Throughput
Value Description
0 Normal Throughput
1 High Throughput
Reliability
Value Description
0 Normal Reliability
1 High Reliability
Delay
Value Description
0 Normal Delay
1 Low Delay
Cost
Value Description
0 Normal Cost
1 Low Cost
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 IP Precedence on page 6-15) 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).
Table 6-4 Diffserv Parameters
6 bits 2 bits
Differentiated Services Code Point ECN (Not QoS related)
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.
Ethernet Frame Example - Containing One RTP (Speech) Packet
Source Destination Protocol
172.16.0.21 172.16.0.101 RTP
Info
Payload type=ITU-T G.729, SSRC=732771006, Seq=30885, Time=20560
Frame 159 (65 bytes on wire, 65 bytes captured)
Arrival Time: Jan 18, 2005 13:55:44.834497000
Time delta from previous packet: 0.000445000 seconds
Time since reference or first frame: 2.901831000 seconds
Frame Number: 159
Packet Length: 65 bytes
Capture Length: 65 bytes
Ethernet II, Src: 00:60:b9:c1:ab:a3, Dst: 00:60:b9:c6:6e:45
Destination: 00:60:b9:c6:6e:45 (Nitsuko_c6:6e:45)
Source: 00:60:b9:c1:ab:a3 (Nitsuko_c1:ab:a3)
SL2100
ISSUE 1.0
6-16
Network Design Considerations
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