OC3 - ATM - STM & Alcatel

edavies · ‎11-21-2002

Has anyone configured an OC3 interface for a connection to an alcatel microwave/radio link. We have a private 155mbps microwave service running over alcatel equipment and we are using a 3620 with an OC3 interface at each end to connect to the alcatel equipment. It looks to be configured for ATM on the OC3 interface but the providers of the alcatel equipment have said it is not ATM but STM-1. The link is working to some extent but we have a lot of performance problems. Does anyone have any experience in a setup linke this or can anyone advise of some references to check.

thanks

Evan

Frederic Vanderbecq · ‎11-22-2002

You can run ATM over that STM-1 link without any problems. As long as the service provider is giving you a Concatenated STM-1 (STM-1c).

As for the performances, this may be related to delay across the satellite link. When you do a ping from router to router, what is the RTT ?

Can you also elaborate on the performance problem ? Are there any errors recorded under the router interfaces ?

edavies · ‎11-24-2002

Performance is very erratic - It is like it is very quick and then suddenly loses a packet, waits and retansmits.

The RTT is quite quick - the service is just a point to point link of about 1 km or so on microwave. See below for an example of typical behaviour of a test ping across the link.

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!!!!!!!!.!!!!!!!!!!

!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!.!!!!!!!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!.!

!!!!.!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

!!!!!!!!!!

Success rate is 98 percent (493/500), round-trip min/avg/max = 1/4/16 ms

I am not seeing any errors on the router interfaces except for a small number of some AAL5 length voilations and AAL5 CPI errors.

We actually own the microwave equipment but a service provider set it up and I am unsure if it is STM-1c or STM-1.

I noticed an atm command since posting the original question

atm sonet stm-1

Has anyone used this or have any idea if it may help?

Frederic Vanderbecq · ‎11-25-2002

If you see AAL5 length voilations, it means that cells are being dropped causing packets to be corrupted and thus dropped. When you issue a show controller atm x/y, do you see any errors ? It is possible that the satellite link or the Alcatel boxes are causing a problem.

One test you could do is a loopback test. Physically loop the router ATM interfaces and have each of them ping their own ATM (sub)interface. If you are dropping packets in that scenario, it may mean that you have a hardware problem on that router. If that test runs clean, then the problem comes from the satellite link or Alcatel modem.

edavies · ‎11-25-2002

Thanks for that. I am going to try the tests you suggest shortly and try and isolate the problem to the routers or the transmission - have to wait a week or so before they will give me an outage.

Frederic Vanderbecq · ‎11-25-2002

One thing I forgot to mention. If you have configured the main interface or a multipoint sub-interface, for the router to be able to ping itself, you will have to add a static mapping for the router IP address under the PVC. If you are using point-to-point sub-interfaces, there are no changes to make.