Avaya 555-245-600 manual DiffServ, Recommendations for end-to-end QoS

DiffServ

Recommendations for end-to-end QoS

When end-to-end QoS is desired, Avaya recommends using DiffServ, a Layer 3 CoS method. Modern routers can map DiffServ Code Points (DSCP) to 802.1p priority values, so 802.1p tags can be recreated on each Ethernet link. This functionality is supported in Avaya Layer 3 switches, and the X330 WAN module.

IEEE 802.1p states a standard according to which these bits are used for CoS. The precedence is listed in Table 54: IEEE 802.1 precedence and service mapping.

Table 54: IEEE 802.1 precedence and service mapping

User priority	Service mapping
000	Default, assumed to be best effort
001	Reserved, less than best effort
010	Reserved
011	Reserved
100	Delay sensitive, no bound
101	Delay sensitive, 100 ms bound
110	Delay sensitive, 10 ms bound
111	Network control

DiffServ

The Differentiated Services (DiffServ) prioritization scheme redefines the existing TOS byte in the IP header (Figure 90: Differentiated Services (DiffServ) TOS byte on page 322) by combining the first 6 bits into 64 possible combinations. This use of the TOS byte is still evolving, but can be used now by Communication Manager, IP Telephones, and other network elements such as routers and switches in the LAN and WAN.

Issue 6 January 2008 321