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New Member

Double hop Sattelite delay & Voip call setup Problem

As it is already known voice is delay sensitve. Ýn many situations where delays range from 10 - 500 (600) msec it is possible to get a succesfull call setup.

Is there a way of configuring of setting up/configuring cisco routers to compensate for the delay (1300 - 1400 msec) caused by double hop satellite links in order achieve call setup. (Such a link was tested with a 2600 and 1750 router and call setup was not possible over the link...)

I remember reading a article where cisco engineers had to reconfigure the parameters in Ciscos Soft Phone in order to compensate for delays of around 1 sec.


Re: Double hop Sattelite delay & Voip call setup Problem

The acceptable delay is actually much lower at less than 200 msecs. It is not recommended to do a VoIP implementation in satellite links given the high round trip delay factor. Even if you go ahead and manage somehow, you would still end up with poor voice quality.

Re: Double hop Sattelite delay & Voip call setup Problem


i too coming under the same situation but not with the sat links but with the LL itself.the roundtrip is rangning between 400ms to 490ms.i hve read that to hv a good quality it shuld be 150ms oneway ther anyway to compensate the delay and make the voip trouble free.




Re: Double hop Sattelite delay & Voip call setup Problem

We are running Voip over sat to 50 oilrigs all over the world.

The voice quality is excellent.

As long as the delay is not varying more than 100Ms there should be no problem with the 600Ms/1200Ms sat delay.

We are using mostly 2650 and 1700 ruters at the different sites.

New Member

Re: Double hop Sattelite delay & Voip call setup Problem

The term VoIP suggests non-IP telephony solution which helps. The sofphone statement is another problem.RTT over single hop satellite can be around 560+ Mseconds. The delay isn't a huge issue, the Jitter is the killer here.The human element can adapt very well to delay as long as it's fixed. The router likes this to. (Voice codec's on Cisco boxes are very sharp and in my experience beat the pants of most FIFO mux's i have had to wrestle with).

the double hop is your real problem as your RTT has leapt to well over 1 second. Very scruffy for voice. How is fax behaving in this setup ? not so good i think.

Moat application will be around 30% efficient in this setup, If you can - convert one of your WAN links to terrestrial and apply tons of QoS to all voice and data streams. FRF12 or LFI for MLPPP with a priority statment for your LLQ voice queue. search for these keywords on CCO for config examples. Good Luck!

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