[j-nsp] QOS (Network Control traffic Queue)
Serge Vautour
sergevautour at yahoo.ca
Mon Mar 12 12:55:16 EDT 2012
Hello,
Folks can correct me if I'm wrong but I'll take a shot at this.
By default Junos assigns traffic generated by the RE to different queues based on the traffic type:
http://www.juniper.net/techpubs/en_US/junos10.0/information-products/topic-collections/config-guide-cos/id-10346810.html#id-10346810
It's not very clear on that page but traffic generated in Queue 3 will get proper ToS markings applied. Here's an OSPF packet capture:
me at blah> monitor traffic interface xe-0/0/0 no-resolve size 1500 detail
Address resolution is OFF.
Listening on xe-0/0/0, capture size 1500 bytes
16:04:41.745098 Out IP (tos 0xc0, ttl 1, id 21968, offset 0, flags [none], proto: OSPF (89), length: 84) 10.1.1.1 > 224.0.0.5: OSPFv2, Hello, length 48
Note the ToS value is 0xC0 = 1100 0000 -> The ToS field = 110 = 6.
There are default IP classifiers applied to all L3 interfaces. For example, here are the defaults for an MPLS interface:
me at blah> show class-of-service interface xe-0/0/0
Physical interface: xe-0/0/0, Index: 154
Queues supported: 8, Queues in use: 8
Scheduler map: <default>, Index: 2
Congestion-notification: Disabled
Logical interface: xe-0/0/0.0, Index: 2684275768
Object Name Type Index
Rewrite exp-default exp (mpls-any) 33
Classifier exp-default exp 10
Classifier ipprec-compatibility ip 13
The default IP classifier:
me at blah> show class-of-service classifier type inet-precedence name ipprec-compatibility
Classifier: ipprec-compatibility, Code point type: inet-precedence, Index: 13
Code point Forwarding class Loss priority
000 best-effort low
001 best-effort high
010 best-effort low
011 best-effort high
100 best-effort low
101 best-effort high
110 network-control low
111 network-control high
As you can see pbit 6 traffic goes to the NC queue. The default schedulers applies to the interface:
me at blah> show class-of-service scheduler-map
Scheduler map: <default>, Index: 2
Scheduler: <default-be>, Forwarding class: best-effort, Index: 21
Transmit rate: 95 percent, Rate Limit: none, Buffer size: 95 percent, Buffer Limit: none, Priority: low
Excess Priority: low
Drop profiles:
Loss priority Protocol Index Name
Low any 1 <default-drop-profile>
Medium low any 1 <default-drop-profile>
Medium high any 1 <default-drop-profile>
High any 1 <default-drop-profile>
Scheduler: <default-nc>, Forwarding class: network-control, Index: 23
Transmit rate: 5 percent, Rate Limit: none, Buffer size: 5 percent, Buffer Limit: none, Priority: low
Excess Priority: low
Drop profiles:
Loss priority Protocol Index Name
Low any 1 <default-drop-profile>
Medium low any 1 <default-drop-profile>
Medium high any 1 <default-drop-profile>
High any 1 <default-drop-profile>
Note that 5% is assigned to NC making sure that RE traffic always has a minimum BW %.
I'm note sure why you'd want to change this. You obviously want to add other Queues and assign BW % as required. Just make sure you always leave pbit 6 mapped to NC FC (queue 3) and leave some BW assigned to it. I wouldn't re-map RE traffic from Queue 3 to some other queue. In Junos (the MX anyway) the queue number as no meaning so there's no reason to move NC from queue 3 to some other queue.
I hope this helps.
Serge
________________________________
From: MOHAMED EDREES - JNT <m.edrees.jnt at mobily.com.sa>
To: "juniper-nsp at puck.nether.net" <juniper-nsp at puck.nether.net>
Sent: Monday, March 12, 2012 10:28:50 AM
Subject: [j-nsp] QOS (Network Control traffic Queue)
Dear Experts
As known in juniper routers the network control traffic by default will be queued in the default queue # 3 which by default called network-control, my questions are
How this forwarding will be forwarded to the queue without applying and classifier on the control plane or even in interface fxp1?
Another question which will depend on the answer of the first one
If we modified the queues to carry different code points as shown below, will the control traffic such as BGP messages will follow these changes or it will go to the default queue # 3 without consideration for the code-points value assigned to that queue.
The default Queues Configuration
[edit class-of-service]
forwarding-classes {
queue 0 best-effort;
queue 1 expedited-forwarding;
queue 2 assured-forwarding;
queue 3 network-control;
The Modified configuration for example
forwarding-classes {
queue 7 nc;
queue 4 af41;
queue 3 af31;
queue 2 af21;
queue 0 be;
Best Regards,
Mohamed Edrees
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