Wireshark-users: Re: [Wireshark-users] Need help with troubleshooting VOIP using Wireshark
Hi,
It would be helpful if you could tell us what type of PBX's these are and by
what trunk protocol they're supposed to be linked. I guess you don't know the
latter, but the PBX info shouldn't be a problem.
Thanx,
Jaap
Steven Pfister wrote:
Are there any kind of guides to troubleshooting VOIP problems (if this really is a problem that I'm seeing) using Wireshark? I'm trying to understand some strange network patterns that are going on. We have several remote sites with their own PBXes that connect to a PBX at the central site using VOIP. The VOIP setup was done before I got here, and I've so far had fairly minimal contact with it.
A lot of the remote sites seem to have a steady, 24x7 stream of udp packets coming back to the central site. For the most part, the source and destination port numbers seem to be in the 15000 to 20000 range, and I really can't see any kind of pattern to them. It's a different set of numbers each time, and I don't really see many repeats. Most of the udp packets are from the remote site to the central site, but there are occasionally similar packets from the central site to the remote site (the ones coming from the remote site outnumber the ones going the other direction, though).
While this is going on, there are some tcp packets being exchanged. Since I'm not really sure what's going on, this is hard to describe, but it looks something like:
1. remote site sends central site an ack of some previous packet at port 1720
2. a lot of udp packets come through
3. about a minute later, the central site send the remote site a keepalive, and the remote site sends one back
4. immediately after that, the central site sends the remote site an ack of the packet from step 1
5. shortly after that, after some more udp packets, an ack from the remote site to the central site of the packet in step 4 is sent
6. the cycle repeats from step 2
This going on fairly constantly, even when the sites are closed (the majority of them are public school buildings). One site, a maintenance building is sending out 5.5 to 6 gb/day.
I really hope I'm not misreading what I'm seeing in Wireshark (I'm still pretty new at it) and confusing the issue.
On the whole, everything is working fine. It's mostly that the large amount of unidentified outgoing traffic is throwing off our bandwidth reports, especially when the sites don't have their normal amount of incoming traffic to hide what's going on.
Thank you!
Steve Pfister
Technical Coordinator,
The Office of Information Technology
Dayton Public Schools
115 S. Ludlow St.
Dayton, OH 45402
Office (937) 542-3149
Cell (937) 673-6779
Direct Connect: 137*131747*8
Email spfister@xxxxxxxxxxxxx
