Question 16/VII - Packet mode signalling between public networks
providing data transmission services (continuation of Question 22/VII
studied in 1985-88)

Considering

(a) that Recommendation X.75 already specifies the packet mode
signalling system between public networks providing data transmission
services;

(b) that Recommendation X.75 applies to all links between packet
switched public data networks (PSPDNs) in different countries as well as
links between PSPDNs and ISDNs, and between ISDNs, as defined in
Recommendations X.31 and the X.300-Series;

(c) that Recommendation X.75 may also apply to national links for
interworking scenarios given in (b) above, within the same country;

(d) that Recommendation X.75 is considered for interworking between an
ISDN offering X.31 based packet mode services and another ISDN offering
additional packet mode services in the future, as defined in the ISDN
services framework Recommendation I.122;

(e) that Recommendation X.75 is being used between a very large number
of networks around the world, and that it has reached a level of
maturity;

(f) that Recommendation X.75 includes the protocol elements necessary to
support the network layer service for interworking situations;

(g) that there is a need for bearer rates higher than 64 kbps, higher
throughput and reliability for X.75 links between networks,

the following points should be studied:

1. What additions or modifications to Recommendation X.75 are needed to
enhance the interworking arrangements for scenarios covered in (b), (c)
and (d) above?

2. What additions or modifications to other packet mode interworking
Recommendations, such as X.323, X.180 and X.181, are needed to enhance
the interworking arrangements?

3. What additional Recommendations or enhancements to existing
Recommendations are required for operations, administrations and
maintenance (OA&M) signalling over X.75 for interworking arrangements
given above, in liaison with Question 12/VII?

4. What additional Recommendations or enhancements to existing
Recommendations are needed to support packet mode interworking
arrangements between new types of interworking arrangements, if any?

Specific points to be covered may include, among others:

1. Points for further study in Recommendation X.75.

2. Enhancements to improve reliability and throughput performance of
X.75 links with higher than 64 kbit/s signalling rates.

3. Enhancements to multi-link procedures, in close cooperation with ISO
and X.25.

4. Additional link layer and/or packet layer signalling for X.75 link
maintenance.

5. Additional signalling over M.75 links for OA&M aspects of virtual
calls and permanent virtual circuits, including:

-maintenance;

-billing and accounting;

-provisioning;

-monitoring;

-testing.

6. Additional signalling over M.75 links to support those X.2 user
facilities currently limited to one network, in interworking scenarios
mentioned above. In particular, X.75 utility signalling for internetwork
call redirection and deflection.

7. Enhancements for the provision of international permanent virtual
circuits.

8. Enhancements to the procedure and the format for NUI utility
signalling.

9. The need for and definition of traffic class utility.

10. Alternative ways of network identification for the purpose of X.75
utility signalling.

11. Alignment of Recommendation X.75 with Recommendation X.25 where
appropriate.

12. Enhancements to QOS signalling over X.75.

13. Enhancements to addressing and routing aspects of X.75.