RPL_ISUPPORT Numeric Definition

Network Working Group E. Brocklesby

Internet-Draft January 5, 2004

Expires: July 5, 2004



IRC RPL_ISUPPORT Numeric Definition

draft-brocklesby-irc-isupport-03


Status of this Memo


This document is an Internet-Draft and is in full conformance with

all provisions of Section 10 of RFC2026.


Internet-Drafts are working documents of the Internet Engineering

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This Internet-Draft will expire on July 5, 2004.


Copyright Notice


Copyright (C) The Internet Society (2004). All Rights Reserved.


Abstract


This memo presents a way for the server to unobtrusively advertise

the ways in which it differs from the Internet Relay Chat (IRC)

specification defined in RFC1459. It is a primary goal to implement

this in a way which is completely backwards-compatible with the

original protocol, and as much as possible with current non-standard

implementations of the ISUPPORT numeric.











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Table of Contents


1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3

1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3

1.2 Changes to previous version . . . . . . . . . . . . . . . . 3

1.3 Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3

1.4 Notes on examples . . . . . . . . . . . . . . . . . . . . . 4

2. Protocol outline . . . . . . . . . . . . . . . . . . . . . . 4

3. Currently defined parameters . . . . . . . . . . . . . . . . 7

3.1 CASEMAPPING . . . . . . . . . . . . . . . . . . . . . . . . 7

3.2 CHANLIMIT . . . . . . . . . . . . . . . . . . . . . . . . . 7

3.3 CHANMODES . . . . . . . . . . . . . . . . . . . . . . . . . 8

3.4 CHANNELLEN . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.5 CHANTYPES . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.6 EXCEPTS . . . . . . . . . . . . . . . . . . . . . . . . . . 9

3.7 IDCHAN . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.8 INVEX . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.9 KICKLEN . . . . . . . . . . . . . . . . . . . . . . . . . . 10

3.10 MAXLIST . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.11 MODES . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

3.12 NETWORK . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.13 NICKLEN . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3.14 PREFIX . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.15 SAFELIST . . . . . . . . . . . . . . . . . . . . . . . . . . 13

3.16 STATUSMSG . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.17 STD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3.18 TARGMAX . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.19 TOPICLEN . . . . . . . . . . . . . . . . . . . . . . . . . . 15

4. Differences to existing implementations . . . . . . . . . . 16

4.1 PREFIX parameter without value . . . . . . . . . . . . . . . 16

4.2 EXCEPTS and INVEX value argument . . . . . . . . . . . . . . 16

4.3 STATUSMSG / WALLCHOPS . . . . . . . . . . . . . . . . . . . 16

4.4 Conflicts with RFC 2812 . . . . . . . . . . . . . . . . . . 16

4.5 Default value for CASEMAPPING . . . . . . . . . . . . . . . 17

4.6 CHANLIMIT / MAXCHANNELS . . . . . . . . . . . . . . . . . . 17

4.7 MAXLIST / MAXBANS . . . . . . . . . . . . . . . . . . . . . 17

4.8 CHARSET . . . . . . . . . . . . . . . . . . . . . . . . . . 17

4.9 TARGMAX / MAXTARGETS . . . . . . . . . . . . . . . . . . . . 17

5. Security Considerations . . . . . . . . . . . . . . . . . . 18

Normative References . . . . . . . . . . . . . . . . . . . . 18

Informative references . . . . . . . . . . . . . . . . . . . 18

Author's Address . . . . . . . . . . . . . . . . . . . . . . 18

A. Default ISUPPORT values . . . . . . . . . . . . . . . . . . 18

B. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19

Intellectual Property and Copyright Statements . . . . . . . 20







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1. Introduction


1.1 Terminology


o Original IRC protocol: The original IRC protocol as described in

RFC 1459 [5].

o The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL

NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and

"OPTIONAL" in this document are to be interpreted as described in

RFC 2119 [1].

o The ABNF syntax used in this document is defined in RFC 2234 [2]

o The term "character" is this document is used to mean an octet, as

defined in RFC 1459 [5], section 2.2.


1.2 Changes to previous version


[Note: To be removed by the RFC editor prior to publication.]


The follow significant changes were made from version 02 to version

03 of this document:


o The semantics of MAXCHANNELS were changed and it was renamed to

CHANLIMIT.

o The semantics of CHIDLEN were changed and it was renamed to

IDCHAN.

o The description of the protocol was clarified significantly, as

were several parameter definitions. Several recommendations of

what the client should do when faced with protocol violations by

the server were also removed.

o Several implications or recommendations of client or server

behaviour were changed into requirements or removed entirely.

o In particular, the server is now required to send STD as the first

parameter upon client registration, followed by all defined

parameters which have no default value.

o The specification of a parameter's value was changed to allow

"\xHH" sequences, to represent spaces and other characters. This

feature is considered experimental and comments are particular

appreciated.

o Delivery of 005 numerics from remote servers is now explicitly

prohibited.

o The CHARSET parameter was found to be unworkable and has been

entirely removed.

o The TARGMAX parameter was added.

o "X" and "X=" were made identical.


1.3 Motivation


Since the publication of RFC 1459 [5] in 1993, a number of changes




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and extensions have been made to the IRC protocol. This has led to a

problem whereby clients are unable to correctly interpret some server

replies, because the reply, channel mode, and so on may have

different meanings on different implementations of the IRC server.

It is also difficult for the client to ascertain which protocol

extensions may be available on a specific server.


A de facto standard has emerged in the community, originally

implemented by the Undernet's IRC server software based on the 005

numeric from DALnet's IRC server, which allows the server to

advertise to the client upon connection which protocol extensions it

supports. This reply, termed RPL_ISUPPORT, uses the non-standard

numeric 005.


Unfortunately, since there is no standard document describing the

ISUPPORT numeric, differences have emerged between implementations in

IRC server software; it is believed that this reduces the potential

usefulness of the feature. This memo attempts to standardise the

format and content of the ISUPPORT numeric in an extensible way, such

that IRC clients can use the information provided to the maximum

extent.


1.4 Notes on examples


Several examples of protocol replies are given throughout this

document. These are intended only for clarification of the protocol;

in the case of a discrepancy between the example and the formal

specification, the specification is always preferred.


2. Protocol outline


The ISUPPORT numeric consists of a series of parameters, each of

which maps to a protocol extension supported by the IRC server. A

parameter may have an associated value, typically a numeric or string

value, which provides additional information on the extension.


The format of the ISUPPORT numeric is the same as other server

numeric replies currently used. A client which does not understand

the numeric may ignore it; however, it is recommended that IRC

clients understand ISUPPORT, in order to allow users the full benefit

of features implemented by the IRC server.











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The ABNF grammar for the numeric is as follows:


isupport = ":" servername SP "005" SP nickname SP

1*13( token SP ) ":are supported by this server"


token = *1"-" parameter / parameter *1( "=" value )

parameter = 1*20letter

value = *letpun

letter = ALPHA / DIGIT

punct = %d33-47 / %d58-64 / %d91-96 / %d123-126

letpun = letter / punct


The format of the postfix descriptive text is not fixed, and may be

any string subject to the requirements of RFC 1459 [5] regarding

numeric replies. Servername and nickname are as defined in RFC 1459

[5].


The "servername" MUST be the name of the server to which the client

is connected; the 005 numeric is never sent remotely across the

network. As with other local numerics, when delivered remotely it

MUST be converted into a 105 numeric before delivery to the client.


A token is of the form "PARAMETER[=VALUE]" or "-PARAMETER". The forms

"X" and "X=" are identical; they both define that the parameter is

present but has no value. The server SHOULD send "X", not "X="; this

is the normalised form.


The server MUST send the parameter in upper-case text; unless

otherwise stated, the parameter's value is case sensitive.


The parameter's value may contain sequences of the form "\xHH", where

HH is a two-digit hexadecimal number. Each such sequence is

considered identical to the equivalent octet after parsing of the

reply into separate tokens has occurred.


[Example: X=A\x20B defines one token, "X", with the value "A B",

rather than two tokens "X" and "B".]

[Note: The literal string "\x" must therefore be encoded as

"\x5Cx".]


If the server has not advertised a CHARSET parameter, it MUST not use

such sequences with a value outside those permitted by the above ABNF

grammar, with the exception of "\x20"; if it has advertised CHARSET,

then it may in addition send any printable character defined in that

encoding. Characters in multibyte encodings such as UTF-8 should be

sent as a series of \x sequences.


RFC 1459 [5] defines a maximum of 15 parameters to any reply,




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including the nickname and the text; therefore, only 13 capabilities

are possible per reply.


In order to allow flexibility in the protocol, and future expansion,

the server may send more than one ISUPPORT reply per connection. It

is RECOMMENDED that consecutive ISUPPORT replies are sent adjacent to

each other. The client MUST support receiving multiple ISUPPORT

replies, and merge them to produce the final list of supported

protocol extensions. It is RECOMMENDED that the server attempt to

send 13 tokens per line before sending multiple replies.


On connection to the server, all parameters are assumed to be equal

to their default values, if any. Unless later changed by the server,

this default value persists throughout the connection. Except as

explicitly stated in its definition, a parameter SHOULD NOT be sent

unless it changes this default value. The server MUST send an 005

reply after client registration but before any further client

commands are processed in order to resolve any ambiguities in

parameters with no default value.


The form "-PARAMETER" is used to negate a previously specified

parameter; that is, revert to the behaviour that would occur if the

parameter had not been specified. This is intended to allow servers

to change their capabilities without disconnecting clients. Both

parameters with and without a value argument may be negated; however,

the value argument is not supplied. It is not required to negate a

parameter in order to change its value, the server should merely

re-advertise the parameter with the new value.


The server may negate tokens which have not been previously

advertised to the client; in this case, the client should ignore the

negation.


The server may not advertise and negate the same parameter, nor

advertise the same parameter with different value specifiers, in the

same ISUPPORT numeric reply. However, the server is free to

advertise or negate the same parameters in separate replies.


The server MUST NOT negate a parameter which does not have a

meaningful default value.


[Note: Implementations often change the value of a particular

parameter upon certain events, such as a successful OPER command

from a client. It is important that any relevant parameters be

(re)advertised when this occurs.]







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3. Currently defined parameters


A number of parameters are currently used in the IRC community, and

it is believed to be beneficial to standardise these. They are

listed below, with relevant information.


[Note: It is intended and expected that future documents will

update and extend the set of defined parameters; this is not meant

to be an exhaustive list.]


3.1 CASEMAPPING


o CASEMAPPING=string


The CASEMAPPING parameter allows the server to specify which method

it uses to compare equality of case-insensitive strings. Possible

values are:


o "ascii": The ASCII characters 97 to 122 (decimal) are defined as

the lower-case characters of ASCII 65 to 90 (decimal). No other

character equivalency is defined.

o "rfc1459": The ASCII characters 97 to 126 (decimal) are defined as

the lower-case characters of ASCII 65 to 94 (decimal). No other

character equivalency is defined.

o "strict-rfc1459": The ASCII characters 97 to 125 (decimal) are

defined as the lower-case characters of ASCII 65 to 93 (decimal).

No other character equivalency is defined.


[Note: The only difference between "rfc1459" and "strict-rfc1459"

is that the characters "~" and "^" are not considered equivalent

in the "strict-rfc1459" encoding. This is believed to be an

mistake in the specification of character equivalency in RFC 1459

[5]; the majority of IRC server implementations known to the

author treat these characters as equivalent (however, see Section

4.5).]


The CASEMAPPING token requires a value.


The default value for CASEMAPPING is "rfc1459". While this differs

from the historical definition in RFC 1459 [5], it is believed to

reflect current IRC server implementations, and is as such more

useful.


3.2 CHANLIMIT


o CHANLIMIT=pfx:num[,pfx:num,...]


This parameter specifies the maximum number of channels that a client




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may join. The value is a series of "pfx:num" pairs, where 'pfx'

refers to one or more channel prefix characters (as specified in

CHANTYPES), and 'num' indicates how many of these types of channel

the client may join in total. If there is no limit to the number of

certain channel type(s) a client may join, the limit should be

specified as the empty string, for example "#:".


[Example: CHANLIMIT=#+:10,&: indicates that a client may join up to

10 '#' and '+' channels (for example, 7 '#' channels and 3 '+'

channels), and any number of '&' channels.]


Clients on either this server or a remote server may be on more than

this number of channels; this parameter is only intended for

information on how many channels the client it is advertised to may

join.


There is no default value for the CHANLIMIT token.


The CHANLIMIT token requires a value.


3.3 CHANMODES


o CHANMODES=A,B,C,D


The CHANMODES token specifies the modes that may be set on a channel.

These modes are split into four categories, as follows:


o Type A: Modes that add or remove an address to or from a list.

These modes always take a parameter when sent by the server to a

client; when sent by a client, they may be specified without a

parameter, which requests the server to display the current

contents of the corresponding list on the channel to the client.

o Type B: Modes that change a setting on the channel. These modes

always take a parameter.

o Type C: Modes that change a setting on the channel. These modes

take a parameter only when set; the parameter is absent when the

mode is removed both in the client's and server's MODE command.

o Type D: Modes that change a setting on the channel. These modes

never take a parameter.


If the server sends any additional types after these 4, the client

MUST ignore them; this is intended to allow future extension of this

token.


The IRC server MUST NOT list modes in CHANMODES which are also

present in the PREFIX parameter; however, for completeness, modes

described in PREFIX may be treated as type B modes.





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If the server does not support any modes corresponding to a

particular type, it should advertise that type as the empty string.


[Example: A server supporting no channel modes would advertise

"CHANMODES=,,,".]

[Example: CHANMODES=b,k,l,imnpst]


The CHANMODES token requires a value.


There is no default value for the CHANMODES token.


3.4 CHANNELLEN


o CHANNELLEN=number


The CHANNELLEN parameter specifies the maximum length of the name of

a channel that may be created by a client. The server may make known

to the client a channel with a name longer than that specified in

this value -- that is, the client must not depend on a channel's name

never being longer than this.


The CHANNELLEN token does not require a value; if none is given,

channel names are not limited in length. If a value is given, it

must be numeric.


The default value for CHANNELLEN is 200; this corresponds to RFC 1459

[5].


3.5 CHANTYPES


o CHANTYPES=chars


The CHANTYPES parameter specifies the valid characters to begin a

channel name.


[Example: CHANTYPES=+#& defines that channels names may begin with

either +, #, or &; for example, #mychannel.]


The default value for CHANTYPES is "CHANTYPES=#&", which corresponds

to RFC 1459 [5]. It SHOULD NOT be specified if the server supports

exactly these channel types.


The CHANMODES parameter does not require a value; if none is given,

the server does not support any channel types.


3.6 EXCEPTS






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o EXCEPTS[=modechar]


The EXCEPTS parameter indicates that the server supports "ban

exceptions" (channel mode +e), as defined in RFC 2811 [3], section

4.3.1. The optional value argument to EXCEPTS indicates which channel

mode is used for ban exceptions. If the token is specified with no

value, it is assumed that mode +e is used.


The default value for EXCEPTS is that channel exceptions are not

supported.


3.7 IDCHAN


o IDCHAN=pfx:num[,pfx:num,...]


The IDCHAN parameter indicates the existence of "safe" channels as

described in RFC 2811 [3], and the length of the "id" portion of

those channel names.


Each mode:num pair indicates one or more channel name prefixes which

corresponds to a "safe" channel, and the length of the ID portion of

those channels' name.


[Example: IDCHAN=!:5 means the client should expect IDs which are 5

characters in length on "!" channels; for example "!JNB4Sircd",

where "JNB4S" is the ID and "ircd" is the channel's short name.]


The IDCHAN token requires a value.


The default value for IDCHAN is no value; that is, there are no

"safe" channel types.


3.8 INVEX


o INVEX[=modechar]


The INVEX parameter indicates that the server supports "invite

exceptions", as defined in RFC 2811 [3], section 4.3.2. The optional

value argument to INVEX indicates which channel mode is used for

invite exceptions. If the token is specified with no value, it is

assumed that mode +I is used.


The default value for INVEX is that channel invite exceptions are not

available.


3.9 KICKLEN






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o KICKLEN=number


The KICKLEN parameter specifies the maximum length of a KICK message

that a client may use. Note that it only specifies the length the

client should send to the server -- the server may send KICK messages

with a length longer than this value.


The KICKLEN token does not require a value; if none is given, KICK

messages are not limited in length. If a value is given, it must be

numeric.


There is no default value for the KICKLEN token.


3.10 MAXLIST


o MAXLIST=mode:num[,mode:num,...]


This parameter specifies the maximum numbers of 'list modes' (type A

modes in CHANMODES) that a client may set on a channel at one time.

Note that this MUST only be interpreted as applying to new modes

which are set by clients -- it should not be used to infer the

maximum length of any mode lists returned by the server.


The parameter is a series of mode-number pairs, each of which

specifies one or more type A modes, along with the maximum size of

the associated list for those modes. Modes which are specified in

the same pair share the same maximum size.


[Example: Given "b:25,eI:50", it would be possible to set up to 25

"+b" modes, and up to 50 of a combination of "+e" and "+I" modes,

e.g. 30 "+e" and 20 "+I" modes, making up a total of 50.]

[Example: MAXLIST=b:25 indicates that 25 bans may be set on a

channel at one time.]


The MAXLIST token requires a value.


There is no default value for the MAXLIST token.


3.11 MODES


o MODES=number


This parameter specifies the maximum number of "variable" modes which

may by set on a channel by a single MODE command from a client. A

"variable" mode is defined as being type A, B and C modes as defined

for CHANMODES, and channel modes specified in the PREFIX parameter.






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[Example: MODES=3 indicates that 3 modes may be set with a MODE

command.]


The value of MODES does not limit the number of modes in a MODE

command which is sent from the server to the client; the client MUST

NOT rely on this being the case.


The default value for the MODES parameter is 3, which corresponds to

RFC 1459 [5].


The MODES token does not require a value; if none is given, the

number of modes which may be set in one command is not limited. If a

value is given, it must be numeric.


3.12 NETWORK


o NETWORK=name


The NETWORK parameter defines the name of the IRC network that the

client is connected to.


[Example: NETWORK=EFnet indicates that the client is connected to

the EFnet IRC network.]


Note that this parameter is intended only for user display purposes;

the client SHOULD NOT assume further capabilities or features of the

IRC server based on the value of the NETWORK parameter.


The NETWORK token requires a value.


The default value of the NETWORK token is no value; that is, the

network does not have a name specified.


3.13 NICKLEN


o NICKLEN=number


This parameter specifies the maximum nickname length that the client

may use in a nickname.


[Example: NICKLEN=9 indicates that clients may have nicknames up to

9 characters in length.]


This parameter does not restrict the length of any nicknames other

clients on the network may use.


The NICKLEN token requires a numeric value.





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The default value for NICKLEN is 9, which corresponds to RFC 1459

[5].


3.14 PREFIX


o PREFIX=[(modes)prefixes]


The PREFIX parameter specifies a list of channel status flags (the

"modes" section) that clients may have on channels, followed by a

mapping to the equivalent channel status flags ("prefixes"), which

are used in NAMES and WHO replies. There is a one to one mapping

between each mode and prefix.


The order of the modes is from that which gives most privileges on

the channel, to that which gives the least.


[Example: (ab)&* maps the channel mode 'a' to the channel status

flag '&', and channel mode 'b' to the channel status flag '*'.]


[Example: PREFIX=(ohv)@%+ maps channel mode 'o' to status '@', 'h'

to status '%', and 'v' to status +.


The default value for PREFIX is "PREFIX=(ov)@+", which corresponds to

RFC 1459 [5]. It SHOULD NOT be specified if the server provides only

these modes. If a server provides ANY additional status flags, it

MUST also provide (ov)@+ (assuming they are applicable to the

server). The PREFIX parameter may be advertised with a null value

specifier; this indicates that no prefixes are supported by the IRC

server.


Note that PREFIX does NOT specify whether or not the server sends

multiple prefix characters for a user in NAMES replies.


3.15 SAFELIST


o SAFELIST


The SAFELIST parameter indicates that the client may request a "LIST"

command from the server, without being disconnected due to the large

amount of data generated by the command.


The SAFELIST token must not be specified with a value.


The default value for the SAFELIST token is none; that is, the

client may not safely request a LIST command.







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3.16 STATUSMSG


o STATUSMSG=string


The server supports a method of sending a NOTICE message to only

those people on a channel with the specified status. This is done

via a NOTICE command, with the channel prefixed by the desired status

flag as the target.


[Example: NOTICE @#channel :Hi there]


The server should deliver the message to all users on the specified

channel with equal or higher status on the channel as the status flag

indicates.


[Example: STATUSMSG=@+ indicates that "@#channel" and "+#channel"

would be valid targets. A message to "+#channel" would deliver the

message to all users with voice and channel operator privileges on

#channel, assuming that the server supported the PREFIX value

(ov)@+.]


The required value argument to STATUSMSG indicates which prefixes

(from the PREFIX parameter) are valid status values for use in NOTICE

commands.


The server MUST NOT advertise a character in STATUSMSG which is also

present in CHANTYPES.


The STATUSMSG token requires a value.


The default value of the STATUSMSG token is none; that is, the

server does not support this form of messaging.


3.17 STD


o STD=version[,version[,...]]


The STD parameter indicates which form(s) of the ISUPPORT numeric are

used by the server. Currently, one only possible value is defined;

that is "rfcnnnn", which refers to this document.


[Note: To be changed by the RFC Editor before publication.]


The STD parameter is intended to be extensible, so that if later

standards emerge which update this document, the server may be able

to advertise this. The "version" string is free-form subject to the

requirements in section ABNF, however, protocol updates defined in

RFCs should be named "rfcxxxx", where "xxxx" is the relevant RFC




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number.


A server may support any number of STD versions. However, new version

strings MUST NOT be added unless there is an ambiguity between two

tokens defined with different meanings in two different standards. It

is expected that most new features may be advertised simply by

additional parameters, in which case a new version string is not

required.


The STD token MUST be the first token advertised by the server upon

connection.


The STD token requires a value.


The default value for the STD parameter is none; that is, no

standardised ISUPPORT is available.


3.18 TARGMAX


o TARGMAX=[cmd:lim,cmd:lim...]


The TARGMAX parameter specifies the maximum number of targets

allowable for commands which accept multiple targets. It consists of

a series of cmd:lim pairs, where each command 'cmd' allows up to

'lim' targets (generally either channels or nicks). In the case of

the KICK command, the limit indicates the maximum number of (user,

channel) pairs which may be specified in any one KICK command.


[Example: TARGMAX=PRIVMSG:4,NOTICE:3 would allow "PRIVMSG A,B,C,D

:message" and "NOTICE A,B,C :message", but not "PRIVMSG A,B,C,D,E

:message" or "NOTICE A,B,C,D :message".]


If no argument is given for a particular command (e.g. "WHOIS:"),

that command does not have a limit on the number of targets.


The server MUST specify all commands available to the user which

support multiple targets.


The default value of TARGMAX is that no commands allow multiple

targets. If this is the case, the server SHOULD NOT specify

"TARGMAX=".


3.19 TOPICLEN


o TOPICLEN=number


The TOPICLEN parameter specifies the maximum length of the topic

specified in the TOPIC command for a channel. Note that it only




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specifies the length of topic that may be set -- the server is free

to return topics longer than this length to the client.


The TOPICLEN token does not require a value; if none is given, the

length of channel topics is not limited.


The TOPICLEN token requires a numeric value.


4. Differences to existing implementations


A number of differences exist between the ISUPPORT defined in this

document and traditional implementations of the ISUPPORT numeric.


4.1 PREFIX parameter without value


The PREFIX parameter is traditionally not sent without a value

parameter; indeed, the author is not aware of any IRC server

implementations where this would be appropriate. However, it is

believed that this support is desired to allow extra flexibility,

while retaining compatibility with traditional PREFIX

implementations.


4.2 EXCEPTS and INVEX value argument


EXCEPTS and INVEX traditionally take no argument -- while they

indicate presence of these features on the server, they do not

specify the channel mode which is associated with these features. It

is believed that the argument value described here provides extra

flexibility while retaining backwards compatibility.


4.3 STATUSMSG / WALLCHOPS


The STATUSMSG parameter replaces the traditional WALLCHOPS parameter

used by some current implementations. It is believed that the name

STATUSMSG better reflects the functionality; since the argument to

STATUSMSG is not optional, it would break backwards compatibility to

use the name WALLCHOPS. It was not considered beneficial to allow a

STATUSMSG flag without a value.


4.4 Conflicts with RFC 2812


RFC 2812 [4], section 5.1, defines a numeric reply "RPL_BOUNCE", with

the associated number "005". While this conflicts with the ISUPPORT

numeric, it is considered that ISUPPORT has received much more

widespread support, and is the de facto standard for use of the 005

numeric. The only server implementation known to use this numeric

has now changed it to 010.





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RFC2812 is an Informational RFC and does not not specify an Internet

standard.


4.5 Default value for CASEMAPPING


The default value for CASEMAPPING ("rfc1459") was chosen because it

reflects the prevailing implementations of the IRC server software

currently in use. While some IRC servers have moved to the "ascii"

case mapping, those known to the author indicate this via

CASEMAPPING=ascii; therefore this is not believed to introduce any

compatibility problems.


4.6 CHANLIMIT / MAXCHANNELS


CHANLIMIT replaces the traditional MAXCHANNELS parameter. MAXCHANNELS

did not specify which types of channel(s) the limit applied to; many

server implementation did not apply the limit to server-local "&"

channels, for example. The token was renamed from MAXCHANNELS to

CHANLIMIT to prevent confusion.


4.7 MAXLIST / MAXBANS


MAXLIST replaces the traditional MAXBANS token. MAXBANS was

considered non-useful, because of its ambiguous meaning; two of the

largest IRC networks, for example, could not agree whether

"MAXBANS=x" was equivalent to "MAXLIST=beI:x" or

"MAXLIST=b:x,e:x,I:x". MAXLIST is also considerably more flexible;

to standardise either of the described behaviours for MAXBANS would

leave some IRC servers unable to accurately describe their

capabilities.


4.8 CHARSET


The traditional CHARSET parameter has been entirely removed. It was

found to be unworkable; a correct specification could not be devised

to represent its meaning across implementations. Several other

methods to implement the same functionality are under discussion but

are outside the scope of this document.


4.9 TARGMAX / MAXTARGETS


Traditional implementations use MAXTARGETS instead of TARGMAX.

However, TARGMAX allowed several commands to be specified (such as

WHOIS and KICK) whereas MAXTARGETS only applies to channels. TARGMAX

is also more extendable to cope with future changes.







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5. Security Considerations


This memo does not raise any security considerations.


Normative References


[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement

Levels", RFC 2119, March 1997.


[2] Crocker, D. and P. Overell, "Augumented BNF for Syntax

Specifications: ABNF", RFC 2234, November 1997.


[3] Kalt, C., "Internet Relay Chat: Channel Management", RFC 2811,

April 2000.


[4] Kalt, C., "Internet Relay Chat: Client Protocol", RFC 2812,

April 2000.


[5] Reed, D. and J. Oikarinen, "Internet Relay Chat Protocol", RFC

1459, May 1993.


Informative references


[6] Roeckx, K., "The 005 numeric", September 2002.



Author's Address


Edward Brocklesby

57 Williamson Way

Oxford, Oxon OX4 4TU

GB


EMail: ejb@goth.net


Appendix A. Default ISUPPORT values


As an aid to implementation, a standard ISUPPORT reply with all

values which may be assumed to be at their defaults upon connection

is supplied here (lines broken due to formatting requirements).



:irc.example.com 005 nickname :CASEMAPPING=rfc1459 CHANNELLEN=200

CHANTYPES=#& MODES=3 NICKLEN=9 PREFIX=(ov)@+ TARGMAX


In addition, the server must provide values for the following

parameters: CHANLIMIT, CHANMODES, KICKLEN, MAXLIST, STD, TOPICLEN.





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Appendix B. Acknowledgements


The author gratefully acknowledges the contributions of Bill Fenner

("fenestro"), Perry Lorier ("Isomer"), Kurt Roeckx ("Q") and John

Midgley ("CrazyEddy") in the preparation of this document.


This document is heavily based on a previous document entitled "The

005 numeric".












































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