APPENDIX IV

(to Recommendation X.223)

Differences between Recommendation X.223 and ISO 8878

The following differences exist between Recommendation X.223 and ISO 8878.

IV.1	In Recommendation X.223, the text in § 6.2.2.1.1 specifies that given conditions a) through d), the address is always carried in the Address Field (AF). ISO 8878 specifies that given conditions a) through c) (ISO 8878 does not include condition d), the address may optionally be carried in the AF.

IV.2	In Recommendation X.223, the text in § 6.2.4 specifies that if "no use of Expedited Data" is indicated or if the NL entity cannot support 32-octet INTERRUPT packets, then the EDN facility is always omitted. For the same case, ISO 8878 specifies that the EDN facility either may be carried specifying "no use of Expedited Data", or may be omitted.

IV.3	In § 6.2.5.1 (Throughput QOS Parameters) of Recommendation X.223, two new paragraphs have been added which are not present in ISO 8878. These paragraphs are the last paragraph in § 6.2.5.1.1, and the last paragraph in § 6.2.5.1.2.

Collectively, these paragraphs specify that whenever the Lowest Quality Acceptable sub-parameters of the Throughput QOS Parameters for both directions are "unspecified" in the N-CONNECT request, the MTCN facility is not included in the CALL REQUEST packet. ISO 8878 specifies that in such a case, the MTCN facility is encoded as 75 bits per second.

IV.4	In § 6.2.5.2 (Transit Delay QOS Parameter) of Recommendation X.223, four new paragraphs have been added which are not present in ISO 8878. These paragraphs are the last paragraph in § 6.2.5.2.1, the last paragraph in § 6.2.5.2.2, the last paragraph in § 6.2.5.2.3, and the last paragraph in § 6.2.5.2.4.

Collectively, these paragraphs specify that whenever the Target and Lowest Quality Acceptable sub-parameters of the Transit Delay QOS Parameter are "unspecified" in the N-CONNECT request, the EETDN facility is not included in the CALL REQUEST packet. ISO 8878 does not explicitly address such a case, and actually implicitly invalidates it per the conditions in items a) -d).

Additionally, in § 6.2.5.2.1 of Recommendation X.223, the last sentence in item d) specifies that in DTE-to-DTE operational environments the usage of the TDSAI facility is for further study. ISO 8878 does not have such a sentence.

IV.5	In § 6.2.5.2.1 of Recommendation X.223, there is only one note after item d). ISO 8878 contains two notes after item d), the first of which is identical to the one note in X.223. ISO has initiated the necessary procedures to remove their second note.

IV.6	The scope of Recommendation X.223 does not include for provision of the OSI Connection-mode Network Service over 1980 X.25 sub-networks. Conversely, ISO 8878 provides for this and defines a protocol mechanism in Annex A. Also, material related to conformance issues, including those raised by the presence of Annex A, is included in Annex B to ISO 8878 and is not included in this Recommendation.