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Network Working Group                                            C. KaltRequest for Comments: 2811                                    April 2000Updates:1459Category: InformationalInternet Relay Chat: Channel ManagementStatus of this Memo   This memo provides information for the Internet community.  It does   not specify an Internet standard of any kind.  Distribution of this   memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2000).  All Rights Reserved.Abstract   One of the most notable characteristics of the IRC (Internet Relay   Chat) protocol is to allow for users to be grouped in forums, called   channels, providing a mean for multiple users to communicate   together.   There was originally a unique type of channels, but with the years,   new types appeared either as a response to a need, or for   experimental purposes.   This document specifies how channels, their characteristics and   properties are managed by IRC servers.Table of Contents1.  Introduction ...............................................22.  Channel Characteristics ....................................32.1  Namespace ..............................................32.2  Channel Scope ..........................................32.3  Channel Properties .....................................42.4  Privileged Channel Members .............................42.4.1  Channel Operators .................................52.4.2  Channel Creator ...................................53.  Channel lifetime ...........................................53.1  Standard channels ......................................53.2  Safe Channels ..........................................64.  Channel Modes ..............................................74.1  Member Status ..........................................74.1.1  "Channel Creator" Status ..........................7Kalt                         Informational                      [Page 1]

RFC 2811        Internet Relay Chat: Channel Management       April 20004.1.2  Channel Operator Status ...........................84.1.3  Voice Privilege ...................................84.2  Channel Flags ..........................................84.2.1  Anonymous Flag ....................................84.2.2  Invite Only Flag ..................................84.2.3  Moderated Channel Flag ............................9         4.2.4  No Messages To Channel From Clients On The Outside    94.2.5  Quiet Channel .....................................94.2.6  Private and Secret Channels .......................94.2.7  Server Reop Flag ..................................104.2.8  Topic .............................................104.2.9  User Limit ........................................104.2.10  Channel Key ......................................104.3  Channel Access Control .................................104.3.1  Channel Ban and Exception .........................114.3.2  Channel Invitation ................................115.  Current Implementations ....................................115.1  Tracking Recently Used Channels ........................115.2  Safe Channels ..........................................125.2.1  Channel Identifier ................................125.2.2  Channel Delay .....................................125.2.3  Abuse Window ......................................135.2.4  Preserving Sanity In The Name Space ...............135.2.5  Server Reop Mechanism .............................136.  Current problems ...........................................146.1  Labels .................................................146.1.1  Channel Delay .....................................146.1.2  Safe Channels .....................................156.2  Mode Propagation Delays ................................156.3  Collisions And Channel Modes ...........................156.4  Resource Exhaustion ....................................167.  Security Considerations ....................................167.1  Access Control .........................................167.2  Channel Privacy ........................................167.3 Anonymity ...............................................178.  Current support and availability ...........................179.  Acknowledgements ...........................................1710. References ................................................1811. Author's Address ..........................................1812. Full Copyright Statement ...................................191. Introduction   This document defines in detail on how channels are managed by the   IRC servers and will be mostly useful to people working on   implementing an IRC server.Kalt                         Informational                      [Page 2]

RFC 2811        Internet Relay Chat: Channel Management       April 2000   While the concepts defined here are an important part of IRC, they   remain non essential for implementing clients.  While the trend seems   to be towards more and more complex and "intelligent" clients which   are able to take advantage of knowing the internal workings of   channels to provide the users with a more friendly interface, simple   clients can be implemented without reading this document.   Many of the concepts defined here were designed with the IRC   architecture [IRC-ARCH] in mind and mostly make sense in this   context.  However, many others could be applied to other   architectures in order to provide forums for a conferencing system.   Finally, it is to be noted that IRC users may find some of the   following sections of interest, in particular sections2 (Channel   Characteristics) and 4 (Channel Modes).2. Channel Characteristics   A channel is a named group of one or more users which will all   receive messages addressed to that channel.  A channel is   characterized by its name, properties and current members.2.1 Namespace   Channels names are strings (beginning with a '&', '#', '+' or '!'   character) of length up to fifty (50) characters.  Channel names are   case insensitive.   Apart from the the requirement that the first character being either   '&', '#', '+' or '!' (hereafter called "channel prefix"). The only   restriction on a channel name is that it SHALL NOT contain any spaces   (' '), a control G (^G or ASCII 7), a comma (',' which is used as a   list item separator by the protocol).  Also, a colon (':') is used as   a delimiter for the channel mask.  The exact syntax of a channel name   is defined in "IRC Server Protocol" [IRC-SERVER].   The use of different prefixes effectively creates four (4) distinct   namespaces for channel names.  This is important because of the   protocol limitations regarding namespaces (in general).  Seesection6.1 (Labels) for more details on these limitations.2.2 Channel Scope   A channel entity is known by one or more servers on the IRC network.   A user can only become member of a channel known by the server to   which the user is directly connected.  The list of servers which knowKalt                         Informational                      [Page 3]

RFC 2811        Internet Relay Chat: Channel Management       April 2000   of the existence of a particular channel MUST be a contiguous part of   the IRC network, in order for the messages addressed to the channel   to be sent to all the channel members.   Channels with '&' as prefix are local to the server where they are   created.   Other channels are known to one (1) or more servers that are   connected to the network, depending on the channel mask:      If there is no channel mask, then the channel is known to all      the servers.      If there is a channel mask, then the channel MUST only be known      to servers which has a local user on the channel, and to its      neighbours if the mask matches both the local and neighbouring      server names.  Since other servers have absolutely no knowledge of      the existence of such a channel, the area formed by the servers      having a name matching the mask has to be contiguous for the      channel to be known by all these servers.  Channel masks are best      used in conjunction with server hostmasking [IRC-SERVER].2.3 Channel Properties   Each channel has its own properties, which are defined by channel   modes.  Channel modes can be manipulated by the channel members.  The   modes affect the way servers manage the channels.   Channels with '+' as prefix do not support channel modes.  This means   that all the modes are unset, with the exception of the 't' channel   flag which is set.2.4 Privileged Channel Members   In order for the channel members to keep some control over a channel,   and some kind of sanity, some channel members are privileged.  Only   these members are allowed to perform the following actions on the   channel:        INVITE  - Invite a client to an invite-only channel (mode +i)        KICK    - Eject a client from the channel        MODE    - Change the channel's mode, as well as                  members' privileges        PRIVMSG - Sending messages to the channel (mode +n, +m, +v)        TOPIC   - Change the channel topic in a mode +t channelKalt                         Informational                      [Page 4]

RFC 2811        Internet Relay Chat: Channel Management       April 20002.4.1 Channel Operators   The channel operators (also referred to as a "chop" or "chanop") on a   given channel are considered to 'own' that channel.  Ownership of a   channel is shared among channel operators.   Channel operators are identified by the '@' symbol next to their   nickname whenever it is associated with a channel (i.e., replies to   the NAMES, WHO and WHOIS commands).   Since channels starting with the character '+' as prefix do not   support channel modes, no member can therefore have the status of   channel operator.2.4.2 Channel Creator   A user who creates a channel with the character '!' as prefix is   identified as the "channel creator".  Upon creation of the channel,   this user is also given channel operator status.   In recognition of this status, the channel creators are endowed with   the ability to toggle certain modes of the channel which channel   operators may not manipulate.   A "channel creator" can be distinguished from a channel operator by   issuing the proper MODE command.  See the "IRC Client Protocol"   [IRC-CLIENT] for more information on this topic.3. Channel lifetime   In regard to the lifetime of a channel, there are typically two   groups of channels: standard channels which prefix is either '&', '#'   or '+', and "safe channels" which prefix is '!'.3.1 Standard channels   These channels are created implicitly when the first user joins it,   and cease to exist when the last user leaves it.  While the channel   exists, any client can reference the channel using the name of the   channel.   The user creating a channel automatically becomes channel operator   with the notable exception of channels which name is prefixed by the   character '+', seesection 4 (Channel modes).  Seesection 2.4.1   (Channel Operators) for more details on this title.Kalt                         Informational                      [Page 5]

RFC 2811        Internet Relay Chat: Channel Management       April 2000   In order to avoid the creation of duplicate channels (typically when   the IRC network becomes disjoint because of a split between two   servers), channel names SHOULD NOT be allowed to be reused by a user   if a channel operator (SeeSection 2.4.1 (Channel Operators)) has   recently left the channel because of a network split.  If this   happens, the channel name is temporarily unavailable.  The duration   while a channel remains unavailable should be tuned on a per IRC   network basis.  It is important to note that this prevents local   users from creating a channel using the same name, but does not   prevent the channel to be recreated by a remote user. The latter   typically happens when the IRC network rejoins.  Obviously, this   mechanism only makes sense for channels which name begins with the   character '#', but MAY be used for channels which name begins with   the character '+'.  This mechanism is commonly known as "Channel   Delay".3.2 Safe Channels   Unlike other channels, "safe channels" are not implicitly created.  A   user wishing to create such a channel MUST request the creation by   sending a special JOIN command to the server in which the channel   identifier (then unknown) is replaced by the character '!'.  The   creation process for this type of channel is strictly controlled.   The user only chooses part of the channel name (known as the channel   "short name"), the server automatically prepends the user provided   name with a channel identifier consisting of five (5) characters.   The channel name resulting from the combination of these two elements   is unique, making the channel safe from abuses based on network   splits.   The user who creates such a channel automatically becomes "channel   creator".  Seesection 2.4.2 (Channel Creator) for more details on   this title.   A server MUST NOT allow the creation of a new channel if another   channel with the same short name exists; or if another channel with   the same short name existed recently AND any of its member(s) left   because of a network split.  Such channel ceases to exist after last   user leaves AND no other member recently left the channel because of   a network split.   Unlike the mechanism described insection 5.2.2 (Channel Delay), in   this case, channel names do not become unavailable: these channels   may continue to exist after the last user left.  Only the user   creating the channel becomes "channel creator", users joining an   existing empty channel do not automatically become "channel creator"   nor "channel operator".Kalt                         Informational                      [Page 6]

RFC 2811        Internet Relay Chat: Channel Management       April 2000   To ensure the uniqueness of the channel names, the channel identifier   created by the server MUST follow specific rules.  For more details   on this, seesection 5.2.1 (Channel Identifier).4. Channel Modes   The various modes available for channels are as follows:        O - give "channel creator" status;        o - give/take channel operator privilege;        v - give/take the voice privilege;        a - toggle the anonymous channel flag;        i - toggle the invite-only channel flag;        m - toggle the moderated channel;        n - toggle the no messages to channel from clients on the            outside;        q - toggle the quiet channel flag;        p - toggle the private channel flag;        s - toggle the secret channel flag;        r - toggle the server reop channel flag;        t - toggle the topic settable by channel operator only flag;        k - set/remove the channel key (password);        l - set/remove the user limit to channel;        b - set/remove ban mask to keep users out;        e - set/remove an exception mask to override a ban mask;        I - set/remove an invitation mask to automatically override            the invite-only flag;   Unless mentioned otherwise below, all these modes can be manipulated   by "channel operators" by using the MODE command defined in "IRC   Client Protocol" [IRC-CLIENT].4.1 Member Status   The modes in this category take a channel member nickname as argument   and affect the privileges given to this user.4.1.1 "Channel Creator" Status   The mode 'O' is only used in conjunction with "safe channels" and   SHALL NOT be manipulated by users.  Servers use it to give the user   creating the channel the status of "channel creator".Kalt                         Informational                      [Page 7]

RFC 2811        Internet Relay Chat: Channel Management       April 20004.1.2 Channel Operator Status   The mode 'o' is used to toggle the operator status of a channel   member.4.1.3 Voice Privilege   The mode 'v' is used to give and take voice privilege to/from a   channel member.  Users with this privilege can talk on moderated   channels.  (Seesection 4.2.3 (Moderated Channel Flag).4.2 Channel Flags   The modes in this category are used to define properties which   affects how channels operate.4.2.1 Anonymous Flag   The channel flag 'a' defines an anonymous channel.  This means that   when a message sent to the channel is sent by the server to users,   and the origin is a user, then it MUST be masked.  To mask the   message, the origin is changed to "anonymous!anonymous@anonymous."   (e.g., a user with the nickname "anonymous", the username "anonymous"   and from a host called "anonymous.").  Because of this, servers MUST   forbid users from using the nickname "anonymous".  Servers MUST also   NOT send QUIT messages for users leaving such channels to the other   channel members but generate a PART message instead.   On channels with the character '&' as prefix, this flag MAY be   toggled by channel operators, but on channels with the character '!'   as prefix, this flag can be set (but SHALL NOT be unset) by the   "channel creator" only.  This flag MUST NOT be made available on   other types of channels.   Replies to the WHOIS, WHO and NAMES commands MUST NOT reveal the   presence of other users on channels for which the anonymous flag is   set.4.2.2 Invite Only Flag   When the channel flag 'i' is set, new members are only accepted if   their mask matches Invite-list (Seesection 4.3.2) or they have been   invited by a channel operator.  This flag also restricts the usage of   the INVITE command (See "IRC Client Protocol" [IRC-CLIENT]) to   channel operators.Kalt                         Informational                      [Page 8]

RFC 2811        Internet Relay Chat: Channel Management       April 20004.2.3 Moderated Channel Flag   The channel flag 'm' is used to control who may speak on a channel.   When it is set, only channel operators, and members who have been   given the voice privilege may send messages to the channel.      This flag only affects users.4.2.4 No Messages To Channel From Clients On The Outside   When the channel flag 'n' is set, only channel members MAY send   messages to the channel.      This flag only affects users.4.2.5 Quiet Channel   The channel flag 'q' is for use by servers only.  When set, it   restricts the type of data sent to users about the channel   operations: other user joins, parts and nick changes are not sent.   From a user's point of view, the channel contains only one user.   This is typically used to create special local channels on which the   server sends notices related to its operations.  This was used as a   more efficient and flexible way to replace the user mode 's' defined   inRFC 1459 [IRC].4.2.6 Private and Secret Channels   The channel flag 'p' is used to mark a channel "private" and the   channel flag 's' to mark a channel "secret".  Both properties are   similar and conceal the existence of the channel from other users.   This means that there is no way of getting this channel's name from   the server without being a member.  In other words, these channels   MUST be omitted from replies to queries like the WHOIS command.   When a channel is "secret", in addition to the restriction above, the   server will act as if the channel does not exist for queries like the   TOPIC, LIST, NAMES commands.  Note that there is one exception to   this rule: servers will correctly reply to the MODE command.   Finally, secret channels are not accounted for in the reply to the   LUSERS command (See "Internet Relay Chat: Client Protocol" [IRC-   CLIENT]) when the <mask> parameter is specified.Kalt                         Informational                      [Page 9]

RFC 2811        Internet Relay Chat: Channel Management       April 2000   The channel flags 'p' and 's' MUST NOT both be set at the same time.   If a MODE message originating from a server sets the flag 'p' and the   flag 's' is already set for the channel, the change is silently   ignored.  This should only happen during a split healing phase   (mentioned in the "IRC Server Protocol" document [IRC-SERVER]).4.2.7 Server Reop Flag   The channel flag 'r' is only available on channels which name begins   with the character '!' and MAY only be toggled by the "channel   creator".   This flag is used to prevent a channel from having no channel   operator for an extended period of time.  When this flag is set, any   channel that has lost all its channel operators for longer than the   "reop delay" period triggers a mechanism in servers to reop some or   all of the channel inhabitants.  This mechanism is described more in   detail insection 5.2.4 (Channel Reop Mechanism).4.2.8 Topic   The channel flag 't' is used to restrict the usage of the TOPIC   command to channel operators.4.2.9 User Limit   A user limit may be set on channels by using the channel flag 'l'.   When the limit is reached, servers MUST forbid their local users to   join the channel.   The value of the limit MUST only be made available to the channel   members in the reply sent by the server to a MODE query.4.2.10 Channel Key   When a channel key is set (by using the mode 'k'), servers MUST   reject their local users request to join the channel unless this key   is given.   The channel key MUST only be made visible to the channel members in   the reply sent by the server to a MODE query.4.3 Channel Access Control   The last category of modes is used to control access to the channel,   they take a mask as argument.Kalt                         Informational                     [Page 10]

RFC 2811        Internet Relay Chat: Channel Management       April 2000   In order to reduce the size of the global database for control access   modes set for channels, servers MAY put a maximum limit on the number   of such modes set for a particular channel.  If such restriction is   imposed, it MUST only affect user requests.  The limit SHOULD be   homogeneous on a per IRC network basis.4.3.1 Channel Ban and Exception   When a user requests to join a channel, his local server checks if   the user's address matches any of the ban masks set for the channel.   If a match is found, the user request is denied unless the address   also matches an exception mask set for the channel.   Servers MUST NOT allow a channel member who is banned from the   channel to speak on the channel, unless this member is a channel   operator or has voice privilege. (SeeSection 4.1.3 (Voice   Privilege)).   A user who is banned from a channel and who carries an invitation   sent by a channel operator is allowed to join the channel.4.3.2 Channel Invitation   For channels which have the invite-only flag set (SeeSection 4.2.2   (Invite Only Flag)), users whose address matches an invitation mask   set for the channel are allowed to join the channel without any   invitation.5. Current Implementations   The only current implementation of these rules as part of the IRC   protocol is the IRC server, version 2.10.   The rest of this section deals with issues that are mostly of   importance to those who wish to implement a server but some parts may   also be of interest for client writers.5.1 Tracking Recently Used Channels   This mechanism is commonly known as "Channel Delay" and generally   only applies to channels which names is prefixed with the character   '#' (SeeSection 3.1 "Standard channels").   When a network split occurs, servers SHOULD keep track of which   channels lost a "channel operator" as the result of the break.  These   channels are then in a special state which lasts for a certain period   of time.  In this particular state, the channels cannot cease toKalt                         Informational                     [Page 11]

RFC 2811        Internet Relay Chat: Channel Management       April 2000   exist.  If all the channel members leave the channel, the channel   becomes unavailable: the server local clients cannot join the channel   as long as it is empty.   Once a channel is unavailable, it will become available again either   because a remote user has joined the channel (most likely because the   network is healing), or because the delay period has expired (in   which case the channel ceases to exist and may be re-created).   The duration for which a channel death is delayed SHOULD be set   considering many factors among which are the size (user wise) of the   IRC network, and the usual duration of network splits.  It SHOULD be   uniform on all servers for a given IRC network.5.2 Safe Channels   This document introduces the notion of "safe channels".  These   channels have a name prefixed with the character '!' and great effort   is made to avoid collisions in this name space.  Collisions are not   impossible, however they are very unlikely.5.2.1 Channel Identifier   The channel identifier is a function of the time.  The current time   (as defined under UNIX by the number of seconds elapsed since   00:00:00 GMT, January 1, 1970) is converted in a string of five (5)   characters using the following base:   "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890" (each character has a decimal   value starting from 0 for 'A' to 35 for '0').   The channel identifier therefore has a periodicity of 36^5 seconds   (about 700 days).5.2.2 Channel Delay   These channels MUST be subject to the "channel delay" mechanism   described insection 5.1 (Channel Delay).  However, the mechanism is   slightly adapted to fit better.   Servers MUST keep track of all such channels which lose members as   the result of a network split, no matter whether the user is a   "channel operator" or not.   However, these channels do NOT ever become unavailable, it is always   possible to join them even when they are empty.Kalt                         Informational                     [Page 12]

RFC 2811        Internet Relay Chat: Channel Management       April 20005.2.3 Abuse Window   Because the periodicity is so long, attacks on a particular channel   (name) may only occur once in a very long while.  However, with luck   and patience, it is still possible for a user to cause a channel   collision.  In order to avoid this, servers MUST "look in the future"   and keep a list of channel names which identifier is about to be used   (in the coming few days for example). Such list should remain small,   not be a burden for servers to maintain and be used to avoid channel   collisions by preventing the re-creation of such channel for a longer   period of time than channel delay does.   Eventually a server MAY choose to extend this procedure to forbid   creation of channels with the same shortname only (then ignoring the   channel identifier).5.2.4 Preserving Sanity In The Name Space   The combination of the mechanisms described in sections5.2.2 and   5.2.3 makes it quite difficult for a user to create a channel   collision. However, another type of abuse consists of creating many   channels having the same shortname, but different identifiers.  To   prevent this from happening, servers MUST forbid the creation of a   new channel which has the same shortname of a channel currently   existing.5.2.5 Server Reop Mechanism   When a channel has been opless for longer than the "reop delay"   period and has the channel flag 'r' set (SeeSection 4.2.7 (Server   Reop Flag)), IRC servers are responsible for giving the channel   operator status randomly to some of the members.   The exact logic used for this mechanism by the current implementation   is described below.  Servers MAY use a different logic, but that it   is strongly RECOMMENDED that all servers use the same logic on a   particular IRC network to maintain coherence as well as fairness.   For the same reason, the "reop delay" SHOULD be uniform on all   servers for a given IRC network.  As for the "channel delay", the   value of the "reop delay" SHOULD be set considering many factors   among which are the size (user wise) of the IRC network, and the   usual duration of network splits.   a) the reop mechanism is triggered after a random time following the      expiration of the "reop delay".  This should limit the eventuality      of the mechanism being triggered at the same time (for the same      channel) on two separate servers.Kalt                         Informational                     [Page 13]

RFC 2811        Internet Relay Chat: Channel Management       April 2000   b) If the channel is small (five (5) users or less), and the "channel      delay" for this channel has expired,        Then reop all channel members if at least one member is local to        the server.   c) If the channel is small (five (5) users or less), and the "channel      delay" for this channel has expired, and the "reop delay" has      expired for longer than its value,        Then reop all channel members.   d) For other cases, reop at most one member on the channel, based on      some method build into the server. If you don't reop a member, the      method should be such that another server will probably op      someone. The method SHOULD be the same over the whole network. A      good heuristic could be just random reop.      (The current implementation actually tries to choose a member      local to the server who has not been idle for too long, eventually      postponing action, therefore letting other servers have a chance      to find a "not too idle" member.  This is over complicated due to      the fact that servers only know the "idle" time of their local      users)6. Current problems   There are a number of recognized problems with the way IRC channels   are managed.  Some of these can be directly attributed to the rules   defined in this document, while others are the result of the   underlying "IRC Server Protocol" [IRC-SERVER].  Although derived fromRFC 1459 [IRC], this document introduces several novelties in an   attempt to solve some of the known problems.6.1 Labels   This document defines one of the many labels used by the IRC   protocol.  Although there are several distinct namespaces (based on   the channel name prefix), duplicates inside each of these are not   allowed.  Currently, it is possible for users on different servers to   pick the label which may result in collisions (with the exception of   channels known to only one server where they can be averted).6.1.1 Channel Delay   The channel delay mechanism described insection 5.1 (Tracking   Recently Used Channels) and used for channels prefixed with the   character '#' is a simple attempt at preventing collisions from   happening.  Experience has shown that, under normal circumstances, itKalt                         Informational                     [Page 14]

RFC 2811        Internet Relay Chat: Channel Management       April 2000   is very efficient; however, it obviously has severe limitations   keeping it from being an adequate solution to the problem discussed   here.6.1.2 Safe Channels   "Safe channels" described insection 3.2 (Safe Channels) are a better   way to prevent collisions from happening as it prevents users from   having total control over the label they choose.  The obvious   drawback for such labels is that they are not user friendly.   However, it is fairly trivial for a client program to improve on   this.6.2 Mode Propagation Delays   Because of network delays induced by the network, and because each   server on the path is REQUIRED to check the validity of mode changes   (e.g., user exists and has the right privileges), it is not unusual   for a MODE message to only affect part of the network, often creating   a discrepancy between servers on the current state of a channel.   While this may seem easy to fix (by having only the original server   check the validity of mode changes), it was decided not to do so for   various reasons.  One concern is that servers cannot trust each   other, and that a misbehaving servers can easily be detected.  This   way of doing so also stops wave effects on channels which are out of   synch when mode changes are issued from different directions.6.3 Collisions And Channel Modes   The "Internet Relay Chat: Server Protocol" document [IRC-SERVER]   describes how channel data is exchanged when two servers connect to   each other.  Channel collisions (either legitimate or not) are   treated as inclusive events, meaning that the resulting channel has   for members all the users who are members of the channel on either   server prior to the connection.   Similarly, each server sends the channel modes to the other one.   Therefore, each server also receives these channel modes.  There are   three types of modes for a given channel: flags, masks, and data.   The first two types are easy to deal with as they are either set or   unset.  If such a mode is set on one server, it MUST be set on the   other server as a result of the connection.Kalt                         Informational                     [Page 15]

RFC 2811        Internet Relay Chat: Channel Management       April 2000   As topics are not sent as part of this exchange, they are not a   problem.  However, channel modes 'l' and 'k' are exchanged, and if   they are set on both servers prior to the connection, there is no   mechanism to decide which of the two values takes precedence.  It is   left up to the users to fix the resulting discrepancy.6.4 Resource Exhaustion   The mode based on masks defined insection 4.3 make the IRC servers   (and network) vulnerable to a simple abuse of the system: a single   channel operator can set as many different masks as possible on a   particular channel.  This can easily cause the server to waste   memory, as well as network bandwidth (since the info is propagated to   other servers).  For this reason it is RECOMMENDED that a limit be   put on the number of such masks per channels as mentioned insection4.3.   Moreover, more complex mechanisms MAY be used to avoid having   redundant masks set for the same channel.7. Security Considerations7.1 Access Control   One of the main ways to control access to a channel is to use masks   which are based on the username and hostname of the user connections.   This mechanism can only be efficient and safe if the IRC servers have   an accurate way of authenticating user connections, and if users   cannot easily get around it.  While it is in theory possible to   implement such a strict authentication mechanism, most IRC networks   (especially public networks) do not have anything like this in place   and provide little guaranty about the accuracy of the username and   hostname for a particular client connection.   Another way to control access is to use a channel key, but since this   key is sent in plaintext, it is vulnerable to traditional man in the   middle attacks.7.2 Channel Privacy   Because channel collisions are treated as inclusive events (SeeSection 6.3), it is possible for users to join a channel overriding   its access control settings.  This method has long been used by   individuals to "take over" channels by "illegitimately" gaining   channel operator status on the channel.  The same method can be used   to find out the exact list of members of a channel, as well as to   eventually receive some of the messages sent to the channel.Kalt                         Informational                     [Page 16]

RFC 2811        Internet Relay Chat: Channel Management       April 20007.3 Anonymity   The anonymous channel flag (SeeSection 4.2.1) can be used to render   all users on such channel "anonymous" by presenting all messages to   the channel as originating from a pseudo user which nickname is   "anonymous".  This is done at the client-server level, and no   anonymity is provided at the server-server level.   It should be obvious to readers, that the level of anonymity offered   is quite poor and insecure, and that clients SHOULD display strong   warnings for users joining such channels.8. Current support and availability     Mailing lists for IRC related discussion:       General discussion: ircd-users@irc.org       Protocol development: ircd-dev@irc.org     Software implementations:ftp://ftp.irc.org/irc/serverftp://ftp.funet.fi/pub/unix/ircftp://coombs.anu.edu.au/pub/irc     Newsgroup: alt.irc9. Acknowledgements   Parts of this document were copied from theRFC 1459 [IRC] which   first formally documented the IRC Protocol.  It has also benefited   from many rounds of review and comments.  In particular, the   following people have made significant contributions to this   document:   Matthew Green, Michael Neumayer, Volker Paulsen, Kurt Roeckx, Vesa   Ruokonen, Magnus Tjernstrom, Stefan Zehl.Kalt                         Informational                     [Page 17]

RFC 2811        Internet Relay Chat: Channel Management       April 200010. References   [KEYWORDS]   Bradner, S., "Key words for use in RFCs to Indicate                Requirement Levels",BCP 14,RFC 2119, March 1997.   [IRC]        Oikarinen, J. and D. Reed, "Internet Relay Chat                Protocol",RFC 1459, May 1993.   [IRC-ARCH]   Kalt, C., "Internet Relay Chat: Architecture",RFC 2810,                April 2000.   [IRC-CLIENT] Kalt, C., "Internet Relay Chat: Client Protocol",RFC2812, April 2000.   [IRC-SERVER] Kalt, C., "Internet Relay Chat: Server Protocol",RFC2813, April 2000.11. Author's Address   Christophe Kalt   99 Teaneck Rd, Apt #117   Ridgefield Park, NJ 07660   USA   EMail: kalt@stealth.netKalt                         Informational                     [Page 18]

RFC 2811        Internet Relay Chat: Channel Management       April 200012.  Full Copyright Statement   Copyright (C) The Internet Society (2000).  All Rights Reserved.   This document and translations of it may be copied and furnished to   others, and derivative works that comment on or otherwise explain it   or assist in its implementation may be prepared, copied, published   and distributed, in whole or in part, without restriction of any   kind, provided that the above copyright notice and this paragraph are   included on all such copies and derivative works.  However, this   document itself may not be modified in any way, such as by removing   the copyright notice or references to the Internet Society or other   Internet organizations, except as needed for the purpose of   developing Internet standards in which case the procedures for   copyrights defined in the Internet Standards process must be   followed, or as required to translate it into languages other than   English.   The limited permissions granted above are perpetual and will not be   revoked by the Internet Society or its successors or assigns.   This document and the information contained herein is provided on an   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Acknowledgement   Funding for the RFC Editor function is currently provided by the   Internet Society.Kalt                         Informational                     [Page 19]
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RFC 2811
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DocumentDocument typeRFC - Informational
April 2000
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