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Question about queue/CoS behavior

‎08-01-2019 07:07 AM

If I have an interface that has a per-unit-scheduler and 2 units: one unit has a traffic-control-profile with a shaper and scheduler-map applied, the other has nothing applied.  If the unit with nothing applied asks to saturate the whole interface with traffic, what will happen to the unit that has the traffic-control-profile applied?  Will JunOS still guarantee the shaped rate to it in the event it needs bandwidth during this congestion period?

3 REPLIES 3
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Re: Question about queue/CoS behavior

‎08-01-2019 09:29 AM

Hi,

 

To be frank, this may be dependent on platform and type of line cards you are using. You may get different results.

 

However, the idea is like below

 

-> This is how you configure the interface

set interfaces ge-1/2/0 per-unit-scheduler
set interfaces ge-1/2/0 flexible-vlan-tagging
set interfaces ge-1/2/0 encapsulation flexible-ethernet-services
set interfaces ge-1/2/0 unit 1 vlan-id 1
set interfaces ge-1/2/0 unit 1 family inet address 192.168.1.1/30
set interfaces ge-1/2/0 unit 2 vlan-id 2
set interfaces ge-1/2/0 unit 2 family inet address 192.168.2.1/30

 

-> This is the CoS configuration you have described 

set class-of-service traffic-control-profiles mhu-tcp scheduler-map mhu-sch
set class-of-service traffic-control-profiles mhu-tcp shaping-rate 100m
set class-of-service interfaces ge-1/2/0 unit 1 output-traffic-control-profile mhu-tcp
set class-of-service scheduler-maps mhu-sch forwarding-class best-effort scheduler be
set class-of-service scheduler-maps mhu-sch forwarding-class assured-forwarding scheduler af
set class-of-service scheduler-maps mhu-sch forwarding-class expedited-forwarding scheduler ef
set class-of-service scheduler-maps mhu-sch forwarding-class network-control scheduler nc
set class-of-service schedulers be transmit-rate percent 50
set class-of-service schedulers be priority low
set class-of-service schedulers ef transmit-rate percent 5
set class-of-service schedulers ef priority high
set class-of-service schedulers af transmit-rate percent 40
set class-of-service schedulers af priority high
set class-of-service schedulers nc transmit-rate percent 5
set class-of-service schedulers nc priority strict-high

 

-> The guarateed rate for unit 1 is 100m. The guranteed rate for unit 2 or another other unit is (1g - 100m which is 900m). So if unit 2 is exceeding 900m of its allocated BW, it will be considered as out of profile. It will be less competive than in profile traffic in unit 1. Ideally it should not starve valid traffic for unit 1. 

 

-> Below is an example I got from MX80 from PFE output. So that you have an idea how this was progremed in PFE according to the config. But those are internal commands. 

 

--------------------------------------------------------------------------------
IFL name: (ge-1/2/0.1, ge-1/2/0) (Index 397, IFD Index 174) egress information

Queue State Max Guaranteed Burst Weight Priorities Drop-Rules Last Enqueue time
Index rate rate size G E Wred Tail
------ ----------- ----------- ------------ ------- ------ ---------- ---------- --------------------------
16 Configured 100000000 50000000 2097152 500 GL EL 3 25 No packets
17 Configured 100000000 5000000 2097152 50 GH EH 3 216 No packets
18 Configured 100000000 40000000 2097152 400 GH EH 3 216 No packets
19 Configured 100000000 Disabled 2097152 50 GH EH 3 216 No packets

--------------------------------------------------------------------------------
IFL name: (ge-1/2/0.2, ge-1/2/0) (Index 398, IFD Index 174) egress information
..
Queue State Max Guaranteed Burst Weight Priorities Drop-Rules Last Enqueue time
Index rate rate size G E Wred Tail
------ ----------- ----------- ------------ ------- ------ ---------- ---------- --------------------------
24 Configured 1000000000 855000000 8388608 950 GL EL 3 68 No packets
25 Configured 1000000000 0 8388608 1 GL EL 0 4 No packets
26 Configured 1000000000 0 8388608 1 GL EL 0 4 No packets
27 Configured 1000000000 45000000 8388608 50 GL EL 3 17 No packets

 


Mengzhe Hu
JNCIE x 3 (SP DC ENT)
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Junos

Re: Question about queue/CoS behavior

‎08-05-2019 07:41 AM

So one does not need to set the 'guaranteed-rate' in the TCP if already using a shaping-rate?  Based on what you described, JunOS automatically setup guarantees for both unit 1 (configured with shaping) and unit 2 (configured with nothing, but based on unit 1's).

 

Thank you for your response.

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Junos

Re: Question about queue/CoS behavior

‎08-08-2019 07:21 AM

Also, what internal command are you using to view low level details of the queues?

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