Re: [RRG] Re: [RAM] Tunneling overheads and fragmentation
Dino Farinacci <dino@cisco.com> Tue, 11 September 2007 21:53 UTC
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From: Dino Farinacci <dino@cisco.com>
Subject: Re: [RRG] Re: [RAM] Tunneling overheads and fragmentation
Date: Tue, 11 Sep 2007 14:53:50 -0700
To: Dino Farinacci <dino@cisco.com>
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Cc: Robin Whittle <rw@firstpr.com.au>, RAM Mailing List <ram@iab.org>
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>> Granted, this is a fairly old box in a small network, but I don't >> see anyone seriously claiming that ALL ISP networks support >> packets larger than 1500 bytes on ALL their internal links (and >> also on inter-ISP links). > > I did a survey about a month ago and it is true. I will yield to > those folks who responded to me to protect their privacy. ;-) > > But the main gist was: > > o We are going to 9K MTUs on all our internal links. > o Where we don't have 9K MTUs, we use 4470. > o Virtually no one runs ISP links at 1500. And hence why I put this paragraph (the second one below) in section 5 of draft-farinacci-lisp-03.txt to reflect Brian Carpenter's comment on the subject: ----- Since additional tunnel headers are prepended, the packet becomes larger and in theory can exceed the MTU of any link traversed from the ITR to the ETR. It is recommended, in IPv4 that packets do not get fragmented as they are encapsulated by the ITR. Instead, the packet is dropped and an ICMP Too Big message is returned to the source. In practice, this is not really a problem. Hosts typically do not originate IP packets larger than 1500 bytes. And second, a survey has been taken (from a list of ISPs, see Acknowledgement section) where nearly all ISP link MTUs are either 4470 bytes or support Ethernet jumbo frames of 9000 bytes. Therefore, we don't anticipate any problems with prepending additional headers. ----- Dino _______________________________________________ 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