US Technical Tips

022: MPPC Compression

12th September 2003

Product: IP Office Version: 1.3(x) and 1.4(x)


Speech ‘clipping’ issues on VoIP calls when using MPPC compression across links that have a very high traffic load.

Operating Environment

IP Office 1.3(x), and 1.4(x) software, using an IP Office Service.


‘Clipping’ of speech for any VoIP calls active on links using MPPC compression.


When a link that had negotiated and used MPPC compression becomes extremely congested the MPPC occasionally does not work correctly and may try to re-negotiate itself for the connection, unsuccessfully.

At this time it is likely to cause errors with the packets that are being transmitted across these links, which would result in data retransmissions and/or clipping of speech for any VoIP calls active on that link at the time.


We have found in the above scenarios where the link is likely to become extremely congested that MPPC compression should be turned off for that service.