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Groups > comp.os.linux.networking > #278

Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised

From Mark Hobley <markhobley@yahoo.donottypethisbit.co>
Newsgroups comp.os.linux.networking, comp.protocols.tcp-ip
Subject Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised
Date 2011-05-21 20:20 +0000
Organization A noiseless patient Spider
Message-ID <ir96q3$565$1@dont-email.me> (permalink)
References <ir8jui$l3k$1@dont-email.me>

Cross-posted to 2 groups.

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On Sat, 21 May 2011 14:58:32 +0000, Mark Hobley wrote:

> 18: Flags [S.], seq 3385954279, ack 3902988975, win 5792, options [mss
> 1380,sackOK,TS val 140346418 ecr 47079743,nop,wscale 7], length 0

I'm not sure what this first line is, but win 5792 is bigger than any
datagram that my ISP can carry.

> 03:40:48.745614 IP venus.markhobley.yi.org.52196 >
> news.eternal-september.org.nntp: Flags [S], seq 185692436, win 14600,
> options [mss 1460,sackOK,TS val 47088682 ecr 0,nop,wscale 5], length 0

The value of win 14600 here is presumably the number of bytes of data that
venus is prepared to receive in a single instance. Is that right? Presumably
that is just data, and excludes headers. Is that right? It is bigger than
any datagram that my ISP can carry. Does it have any effect on datagram
sizes?

> news.eternal-september.org.nntp > venus.markhobley.yi.org.52196: Flags
> [S.], seq 3936843225, ack 185692437, win 5792, options [mss
> 1380,sackOK,TS val 140355273 ecr 47088682,nop,wscale 7], length 0

Here I receive a window size. Presumably, that is the size that the remote
host at eternal-september is prepared to accept. Again, I would never be
able to deliver that many bytes in a single datagram.

> 03:41:21.453043 IP news.eternal-september.org.nntp >
> venus.markhobley.yi.org.52197: Flags [S.], seq 156904658, ack 693658576,
> win 5792, options [mss 1380,sackOK,TS val 140363421 ecr
> 47096829,nop,wscale 7], length 0 03:41:21.453127 IP

Here is another big window. I don't know whether that means anything.

> 03:41:54.123370 IP venus.markhobley.yi.org.52198 >
> news.eternal-september.org.nntp: Flags [S], seq 1215827121, win 14600,
> options [mss 1460,sackOK,TS val 47105026 ecr 0,nop,wscale 5], length 0

Another big window.

> news.eternal-september.org.nntp: Flags [S], seq 1725633662, win 14600,
> options [mss 1460,sackOK,TS val 47113211 ecr 0,nop,wscale 5], length 0

and another

> 03:42:26.982276 IP news.eternal-september.org.nntp >
> venus.markhobley.yi.org.52199: Flags [S.], seq 1178329563, ack
> 1725633663, win 5792, options [mss 1380,sackOK,TS val 140379803 ecr
> 47113211,nop,wscale 7], length 0 03:42:26.982362 IP
> 03:42:50.439130 IP news.eternal-september.org.nntp >
> venus.markhobley.yi.org.51218: Flags [R], seq 4178125634, win 0, length
> 0

Hmmm, a window of zero here. Presumably, the remote is busy.

> 03:42:59.663041 IP venus.markhobley.yi.org.52200 >
> news.eternal-september.org.nntp: Flags [S], seq 2233139354, win 14600,
> options [mss 1460,sackOK,TS val 47121411 ecr 0,nop,wscale 5], length 0

A big window.

> 03:42:59.770427 IP news.eternal-september.org.nntp >
> venus.markhobley.yi.org.52200: Flags [S.], seq 1693600159, ack
> 2233139355, win 5792, options [mss 1380,sackOK,TS val 140388003 ecr
> 47121411,nop,wscale 7], length 0 03:42:59.770510 IP

And another

03:43:04.320740 IP venus.markhobley.yi.org.52201 >
> news.eternal-september.org.nntp: Flags [S], seq 2304145392, win 14600,
> options [mss 1460,sackOK,TS val 47122576 ecr 0,nop,wscale 5], length 0

A big window again. Hey look at the mss value! That looks big to me.
My ISP cannot carry a datagram above 1412 bytes.

> 03:43:04.500693 IP news.eternal-september.org.nntp >
> venus.markhobley.yi.org.52201: Flags [S.], seq 1766167236, ack
> 2304145393, win 5792, options [mss 1380,sackOK,TS val 140389170 ecr
> 47122576,nop,wscale 7], length 0

A big window.

> 03:43:11.752242 IP news.eternal-september.org.nntp >
> venus.markhobley.yi.org.52202: Flags [S.], seq 1875583976, ack
> 2424765078, win 5792, options [mss 1380,sackOK,TS val 140390973 ecr
> 47124291,nop,wscale 7], length 0

Another big window

> 03:43:14.812402 IP venus.markhobley.yi.org.52203 >
> news.eternal-september.org.nntp: Flags [S], seq 2475930012, win 14600,
> options [mss 1460,sackOK,TS val 47125199 ecr 0,nop,wscale 5], length 0

There is that big maximum segment size again!

Mark.

-- 
Mark Hobley
Linux User: #370818  http://markhobley.yi.org/

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Thread

Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-21 14:58 +0000
  Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised "David W. Hodgins" <dwhodgins@nomail.afraid.org> - 2011-05-21 15:16 -0400
    Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-05-21 22:02 +0000
      Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Tauno Voipio <tauno.voipio@notused.fi.invalid> - 2011-05-22 19:59 +0300
        Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-22 17:09 +0000
  Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-21 20:20 +0000
    Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Richard Kettlewell <rjk@greenend.org.uk> - 2011-05-21 22:47 +0100
    Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-05-21 22:28 +0000
      Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-22 01:15 +0000
        Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-05-22 06:01 +0000
          Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-22 07:28 +0000
            Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Andy Furniss <spam@andyfurniss.entadsl.com> - 2011-05-22 11:40 +0100
              Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-22 12:25 +0000
                Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Andy Furniss <spam@andyfurniss.entadsl.com> - 2011-05-22 20:40 +0100
                Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Andy Furniss <spam@andyfurniss.entadsl.com> - 2011-05-22 20:56 +0100
                Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-22 22:57 +0000
                Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-22 23:12 +0000
            Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-05-22 11:31 +0000
              Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-22 11:50 +0000
                Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-05-22 12:52 +0000
                Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-22 13:27 +0000
                Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-05-22 19:19 +0000
                Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-22 22:12 +0000
                Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-25 15:55 +0000
                ip route - Wrong Maximum Segment Size being advertised Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-25 17:27 +0000
                Re: Linux 2.6.39.1 - Wrong Maximum Segment Size in both directions Mark Hobley <markhobley@yahoo.donottypethisbit.co> - 2011-05-29 00:34 +0000
                Re: Linux 2.6.39.1 - Wrong Maximum Segment Size in both directions Andy Furniss <spam@andyfurniss.entadsl.com> - 2011-05-29 11:11 +0100
                Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Martijn Lievaart <m@rtij.nl.invlalid> - 2011-05-23 08:13 +0200
    Re: Linux 2.6.39-rc7 - Wrong Maximum Segment Size being advertised Barry Margolin <barmar@alum.mit.edu> - 2011-05-22 00:44 -0400

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