DeVoe, Charles (PKI) wrote: > > I have several users who are trying to run an application and > often have > problems. In using a sniffer on the packets I have found that > some of the > packets are experiencing long ack times. How does one > troubleshoot this > sort of problem?
Gather the following info: 1. Do you see the Long ACK Time symptom on your Sniffer even when the users aren't complaining? The Sniffer threshold could be set too low. (Is this a Sniffer "symptom" or "diagnosis" by the way? Sniffer symptoms are sometimes misleading noise, sorry to say.) 2. Find out which side of the conversation is slow in sending the ACKs, the client or server. (Also, find out if this Sniffer symptom may just be for the server side. I think I remember that it only concerns itself with the server side.) 3. What is your topology? What internetworking equipment is between the users and the resources they are trying to reach? What errors to these devices report? Gather statistics from the devices, including reliability, load, errors, collisions if it's Ethernet, dropped packets, buffer exhaustion, etc. 4. Assuming you were sniffing near the user when you saw this symptom, incrementally move the Sniffer hop-by-hop until you're on the server's LAN. If the symptom disappears at some point, then you have an idea where the congestion is, one hop back from the hop where the problem disappears. 5. If you still see the Long ACK Time on the server's LAN, then call the server dudes in. Tell them you have proof that the server is slow. Harrass them 'til they fix the problem. :-) 6. Depending on the OS of the server, there are probably quite a few tools you could use at the server, if you ARE "the server dude." Check CPU, memory, and disk usage; caching behavior; thrashing behavior; etc. 7. If the Long ACK problem doesn't occur on the LAN that the server is on but does occur closer to the client, then you can't blame the server dudes. You have to blame the network engineers. You may have to point the finger at yourself, unfortunatley. Go back to step 3 where you analyze internetworking device statistics. Could there be a congested shared Ethernet network somewhere. Could there be an Ethernet duplex mismach problem? Are WANs invovled? Are they congested or experiencing errors? Oh, one more thing, buy a copy of Troubleshooting Campus Networks! :-) _______________________________ Priscilla Oppenheimer www.troubleshootingnetworks.com www.priscilla.com > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=62909&t=62867 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
