Annex G & big messages (and TPKT and Annex E)

[Andrew Draper]

At 09:35 1999-05-04 +0200, ETO wrote:
>When an Annex G message will exceed max packet size (typically a
>DescriptorConfirm) on UDP, a Reject might be sent, and the session is
>repeated on TCP.
>
>But, isn't our PDU size on TCP also limited? When using TPK,
the max pdu
>size is 65k too, as seen in RFC-1006....

I don't think this is a problem for Annex G.

First, a sensible implementation is probably sending DescriptorRequests over
TCP anyway since it expects a large (well larger than MRU) answer anyway so
the UDP step described above won't happen (only AccessRequest and
ValidationRequest is likely to be sent over UDP).

Secondly, the only message likely to run into the maximum message size limit
is the DescriptorConfirm (if a descriptor is more than 64K).  I don't expect
anyone to have a descriptor of 64K or more, but if they do it can be broken
down into multiple descriptors, and each one transmitted separately.

For call signalling over annex E the message size limit isn't a problem
either.  Annex E will be transmitting the same call signalling messages as
would be sent over TPKT over TCP, so messages of more than 64K aren't
allowed (since they wouldn't fit within TPKT), even if anyone can create a
plausible one.

Regards,

  Andy

--
Andrew Draper --  Principal Development Engineer  -- WAVE Software
Madge Networks, Wexham Springs, Framewood Road, Wexham, Berks, UK.
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