Junos Cup 2014
Junos Cup 2014

Tournament 3: Portugal Challenge & Solution: End-to-End Class of Service

[ Edited ]
‎06-26-2014 07:17 AM

Country Flag: Portugal


Author: Jay Wu


Title: End-to-End Class of Service


Type: Service Provider


Difficulty: High (2 points).


Technical Description: With just three set configuration commands, ensure that the packets with IP precedence 5 (and only those packets) are placed in the expedited-forwarding queue across the core routers.






Challenge Instructions:

For this challenge, you need to start the topology “PORTUGAL – End-to-End Class of Service”.


The goal of this challenge is to provide end-to-end CoS guarantees from CE1 to CE2:


- Traffic from CE1 to CE2 with IP precedence 5 should be placed into the expedited-forwarding queue at the egress interface of all the core routers (PE1, P, PE2). Yes, including PE2 when it sends the packets out of ge-0/0/2.


- Other traffic from CE1 to CE2 (packets with other IP precedence bits) should be placed into the best-effort queue across all core routers.


You can generate ICMP packets in order to simulate customer’s traffic:

juniper@CE1> ping interval 0.1 source tos <value>


Then, on the core routers, you can check the egress queue by executing:

juniper@P*> show interfaces queue ge-0/0/2 | except "   0"


TIP: Multiply the IP precedence times 32, and you’ll get the tos value. For example, if you want to send packets with IP precedence 5, then use ping option tos 160.


Your answer to the challenge must meet the following conditions:

- You are only allowed to modify the configuration of PE routers.

- You cannot modify or create any classifier under [edit class-of-service classifiers], but you are allowed to use any already existing classifiers to complete this task.

- You are not allowed to configure any new firewall filter.

- You are not allowed to make any change under the [edit protocols] hierarchy.

- You must accomplish the solution with three set commands, two of which are issued at one PE and the third at the other PE, so your answer looks like the following:


At one PE:


<set command #1>

<set command #2>



And at the other PE:


<set command #3>



To solve this challenge submit the three set commands according to this challenge’s conditions.


NOTE: If you have issues connecting to the Junosphere topology please check Junosphere Technical documentation, or request assistance in the Junosphere forum 

Send an email with your proposed solution to junos-cup@juniper.net:

  •  The subject should be “<country-name-of-the-challenge> -  <your-full-name>”. For example: “Brazil – Wolfgang Amadeus Mozart”.
  • In the email body, please include your proposed solution, along with your first and last name and complete mailing address including zip/postal code and your shirt size (S, M, L, XL, XXL, XXXL) (Only if you haven’t already submitted your address/shirt size on a previous submission)


Deadline to Respond: Tuesday, 1st of July 23:59:59 Pacific Daylight Time (PDT) 

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Some additional notes:

  • You can try to solve and submit answers for as many active challenges as you wish
  • The answers will be read by the organization right after the deadline
  • The challenge instructions are final, and no additional information or tips will be provided before the publication of the solution and the winner list. Please don’t expect a reply from junos-cup@juniper.net.
  • If you feel that your initial solution is wrong or incomplete, you can send up to three messages for the same challenge, but please note that only your last message (received before the deadline) will be read.
  • If you think there is an error in the definition of the challenges, please send us an email with subject (“<country-name> ERROR”); if there is no reply, then it’s likely an intentional condition of the challenge, rather than an error.




At PE1:


juniper@PE1# set class-of-service interfaces ge-0/0/2 unit 0 rewrite-rules exp EXP-WR protocol mpls-inet-both-non-vpn  


juniper@PE1# set firewall family inet filter MF-classifier term others then loss-priority low    


At PE2:


juniper@PE2# set class-of-service interfaces ge-0/0/1 unit 0 classifiers inet-precedence default   


Julie Wider
Advocacy Manager
Twitter: @JNetCommunity & @jawider