Philip Lavine wrote:

Can someone explain how a TCP conversation could degenerate into congestion av oidance on a long fat pipe if there is no packet/segment loss or out of order se gments?

Here is the situation: WAN = 9 Mbps ATM connection between NY and LA (70 ms delay) LAN = Gig Ethernet Receiver: LA server = Win2k3 Sender: NY server = Linux 2.4 Data transmission typical = bursty but never more that 50% of CIR Segment sizes = 64k to 1460k but mostly less than 100k

Typical Problem Scenario: Data transmission is humming along consistently at 2 Mbps, all of a sudden transmission rates drop to nothing then pickup again afte r 15-20 seconds. Prior to the drop off (based on packet capture) there is usuall y a DUP ACK/SACK coming from the receiver followed by the Retransmits and conges tion avoidence. What is strange is there is nothing prior to the drop off that w ould be an impetus for congestion (no high BW utilization or packet loss).

Also is there any known TCP issues between linux 2.4 kernel and windows 2003 S P1? Mainly are there issues regarding the handling of SACK, DUP ACK's and Fast R etransmits.

Of course we all know that this is not a application issue since developers ma ke flawless socket code, but if it is network issue how is caused?

Duplex mismatch on an intermediate ethernet segment? -- Jay Hennigan - CCIE #7880 - Network Engineering - jay@impulse.net Impulse Internet Service - http://www.impulse.net/ Your local telephone and internet company - 805 884-6323 - WB6RDV