Applying QoS to net management traffic

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Apr 29th, 2008
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We are using 3750 switches in our core & distribution layer in many sites. WAN links are at a variety of speed (2 M, 5M, 10M up to dark fiber running at 1G)through our MAN provider network. I'm actually designing the QoS strategy and implementation for support Voice, Mission critical traffics, best effort and so on. The only traffics I don't know how to mark them, are network management traffics generated by the network element itself: as SNMP, NTP, Syslog, TFTP, telnet, SSH. Do you have an idea how to do that? I know OSPF is marked by default to dscp 48 which is fine. What about the other net man traffics.



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Joseph W. Doherty Tue, 04/29/2008 - 11:50
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If you're asking for recommendations for marking, I suggest better markings for lightweight and/or highly interactive traffic. This would include, NTP, telnet and SSH (SSH, though, can burn you if someone uses SCP.)

You might also want to insure non-TCP traffic isn't dropped. Don't always need to raise priority, increasing queue size for such traffic might also work. This would include traffic like syslog and TFTP, and perhaps, SNMP.

Don't forget, you can have asymmetric QoS, better priority treatment for SNMP queries, less on results.

bdube Wed, 04/30/2008 - 06:55
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Hi Joseph,

Thanks for your answer.

I already have a strategy to mark lightweight, interactive, mission critical traffic and so on. The traffic I want to mark is the one for the switches/routers management, mainly those traffic issued by the equipment itself. Since, my customer is using mainly 3750-L3 and 3560-L3 switches I can only mark incoming traffic. I don't find the way to mark traffic issued by the equipment itself.



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