| RFC : | rfc1324 |
| Title: | |
| Date: | May 1992 |
| Status: | INFORMATIONAL |
Network Working Group D. Reed
Request for Comments: 1324 May 1992
A Discussion on Computer Network Conferencing
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard. Distribution of this memo is
unlimited.
Abstract
This memo is intended to make more people aware of the present
developments in the Computer Conferencing field as well as put
forward ideas on what should be done to formalize this work so that
there is a common standard for programmers and others who are
involved in this field to work with. It is also the intention of
this memo to stimulate the computer community and generate some
useful discussion about the merits of this field.
Introduction
Computer network conferencing is just now starting to grow and take
advantage of the modern technology that is available. Although there
are some systems which have been around for some time (BRC - Bitnet
Relay Chat and IRC - Internet Relay Chat), there has not been any
real move to bring them together under a single protocol. This has
led to various protocols and different systems coming to life. As
these different systems continue to pop up, it is becoming more
obvious that there is need of a standard in this area for developers
to follow without the need of worrying about protocol clashes.
In any implementation of a conferencing program, there are likely to
be two main components: (1) a client program or interface which users
enter commands into (hereafter referred to as a "client") and 2) a
server program which acts as a multiplexor for various clients which
connect to it. There are other expectations and requirements for both
servers and clients which are mentioned in more detail later.
Table of Contents
1.0 Network Conferencing Today........................... 2
1.1 Conferencing in general today........................ 2
1.2 Talk/phone vs. conferencing.......................... 3
1.3 Advantages of realtime network conferencing.......... 3
2.0 Goals for what a protocol should provide............. 4
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2.1 State Information problems........................... 4
2.2 Network barriers..................................... 4
2.3 User needs........................................... 4
2.3.1 User privacy......................................... 4
2.3.2 Realtime Expectations................................ 5
2.4 Message Delivery..................................... 5
2.4.1 Deficiencies in using IP only........................ 5
2.4.2 Flexibility.......................................... 5
2.4.3 Building a flexible transport protocol............... 5
2.5 Network Structure.................................... 5
2.5.1 Size................................................. 5
3.0 Usage................................................ 6
4.0 Setting it up........................................ 6
4.1 Installation......................................... 6
4.2 Controlling growth................................... 7
5.0 Finding the *right* protocol......................... 7
5.1 Name for protocol.................................... 7
5.2 Responsibilities of conference servers............... 7
5.2.1 Message passing...................................... 7
5.2.2 Who is on?........................................... 7
5.2.3 Who is who?.......................................... 8
5.2.4 Conference security.................................. 8
5.2.5 Error reporting...................................... 8
5.2.6 Network Friendliness................................. 8
5.2.7 To ASCII or not to ASCII............................. 8
5.2.8 Queries or messages to a server and replies.......... 9
5.3 Responsibilities of clients.......................... 9
5.3.1 Providing accurate information....................... 9
5.3.2 Client as servers.................................... 9
5.4 How complex should the protocol be?................. 10
5.4.1 User identification................................. 10
5.4.2 Trees and cycles.................................... 10
5.5 Protocol summary.................................... 10
6.0 Security Considerations............................. 10
7.0 Author's Address.................................... 11
1.0 NETWORK CONFERENCING TODAY
1.1 Conferencing in general today
Conferences today are an integral part of the business world in many
ways. A conference may be held to reassure staff about company
problems (boost moral) or may be held by a few directors in an
emergency situation where a carefully considered solution is needed.
Conferences also form the cornerstone of workshops held where various
groups of people, who attend, are to be briefed on new developments.
In nearly all of these situations, there will be a group of 2 or
more, where each speaks and listens to others. There exist PABXs and
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other features of the telephone system which provide for conferencing
between people around the globe at a cost effective rate. The only
place which really lacks any formal form of conferencing is the
internet, although many unofficial conferencing systems already
exist, spanning the globe or providing local forums.
1.2 Talk/phone vs. conferencing
To provide instantaneous communication between two users on unix and
other multiuser systems, interprocess communication is commonly used
either over a network or other local methods. The diversity of unix
platforms has introduced as many problems as the presence of various
operating systems on the net. Commonly, those on Unix based machines
are unable to talk to those on VMS or VM machines. The occasion even
arises where two Unix hosts are unable to talk to each other due to
different talk protocols.
1.3 Advantages of realtime computer conferencing
By providing a standard for computer conferencing, it should
eliminate the problem of who is using what computer. This will mean
that someone from a VMS or VM machine can talk with one or more
people without having to worry whether their counterpart has an
account on a compatible machine for their choice of communication.
Electronic mail (email) has already reached this position with most
modern mailers on the internet being compliant with RFC822. It is
therefore not unreasonable to expect this of realtime conferencing
which is to talk as USENet is to email; although of those four (4),
only email and news have been covered by RFCs.
USENet is a vast resource and immensely useful for many people around
the globe. It does, however suffer from a high noise to signal ratio.
It would be unwise to expect much difference in performance from
conferencing.
By providing the means for realtime computer conferencing, it opens
up a whole new area of usefulness to computers. For both students and
staff alike, it opens up new possibilities. In educational
institutions where there is a high level of project work with groups
of more than 2, it means that students can work from home or other
remote places and discuss their project with their fellow students in
a manner which would be similar to all students having a conventional
meeting or conference. This same situation also applies to staff
members. For those who have previously relied on email between
fellow researchers in many remote institutions, computer conferencing
brings the world together, onto the researchers screen where they can
trade ideas and code in real time. Traditionally to achieve these
goals, the phone would have been used and a teleconference setup and
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it will probably remain so for many years to come with video phones
too. However, with phone conferencing, when people talk over each
other, the quality of the discussion is degraded.
2.0 Goals for what a protocol should provide
In producing a protocol for conferencing over computer networks, the
following problems must be considered:
2.1 State Information problems
The number of users who are a part of the conference may fluctuate
continuously by a large amount over any given period of time. The
protocol should endevour to make disruptions such as these as smooth
as possible but at the same time, keep the realtime feel in the
conference. It is not acceptable to buffer a user who quits for any
given time but at the same time, if a server has network problems
with connecting to another one, it may be wise to find some way
around the continual stream of state messages that are passed - or -
at least a way to reduce the number.
2.2 Network barriers
Members of a conference may be on physical networks which cannot
directly communicate with each other, such as those used from a host
on a commercial network talking via a bridge to someone from a
network directly connected to a network directly accessible from
theirs. So in this case, the users involved have no need to directly
use the bridge (as required by unix talk) since the server on the
gateway host provides a way for messages to be passed in and out of
the unreachable sections. In this case also, there is a minimum
security risk to the network which is otherwise unreachable.
2.3 User needs
2.3.1 User privacy
Members of a conference may wish to exchange ideas privately without
fear of others eavesdropping or interrupting the current conference.
To facilitate this, there should be some support by the protocol to
pass messages from one user/client directly to another.
It is also reasonable for a user to want to be able to hide in one
way or another from other users, effectively making themself
invisible to other users.
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2.3.2 Realtime Expectations
Users will expect conferencing to be real time, giving the thereby
demanding that the protocol supply a quick, efficient, reliable and
accurate delivery of a message. Only when these requirements are met
can a conference system hope to be of any use to its users.
2.4 Message Delivery
2.4.1 Deficiencies in using IP only
In routing between conference servers, the problem of routing
messages is an important issue. If there was a server for the
conference at each domain, this wouldn't be an issue, one could
simply do some sort of lookup and find the server for it. This is not
the case and unless such a server becomes a standard item for unix
machines, it is not reasonable to expect it to ever be so. Thus the
need for a layer on top of TCP/IP is needed to deliver messages
between the servers for the conference.
2.4.2 Flexibility
The routing protocol used should not be inflexible and should allow
for routes to change over time in much the same way as RIP does now.
However, there is no need for a special routing protocol such as RIP
since this is already part of IP's functionality. Routing information
should be updated automatically when the server receives information
via that route whether it creates or destroys a route.
2.4.3 Building a flexible transport protocol on top of existing ones
If such a conferencing service is built upon TCP/IP, it is therefore
possible to build an abstract routing model which has no relation to
the TCP/IP model. However, it is not wise to ignore the presence of
either TCP or IP since by integrating them into the protocol, it is
easier to use their strengths. If the protocol relies too heavily on
TCP/IP features, it will also inherit some of its weaknesses. These
maybe taken for granted, but it is worth keeping them in mind when
designing a protocol to be both reliable, efficient and useful.
2.5 Network Structure
2.5.1 Size
The potential userbase of a conferencing system using the internet
should not be underestimated. It is therefore desirable that the
conferencing system should be as distributed as possible, and as
little state information kept as possible. If the IRC network is
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taken as a guide, with 800 users on 140 servers in some 200 channels,
the server was using over 1MB of memory. Due to the nature of
conferencing and the server being run as a daemon, this memory was
hardly ever swapped out. For this reason, servers should aim to only
be authoritive about required users, channels and servers and keep up
to date information on these.
There is also no requirement that a global conferencing system be
built, although it is an ideal arena to show the strengths of the
network. It also goes without saying that it shows up a lot of its
weaknesses too.
Any protocol which is developed should operate equally well and
efficiently on both a large scale network and on a small scale
network.
3.0 Usage
If past usage is any guide, then a network based conferencing system
will be largely used by mostly students. This is not as unreasonable
as it may sound since students and student accounts easily form the
largest body on the internet. To encourage staff or other adults into
this field, it might be prudent to reduce the amount of noise and
interfearance a bored student (or staff member!) can generate.
Realtime conferencing via computer networks is, however, a very
attractive toy to many students. It puts them in touch with the world
at no extra charge to them. They are able to construct their own
character and mask or hide their real self. This is a field which has
already been researched and is an interesting topic to pursue.
4.0 Setting it up
4.1 Installation
The installation and setup of most network utilities/servers is not
something that is commonly discussed. It is, however, a point worth
considering here after observations made on the setup and
installation of systems such as IRC. If the setup is too easy and
requires little work, it is not unreasonable to expect students to
"install" it in their own accounts to provide themselves and friends
with this service. There is little that can really be done about this
except to force servers to listen and connect only to a certain
priveledged port(s). This need, however, requires root intervention
or aid and it is doubtful whether a service such as this should
require such steps.
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This problem is not often encountered with other network services
since they either require large amounts of disk space to be done
properly (news) or require the co-operation of other servers before
they work in a full serving role (DNS and use of name servers is a
good example of this). Of the two, the latter is a good solution if
it can be implemented fairly and well.
4.2 Controlling growth
Is it possible to reasonably control the growth and connectivity of a
large realtime conferencing network? Should it be compared to other
facilities such as USENet which is commonly available and very
widespread with no real central control over who gets news?
5.0 Finding the *right* protocol
This section deals with points which are central issues when deciding
upon a protocol. There are many points to consider when developing a
realtime protocol which is going to provide a service to many users
simultaneously.
5.1 Name for protocol
Although names such as IRC and ICB have been used in the past to
describe the implementation provided, this document is aimed at
stimulating a protocol which is much more general and useful than
these. A better name would reflect this. Depending on what network it
is implemented on, the Network Conferencing Protocol (NCP) or the
Internet Conferencing Protocol (ICP) are two suitable names.
5.2 Responsibilities of conference servers
5.2.1 Message passing
A conferencing server should pass on all messages not destined for
itself or its users to the destination as quickly and efficiently as
possible. To this end, the server should not be required to do
extensive parsing of the incoming message, but rather, look at the
header and decide from there whether to send it on in the typical
gateway/relay fashion or parse it and pass it to one or more of its
users.
5.2.2 Who is on?
Any conference server should be able to supply (on request) a list of
attached user(s). The attached user(s) should have the option of
being able to say whether they wish to show up in such lists.
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5.2.3 Who is who?
All servers should provide *some* method to identify any known user
and supply details to the person making the query based on the search
key given.
5.2.4 Conference security
Conference servers should not run in such a manner that they
deliberately record the private conversation(s) of users which are
relying on the server in some way. It might seem that encrypting the
message before transmission to other servers in some way would solve
this, but this is better left as an option which is implemented in
clients and thus leaves it to the users to decide how secure they
want their conference to be.
5.2.5 Error reporting
All errors that the server encounters in its running life should one
way or another be reported to the operator(s) which are responsible
for this. This may include sending messages if an operator is online
or logging it to an error file.
5.2.6 Network Friendliness
It is quite easy for any network based application to "abuse" the
network it is running on. Also in a relay situation, it is quite
possible that a server will become bogged down trying to keep up with
just one connection and reduces the performance on an overall scale
to all users relying on it. It is therefore recommended that user
connections be subject to some sort of monitoring and flood control
to stop them dumping large amounts of spurious data and causing the
server to slow down.
The server should also aim to maximise the packet size of all packets
written out to the network. Not only does this make the packet/bytes
statistics look nice, but also increases the efficiency of the server
by reducing the time it spends in the system state waiting/doing IO
operations such as read/write. The cost here is a fractional decrease
in the real-time efficiency of the server.
5.2.7 To ASCII or not to ASCII
Given that most of the widely used Internet protocols such as SMTP,
NNTP and FTP are all based on commands which are given via ASCII
strings, there seems no reason why a conferencing protocol should be
any different. The gains from going to binary are marginal and
debugging/testing is not as easy as with ASCII. However, it is not
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unreasonable for some part of the protocol to be done in binary.
5.2.8 Queries or messages to a server and replies
For implementation of server queries, it is quite acceptable to use
ASCII messages which are made up of words. (Any string of characters
which doesn't start with a number). Replies should be some sort of
numeric. This is a follow on from from 5.2.7 where all of FTP, NNTP
and SMTP work in this manner. By reserving numerics *just* for server
replies, there can be no confusion about whether the message is going
to or from a server.
5.3 Responsibilities of clients
This section discusses the obligations of clients which are connected
to a conference server.
5.3.1 Providing accurate information
Expecting accurate information is foolish, it matters not for most of
the internet, but those that we do wish to trace wont give such
information. A client is expected to provide accurate and valid
information to the server it connects to so that confusion about who
is who is not a problem. Optionally, the server may decide to not
trust the information from the client and use some authentication
scheme that is open to it for such.
5.3.2 Client as servers
If a client is acting as a server and accepting direct connections
from other clients, the client should provide information about users
as discussed in 5.2.3. It is not necessary that a client be able to
handle complex methods of communication such as channels and their
advanced forms, but they should at least provide users with being
able to send messages to other users.
An example of this type of program might be Xtv where one or more
users can connect to another Xtv client program using Xtv clients.
In the case of X windows and perhaps in other areas, one it to ask
the destination user to run a program in a similar manner to unix
talk.
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5.4 How complex should the protocol be?
5.4.1 User identification
When a user signs onto a system that has an implementation of a
conferencing protocol, they are usually asked or given some sort of
unique key by which they are later able to be referenced by. In a
large system, it may be such that any key which has meaning to the
user(s) will not be sufficient and that collisions will occur with
such. It is therefore suggested that a server generate an identifier
for each new user it has. This identifier must not only be unique in
space, but also time. It is not reasonable for the user to ever have
to be aware of what this identifier is, it should only be known by
servers which *need* to know. A similar system to that used by
NNTP/SMTP is a fair implementation of such a scheme.
5.4.2 Trees and cycles
Due to the structure of the network being cyclic or forming loops, it
is quite natural to want to emulate this within the protocol that is
available for users. This has several advantages over trees, mainly
the average path between any 2 nodes being shorter. A cyclic
structure also poses many problems in getting messages delivered and
keeping the connected users and servers up to date. The main problem
with using the tree model is that a break in one part of the tree
needs to be communicated to all other parts of the tree to keep some
sort of realism about it. The problem here is that such
communications happen quite often and a lot of bandwidth is
needlessly generated. By implementing a protocol which supports a
cyclic graph of its connectivity, breakages are less damaging except
when it is a leaf or branch that breaks off.
5.5 Protocol summary
It is not expected that any protocol that meets the above demands
will be either easy to arrive at or easy to implement. Some of the
above requirements may seem to be exotic, unnecessary or not worth
the effort. After viewing previous conferencing programs and how they
work, many short comings can be seen in taking shortcuts.
6.0 Security Considerations
Security issues are not discussed in this memo.
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7.0 Author's Address
Darren Reed
4 Pateman Street
Watsonia, Victoria 3087
Australia
Email: avalon@coombs.anu.edu.au
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