As will soon become apparent, it is the way in which the Internet has evolved and hence its current structure that allows for the possibility of certain ISPs and larger Telcos to jointly exercise what would amount to an elitist monopolistic style of control over the Internet encompassing all elements and aspects of its accessibility, delivery, reach and functionality.

It is those issues surrounding current and future Internet accessibility that are of particular relevance considering the content, scope and provisions of various tabled and pending legislations in the USA and other countries. Make no mistake about it. What is at stake here is the very thing that has made the Internet what it is today; its neutrality.

Therefore; throughout the course of this investigation, we will be keeping an eye to the future while paying specific attention to how it is possible for ISPs, if permitted to control the Internet and all elements and aspects of its accessibility.

A Distributed Wide Area Network (WAN) Model

In essence, the Internet (internetwork) is based around a distributed Wide Area Networking (WAN) model (see Fig.1 above) comprised of untold numbers of different networks of varying architectures, topologies, technologies, sizes and complexity being linked together to form one giant internetwork spanning the entire globe and even beyond into space. Yes, they do have Internet access onboard the International Space Station (ISS).

As depicted in Figure 1; consumers, enterprises and organizations of all types and sizes wishing to access remote resources or to connect with another network via the Internet must first establish and maintain a connection with their Internet Service Provider (ISP). This ISP will in turn accesses the Internet backbone either directly at an Internet Exchange Point (IX or IXP) or by connecting with another (usually larger) ISP from whom they purchase IP transit or peer with. See IP Transit for more details.

The key factor that defines a distributed WAN is that servers and clients will be spread throughout the entirety of the network more or less randomly. In fact, up until recently the majority of Internet access and services were such that end-points would be continually and sporadically connecting and disconnecting without prior notice to their ISP.

From an ISP's perspective, this behavior placed scalability issues among the hardest facets of service provision and quality of service delivery to address.

It was also common for ISPs to terminate endpoint connections that they (the ISP) “deemed” to be idle. Unfortunately, the end user and their ISP often have very different and conflicting ideas and definitions of what constitutes idle and therefore qualifying for connection termination. This has always been the most frustrating characteristic of traditional dial-up Internet access.

The Rise of Point-to-Point Links

When dissecting and analyzing the structure and topology of the Internet it is important to never lose sight of its fundamentally distributed conglomerate nature. One direct consequence of this is that routers play an essential role in connecting together the various networks and subnets which comprise the Internet.

In general, whenever these different networks are not geographically adjacent dedicated always on point-to-point links have up until recently been the traditional modus operandi (see Figure 2 below).

Historically, this type of point-to-point full-time telecommunications interconnect is known as a leased-line and in its simplest form consists of a dedicated telephone line with modems and routers or modem/routers at each end. Standard practice in implementing this design is to assign the dedicated link a subnet unto itself with only two IP addresses; one for each end.

This type of arrangement was fine from an enterprise perspective as it permitted various geographically dispersed branches of an organization to be permanently connected while preserving IP addresses.

The biggest drawback however, is the fact that point-to-point connectivity deployed as a full mesh topology (see Figure 2 above) rapidly becomes an over complicated administrative and economical nightmare. As the number of separated sites requiring interconnection increases, so too does the number of relatively expensive dedicated leased-lines and associated point-to-point connectivity terminal devices (modems, routers, cabling etc.) and infrastructure (distribution and access devices and wiring).

Another problem with traditional point-to-point connectivity is that each individual link consumed two “live” IP addresses. Incorporation of multiple redundant links as in a mesh topology (Figure 2) improved the overall internetwork's reliable availability but consumed ever larger numbers of “live” IP addresses which were fast becoming very hard to come by. This depletion of the available “live” IP address pool is one of the main reasons that we are currently transitioning to IPv6.

The practical establishment of an organization-wide mesh topology network is therefore economically and administratively unrealistic. The result was that in practice, organizations would establish up to three point-to-point links per site thereby providing redundancy of connectivity. Should any one link be disrupted the site could still communicate via the other links; albeit in a circuitous manner. The message still got through.

A Cooperative Model

Moving beyond a single enterprise desiring full-time interconnectivity the picture immediately increases in complexity. Now either every organization has its own routers connecting to the shared internetwork or some organizations could cooperatively share internetwork connected routers as their “gateway” to the internetwork. For a fee of course (see Figure 3 below).

The technical term for cooperative tariff-free network access and IP transit arrangements between different organizations (or even individuals) is peering.

Due to its numerous different forms, details, characteristics and manifestations peering warrants an article unto itself. Similarly, the Internet Service Provider (ISP) Tier system merits further investigation. However, due to the tight relationships between the two (ISP tiers and ISP peering) I will collectively cover them both in another article entitled Internet Service Providers (ISPs) Tiers and Peering.

Jumping forward in time for a moment, we find that for the Internet of today a modified cooperative model has won. Special organizations known as Internet Service Providers (ISPs) have their own Internet internetwork connected routers and the rest of us enter into an agreement with the ISP to gain usage rights for Internet access via their (our IPS's) Internet internetwork connected routers (see Figure 3 above).

Internet Backbone Topology

Right from the outset, the Internet in the USA has always used a backbone topology, with the original backbone network infrastructure being provided by the National Science Foundation Network (NSFNET). This structure was eventually privatised in 1995 when a variety of commercial organizations, known as Network Service Providers (NSPs) collectively took over the backbone functionality.

Note that in most parts of the world today (including Australia and the USA) these original Internet backbone provisioning and support NSPs are now referred to as Tier 1Internet Service Providers (ISPs). As I will discuss shortly; very similar structures, circumstances, peering arrangements and relationships between the Tier 1 ISPs exist in practically every Internet connected country, at least at their local national level.

Internet Exchange Points (IX or IXP)

One particularly important and pervasive characteristic of the Internet that also occurs at the local, national and the global levels is that geographically speaking Tier 1 ISPs interconnect with the Internet backbone and each other at various clearly defined and readily distinguishable physical locations throughout the Internet backbone (see Figure 4).

Originally, these Internet backbone access and ISP interconnectivity points were known as Network Access Points (NAPs). However, the term Network Access Point (NAP) is no longer used in this context. Rather, the name commonly given to the physical locations at which Tier 1 ISP Internet backbone interconnections occur today is Internet Exchange Points (IX or IXP) (see Figure 4).

Note that although the term Network Access Point (NAP) is still in common use today it now refers not to the Internet backbone access points but to those points at which users access their local network. This may be a home or corporate LAN, MAN, WAN or even a public wireless hot-spot. In fact any point at which individuals access a network is considered to be a network access point.

As one would expect either certain cooperative arrangements (peering) or very complex financial schemes exist between the various Tier 1 ISPs. I will be discussing these arrangements and Tier 2 and Tier 3 ISPs in another article so I won't delve into this aspect any further at this point. Suffice to say that on the global stage the Internet is built around the same type of backbone structure with discrete Tier1 ISP access via Internet Exchange Points (IX or IXP).

ISP Point of Presence (POP)

An ISP has a Point of Presence (POP) at a physical location if its customers can connect to it at that location. This holds true regardless of which tier that ISP may be classified as belonging to or which level of the Internet structure or local hierarchy we are discussing.

Local Conditions and Network Evolution

As an example of the changes and local conditions that may prevail in different geographical locations from time to time I will use the Australian case as this is somewhat easier to grasp and illustrate being a one-country continent even though the distinctions between Tier 1, Tier 2 and Tier 3 ISPs are somewhat blurry.

Back in 1990 the Australian Academic and Research Network (AARNet) was established to connect all Australian universities and a number of research institutions. The first AARNet implementation involved a state-level router in each Australian State capital city. These routers were connected to the main AARNet hub router in Melbourne by way of expensive leased-line services. An additional leased-line was used to link the Melbourne-based hub router to the USA.

AARNet retained ownership of all of the routers and the provision of basic carriage services was the only involvement of Telstra, the telecommunications provider at the time. Thus, Internet access between Australian universities more or less followed the cooperative model as already discussed above.

This expensive to maintain and run architecture has now been replaced by a far more economical one where an ISP (C & W Optus in this case) interconnects all state regional networks to each other as well as to the publicly accessible Australian and International Internet.

In this example we see a relatively expensive private hybrid tree/star topology network based upon point-to-point connections being replaced by a far more economical publically accessible commercial backbone-based topology internetwork.

Endpoint Connectivity and Presence

While the Internet backbone is a highly structured, ordered and persistently stable component of the global internetwork, the terminal networks, user nodes and other endpoints connecting to it are free to come and go as intermittently as they please. It is merely a matter of convenience or of a fiscally driven e-commerce desirability that sees most broadband Internet connections being “always on”.

Beyond Terra Firma and into the Future

As already noted Internet access is available onboard the International Space Station (ISS). What is not so well known is the degree to which traditionally Earth-bound communications and networking technologies and devices such as routers and switches are leaving the confines of terra firma and making the transition to space; thereby becoming truly universal infrastructure devices.

To illustrate just how much these unified communications and networking technologies are extending their reach far beyond terra firma, the Japanese have recently launched an ATM switch onboard a communications satellite.

The idea being to perform the switching functions in situ (in space) rather than beaming signals from earth-bound handsets up to the satellite, down to a ground-based exchanges for switching, then back up to the satellite for final relay back down to the intended earth-bound recipient. Compare this to the efficiency of a caller beaming the signal directly to the satellite where onboard switching takes place and the signal will then be transmitted directly to the intended recipient.

With the continuing evolution of converged unified communications and networking technologies and functionalities such as Voice over Internet Protocol (VoIP) this trend will not only continue into the foreseeable future but accelerate exponentially.

Further Reading, Additional Links and Resources:

• Wide Area Networks (WAN)
• Asynchronous Transfer Mode (ATM)
• IP Transit