01-06-2011 08:56 AM
Hope to understand the marking/qos on foundry switches, if a device send a packet with dscp 40, will this packet won't be changed and will be in the priority 5 by default without any configuration on the switch? Thanks
01-06-2011 12:19 PM
This will depend on the model of switch you are using. Here is some information out of the Configuration guide:
FastIron GS, LS, WS, and CX Series devices support DSCP-based QoS on a per-port basis.
DSCP-based QoS is not automatically honored for switched traffic. The default is 802.1p to CoS
mapping. To honor DSCP-based QoS, enter the following command at the interface level of the CLI.
Syntax: trust dscp
When trust dscp is enabled, the interface honors the Layer 3 DSCP value. By default, the interface honors the Layer 2 CoS value.
FastIron X Series devices require the use of an ACL to honor DSCP-based QoS for routed traffic in
the Layer 3 image, or for switched traffic in the Layer 2 image. To enable DSCP-based QoS on these
devices, apply an ACL entry such as the following.
FastIron(config)#access-list 101 permit ip any any dscp-cos-mapping
If you are using a different model of switch, please specify.
Please let me know if you have any other questions.
01-06-2011 01:15 PM
Thanks for the information, based on that, I'd like to expand a little bit.
access-list 110 bridged-routed
access-list 110 permit tcp any any eq 1720 dscp-marking 40 dscp-cos-mapping
access-list 110 permit udp any any eq 1720 dscp-marking 40 dscp-cos-mapping
access-list 110 permit tcp any any dscp-marking 0 dscp-cos-mapping
access-list 110 permit udp any any dscp-marking 0 dscp-cos-mapping
access-list 110 permit ip any any
ip access-group 110 in
So with this, on the edge switch FSX, only tcp and udp ports 1720 are marked with dscp 40 and they will use the default map so they will in priority 5, the rest of traffic will be marked at 0.
On the Layer2 uplink of upstream NetIron MLX, I'll put trust dscp on the interface.
Let me know if above configuration is correct.
BTW, what is your recommendation for Bearer Traffic priority on Froundry switches? 5 or 7 ?