Charles M. Kozierok The TCP-IP Guide

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shared access medium. As the use of switches has increased, allowing dedicated

bandwidth to each computer, full-duplex operation has become very popular. Full-duplex

operation in Ethernet not only allows the simultaneous transmission of data in both direc-

tions, it also eliminates contention for the formerly shared access medium—no more

collisions. The combination of these two effects improves performance, sometimes

substantially.

Key Concept: There are three basic operating modes that describe how data is sent

between connected devices on a network. In simplex operation, data can flow in only

one direction between two devices. Half-duplex networks allow any device to

transmit, but only one may do so at a time. Full-duplex operation means two attached

devices can each transmit and receive simultaneously—this offers the greatest potential

performance, since throughput is not decreased by forcing one device to wait for another

before sending data.

Quality of Service (QoS)

I mentioned in my discussion of common network performance measurements that there

were many different aspects to network performance. I also introduced the concept of

latency, which measures how long it takes for data to travel across a network. Latency is

one important part of a larger issue in networking that is sometimes called quality of service

or QoS.

The inherent nature of most networking technologies is that they are more concerned with

pumping data from one place to another as fast as possible than they are with how the data

is sent. For example, the Internet is designed on top of the Internet Protocol, a packet-

switching technology that is designed to get packets from point “A” to point “B” in whatever

way is most effective, without the user necessarily having any ability to know what route will

be taken. In fact, some packets in the same data stream may be sent along different routes.

Packets may be stored for a while before being forwarded to their destination, or even

dropped and retransmitted.

For most applications, such as simple file or message transfers, this is perfectly fine.

However, there are applications where this sort of service is simply of “too low quality”. In

these cases, the nature of how the data is delivered is more important than merely how fast

it is, and there is a need for technologies or protocols that offer “quality of service”. This

general term can encompass a number of related features; common ones include the

following:

☯ Bandwidth Reservation: The ability to reserve a portion of bandwidth in a network or

interface for a period of time, so that two devices can count on having that bandwidth

for a particular operation. This is used for multimedia applications where data must be

streamed in real-time and packet rerouting and retransmission would result in

problems. This is also called resource reservation.

☯ Latency Management: A feature that limits the latency in any data transfer between

two devices to a known value.

☯ Traffic Prioritization: In conventional networks, “all packets are created equal”. A

useful QoS feature is the ability to handle packets so that more important connections

receive priority over less important one.

☯ Traffic Shaping: This refers to the use of buffers and limits that restrict traffic across a

connection to be within a pre-determined maximum.

☯ Network Congestion Avoidance: This QoS feature refers to monitoring particular

connections in a network, and rerouting data when a particular part of the network is

becoming congested.

So, in essence, quality of service in the networking context is analogous to quality of service

in the “real world”. It is the difference between getting take-out and sit-down service at a

nice French restaurant—both cure the hunger pangs, but they meet very different needs.

Some applications, especially multimedia one such as voice, music and video, are time-

dependent and require a constant flow of information more than raw bandwidth; for these

uses, a burger and fries in a paper bag just won’t cut the mustard. ☺

Key Concept: The generic term quality of service describe the characteristics of

how data is transmitted between devices, rather than just how quickly it is sent.

Quality of service features seek to provide more predictable streams of data rather

than simply faster ones. Examples of such features include bandwidth reservation, latency

minimums, traffic prioritization and shaping, and congestion limitation. Quality of service is

more important for specialty applications such as multimedia than for routine applications

such as those that transfer files or messages.

To support quality of service requirements, many newer technologies have been developed

or enhanced to add quality of service features to them. This includes the ability to support

isochronous transmissions, where devices can reserve a specific amount of bandwidth over

time to support applications that must send data in real time. One technology that has

received a lot of attention for its quality of service features is Asynchronous Transfer Mode

(ATM). ATM is designed to support traffic management features that are not generally

available on networks not created to provide quality of service features (such as Ethernet)

Note: “Quality of service” has become a big buzzword, lately. By itself, this term

conveys about as much useful information about what the technology offers as

being told that it is “high performance”. You have to dig past the marketingspeak

and find out exactly what QoS features are being offered.

Network Standards and Standards Organizations

You can't study networking and its related technologies without very quickly encountering a

whole host of standards that are related to the subject—and organizations that create these

standards. Network standards facilitate the interoperability of network technologies and are

extremely important. It may be an exaggeration to say that networking wouldn't exist

without standards, but it isn’t to say that networking as we know it would not exist without

them. Networks are literally everywhere, and every hardware device or protocol is governed

by at least one standard, and usually many.

In this section I provide a brief examination of the often-overlooked subject of network

standards and standards organizations. I begin with a background discussion of why

standards are important, highlighting the differences between proprietary, de facto and

open standards. I give an overview of networking standards in general terms, and then

describe the most important international standards organizations and industry groups

related to networking. I then describe the structure of the organizations responsible for

Internet standards, including the registration authorities and registries that manage

resources such as addresses, domain names and protocol values. I conclude with a

discussion of the Request For Comment (RFC) process used for creating Internet

standards.

Proprietary, Open and De Facto Standards

Why are standards important? Well, because I said so. They are. Alright, fine, I'll try to do a

bit better than that; even my young kids won't take that for an answer any more. But I have

to warn you that the proper answer is a lot longer than the cute answer. ☺

An old saw in the computer world says that “the beauty of standards is that there are so

many to choose from”. This little joke reflects the frustration that technicians often feel at the

sheer number of standards that are found in the industry: thousands. Aside from differing in

terms of content—what technologies and protocols they describe—standards also often

differ in terms of the type of standards they are, and how they came about. In fact, part of

the reason why there are sometimes “so many to choose from” in a particular area is

because of how they come about.

Proprietary Standards

In the early days of computing, many people didn't quite understand just how important

universal standards were. Most companies were run by skilled inventors, who came up with

great ideas for new technologies and weren't particularly interested in sharing them. It

wasn't considered a “smart business move” to share information about new inventions with

other companies—the competition! Oh sure, every company believed that standards were

important, but they thought it was even more important that they be the ones to control

those standards.

I'll give you an example of what I mean. Let’s imagine that it's 1985, and I have just come up

with a great networking technology, which I have incorporated into a fancy new local area

networking product called “SooperDooperNet”. (Catchy, eh?) SooperDooperNet is my

product. I have patents on the technology, I control its design and manufacture, and I sure

as heck don't tell anyone else how it works—if I did, they would copy me, right?

Now, I could sell interface cards, cables and accessories for SooperDooperNet, and a

company that wanted to use it could install the cards in all of their PCs and be assured that

they would be able to talk to each other. This solves the interoperability problem for this

company by creating a “SooperDooperNet standard”. This would be an example of a propri-

etary standard—it's owned by one company or person.

The problem with proprietary standards is that other companies are excluded from the

standard development process, and therefore have little incentive to cooperate with the

standard owner. In fact, just the opposite: they have a strong motivation to develop a

competing proprietary standard, even if it doesn't improve on the existing one.

So when my competition sees what I am doing, he is not going to also create network

interface cards that can work with SooperDooperNet, which would require paying me a

royalty. Instead, he's going to develop a new line of networking hardware called MegaAwe-

someNet, which is very similar to SooperDooperNet in operation but uses different

connectors and cable and logic. He too will try to sell bunches of cards and cables—to my

customers, if possible!

You can see what the problem is here: the market ends up with different companies using

different products that can't interoperate. If you install SooperDooperNet, you have to come

to me for any upgrades or changes—you have no choices. Worse, what happens if Acme

Manufacturing, which has 50 PCs running SooperDooperNet, merges with Emca Manufac-

turing, which has 40 PCs running MegaAwesomeNet? Well, the IT people have a problem,

that's what. Sure, there would be ways to solve it, but wouldn't everyone be better off to just

avoid these difficulties in the first place? And how could you create something like the

Internet if everyone's networks used different “standards”?

Open Standards

Eventually, companies learned that they would be better off to have standards that

everyone agreed with, instead of constantly fighting with each other. This is particularly true

of networking, where devices need to talk to each other. If many companies get together

and agree to cooperate, they can create an open standard instead of a bunch of proprietary

ones. The name is rather self-explanatory; rather than being the closely-guarded secret of

one organization, and open standard is available to any who are interested in using it.

One key to the success of an open standard is a steering organization to promote it.

Usually, a neutral, non-profit trade association or working group is established to develop

and promote the standard, and the various for-profit hardware and software companies join

this group and support it financially. These groups also work with standards approval bodies

like the ITU and ISO to gain acceptance for their standards.

Of course, the companies aren't doing this just to be nice to their customers. In creating

open standards, they split the “market share pie” between them, but they make the pie grow

much larger by attracting more customers. Customers like open standards more than

proprietary ones, because they give them more choices, and increase their ability to interact

with other companies, troubleshoot problems, hire skilled workers, and expand in the future.

As for the companies, they still compete in their specific offerings, so it's not like they all end

up making the same products. For all of these reasons, open standards are now far more

common than proprietary ones.

However, the process involved in creating these standards is often a difficult one. In some

cases the standards organization will draft the standard from the ground up, but in others it

may select one technology as the basis for the standard from several that are submitted in

what is commonly called a “technology bake-off”. Thus, many different companies may

come to the table with different approaches, each of them vying for selection as the

standard for use by the group. Politics can cause groups to get bogged down for years

fighting over various options, or even to split into multiple groups. Good examples are what

occurred in the conflict between supporters of 100VG-AnyLAN and Fast Ethernet, and the

problems with standards politics that have plagued the world of powerline networking.

Furthermore, there are still some companies that believe strongly in proprietary standards,

because they really want to control and direct the market. One of the most famous/

infamous in this regard is Sony, a company that makes excellent hardware but frequently

refuses to accept established standards. For this reason, some people avoid their products,

even though they are good; because they want to stick to industry standards.

De Facto Standards

This brings me to the third type of standard that is often seen in the computer world: the de

facto standard. “De facto” is Latin for “in fact”, so a de facto standard is one that is used as

a universal standard just because over time it became widely used, and not because the

standard was developed and approved by a standards committee. A good example of a de

facto standard is the “AT” command set used by modems; virtually all modems use it, but

this resulted not from an industry group agreeing to adopt and deploy it. Rather, it was

developed unilaterally by Hayes, the pioneering modem company, and then adopted by

virtually every other modem maker until it became a standard.

One reason why proprietary standards are still sometimes seen is that some companies

want to produce a standard that will become so universally used that it becomes the de

facto standard, thus giving them a leadership position in that market. Again, in my

estimation Sony falls into this category—they often want to do things “their way” and create

proprietary standards that they try to promote using their powerful market presence.

Sometimes this succeeds but often it does not, resulting a fragmented market of incom-

patible products. An excellent example is when Sony created a new format for digital

camera flash memory (the “memory stick”) rather than using the CompactFlash format used

by other camera manufacturers. The result of this was not everyone using memory sticks

as Sony had hoped, but two incompatible standards that increase confusion and yield no

real benefit to the customer.

Key Concept: Networking standards can be classified as proprietary, open or de

facto. Proprietary standards are owned by one particular organization. If that organi-

zation has sufficient market clout and the industry lacks alternatives to its standard, it

may be adopted by the whole industry, becoming a de facto standard. Usually, however,

differing proprietary standards compete with each other, resulting in a fragmented market.

In contrast, open standards are not owned by anyone—they are created by neutral organi-

zations to ensure that compatible products can be designed and developed by many

different companies. This makes life easier for the customer as well as promoting the

market as a whole.

Networking Standards

All networking technologies have standards associated with them. These are usually highly

technical documents, and often presume that the reader has a fair bit of knowledge about

networking. If you aren't an expert, you will probably have some difficulty understanding

networking standards. (Some people seem to think I am an expert, but I too have trouble

with most of the details in a typical networking standard.)

In fact, many technologies have quite a number of standards associated with them. A

networking technology may have more than one standard for any or all of the following

reasons:

☯ The original standard has been revised or updated;

☯ The technology is sufficiently complex that it needs to be described in more than one

document;

☯ The technology borrows from or builds on documents used in related technologies;

☯ More than one organization has been involved in developing the technology.

Standards documents created in the United States are usually developed in English, but are

also routinely translated into other languages. European standards are often published

simultaneously in English, French and German, and perhaps other languages as well.

Today, virtually all networking standards are “open” standards, administered by a standards

organization or industry group. As I explained in the previous topic, open standards are

more popular than proprietary ones in the computer industry, and that's particularly so when

it comes to networking. In fact, the few technologies where there is no universally-accepted

open standard have been losing ground to those with open standards, particularly in the

areas of wireless LANs and home networking—pretty much proving how important an open

process really is.

I considered having a separate section where I listed all of the various standards used for

networking within the Guide. However, this would be a very large section indeed, and the

discussions of the various standards would be somewhat “detached” from the places where

I describe the technologies they define. Instead, I have many different smaller discussions

of standards, within the sections where I describe each networking method or protocol.

These can usually be found in an overview topic introducing each technology type, though

for more complex protocols I have a dedicated topic just discussing relevant standards and

where they are documented.

International Networking Standards Organizations

The rise of open standards not owned by any one company has been a great boon to

customers of computer and networking products, as well as the manufacturers that sell to

them. In order to facilitate the development of open standards, however, organizations are

needed that will coordinate the creation and publishing of these documents. Generally,

these are non-profit organizations that specifically take a neutral stance regarding technol-

ogies and work for the betterment of the industry as a whole.

Here are some of the standards organizations that you are likely to encounter when reading

about networking and the Internet:

☯ International Organization for Standardization (ISO): Probably the biggest

standards organization in the world, the ISO is really a federation of standards organi-

zations from dozens of nations. In the networking world, the ISO is best known for its

OSI Reference Model.

Note: The shortened name of the International Organization for Standardization is

indeed “ISO”, and not “IOS” as you might imagine. In fact, it is not an acronym at

all. Since the full name of the body differs from one language to the next, any

acronym for that name would differ as well. Instead, the organization chose the name “ISO”

from the Greek word “isos”, meaning “equal”. Many people, especially in the United States,

think “ISO” is short for “International Standards Organization”, but this is incorrect.

☯ American National Standards Institute (ANSI): ANSI is the main organization

responsible for coordinating and publishing computer and information technology

standards in the United States. While they are commonly thought of as developing and

maintaining standards, they do neither. Instead, they oversee and accredit the organi-

zations that actually create the standards, qualifying them as Standards Developing

Organizations or SDOs. ANSI also publishes the standards documents created by the

SDOs, and serves as the United States' representative to the ISO.

☯ Information Technology Industry Council (ITIC): ITIC is a group of several dozen

companies in the information technology (computer) industry. ITIC is the SDO

approved by ANSI to develop and process standards related to many computer-

related topics. It was formerly known as the Computer and Business Equipment

Manufacturers Association (CBEMA).

☯ National Committee for Information Technology (NCITS): A committee established

by the ITIC to develop and maintain standards related to the information technology

world. NCITS was formerly known by the name Accredited Standards Committee X3,

Information Technology, or more commonly, just X3. It maintains several sub-

committees that develop and maintain standards for various technical subjects.

☯ Institute of Electrical and Electronics Engineers (IEEE): The IEEE (pronounced

“eye-triple-ee”) is a well-known professional organization for those in the electrical or

electronics fields, including computers and networking. IEEE's main claim to fame in

the networking industry is the IEEE 802 Project, which encompasses many popular

networking technologies including Ethernet.

☯ Electronic Industries Alliance (EIA): The EIA is an international industry association

that is best known for publishing electrical wiring and transmission standards.

☯ Telecommunications Industry Association (TIA): The TIA is the communications

sector of the EIA, and is responsible for developing communications standards. Since

communications, wiring and transmission are all related, and since the TIA and EIA

organizations are also related, standards produced by the EIA or TIA are often labeled

with the combined prefixes “EIA/TIA” or “TIA/EIA”.

☯ International Telecommunication Union - Telecommunication Standardization

Sector (ITU-T): ITU-T is another large international body that develops standards for

the telecommunications industry. The ITU-T was formerly named the International

Telephone and Telegraph Consultative Committee or CCITT (the abbreviation was of

the French version of the organization's name, Comité consultatif international

téléphonique et télégraphique.)

☯ European Telecommunications Standards Institute (ETSI): An organization with

members from dozens of countries both within and outside Europe that is dedicated to

developing telecommunications standards for the European market (and elsewhere).

ETSI is known for, among other things, regulating the use of radio bandwidth in

Europe and developing standards such as HiperLAN.

This list represents some of the more important organizations that are responsible for

establishing and publishing standards in the networking world. It is not an exhaustive list,

however. I should also point out that the set of related organizations responsible for creating

Internet standards is not shown in this list as I have covered them in two dedicated topics

on Internet standards organizations and registration authorities.

I want to emphasize that many of the organizations above do not actually develop the

various standards. Generally, these are oversight organizations—“high level management”

if you will—that work with many other smaller groups who actually develop the standards.

Also, in many cases a particular standard may be published by more than one standards

organization, so it may be labeled with more than one name.

Key Concept: There are a number of well-known international organizations that

play an important role in the development of open networking standards. Some of

the most important of these are ISO, ANSI, ITIC, IEEE, EIA/TIA, ITU-T and ETSI.

These are oversight organizations, responsible for overall management of the standards

development process, rather than for the particulars of creating individual standards.

Networking Industry Groups

As I explained in the previous topic, most open standards are coordinated and published by

a small number of large, often international standards organizations. However, these are

not the only groups of people who are involved in the development of standards for

networking and Internet technologies. There are also many different networking industry

groups that play an important role in the standard creation process.

Networking industry groups differ in a few ways from standards organizations.They are

typically dedicated to the promotion of a specific technology, where standards organizations

are more generic and handle the oversight of hundreds of different ones. Industry groups

are also generally smaller than standards organizations, with members drawn primarily

from the field of developers and manufacturers that create products for the particular

technology the group promotes.

Perhaps most importantly, industry groups often actually write and maintain the standards,

where standards organizations are generally more “supervisors” who ensure that the

standards meet, well, the standards for the development of standards. Some industry

groups, however, are concerned only with marketing and promotion activities.

Obviously, these industry groups work closely together with the standards organizations. In

some cases, they may even be part of the same overall organization, and all of the different

groups are related in some ways. For example, the IEEE 802 project consists of a number

of working groups that are charged with maintaining and developing specific technology

standards, which the larger IEEE organization approves and publishes.

One of these working groups is the 802.11 working group, which develops wireless Ethernet

technology. At the same time that this group “does its thing”, there is an industry group

called the Wireless Ethernet Compatibility Alliance (WECA). This group works to ensure the

cross-vendor compatibility of 802.11b wireless networking hardware and software.

Other industry groups are formed specifically to develop independent standards that are not

approved through a formal standardization process. Examples include groups such as

HomePNA, IrDA and HomeRF. One of the problems with these groups is that they usually

do not make their standards open to the public. This is undoubtedly due to some sort of

security concern or desire to keep the “inner workings” of their technology “secret”.

Unfortunately for these groups, this policy harms the ability of regular people to learn about

how their technologies work. For example, in writing this and other reference works, I am

almost always unable to obtain specifications from most of the private industry groups.

They either refuse to allow me to get the document at all, or want to charge me a great deal

of money for the privilege (well into the thousands of dollars in some cases). In doing this,

these groups harm their own cause, by making it more difficult for those interested in their

technologies to learn about them. This is another key advantage of open standards

managed by public organizations such as ANSI or the IEEE.

Internet Standards Organizations (ISOC, IAB, IESG, IETF, IRSG,

IRTF)

High-quality, widely-accepted open standards become more important the larger the

number of people that use a network. The largest network of all is of course the Internet,

which connects millions of people on thousands of individual networks into a globe-

spanning internetwork. The Internet has revolutionized not only networking and computing,

but communication, business, and even society as a whole. One of the critical factors in the

success of the Internet has been its development using open standards.

Of course, nobody sat down one day and said “hey, let’s create the Internet!” (No, not even

Al Gore. ☺) It began as a small research network, and was developed over time concur-

rently with the technology set that implemented it: TCP/IP. At first, a relatively small

organization was sufficient to manage the development of Internet standards and oversee

its activities, but as the Internet continued to grow, this became inadequate. Eventually a

more formalized structure of organizations was required, to manage the Internet devel-

opment process and other activities to ensure the continued success and growth of the

Internet and the TCP/IP technologies that power it.

Today, there are six organizations that are responsible for the development of the Internet’s

architecture, standards and policies, and related activities. They are closely-related, with

certain organizations being responsible for oversight of others, as shown in Figure 7. These

organizations perform many tasks, and can be somewhat confusing to understand, since

many have similar-sounding names and responsibilities. Therefore, I will concentrate

mostly on their role in the development of Internet standards, since that is our primary

interest in this discussion.

Key Internet Standards Organizations

Here is a brief description, rather simplified, of the key Internet standards organizations:

☯ Internet Society (ISOC): A professional society responsible for general, high-level

activities related to the management, development and promotion of the Internet.

ISOC has thousands of individual and organizational members that engage in activ-

ities such as research, education, public policy development and standardization. It is

responsible for providing financial and administrative support to the other organiza-

tions listed below. From the standpoint of standards development, ISOC’s key role is

its responsibility for oversight of the IAB.