Qos in VOIP IPSEC

[safe]

Dear All,

Is it possible to do Qos in Voip IPsec using TOS bit value.How VOIP packet send when using IPSEC means can we read TOS value in between devices.My requirement is that I have to do QOS but my in between device understand TOS value only.

TIA

SAM

[jackko]

just wondering what sort of device we are discussing here.

assuming it's a pix then v7 is a must. refer to the the configuration guide: applying qos policies

http://www.cisco.com/en/US/products/ps6120/products_configuration_guide_chapter09186a0080450b9a.html

[safe]

HI Jack ,

Here we are using Cisco routers , media is Vsat.We want QOS control by IDU which understand TOS value.

TIA

Regards

SAM

[mheusinger]

Hello,

first be aware that the IPSec standard does imply to copy the TOS byte of the encrypted header into the new header. This means in case your VoIP packets are already marked the marking will remain though you do not see the content of the IPSec packets.

Setup policies based on the TOS marking and your VoIP gets preferential treatment.

The second feature you might need to use - only available at the tunnel headend - is QoS pre-classify. There the encrypting router keeps a copy of the original header in memory along with the encrypted packet. This way you can use the original header to specify f.e. RTP traffic should be prioritized.

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Martin

[safe]

thks mheusinger ,

this is also helpfull for me.where can i get sample configuration for testing this set up in LAB.

can u pls give some link where i can get more details @ this.

TIA

SAM.

[mheusinger]

Hello,

you might want to read "Reference Guide to Implementing Crypto and QoS"

http://www.cisco.com/en/US/tech/tk543/tk757/technologies_tech_note09186a00800b3d15.shtml

where the most important informations can be found. What I also found helpful is "Configuring QoS for Virtual Private Networks"

http://www.cisco.com/en/US/products/sw/iosswrel/ps1835/products_configuration_guide_chapter09186a00800c75d3.html

out of the "Cisco IOS Quality of Service Solutions Configuration Guide".

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Martin

[safe]

hi mheusinger,

It is very helpfull for me.Thanks a lot

Regards

SAM

[mheusinger]

Hello,

one more thing: make sure that you calculate with the proper bandwidth per VoIP call. In the case of VoIP over IPSec it will mainly be determined by the overhead. A good starting point for this topic is:

"Voice Over IP - Per Call Bandwidth Consumption"

http://www.cisco.com/en/US/tech/tk652/tk698/technologies_tech_note09186a0080094ae2.shtml

Unfortunately for you it does not talk about IPSec. But adding the IPSec header in your specific installation to each voip packet will allow you to calculate the requirements along the document.

Hope this helps

Martin