On Thu, 7 Oct 1999 01:41:02 +0100,
Steve Dodd <[EMAIL PROTECTED]> wrote:
>The pattern I've noticed so far seems to be that whenever the sending host
>queues multiple segments in quick succession, the remote host only ever sees
>the first:
>
>We see:
>
>00:33:46.748313 loth.1131 > moria-eth.1883: P 1:1449(1448) ack 1 win 32120
><nop,nop,timestamp 1020677 71896360> (DF)
>00:33:46.749684 loth.1131 > moria-eth.1883: P 1449:2897(1448) ack 1 win 32120
><nop,nop,timestamp 1020677 71896360> (DF)
>00:33:47.366914 moria-eth.1883 > loth.1131: . ack 1449 win 31856 <nop,nop,timestamp
>71896444 1020677> (DF) [tos 0x10]
>
>The remote sees:
>
>00:33:58.678060 loth.1131 > moria-eth.1883: P 1:1449(1448) ack 1 win 32120
><nop,nop,timestamp 1020677 71896360> (DF)
>00:33:58.678334 moria-eth.1883 > loth.1131: . ack 1449 win 31856 <nop,nop,timestamp
>71896444 1020677> (DF) [tos 0x10]
>
>and again, later, we see:
>
>00:33:47.367056 loth.1131 > moria-eth.1883: P 2897:4345(1448) ack 1 win 32120
><nop,nop,timestamp 1020739 71896444> (DF)
>00:33:47.367574 loth.1131 > moria-eth.1883: P 4345:5793(1448) ack 1 win 32120
><nop,nop,timestamp 1020739 71896444> (DF)
>00:33:47.936948 moria-eth.1883 > loth.1131: . ack 1449 win 31856 <nop,nop,timestamp
>71896502 1020677> (DF) [tos 0x10]
>
>but the remote only sees:
>
>00:33:59.249165 loth.1131 > moria-eth.1883: P 2897:4345(1448) ack 1 win 32120
><nop,nop,timestamp 1020739 71896444> (DF)
>00:33:59.249450 moria-eth.1883 > loth.1131: . ack 1449 win 31856 <nop,nop,timestamp
>71896502 1020677> (DF) [tos 0x10]
Just a normal lost packet. The packet 1449:2897 was lost, the sender
transmitted more packets, the receiver replied that it had only seen to
the end of packet 1448. Eventually the sender realizes a packet has
been lost and should retransmit it, standard TCP recovery for lost
packets.
Now if the sender never retransmits 1449:2897 then there is a bug in
the Linux TCP code (very unlikely). If the sender retransmits
1449:2897 but the receiver never sees it, suspect the PPP link, in
particular I would suspect header compression. Do you get the same
problems without ppp compression (-ac -vj -pc in pppd startup)?
ps. cc: trimmed, l-k removed.
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