RE: interface stats, physical problem or high utilization?
Thanks to everyone for the feedback. I think I have mustered enough evidence to change my co-worker's viewpoint. By the way, the problem was physical (telco) related. I found the problem by running debug on the service-module. After watching the router for 30 minutes, I saw the following: SERVICE_MODULE(0): detects loopback test from telco SERVICE_MODULE(0): loopback test from telco ended after duration 00:00:00 Those debug commands really come in handy. Later, Chris -Original Message- From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] Sent: Tuesday, December 26, 2000 8:38 PM To: Kane, Christopher A.; '[EMAIL PROTECTED]' Subject: Re: interface stats, physical problem or high utilization? At 09:59 AM 12/26/00, Kane, Christopher A. wrote: I'm looking for some feedback to a discussion I had with a co-worker. I'm not looking for troubleshooting assistance with this problem. Rather, I would like to know if anyone else has experienced a similar situation in which a utilization problem looks like a physical problem? Input errors, CRC errors, and carrier transitions on a WAN link seem like a physical problem, and not a utilization problem. Dropped frames would indicate a utilization problem. Since I have Ethernet on the brain, I'm wondering if your co-worker who said that high utilization can look like a physical problem was over-generalizing? On shared Ethernet, high utilization can indeed look like a physical problem. Collisions result in frames with bad CRCs. You need to do more analysis to isolate whether the CRCs are a result of high utilization or noise, cross-talk, or other physical problems. Do the CRCs only occur in runts (64 bytes), for example, which are usually the result of a collision? But on a WAN? I think high utilization versus a physical-layer problem would manifest itself differently. On the other hand, high utilization could trigger a bug in carrier or your own equipment which trashes frames, resulting in CRCs. What is your utilization, by the way? Is it high when that user is downloading large files? You said you weren't asking for troubleshooting tips, but please do let us know if you solved the problem and what the cause turned out to be. Thanks. Priscilla We had a customer with a 56k Frame ckt terminating into a Cisco 2524 with an integrated 4-wire CSU/DSU. The end user was complaining of dropping when trying to pull large files (3 meg). The interface stats showed Input errors, CRCs and carrier transitions. Myself and the telco were able to test end-to-end clean several times. We then swapped the 2524 for fear that the integrated CSU/DSU was flaky. The problem remained. Then my co-worker made a statement that I am having a hard time agreeing with. He stated that it must be heavy utilization by the end user that is causing the problem. Could that be? A utilization problem that looks like a physical problem according to the stats provided by the serial interface? It's always fun to banter with co-workers. Round-table discussions in front of the whiteboard are my favorite part of the job. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Priscilla Oppenheimer http://www.priscilla.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: interface stats, physical problem or high utilization?
Hhhm.. it was a telco problem. knock me over with a feather!! :- -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of Kane, Christopher A. Sent: Wednesday, December 27, 2000 6:22 AM To: 'Priscilla Oppenheimer'; Kane, Christopher A.; '[EMAIL PROTECTED]' Subject:RE: interface stats, physical problem or high utilization? Thanks to everyone for the feedback. I think I have mustered enough evidence to change my co-worker's viewpoint. By the way, the problem was physical (telco) related. I found the problem by running debug on the service-module. After watching the router for 30 minutes, I saw the following: SERVICE_MODULE(0): detects loopback test from telco SERVICE_MODULE(0): loopback test from telco ended after duration 00:00:00 Those debug commands really come in handy. Later, Chris -Original Message- From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] Sent: Tuesday, December 26, 2000 8:38 PM To: Kane, Christopher A.; '[EMAIL PROTECTED]' Subject: Re: interface stats, physical problem or high utilization? At 09:59 AM 12/26/00, Kane, Christopher A. wrote: I'm looking for some feedback to a discussion I had with a co-worker. I'm not looking for troubleshooting assistance with this problem. Rather, I would like to know if anyone else has experienced a similar situation in which a utilization problem looks like a physical problem? Input errors, CRC errors, and carrier transitions on a WAN link seem like a physical problem, and not a utilization problem. Dropped frames would indicate a utilization problem. Since I have Ethernet on the brain, I'm wondering if your co-worker who said that high utilization can look like a physical problem was over-generalizing? On shared Ethernet, high utilization can indeed look like a physical problem. Collisions result in frames with bad CRCs. You need to do more analysis to isolate whether the CRCs are a result of high utilization or noise, cross-talk, or other physical problems. Do the CRCs only occur in runts (64 bytes), for example, which are usually the result of a collision? But on a WAN? I think high utilization versus a physical-layer problem would manifest itself differently. On the other hand, high utilization could trigger a bug in carrier or your own equipment which trashes frames, resulting in CRCs. What is your utilization, by the way? Is it high when that user is downloading large files? You said you weren't asking for troubleshooting tips, but please do let us know if you solved the problem and what the cause turned out to be. Thanks. Priscilla We had a customer with a 56k Frame ckt terminating into a Cisco 2524 with an integrated 4-wire CSU/DSU. The end user was complaining of dropping when trying to pull large files (3 meg). The interface stats showed Input errors, CRCs and carrier transitions. Myself and the telco were able to test end-to-end clean several times. We then swapped the 2524 for fear that the integrated CSU/DSU was flaky. The problem remained. Then my co-worker made a statement that I am having a hard time agreeing with. He stated that it must be heavy utilization by the end user that is causing the problem. Could that be? A utilization problem that looks like a physical problem according to the stats provided by the serial interface? It's always fun to banter with co-workers. Round-table discussions in front of the whiteboard are my favorite part of the job. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Priscilla Oppenheimer http://www.priscilla.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: interface stats, physical problem or high utilization?
You need to look into the following things in this particular scenario: 1. The output queue drops on the serial interface and if they increase during the file transfer. 2. The queueing type configured on the interface such as WFQ, FIFO, etc. 3. The "buffers" situation in terms of their depletion. 4. The mix of applications that are being transported over the WAN link. 5. A Sniffer WAN trace may also prove helpful in this situation. 6. Observe the "5-minute traffic rate" on the serial interface during a large file transfer and see if it peaks to 56 Kbps. 7. Is something driving the interface into "process-switched mode" ? 8. You can prioritize the application that is being impacted the most by using any of the queueing mechanisms. However, this decision may have some adverse effects if not properly researched. Here I am assuming that the frame PVC has been provisioned correctly and that it is delivering as per the rated CIR/EIR. This was just to trigger your thought-process as you have not provided enough information to be able to correctly pin-point the cause. Aziz S. Islam -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Kane, Christopher A. Sent: Tuesday, December 26, 2000 9:59 AM To: '[EMAIL PROTECTED]' Subject: interface stats, physical problem or high utilization? I'm looking for some feedback to a discussion I had with a co-worker. I'm not looking for troubleshooting assistance with this problem. Rather, I would like to know if anyone else has experienced a similar situation in which a utilization problem looks like a physical problem? We had a customer with a 56k Frame ckt terminating into a Cisco 2524 with an integrated 4-wire CSU/DSU. The end user was complaining of dropping when trying to pull large files (3 meg). The interface stats showed Input errors, CRCs and carrier transitions. Myself and the telco were able to test end-to-end clean several times. We then swapped the 2524 for fear that the integrated CSU/DSU was flaky. The problem remained. Then my co-worker made a statement that I am having a hard time agreeing with. He stated that it must be heavy utilization by the end user that is causing the problem. Could that be? A utilization problem that looks like a physical problem according to the stats provided by the serial interface? It's always fun to banter with co-workers. Round-table discussions in front of the whiteboard are my favorite part of the job. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: interface stats, physical problem or high utilization?
You need to look into the following things in this particular scenario: 1. The output queue drops on the serial interface and if they increase during the file transfer. 2. The queueing type configured on the interface such as WFQ, FIFO, etc. 3. The "buffers" situation in terms of their depletion. 4. The mix of applications that are being transported over the WAN link. 5. A Sniffer WAN trace may also prove helpful in this situation. 6. Observe the "5-minute traffic rate" on the serial interface during a large file transfer and see if it peaks to 56 Kbps. 7. Is something driving the interface into "process-switched mode" ? 8. You can prioritize the application that is being impacted the most by using any of the queueing mechanisms. However, this decision may have some adverse effects if not properly researched. Here I am assuming that the frame PVC has been provisioned correctly and that it is delivering as per the rated CIR/EIR. This was just to trigger your thought-process as you have not provided enough information to be able to correctly pin-point the cause. Aziz S. Islam -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Kane, Christopher A. Sent: Tuesday, December 26, 2000 9:59 AM To: '[EMAIL PROTECTED]' Subject: interface stats, physical problem or high utilization? I'm looking for some feedback to a discussion I had with a co-worker. I'm not looking for troubleshooting assistance with this problem. Rather, I would like to know if anyone else has experienced a similar situation in which a utilization problem looks like a physical problem? We had a customer with a 56k Frame ckt terminating into a Cisco 2524 with an integrated 4-wire CSU/DSU. The end user was complaining of dropping when trying to pull large files (3 meg). The interface stats showed Input errors, CRCs and carrier transitions. Myself and the telco were able to test end-to-end clean several times. We then swapped the 2524 for fear that the integrated CSU/DSU was flaky. The problem remained. Then my co-worker made a statement that I am having a hard time agreeing with. He stated that it must be heavy utilization by the end user that is causing the problem. Could that be? A utilization problem that looks like a physical problem according to the stats provided by the serial interface? It's always fun to banter with co-workers. Round-table discussions in front of the whiteboard are my favorite part of the job. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: interface stats, physical problem or high utilization?
At 09:59 AM 12/26/00, Kane, Christopher A. wrote: I'm looking for some feedback to a discussion I had with a co-worker. I'm not looking for troubleshooting assistance with this problem. Rather, I would like to know if anyone else has experienced a similar situation in which a utilization problem looks like a physical problem? Input errors, CRC errors, and carrier transitions on a WAN link seem like a physical problem, and not a utilization problem. Dropped frames would indicate a utilization problem. Since I have Ethernet on the brain, I'm wondering if your co-worker who said that high utilization can look like a physical problem was over-generalizing? On shared Ethernet, high utilization can indeed look like a physical problem. Collisions result in frames with bad CRCs. You need to do more analysis to isolate whether the CRCs are a result of high utilization or noise, cross-talk, or other physical problems. Do the CRCs only occur in runts (64 bytes), for example, which are usually the result of a collision? But on a WAN? I think high utilization versus a physical-layer problem would manifest itself differently. On the other hand, high utilization could trigger a bug in carrier or your own equipment which trashes frames, resulting in CRCs. What is your utilization, by the way? Is it high when that user is downloading large files? You said you weren't asking for troubleshooting tips, but please do let us know if you solved the problem and what the cause turned out to be. Thanks. Priscilla We had a customer with a 56k Frame ckt terminating into a Cisco 2524 with an integrated 4-wire CSU/DSU. The end user was complaining of dropping when trying to pull large files (3 meg). The interface stats showed Input errors, CRCs and carrier transitions. Myself and the telco were able to test end-to-end clean several times. We then swapped the 2524 for fear that the integrated CSU/DSU was flaky. The problem remained. Then my co-worker made a statement that I am having a hard time agreeing with. He stated that it must be heavy utilization by the end user that is causing the problem. Could that be? A utilization problem that looks like a physical problem according to the stats provided by the serial interface? It's always fun to banter with co-workers. Round-table discussions in front of the whiteboard are my favorite part of the job. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Priscilla Oppenheimer http://www.priscilla.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
