Communications

Paul Baran and open spectrum

Paul Baran, an engineer who helped create the technical underpinnings for the Arpanet (the precursor to today’s Internet), died Saturday in Palo Alto, California.  While everyone else celebrates his early contributions to packet networking, I will remember him for his open spectrum advocacy.

I never had the privilege of hearing Paul Baran speak live, but as I became interested in wireless spectrum, one of the earliest references I encountered was this transcript of Paul Baran's Keynote Address at the 8th Annual Conference on Next Generation Networks Washington, DC, November 9, 1994.

His title says it all:

Visions of the 21st Century Communications: Is the Shortage of Radio Spectrum for Broadband Networks of the Future a Self Made Problem?

And here's an excerpt:

   The key point at issue that we will question is the widespread belief
   that we don't have enough radio spectrum to go around. This is a
   common, fundamental belief. Since we live in a world of scarcity or
   natural resources it is almost automatic that we believe that there is
   a shortage of frequencies. This particular resource is somewhat
   different.
   
   This morning, let's start by reviewing this presumption of a permanent
   shortage. Let's consider how, with an application of already known
   technology, we could create even a surplus of frequencies. What may be
   going on is an inadvertent shortage created by a regulatory structure
   which has yet to appreciate the potential capabilities of the new
   digital signal processing technology as applied to communications.

Paul Baran is hardly the originator of open spectrum ideas, but the complete transcript shows he once again led the industry.

 

Mobile oligopoly tightens

I remember the heady days of the late 90s (while the PCS build out was happening).  Depending on how and when you counted, we had more than 6 mobile operators in the Boston area.  Everyone was competing for customers, to the great benefit of the consumer, as mobile phones rapidly transitioned from expensive car phones to relatively low cost, widely adopted personal handheld devices.

In recent years we've seen that competition shrink to just four operators (Verizon, AT&T, Sprint and T-Mobile).  At one time, I was hopeful that Clearwire would be one more operator, but then they became effectively joined to Sprint.  More recently I've been hopeful about Lightsquared, although they are a long way from providing service.

Now we get bad news.  AT&T is buying T-Mobile.  Consolidation!  Less competition not more.  Ugh!

Basic questions about NGNs

I get questions on telecom, mobile and Internet topics from students in different parts of the world and I try to reply to them all as best I can.  One kind of question that comes up repeatedly has to do with "Next Generation Networks" or NGNs - what are they?  why are they based on packet technology?  how do they support multi-services? etc.  

Recently I answered a whole string of such questions for a Masters student in the UK.  Here are my answers:

Hi  ... ,

For most kinds of communication, packet networks are more flexible and more efficient.  And, as a practical matter, the Internet (a packet network) has become a globally pervasive platform, which indeed can be used to support almost any kind of communication.  Most everything is migrating to the Internet because the Internet is pervasive and Internet technology is by far the highest volume and lowest cost of any communications technology.  So it's natural that any envisioned NGN would be built on packet technology.

The term NGN is a bit loaded, as it normally refers to a telco-centric view of how the Internet should evolve.  My views on that are here:

   http://www.tmcnet.com/ngnmag/columns/articles/126646-ngn-itu-misses-boat.htm

For the latest on how many AS numbers have been assigned see:

   http://www.cidr-report.org/as2.0/autnums.html

For the latest on how many AS numbers are currently advertising routes on the Internet backbone, see:

   http://www.cidr-report.org/as2.0/

The only issue with carrying a variety of services over a common platform is whether you need different relative levels of service (QoS) to support different higher level services like telephony, video, web browsing, etc.  The telco view is that a sophisticated range of priorities are essential (and that the telco should be able to differentially bill based on the higher level service that is being carried).  However, no one has figured out a commercially viable way to deliver QoS over the public Internet.  Also, if there is any requirement for QoS at all, it is for very simple differentiation at just those few points where there are bandwidth shortages.

The richest set of details on what an NGN is envisioned to be is presented in the standards of the 3GPP (the body that provides standards for GSM, HSPA, LTE and other wireless networks).  See: 

   http://en.wikipedia.org/wiki/IP_Multimedia_Subsystem

   http://en.wikipedia.org/wiki/System_Architecture_Evolution

and if you want to read the actual 3GPP specs, you might start here:

   http://www.3gpp.org/ftp/Specs/archive/23_series/23.402/23402-a21.zip

You'll have to dig through documentation on the 3GPP's IMS and SAE if you want to understand their plans for their NGN.  I don't expect any NGN to gain much traction compared to the open Internet and I personally have moved from a business where I supplied products to telco equipment vendors into a new business, netBlazr, where we are revolutionizing the delivery of fixed Internet connectivity in urban areas. So I'm not so interested in NGN any more.  :)

MPLS is an IP-centric protocol layer just below the IP layer which allows Internet Service Providers with multiple routes to define "virtual circuits" between points in the core network.  It's a way to hide (i.e. simplify) an otherwise complex network of IP routers and to channel certain kinds of traffic over specific virtual circuits.  This can be used to guarantee enough headroom for certain kinds of traffic and for other network management purposes.  For example, if you want to give priority to voice traffic, you could route all voice-related IP sessions over a different path (different at the MPLS level) and you could guarantee enough bandwidth on that path so voice traffic was never over-subscribed (i.e. never ran out of bandwidth).  When there was little or no voice traffic, other MPLS virtual circuits running over the same links could use the idle bandwidth, but when voice traffic increases, the voice circuit would get it's predetermined bandwidth.

Indeed, MPLS works by assigning labels (which are inserted between the link layer protocol header and the IP header).  Here's a view of how MPLS & QoS are envisioned to work:

   http://www.huawei.com/products/datacomm/catalog.do?id=2515

This is simpler than the ITU/3GPP view of NGN, but still likely more complex than what most network operators are deploying.  On the other hand, I don't have direct field experience operating a backbone network, so i can't give you the real details.  My impression is that Internet backbone operators use MPLS but only for very simple pre-defined bandwidth allocations between major backbone routers.

I hope this helps,

Brough Turner