2.6 Internet Standards

     

This book discusses several application-layer Internet protocols, most notably HTTP. However, this is not a book about those protocols and it tries not to say more than the minimum you need to know. If you need detailed information about any protocol, the definitive source is the standards document for the protocol.

While there are many standards organizations in the world, the two that produce most of the standards relevant to network programming and protocols are the Internet Engineering Task Force (IETF) and the World Wide Web Consortium (W3C). The IETF is a relatively informal, democratic body open to participation by any interested party. Its standards are based on "rough consensus and running code" and tend to follow rather than lead implementations . IETF standards include TCP/IP, MIME, and SMTP. The W3C, by contrast, is a vendor organization, controlled by dues-paying member corporations, that explicitly excludes participation by individuals. For the most part, the W3C tries to define standards in advance of implementation. W3C standards include HTTP, HTML, and XML.

2.6.1 IETF RFCs

IETF standards and near-standards are published as Internet drafts and requests for comments (RFCs). RFCs and Internet drafts range from informational documents of general interest to detailed specifications of standard Internet protocols like FTP. RFCs that document a standard or a proposed standard are published only with the approval of the Internet Engineering Steering Group (IESG) of the IETF. All IETF approved standards are RFCs, but not all RFCs are IETF standards. RFCs are available from many locations on the Internet, including http://www.faqs.org/rfc/ and http://www.ietf.org/rfc.html. For the most part RFCs, particularly standards-oriented RFCs, are very technical, turgid, and nearly incomprehensible. Nonetheless, they are often the only complete and reliable source of information about a particular protocol.

Most proposals for a standard begin when a person or group gets an idea and builds a prototype. The prototype is incredibly important. Before something can become an IETF standard, it must actually exist and work. This requirement ensures that IETF standards are at least feasible , unlike the standards promulgated by some other organizations. If the prototype becomes popular outside its original developers and if other organizations begin implementing their own versions of the protocol, a working group may be formed under the auspices of the IETF. This working group attempts to document the protocol in an Internet-Draft . Internet-Drafts are working documents and change frequently to reflect experience with the protocol. The experimental implementations and the Internet-Draft evolve in rough synchronization, until eventually the working group agrees that the protocol is ready to become a formal standard. At this point, the proposed specification is submitted to the IESG.

The proposal goes through six states or maturity levels as it follows the standardization track:

  • Experimental

  • Proposed standard

  • Draft standard

  • Standard

  • Informational

  • Historic

For some time after the proposal is submitted, it is considered experimental . The experimental stage does not imply that the protocol is not solid or that it is not widely used; unfortunately , the standards process usually lags behind de facto acceptance of the standard. If the IESG likes the experimental standard or it is in widespread use, the IESG will assign it an RFC number and publish it as an experimental RFC, generally after various changes.

If the experimental standard holds up well in further real world testing, the IESG may advance it to the status of proposed standard . A proposed standard is fairly loose, and is based on the experimental work of possibly as little as one organization. Changes may still be made to a protocol in this stage.

Once the bugs appear to have been worked out of a proposed standard and there are at least two independent implementations, the IESG may recommend that a proposed standard be promoted to a draft standard . A draft standard will probably not change too much before eventual standardization unless major flaws are found. The primary purpose of a draft standard is to clean up the RFC that documents the protocol and make sure the documentation conforms to actual practice, rather than to change the standard itself.

When a protocol completes this, it becomes an official Internet standard . It is assigned an STD number and is published as an STD in addition to an RFC. The absolute minimum time for a standard to be approved as such is 10 months, but in practice, the process almost always takes much longer. The commercial success of the Internet hasn't helped, since standards must now be worked out in the presence of marketers, vulture capitalists, lawyers , NSA spooks, and others with vested interests in seeing particular technologies succeed or fail. Therefore, many of the "standards" that this book references are in either the experimental, proposed, or draft stage. As of publication, there are over 3,800 RFCs. Less than one hundred of these have become STDs, and some of those that have are now obsolete. RFCs relevant to this book are detailed in Table 2-2.

Some RFCs that do not become standards are considered informational ,. These include RFCs that specify protocols that are widely used but weren't developed within the normal Internet standards track, and haven't been through the formal standardization process. For example, NFS, originally developed by Sun, is described in the informational RFC 1813. Other informational RFCs provide useful information (like users' guides), but don't document a protocol. For example, RFC 1635, How to Use Anonymous FTP , is an informational RFC.

Finally, changing technology and increasing experience renders some protocols and their associated RFCs obsolete. These are classified as historic . Historic protocols include IMAP3 (replaced by IMAP4), POP2 (replaced by POP3), and Remote Procedure Call Version 1 ( replaced by Remote Procedure Call Version 2).

In addition to its maturity level, a protocol has a requirement level. The possible requirement levels are:


Not recommended

Should not be implemented by anyone .


Limited use

May have to be implemented in certain unusual situations but won't be needed by most hosts . Mainly these are experimental protocols.


Elective

Can be implemented by anyone who wants to use the protocol. For example, RFC 2045, Multipurpose Internet Mail Extensions , is a Draft Elective Standard.


Recommended

Should be implemented by Internet hosts that don't have a specific reason not to implement it. Most protocols that you are familiar with (like TCP and UDP, SMTP for email, Telnet for remote login, etc.) are recommended.


Required

Must be implemented by all Internet hosts. There are very few required protocols. IP itself is one (RFC 791), but even protocols as important as TCP or UDP are only recommended. A standard is only required if it is absolutely essential to the functioning of a host on the Internet.

Table 2-2 lists the RFCs and STDs that provide formal documentation for the protocols discussed in this book.

Table 2-2. Selected Internet RFCs

RFC

Title

Maturity level

Requirement level

Description

RFC 3300

STD 1

Internet Official Protocol Standards

Standard

Required

Describes the standardization process and the current status of the different Internet protocols.

RFC 1122

RFC 1123

STD 3

Host Requirements

Standard

Required

Documents the protocols that must be supported by all Internet hosts at different layers (data link layer, IP layer, transport layer, and application layer).

RFC 791

RFC 919

RFC 922

RFC 950

STD 5

Internet Protocol

Standard

Required

The IP internet layer protocol.

RFC 768

STD 6

User Datagram Protocol

Standard

Recommended

An unreliable, connectionless transport layer protocol.

RFC 792

STD 5

Internet Control Message Protocol (ICMP)

Standard

Required

An internet layer protocol that uses raw IP datagrams but is not supported by Java. Its most familiar use is the ping program.

RFC 793

STD 7

Transmission Control Protocol

Standard

Recommended

A reliable, connection-oriented, streaming transport layer protocol.

RFC 2821

Simple Mail Transfer Protocol

Proposed standard

Recommended

The application layer protocol by which one host transfers email to another host. This standard doesn't say anything about email user interfaces; it covers the mechanism for passing email from one computer to another.

RFC 822

STD 11

Format of Electronic Mail Messages

Standard

Recommended

The basic syntax for ASCII text email messages. MIME is designed to extend this to support binary data while ensuring that the messages transferred still conform to this standard.

RFC 854

RFC 855

STD 8

Telnet Protocol

Standard

Recommended

An application-layer remote login service for command-line environments based around an abstract network virtual terminal (NVT) and TCP.

RFC 862

STD 20

Echo Protocol

Standard

Recommended

An application-layer protocol that echoes back all data it receives over both TCP and UDP; useful as a debugging tool.

RFC 863

STD 21

Discard Protocol

Standard

Elective

An application layer protocol that receives packets of data over both TCP and UDP and sends no response to the client; useful as a debugging tool.

RFC 864

STD 22

Character Generator Protocol

Standard

Elective

An application layer protocol that sends an indefinite sequence of ASCII characters to any client that connects over either TCP or UDP; also useful as a debugging tool.

RFC 865

STD 23

Quote of the Day

Standard

Elective

An application layer protocol that returns a quotation to any user who connects over either TCP or UDP and then closes the connection.

RFC 867

STD 25

Daytime Protocol

Standard

Elective

An application layer protocol that sends a human-readable ASCII string indicating the current date and time at the server to any client that connects over TCP or UDP. This contrasts with the various NTP and Time Server protocols, which do not return data that can be easily read by humans .

RFC 868

STD 26

Time Protocol

Standard

Elective

An application layer protocol that sends the time in seconds since midnight, January 1, 1900 to a client connecting over TCP or UDP. The time is sent as a machine-readable, 32-bit signed integer. The standard is incomplete in that it does not specify how the integer is encoded in 32 bits, but in practice a two's complement, big-endian integer is used.

RFC 959

STD 9

File Transfer Protocol

Standard

Recommended

An optionally authenticated, two-socket application layer protocol for file transfer that uses TCP.

RFC 977

Network News Transfer Protocol

Proposed standard

Elective

The application layer protocol by which Usenet news is transferred from machine to machine over TCP; used by both news clients talking to news servers and news servers talking to each other.

RFC 1034

RFC 1035

STD 13

Domain Name System

Standard

Recommended

The collection of distributed software by which hostnames that human beings can remember, like www.oreilly.com, are translated into numbers that computers can understand, like 198.112.208.11. This STD defines how domain name servers on different hosts communicate with each other using UDP.

RFC 1112

Host Extensions for IP Multicasting

Standard

Recommended

The internet layer methods by which conforming systems can direct a single packet of data to multiple hosts. This is called multicasting; Java's support for multicasting is discussed in Chapter 14.

RFC 1153

Digest Message Format for Mail

Experimental

Limited use

A format for combining multiple postings to a mailing list into a single message.

RFC 1288

Finger Protocol

Draft standard

Elective

An application layer protocol for requesting information about a user at a remote site. It can be a security risk.

RFC 1305

Network Time Protocol (Version 3)

Draft standard

Elective

A more precise application layer protocol for synchronizing clocks between systems that attempts to account for network latency.

RFC 1738

Uniform Resource Locators

Proposed standard

Elective

Full URLs like http://www.amnesty.org/ and ftp://ftp. ibiblio .org/pub/multimedia/chinese-music/Dream_Of_Red_Mansion/HLM04 .Handkerchief.au .

RFC 1808

Relative Uniform Resource Locators

Proposed standard

Elective

Partial URLs like /javafaq/books/ and ../examples/07/index.html used as values of the HREF attribute of an HTML A element.

RFC 1939

STD 53

Post Office Protocol, Version 3

Standard

Elective

An application-layer protocol used by sporadically connected email clients such as Eudora to retrieve mail from a server over TCP.

RFC 1945

Hypertext Transfer Protocol (HTTP 1.0)

Informational

N/A

Version 1.0 of the application layer protocol used by web browsers talking to web servers over TCP; developed by the W3C rather than the IETF.

RFC 2045

RFC 2046

RFC 2047

Multipurpose Internet Mail Extensions

Draft standard

Elective

A means of encoding binary data and non-ASCII text for transmission through Internet email and other ASCII-oriented protocols.

RFC 2068

Hypertext Transfer Protocol (HTTP 1.1)

Proposed standard

Elective

Version 1.1 of the application layer protocol used by web browsers talking to web servers over TCP.

RFC 2141

Uniform Resource Names (URN) Syntax

Proposed standard

Elective

Similar to URLs but intended to refer to actual resources in a persistent fashion rather than the transient location of those resources.

RFC 2373

IP Version 6 Addressing Architecture

Proposed standard

Elective

The format and meaning of IPv6 addresses.

RFC 2396

Uniform Resource Identifiers (URI): Generic Syntax

Proposed standard

Elective

Similar to URLs but cut a broader path . For instance, ISBN numbers may be URIs even if the book cannot be retrieved over the Internet.

RFC 3501

Internet Message Access Protocol Version 4rev1

Proposed standard

Elective

A protocol for remotely accessing a mailbox stored on a server including downloading messages, deleting messages, and moving messages into and out of different folders.


The IETF has traditionally worked behind the scenes, codifying and standardizing existing practice. Although its activities are completely open to the public, it's traditionally been very low-profile. There simply aren't that many people who get excited about the details of network arcana like the Internet Gateway Message Protocol (IGMP). The participants in the process have mostly been engineers and computer scientists, including many from academia as well as the corporate world. Consequently, despite often vociferous debates about ideal implementations, most serious IETF efforts have produced reasonable standards.

Unfortunately, that can't be said of the IETF's efforts to produce web (as opposed to Internet) standards. In particular, the IETF's early effort to standardize HTML was a colossal failure. The refusal of Netscape and other key vendors to participate or even acknowledge the process was a crucial problem. That HTML was simple enough and high-profile enough to attract the attention of assorted market-droids and random flamers didn't help matters either. Thus, in October 1994 the World Wide Web Consortium was formed as a vendor-controlled body that might be able to avoid the pitfalls that plagued the IETF's efforts to standardize HTML and HTTP.

2.6.2 W3C Recommendations

Although the W3C standardization process is similar to the IETF process (a series of working drafts hashed out on mailing lists resulting in an eventual specification), the W3C is a fundamentally different organization. Whereas the IETF is open to participation by anyone, only corporations and other organizations may become members of the W3C. Individuals are specifically excluded. Furthermore, although nonprofit organizations like the World Wide Web Artists Consortium (WWWAC) may join the W3C, only the employees of these organizations may participate in W3C activities. Their volunteer members are not welcome. Specific individual experts are occasionally invited to participate on a particular working group even though they are not employees of a W3C member company. However, the number of such individuals is quite small relative to the number of interested experts in the broader community. Membership in the W3C costs $50,000 a year ($5,000 a year for nonprofits) with a minimum 3-year commitment. Membership in the IETF costs $0 a year with no commitment beyond a willingness to participate. And although many people participate in developing W3C standards, each standard is ultimately approved or vetoed by one individual, W3C director Tim Berners-Lee. IETF standards are approved by a consensus of the people who worked on the standard. Clearly, the IETF is a much more democratic (some would say anarchic) and open organization than the W3C.

Despite the W3C's strong bias toward the corporate members that pay its bills, it has so far managed to do a better job of navigating the politically tricky waters of Web standardization than the IETF. It has produced several HTML standards, as well as a variety of others such as HTTP, PICS, XML, CSS, MathML, and more. The W3C has had considerably less success in convincing vendors like Netscape and Microsoft to fully and consistently implement its standards.

The W3C has five basic levels of standards:


Note

A note is generally one of two things: either an unsolicited submission by a W3C member (similar to an IETF Internet draft) or random musings by W3C staff or related parties that do not actually describe a full proposal (similar to an IETF informational RFC). Notes will not necessarily lead to the formation of a working group or a W3C recommendation.


Working drafts

A working draft is a reflection of the current thinking of some (not necessarily all) members of a working group. It should eventually lead to a proposed recommendation, but by the time it does so it may have changed substantially.


Candidate recommendation

A candidate recommendation indicates that the working draft has reached consensus on all major issues and is ready for third-party comment and implementations. If the implementations do not uncover any obstructions, the spec can be promoted to a proposed recommendation.


Proposed recommendation

A proposed recommendation is mostly complete and unlikely to undergo more than minor editorial changes. The main purpose of a proposed recommendation is to work out bugs in the specification document rather than in the underlying technology being documented.


Recommendation

A recommendation is the highest level of W3C standard. However, the W3C is very careful not to actually call this a "standard" for fear of running afoul of antitrust statutes. The W3C describes a recommendation as a "work that represents consensus within W3C and has the Director's stamp of approval. W3C considers that the ideas or technology specified by a Recommendation are appropriate for widespread deployment and promote W3C's mission."

The W3C has not been around long enough to develop a need for a historical or informational standard status. Another difference the IETF and the W3C is that the W3C process rarely fails to elevate a standard to full recommendation status once work has actively commencedthat is, once a working group has been formed. This contrasts markedly with the IETF, which has more than a thousand proposed and draft standards, but only a few dozen actual standards.

PR Standards

In recent years , companies seeking a little free press or perhaps a temporary boost to their stock price have abused both the W3C and IETF standards processes. The IETF will accept a submission from anyone, and the W3C will accept a submission from any W3C member. The IETF calls these submissions "Internet drafts" and publishes them for six months before deleting them. The W3C refers to such submissions as " acknowledged submissions" and publishes them indefinitely. However, neither organization actually promises to do more than acknowledge receipt of these documents. In particular, they do not promise to form a working group or begin the standardization process. Nonetheless, press releases invariably misrepresent the submission of such a document as a far more significant event than it actually is. PR reps can generally count on suckering at least a few clueless reporters who aren't up to speed on the intimate details of the standardization process. However, you should recognize these ploys for what they are.




Java Network Programming
Java Network Programming, Third Edition
ISBN: 0596007213
EAN: 2147483647
Year: 2003
Pages: 164

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