Unbalancedtraffic_OSPF_MPLS

[asakurahao]

Hi Everyone

We are running OSPF with 4 point to point parallel links between two routers to carrying MPLS traffic.

The said 4 parallel links have equal cost to load balance traffic, however the actual traffic between the 4 links are unequal.

The first link gets the largest share (bulk) of the total traffic while the the 3 other parallel links gets to load balance the remaining parts of the traffic.

May i ask anyone how can i solve the problem or ways to make sure that all 4 parallel links balance traffic almost equally.

Thank you very much for your time and help.

Best Regards,

asakurahao

[Giuseppe Larosa]

Hello Asakurahao,

it all depends on the type of traffic.

MPLS traffic is balanced based on the internal MPLS label that is provided by MP BGP in case of L3 VPN or by LDP in targeted sessions in case of EoMPLS.

A single label is advertised by  the PE node for a VPNv4 prefix or a pseudowire and as a result of this a single link is selected for this type of traffic.

What can be done depends on the platforms involved what model are the routers in your network setup?

Hope to help

Giuseppe

[asakurahao]

Hi Giuseppe Larosa,

I am currently using 7606-S with ES plus linecard running IOS SRE5.

My apologies but the topic seems a liitle vague to me.

We are using pseudowire switching with different virtual circuit IDs for each vlan, the same set off vlans and architecture used for my entire network.

And btw, is there a way (show commands) so that i can see or verify the amount of traffic passing via each pseudowire (EoMPLS).

Thanks!

[Giuseppe Larosa]

Hello Jayson,

what I have seen in my tests is that traffic of each pseudowire uses a single path, traffic of different  pseudowires may follow different paths

try the following to check stats of each pseudowire to see traffic on each pseudowire (see last section of the output)

show mpls l2transport vc detail

see

http://www.cisco.com/en/US/docs/ios-xml/ios/mpls/command/mp-s2.html#GUID-71FBEEB2-0101-4B76-8967-0D26E503CFA9

Hope to help

Giuseppe

[asakurahao]

Hi Giuseppe,

Good day to you!

Im aware of the commands showing the status of ecah vc, but unfortunately i am not that aware on how I can do load balancing the packets using ospf.

i have read some documents regarding parallel links running ospf for load balancing but all needs cef. can i use cef together with mpls ethernet over mpls?

Thanks!

Best regards,

asakurahao

[Giuseppe Larosa]

Hello Jayson,

your network device is already using CEF, MPLS is based on CEF in Cisco implementation so you cannot turn on CEF as it is already operational.

OSPF does provide only the routing to the other PE loopback address. However, in the forwarding plane the problem becomes that of moving MPLS frames with two MPLS labels:

the more external label points to the remote PE node loopback address and it is always the same for all pseudowires defined/terminated on the same PE node.

the internal label changes for each pseudowire and it is negotiated by LDP targeted sessions.

Traffic belonging to the same pseudowire will have the same values for the two MPLS labels and all frames will go over a single link.

So traffic of different pseudowires having a different internal label can use different paths among the 4 parallel paths, but the path selection is based on internal label value only and OSPF does not play a role in this.

Hope to help

Giuseppe