Re: [v4tov6transition] [Softwires] IPv6 VPNs configured over1280MTU tunnels
"Templin, Fred L" <Fred.L.Templin@boeing.com> Mon, 11 October 2010 23:18 UTC
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From: "Templin, Fred L" <Fred.L.Templin@boeing.com>
To: Brian E Carpenter <brian.e.carpenter@gmail.com>
Date: Mon, 11 Oct 2010 16:19:32 -0700
Thread-Topic: [Softwires] [v4tov6transition] IPv6 VPNs configured over1280MTU tunnels
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Cc: Softwires <softwires@ietf.org>, "v4tov6transition@ietf.org" <v4tov6transition@ietf.org>
Subject: Re: [v4tov6transition] [Softwires] IPv6 VPNs configured over1280MTU tunnels
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Hi Brian, > -----Original Message----- > From: softwires-bounces@ietf.org > [mailto:softwires-bounces@ietf.org] On Behalf Of Brian E Carpenter > Sent: Monday, October 11, 2010 2:26 PM > To: Templin, Fred L > Cc: Softwires; v4tov6transition@ietf.org > Subject: Re: [Softwires] [v4tov6transition] IPv6 VPNs > configured over1280MTU tunnels > > Fred > > On 2010-10-12 07:23, Templin, Fred L wrote: > >>> In the to-host direction, because the ISP network is all what > >>> is left to traverse before reaching the CPE. > >> In what you call the to-host direction, any ICMPv4 > >> returned from the ISP network might not have enough > >> information for stateless translation to ICMPv6. > > > > I should also say, any ICMPv4 returned from within > > the end user network (where MTUs might not be so well > > managed) might not be delivered to the tunnel endpoint > > in the ISP network. > > Well, yes, and there were several years when I frequently found myself > in hotel rooms having to manually set the IPv4 MTU on my laptop to a > low value, when connecting through broken dial-up ISPs. No doubt > we'll also go through some years before all operators are providing > an adequately large MTU to cope with IPv6-in-foo tunnels. I don't > think any transition solution can hope to be 100% watertight > on this. IROM (vis-a-vis SEAL) is striving for a true tunnel MTU solution and I think has made significant strides. The SEAL approach is dissimilar from IPv4 PMTUD in that it is the tunnel far end (and not a router on the path) that returns the PTB message. SEAL relies on routers in the path correctly implementing IPv4 fragmentation, which is a required behavior even for tunnel paths that traverse untrusted/unmanaged domains. SEAL's only requirement is that the IPv4 first fragment of a fragmented IPv4 datagram contain at least enough information to include a tunnel identifier. The minimum size for a first fragment is 8 bytes beyond the IP header, since the fragment offset field counts the number of 8 byte blocks. Common operational practices also suggest that routers tend to make the first fragment be approximately MTU-sized since this may be useful to allow the destination to measure the path MTU. There is also enough uncertainty about tiny fragment attacks (RFC1858, RFC3128, etc.) that it seems highly unlikely that the first fragment of a multi-fragment IPv4 datagram would contain less than 16 bytes (UDP header plus enough extra to contain a tunnel ID). > We'll make the changes that Rémi mentioned, but > you're correct that IPv6-in6a44 tunnels might have MTU issues. Please have a look at my tunnel MTU guy when deciding how to set the static MTU configuration knob: http://www.ietf.org/mail-archive/web/softwires/current/msg01659.html The term "configuration knob" came from RFC4213, which also has an analysis of setting a static MTU that may be helpful. But, remember that VPNs configured over paths containing IPv6-in-IPv4 tunnels will need more headroom, so 1280 seems insufficient. Thanks - Fred fred.l.templin@boeing.com > Brian > > _______________________________________________ > Softwires mailing list > Softwires@ietf.org > https://www.ietf.org/mailman/listinfo/softwires >
- [v4tov6transition] ISP support of Native IPv6 acr… Rémi Després
- Re: [v4tov6transition] [Softwires] ISP support of… Brian E Carpenter
- Re: [v4tov6transition] [Softwires] ISP support of… Ole Troan
- Re: [v4tov6transition] [Softwires] ISP support of… Brian E Carpenter
- Re: [v4tov6transition] [Softwires] ISP support of… Templin, Fred L
- Re: [v4tov6transition] [Softwires] ISP support of… Yiu L. Lee
- Re: [v4tov6transition] [Softwires] ISP support of… Yiu L. Lee
- Re: [v4tov6transition] [Softwires] ISP support of… Rémi Després
- Re: [v4tov6transition] [Softwires] ISP support of… Ole Troan
- Re: [v4tov6transition] [Softwires] ISP support of… Yiu L. Lee
- Re: [v4tov6transition] [Softwires] ISP support of… Rémi Després
- Re: [v4tov6transition] [Softwires] ISP support of… Rémi Després
- Re: [v4tov6transition] [Softwires] ISP support of… Templin, Fred L
- Re: [v4tov6transition] [Softwires] ISP support of… Ole Troan
- Re: [v4tov6transition] [Softwires] ISP support of… Brian E Carpenter
- Re: [v4tov6transition] [Softwires] ISP support of… Brian E Carpenter
- Re: [v4tov6transition] [Softwires] ISP support of… Brian E Carpenter
- Re: [v4tov6transition] [Softwires] ISP support of… Olivier Vautrin
- Re: [v4tov6transition] [Softwires] ISP support of… Cameron Byrne
- Re: [v4tov6transition] [Softwires] ISP support of… Ed Jankiewicz
- Re: [v4tov6transition] [Softwires] ISP support of… Rémi Després
- Re: [v4tov6transition] [Softwires] ISP support of… Ole Troan
- Re: [v4tov6transition] [Softwires] ISP support of… Rémi Després
- Re: [v4tov6transition] [Softwires] ISP support of… Templin, Fred L
- [v4tov6transition] IPv6 VPNs configured over 1280… Templin, Fred L
- Re: [v4tov6transition] IPv6 VPNs configured over … Templin, Fred L
- Re: [v4tov6transition] [Softwires] ISP support of… Yiu L. Lee
- Re: [v4tov6transition] [Softwires] ISP support of… Templin, Fred L
- Re: [v4tov6transition] [Softwires] ISP support of… Yiu L. Lee
- Re: [v4tov6transition] [Softwires] ISP support of… Templin, Fred L
- Re: [v4tov6transition] [Softwires] ISP support of… Yiu L. Lee
- Re: [v4tov6transition] IPv6 VPNs configured over … Washam Fan
- Re: [v4tov6transition] ISP support of Native IPv6… Tina TSOU
- Re: [v4tov6transition] ISP support of Native IPv6… Brian E Carpenter
- Re: [v4tov6transition] IPv6 VPNs configured over … Templin, Fred L
- Re: [v4tov6transition] IPv6 VPNs configured over … Rémi Després
- Re: [v4tov6transition] IPv6 VPNs configured over … Templin, Fred L
- Re: [v4tov6transition] IPv6 VPNs configured over … Rémi Després
- Re: [v4tov6transition] IPv6 VPNs configured over … Templin, Fred L
- Re: [v4tov6transition] [Softwires] IPv6 VPNs conf… Templin, Fred L
- Re: [v4tov6transition] [Softwires] IPv6 VPNs conf… Brian E Carpenter
- Re: [v4tov6transition] [Softwires] IPv6 VPNs conf… Templin, Fred L
- Re: [v4tov6transition] IPv6 VPNs configured over … Washam Fan
- Re: [v4tov6transition] IPv6 VPNs configured over … Templin, Fred L
- Re: [v4tov6transition] IPv6 VPNs configured over … Washam Fan
- Re: [v4tov6transition] [Softwires] 6a44 MTU issues Rémi Després
- Re: [v4tov6transition] IPv6 VPNs configured over … Templin, Fred L
- Re: [v4tov6transition] [Softwires] 6a44 MTU issues Templin, Fred L
- Re: [v4tov6transition] [Softwires] 6a44 MTU issues Rémi Després
- Re: [v4tov6transition] [Softwires] 6a44 MTU issues Templin, Fred L
- Re: [v4tov6transition] [Softwires] 6a44 MTU issues Rémi Després
- Re: [v4tov6transition] IPv6 VPNs configured over … Washam Fan
- Re: [v4tov6transition] [Softwires] 6a44 MTU issues Templin, Fred L
- Re: [v4tov6transition] IPv6 VPNs configured over … Templin, Fred L
- Re: [v4tov6transition] IPv6 VPNs configured over … Brian E Carpenter
- Re: [v4tov6transition] IPv6 VPNs configured over … Templin, Fred L