Making the call for VoIP standards
Published: 31 Jul 2002 08:03 BST
Both H.323 and SIP have problems with aspects of today's networks. Network address translation -- NAT -- is particularly difficult for peer-to-peer systems, as the network address of a machine behind a NAT gateway makes no sense outside the LAN on which that machine lives. The gateway itself must understand how to translate all packets intended for the machine, and with a complex protocol such as H.323 that can consume considerable resources and require additional management. Firewalls too need to understand either protocol: there is a fundamental tension between exposing every individual device to the wider network for data transfer, and shielding information from the network for security reasons.
Many of the arguments between the SIP and the H.323 camps will be familiar to anyone who remembers when OSI standards first met TCP/IP: H.323 is a widely deployed and mature standard says one group; it's a legacy of the first generation and will be quietly worked around, says the other. H.323 is flexible, capable and scalable -- or it's cumbersome, over-engineered and over-complex. SIP is simple, lightweight and open; or it needs complex interactions with other standards, isn't supported widely and has potential for intellectual property disputes.
Fortunately, nobody needs either H.323 or SIP today or tomorrow. Both can potentially save money and give a better ROI on current systems by coupling voice with data more effectively. Both require awareness from existing network components. No killer application has yet been discovered that makes Internet telephony absolutely essential. Treating the claims and counterclaims of both camps with a degree of scepticism while demanding that advantages are demonstrated, not merely promised, will serve network planners and implementers well while things settle down. Building in volcano zones may be exciting, but it's not for the risk-adverse.
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