SIP Protocol

[rboynton]

Are there any issues with Wingate handling SIP traffic? We currently have a separate circuit for internet and VoIP, and want to combine them to save money.

[rboynton]

Perhaps a better question is how to best provide QoS for the SIP traffic. There does not appear to be any provision for QoS, but perhaps I could prioritize the traffic by source and destination IP address to achieve the same result. Anyone successfully using VoIP through Wingate?

[adrien]

Hi Rick

I did a bit of research on SIP. Basically it's only a management protocol for establishing calls etc. It doesn't actually carry the VOIP data itself, this is negotiated over another protocol, which can vary depending on capabilities of the agents involved.

E.g. SIP can be used to set up SDP, RTP, RTSP etc media channels.

I think it's these other protocols that may or may not have trouble going through a firewall/NAT depending on what IP-based protocols they use. If they go over TCP or UDP they should work fine, but if they have their own IP-level protocols there would be problems going through WinGate.

QoS normally uses the Type of Service header in the IP frame (now called "Differentiated Services Code Point") to signal congestion, and prioritise traffic. WinGate doesn't use this field for prioritisation, so it's not QoS per se, however you can prioritise traffic through WinGate based on a number of attributes.

Adrien

[rboynton]

Thanks Adrien. I know what the originating IP is, and the target is always the SIP based phone system. This being the case, it may be easier to insert a router upstream to separate out the SIP traffic (based on the originating IP) from all other before it hits the Wingate box.

In fact, now that I think about it, we would not want the phone traffic going through Wingate. You and I discussed the issue of the number of concurrent connections counting against our license count. Though we recently had to upgrade our license (nearly continual license violation notifications), the number of inbound calls could quickly put us in the same spot again.