nanog mailing list archives
Re: [NANOG] Microsoft.com PMTUD black hole?
From: Iljitsch van Beijnum <iljitsch () muada com>
Date: Wed, 7 May 2008 07:22:21 +0200
On 6 mei 2008, at 23:48, Valdis.Kletnieks () vt edu wrote:
A more common approach is to rewrite the MSS option in all TCP SYNs with a smaller value so there won't be TCP segments large enough to trigger the problem. AFAIK, all boxes that do PPPoE do this.
And just the other day, you were saying:
Very few people out there use an MTU significantly below 1500 bytes. A 1500-byte MTU will give you an _average_ packet size of ~1000 on long- lived TCP flows because there is one tiny ACK for every two full size data segments.
Right. Why is that noteworthy? I have a lot more to say about MTU issues in this draft about negotating MTUs between two hosts/routers on a subnet so jumboframes can be deployed without manual configuration: http://www.ietf.org/internet-drafts/draft-van-beijnum-multi-mtu-02.txt
Apparently, there's a *reason* why RFC1122, section 3.3.3 says:
It is generally desirable to avoid local fragmentation and to choose EMTU_S low enough to avoid fragmentation in any gateway along the path. In the absence of actual knowledge of the minimum MTU along the path, the IP layer SHOULD use EMTU_S <= 576 whenever the destination address is not on a connected network, and otherwise use the connected network's MTU.
Tell it to Microsoft and their ICMP-filtering friends... _______________________________________________ NANOG mailing list NANOG () nanog org http://mailman.nanog.org/mailman/listinfo/nanog
Current thread:
- Re: [NANOG] Microsoft.com PMTUD black hole?, (continued)
- Re: [NANOG] Microsoft.com PMTUD black hole? Brandon Butterworth (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Iljitsch van Beijnum (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Nathan Anderson/FSR (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Nathan Anderson/FSR (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Iljitsch van Beijnum (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Nathan Anderson/FSR (May 07)
- Message not available
- Re: [NANOG] Microsoft.com PMTUD black hole? Nathan Anderson/FSR (May 07)
- Re: [NANOG] Microsoft.com PMTUD black hole? Tomas L. Byrnes (May 07)
- Re: [NANOG] Microsoft.com PMTUD black hole? Nathan Anderson/FSR (May 07)
- Re: [NANOG] Microsoft.com PMTUD black hole? Matthew Petach (May 12)
- Re: [NANOG] Microsoft.com PMTUD black hole? Iljitsch van Beijnum (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Brandon Butterworth (May 06)
- Message not available
- Re: [NANOG] Microsoft.com PMTUD black hole? Iljitsch van Beijnum (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Bjørn Mork (May 07)
- Re: [NANOG] Microsoft.com PMTUD black hole? Tomas L. Byrnes (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Marshall Eubanks (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Nathan Anderson/FSR (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Nathan Anderson/FSR (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Randy Bush (May 06)
- Re: [NANOG] Microsoft.com PMTUD black hole? Glen Turner (May 07)
- Re: [NANOG] Microsoft.com PMTUD black hole? Patrick Giagnocavo (May 07)