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\v | 5i'
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\s12FASCICLE\ VI.11
\v'4P'
.RT
.ce 0
.sp 1P
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\fBRecommendations Q.930 to Q.940\fR \v'2P'
.EF '%	 \ \ \ ^''
.OF ''' \ \ \ ^	%'
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\fBDIGITAL\ SUBSCRIBER\ SIGNALLING\ SYSTEM\ No.\ 1\ (DSS\ 1),\fR 
.ce 0
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\fBNETWORK\ LAYER,\ USER\(hyNETWORK\ MANAGEMENT\fR 
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SECTION\ 1
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\fBNETWORK\ LAYER\fR 
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\fBRecommendation\ Q.930\fR 
.FS
This Recommendation appears in the I\(hyseries of Recommendations as Recommendation 
I.450. 
.FE
.RT
.sp 2P
.sp 1P
.ce 1000
\fBISDN\ USER\(hyNETWORK\ INTERFACE\ LAYER\ 3\ \(em\ GENERAL\ ASPECTS\fR 
.EF '%	Fascicle\ VI.11\ \(em\ Rec.\ Q.930''
.OF '''Fascicle\ VI.11\ \(em\ Rec.\ Q.930	%'
.ce 0
.sp 1P
.LP
\fB1\fR 	\fBGeneral\fR 
.sp 1P
.RT
.sp 2P
.LP
1.1
	\fIIntroduction\fR 
.sp 1P
.RT
.PP
This Recommendation describes in general terms the D\(hychannel
layer\ 3 functions and protocol employed across an ISDN user\(hynetwork 
interface. Details are provided in Recommendation\ Q.931(I.451)\ [1] and 
in 
Recommendation\ Q.932(I.452)\ [2].
.PP
The term \*QLayer 3\*U is a general term used in these Recommendations 
to refer to the procedures described in Recommendation\ Q.931(I.451) and 
in 
Recommendation\ Q.932(I.452).
.PP
The layer 3 protocol provides the means to establish, maintain and
terminate network connections across an ISDN between communicating application 
entities. In addition, it provides generic procedures which may be used 
for the invocation and operation of supplementary services. The detailed 
description of 
.PP
the layer\ 3 protocol in Recommendation\ Q.931(I.451) and
Recommendation\ Q.932(I.452) make use of the definition and terminology
concepts of the ISDN protocol reference model given in
Recommendation\ I.320\ [3]. Recommendation\ Q.931(I.451) and
Recommendation\ Q.932(I.452) do not at present cover all functions which 
may be specified for layer\ 3. Recommendation\ Q.931(I.451), Recommendation\ 
Q.932(I.452) and Recommendation\ I.320 are not presently completely consistent 
in their 
structure of protocols. Further study is required to enhance these
Recommendations in order to resolve these inconsistencies.
.PP
Alignment/interworking between facilities defined in the Q.930\(hyseries 
Recommendations and the services defined in the I.250\(hyseries Recommendations 
is for further study.
.PP
The application of Recommendations Q.931 and Q.932 to the detailed
operation of each individual supplementary service will be the subject 
for the future Recommendations in the Q.930\ series. 
.RT
.PP
1.2
Connection control by the user of an ISDN requires:
.sp 9p
.RT
.LP
	a)
	application of layer 3 protocol for control of
circuit\(hyswitched connections and/or packet\(hyswitched connections,
in combination with;
.LP
	b)
	application of an appropriate data link layer service
(supported by an appropriate physical layer service).
.PP
Layer 3 provides to the user the functions associated with the
establishment and operation of a network connection. Layer\ 3 makes invisible 
to the user how it utilizes underlying resources such as data link connections 
to provide a network connection. 
.bp
.sp 1P
.LP
1.3
	\fIServices provided by the data link layer\fR 
.sp 9p
.RT
.PP
Layer 3 utilizes functions and services provided by the data
link as defined in Recommendations\ Q.920(I.440)\ [4] and Q.921(I.441)
[5]. These services are summarized below:
.RT
.LP
	a)
	establishment of data link connections;
.LP
	b)
	error\(hyprotected transmission of data;
.LP
	c)
	re\(hyestablishment of data link connection (indicating
loss of information).
.sp 1P
.LP
1.4
	\fISymmetry of the layer 3 protocol\fR 
.sp 9p
.RT
.PP
It is intended that the layer 3 protocol is fully symmetrical to
enable direct user\(hyto\(hyuser communication (e.g.,\ PABX\(hyto\(hyPABX 
communication over a leased circuit). 
.PP
In order to achieve this objective, several options are incorporated in 
Recommendation\ Q.931. They are described in Annex\ D to 
Recommendation\ Q.931.
.RT
.sp 2P
.LP
\fB2\fR 	\fBStructure of layer 3\fR 
.sp 1P
.RT
.sp 1P
.LP
2.1
	\fICategories of functions\fR 
.sp 9p
.RT
.PP
There are two categories of functions performed at layer 3 and
services provided by layer\ 3 in the establishment of network connections. 
The first category contains those functions which directly control the 
connection establishment. 
.PP
The second category contains those functions relating to the transport 
of messages additional to the functions provided by the data link layer. 
An 
example of the additional layer\ 3 functions is the provision of re\(hyrouting 
of signalling messages on an alternate 
D\(hychannel
(where provided) in the event of D\(hychannel failure. Other possible functions 
in this category may 
include multiplexing and message segmenting and blocking.
.PP
It is intended that the communications between these two categories
will be aligned as far as possible with the primitives used between the user
parts and the message transfer part in Signalling System No.\ 7.
.PP
Further study is required to determine the functions to be included in 
each category. 
.RT
.sp 1P
.LP
2.2
	\fILayer 3 functions\fR 
.sp 9p
.RT
.PP
The layer 3 protocol described in this Recommendation is designed to effect 
the establishment and control of circuit\(hyswitched and packet\(hyswitched 
connections. The functions support procedures for both basic call and call 
control in conjunction with network\(hyprovided supplementary facilities.
Furthermore, services involving the use of connections of different types,
according to user's specification, may be effected through \*Qmulti\(hymedia\*U 
call control procedures. 
.PP
Functions performed by layer 3 include the following:
.RT
.LP
	a)
	processing of primitives for communicating with the data
link layer;
.LP
	b)
	generation and interpretation of layer 3 messages for
peer\(hylevel communication;
.LP
	c)
	administration of timers and logical entities
(e.g.,\ call\(hyreferences) used in the call control procedures;
.LP
	d)
	 administration of access resources including B\(hychannels and packet\(hylayer 
logical channels 
(e.g.,\ Recommendation\ X.25 [6]);
.LP
	e)
	checking to ensure that services provided are consistent
with user requirements (e.g.,\ as expressed by bearer capability, addresses,
low layer and high layer compatibilities).
.PP
This list of layer 3 functions is not exhaustive, and it is not
intended to imply that all functions are provided on both the terminal 
and the network side of the user\(hynetwork interface. 
.PP
The following general functions may also be performed by
layer\ 3:
.RT
.LP
	a)
	routing and relaying;
.LP
	b)
	network connection control;
.LP
	c)
	conveying user\(hyto\(hynetwork and network\(hyto\(hyuser information;
.LP
	d)
	network connection multiplexing;
.LP
	e)
	segmenting and reassembly;
.bp
.LP
	f
)
	error detection;
.LP
	g)
	error recovery;
.LP
	h)
	sequencing;
.LP
	i)
	congestion control and user data flow control; and
.LP
	j)
	restart.
.sp 1P
.LP
2.2.1
	\fIRouting and relaying\fR 
.sp 9p
.RT
.PP
Network connections exist either between users or between users and ISDN 
exchanges. Network connections may involve intermediate systems which 
provide relays to other interconnecting subnetworks and which facilitate
interworking with other networks. Routing functions determine an appropriate
route between layer\ 3 addresses.
.RT
.sp 1P
.LP
2.2.2
	\fINetwork connection control\fR 
.sp 9p
.RT
.PP
This function includes mechanisms for providing network connections making 
use of data link connections provided by the data link layer. 
.RT
.sp 1P
.LP
2.2.3
	\fIConveying user information\fR 
.sp 9p
.RT
.PP
This function may be carried out with or without the establishment of a 
circuit\(hyswitched connection. 
.RT
.sp 1P
.LP
2.2.4
	\fINetwork connection multiplexing\fR 
.sp 9p
.RT
.PP
Layer 3 provides multiplexing of call control information for
multiple calls onto a single data link connection.
.RT
.sp 1P
.LP
2.2.5
	\fISegmenting and reassembly\fR 
.sp 9p
.RT
.PP
Layer 3 may segment and reassemble Recommendation Q.931 messages
for the purpose of facilitating their transfer across local user\(hynetwork
interface.
.RT
.sp 1P
.LP
2.2.6
	\fIError detection\fR 
.sp 9p
.RT
.PP
Error detection functions are used to check for procedural errors in the 
layer\ 3 protocol. Error detection in layer\ 3 uses, among other 
information, error notification of loss of information from the data link
layer.
.RT
.sp 1P
.LP
2.2.7
	\fIError recovery\fR 
.sp 9p
.RT
.PP
This function includes mechanisms for recovering from detected
errors.
.RT
.sp 1P
.LP
2.2.8
	\fISequencing\fR 
.sp 9p
.RT
.PP
This function includes mechanisms for providing the service of
sequenced delivery of layer\ 3 information over a given network connection 
when requested. In normal conditions layer\ 3 ensures the delivery of information 
in the sequence it is submitted by the user. 
.RT
.sp 1P
.LP
2.2.9
	\fICongestion control and user data flow control\fR 
.sp 9p
.RT
.PP
Layer 3 may indicate rejection or unsuccessful indication for
connection establish requests to control congestion within a network. Flow
control for the user\(hyto\(hyuser signalling messages is described in
Recommendation\ Q.931(I.451).
.RT
.sp 1P
.LP
2.2.10
	\fIRestart\fR 
.sp 9p
.RT
.PP
This function is used to return channels and interfaces to an idle condition 
to recover from certain abnormal conditions. 
.RT
.sp 2P
.LP
\fB3\fR 	\fBStructure of layer 3 Recommendations\fR 
.sp 1P
.RT
.PP
The following is the structure of the layer 3
Recommendations:
.RT
.LP
	Q.930(I.450)\ \(em
	ISDN user\(hynetwork interface layer 3 \(em General
aspects
.LP
	Q.931(I.451)\ \(em
	ISDN user\(hynetwork interface layer 3
specification for basic call control
.LP
	Q.932(I.452)\ \(em
	Generic procedures for the control of ISDN
supplementary services
.bp
.sp 2P
.LP
\fB4\fR 	\fBInterface between layer 3 and the adjacent layers\fR 
.sp 1P
.RT
.sp 1P
.LP
4.1
	\fIOverview of the interfaces\fR 
.sp 9p
.RT
.PP
ISDN user\(hynetwork interface layer 3 provides its services to the
upper layer via layer\ 3 service access point (SAP), and receives services 
from the data link layer via data link layer SAP, as is shown in Figure\ 
1/Q.930. A particular service is provided to the upper layer, or received 
from the data 
link layer, by exchanging a corresponding sequence of primitives across the
SAP.
.RT
.sp 1P
.LP
4.2
	\fIInterface between layer 3 and data link layer\fR 
.sp 9p
.RT
.PP
Overview of the interface between ISDN user\(hynetwork interface
layer\ 3 and the data link layer from the view point of the data link layer 
is given in \(sc\ 2 of Recommendation\ Q.920(I.440). Primitives and primitive 
procedures for this interface are specified in \(sc\ 4 of
Recommendation\ Q.921(I.441).
.RT
.sp 1P
.LP
4.3
	\fIInterface between layer 3 and upper layer\fR 
.sp 9p
.RT
.PP
Primitives and primitive procedures for this interface are left for further 
study. 
.RT
.LP
.rs
.sp 18P
.ad r
\fBFigure 1/Q.930, p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
	\fBReferences\fR 
.sp 1P
.RT
.LP
[1]
	CCITT Recommendation \fIISDN user\(hynetwork interface layer 3\fR 
\fIspecification for basic call control\fR , Vol,\ VI(III), Rec.\ Q.931(I.451).
.LP
[2]
	CCITT Recommendation \fIGeneric procedures for the control of ISDN\fR 
\fIsupplementary services\fR , Vol.\ VI(III), Rec.\ Q.932(I.452).
.LP
[3]
	CCITT Recommendation \fIISDN protocol reference model\fR , Vol.\ III,
Rec.\ I.320.
.LP
[4]
	CCITT Recommendation \fIISDN user\(hynetwork interface data\fR 
\fIlink layer \(em General aspects\fR , Vol.\ VI(III), Rec.\ Q.920(I.440).
.LP
[5]
	CCITT Recommendation \fIISDN user\(hynetwork interface data\fR 
\fIlink layer specification\fR , Vol.\ VI(III), Rec.\ Q.921(I.441).
.LP
[6]
	CCITT Recommendation \fIInterface between data terminal equipment\fR 
\fI(DTE) and data circuit terminating equipment (DCE) for terminals\fR 
\fIoperating in the packet mode and connected to public data networks by\fR 
\fIdedicated circuit\fR , Vol.\ VIII, Rec.\ X.25.
.sp 2P
.LP
	\fIAbbreviations used in Recommendations Q.930(I.450) and Q.931(I.451)\fR 
.sp 1P
.RT
.PP
See list at the end of Recommendation Q.931.
.bp
.RT
.sp 2P
.LP
\fBRecommendation\ Q.931\fR 
.RT
.sp 2P
.ce 1000
\fBISDN\ USER\(hyNETWORK\ INTERFACE\ LAYER\ 3\ SPECIFICATION\fR 
.EF '%	Fascicle\ VI.8\ \(em\ Rec.\ Q.931''
.OF '''Fascicle\ VI.8\ \(em\ Rec.\ Q.931	%'
.ce 0
.sp 1P
.ce 1000
\fBFOR\ BASIC\ CALL\ CONTROL\fR 
.ce 0
.sp 1P
.LP
\fB1\fR 	\fBGeneral\fR 
.sp 1P
.RT
.PP
This Recommendation specifies the procedures for the establishing, maintaining, 
and clearing of network connections at the ISDN user\(hynetwork 
interface. These procedures are defined in terms of messages exchanged 
over the D\(hychannel of basic and primary rate interface structures. The 
functions and 
procedures of this protocol, and the relationship with other layers, are
described in general terms in Recommendation\ Q.930 (I.450)\ [1].
.PP
This Recommendation is intended to specify the essential features,
procedures, and messages required for call control in the D\(hychannel. 
However, there are some details of procedure which have not yet been specified, 
and 
which will be the subject of further study.
.RT
.sp 1P
.LP
1.1
	\fIScope of the Recommendation\fR 
.sp 9p
.RT
.PP
The procedures currently described in this Recommendation are for the control 
of circuit\(hyswitched connections, user\(hyto\(hyuser signalling 
connections, and packet\(hyswitched connections. The transport of other
message\(hybased information flows on the D\(hychannel is a subject for 
further study and will be included in related Recommendations. 
.PP
\fINote\ 1\fR \ \(em\ The term \*Qlayer\ 3\*U is used for the functions 
and protocol described in this Recommendation [see Recommendation\ Q.930 
(I.450)]. The 
terms \*Qdata link layer\*U and \*Qlayer\ 2\*U are used interchangeably 
to refer to the layer immediately below layer\ 3. 
.PP
\fINote\ 2\fR \ \(em\ Alignment of the functions and protocol with those 
of OSI network layer is for further study. 
.RT
.sp 1P
.LP
1.2
	\fIApplication to interface structures\fR 
.sp 9p
.RT
.PP
The layer 3 procedures apply to the interface structures defined in Recommendation\ 
I.412\ [2]. They use the functions and services provided by 
layer\ 2. The unacknowledged information transfer service is used by layer\ 
3 to provide point\(hyto\(hymultipoint operation as described in \(sc\ 
5.2. 
.PP
The layer 3 procedures request the services of layer 2 and receive
information from layer\ 2 using the primitives defined in
Recommendation\ Q.921\ [3]. These primitives are used to illustrate the
communication between the protocol layers and are not intended to specify or
constrain implementations.
.RT
.sp 2P
.LP
\fB2\fR 	\fBOverview of\fR 
\fBcall control\fR 
.sp 1P
.RT
.PP
In this Recommendation the terms \*Qincoming\*U and \*Qoutgoing\*U are 
used to describe the call as viewed by the user side of the interface. 
.PP
In the paragraphs which follow states are defined for circuit switched 
calls in \(sc\ 2.1 (call states), for packet mode access connections in 
\(sc\ 2.2 
(access connection states) for temporary signalling connections in \(sc\ 
2.3 (call states), and for the interface in \(sc\ 2.4 (global call reference 
states). 
.PP
This paragraph defines the basic call control states that individual calls 
may have. These definitions do not apply to the state of the interface 
itself, any attached equipment, the D\(hychannel, or the logical links used for
signalling on the D\(hychannel. Because several calls may exist simultaneously 
at a user\(hynetwork interface, and each call may be in a different state, 
the state of the interface itself cannot be unambiguously defined. 
.PP
\fINote\fR \ \(em\ Additional states and SDL diagrams may be defined when new
procedures are developed.
.PP
Detailed description of the procedures for call control are given in \(sc\(sc\ 
5, 6, 7, and\ 8 in terms of: (a)\ the messages defined in \(sc\ 3 which 
are 
transferred across the user\(hynetwork interface; and (b)\ the information
processing and actions that take place at the userside and the network side.
Overview and detailed\ SDL diagrams for call control of circuit\(hyswitched 
calls are contained in Annex\ A. 
.bp
.PP
Throughout this Recommendation, references are made to B\(hychannels. For 
services using H\(hychannels, the references to B\(hychannels should be 
taken to 
refer to the appropriate H\(hychannel. Further study may be needed on other
enhancements to support such services.
.RT
.sp 1P
.LP
2.1
	\fICircuit switched calls\fR 
.sp 9p
.RT
.PP
This paragraph defines the basic call control states for circuit
switched calls. The procedures for call control are given in \(sc\ 5.
.PP
Annex D contains optional procedures (as an extension to the basic
procedures) to allow symmetric signalling. These states are defined in
Annex\ D.
.RT
.sp 1P
.LP
2.1.1
	\fICall states at the user side of the interface\fR 
.sp 9p
.RT
.PP
The states which may exist on the user side of the user\(hynetwork
interface are defined in this paragraph.
.RT
.sp 1P
.LP
2.1.1.1
	\fINull state (U0)\fR 
.sp 9p
.RT
.PP
No call exists.
.RT
.sp 1P
.LP
2.1.1.2
	\fICall initiated (U1)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call, when the user requests call establishment 
from the network. 
.RT
.sp 1P
.LP
2.1.1.3
	\fIOverlap sending (U2)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the user has received acknowledgement 
of the call establishment request which permits the user to 
send additional call information to the network in overlap mode.
.RT
.sp 1P
.LP
2.1.1.4
	\fIOutgoing call proceeding (U3)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the user has received acknowledgement 
that the network has received all call information necessary to effect 
call establishment. 
.RT
.sp 1P
.LP
2.1.1.5
	\fICall delivered (U4)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call, when the calling user has received 
an indication that remote user alerting has been initiated. 
.RT
.sp 1P
.LP
2.1.1.6
	\fICall present (U6)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has received a call 
establishment request but has not yet responded. 
.RT
.sp 1P
.LP
2.1.1.7
	\fICall received (U7)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has indicated alerting 
but has not yet answered. 
.RT
.sp 1P
.LP
2.1.1.8
	\fIConnect request (U8)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has answered the call 
and is waiting to be awarded the call. 
.RT
.sp 1P
.LP
2.1.1.9
	\fIIncoming call proceeding (U9)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has sent
acknowledgement that the user has received all call information necessary to
effect call establishment.
.bp
.RT
.sp 1P
.LP
2.1.1.10
	\ \fIActive (U10)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has received an acknowledgement 
from the network that the user has been awarded the call. 
This state exists for an outgoing call when the user has received an indication 
that the remote user has answered the call. 
.RT
.sp 1P
.LP
2.1.1.11
	\ \fIDisconnect request (U11)\fR 
.sp 9p
.RT
.PP
This state exists when the user has requested the network to clear the 
end\(hyto\(hyend connection (if any) and is waiting for a reponse. 
.RT
.sp 1P
.LP
2.1.1.12
	\ \fIDisconnect indication (U12)\fR 
.sp 9p
.RT
.PP
This state exists when the user has received an invitation to
disconnect because the network has disconnected the end\(hyto\(hyend connection 
(if any). 
.RT
.sp 1P
.LP
2.1.1.13
	\ \fISuspend request (U15)\fR 
.sp 9p
.RT
.PP
This state exists when the user has requested the network to
suspend the call and is waiting for a response.
.RT
.sp 1P
.LP
2.1.1.14
	\ \fIResume request (U17)\fR 
.sp 9p
.RT
.PP
This state exists when the user has requested the network to resume a previously 
suspended call and is waiting for a response. 
.RT
.sp 1P
.LP
2.1.1.15
	\ \fIRelease request (U19)\fR 
.sp 9p
.RT
.PP
This state exists when the user has requested the network to
release and is waiting for a response.
.RT
.sp 1P
.LP
2.1.1.16
	\ \fIOverlap receiving (U25)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has
acknowledged the call establishment request from the network and is prepared 
to receive additional call information (if any) in overlap mode. 
.RT
.sp 1P
.LP
2.1.2
	\fINetwork call states\fR 
.sp 9p
.RT
.PP
The call states that may exist on the network side of the
user\(hynetwork interface are defined in this paragraph.
.RT
.sp 1P
.LP
2.1.2.1
	\fINull state (N0)\fR 
.sp 9p
.RT
.PP
No call exists.
.RT
.sp 1P
.LP
2.1.2.2
	\fICall initiated (N1)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the network has
received a call establishment request but has not yet responded.
.RT
.sp 1P
.LP
2.1.2.3
	\fIOverlap sending (N2)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the network has
acknowledged the call establishment request and is prepared to receive
additional call information (if any) in overlap mode.
.RT
.sp 1P
.LP
2.1.2.4
	\fIOutgoing call proceeding (N3)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the network has sent
acknowledgement that the network has received all call information necessary 
to effect call establishment. 
.RT
.sp 1P
.LP
2.1.2.5
	\fICall delivered (N4)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the network has
indicated that remote user alerting has been initiated.
.bp
.RT
.sp 1P
.LP
2.1.2.6
	\fICall present (N6)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has sent a call 
establishment request but has not yet received a satisfactory 
response.
.RT
.sp 1P
.LP
2.1.2.7
	\fICall received (N7)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has
received an indication that the user is alerting but has not yet received an
answer.
.RT
.sp 1P
.LP
2.1.2.8
	\fIConnect request (N8)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has
received an answer but the network has not yet awarded the call.
.RT
.sp 1P
.LP
2.1.2.9
	\fIIncoming call proceeding (N9)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has
received acknowledgement that the user has received all call information
necessary to effect call establishment.
.RT
.sp 1P
.LP
2.1.2.10
	\ \fIActive (N10)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has awarded the 
call to the called user. This state exists for an outgoing call when the 
network has indicated that the remote user has answered the call.
.RT
.sp 1P
.LP
2.1.2.11
	\ \fIDisconnect request (N11)\fR 
.sp 9p
.RT
.PP
This state exists when the network has received a request from the user 
to clear the end\(hyto\(hyend connection (if any). 
.RT
.sp 1P
.LP
2.1.2.12
	\ \fIDisconnect indication (N12)\fR 
.sp 9p
.RT
.PP
This state exists when the network has disconnected the end\(hyto\(hyend 
connection (if any) and has sent an invitation to disconnect the user\(hynetwork 
connection. 
.RT
.sp 1P
.LP
2.1.2.13
	\ \fISuspend request (N15)\fR 
.sp 9p
.RT
.PP
This state exists when the network has received a request to
suspend the call but has not yet responded.
.RT
.sp 1P
.LP
2.1.2.14
	\ \fIResume request (N17)\fR 
.sp 9p
.RT
.PP
This state exists when the network has received a request to resume a previously 
suspended call but has not yet responded. 
.RT
.sp 1P
.LP
2.1.2.15
	\ \fIRelease request (N19)\fR 
.sp 9p
.RT
.PP
This state exists when the network has requested the user to
release and is waiting for a response.
.RT
.sp 1P
.LP
2.1.2.16
	\ \fICall abort (N22)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call for the point\(hyto\(hymultipoint 
configuration when the call is being cleared before any user has been awarded 
the call. 
.RT
.sp 1P
.LP
2.1.2.17
	\ \fIOverlap receiving (N25)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has
received acknowledgement of the call establishment request which permits the
network to send additional call information (if any) in the overlap
mode.
.RT
.sp 1P
.LP
2.2
	\fIPacket\(hymode access connections\fR 
.sp 9p
.RT
.PP
This paragraph defines the basic packet\(hymode access connection
control states for access to the ISDN virtual circuit bearer service (case\ 
B). The procedures for access connection control are given in \(sc\ 6. 
.bp
.RT
.sp 1P
.LP
2.2.1
	\fIAccess connection states at the user side of the interface\fR 
.sp 9p
.RT
.PP
The states which may exist on the user side of the user\(hynetwork
interface are defined in this paragraph.
.RT
.sp 1P
.LP
2.2.1.1
	\fINull state (U0)\fR 
.sp 9p
.RT
.PP
No access connection exists.
.RT
.sp 1P
.LP
2.2.1.2
	\fICall initiated (U1)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing access connection, when the user requests 
access connection establishment from the network. 
.RT
.sp 1P
.LP
2.2.1.3
	\fIOutgoing call proceeding (U3)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing access connection when the user has received 
acknowledgement that the network has received all access 
connection information necessary to effect access connection
establishment.
.RT
.sp 1P
.LP
2.2.1.4
	\fICall present (U6)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection when the user has received 
a access connection establishment request but has not yet 
responded.
.RT
.sp 1P
.LP
2.2.1.5
	\fICall received (U7)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection when the user has indicated 
alerting but has not yet answered. 
.RT
.sp 1P
.LP
2.2.1.6
	\fIConnect request (U8)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection when the user has accepted 
the access connection and is waiting to be awarded the access 
connection.
.RT
.sp 1P
.LP
2.2.1.7
	\fIIncoming call proceeding (U9)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection when the user has sent 
acknowledgement that the user has received all access connection 
information necessary to effect access connection establishment.
.RT
.sp 1P
.LP
2.2.1.8
	\fIActive (U10)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection when the user has received 
an acknowledgement from the network that the user has been awarded the 
access connection. This state exists for an outgoing access connection 
when the user has received an indication that the local network has completed 
the access connection. 
.RT
.sp 1P
.LP
2.2.1.9
	\fIDisconnect request (U11)\fR 
.sp 9p
.RT
.PP
This state exists when the user has requested the local network to clear 
the access connection and is waiting for a response. 
.RT
.sp 1P
.LP
2.2.1.10
	\ \fIDisconnect indication (U12)\fR 
.sp 9p
.RT
.PP
This state exists when the user has received an invitation to
disconnect because the network has disconnected the access connection to\(hyend
connection (if any).
.RT
.sp 1P
.LP
2.2.1.11
	\ \fIRelease request (U19)\fR 
.sp 9p
.RT
.PP
This state exists when the user has requested the network to
release the access connection and is waiting for a response.
.RT
.sp 1P
.LP
2.2.2
	\fIAccess connection states at the network side of the interface\fR 
.sp 9p
.RT
.PP
The states which may exist on the network side of the user\(hynetwork interface 
are defined in this paragraph. 
.RT
.sp 1P
.LP
2.2.2.1
	\fINull state (N0)\fR 
.sp 9p
.RT
.PP
No access connection exists.
.bp
.RT
.sp 1P
.LP
2.2.2.2
	\fICall initiated (N1)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing access connection when the
network has received an access connection establishment request but has 
not yet responded. 
.RT
.sp 1P
.LP
2.2.2.3
	\fIOutgoing call proceeding (N3)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing access connection when the
network has sent acknowledgement that the network has received all access
connection information necessary to effect access connection
establishment.
.RT
.sp 1P
.LP
2.2.2.4
	\fICall present (N6)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection when the
network has sent an access connection establishment request but has not yet
received a satisfactory response.
.RT
.sp 1P
.LP
2.2.2.5
	\fICall received (N7)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection when the
network has received an indication that the user is alerting but has not yet
received an answer.
.RT
.sp 1P
.LP
2.2.2.6
	\fIConnect request (N8)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection when the
network has received an answer but the network has not yet awarded the 
access connection. 
.RT
.sp 1P
.LP
2.2.2.7
	\fIIncoming call proceeding (N9)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection when the
network has received acknowledgment that the user has received all access
connection information necessary to effect access connection
establishment.
.RT
.sp 1P
.LP
2.2.2.8
	\fIActive (N10)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection when the
network has awarded the access connection to the called user. This state 
exists for an outgoing access connection when the local network has indicated 
that the access connection has been completed. 
.RT
.sp 1P
.LP
2.2.2.9
	\fIDisconnect request (N11)\fR 
.sp 9p
.RT
.PP
This state exists when the network has received a request from the user 
to clear the access connection. 
.RT
.sp 1P
.LP
2.2.2.10
	\ \fIDisconnect indication (N12)\fR 
.sp 9p
.RT
.PP
This state exists when the network has sent an invitation to
disconnect the user\(hynetwork access connection.
.RT
.sp 1P
.LP
2.2.2.11
	\ \fIRelease request (N19)\fR 
.sp 9p
.RT
.PP
This state exists when the network has requested the user to
release the access connection and is waiting for a response.
.RT
.sp 1P
.LP
2.2.2.12
	\ \fICall abort (N22)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming access connection for the
point\(hyto\(hymultipoint configuration when the access connection is being 
cleared before any user has been awarded the access connection. 
.RT
.sp 1P
.LP
2.3
	\fITemporary signalling connections\fR 
.sp 9p
.RT
.PP
This paragraph defines the basic call control states for
user\(hyto\(hyuser signalling not associated with circuit switched calls. The
procedures for call control are given in \(sc\ 7.2.
.RT
.sp 1P
.LP
2.3.1
	\fICall states at the user side of the interface\fR 
.sp 9p
.RT
.PP
The states which may exist on the user side of the user\(hynetwork
interface are defined in this paragraph.
.bp
.RT
.sp 1P
.LP
2.3.1.1
	\fINull state (U0)\fR 
.sp 9p
.RT
.PP
No call exists.
.RT
.sp 1P
.LP
2.3.1.2
	\fICall initiated (U1)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call, when the user requests call establishment 
from the network. 
.RT
.sp 1P
.LP
2.3.1.3
	\fIOverlap sending (U2)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the user has received acknowledgement 
of the call establishment request which permits the user to 
send additional call information to the network in overlap mode.
.RT
.sp 1P
.LP
2.3.1.4
	\fIOutgoing call proceeding (U3)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the user has received acknowledgement 
that the network has received all call information necessary 
to effect call establishment.
.RT
.sp 1P
.LP
2.3.1.5
	\fICall delivered (U4)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call, when the calling user has received 
an indication that remote user alerting has been initiated. 
.RT
.sp 1P
.LP
2.3.1.6
	\fICall present (U6)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has received a call 
establishment request but has not yet responded. 
.RT
.sp 1P
.LP
2.3.1.7
	\fICall received (U7)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has indicated alerting 
but has not yet answered. 
.RT
.sp 1P
.LP
2.3.1.8
	\fIConnect request (U8)\fR 
.sp 9p
.RT
.PP
This state exists for incoming call when the user has answered the call 
and is awaiting to be awarded the call. 
.RT
.sp 1P
.LP
2.3.1.9
	\fIIncoming call proceeding (U9)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has sent
acknowledgement that the user has received all call information necessary to
effect call establishment.
.RT
.sp 1P
.LP
2.3.1.10
	\ \fIActive (U10)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has received an acknowledgement 
from the network that the user has been awarded the call. 
This state exists for an outgoing call when the user has received an
indication that the remote user has answered the call.
.RT
.sp 1P
.LP
2.3.1.11
	\ \fIRelease request (U19)\fR 
.sp 9p
.RT
.PP
This state exists when the user has requested the network to
release and is waiting for a response.
.RT
.sp 1P
.LP
2.3.1.12
	\ \fIOverlap receiving (U25)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the user has
acknowledged the call establishment request from the network and is prepared 
to receive additional call information (if any) in overlap mode. 
.RT
.sp 1P
.LP
2.3.2
	\fINetwork call states\fR 
.sp 9p
.RT
.PP
The call states that may exist on the network side of the
user\(hynetwork interface are defined in this paragraph.
.bp
.RT
.sp 1P
.LP
2.3.2.1
	\fINull state (N0)\fR 
.sp 9p
.RT
.PP
No call exists.
.RT
.sp 1P
.LP
2.3.2.2
	\fICall initiated (N1)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the network has
received a call establishment request but has not yet responded.
.RT
.sp 1P
.LP
2.3.2.3
	\fIOverlap sending (N2)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the network has
acknowledged the call establishment request and is prepared to receive
additional call information (if any) in overlap mode.
.RT
.sp 1P
.LP
2.3.2.4
	\fIOutgoing call proceeding (N3)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the network has sent
acknowledgement that the network has received all call information necessary 
to effect call establishment. 
.RT
.sp 1P
.LP
2.3.2.5
	\fICall delivered (N4)\fR 
.sp 9p
.RT
.PP
This state exists for an outgoing call when the network has
indicated that remote user alerting has been initiated.
.RT
.sp 1P
.LP
2.3.2.6
	\fICall present (N6)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has sent a call 
establishment request but has not yet received a satisfactory 
response.
.RT
.sp 1P
.LP
2.3.2.7
	\fICall received (N7)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has
received an indication that the user is alerting but has not yet received an
answer.
.RT
.sp 1P
.LP
2.3.2.8
	\fIConnect request (N8)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has
received an answer but the network has not yet awarded the call.
.RT
.sp 1P
.LP
2.3.2.9
	\fIIncoming call proceeding (N9)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has
received acknowledgement that the user has received all call information
necessary to effect call establishment.
.RT
.sp 1P
.LP
2.3.2.10
	\ \fIActive (N10)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has awarded the 
call to the called user. This state exists for an outgoing call when the 
network has indicated that the remote user has answered the call.
.RT
.sp 1P
.LP
2.3.2.11
	\ \fIRelease request (N19)\fR 
.sp 9p
.RT
.PP
This state exists when the network has requested the user to
release and is waiting for a response.
.RT
.sp 1P
.LP
2.3.2.12
	\ \fICall abort (N22)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call for the point\(hyto\(hymultipoint 
configuration when the call is being cleared before any user has been awarded 
the call. 
.RT
.sp 1P
.LP
2.3.2.13
	\ \fIOverlap receiving (N25)\fR 
.sp 9p
.RT
.PP
This state exists for an incoming call when the network has
received acknowledgement of the call establishment request which permits the
network to send additional call information (if any) in the overlap mode.
.bp
.RT
.sp 1P
.LP
2.4
	\fIStates associated with the global call reference\fR 
.sp 9p
.RT
.PP
This paragraph defines the states that the protocol may adopt using the 
global call reference. The procedures for use of the global call reference 
for RESTART are contained in \(sc\ 5.5. 
.PP
There is only one global call reference per interface.
.RT
.sp 1P
.LP
2.4.1
	\fICall states at the user side of the interface\fR 
.sp 9p
.RT
.PP
The states which may exist on the user side of the user network
interface are defined in this paragraph.
.RT
.sp 1P
.LP
2.4.1.1
	\fINull (Rest 0)\fR 
.sp 9p
.RT
.PP
No transaction exists.
.RT
.sp 1P
.LP
2.4.1.2
	\fIRestart request (Rest 1)\fR 
.sp 9p
.RT
.PP
This state exists for a restart transaction when the user has sent a restart 
request but has not yet received an acknowledgement response from the network. 
.RT
.sp 1P
.LP
2.4.1.3
	\fIRestart (Rest 2)\fR 
.sp 9p
.RT
.PP
This state exists when a request for a restart has been received
from the network and responses have not yet been received from all locally
active call references.
.RT
.sp 1P
.LP
2.4.2
	\fICall states at the network side of the interface\fR 
.sp 9p
.RT
.PP
The states which may exist on the network side of the user\(hynetwork interface 
are defined in this paragraph. 
.RT
.sp 1P
.LP
2.4.2.1
	\fINull (Rest 0)\fR 
.sp 9p
.RT
.PP
No transaction exists.
.RT
.sp 1P
.LP
2.4.2.2
	\fIRestart request (Rest 1)\fR 
.sp 9p
.RT
.PP
This state exists for a restart transaction when the network has
sent a restart request but has not yet received an acknowledgement response
from the user.
.RT
.sp 1P
.LP
2.4.2.3
	\fIRestart (Rest 2)\fR 
.sp 9p
.RT
.PP
This state exists when a request for a restart has been received
from the user and a response has not yet been received from all locally 
active call references. 
.RT
.sp 2P
.LP
\fB3\fR 	\fBMessage functional definitions and content\fR 
.sp 1P
.RT
.PP
This paragraph provides an overview of the Q.931 message structure, which 
highlights the functional definition and information content 
(i.e.\ semantics) of each message. Each definition includes:
.RT
.LP
	a)
	A brief description of the message direction and use,
including whether the message has:
.LP
	1)
	 Local significance, i.e. relevant only in the originating or terminating 
access; 
.LP
	2)
	Access significance, i.e. relevant in the originating and
terminating access, but not in the network;
.LP
	3)
	 Dual significance, i.e. relevant in either the originating or terminating 
access and in the network; or 
.LP
	4)
	Global significance, i.e. relevant in the originating and
terminating access and in the network.
.LP
	b)
	A table listing the codeset 0 information elements in the
order of their appearance in the message (same relative order for all message 
types). For each information element the table indicates: 
.LP
	1)
	the section of this Recommendation describing the
information element;
.LP
	2)
	 the direction in which it may be sent; i.e., user to network (`u\ \(ra\ 
n'), network to user (`n\ \(ra\ u'), or both; 
.bp
.LP
	 \fINote\fR \ \(em\ The user\(hynetwork terminology in \(sc 3 refers to 
the TE\(hyTE, TE\(hyNT2, and NT2\(hyET interface structures. Annex\ D contains 
a description of the information element usage for
symmetric NT2\(hyNT2 interfaces.
.LP
	3)
	 whether inclusion is mandatory (`M') or optional (`O'), with a reference 
to notes explaining the circumstances under 
which the information element shall be included;
.LP
	4)
	 the length of the information element (or permissible range of lengths), 
in octets, where `*' denotes an undefined maximum length, which 
may be network or service dependant.
.LP
	\fINote\fR \ \(em\ All messages may contain information elements from
codesets\ 5, 6 and\ 7 and corresponding locking and non\(hylocking
shift information elements which comply with the coding rules
specified in \(sc\(sc\ 4.5.2\(hy4.5.4. None of these information elements,
however, are listed in any of the tables in \(sc\ 3.
.LP
	c)
	Further explanatory notes, as necessary.
.sp 1P
.LP
3.1
	\fIMessages for circuit mode connection control\fR 
.sp 9p
.RT
.PP
Table 3\(hy1/Q.931 summarizes the messages for circuit\(hymode connection 
control. 
.RT
.LP
.sp 2
.ce
\fBH.T. [T1.931]\fR 
.ce
TABLE\ 3\(hy1/Q.931
.ce
\fBMessages for circuit\(hymode connection control\fR 
.T&
lw(126p) | lw(42p) .
	
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy1/Q.931 [T1.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.1
	\fIAlerting\fR 
.sp 9p
.RT
.PP
This message is sent by the called user to the network and by the network 
to the calling user to indicate that called user alerting has been 
initiated. See Table\ 3\(hy2/Q.931.
.RT
.ce
\fBH.T. [T2.931]\fR 
.ce
TABLE\ 3\(hy2/Q.931
.ce
\fBALERTING message content\fR 
.ce
Message type:\ ALERTING
.ce
Significance:\ global
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy2/Q.931 [T2.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.2
	\fICall proceeding\fR 
.sp 9p
.RT
.PP
This message is sent by the called user to the network or by the
network to the calling user to indicate that the requested call establishment 
has been initiated and no more call establishment information will be accepted. 
See Table\ 3\(hy3/Q.931. 
.RT
.ce
\fBH.T. [T3.931]\fR 
.ce
TABLE\ 3\(hy3/Q.931
.ce
\fBCALL PROCEEDING message content\fR 
.ce
Message type:\ CALL\ PROCEEDING
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy3/Q.931 [T3.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 16P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.3
	\fICongestion control\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to indicate the
establishment or termination of flow control on the transmission of USER
INFORMATION messages. See Table\ 3\(hy4/Q.931.
.RT
.ce
\fBH.T. [T4.931]\fR 
.ce
TABLE\ 3\(hy4/Q.931
.ce
\fBCONGESTION CONTROL message content\fR 
.ce
Message type:\ CONGESTION CONTROL
.ce
Significance:\ local (Note 1)
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy4/Q.931 [T4.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.4
	\fIConnect\fR 
.sp 9p
.RT
.PP
This message is sent by the called user to the network and by the network 
to the calling user to indicate call acceptance by the called user. See 
Table\ 3\(hy5/Q.931. 
.RT
.ce
\fBH.T. [T5.931]\fR 
.ce
TABLE\ 3\(hy5/Q.931
.ce
\fBCONNECT message content\fR 
.ce
Message type:\ CONNECT
.ce
Significance:\ global
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy5/Q.931 [T5.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.5
	\fIConnect acknowledge\fR 
.sp 9p
.RT
.PP
This message is sent by the network to the called user to indicate the 
user has been awarded the call. It may also be sent by the calling user 
to the network to allow symmetrical call control procedures. See 
Table\ 3\(hy6/Q.931.
.RT
.ce
\fBH.T. [T6.931]\fR 
.ce
TABLE\ 3\(hy6/Q.931
.ce
\fBCONNECT ACKNOWLEDGE message content\fR 
.ce
Message type:\ CONNECT ACKNOWLEDGE
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy6/Q.931 [T6.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.6
	\fIDisconnect\fR 
.sp 9p
.RT
.PP
This message is sent by the user to request the network to clear an end\(hyto\(hyend 
connection or is sent by the network to indicate that the end\(hyto\(hyend 
connection is cleared. See Table\ 3\(hy7/Q.931. 
.RT
.ce
\fR 
.ce
\fBH.T. [T7.931]\fR 
.ce
TABLE\ 3\(hy7/Q.931
.ce
\fBDISCONNECT message content\fR 
.ce
Message type:\ DISCONNECT
.ce
Significance:\ global
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy7/Q.931 [T7.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 3P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.7
	\fIFacility\fR 
.sp 9p
.RT
.PP
This message is defined in Recommendation Q.932\ [4].
.RT
.sp 1P
.LP
3.1.8
	\fIInformation\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to provide
additional information. It may be used to provide information for call
establishment (e.g.\ overlap sending and receiving) or miscellaneous
call\(hyrelated information. See Table\ 3\(hy8/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T8.931]\fR 
.ce
TABLE\ 3\(hy8/Q.931
.ce
\fBINFORMATION message content\fR 
.ce
Message type:\ INFORMATION
.ce
Significance:\ local (Note 1)
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy8/Q.931 [T8.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.9
	\fINotify\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to indicate
information pertaining to a call, such as user suspended. See
Table\ 3\(hy9/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T9.931]\fR 
.ce
TABLE\ 3\(hy9/Q.931
.ce
\fBNOTIFY message content\fR 
.ce
Message type:\ NOTIFY
.ce
Significance:\ access
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy9/Q.931 [T9.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 19P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.10
	\fIProgress\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to indicate the
progress of a call in the event of interworking or in relation with the
provision of in\(hyband information/patterns. See Table\ 3\(hy10/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T10.931]\fR 
.ce
TABLE\ 3\(hy10/Q.931
.ce
\fBPROGRESS message content\fR 
.ce
Message type:\ PROGRESS
.ce
Significance:\ global
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy10/Q.931 [T10.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 13P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.11
	\fIRelease\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to indicate that
the equipment sending the message has disconnected the channel (if any) and
intends to release the channel and the call reference, and that the receiving 
equipment should release the channel and prepare to release the call reference 
after sending RELEASE COMPLETE. See Table\ 3\(hy11/Q.931. 
.RT
.ce
\fR 
.ce
\fBH.T. [T11.931]\fR 
.ce
TABLE\ 3\(hy11/Q.931
.ce
\fBRELEASE message content\fR 
.ce
Message type:\ RELEASE
.ce
Significance:\ local (Note 1)
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy11/Q.931 [T11.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 4P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.12
	\fIRelease complete\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to indicate that
the equipment sending the message has released the channel (if any) and call
reference, the channel is available for reuse, and the receiving equipment
shall release the call reference. See Table\ 3\(hy12/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T12.931]\fR 
.ce
TABLE\ 3\(hy12/Q.931
.ce
\fBRELEASE COMPLETE message content\fR 
.ce
Message type:\ RELEASE COMPLETE
.ce
Significance:\ local (Note 1)
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy12/Q.931 [T12.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 4P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.13
	\fIResume\fR 
.sp 9p
.RT
.PP
This message is sent by the user to request the network to resume a suspended 
call. See Table\ 3\(hy13/Q.931. 
.RT
.ce
\fR 
.ce
\fBH.T. [T13.931]\fR 
.ce
TABLE\ 3\(hy13/Q.931
.ce
\fBRESUME message content\fR 
.ce
Message type:\ RESUME
.ce
Significance:\ local
.ce
Direction:\ user to network
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy13/Q.931 [T13.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.1.14
	\fIResume acknowledge\fR 
.sp 9p
.RT
.PP
This message is sent by the network to the user to indicate
completion of a request to resume a suspended call. See Table\ 3\(hy14/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T14.931]\fR 
.ce
TABLE\ 3\(hy14/Q.931
.ce
\fBRESUME ACKNOWLEDGE message content\fR 
.ce
Message type:\ RESUME ACKNOWLEDGE
.ce
Significance:\ local
.ce
Direction:\ network to user
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy14/Q.931 [T14.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.15
	\fIResume reject\fR 
.sp 9p
.RT
.PP
This message is sent by the network to the user to indicate failure of 
a request to resume a suspended call. See Table\ 3\(hy15/Q.931. 
.RT
.ce
\fBH.T. [T15.931]\fR 
.ce
TABLE\ 3\(hy15/Q.931
.ce
\fBRESUME REJECT message content\fR 
.ce
Message type:\ RESUME REJECT
.ce
Significance:\ local
.ce
Direction:\ network to user
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy15/Q.931 [T15.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 23P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.16
	\fISetup\fR 
.sp 9p
.RT
.PP
This message is sent by the calling user to the network and by the network 
to the called user to initiate call establishment. See 
Table\ 3\(hy16/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [1T16.931]\fR 
.ce
TABLE\ 3\(hy16/Q.931
.ce
\fBSETUP message content\fR 
.ce
Message type:\ SETUP
.ce
Significance:\ global
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy16/Q.931 [1T16.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fR 
.ce
\fBH.T. [2T16.931]\fR 
.LP
\fINote\ 1\fR 
\ \(em\ Included if the user or the network optionally indicates that all
information necessary for call establishment is included in the SETUP message.
.LP
\fINote\ 2\fR 
\ \(em\ The Repeat indicator information element is included immediately
before the first Bearer capability information element when either the 
in\(hycall modification procedure or the bearer capability negotiation 
procedure is used (see Annex O). 
.LP
\fINote\ 3\fR 
\ \(em\ May be repeated if the bearer capability negotiation procedure
is used. For bearer capability negotiation, either two or
three Bearer capability information elements may be included in descending
order of priority, i.e., highest priority first.
.LP
\fINote\ 4\fR 
\ \(em\ Mandatory in the network\(hyto\(hyuser direction. Included in the
user\(hyto\(hynetwork direction when the user wants to indicate a channel. 
If not 
included, its absence is interpreted as \*Qany channel acceptable\*U.
.LP
\fINote\ 5\fR 
\ \(em\ May be included for functional operation of supplementary
services (see \(sc\ 7).
.LP
\fINote\ 6\fR 
\ \(em\ Included in the event of interworking or in connection with the
provision of in\(hyband information/patterns.
.LP
\fINote\ 7\fR 
.LP
\ \(em\ Included by the calling user or the network to indicate
network\(hyspecific facilities information (see Annex\ E).
.LP
\fINote\ 8\fR 
\ \(em\ Included if the network provides information that can be
presented to the user.
.LP
\fINote\ 9\fR 
\ \(em\ The minimum length is 2 octets;
the maximum length is network dependent and is either 34 or 82 octets.
.LP
\fINote\ 10\fR 
\ \(em\ Either the Called party number or the Keypad facility information 
element is included by the user to convey called party number information 
to 
the network. The Keypad facility information element
may also be included by the user to convey other call establishment
information to the network.
.ce
.LP
\ \(em\ Included if the network optionally provides additional information 
describing tones (see \(sc\ 8). 
.LP
\fINote\ 12\fR 
\ \(em\ As a network option, may be used for stimulus operation of
supplementary services (see \(sc\(sc\ 7 and 8).
.LP
\fINote\ 13\fR 
\ \(em\ May be included by the calling user or the network to identify 
the calling user. 
.LP
\fINote\ 14\fR 
\ \(em\ Included in the user\(hyto\(hynetwork direction when the calling user
wants to indicate the calling party subaddress. Included in the network\(hyto\(hyuser 
direction if the calling user included a Calling party subaddress information 
element in the SETUP message. 
.LP
\fINote\ 15\fR 
\ \(em\ Either the Called party number or the Keypad facility information 
element is included by the user to convey called party number information 
to 
the network.
The Called party number information element is included by the network
when called party number information is conveyed to the user.
.LP
\fINote\ 16\fR 
\ \(em\ Included in the user\(hyto\(hynetwork direction when the calling user
wants to indicate the called party subaddress. Included in the network\(hyto\(hyuser 
direction if the calling user included a Called party subaddress information 
element in the SETUP message.
.LP
\fINote\ 17\fR 
\ \(em\ Included by the calling user to select a particular transit
network (see Annex\ C).
.LP
\fINote\ 18\fR 
\ \(em\ Included in the user\(hyto\(hynetwork direction when the calling user
wants to pass low layer compatibility information to the called user.
Included in the network\(hyto\(hyuser direction if the calling user included 
a Low 
layer compatibility information element in the SETUP message.
.LP
\fINote\ 19\fR 
\ \(em\ Included in the user\(hyto\(hynetwork direction when the calling user
wants to pass High layer compatibility information to the called user.
Included in the network\(hyto\(hyuser direction if the calling user included 
a High layer compatibility information element in the SETUP message. 
.LP
\fINote\ 20\fR 
\ \(em\ Included in the user\(hyto\(hynetwork direction when the calling user
wants to pass user information to the called user.
Included in the network\(hyto\(hyuser direction if the calling user included a
user\(hyuser information element in the SETUP message. Conditions for this
transfer are described in \(sc\ 7.
.LP
\fINote\ 21\fR 
\ \(em\ The minimum length is 2 octets;
the standard default maximum length is 131 octets.
\fR 
.ce
\fBH.T. [T17.931]\fR 
.ce
TABLE\ 3\(hy17/Q.931
.ce
\fBSETUP ACKNOWLEDGE message content\fR 
.ce
Message type:\ SETUP ACKNOWLEDGE
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.nr PS 9
.RT
.ad r
\fBNotes to Table 3\(hy16/Q.931 [2T16.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 6P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.17
	\fISetup acknowledge\fR 
.sp 9p
.RT
.PP
This message is sent by the network to the calling user or by the called 
user to the network to indicate that call establishment has been 
initiated, but additional information may be required. See
Table\ 3\(hy17/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T17.931]\fR 
.ce
TABLE\ 3\(hy17/Q.931
.ce
\fBSETUP ACKNOWLEDGE message content\fR 
.ce
Message type:\ SETUP ACKNOWLEDGE
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy17/Q.931 [T17.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 14P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.18
	\fIStatus\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network in response to a
STATUS ENQUIRY message or at any time during a call to report certain error
conditions listed in \(sc\ 5.8. See Table\ 3\(hy18/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T18.931]\fR 
.ce
TABLE\ 3\(hy18/Q.931
.ce
\fBSTATUS message content 
.ce
Message type:\ STATUS
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy18/Q.931 [T18.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 21P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.19
	\fIStatus enquiry\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network at any time to
solicit a STATUS message from the peer layer\ 3 entity. Sending a STATUS 
message in response to a STATUS ENQUIRY message is mandatory. See 
Table\ 3\(hy19/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T19.931]\fR 
.ce
TABLE\ 3\(hy19/Q.931
.ce
\fBSTATUS ENQUIRY message content\fR 
.ce
Message type:\ STATUS ENQUIRY
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy19/Q.931 [T19.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.1.20
	\fISuspend\fR 
.sp 9p
.RT
.PP
This message is sent by the user to request the network to suspend a call. 
See Table\ 3\(hy20/Q.931. 
.RT
.ce
\fR 
.ce
\fBH.T. [T20.931]\fR 
.ce
TABLE\ 3\(hy20/Q.931
.ce
\fBSUSPEND message content\fR 
.ce
Message type:\ SUSPEND
.ce
Significance:\ local
.ce
Direction:\ user to network
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy20/Q.931 [T20.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.21
	\fISuspend acknowledge\fR 
.sp 9p
.RT
.PP
This message is sent by the network to the user to indicate
completion of a request to suspend a call. See Table\ 3\(hy21/Q.931.
.RT
.ce
\fBH.T. [T21.931]\fR 
.ce
TABLE\ 3\(hy21/Q.931
.ce
\fBSUSPEND ACKNOWLEDGE message content 
.ce
Message type:\ SUSPEND ACKNOWLEDGE
.ce
Significance:\ local
.ce
Direction:\ network to user
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy21/Q.931 [T21.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.1.22
	\fISuspend reject\fR 
.sp 9p
.RT
.PP
This message is sent by the network to the user to indicate failure of 
a request to suspend a call. See Table\ 3\(hy22/Q.931. 
.RT
.ce
\fR 
.ce
\fBH.T. [T22.931]\fR 
.ce
TABLE\ 3\(hy22/Q.931
.ce
\fBSUSPEND REJECT message content\fR 
.ce
Message type:\ SUSPEND REJECT
.ce
Significance:\ local
.ce
Direction:\ network to user
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy22/Q.931 [T22.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.23
	\fIUser information\fR 
.sp 9p
.RT
.PP
This message is sent by the user to the network to transfer
information to the remote user. This message is also sent by the network 
to the user to deliver information from the other user. This message is 
used if the 
user\(hyto\(hyuser transfer is part of an allowed information transfer 
as defined in \(sc\(sc\ 7.1.4 or\ 7.1.5. See Table\ 3\(hy23/Q.931. 
.RT
.ce
\fR 
.ce
\fBH.T. [T23.931]\fR 
.ce
TABLE\ 3\(hy23/Q.931
.ce
\fBUSER INFORMATION message content\fR 
.ce
Message type:\ USER INFORMATION
.ce
Significance:\ access
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy23/Q.931 [T23.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 20P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2
	\fIMessages for packet\(hymode access connection control\fR 
.sp 9p
.RT
.PP
Table 3\(hy24/Q.931 summarizes the messages for packet\(hymode access
connection control. The message tables in this paragraph should be used for
Case\ B (packet switched access to an ISDN virtual circuit service) as 
defined in \(sc\ 6. For Case\ A (circuit switched access to PSPDN services) 
the message 
tables in \(sc\ 3.1 should be used.
.RT
.ce
\fR 
.ce
\fBH.T. [T24.931]\fR 
.ce
TABLE\ 3\(hy24/Q.931
.ce
\fBMessages for packet\(hymode access connection control\fR 
.T&
lw(126p) | lw(42p) .
	
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy24/Q.931 [T24.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 22P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.1
	\fIAlerting\fR 
.sp 9p
.RT
.PP
This message is sent by the called user to the network to indicate that 
called user alerting has been initiated. See Table\ 3\(hy25/Q.931. 
.RT
.ce
\fR 
.ce
\fBH.T. [T25.931]\fR 
.ce
TABLE\ 3\(hy25/Q.931
.ce
\fBALERTING message content\fR 
.ce
Message type:\ ALERTING
.ce
Significance:\ local
.ce
Direction:\ user to network
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy25/Q.931 [T25.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 21P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.2
	\fICall proceeding\fR 
.sp 9p
.RT
.PP
This message is sent by the called user to the network or by the
network to the calling user to indicate that the requested access connection
establishment has been initiated. See Table\ 3\(hy26/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T26.931]\fR 
.ce
TABLE\ 3\(hy26/Q.931
.ce
\fBCALL PROCEEDING message content\fR 
.ce
Message type:\ CALL\ PROCEEDING
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy26/Q.931 [T26.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 17P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.3
	\fIConnect\fR 
.sp 9p
.RT
.PP
This message is sent by the called user to the network and by the network 
to the calling user to indicate acceptance of the access connection. 
See Table\ 3\(hy27/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T27.931]\fR 
.ce
TABLE\ 3\(hy27/Q.931
.ce
\fBCONNECT message content\fR 
.ce
Message type:\ CONNECT
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy27/Q.931 [T27.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.4
	\fIConnect acknowledge\fR 
.sp 9p
.RT
.PP
This message is sent by the network to the called user to indicate the 
user has been awarded the access connection. It may also be sent by the 
calling user to the network to allow symmetrical access connection control
procedures. See Table\ 3\(hy28/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T28.931]\fR 
.ce
TABLE\ 3\(hy28/Q.931
.ce
\fBCONNECT ACKNOWLEDGE message content\fR 
.ce
Message type:\ CONNECT ACKNOWLEDGE
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy28/Q.931 [T28.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 25P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.5
	\fIDisconnect\fR 
.sp 9p
.RT
.PP
This message is sent by the user to request the network to clear an access 
connection or is sent by the network to the user to indicate that the 
access connection has been cleared. See Table\ 3\(hy29/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T29.931]\fR 
.ce
TABLE\ 3\(hy29/Q.931
.ce
\fBDISCONNECT message content\fR 
.ce
Message type:\ DISCONNECT
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy29/Q.931 [T29.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 18P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.6
	\fIProgress\fR 
.sp 9p
.RT
.PP
This message is sent by the called user to indicate the progress
of an access connection establishment in the event of interworking within a
private network. See Table\ 3\(hy30/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T30.931]\fR 
.ce
TABLE\ 3\(hy30/Q.931
.ce
\fBPROGRESS message content\fR 
.ce
Message type:\ PROGRESS
.ce
Significance:\ local
.ce
Direction:\ user to network
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy30/Q.931 [T30.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 24P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.7
	\fIRelease\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to indicate that
the equipment sending the message has disconnected the channel (if any) and
intends to release the channel and the call reference, and that the receiving 
equipment should release the channel and prepare to release the call reference 
after sending RELEASE COMPLETE. This message is sent by the network to 
the user to indicate that the access connection is awarded on either the 
D\(hychannel or an existing channel and that the network intends to release 
the call reference. 
See Table\ 3\(hy31/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T31.931]\fR 
.ce
TABLE\ 3\(hy31/Q.931
.ce
\fBRELEASE message content\fR 
.ce
Message type:\ RELEASE
.ce
Significance:\ local (Note 1)
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy31/Q.931 [T31.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 10P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.8
	\fIRelease complete\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to indicate that
the equipment sending the message has released the channel (if any) and call
reference, the channel is available for reuse, and the receiving equipment
shall release the call reference. See Table\ 3\(hy32/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T32.931]\fR 
.ce
TABLE\ 3\(hy32/Q.931
.ce
\fBRELEASE COMPLETE message content\fR 
.ce
Message type:\ RELEASE COMPLETE
.ce
Significance:\ local (Note 1)
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy32/Q.931 [T32.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 12P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.9
	\fISetup\fR 
.sp 9p
.RT
.PP
This message is sent by the calling user to the network and by the network 
to the called user to initiate access connection establishment. See 
Table\ 3\(hy33/Q.931.
.RT
.LP
.sp 1
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [1T33.931]\fR 
.ce
TABLE\ 3\(hy33/Q.931
.ce
\fBSETUP message content\fR 
.ce
Message type:\ SETUP
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy33/Q.931 [1T33.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [2T33.931]\fR 
.LP
\fINote\ 1\fR 
\ \(em\ May be used to describe a CCITT telecommunication service
involving packet\(hymode access connections, if appropriate.
.LP
\fINote\ 2\fR 
\ \(em\ Mandatory in the network\(hyto\(hyuser direction. Included in the
user\(hyto\(hynetwork direction when the user wants to indicate a channel. 
If not 
included, its absence is interpreted as \*Qany channel acceptable\*U.
.LP
\fINote\ 3\fR 
\ \(em\ Included in the event of interworking within a private network.
.LP
\fINote\ 4\fR 
\ \(em\ Included if the network provides information that can be
presented to the user.
.LP
\fINote\ 5\fR 
\ \(em\ The minimum length is 2 octets;
the maximum length is network dependent and is either 34 or 82 octets.
.LP
\fINote\ 6\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25 | 5]/Q.931 information element mapping and provides indication 
to the 
called user of the information rate for the call.
.LP
\fINote\ 7\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25/Q.931 information element mapping and provides indication 
to the called 
user of the maximum permissible transit delay for the call.
.LP
\fINote\ 8\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25/Q.931 information element mapping and provides indication 
to the called 
user of the end\(hyend transit delay for the call.
.LP
\fINote\ 9\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25/Q.931 information element mapping and provides indication 
to the called 
user of the packet layer binary parameters for the call.
.LP
\fINote\ 10\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25/Q.931 information element mapping and provides indication 
to the called 
user of the packet layer window size for the call.
.LP
\fINote\ 11\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25/Q.931 information element mapping and provides indication 
to the called 
user of the packet size for the call.
.LP
\fINote\ 12\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25/Q.931 information element mapping and provides indication 
to the called 
user of the calling party number.
.LP
\fINote\ 13\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25/Q.931 information element mapping and provides indication 
to the called 
user of the calling party subaddress.
.LP
\fINote\ 14\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25/Q.931 information element mapping and provides indication 
to the called 
user of the called party number.
.LP
\fINote\ 15\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25/Q.931 information element mapping and provides indication 
to the called 
user of the called party subaddress.
.LP
\fINote\ 16\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the network 
implements X.25/Q.931 information element mapping and provides indication 
to the called 
user of the number from which a call diversion or transfer was invoked.
.LP
\fINote\ 17\fR 
\ \(em\ Included in the network\(hyto\(hyuser direction if the calling user
included user information and the network implements X.25/Q.931 information
element mapping.
.LP
\fINote\ 18\fR 
\ \(em\ The minimum length is 2 octets;
the standard default maximum length is 131 octets.
.LP
.ce
\fBH.T. [T34.931]\fR 
.ce
TABLE\ 3\(hy34/Q.931
.ce
\fBSTATUS message content 
.ce
Message type:\ STATUS
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBNotes to Table 3\(hy33/Q.931 [2T33.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 14P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.10
	\fIStatus\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network in response to a
STATUS ENQUIRY message or at any time to report certain error conditions 
listed in \(sc\ 5.8. See Table\ 3\(hy34/Q.931. 
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T34.931]\fR 
.ce
TABLE\ 3\(hy34/Q.931
.ce
\fBSTATUS message content 
.ce
Message type:\ STATUS
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy34/Q.931 [T34.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 23P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.2.11
	\fIStatus enquiry\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network at any time to
solicit a STATUS message from the peer layer\ 3 entity. Sending a STATUS 
message in response to a STATUS ENQUIRY message is mandatory. See 
Table\ 3\(hy35/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T35.931]\fR 
.ce
TABLE\ 3\(hy35/Q.931
.ce
\fBSTATUS ENQUIRY message content\fR 
.ce
Message type:\ STATUS ENQUIRY
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy35/Q.931 [T35.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 25P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3
	\fIMessages for user\(hyto\(hyuser signalling not associated with\fR 
\fIcircuit switched calls\fR 
.sp 9p
.RT
.PP
Table 3\(hy36/Q.931 summarizes the messages for the control of
non\(hycall associated temporary signalling connections and the transfer of
user\(hyuser information.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T36.931]\fR 
.ce
TABLE\ 3\(hy36/Q.931
.ce
\fBMessages for temporary signalling connection control\fR 
.T&
lw(126p) | lw(42p) .
	
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy36/Q.931 [T36.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 20P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.1
	\fIAlerting\fR 
.sp 9p
.RT
.PP
This message is sent by the called user to the network and by the network 
to the calling user to indicate that called user alerting has been 
initiated. See Table\ 3\(hy37/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T37.931]\fR 
.ce
TABLE\ 3\(hy37/Q.931
.ce
\fBALERTING message content\fR 
.ce
Message type:\ ALERTING
.ce
Significance:\ global
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy37/Q.931 [T37.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 15P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.2
	\fICall proceeding\fR 
.sp 9p
.RT
.PP
This message is sent by the called user to the network and by the network 
to the calling user to indicate that the requested establishment has 
been initiated and no more call establishment information will be accepted.
See Table\ 3\(hy38/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T38.931]\fR 
.ce
TABLE\ 3\(hy38/Q.931
.ce
\fBCALL PROCEEDING message content\fR 
.ce
Message type:\ CALL\ PROCEEDING
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy38/Q.931 [T38.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 20P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.3
	\fICongestion control\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to indicate the
establishment or termination of flow control on the transmission of USER
INFORMATION messages. See Table\ 3\(hy39/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T39.931]\fR 
.ce
TABLE\ 3\(hy39/Q.931
.ce
\fBCONGESTION CONTROL message content\fR 
.ce
Message type:\ CONGESTION CONTROL
.ce
Significance:\ local (Note 1)
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy39/Q.931 [T39.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 19P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.4
	\fIConnect\fR 
.sp 9p
.RT
.PP
This message is sent by the called user to the network and by the network 
to the calling user to indicate call acceptance by the called user. See 
Table\ 3\(hy40/Q.931. 
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T40.931]\fR 
.ce
TABLE\ 3\(hy40/Q.931
.ce
\fBCONNECT message content\fR 
.ce
Message type:\ CONNECT
.ce
Significance:\ global
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy40/Q.931 [T40.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 15P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.5
	\fIConnect acknowledge\fR 
.sp 9p
.RT
.PP
This message is sent by the network to the called user to indicate the 
user has been awarded the call. It may also be sent by the calling user 
to the network to allow symmetrical call control procedures. See 
Table\ 3\(hy41/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T41.931]\fR 
.ce
TABLE\ 3\(hy41/Q.931
.ce
\fBCONNECT ACKNOWLEDGE message content\fR 
.ce
Message type:\ CONNECT ACKNOWLEDGE
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy41/Q.931 [T41.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 25P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.6
	\fIInformation\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to provide
additional information. It may be used to provide information for call
establishment (e.g.\ overlap sending and receiving) or miscellaneous
call\(hyrelated information. See Table\ 3\(hy42/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T42.931]\fR 
.ce
TABLE\ 3\(hy42/Q.931
.ce
\fBINFORMATION message content\fR 
.ce
Message type:\ INFORMATION
.ce
Significance:\ local (Note 1)
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy42/Q.931 [T42.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 6P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.7
	\fIRelease\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to indicate that
the equipment sending the message has disconnected the channel (if any) and
intends to release the channel and the call reference, and that the receiving 
equipment should release the channel and prepare to release the call reference 
after sending RELEASE COMPLETE. See Table\ 3\(hy43/Q.931. 
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T43.931]\fR 
.ce
TABLE\ 3\(hy43/Q.931
.ce
\fBRELEASE message content\fR 
.ce
Message type:\ RELEASE
.ce
Significance:\ local (Note 1)
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy43/Q.931 [T43.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 13P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.8
	\fIRelease complete\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to indicate that
the equipment sending the message has released the channel (if any) and call
reference, the channel is available for reuse, and the receiving equipment
shall release the call reference. See Table\ 3\(hy44/Q.931.
.RT
.ce
\fR 
.ce
\fR 
.ce
\fBH.T. [T44.931]\fR 
.ce
TABLE\ 3\(hy44/Q.931
.ce
\fBRELEASE COMPLETE message content\fR 
.ce
Message type:\ RELEASE COMPLETE
.ce
Significance:\ local (Note 1)
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy44/Q.931 [T44.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 12P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.9
	\fISetup\fR 
.sp 9p
.RT
.PP
This message is sent by the calling user to the network and by the network 
to the called user to initiate call establishment. See 
Table\ 3\(hy45/Q.931.
.RT
.ce
\fBH.T. [1T45.931]\fR 
.ce
TABLE\ 3\(hy45/Q.931
.ce
\fBSETUP message content\fR 
.ce
Message type:\ SETUP
.ce
Significance:\ global
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy45/Q.931 [1T45.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 2P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [2T45.931]\fR 
.LP
\fINote\ 1\fR 
\ \(em\ Included if the user or the network optionally indicates that all
information necessary for call establishment is included in the SETUP message.
.LP
\fINote\ 2\fR 
\ \(em\ The Bearer capability and compatibility information elements may
be used to describe a CCITT telecommunication service, if appropriate.
.LP
\fINote\ 3\fR 
\ \(em\ Included by the calling user or the network to indicate network
specific facilities information (see Annex\ E).
.LP
\fINote\ 4\fR 
\ \(em\ Included if the network provides information that can be
presented to the user.
.LP
\ \(em\ The minimum length is 2 octets;
.LP
\fINote\ 5\fR 
the maximum length is network dependent and is either 34 or 82 octets.
.LP
\fINote\ 6\fR 
\ \(em\ Either the Called party number or the Keypad facility information
element is included by the user to convey called party number information to
the network during overlap sending. The Keypad facility information element
may also be included by the user to convey other call establishment
information to the network.
.LP
\fINote\ 7\fR 
\ \(em\ May be included by the calling user or the network to identify 
the calling user. 
.LP
\fINote\ 8\fR 
\ \(em\ Included in the user\(hyto\(hynetwork direction when the calling user
wants to indicate the calling party subaddress. Included in the network\(hyto\(hyuser 
direction if the calling user included a Calling party subaddress information 
element in the SETUP message. 
.LP
\fINote\ 9\fR 
\ \(em\ Either the Called party number or the Keypad facility information
element is included by the user to convey called party number information to
the network.
The Called party number information element is included by the network
when called party number information is conveyed to the user.
.LP
\fINote\ 10\fR 
\ \(em\ Included in the user\(hyto\(hynetwork direction when the calling user
wants to indicate the called party subaddress. Included in the network\(hyto\(hyuser 
direction if the calling user included a Called party subaddress information 
element in the SETUP message.
.LP
\fINote\ 11\fR 
\ \(em\ Included by the calling user to select a particular transit
network (see Annex C).
.LP
\fINote\ 12\fR 
\ \(em\ Included in the user\(hyto\(hynetwork direction when the calling user
wants to pass low layer compatibility information to the called user.
Included in the network\(hyto\(hyuser direction if the calling user included 
a low 
layer compatibility information element in the SETUP message.
.LP
\fINote\ 13\fR 
\ \(em\ Included in the user\(hyto\(hynetwork direction when the calling user
wants to pass high layer compatibility information to the called user.
Included in the network\(hyto\(hyuser direction if the calling user included 
a high layer compatibility information element in the SETUP message. 
.LP
\fINote\ 14\fR 
\ \(em\ Included in the user\(hyto\(hynetwork direction when the calling user
wants to pass user information to the called user.
Included in the network\(hyto\(hyuser direction if the calling user included a
user\(hyuser information element in the SETUP message. Conditions for this
transfer are described in \(sc\ 7.
.LP
\fINote\ 15\fR 
\ \(em\ The minimum length is 2 octets;
the standard default maximum length is 131 octets.
.ce
\fBH.T. [T46.931]\fR 
.ce
TABLE\ 3\(hy46/Q.931
.ce
\fBSETUP ACKNOWLEDGE message content\fR 
.ce
Message type:\ SETUP ACKNOWLEDGE
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBNotes to Table 3\(hy45/Q.931 [2T45.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 17P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.10
	\fISetup acknowledge\fR 
.sp 9p
.RT
.PP
This message is sent by the network to the calling user or by the called 
user to the network to indicate that call establishment has been 
initiated, but additional information may be required. See
Table\ 3\(hy46/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T46.931]\fR 
.ce
TABLE\ 3\(hy46/Q.931
.ce
\fBSETUP ACKNOWLEDGE message content\fR 
.ce
Message type:\ SETUP ACKNOWLEDGE
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy46/Q.931 [T46.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 22P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.11
	\fIStatus\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network in response to a
STATUS ENQUIRY message or at any time to report error conditions listed in
\(sc\ 5.8. See Table\ 3\(hy47/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T47.931]\fR 
.ce
TABLE\ 3\(hy47/Q.931
.ce
\fBSTATUS message content 
.ce
Message type:\ STATUS
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy47/Q.931 [T47.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 21P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.3.12
	\fIStatus enquiry\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network at any time to
solicit a STATUS message from the peer layer\ 3 entity. Sending a STATUS 
message in response to a STATUS ENQUIRY message is mandatory. See 
Table\ 3\(hy48/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T48.931]\fR 
.ce
TABLE\ 3\(hy48/Q.931
.ce
\fBSTATUS ENQUIRY message content 
.ce
Message type:\ STATUS ENQUIRY
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy48/Q.931 [T48.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.3.13
	\fIUser information\fR 
.sp 9p
.RT
.PP
This message is sent by the user to the network to transfer
information to the remote user. This message is also sent by the network 
to the user to deliver information from the other user. See Table\ 3\(hy49/Q.931. 
.RT
.ce
\fBH.T. [T49.931]\fR 
.ce
TABLE\ 3\(hy49/Q.931
.ce
\fBUSER INFORMATION message content\fR 
.ce
Message type:\ USER INFORMATION
.ce
Significance:\ access
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy49/Q.931 [T49.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.4
	\fIMessages used with the global call reference\fR 
.sp 9p
.RT
.PP
Table 3\(hy50/Q.931 summarizes the messages which may use the global call 
reference defined in \(sc\ 4.3. 
.RT
.ce
\fR 
.ce
\fBH.T. [T50.931]\fR 
.ce
TABLE\ 3\(hy50/Q.931
.ce
\fBMessages used with the global call reference\fR 
.T&
lw(126p) | lw(42p) .
	
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy50/Q.931 [T50.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.4.1
	\fIRestart\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network to request the
recipient to restart (i.e.,\ return to idle condition) the indicated channel(s) 
or interface. See Table\ 3\(hy51/Q.931. 
.RT
.ce
\fR 
.ce
\fBH.T. [T51.931]\fR 
.ce
TABLE\ 3\(hy51/Q.931
.ce
\fBRESTART message content\fR 
.ce
Message type:\ RESTART
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy51/Q.931 [T51.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.4.2
	\fIRestart acknowledge\fR 
.sp 9p
.RT
.PP
This message is sent to acknowledge the receipt of a RESTART
message and to indicate that the requested restart is complete. See
Table\ 3\(hy52/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T52.931]\fR 
.ce
TABLE\ 3\(hy52/Q.931
.ce
\fBRESTART ACKNOWLEDGE message content\fR 
.ce
Message type:\ RESTART ACKNOWLEDGE
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy52/Q.931 [T52.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 19P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.4.3
	\fIStatus\fR 
.sp 9p
.RT
.PP
This message is sent by the user or the network
at any time during a call to report certain error
conditions listed in \(sc\ 5.8. See Table\ 3\(hy53/Q.931.
.RT
.ce
\fR 
.ce
\fBH.T. [T53.931]\fR 
.ce
TABLE\ 3\(hy53/Q.931
.ce
\fBSTATUS message content 
.ce
Message type:\ STATUS
.ce
Significance:\ local
.ce
Direction:\ both
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
lw(84p) | lw(36p) | lw(36p) | lw(36p) | lw(36p) .
				
.TE
.nr PS 9
.RT
.ad r
\fBTable 3\(hy53/Q.931 [T53.931], p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 19P
.ad r
Blanc
.ad b
.RT
.LP
.bp