Question 27/VII - Open Systems Interconnection (OSI) transport and
network layers (continuation of part of Question 43/VII studied in 1985-
1988 on OSI transport and network layers

Considering

(a) that Recommendation X.200 specifies the reference model of Open
Systems Interconnection for CCITT applications;

(b) that Recommendation X.210 specifies the layer service definition
conventions of Open Systems Interconnection for CCITT applications;

(c) that Recommendation X.213 specifies the network service of Open
Systems Interconnection for CCITT applications;

(d) that Recommendation X.214 specifies the transport service of Open
Systems Interconnection for CCITT applications;

(e) that Recommendation X.224 specifies the transport protocol of Open
Systems Interconnection for CCITT applications;

(f) that Recommendation X.244 specifies the procedure for the exchange
of protocol identification during virtual call establishment on public
networks;

(g) that administrations and users in many countries are applying the
Open Systems Interconnection family of Recommendations to public
networks now existing or due to be available in the near future;

(h) that close collaboration and liaison with other international bodies
(e.g., ISO, IEC) studying Open Systems Interconnection is highly
desirable,

1. Transport layer

What further refinements are required to transport layer Recommendations
X.214 and X.224?

In particular, studies should include:

a) What further consideration needs to be given to Quality of Service
issues?

b) Is there a need for further protocol to allow transport entities to
negotiate the use and control of network service connections, and layer
management issues in general?

c) What consideration needs to be given for addition of formal
descriptions to Recommendations X.214 and X.224?

d) What consideration needs to be given to addressing requirements for
the transport layer?

e) What further relationships between the Transport Layer and adjacent
layers need to be defined?

f) What further consideration is needed for OSI/non OSI protocol
identification?

g) What further consideration needs to be given to transport layer
management?

h) What further consideration needs to be given to transport layer
security?

2. Network Service

What further refinements are required to the network service
Recommendation X.213 recognizing:

a) that users need to communicate with each other irrespective of the
diversity of interconnected networks?

b) that methodical representation of networks and their capabilities
will further promote the effective and efficient use of public data
networks;

c) a universally applicable Network Service should be used in the
development of compatible service, interface and procedure definitions;

d) that such a Network Service should as far as possible accommodate
existing Recommendations to allow the steady evolution of new networks
and the new services.

In particular,

a) What further consideration needs to be given to Quality of Service
issues?

b) What consideration needs to be given to the addition of a formal
description to Recommendation X.213?

c) Does any requirement for compatibility checking within the network
layer affect the network service, and if so, how?

d) What further consideration needs to be given to CCITT defined
services, DTE/DCE interface Recommendations, ISDN and international
inter- exchange signalling system, in relation to the network service?

e) Are any further refinements required to cover the case of point-
multipoint operation?

f) Are any further refinements required to cover the case of multi-
stage connection establishment?

g) What further consideration needs to be given to OSI network layer
addressing? For example, what mechanisms are required to facilitate the
derivation of sub-network addresses from OSI network addresses?

h) What further consideration needs to be given to OSI network layer
management?

i) What further consideration needs to be given to OSI network layer
security?

3. Liaison

What is necessary to maintain cooperation with other international
organizations (e.g., ISO/IEC JTC 1) in activities concerning the
transport and network layers for OSI?