Quality of Service guidelines
322 Avaya Application Solutions IP Telephony Deployment Guide
Figure 90: Differentiated Services (DiffServ) TOS byte
A DiffServ Code Point (DSCP) of 46 (101110), referred to as expedited forwarding (EF), is
suggested for the proper treatment of voice packets. Signaling packets can also be marked with
DSCP 46 if there is sufficient bandwidth to prevent dropped packets. To assure that voice and
signaling packets are not in contention, mark signaling packets with a different DSCP value.
With Communication Manager, you can set any DSCP value needed to work with a company’s
QoS scheme.
Some common DiffServ Code Points are defined in RFCs 2474 and 2475. Although DSCPs are
specified in IETF RFCs, the treatment of packets that are tagged with DiffServ depends on
implementation.
Note that older routers might require a DSCP setting of 40 (101000), which is backward
compatible with the original TOS byte definition of critical. But again, Avaya products and
software allows users to set any of the 64 possible DSCP values to work with your voice quality
