Packet loss and slowness on frame relay network

Cintron · ‎04-01-2006

We are in the states and have point-to-point connections in the states and Canada. We have about 30 offices in Canada using frame relay point to point connections. We just started noticing that the sites are experiencing about 5-10% packet loss during continuous pings. The packet loss occurs during the day when there is the most traffic. The sites have 32K, 64K, 128K and 256K CIR's. We checked with our provider and they were seeing no problems at the CO to the offices in question. They did see some FECNs in their switches and so did I on our 2600 routers, except when running continous pings I don't see the replies going to large numbers for example a ping session may look like this:

Reply from 68.142.226.51: bytes=32 time=16ms TTL=47

Reply from 68.142.226.51: bytes=32 time=17ms TTL=47

Reply from 68.142.226.51: bytes=32 time=16ms TTL=48

Request timed out.

Reply from 68.142.226.51: bytes=32 time=19ms TTL=47

Reply from 68.142.226.51: bytes=32 time=21ms TTL=47

Reply from 68.142.226.51: bytes=32 time=20ms TTL=48

Reply from 68.142.226.51: bytes=32 time=16ms TTL=47

Reply from 68.142.226.51: bytes=32 time=17ms TTL=47

Request timed out.

Reply from 68.142.226.51: bytes=32 time=16ms TTL=48

Reply from 68.142.226.51: bytes=32 time=19ms TTL=47

Request timed out.

Reply from 68.142.226.51: bytes=32 time=21ms TTL=47

Reply from 68.142.226.51: bytes=32 time=20ms TTL=48

Reply from 68.142.226.51: bytes=32 time=16ms TTL=47

Reply from 68.142.226.51: bytes=32 time=17ms TTL=47

Reply from 68.142.226.51: bytes=32 time=16ms TTL=48

Request timed out.

Reply from 68.142.226.51: bytes=32 time=19ms TTL=47

Reply from 68.142.226.51: bytes=32 time=21ms TTL=47

Reply from 68.142.226.51: bytes=32 time=20ms TTL=48

If you notice the replies are at about 17-20ms avg but then timeouts occur. If there was overutilization or packet bursts, the replies would be higher until the timeouts would occur which is not happening here. The provider thinks they're seeing overutilization of the circuits but I'm thinking something's not working here, whether it be a frame switch or a CSU perhaps on our end but not sure where to look. Any ideas?

sundar.palaniappan · ‎04-01-2006

Here's how I would approach this problem.

Limit traffic sent to the CIR setting. You can use FRTS or GTS to accomplish this. At this point, you shouldn't see any DE/FECN/BECN on the router and you shouldn't also be losing any packets. If you still see any of the above, problem is either incorrect provision of circuit on the Telco network or a physical layer problem. Obviously, if you don't see any packet loss after applying shaping on the router the problem is oversubscription.

If you suspect a physical layer problem, check the interface on the router and service-module/controller if you are using an internal WIC CSU/DSU. If it's an external CSU/DSU, check on the vendor web site how to troubleshoot.

Let us know how it goes.

--Sundar

Cintron · ‎04-01-2006

Can you elaborate on FRTS or GTS? Are these terms or commands for traffic shaping? Where can I get more info on usage of traffic shaping?

sundar.palaniappan · ‎04-02-2006

Here's it is.

http://www.cisco.com/en/US/partner/tech/tk713/tk237/technologies_configuration_example09186a00800942f8.shtml

http://www.cisco.com/en/US/customer/tech/tk713/tk237/technologies_tech_note09186a008014f8a7.shtml#generic

HTH,

Sundar