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Network Working Group                                         D. ReedRequest for Comments: 1324                                   May 1992A Discussion on Computer Network ConferencingStatus 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 Contents1.0     Network Conferencing Today...........................21.1     Conferencing in general today........................21.2     Talk/phone vs. conferencing..........................31.3     Advantages of realtime network conferencing..........32.0     Goals for what a protocol should provide.............4Reed                                                            [Page 1]

RFC 1324             Computer Network Conferencing              May 19922.1     State Information problems...........................42.2     Network barriers.....................................42.3     User needs...........................................42.3.1   User privacy.........................................42.3.2   Realtime Expectations................................52.4     Message Delivery.....................................52.4.1   Deficiencies in using IP only........................52.4.2   Flexibility..........................................52.4.3   Building a flexible transport protocol...............52.5     Network Structure....................................52.5.1   Size.................................................53.0     Usage................................................64.0     Setting it up........................................64.1     Installation.........................................64.2     Controlling growth...................................75.0     Finding the *right* protocol.........................75.1     Name for protocol....................................75.2     Responsibilities of conference servers...............75.2.1   Message passing......................................75.2.2   Who is on?...........................................75.2.3   Who is who?..........................................85.2.4   Conference security..................................85.2.5   Error reporting......................................85.2.6   Network Friendliness.................................85.2.7   To ASCII or not to ASCII.............................85.2.8   Queries or messages to a server and replies..........95.3     Responsibilities of clients..........................95.3.1   Providing accurate information.......................95.3.2   Client as servers....................................95.4     How complex should the protocol be?.................105.4.1   User identification.................................105.4.2   Trees and cycles....................................105.5     Protocol summary....................................106.0     Security Considerations.............................107.0     Author's Address....................................111.0  NETWORK CONFERENCING TODAY1.1  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 andReed                                                            [Page 2]

RFC 1324             Computer Network Conferencing              May 1992   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 withRFC822. 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 andReed                                                            [Page 3]

RFC 1324             Computer Network Conferencing              May 1992   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 needs2.3.1  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.Reed                                                            [Page 4]

RFC 1324             Computer Network Conferencing              May 19922.3.2  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 Delivery2.4.1  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 Structure2.5.1  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 isReed                                                            [Page 5]

RFC 1324             Computer Network Conferencing              May 1992   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 up4.1  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.Reed                                                            [Page 6]

RFC 1324             Computer Network Conferencing              May 1992   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 servers5.2.1  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.Reed                                                            [Page 7]

RFC 1324             Computer Network Conferencing              May 19925.2.3  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 notReed                                                            [Page 8]

RFC 1324             Computer Network Conferencing              May 1992   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.Reed                                                            [Page 9]

RFC 1324             Computer Network Conferencing              May 19925.4  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.Reed                                                           [Page 10]

RFC 1324             Computer Network Conferencing              May 19927.0  Author's Address   Darren Reed   4 Pateman Street   Watsonia, Victoria 3087   Australia   Email: avalon@coombs.anu.edu.auReed                                                           [Page 11]