X.25 TYPE NUMBERS

(last updated 2007-08-30)

ITU-T TSB defines the high order two bits of the first octet of call user
data as follows:


00 - Used for other ITU-T TSB recommendations (such as X.29)
01 - Reserved for use by "national" administrative
     authorities
10 - Reserved for use by international administrative authorities
11 - Reserved for arbitrary use between consenting DTEs

Call User Data (hex)     Protocol                      Reference
-------------------      --------                      ---------

01                       PAD                               [AXL]
C5                       Blacker front-end descr dev       [AXL]
CC                       IP                         [RFC877,AXL]*
CD                       ISO-IP                            [AXL]             
CF                       PPP                           [RFC1598]
DD                       Network Monitoring                [AXL]

*NOTE: ISO SC6/WG2 approved assignment in ISO 9577 (January 1990).


REFERENCES

[RFC877] Korb, J., "A Standard for the Transmission of IP Datagrams
         Over Public Data Networks", RFC 877, Purdue University,
         September 1983.

[RFC1598] Simpson, W., "PPPin X.25", RFC 1598, Daydreamer, March 1994.


PEOPLE

[AXL]     Alain Lanssiers <alanssie&cisco.com>

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