[Softwires] DS-Lite fragmentation RFC2473 reference
Daniel Roesen <dr@cluenet.de> Tue, 11 October 2011 12:37 UTC
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Date: Tue, 11 Oct 2011 14:37:27 +0200
From: Daniel Roesen <dr@cluenet.de>
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Subject: [Softwires] DS-Lite fragmentation RFC2473 reference
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Hi, the DS-Lite spec states: 5.3. Fragmentation and Reassembly ... [...] The inner IPv4 packet MUST NOT be fragmented. Fragmentation MUST happen after the encapsulation of the IPv6 packet. Reassembly MUST happen before the decapsulation of the IPv4 packet. A detailed procedure has been specified in [RFC2473] Section 7.2. The change from "fragment the IPv4 payload" to "fragment the IPv6 tunnel packet" came between draft-ietf-softwire-dual-stack-lite-00 and -01: http://tools.ietf.org/rfcdiff?url2=draft-ietf-softwire-dual-stack-lite-01.txt The probable trigger was: http://www.ietf.org/mail-archive/web/softwires/current/msg00756.html No reasoning has been provided on the list, nor was the change in -01 commented. I'm wondering what the reasoning was to mandate tunnel packet fragmentation instead of payload. Could anyone give some insights? Theoretically there should be no adverse impact by AFTR fragmenting the NATted IPv4 payload packets for transmission into the tunnel to the B4. Reassembly would be offloaded from the B4 to the endpoint behind the B4. I've investigated a bit and found reports of SIP implementations having serious problems with fragmented UDP, as well as Microsoft AD/Kerberos: http://blog.tmcnet.com/third-screen/2009/03/udp_fragmentation_breaks_sip_in_todays_ip-pbxs.html http://blogs.technet.com/b/asiasupp/archive/2006/09/19/457413.aspx Any insight appreciated! Best regards, Daniel PS: yes, fragmenting the tunnel packets is of course the most transparent way end-to-end, but it comes at a price... -- CLUE-RIPE -- Jabber: dr@cluenet.de -- dr@IRCnet -- PGP: 0xA85C8AA0
- [Softwires] DS-Lite fragmentation RFC2473 referen… Daniel Roesen
- Re: [Softwires] DS-Lite fragmentation RFC2473 ref… Francis Dupont
- Re: [Softwires] DS-Lite fragmentation RFC2473 ref… Lee, Yiu
- Re: [Softwires] DS-Lite fragmentation RFC2473 ref… Daniel Roesen