Wednesday, May 04, 2005

WTF is the NGN?

WTF is the NGN?


Richard Stastny VoIP and ENUM
The problem with the Next Generation Network (NGN) is not that there exists no definition what it is, it is the other way round: there are too many definitions and viewpoints, so everybody has his own opinion. This faith of course is depending what an individual thinks that the "Existing Generation Network" is. Bellheads living in a circuit-switching (TDM) world basically think the NGN is a "packet-based" network (because they like to be generic and want to avoid the term IP, because it is to "specific").

In turn the term NGN was not well understood (and if, not very much liked) by the netheads at the IETF, because they obviously consider "packed-based" as the "Existing Generation Network", not as NGN.

Living in both worlds, I personally consider (and have used it in this way intrisically in my blog) the term NGN as opposite to the "public" Internet, so the NGN is an IP-based network or application in a "walled garden". This separation can be in the transport layer (e.g. by having no or only a very controlled connectivity with the "public" address- or namespace), or on the application (or service) layer (e.g. Vonage or Skype), or both (e.g Yahoo!BB or the IMS NGN). This viewpoint is of course influenced by my work in ETSI TISPAN on IMS and also by my work in IETF on ENUM.

So I was very interested to visit the ITU-T Workshop on NGN in collaboration with the IETF and to hear the different viewpoints, especially what the IETF has to say on the NGN approach from ITU-T and ETSI.

The progam started after the welcome by Mr. Houlin Zhao (director of the ITU TSB) with a presentation from Brian Carpenter (IETF chair), stating the position of the IETF in general and citing from RFC3935 "The Mission of the IETF", 2004:
The goal of the IETF is to make the Internet work better.
and defining the Internet:
A large, heterogeneous collection of interconnected systems that can be used for communication of many different types between any interested parties connected to it. The term includes both the “core Internet” (ISP networks) and “edge Internet” (corporate and private networks, often connected via firewalls, NAT boxes, application layer gateways and similar devices). The Internet is a truly global network, reaching into just about every country in the world. The IETF community wants the Internet to succeed because we believe that the existence of the Internet, and its influence on economics, communication, and education, will help us to build a better human society.
He also set the scene of the IETF view in relation to the ITU-T NGN view:
We believe that the requirements and services described in the ITU-T NGN effort represent an important plan for future network activities, but
they are just one plan
we may disagree about the expected viability of
some design choices, based on collected experience in developing and deploying the Internet.
Next on the schedule was Session1: Requirements and Functional Architecture

For didactical reasons I start with the second presentation from Dave Meyer: A Brief Overview of the IETF and the Internet Architecture: Past, Present and Future.

The core statements of his presentation regarding the NGN where related to the End-to-End principle of the Internet:
... the end-to-end principle is perhaps the most fundamental and least
understood of the Internet’s architectural principles…:
Nothing should be done in the network that can be efficiently done in an end-system.
A function that must be performed at a higher layer should not also be performed at a lower layer (without a good reason)
He did not say it, but especially the first bullet point means: keep the network simple and stupid.

He then made a tour-de-force through the principles of the Internet architecture, for each point stating past, presence and future areas of activity:
Simplicity, Multiplexing, Transparency, Universal connectivity, Immediate Delivery, Subnet Heterogenity, Common Bearer Service, Connectionless Network, Minimal Dependency,Global Addressing, Regions, Mobility, Protocol Layering, Distributed Control, Global routing computation, Security, Network Resource Allocation
The conclusion was:
The Internet is evolving to support diverse and emerging requirements sets
Including many of the requirements that are beginning to be specified by projects such as the ITU’s NGN
Note this kind of “evolvability” is a fundamental property of the IA (deriving from its “minimalist semantics”)
So where are the architectural misalignments?
And where can we work together?
Ok, he knew the misalignments already, because Keith Knightson, Rapporteur ITU-T SG13 Q.3 -Architecture gave his presentation "Basic NGN Architecture - Principles & Issues" first.

Keith started with the Next Generation Network (NGN) definition from ITU-T Recommendation Y.2001:
A packet-based network able to provide telecommunication services and able to make use of multiple broadband, QoS-enabled transport technologies and in which service-related functions are independent from underlying transport-related technologies.

It enables unfettered (unrestricted - for non-native readers) access for users to networks and to competing service providers and/or services of their choice. It supports generalized mobility which will allow consistent and ubiquitous provision of services to users.
Ok, any net-head may sign this on a first look, but behold, WTF is meant by "services" and the "provision" of these?. "Service" is similar to "NGN", too may different definitions around.

One had to wait until the morning session 5 "Security" on the second day to get the simple answer from the IETF on this by Jon Peterson on slide 2 of his presentation:
On the Internet, telephony is an application

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