NEC SL1100, Networking Manual

Page: 85 / 292

NEC SL1100 Issue 6.0
Networking Manual 6 - 23
6.5 Diffserv (Differentiated Service)
Differentiated Services (Diffserv) uses the ToS field in an IP header. Diffserv
is now commonly used instead of IP Precedence (refer to
6.4 IP Precedence
on page 6-22 ) as it provides greater flexibility. This method uses six bits of the
ToS field to determine the priority – which provides up to 64 possible values.
The combination of binary digits is known as the Diffserv Codepoint (DSCP).
The example below shows an Ethernet Frame containing one RTP (speech)
packet. The IP Packet has the ToS field set to 101000 (binary) which is the
equivalent of Class Selector 5. The router(s) in this network should be
programmed to prioritize based on CS5.
Table 6-5 Diffserv Parameters
6 bits 2 bits
Differentiated Services Code Point ECN
(Not QoS related)
Ethernet Frame Example - Containing One RTP (Speech) Packet