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New Member

Satellite link utillisations across 2600 and 3600 routers.

I understand that cisco has specified magin after which it declares a link connected accross two routers over utillised. Sometimes we have a Tx and/or Rx loads as high as 250. Could someone please help with percentage at least for a latency link.

4 REPLIES

Re: Satellite link utillisations across 2600 and 3600 routers.

Hello,

it depends on what you have configured between the routers. Usually, 75% of the bandwidth is available for data, and 25% is reserved for control traffic and overhead. However, these values are configurable, and you can theoretically configure 100% of the available bandwidth for data traffic. So, a value of 250 does not necessarily mean that the link is overutilized. Are you experiencing a specific problem ?

Regards,

GNT

New Member

Re: Satellite link utillisations across 2600 and 3600 routers.

Yes, i monitor excessive packet drops ones have loads exceeding 200/255 over satellite links, but the scenario is not exactly the same with lower latency terrestrial links. The retransmission of these as well as TCP congestion recovery, i believe causes the end station users to experience extreem slow responses. Is there something i can do arrest this situation without increasing the link bandwidth?

Re: Satellite link utillisations across 2600 and 3600 routers.

Hello,

you could try and configure Random Early Detection on your serial interfaces:

Router(config-if)# random-detect

'Random Early Detection (RED) is a congestion avoidance mechanism that takes advantage of the congestion control mechanism of TCP. By randomly dropping packets prior to periods of high congestion, RED tells the packet source to decrease its transmission rate'

In any case, give it a try and see if the performance improves (that is, if the packet drops decrease)...

Regards,

GNT

Gold

Re: Satellite link utillisations across 2600 and 3600 routers.

If you have not already change your router to use 30 seconds averages rather than the default of 5 minutes to calaculate the display. (load command under interface)

If you are getting 250/255 and you have it set to 5 minutes you are most likely overloading the link. It is very likely you burst to 255/255 and it drops traffic the averaging just hides the fact that you went to 100% load.

You only true solution is buy more bandwidth. A temporary thing is to set up QoS on the line to decide who is more important. A very simple way is to set the precedence of all packets as they enter the router to say 3 but set people you don't like to 0. Just put fair queue on the output link if its not already the default. Of course if you wish there are many more QoS options.

Deciding which traffic to set to what priority is tricky. First thing to do while you are figuring it out is to favor the people who yell the loudest and have a valid complaint. You can us IP ACCOUNTING and IP ROUTE-CACHE FLOW to get some data on who is using the link.

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