rtp header compression on VPN

connect101 · ‎08-06-2007

Hi,

Is it possible to compress th rtp header on a VPN.

I use fastEthernet to connect with the IDU.I can't use the rtp-header compression on the FastEthernet interface.

In other case, how can I activate IP RTP Header-compression, if I use FastEthernet interface.

Thanks

paolo bevilacqua · ‎08-06-2007

cRTP is supported only on serial interfaces. So you cannot enable it on VPN or fastethernet.

Hope this helps, please rate post if it does!

connect101 · ‎08-07-2007

I have only 512Kbps with my ISP.

So the max number of call that can be supported is 6, because of the FastEhternet.I use VPN (site-to-site) for the call tranfert to my remote CME.

1 - Is there any idea to improve the number of the call?

2 - How can I reduce the bandwitdh consumption, per call? Now it is 60Kbps per call. I wanna reduce it.

I already use VPN (group 2 for the isakmp policy) and autoQoS Voip.

Thanks :-)

paolo bevilacqua · ‎08-07-2007

Hi,

Are you using g.711 ? That would be 87 kbps per call, not 60.

You can configure g.729 under the ephones, but you need to do that for all the ephones you are using site-site.

connect101 · ‎08-07-2007

Hi,

No I'm using g729r for the two dial-peer.

The calculation is with thi site : http://tools.cisco.com/Support/VBC/do/CodecCalc2.do

I'm using tunnel interface for the VPN.

Thks,

paolo bevilacqua · ‎08-07-2007

Hi,

if g.729 is successfully negotiate (check on the phones pressing ? twice and look at info), your only option to reduce bandwidth would be to pass voice without VPN, directly on a internet interface with public address.

connect101 · ‎08-07-2007

Hi,

If I don't use VPN, there is no safety.

And how about fragmentation?