Thursday, January 3, 2013

MPLS QoS Testing Tools

When you're setting the mpls experiment bit on the PE router for traffic coming from CE router you must use imposition for QoS treatment. You cannot use topmost because the packet is IP packet. If you're on a P router you can set or match on the topmost label for the swap function. If you're on the PE router receiving traffic from the P router then you can also set and match on the topmost label.
Whether a customers sets the DSCP/TOS or you set an mpls exp bit inbound on a PE router you have to match on the mpls experiment bits as the packet leaves the PE router going to the P router because the packet is an mpls packet not an IP packet. If a packet is marked by a customer with a DSCP or TOS value, that value will be honored/mapped to an mpls experiment value. See the chart below for mappings honored:-

0000|0000-7000000 - 000111000-1F0000|0000 - 0001|1111
1001|00041501001000 - 001111120-3F0010|0000 - 0011|1111
2010|00016-23010000 - 010111240-5F0100|0000 - 0101|1111
3011|00024-31011000 - 011111360-7F0110|0000 - 0111|1111
4100|00032-39100000 - 100111480-9F1000|0000 - 1001|1111
5101|00040-47101000 - 1011115A0-BF1010|0000 - 1011|1111
6110|00048-55110000 - 1101116C0-DF1100|0000 - 1101|1111
7111|00056-63111000 - 1111117E0-FF1110|0000 - 1111|1111
You can verify your QOS policies by using the ip telnet tos in hex command. This works great, for example if you want to generate traffic with a TOS value of 6 or a DSCP value of 54 you would use the command ip telnet tos 11000000. Telnet from one CE router to the other CE router and the telnet traffic will be marked with TOS 6 or DSCP 54.

After you configure ip telnet tos xx on an edge device telnet to the far end of your network and run some commands in order to generate some telnet traffic. Next use the "show policy-map interface and look for packets matched to see if your policy is configured correctly.

You can also see the TOS or DSCP value set on IP traffic traversing the network use ip accounting precedence output or input on the PE or CE router. Then use the show interface precedence command.

People who read this post also read :

No comments: