[PWOT] Re: comment on latest draft-martini-l2circuit-encap-mpls-01.txt
Dan Tappan <tappan@cisco.com> Tue, 20 March 2001 00:15 UTC
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Date: Mon, 19 Mar 2001 19:08:28 -0500
To: "Shah, Himanshu" <hshah@tenornetworks.com>
From: Dan Tappan <tappan@cisco.com>
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Subject: [PWOT] Re: comment on latest draft-martini-l2circuit-encap-mpls-01.txt
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[ moved to the right working group list] At 04:34 PM 3/16/2001 -0500, you wrote: >Hello Luca, > >Sorry for the late comment, I didn't know of this draft until recently. >I see the addition of the control word and algorithm for handling >sequence numbers on send and receive side. > >It seems that sequence check on receive side does not handle the >wrap around correctly, i.e. finds the out-of-sequence little too late. > >For example if the max was 64, > >sender receiver's expected Seq > >62 -> 62, next: 62+1=63 >64 -> 63, 64>=63 packet in order. Next: 64+1=1, wrapped >63 -> 1, 63>=1 packet in order. Next: 63+1=64 >1 -> 64, 1 !>=64. packet out-of-order, drop, next:1+1=2 > >As shown above, out-of-order packet already forwarded! In general with a circular sequence number space you need to include the concept of a 'window' - the maximum sequence number that is reasonable to receive. This got left out of the definition in the draft. My inclination would be to define the window to 1/2 the sequence space (it could be made arbitrarily smaller, but there may not be any point). So, in your example above: - 63 > 1 + window, so discard - 1 == 1, in sequence _______________________________________________ pwot mailing list pwot@ietf.org http://www.ietf.org/mailman/listinfo/pwot
- [PWOT] Re: comment on latest draft-martini-l2circ… Dan Tappan
- Re: [PWOT] Re: comment on latest draft-martini-l2… Stephen Casner