[VOIPSEC] Performance/QoS implications of Secure SIP?

[Pankaj Shroff]

Hi Tao
 SIP is a signalling protocol. In other words, SIP messages do not actually 
carry voice packets. The SIP messages are used to set up and tear down a 
"VoIP" call. The actual voice packets are typically transported via a 
different protocol on a separate "channel" using the RTP protocol. 
Therefore, for achieving secure VoIP call, you need encryption in two 
places. To achieve security for signalling messages, SIP has to be secured. 
This is done using SIP/TLS (most common) - although there are some other 
ways to do it also. Encrypting the SIP messages does not cause any Quality 
issues with the voice per se. However, the latency added due to encryption 
and decryption may or may not affect messaging. In my experience it does not 
affect it significantly enough. As far as securing the voice itself, there 
is a new up and coming protocol called Secure-RTP or SRTP which allows 
encryption of RTP packets. The QoS implications of this are as of yet 
unknown since it is not in widespread deployment in the industry. You can 
follow this mailing list closely because there is a lot of discussion on 
SRTP here which you might find educaitonal. Good luck!
 Regards
Pankaj 
 -- 
Pankaj Shroff
shroffG at Gmail.com 

 On 9/7/05, Tao Zhang <wzyzht at hotmail.com> wrote: 
> 
> Hi, all
> 
> I am new to VoIP and SIP. I have been wondering about the
> performance/QoS implications of secure SIP. By securing
> SIP, the client has to do a lot of extra cryptograhic operations,
> for example encrypting every VoIP packet, will that degrade
> the quality of the call? Especially quality is critical for VoIP and
> the phone clients may not be very powerful. Or that is not a
> problem at all and the QoS issues for SIP mainly come from
> the network?
> 
> Could somebody point me to some related resources?
> 
> Thanks so much
> 
> Tao
> 
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