Quality of Service guidelines
*0.01 second (10 ms)/8 bits/byte = 480 bytes. As the circuit size diminishes, however, care should be taken to never reduce the MTU below 200 bytes. Below that size, telephony signaling and bearer (voice) packets can also be fragmented, which reduces the link efficiency and degrades voice performance.
LFI
Link Fragmentation and Interleaving (LFI) is an enhancement to Multilink PPP (MLP) that fragments packets at the Layer 2 (PPP) level. Fragmenting at the IP layer, as with MTU reduction, forces the addition of a new
Avaya recommends use of LFI functionality instead of MTU manipulation when transmitting IP Telephony packets over PPP links. As with MTU, Avaya recommends sizing packets so that the serialization delay is approximately 10 ms or less.
FRF.12
FRF.12 is a Frame Relay standard for fragmentation. It works for Frame Relay in the same way that LFI works for PPP, with similar increases in efficiency over MTU manipulation. When implementing a Frame Relay network, Avaya recommends using FRF.12 for fragmentation, and sizing the fragments so the serialization delay is no more than 10 ms.
RTP
RTP header compression is a mechanism that reduces the protocol overhead that is associated with IP Telephony audio packets. It is a function of the network, and not a function of the IP Telephony application. Along with the benefits of using RTP header compression, there are also cautions.
Application perspective
Table 56: Anatomy of
