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Date: Sun, 31 Oct 1999 12:58:33 -0600 (CST)
From: Jonathan Lemon <jlemon@flugsvamp.com>
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Subject: kern/14623: packet loss on gigabit network
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>Number:         14623
>Category:       kern
>Synopsis:       packet loss on gigabit network
>Confidential:   no
>Severity:       critical
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Sun Oct 31 11:00:01 PST 1999
>Closed-Date:
>Last-Modified:
>Originator:     Jonathan Lemon
>Release:        FreeBSD 4.0-CURRENT i386
>Organization:
>Environment:

PC#1 (client) is a 450Mhz-PIII with a fxp0 card.        (Dell 410)
PC#2 (server) is a 600Mhz-PIII with an Alteon card.	(Dell 4300)

Machines are connected via a Netgear FS509 switch, with the alteon
card being plugged into the gigabit port.  PC#2 (server) also has 
an fxp0 card which can be used in lieu of the ti0 card.

All connections to the switch are full-duplex.

Both machines are running 4.0-CURRENT as of 28-oct-99.

Alteon card/driver details:

$FreeBSD: src/sys/pci/if_ti.c,v 1.24 1999/09/23 03:32:54 wpaul
ti0@pci0:12:0:  class=0x020000 card=0x000112ae chip=0x000112ae rev=0x01 hdr=0x00


>Description:

  Performing bulk data transfer between client and server results in
packets disappearing.  Further retransmits of the lost packet still
do not result in the other end receiving the packet.  More specifically,
tcpdumps taken on both machines show the following pattern:
  (note: no packets were dropped by bpf during these traces)

   Client transmits on the order of 100 packets in at full blast to
server, which acks the packets correctly.

   Server does not receive a packet that the client transmits
(never shows up on tcpdump on the server side)

   Client retransmits missing packet using exponential backoff (1, 2,
4, 8, 16, etc).  tcpdump on the client shows the packet being sent.
tcpdump on the server shows no packets being received.

   No further progress is made on the connection.

This is symmetric; it doesn't matter whether the sender is the server
or the client; it happens both ways.

  1. this only happens after a large number of packets are sent.
     (roughly between 145K to 310K bytes)
  2. this does not happen when using two fxp0 cards.
  3. other TCP sessions between the machines (e.g.: telnet) are unaffected.

tcpdump traces, full dmesg output, or other information also available.

>How-To-Repeat:

	ftp a large file (/kernel) from one machine to another in the
	given environment.

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted:


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