As the popularity of Internet Protocol (IP) telephony increases, equipment manufacturers are preparing for a world in which companies use gear from several different vendors.

While Q.Sig has been a popular interoperability standard, firms such as Mitel, Cisco, Avaya and 3Com are supporting

Session Initiated Protocol (SIP) in some of their products to ensure they can work with competitors’ products.

Although SIP lets some products share certain feature sets with others, a Canadian analyst warns the protocol will not necessarily allow users to take advantage of all product features.

“”As a vendor, if you want to support all of the functions that you have on your platform with SIP it’s going to take a certain conversion effort, because you’re going to have to map out all of your functions into SIP, which is a pretty big effort,”” said Ronald Gruia, enterprise communications program leader at Frost & Sullivan’s Toronto office.

He added that few vendors support SIP on communications servers, though more support it on handsets.

For example, 3Com Corp. introduced the VCX V7000 IP Telephony Solution, which supports SIP. The VCX V7000 includes an upgrade path from 3Com’s network branch exchange (NBX) IP telephony products. 3Com plans to introduce a Linux version of VCX V7000, which currently works on the Sun Solaris operating system.

Bruce Comeau, country manager for 3Com Canada, said NBX users who want to add SIP capability to their system can get a software upgrade to the Linux version of VCX.

Comeau added that 3Com wants to cater to users who want their SIP phones to be able to work with other SIP phones, and to those who want to use handsets based on the IEEE 802.11, or Wi-Fi, wireless local-area networking standard.

For its part, Mitel Networks offers SIP capability on its 5055 IP phone and will include the protocol on more hardware as components get less expensive.

Christian Szpilfogel, Mitel’s head of platforms and applications, said users will look for products with the best features and may choose SIP in order to ensure it will work well with other products in the future.

“”I think people are getting a more realistic expectation,”” he said.

“”There was a point in time when people thought SIP was a nirvana – you’d be able to do all features and get ultimate internetworking, and that’s not a reasonable expectation.

“”Just because somebody has call park on one set of SIP devices doesn’t mean it will work well with call park on another set.””

Szpilfogel added some carriers are starting to adopt SIP in their networks, and this is piquing the interest of enterprise users.

Gruia said another driving force is the limitations of the H.323 standard, which was intended for video conferencing networks but has been adapted to voice over IP.

Greg Meckbach is Editor of Communications & Networking.

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