Subject: (ION) comments on nhrp flow extensions

From: [email-masked] (Matthew Squire)
Date: Thu, 09 Jul 1998 10:23:54 -0400

Wanted to pass on a few comments on the flow extensions draft...

1) I'm not sure how the ToS mask field works.  It seems to assume that the
ToS field is a bit field, where each bit has meaning and by setting
additional bits one "restricts" the flows.   With DiffServ, no one knows
yet what the field is going to look like, and whether specific bits will
have meaning or not.  Even with the requirements specified in rfc1349 and
rfc1123, the interpretation is not amendable to restricting flows by
setting more bits in a mask.  

2) Seems like problems can arise if transit NHSs which do not understand
the flow extension can cache replies.   The IP/NBMA binding in a successful
response with a flow extension is restricted only to that flow, but
"non-flow" transit NHSs may cache the IP/NBMA binding and use it to give
non-authoritative responses to future requests.  You probably want to
eliminate this possibility.  I guess you could make the extension
compulsory, or require authoritative responses, or don't permit caching of
responses.  

3) Might be useful to permit/prohibit the use of source flow binding in a
manner similar to the way NHRP can use the source IP/NBMA in requests (ie
S-bit, which I'm assuming still just applies to the source IP/NBMA and not
the source flow).  Haven't thought this all the way through yet, but seems
in line with the current spec.  

- Matt
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