When SIP phones on an ADSL or DSL line have problems maintain a connection to an Asterisk server it is important to perform a packet capture on the server. This may show that dropped packets or incorrectly sequenced packets are being seen. This fragmentation can be caused by the ADSL or DSL connection. By reducing the MTU size on the asterisk server or the router packets may be sized where the fragmentation level is acceptable.
It is important to note that if the MTU size is reduced on the asterisk server all connections will be affected by this. Where possible only reduce the MTU size on the route to the network that is having the problems.
An MTU size of 1400 will usually help with the fragmentation.
Article ID: 9, Created On: 1/18/2009, Modified: 6/16/2009