Bizarre Slow Response Problem

[phinphan]

Bizarre Slow Response Problem FIXED

I am helping a friend with a small system. Pure voip system using Walmart Special. 2 Grandstream GXP2000 phones. D-Link DIR655 Router. All these components are known to work with PBXIAF. When a call comes in from vitelity direct to an extension or ring group, the system waits about 15 or twenty seconds before doing anything (although it appears to be ringing from the calling side). If you hang up, the phone continues to ring for 30 seconds or so. Actions are not reflected in the CLI in a timely manner.

I have changed out the computer, changed out the phones, disabled all qos on the router, Put the pbx in the dmz, disabled-iptables, etc. One weird thing I noticed was that ping times from the pbx to the phones were on the order of 10-12 ms. Usually they would be on the order of 1-2 ms. Could that be a bad router? Internal calls suffer from the same problems so I dont think it is a vitelity issue.

From other pc's the internet and connectivity works just fine.

Has anyone come across this before or can you give me any troubleshooting ideas.

 

[jmullinix]

My suggestion requires an explanation of the difference between UDP traffic and TCP traffic.

TCP traffic does error correction. If a packet gets lost or mangled in transit, it is resent. UDP is best efforts delivery. If a packet gets lost or mangled, it is just lost forever.

I have discovered that inexpensive SOHO routers will stop routing UDP traffic when one of the interfaces is starting to fail. The TCP (like Web and email) will continue to pass because of the error correction, but enough of the UDP (like VOIP) packets are lost and causes VOIP channel failures.

For some reason the Linksys BEFSR series of SOHO routers seem to be prone to this.

 

[phinphan]

John - thanks for the suggestion. A new router is a relatively easy suggestion. I will give it a try. The routers status page does not seem to indicate any errors, however.

 

[wardmundy]

TCP traffic does error correction. If a packet gets lost or mangled in transit, it is resent. UDP is best efforts delivery. If a packet gets lost or mangled, it is just lost forever.

I have discovered that inexpensive SOHO routers will stop routing UDP traffic when one of the interfaces is starting to fail. The TCP (like Web and email) will continue to pass because of the error correction, but enough of the UDP (like VOIP) packets are lost and causes VOIP channel failures.

Good to learn something every day. Thanks, John!

 

[phinphan]

Thanks to John for the suggestion. The router change did the trick. Works great now.

 

[jmullinix]

Glad that worked. Have a great weekend.