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The Ultimate Transport

October 15, 2007 - 0 Comments

The unprecedented growth of IP based networks over the last decade or so has blurred the traditional distinctions often made between switching and transmission systems in SP networks. Many in today’s IP dominated businesses scarcely acknowledge there is a difference, and maybe what differences there are will eventually disappear, relegated to history’s dustbin.Still, it would be foolhardy to design networks assuming that these two basic aspects of networking did not answer to quite different requirements, since they fulfill entirely different functions in SP networks. If so, does it make sense that one type of packet technology, e.g. IP/MPLS, can be pressed into service for both switching and transmission systems?Conventional wisdom suggests this should be quite feasible. After all, a packet is a packet, so what if you switch it in routers located in San Jose, or transmit it from San Francisco to Boston over an optical fiber transmission system! But the reality is that transmission systems have traditionally dealt with a whole different problem set than switching/routing equipment need to deal with. Many of these issues stem from the need to effectively manage long haul networks remotely using centralized OSS. And there is always the challenge of ensuring extremely high availability and survivability in the face of inevitable human and natural disasters to widely scattered outside plant. Conventional transport systems, such as those based on the ubiquitous SDH (or even ATM) technologies, have evolved complex network management and OAM mechanisms to handle these challenges.As network operators evolve their transport systems from conventional SDH based equipment to packet based (IP/MPLS or Ethernet) transport in their drive for OPEX and CAPEX savings, these challenges remain. The question arises as to how these packet technologies, originally conceived for primarily switching/routing operations, should be adapted for long haul transport operations.It seems how one does this depends on who you talk to! Many approaches are being pursued in the burgeoning market for packet based transport. But the nagging doubt remains as to whether these approaches, often adorned with hopeful acronyms like T-MPLS, PBT, PBB-TE and the like, really meet the stringent demands of carrier class packet transport technology? They seem like work-arounds, rather than solutions!It has been tried before, and not so long ago. After all, ATM was designed as both a switching and a transmission system technology, with capabilities built-in to satisfy the demands of both worlds. It could even be conjectured that ATM’s brave attempt to be all things to all men resulted in an over-complex technology that had to make so many compromises that it satisfied no-one in the end! Could such a fate befall other packet technologies that tried to satisfy both the diverse transmission and routing worlds? Yes, it’s possible, if we don’t learn from the lessons of history. But if we architect packet transport intelligently, bearing in mind the differing demands of transport and switching, there is no reason why it would not be possible to come up with the ultimate transport technology.That’s a challenge I for one am willing to sign up to.

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