Re: [RAM] Re: Tunneling overheads and fragmentation
David Meyer <dmm@1-4-5.net> Thu, 19 July 2007 16:30 UTC
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Date: Thu, 19 Jul 2007 09:30:33 -0700
From: David Meyer <dmm@1-4-5.net>
To: Stephane Bortzmeyer <bortzmeyer@nic.fr>
Subject: Re: [RAM] Re: Tunneling overheads and fragmentation
Message-ID: <20070719163033.GA17293@1-4-5.net>
References: <469F7673.6070702@firstpr.com.au> <20070719160125.GA16217@nic.fr>
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Cc: Robin Whittle <rw@firstpr.com.au>, ram@iab.org
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On Thu, Jul 19, 2007 at 06:01:25PM +0200, Stephane Bortzmeyer wrote: > On Fri, Jul 20, 2007 at 12:34:27AM +1000, > Robin Whittle <rw@firstpr.com.au> wrote > a message of 54 lines which said: > > > Can anyone help me understand the likely problems with tunneling > > packets and what MTU limits might be exceeded if LISP, eFIT-APT or > > Ivip is used with IPv4? > > Executive summary: tunnels create a lot of problems (see the RFC > indicated by Fred Templin plus RFC 2923). The whole thing with PMTU discovery continues to come up whenever we debate tunneling. We spent a lot of time trying to document that particular issue in RFC 2784 (GRE). > > For instance, if all provider and transit routers happily handle > > packets significantly longer than whatever hosts normally produce > > (say 1500 bytes) then adding the encapsulation won't lead to any > > fragmentation. Is this a reasonable assumption? > > I do not think so. Agreed. As mentioned above, there is also the interaction with PMTU discovery; basically, it can be nontrivial to find the original source of the packet so you can send a a "fragmentation needed and DF set" back to the source. If indeed you can't find the source (multiple encaps or whatever), then the source's packets (those that have the DF bit set, i.e., doing PMTU discovery) get black-holed. Not sure if that was your question, but in any event... Dave
_______________________________________________ RAM mailing list RAM@iab.org https://www1.ietf.org/mailman/listinfo/ram
- RE: [RAM] Tunneling overheads and fragmentation Templin, Fred L
- [RAM] Tunneling overheads and fragmentation Robin Whittle
- [RAM] Re: Tunneling overheads and fragmentation Stephane Bortzmeyer
- Re: [RAM] Re: Tunneling overheads and fragmentati… Iljitsch van Beijnum
- Re: [RAM] Re: Tunneling overheads and fragmentati… David Meyer
- Re: [RAM] Tunneling overheads and fragmentation Wassim Haddad
- Re: [RAM] Tunneling overheads and fragmentation Robin Whittle
- Re: [RAM] Tunneling overheads and fragmentation Gert Doering
- Re: [RAM] Tunneling overheads and fragmentation Robin Whittle
- Re: [RAM] Tunneling overheads and fragmentation Marshall Eubanks
- Re: [RAM] Tunneling overheads and fragmentation Robin Whittle
- Re: [RAM] Tunneling overheads and fragmentation Iljitsch van Beijnum
- Re: [RRG] Re: [RAM] Tunneling overheads and fragm… Iljitsch van Beijnum
- Re: [RRG] Re: [RAM] Tunneling overheads and fragm… Dino Farinacci
- Re: [RRG] Re: [RAM] Tunneling overheads and fragm… Iljitsch van Beijnum
- Re: [RRG] Re: [RAM] Tunneling overheads and fragm… Dino Farinacci
- Re: [RRG] Re: [RAM] Tunneling overheads and fragm… Dino Farinacci
- Re: [RRG] Re: [RAM] Tunneling overheads and fragm… Pekka Savola
- Re: [RRG] Re: [RAM] Tunneling overheads and fragm… Gert Doering
- Re: [RRG] Re: [RAM] Tunneling overheads and fragm… Gert Doering
- Re: [RRG] Re: [RAM] Tunneling overheads and fragm… Dino Farinacci