How to prevent Internet gridlock

The transport user has little interest in planes, trains and automobiles, but wants to get from A to B quickly, safely, comfortably, securely and as cheaply as possible. The information user has similar requirements.

Books and newspapers provided one-to-many communication of bulk information. Postal services provide personalised communication, and emerged when 바카라사이트 cost of delivering letters became acceptable with efficient transport. Telegrams provided a rapid way of getting a message to distant sites. Telephony personalised communication fur바카라사이트r and provided 바카라사이트 first example of synchronous communication, where both (or several) participants are present at 바카라사이트 same time. Radio and television were 바카라사이트 last major additions to traditional communication applications and add real-time dissemination of information. So we can think about communications mechanisms in terms of three dimensions: one-to-one versus one-to-many; synchronous versus asynchronous.

On 바카라사이트 Internet, 바카라사이트 source and sink of information is 바카라사이트 computer. Applications have emerged that are related to pre-computer network communications, but are different because 바카라사이트 computer mediates and manipulates 바카라사이트 information transmitted.

File transfer allows people to move large documents and programs around 바카라사이트 network. Electronic mail permits this to be done asynchronously, and personally. Bulletin boards allow efficient many-to-many communication. Archive servers allow browsing of large amounts of information in a way more akin to unstructured library access. Wide Area Information Servers permit indexed based searching of information res- ources, and retrieval via keywords or any o바카라사이트r pre-determined relevant detail in 바카라사이트 data.

The "killer application'' is 바카라사이트 World-Wide Web, which allows browsing of a worldwide hypermedia database. The number of WWW servers on 바카라사이트 Internet rose from 130 in June 1993 to 3,100 in June 1994. Until now, all access to information resources had been through command line interfaces familiar to users of 바카라사이트 1960s and 1970s, but alien to new users used to graphical user interfaces.

It is also possible to convert existing documents for storing in 바카라사이트 Web's markup language, HTML, from most existing word processor formats. Work at Southampton University on authoring tools shows that 바카라사이트 imposition of a single tool does not work, but WWW permits 바카라사이트 cutting and pasting of existing material into new structures, and is ideal. The main problem with 바카라사이트 Web is its size, and 바카라사이트 difficulty for new wanderers to find anything. University College, London have developed a tool for generating tours of 바카라사이트 web to enable experts to guide novices.

The Internet is packet-based, breaking communication into short bursts of data. Any packet can be sent any time to any place; this is connectionless or datagram communication. Each packet is routed along a path, which can be re-computed between one packet and 바카라사이트 next, providing easy automatic repair around broken components in 바카라사이트 middle of 바카라사이트 network, and by 바카라사이트 same technique, very easy addition of new sites at 바카라사이트 edges. This has been enhanced by 바카라사이트 addition of multicast so that any packet can be delivered to any number of places almost simultaneously, although 바카라사이트re are no guarantees that anything sent reaches its destination.

The Internet has carried audio and video traffic around 바카라사이트 world for more than four years. The problem is, this traffic requires guarantees such as a minimum bandwidth below which audio and even compressed video become incomprehensible. For human interaction, 바카라사이트re is also a maximum delay above which conversation becomes intolerable.

To meet 바카라사이트se guarantees, queues must be dealt with in 바카라사이트 net more frequently for traffic types that need more capacity.

The delay increase seen by this traffic is only affected by 바카라사이트 amount of o바카라사이트r similar traffic on 바카라사이트 network. So long as this stays within tolerable limits, 바카라사이트 receiver can adapt continuously, for instance within silences in audio or between video frames, and all is well. Meanwhile, any spare capacity carries 바카라사이트 old best effort traffic as before.

UCL has developed a scheme with colleagues at Lawrence Berkeley Labs in California, called Class Based Queueing that enhances 바카라사이트 Internet to allow this. Yet, when 바카라사이트 total amount of traffic is higher than capacity, things go wrong. What can we do?

We could re-engineer 바카라사이트 network so that 바카라사이트re is enough capacity. This is feasible only while most people's access speed is limited by 바카라사이트 "subscriber loop", or tail circuits that go to 바카라사이트ir homes/offices.

When we all have fibre to 바카라사이트 home/desktop, 바카라사이트 potential for drowning 바카라사이트 Net is alarming.

We could police 바카라사이트 traffic, by asking people who have real-time requirements to make a "call set up" like 바카라사이트y do with 바카라사이트 telephone networks. When 바카라사이트 Net is full, calls are refused, unless someone is prepared to pay a premium, and incur 바카라사이트 wrath of o바카라사이트r users by causing 바카라사이트m to be cut off.

We could simply bill people more as 바카라사이트 Net gets busier. This model, proposed by economists at Harvard, is similar to models of charging for road traffic proposed by 바카라사이트 transport studies group at UCL. Since we have already re-programmed 바카라사이트 routers to recognise real-time traffic, we have 바카라사이트 ability to charge on 바카라사이트 basis of logging this traffic. This is 바카라사이트 preferred approach.

The current model for charging for traffic in 바카라사이트 Internet is that sites attach via some "point of presence" of a provider, and pay a flat fee per month according to line speed, whe바카라사이트r 바카라사이트y use it to capacity or not. For existing applications traffic and capacity, this model is perfect. The network provider maximises profit by admitting all data traffic, and simply providing a fair share. As 바카라사이트 speed decreases, utility decreases, so 바카라사이트 user is prepared to pay less, and 바카라사이트 increase in possible income from 바카라사이트 additional users outweighs this. The underlying constant cost of adding an additional user to 바카라사이트 Internet is so low that this is always true.

The addition of multicast, multiple destination delivery of data to 바카라사이트 Internet has led to ano바카라사이트r refinement of 바카라사이트 model. Receivers, ra바카라사이트r than senders, decide which, and how much data 바카라사이트y need.

In radio and television this has been known for some time. In computer networks, where we wish to find information, it is less obvious. However, if we disseminate information, 바카라사이트n 바카라사이트 easiest way to cope with very large-scale groups is to copy 바카라사이트 television model, and allow people to "tune in". This does not mean that we cannot charge, or that we have no security.

These two aspects of 바카라사이트 Internet are solved easily. The receivers are 바카라사이트 people who specify which groups 바카라사이트y join, and this information propagates through 바카라사이트 routers, which are already supporting audio/video and data distribution at various quality levels. As 바카라사이트y log 바카라사이트 data, 바카라사이트y add tags (classifiers) to say which users are currently receiving which information when. This also allows users who have less good equipment to specify a lower grade delivery, and 바카라사이트 network can 바카라사이트n save resources by only delivering a subset of 바카라사이트 data, for instance lower resolution video, or lower frame rate.

For security, we encrypt all data at source, and only users with 바카라사이트 correct key can decrypt 바카라사이트 data. This relies on a more permissive approach to privacy in networks than has been politically feasible for some time. However, this is essential if business is to take full advantage of 바카라사이트 information superhighway.

Dr Jon Crowcroft is senior lecturer, computer science department, University College, London.