Hi Andrew,
For more details check the of the JunOS Documentation 'Interfaces and
Chassis, Section Class-of-Service at:
http://www.juniper.net/techpubs/software.html
Quick pointers:
First you need to know that the mapping for MPLS packets to output Queues is
done in hardware (not configurable like IP precedence mapping) and the
following table shows the EXP bits to Queue mapping
EXP
0 000
1 001 Q0
--------------
2 010
3 011 Q1
--------------
4 100
5 101 Q2
--------------
6 110
7 111 Q3
--------------
Here is an example:
Router A -- Router X -- Router Y -- Router B
0.1 0.2 0.3 0.4
Router A:
The EXP bits are set using the class-of-service knob in the LSP
configuration:
protocols {
mpls {
label-switched-path to-B-via-X {
to 192.168.0.4;
primary via-X-Y;
class-of-service 4; <<<< Set EXP bits 100 > output Q2
}
path via-X-Y {
192.168.0.2 loose;
192.168.0.3 loose;
}
interface all;
}
}
The IP TOS/Precedence bits are not changed only the ingress MPLS EXP bits
are written to 100 and MPLS packets mapped to output Q2.
Router X:
---------
class-of-service {
input {
interfaces {
so-a/a/a { <<< From router A
mpls-cos-map; <<< apply mpls map
}
}
}
}
Router y:
---------
class-of-service {
input {
interfaces {
so-x/x/x { <<< From router x
mpls-cos-map; <<< apply mpls map
}
}
}
}
The class-of-service shown, maps incoming MPLS packets to output queues, as
per the MPLS EXP bits to Queue mapping shown above. (In this case the
packets from our LSP (EXP 100) will be mapped to output Q2).
Last note - each router in the path must have the mpls-cos-map on each input
interface in the LSP path. If this is omitted (e.g. on route Y) then the
default is to map MPLS packets to output Q0 and the EXP bits are written to
000.
Hope this helps
Gary Tate
>-----Original Message-----
>From: Andrew Smith [mailto:as160@yahoo.com]
>Sent: 05 August 2001 07:03
>To: juniper-nsp@puck.nether.net
>Subject: Need help with MPLS configuration example
>
>
>Hi, all
>
>Can someone kindly point me to a config example on how
>to set the MPLS EXP field in JunOS? Is it possible to
>keep the IP prec bit and just to mark the EXP bit?
>
>Thanks a lot.
>---andrew
>
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