Moved to sip-implementors list ... Most sip stacks that have wide interoperability have many person years of engineering effort in them. Even if you had a perfect stack today, it is a significant ongoing effort to keep it tracking the changes and keep it up to date. It is hard to answer questions like the one you ask because the answers will vary widely. I will take a stab at this but keep in mind these are very rough and would probably vary by two orders of magnitude based on what you wanted to do.
SIP looks surprisingly easy to implement - and you can get something that makes calls working very quickly. I'm will to guess that Henning has had graduate students that wrote working SIP applications in a time span of a few days to a week. On the other end several large company have many engineers long term dedicated to having working SIP stacks. Many vendors have found it cheaper to license telecom stacks from others than develop there own - check out the number of people using other vendors H.323 or SS7 stacks. If you want to get a feel of whats in a SIP stack, check out some of the open source ones such as the one at NIST or www.vovida.org. To build a SIP stack you need competent programmers that can do network programming, protocol parsing and such. It also helps greatly to have a few people who deeply understand how SIP works - why it works that way - and what the complex things are that have messed up other implementation. Ironically as SIP has gotten more complex and more widespread recognition, the market has changed in a way that's makes it easier to hire these sort of people than ever before. A team of 5 engineers could likely put together an initial working implementation suitable for a complex IP phone in 3-5 months and after a sipit or two have it widely interoperable. A proxy implementation is simpler. After the initial 4-9 months a team of 2 engineers could likely support it and keep it tracking the standards. Keep in mind the accuracy of these estimates is likely in the multiple or divide by 50 zone. What features of SIP you need, how interoperable the implementation is, what you do with security, how much previous experience you have, how small or fast you needed it, and so on all change this estimate a bunch. As a final question I often ask people who are about to implement their own SIP stack - what TCP stack are you going to use? I have never had some tell me there were writing their own. In fact, they often say they will us one that can track it's roots back to a BSD stack. It always makes me wonder - why not use an open source stack. There are a few around. It may be that one of the open source ones is lacking some feature you needs but, would it not be easier to add that feature than write a complete new stack? What's your competitive advantage - hopefully it's your application - people who think their SIP stack is their sustainable competitive advantage you are probably unclear on the goals of SIP. Cullen > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of sumir > Sent: Monday, November 25, 2002 11:11 PM > To: [EMAIL PROTECTED] > Subject: [Sip] Sip Stack Market Place. Follow-Up! > > > Hi friends > > I am highly thankful to Mr. Mohammed Asfar of Nokia and Mr. Jeff > Hoefgen of > Radvision for their answers... > > I hv some questions like: > Q1 What if I start developing a sip stack. what techical knowledge and > resources I require? > Q2 What is the approximate development time for developing sip stack? (man > days). > Q3 > How many people is needed to dedicate to developing sip stack? > Q4 What are my costs for developing these stacks? > Q5 What technical resources I need to build these stacks? > Q6 Do i need to follow certain rules if any.. > > Looking forward to hear from you friends soon > > With regards! > sam > > > _______________________________________________ Sip-implementors mailing list [EMAIL PROTECTED] http://lists.cs.columbia.edu/mailman/listinfo/sip-implementors
