NOTICE: The protocol defined herein is a Draft Standard of the XMPP Standards Foundation. Implementations are encouraged and the protocol is appropriate for deployment in production systems, but some changes to the protocol are possible before it becomes a Final Standard.
On the existing Jabber network, there are many opportunities to optimize stanza traffic. For example, clients that want to send the same stanza to multiple recipients currently must send multiple stanzas. Similarly, when a user comes online the server sends many nearly-identical presence stanzas to remote servers.
The 'http://jabber.org/protocol/address' specification provides a method for both clients and servers to send a single stanza and have it be delivered to multiple recipients, similar to that found in RFC 822 . As a side-effect, it also provides all of the functionality specified by the old 'jabber:x:envelope'  proposal, which this XEP can supersede.
The IM service MAY implement multicast directly, or it MAY delegate that chore to a separate service. A client can use the following approach to find a multicast-capable service hosted by its domain:
Send a disco#info request to the IM server; if its reply includes the 'http://jabber.org/protocol/address' feature, then it is a multicast-capable service.
If the IM server is not a multicast-capable service, send a disco#items request to the IM server; the IM server will then return a list of associated services.
Send a disco#info request to each of the services associated with the IM server; if one of the replies includes the 'http://jabber.org/protocol/address' feature, then that service is a multicast-capable service.
The multicast service MAY choose to limit which local users can use the service. The server MAY choose to limit whether non-local servers can send address headers that require the local server to send to third parties (relaying). In either case, if the server chooses to disallow the request, the server MUST return a Forbidden error (see the Error Conditions section below). In the relaying case, the server SHOULD NOT deliver to any of the addresses (even the local ones) if the sender is disallowed.
Implementations MAY choose to cache the disco response.
Positive responses MAY be cached differently than negative
responses. The result SHOULD NOT be cached for more than 24
hours, unless some sort of time-to-live information is
added to the Service Discovery protocol in the future.
Address values are packaged together into an
Each address to which the sender wants the stanza to be re-sent will show up as an <address/> in the <addresses/> element. There are several different types of address, shown below.
An <address/> element MUST possess a 'type' attribute, and MUST possess at least one of the 'jid', 'uri', 'node', and 'desc' attributes. An <address/> element MUST NOT possess both a 'jid' attribute and a 'uri' attribute. If sending through a multicast service, an address MUST include a 'jid' or a 'uri' attribute, unless it is of type 'noreply'.
The 'jid' attribute is used to specify a simple Jabber ID associated with this address. If the 'jid' attribute is specified, the 'uri' attribute MUST NOT be specified. Support for the 'jid' attribute is REQUIRED.
The 'uri' attribute is used to specify an external system address, such as a sip:, sips:, or im: URI. If the 'uri' attribute is specified, the 'jid' and 'node' attributes MUST NOT be specified. These URIs MUST be formatted as specified in their respective RFCs, however with the characters & < > ' " replaced by their equivalent XML escapes, & < > ' ". If a receiving entity does not understand the given URI scheme, or if the URI is not formatted correctly, a "JID Malformed" error SHOULD be returned. Support for the 'uri' attribute is OPTIONAL.
The 'node' attribute is used to specify a sub-addressable unit at a particular JID, corresponding to a Service Discovery node. A node attribute MAY be included if a 'jid' attribute is specified. If a 'uri' attribute is specified, a 'node' attribute MUST NOT be specified. Support for the 'node' attribute is RECOMMENDED.
The 'desc' attribute is used to specify human-readable information for this address. This data may be used by clients to provide richer address-book integration. This information is in the language of the sender, which MAY be identified using the standard xml:lang rules from XMPP Core . Support for the 'desc' attribute is RECOMMENDED.
When a multicast service delivers the stanza to a non-bcc address, it MUST add a delivered='true' attribute to the address element. A multicast service MUST NOT deliver to an address that was marked with a delivered='true' attribute when the service received the stanza. A multicast service SHOULD attempt to deliver to all addresses that are not marked with a delivered='true' attribute. The delivered attribute is used to prevent loops. See the Multicast Usage section below for more details. Support for the 'delivered' attribute is REQUIRED.
These addressees should receive 'blind carbon copies' of the stanza. This means that the server MUST remove these addresses before the stanza is delivered to anyone other than the given bcc addressee or the multicast service of the bcc addressee.
This is the address to which all replies are requested to be sent. Clients SHOULD respect this request unless an explicit override occurs. There MAY be more than one replyto or replyroom on a stanza, in which case the reply stanza MUST be routed to all of the addresses.
This is the JID of a Multi-User Chat (XEP-0045)  room to which responses should be sent. When a user wants to reply to this stanza, the client SHOULD join this room first. Clients SHOULD respect this request unless an explicit override occurs. There MAY be more than one replyto or replyroom on a stanza, in which case the reply stanza MUST be routed to all of the addresses.
This address type is used by Multi-User Chat (XEP-0045)  services. If a room is non-anonymous, the service MAY include an Extended Stanza Addressing (XEP-0033)  element that notes the original full JID of the sender by means of the "ofrom" address type
As specified herein, the <address/> element is empty. Implementations or future protocols MAY extend the <address/> element for additional functionality, but any extensions are out of scope for this XEP. Such extensions SHOULD be appropriately qualified with a new namespace, and any extensions that are not understood by an implementation MUST be ignored.
This specification can be used to, in effect, send directed
presence (see Section 4.6 of RFC 6121 ). In order to ensure
that entities that have received directed available presence
through the service also are informed when the originating
entity sends unavailable presence, the multicast service MUST
do the following:
Keep track of the entities to which it sends available
presence (i.e., presence stanzas with no 'type' attribute)
along with the originating entity of that presence.
Upon receiving a presence stanza of type "unavailable"
from an originating entity, broadcast that unavailable
presence to all entities to which it has send available
In this way, the multicast service ensures that all
entities which have received available presence through the
service also receive the associated unavailable presence.
The following usage scenario shows how messages flow through both address-enabled and non-address-enabled portions of the Jabber network.
Note: the logic associated with how to perform the following tasks is purely informational. A conforming service MUST generate output as if these rules had been followed, but need not (and probably will not) use this algorithm.
User desires to send a stanza to more than one
Client determines the JID of a multicast service,
using Service Discovery.
If no multicast service is found, the client MAY
choose to deliver each stanza individually, or it MAY
query each of the servers associated with desired
recipients, and batch stanzas to those servers
If a multicast service is found, the client constructs
a stanza with an address block, and sends it to the
multicast service. (Note: For the following rules, any
address that was marked on the incoming address header
with delivered='true' is never re-delivered.)
The server checks to see if it can deliver to all of
the specified addresses. If not, the stanza is returned
with a "Forbidden" error, and processing stops.
The server adds a delivered='true' attribute to all
The server removes all type='bcc' attributes.
The server delivers the stanza to all of the 'to',
'cc', and 'bcc' addresses from the original address header that
are being handled locally. The server replaces the
'to' attribute on the outer stanza with the JID of each
addressee. Each 'bcc' recipient MUST receive only the
<address type='bcc'/> associated with that
For each non-local server (the 'target server') that
has addresses specified in 'to', 'cc', or 'bcc' addresses
in the original address header, the local server determines
whether the target server supports multicast, using Service
If the target server does not support address headers, the
local server sends a copy of the stanza to each address,
with the 'to' attribute on the outer stanza set to the JID
of the given addressee.
If the target server does support address headers, the server
removes the delivered='true' attributes on each of the
addresses bound for that server, and replaces the 'to'
attribute on the outer stanza with the adress of the
multicast service for the target server. The 'bcc'
addresses for the target server from the original address header
are added back to the address header. A single stanza is sent to
the target server.
When replying to a message stanza that contains an extended
address, the following rules apply:
If a noreply address is
specified, a reply SHOULD NOT be generated.
If one or more replyroom addresses are specified, the client SHOULD
join the specified chat rooms instead of replying directly
to the specified users. No further extended address
processing is required.
If one or more replyto address are specified, the reply SHOULD go
to the specified addresses. No further extended address
processing is required. Any <thread/> element from
the initial message MUST be copied into the replies.
Otherwise, an extended-address aware client MUST copy
the address header from the original message into the reply,
removing any delivered attributes. If the original sender
is not in the copied list, the original sender MUST be
added as a 'to' address. The recipient's address SHOULD
be removed from the list. The client then proceeds with
the rules from the Multicast Usage
section above for delivery of the message.
A recipient SHOULD trust a stanza's extended addressing headers only as much as it trusts the sender of the stanza.
Furthermore, there exists the potential for abuse related to the 'replyto' and 'replyroom' features (e.g., an entity could send messages with 'replyroom' set to the address of a room that hosts salacious content or with 'replyto' set to the address of a spambot that harvests Jabber addresses). Therefore if a human user's receiving application receives a message with extended stanza addressing that specifies a 'replyto' or 'replyroom' address other than that of the sender, it SHOULD inform the user of that fact. (Naturally, the receiving application MAY also limit the entities to which the recipient can reply using privacy lists as specified in XMPP IM .)
Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.
Disclaimer of Warranty
## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ##
Limitation of Liability
In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.
This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA).
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The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.
The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".
8. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.
9. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>.
Editorial cleanups, rearrangement. Allowed IQ's
in certain cases. Clarified node rules. Changed
delivered='yes' to delivered='true'. Noreply shouldn't
imply no other addresses. Clarified when authorization
checks take place. Remove own address on reply. Bad URI
Changed namespace to
'http://www.jabber.org/protocol/address', and removed one
level of nesting, since addresses are the only block left.
Made it clearer that the session manager can implement
multicast directly. Removed infobits (needs to be a
separate specification). Reworked the examples to be more correct.
Added reply handling rules. Added schema.