Wireshark mailing list archives
Re: FCIP issues with SAN replication
From: Bill Meier <wmeier () newsguy com>
Date: Tue, 29 Jun 2010 12:08:12 -0400
Chandler, Mel wrote:
Greetings all, <snip> Now the problem, although we have one gigabit of bandwidth, they'll only use about 13Mbps of it each, we've verified this with iperf. Each connection we'll only take 13Mbps of bandwidth, parallel tests show each connection gets 13Mbps of bandwidth. The HP engineer told us that at5Mbps we get approximately 1.3Mbps of actually data, which means thatFCIP has 80% over head? Can that be right? The big huge problem is that after running for several hours they'll eventually just die and have to rebooted to start replicating again. They're already on the latest firmware (2.4.4.1). The only error we get from the statistic screen of the MPX's says they're getting TCP timeouts. I've performed captures on both sides' MPXs' and the errors I see in a 60 sec sample are FCP malformed packets (~4300), duplicate ACK's (~41), previous segment lost (~3), fast retransmission (~3). When HP was questioned about the FCP malformed packets they stated that they use a proprietary protocol and that wireshark wouldn't be able to decode it. I've since searched for this protocol but can find no references to it anywhere. The other errors seem so minor and few it would be hard to believe that they're impacting the data stream that much if at all. I'll include a small sample of the captures, if it lets me.
Taking a quick look at one of the captures (SNA) (and if I haven't missed anything) I see the following. The rate appears to be limited because of the "TCP window size" being used and the TCP "acknowledge time" for the connection. 1. It appears that the "ack time" is about 35 millisecs (interval between when a frame is sent and when an ack is received). 2. The 'TCP window size is 32768 bytes). If we assume "infinitely fast" transmission then the pattern is essentially: - send 32K bytes; - wait 35 ms for the acks (and so on) So: ~ 1/.035sec * 32KBytes can be sent per second which is ~ 8Mbits per/sec If my analysis is correct I suggest you may want to consult with ?? about the configuration of the TCP connection. You can see the pattern in the SNA capture by: 1. Filter on the TCP/FC connection (Statistics ! Conversations ! TCP) 2. Select the first frame 3. Do Statistics ! TCP Stream Graph ! Tine sequence Graph (tcptrace). ___________________________________________________________________________ Sent via: Wireshark-users mailing list <wireshark-users () wireshark org> Archives: http://www.wireshark.org/lists/wireshark-users Unsubscribe: https://wireshark.org/mailman/options/wireshark-users mailto:wireshark-users-request () wireshark org?subject=unsubscribe
Current thread:
- FCIP issues with SAN replication Chandler, Mel (Jun 29)
- Re: FCIP issues with SAN replication Gerald Combs (Jun 29)
- Re: FCIP issues with SAN replication Bill Meier (Jun 29)
- Re: FCIP issues with SAN replication Martin Visser (Jun 29)