| TOC |
|
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 Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 7, 2002.
Copyright (C) The Internet Society (2001). All Rights Reserved.
This memo describes the APEX publish-subscribe service, addressed as the well-known endpoint "apex=pubsub". The pubsub service is used to manage subscriber lists for a set of topical distribution groups, and to forward messages to group subscribers.
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| TOC |
Multicast is a form of one-to-many distribution of datagrams. Its perceived strength relies on the "network" (in whatever form it is realized), rather than the source, replicating traffic to the different receivers of a group. The replication topology is a tree of nodes overlayed on top of a physical network. Traditionally, multicast has been viewed as a network layer service in which replication is done by routers.
In this document we describe an application-level multicast service. Rather than relying on IP layer multicast[1], the service distributes information through an APEX[2] "relay mesh". The APEX relaying mesh uses BEEP[3], which in turn runs on top of TCP[4]. This last point allows the service to adapt to congestion in a fashion that is TCP-friendly.
An application-level multicast service could, for example, allow implementation of a messaging "exploder" that performs a single store-and-forward delivery of a group-addressed message across a trans-oceanic link, after which point messages are delivered to multiple recipients on the remote side of the link. The service can be deployed using static tree configuration, and possibly later augmented with a protocol for automating tree configuration.
The service we describe is called the APEX publish-subscribe (pubsub) service. The pubsub service is used to manage subscriber lists for a set of topical distribution groups, and to forward messages to group subscribers.
APEX, at its core, provides a best-effort datagram service. Within an administrative domain, all relays must be able to handle messages for any endpoint within that domain. APEX services are logically defined as endpoints but given their ubiquitous semantics they do not necessarily need to be associated with a single physical endpoint. As such, they may be provisioned co-resident with each relay within an administrative domain, even though they are logically provided on top of the relaying mesh, i.e.,
+----------+ +----------+ +----------+ +---------+
| APEX | | APEX | | APEX | | |
| access | | pubsub | | presence | | ... |
| service | | service | | service | | |
+----------+ +----------+ +----------+ +---------+
| | | |
| | | |
+----------------------------------------------------------------+
| |
| APEX core |
| |
+----------------------------------------------------------------+
That is, applications communicate with an APEX service by exchanging data with a "well-known endpoint" (WKE).
APEX applications communicate with the pubsub service by exchanging data with the well-known endpoint "apex=pubsub" in the corresponding administrative domain, e.g., "apex=pubsub@example.com" is the endpoint associated with the pubsub service in the "example.com" administrative domain.
Note that within a single administrative domain, the pubsub service makes use of the APEX access[5] service to determine whether an originator is allowed to manage topic and subscription information, and whether an originator is allowed to publish to a given topic.
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The APEX pubsub service manages a list of named topics and a list of subscribers for each topic, and implements delivery for group-addressed messages using the underlying APEX relay service.
The pubsub service uses hierarchical topic names similar to NNTP[6] group names. Unlike NNTP's global newsgroup namespace, the pubsub service defines a distinct topic name space per administrative domain. The allocation of the topic name space, including any conventions applied at particular levels in the hierarchy, is an issue for each local administrative domain. Each administrative domain is also responsible for setting access control policy for pubsub operations, and for maintaining state on stable storage about the currently existing set of topics and subscribers for each topic.
Each of the topic and subscription management operations is described in the subsections below.
When an application wants to define a new topic to which group-delivery messages can be addressed, it sends a createtopic operation to the service, e.g.,
+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='mike@example.com' />
<recipient identity='apex=pubsub@example.com' />
<data-content Name='Content'>
<createtopic topic='music.jazz.milesdavis'
transID='1' />
</data-content>
</data>
S: <ok />
The service immediately responds with a reply operation containing the same transaction-identifier, e.g.,
+-------+ +-------+
| | <------- data -- | |
| relay | | pubsub|
| | -- ok ---------> | svc. |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=pubsub@example.com' />
<recipient identity='mike@example.com' />
<data-content Name='Content'>
<reply code='250' transID='1' />
</data-content>
</data>
S: <ok />
When an application wants to delete an existing topic, it sends a deletetopic operation to the service, e.g.,
+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='mike@example.com' />
<recipient identity='apex=pubsub@example.com' />
<data-content Name='Content'>
<deletetopic topic='music.jazz.milesdavis'
transID='2' />
</data-content>
</data>
S: <ok />
The service immediately responds with a reply operation containing the same transaction-identifier, e.g.,
+-------+ +-------+
| | <------- data -- | |
| relay | | pubsub|
| | -- ok ---------> | svc. |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=pubsub@example.com' />
<recipient identity='mike@example.com' />
<data-content Name='Content'>
<reply code='250' transID='2' />
</data-content>
</data>
S: <ok />
When an application wants to get a list of existing topics, it sends a listtopics operation to the service, e.g.,
+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='mike@example.com' />
<recipient identity='apex=pubsub@example.com' />
<data-content Name='Content'>
<listtopics />
</data-content>
</data>
S: <ok />
The service immediately responds with a topiclist operation containing the list of topics registered with its administrative domain, e.g.,
+-------+ +-------+
| | <------- data -- | |
| relay | | pubsub|
| | -- ok ---------> | svc. |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=pubsub@example.com' />
<recipient identity='mike@example.com' />
<data-content Name='Content'>
<topiclist>
<topic name="music.jazz.milesdavis" />
<topic name="music.classicrock.zeppelin" />
</topiclist>
</data-content>
</data>
S: <ok />
In addition to the topiclist operation, applications can track changes to the topic list via the APEX presence service[7]. This approach is discussed is more detail later.
When an application wants to subscribe to a topic it sends a subscribe operation to the service, e.g.,
+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='mike@example.com' />
<recipient identity='apex=pubsub@example.com' />
<data-content Name='Content'>
<subscribe subscriber='mike@example.com'
topic='music.jazz.milesdavis'
duration='9999999'
transID='3' />
</data-content>
</data>
S: <ok />
The service immediately responds with a reply operation containing the same transaction-identifier, e.g.,
+-------+ +-------+
| | <------- data -- | |
| relay | | pubsub|
| | -- ok ---------> | svc. |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=pubsub@example.com' />
<recipient identity='mike@example.com' />
<data-content Name='Content'>
<reply code='250' transID='3' />
</data-content>
</data>
S: <ok />
Either the subscriber or the service may cancel a subscription by sending a cancel operation., e.g.,
+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='mike@example.com' />
<recipient identity='apex=pubsub@example.com' />
<data-content Name='Content'>
<cancel topic='music.jazz.milesdavis' transID='4' />
</data-content>
</data>
S: <ok />
+-------+ +-------+
| | <------- data -- | |
| relay | | pubsub|
| | -- ok ---------> | svc. |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=pubsub@example.com' />
<recipient identity='mike@example.com' />
<data-content Name='Content'>
<reply code='250' transID='4' />
</data-content>
</data>
S: <ok />
or
+-------+ +-------+
| | <------- data -- | |
| relay | | pubsub|
| | -- ok ---------> | svc. |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=pubsub@example.com' />
<recipient identity='mike@example.com' />
<data-content Name='Content'>
<cancel topic='music.jazz.milesdavis' transID='99' />
</data-content>
</data>
S: <ok />
Servicing publish/subscribe activity from a single location would present scaling problems. To support distributed subscriber management, individual administrative domains can field pubsub servers that send subscribe and cancel requests to other pubsub servers. In this fashion, it is possible to construct a distributed tree of servers that handle publish and subscribe activity. Whether this set of servers is configured manually or through an automated tree formation protocol is outside the scope of the current document.
When a pubsub server wants to act as a distributor for a particular topic it sends a subscribe operation to the service, using the appropriate subaddress as the originator, e.g.,
+-------+ +-------+
| pubsub| -- data -------> | |
| svc. | | relay |
| #2 | <--------- ok -- | |
+-------+ +-------+
C: <data content='#Content'>
<originator
identity='apex=pubsub/music.jazz.milesdavis@redistr.com' />
<recipient identity='apex=pubsub@example.com' />
<data-content Name='Content'>
<subscribe
subscriber=
'apex=pubsub/music.jazz.milesdavis@redistr.com'
topic='music.jazz.milesdavis'
duration='9999999'
transID='5' />
</data-content>
</data>
S: <ok />
The service immediately responds with a reply operation containing the same transaction-identifier, e.g.,
+-------+ +-------+
| | <------- data -- | pubsub|
| relay | | svc. |
| | -- ok ---------> | #1 |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=pubsub@example.com' />
<recipient
identity='apex=pubsub/music.jazz.milesdavis@redistr.com' />
<data-content Name='Content'>
<reply code='250' transID='5' />
</data-content>
</data>
S: <ok />
Similarly, a pubsub server would send a cancel request using the appropriate subaddress as the originator.
Additional processing steps are needed to handle the case where pubsub servers themselves may originate subscribe and cancel requests. Specifically, when any subscribe or cancel request is received, the receiving server must first check whether the originator falls within the administrative domain of a redistributing pubsub server for the given topic, and if so, the subscribe or cancel request is forwarded to that pubsub server. The Subscribe Operation and The Cancel Operation present the algorithmic details.
It is a local provisioning decision whether a redistributing pubsub server advertises its presence to end users.
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To publish a message to subscribers of a particular topic, an application sends an APEX data message to the service, using subaddressing to specify the topic for which group delivery is desired, e.g.,
+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | |
+-------+ +-------+
C: <data content='cid:2@example.com'>
<originator identity='mike@example.com' />
<recipient
identity='apex=pubsub/music.jazz.milesdavis@example.com' />
</data>
--boundary
Content-Type: application/beep+xml
Content-ID: <2@example.com>
<album>
<artist>Miles Davis</artist>
<title>Kind of Blue</title>
<date>1959</date>
<tracks>
<track>So What</track>
<track>Freddie Freeloader</track>
<track>Blue in Green</track>
<track>All Blues</track>
<track>Flamenco Sketches</track>
<track>Flamenco Sketches (Alternate Take)</track>
</tracks>
</album>
--boundary--
S: <ok />
In response, the service forwards the message content to each subscriber of the subaddress-named topic, rewriting the message to contain a list of recipients so that the APEX core will relay the message to each subscriber in turn:
+-------+ +-------+
| | <------- data -- | |
| | | pubsub|
| | -- ok ---------> | svc. |
| | +-------+
+-------+ | |
| | <------- data -- | |
| sub 1 | | relay |
| | -- ok ---------> | |
+-------+ | |
+-------+ | |
| | <------- data -- | |
| sub 2 | | |
| | -- ok ---------> | |
+-------+ +-------+
...
C: <data content='cid:2@example.com'>
<originator
identity='apex=pubsub/music.jazz.milesdavis@example.com' />
<recipient identity='subscriber1@example.com' />
<recipient identity='subscriber2@example.com' />
</data>
--boundary
Content-Type: application/beep+xml
Content-ID: <2@example.com>
<album>
<artist>Miles Davis</artist>
<title>Kind of Blue</title>
<date>1959</date>
<tracks>
<track>So What<track>
<track>Freddie Freeloader<track>
<track>Blue in Green<track>
<track>All Blues<track>
<track>Flamenco Sketches<track>
<track>Flamenco Sketches (Alternate Take)<track>
</tracks>
</album>
--boundary--
S: <ok />
This subaddress-based topic naming is used rather than defining an explicit "publish" operation so that sending and receiving applications need not be aware that they are participating in group delivery transmissions. The placement of multiple subscribers within a pubsub message realizes the benefit of a single message being replicated N times by the APEX relay mesh, versus the transmission of N messages by the publisher (source) to the relay mesh.
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Registration: The Pubsub Service contains the APEX service registration for the pubsub service:
An implementation of the service must maintain information about in-progress operations in persistent storage.
Consult Section 6.1.1 of [2] for a discussion on the properties of long-lived transaction-identifiers.
Section 4.1 of [2] describes how arbitrary MIME content is exchanged as a BEEP[3] payload. For example, to transmit:
<data content='...'>
<originator identity='mike@example.com' />
<recipient
identity='apex=pubsub/music.jazz.milesdavis@example.com' />
</data>
where "..." refers to: <FavoriteAlbum title="Kind of Blue" />
then the corresponding BEEP message might look like this:
MSG 1 1 . 42 1234
Content-Type: multipart/related; boundary="boundary";
start="<1@example.com>";
type="application/beep+xml"
--boundary
Content-Type: application/beep+xml
Content-ID: <1@example.com>
<data content='cid:2@example.com'>
<originator identity='mike@example.com' />
<recipient
identity='apex=pubsub/music.jazz.milesdavis@example.com' />
</data>
--boundary
Content-Type: application/beep+xml
Content-ID: <2@example.com>
<FavoriteAlbum title="Kind of Blue" />
--boundary--
END
or this:
MSG 1 1 . 42 1234
Content-Type: application/beep+xml
<data content='#Content'>
<originator identity='mike@example.com' />
<recipient
identity='apex=pubsub/music.jazz.milesdavis@example.com' />
<data-content Name='Content'>
<FavoriteAlbum title="Kind of Blue" />
</data-content>
</data>
END
When an application wants to create a new topic to which subscribe operations and data transmissions can refer, it sends a "createtopic" element to the service.
The "createtopic" element has a "topic" attribute, a "transID" attribute, and no content:
When the service receives a "createtopic" element, the service performs these steps:
When sending the "reply" element, the "transID" attribute is identical to the value found in the "createtopic" element sent by the originator.
When an application wants to delete an existing topic (i.e., one for which a previous createtopic operation completed successfully), it sends a "deletetopic" element to the service.
The "deletetopic" element has a "topic" attribute, a "transID" attribute, and no content:
When the service receives a "deletetopic" element, the service performs these steps:
When sending the "reply" element, the "transID" attribute is identical to the value found in the "deletetopic" element sent by the originator.
Note that following a deletetopic operation, data transmissions refering to this topic may continue to be propagated. Although the service will all no new data transmissions to start refering to this topic, in-progress data transmissions may be in transit.
When an application wants to get a list of existing topics, it sends a "listtopics" element to the service.
The "listtopics" element has no content.
When the service receives a "listtopics" element, the service performs these steps:
When an application wants to receive forwarded messages sent to the service via the data transmissions sent to a particular topic (subaddress) at a domain, it sends a "subscribe" element to the service.
The "subscribe" element has a "subscriber" attribute, a "topic" attribute, a "transID" attribute, a "duration" attribute, and no content:
When the service receives a "subscribe" element, we refer to the "subscriber" attribute of the "subscribe" element as the "subject", and the service performs these steps:
When sending the "reply" element, the "transID" attribute is identical to the value found in the "subscribe" element sent by the originator.
When an application no longer wishes to subscribe to a particular topic, it sends an "cancel" element to the service; similarly, when the service no longer considers an application to be subscribing, an "cancel" element is sent to the application.
The "cancel" element has a "subscriber" attribute, a "topic" attribute, a "transID" attribute, and no content:
When the service receives an "cancel" element, we refer to the "subscriber" attribute of the "subscribe" element as the "subject", and the service performs these steps:
When sending the "reply" element, the "transID" attribute is identical to the value found in the "subscribe" element sent by the originator.
Note that following a cancel operation, the originator may receive further data transmissions directed to the specified topic. Although the service will forward no new data after processing a cancel operation and sending the reply operation, earlier transmissions may be in transit.
When an application wants to transmit information to other applications subscribed to a particular topic within an administrative domain, it sends data to the apex=pubsub service at the given administrative domain using the APEX "data" operation, with the subaddress set to the desired topic. When the service receives a data operation so addressed, it performs the following steps:
To detect misconfigurations that cause forwarding loops in the APEX relaying mesh, the APEX pubsub service re-introduces a mechanism similar to the IP TTL[9] mechanism, in the form of an APEX option. Registration: The dataHopping Option contains the APEX option registration for the "dataHopping" option.
If this option is present in the "data" operation (c.f., Section 4.4.4 of [2]) and the value of the "noMoreThan" attribute is non-zero, then:
Further, note that because this option is processed on a per-hop basis, the originator must set the "targetHop" attribute to the value "all" and the "mustUnderstand" attribute to the value "true".
If the APEX report service (c.f., Section 6.2 of [2]) is invoked to send an error report, it issues a data operation with:
For example:
+-------+ +-------+
| | -- data -------> | |
| appl. | | relay |
| | <--------- ok -- | #1 |
+-------+ +-------+
C: <data content='cid:1@example.com'>
<originator identity='appl=pubsub/topic=fred@example.com' />
<recipient identity='barney@example.com' />
<option internal='dataHopping' targetHop='all'
mustUnderstand='true' transID='86' />
<dataHopping noMoreThan='2' reportErrors='true' />
</option>
</data>
S: <ok />
+-------+ +-------+
| | -- data -------> | |
| relay | | relay |
| #1 | <--------- ok -- | #2 |
+-------+ +-------+
C: <data content='cid:1@example.com'>
<originator identity='appl=pubsub/topic=fred@example.com' />
<recipient identity='barney@example.com' />
<option internal='dataHopping' targetHop='all'
mustUnderstand='true' transID='86' />
<dataHopping noMoreThan='1' reportErrors='true' />
</option>
</data>
S: <ok />
relay #2 determines that further relaying is necessary:
+-------+ +-------+
| | <------- data -- | |
| relay | | relay |
| #1 | -- ok ---------> | #2 |
+-------+ +-------+
C: <data content='#Content'>
<originator identity='apex=report@example.com' />
<recipient identity='appl=pubsub/topic=fred@example.com' />
<data-content Name='Content'>
<statusResponse transID='86'>
<destination identity='barney@example.com'>
<reply code='550' />
</destination>
</statusResponse>
</data-content>
</data>
S: <ok />
While processing operations, the service may respond with a "reply" element. Consult Sections 10 and 6.1.2 of [2], respectively, for the definition and an exposition of the syntax of the reply element.
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- Well-Known Endpoint:
- apex=pubsub
- Syntax of Messages Exchanged:
- c.f., The Pubsub Service DTD
- Sequence of Messages Exchanged:
- c.f., The Pubsub Service
- Access Control Tokens:
- pubsub:createtopic, pubsub:deletetopic, pubsub:listtopics, pubsub:subscribe, pubsub:cancel, core:data
- Contact Information:
- c.f., the "Authors' Addresses" section of this memo
The APEX option registration template is defined in Section 7.1 of [2].
- Option Identification:
- dataHopping
- Present in:
- APEX's "data" element
- Contains:
- dataHopping (c.f., The dataHopping Option DTD)
- Processing Rules:
- c.f., The dataHopping Option
- Contact Information:
- c.f., the "Authors' Addresses" section of this memo
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<!--
DTD for the APEX pubsub service, as of 2001-09-16
Refer to this DTD as:
<!ENTITY % APEXPUBSUB PUBLIC "-//IETF//DTD APEX PUBSUB//EN" "">
%APEXPUBSUB;
-->
<!ENTITY % APEXCORE PUBLIC "-//IETF//DTD APEX CORE//EN" "">
%APEXCORE;
<!--
DTD data types:
entity syntax/reference example
====== ================ =======
topic
TOPIC [a-z][a-z0-9.-_]* finance.vc.findandflip
c.f., Section x.x
-->
<!ENTITY % TOPIC "CDATA">
<!--
Synopsis of the APEX pubsub service
service WKE: apex=pubsub
message exchanges:
consumer initiates service replies
================== ================
createtopic reply
deletetopic reply
listtopics topiclist
subscribe reply
cancel reply
service initiates consumer replies
================= ================
cancel (nothing)
access control:
operation subject token
----------- ---------- ------------------
createtopic apex=pubsub pubsub:createtopic
deletetopic apex=pubsub pubsub:deletetopic
listtopics apex=pubsub pubsub:listtopics
subscribe apex=pubsub/topic pubsub:subscribe
cancel apex=pubsub/topic pubsub:cancel
data apex=pubsub/topic core:data
-->
<!ELEMENT createtopic EMPTY>
<!ATTLIST createtopic
topic %TOPIC; #REQUIRED
transID %UNIQID; #REQUIRED>
<!ELEMENT deletetopic EMPTY>
<!ATTLIST deletetopic
topic %TOPIC; #REQUIRED
transID %UNIQID; #REQUIRED>
<!ELEMENT listtopics EMPTY>
<!ELEMENT subscribe EMPTY>
<!ATTLIST subscribe
subscriber %ENDPOINT; #REQUIRED
topic %TOPIC; #REQUIRED
transID %UNIQID; #REQUIRED
duration %SECONDS; #REQUIRED>
<!ELEMENT cancel EMPTY>
<!ATTLIST cancel
topic %TOPIC; #REQUIRED
transID %UNIQID; #REQUIRED>
<!ELEMENT topiclist (topic*)>
<!ELEMENT topic EMPTY>
<!ATTLIST name %TOPIC; #REQUIRED>
<!--
DTD data types:
entity syntax/reference example
====== ================ =======
hopcount
HOPS 0..255 17
-->
<!ENTITY % HOPS "CDATA">
<!ELEMENT dataHopping EMPTY>
<!ATTLIST dataHopping
noMoreThan %HOPS; "0"
reportErrors
(true|false) "false">
| TOC |
Consult [2]'s Section 11 for a discussion of APEX security issues.
The APEX access[5] service provides considerable flexibility to administrators. For example:
To implement a policy that only allows applications within the example.com administrative domain to create and delete topics in that administrative domain, the APEX access service would contain the entry:
<access owner='apex=pubsub@example.com'
actor='*@example.com'
actions='pubsub:createtopic pubsub:deletetopic' />
To implement a policy that allows any application to subscribe to the music.jazz.milesdavis topic in the example.com administrative and that allows a pubsub server in the forwarder.com domain to handle distributed subscription management for this topic, the APEX access service would contain the entries:
<access owner='apex=pubsub/music.jazz.milesdavis@example.com'
actor='*@*'
actions='pubsub:subscribe' />
<access owner='apex=pubsub/music.jazz.milesdavis@example.com'
actor='apex=pubsub/music.jazz.milesdavis@forwarder.com'
actions='pubsub:subscribe' />
To implement a policy that allows anyone to publish to the music.jazz.milesdavis topic in the example.com administrative domain, the APEX access service would contain the entry:
<access owner='apex=pubsub/music.jazz.milesdavis@example.com'
actor='*@*'
actions='core:data' />
To add an exception list stating that mr.slate@example.com is not allowed to publish to this topic, the APEX access service would contain the above entry and also this entry:
<access owner='apex=pubsub/music.jazz.milesdavis@example.com'
actor='mr.slate@example.com'
actions='' />
To implement a policy that only allows people who are subscribed to a topic to publish to that topic, the pubsub service would update the set of access entries whenever a subscribe or cancel operation was successfully performed. For example, when user barney@rubble.com subscribes to the music.jazz.milesdavis topic in the example.com administrative domain, the following token would be added to the APEX access service:
<access owner='apex=pubsub/music.jazz.milesdavis@example.com'
actor='barney@rubble.com'
actions='core:data' />
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| [1] | Deering, S., "Host extensions for IP multicasting", STD 5, RFC 1112, August 1989. |
| [2] | Rose, M., Klyne, G. and D. Crocker, "The Application Exchange Core", draft-ietf-apex-core-05 (work in progress), August 2001. |
| [3] | Rose, M., "The Blocks Extensible Exchange Protocol Core", RFC 3080, March 2001. |
| [4] | Rose, M., "Mapping the BEEP Core onto TCP", RFC 3081, March 2001. |
| [5] | Rose, M., Klyne, G. and D. Crocker, "The APEX Access Service", draft-ietf-apex-access-07 (work in progress), August 2001. |
| [6] | Kantor, B. and P. Lapsley, "Network News Transfer Protocol", RFC 977, Feb 1986. |
| [7] | Rose, M., Klyne, G. and D. Crocker, "The APEX Presence Service", draft-ietf-apex-presence-05 (work in progress), July 2001. |
| [8] | World Wide Web Consortium, "Platform For Internet Content Selection (PICS)", W3C PICS, October 2001. |
| [9] | Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. |
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| Michael F. Schwartz | |
| NetTopBox, Inc. | |
| EMail: | schwartz@CodeOnTheRoad.com |
| URI: | http://www.CodeOnTheRoad.com |
| Marshall T. Rose | |
| Dover Beach Consulting, Inc. | |
| POB 255268 | |
| Sacramento, CA 95865-5268 | |
| US | |
| Phone: | +1 916 483 8878 |
| EMail: | mrose@dbc.mtview.ca.us |
| K. Carlberg | |
| University College London | |
| EMail: | K.Carlberg@cs.ucl.ac.uk |
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The IANA makes the registrations specified in Registration: The dataHopping Option.
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The authors gratefully acknowledge the contributions of: Jon Crowcroft, Eric Dixon, Huston Franklin, Carl Malamud, and Bob Wyman.
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