Re: ISO8473 vs. IP


Robert Hagens (hagens@janeb.wisc.edu)
Tue, 8 Sep 87 11:37:55 CDT


Comparison of DoD IP and ISO IP:

As Paul pointed out, functionally the same. Here are some other differences:

- No upper layer protocol ID in ISO8473.
- Headers in ISO8473 can be 255 octets (vs. 60 for DoD IP).
- Support of header parameters is optional in ISO8473, mandatory in DoD IP.
- Time to live in ISO8473 is 1/2 sec as opposed to 1 sec for DoD IP.
        (It will still end up being used as a hop count.)
- No timestamp parameter in ISO8473.
- Fixed part of ISO8473 header has odd byte aligned, 2 byte fields.
- DoD IP fragmentation is called segmentation in ISO. Identical function,
        however all ISO8473 optional parameters are carried with fragment.
        (Called a derived PDU).

Only in ISO8473:
- Error Report PDU. Sent when a data PDU is discarded. Almost identical to
        data pdu except it contains the reason for discard. Data of error
        report PDU is header of discarded PDU. Error report contains
        ICMP functionality of destination unreachable, ttl expired and
        parameter problem.
- 'congestion experienced'. Set by a router, when a router
        experiences congestion.

The two biggest differences I see are the address part and lack of
upper layer proto id.

Rob Hagens
UW Madison Computer Science



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