Comment 12 for bug 380091

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BrainwreckedTech (paulhinchberger3+ubuntulaunchpad) wrote : Re: Ubuntu 9.04 Ekiga 3.2.0 Default config gives oversized UDP packets

Alvin

We seem to be having two different problems.

Mine was due to the local machine's MTU setting and was fixed when the MTU was brought down to 1500. My specific issue here was that Ekiga could very well work with the local machine's MTU set to 7000 as it's called *Maximum* Transmission Unit not *Only* Transmission Unit. As evidenced in my test cases, a computer can receive packets smaller than its MTU setting with no problem. That's why conversation went one way in one of my test cases - Ekiga was receiving 1500-byte (or smaller) packets but sending out 7000-byte packets and the packets where being dropped (too large) once they hit the public Internet.

However, you seem to be saying that no matter what you do, you can't get the Ekiga Echo Test to work. Please reply and verify:

* that your MTU setting is 1500 in the output that ifconfig gives you. Look for the MTU in the 4th line.

  Example:
     eth0 Link encap:Ethernet HWaddr 00:17:31:3b:d0:ee
               inet addr:192.168.1.101 Bcast:192.168.1.255 Mask:255.255.255.0
               inet6 addr: fe80::217:31ff:fe3b:d0ee/64 Scope:Link
               UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

* that you still can't connection when the only codec you tell Ekiga to use is GSM

When I got this working, I swear this was the protocol Ekiga said it was using. I have to go by memory on this one, because it seems that the Ekiga registration server is down at the moment. (Both my desktop and netbook fail Ekiga registration with "MonSock UDP Port on remote not ready." in the debug output.)

* try an MTU of 1400.

While 1500 is the standard, some hops on the net are less. If your ISP is one of those hops, you'll never get 1500-byte UDP packets out to the Internet.

From http://kb.netgear.com/app/answers/detail/a_id/1153 :

# 1500. The largest Ethernet packet size; it is also the default value. This is the typical setting for non-PPPoE, non-VPN connections.
# 1492. The size PPPoE prefers.
# 1472. Maximum size to use for pinging. (Bigger packets are fragmented.)
# 1468. The size DHCP prefers.
# 1460. Usable by AOL if you don't have large email attachments, etc.
# 1430. The size VPN and PPTP prefer.
# 1400. Maximum size for AOL DSL.

If you still can't connect, I think this might be another bug and it'd be best to file another one for it.