Friday, 17 February 2012

Take a small sip...

SIP will be fun...

For those that do not know, Voice over IP is mostly handled using a protocol called SIP. No Skype is some strange shit and not the same at all :-)

There are other protocols but SIP has kind of won the day on this, and for a typical business SIP is about proper phone calls and phone numbers and using "Internet" as the connection medium for those calls.

Now we have done SIP and VoIP generally for some time. Oddly we kind of started in the telephony side selling mobiles and even ISDN switches 15 years ago. So this is turning full circle but with more modern technology than ISDN.

Now, we have used asterisk, and since then I did my own linux based SIP server. It was clever. It did not do media but passed on sdp negotiations between end points and worked as a proxy. Works well for our SIP VoIP services but we want to do more and better.

We have this really good hardware platform, well platforms in fact. The FireBricks. So the plan is to make them do SIP.

I started with the idea that the gigbit boxes (FB 6000s) would be a core ISTP SIP gateway box and we would sell a few to larger SIP based telcos. But as the idea developed we realised that small businesses need SIP on their Internet gateway boxes.

So the idea is to put SIP in the whole range. The smaller FB2500 doing 100Mb/s Internet gateway and local SIP "server" for phones on the LAN. It would handle internal calls and route externally via a carrier (such as us, or many others).

Doing this bypasses all of the crap you get with NAT. NAT is evil! and screws up SIP in many ways. Those few with the right mix of SIP server, NAT gateway, STUN server and SIP phone that happen to play well enough are lucky. Mostly SIP and NAT is a nightmare, and even just SIP and firewalls is a challenge.

So making FireBricks do this is cool. It makes for a nice small office package.

Trick is, having done one SIP server from scratch (very much RFC based), I now know a lot of what really happens and how shit breaks. So the next version will be way better.

So, what can I say? - watch this space.

[now I have blogged I'll have to actually write this, but not for another week or two at the least]

8 comments:

  1. Am loving the NAT Bypass A&A Sip friendly server .. Which beats the hell outta NAT hands down!

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  2. When the ARM chap mentioned SIP servers yesterday, I wondered how long before this post would come!

    It would be great if the FB2700 could do some of the higher end stuff too, memory and processor permitting. Great way for us smaller companies to get on the ladder and escape from Asterisk!

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  3. I have not blogged on the IXLeeds stuff yet - I figured others can do a better job, but it was funny.

    As a group there were loads of "voice" people there (thanks to Adam) who did not even know me. How strange!

    As it happens the ARM guys comments are not FB related. Someone is not joining the dots at AQL I expect. But I hope to get my foot in the door on this.

    I expect an FB2700 can do shit-loads of SIP stuff if we try. The idea is voicemail and call recording is all farmed out to linux boxes, or "the cloud".

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  4. I enjoyed it too. It was interesting to see such a mix of suits and techies. Very different to UKNOF.

    There's no doubt in my mind that your SIP server will be better than any other team will develop, as theirs would inevitably become a SIP server designed by a committee which usually means that compromises have to be made.

    The idea of farming out the heavy lifting makes a lot of sense. I look forward to hearing more about it.

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  5. I want to do a presentation on it to the likes of UKNOF, IXLeeds, etc, when done. Should be interesting in architecture of how to do this stuff.

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  6. Does this mean that our VoIP phones will no longer need real IP addresses? presumably not, if the phones only ever need to talk to the firebrick. I invariably get no RTP incoming if I try NAT, but then I am not using STUN.
    I also assume that the FB will remain in the middle of any conversations (SIP or RTP) that the phones have with any other phone/registrar?

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  7. Looks like I am going the full circle with you then. My first encounter with A&A was when I bought a Network Alchemy ISDN switch for my phones many years ago when 'fast Internet access' was ISDN, then you did ADSL, so I got that, now I have RevTel SIP/IAX and a SIM. Been an interesting journey :)

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