QoS and DLSw+ 535
NOTE
The IETF has created a working group to define "An Architecture for Differentiated Service"
(RFC 2475). This IETF work is defining the use of IP Precedence to deliver scalable,
differentiated services across the Internet.
Table 14-2 shows the values of the IP Precedence bits and their corresponding definitions. Cisco
routers use only bits 0 through 5. Bits 6 and 7 are not used.
How TCP Ports Map to DLSw
Table 14-3 lists DLSw+ priority queues and IP Precedence default mapping. Notice that TCP
port 2065 maps directly to the High queue, which is equivalent to the Critical value or Bit 5 in
the IP Precedence field.
When the priority keyword option is used on the dlsw remote-peer command, DLSw
automatically does the following things:
·
Activates the four TCP ports to the remote peer
·
Sets IP Precedence values
·
Assigns traffic to the specific ports according to the extended access list
Table 14-2
IP Precedence Bits and Their Corresponding Definitions
Value
Definition
Network
Matches packets with network-control precedence (7)
Internet
Matches packets with internetwork-control precedence (6)
Critical
Matches packets with critical precedence (5)
Flash-Override
Matches packets with flash-override precedence (4)
Flash
Matches packets with flash precedence (3)
Immediate
Matches packets with immediate precedence (2)
Priority
Matches packets with priority precedence (1)
Routine
Matches packets with routine precedence (0)
Table 14-3
DLSw+ Priority Queues and IP Precedence Default Mapping
TCP Port
DLSw+ Priority Queue
IP Precedence
IP Precedence Value
2065
High
Critical
5
1981
Medium
Flash override
4
1982
Normal
Flash
3
1983
Low
Immediate
2
87200333.book Page 535 Wednesday, August 22, 2001 1:41 PM