Admin Network Technologies

The IT Detective Agency: WebEx and the case of the mysterious reset

A company known to me was a contented user of WebEx until they noticed a strange behaviour: their calls were losing quality or even dropped exactly after one hour. No one, most especially the vendor of WebEx, had the slightest idea of the root cause. Read on to see how this fascinating case is playing out.

Scene: company offices, Sao Paolo, Brazil
Triago, a very competent IT professional located in Sao Paolo was the first to report the problem. More-or-less it went like this:

– when he uses the call-my-computer feature in WebEx the call quality is fine, until he has been on the meeting for one hour. At the one hour mark the voice quality of others (from his perspective) dropped dramatically. Sometimes the call was completely lost. Then, about five minutes later, the quality was OK again.
– the problem only occurred when in the office or using VPN, i.e., when using the company network
– others in South America are having the same issue
– he can use the same company laptop, on the Internet, and will not have the problem

After the usual finger-pointing amongst various vendors a debugging plan was created.

It’s going really well. There have been about 12 test calls, stretched out over the last five months. You have to admire the chutzpah of US software vendors who sell to major customers and then still manage to treat them like crap come time for support.

The pattern, more-or-less, goes like this. test call with several vendors plus Triago and I in the US. Wait around for an hour, produce the problem. Wait for software vendor to “analyze”. Wait for two weeks. Some small insight may be gleaned by them. Conclusion: another test is needed, we didn’t have all the traces we need. rinse and repeat.

Scene: A soulless office park somewhere in northern New Jersey
To be continued, literally…

Scene: an enterprise-class server room somewhere in Research triangle Park, North Carolina
If one uses the company’s guest WiFi, one uses the company’s firewall, but not the company’s proxy server. This test succeeds. But, unfortunately, one also uses UDP rather than TCP for the communication because that is the default. See the references for communication requirements.

So one thought is to knock out the ability to use UDP by blocking UDP port 9000, thereby forcing use of TCP. Testing that today….

References and related
Networking requirements for WebEx: