DDS and XMPP

DDS vs. XMPP

Angelo Corsaro Gerardo Pardo-Castellote
OMG DDS Co-Chair OMG DDS Co-Chair
PrismTech RTI
angelo.corsaro@prismtech.com gerardo@rti.com

1

Agenda

- XMPP Intro
- Some XMPP Extension
- XMPP vs DDS
- Concluding Remarks

OMG DDS SIG

XMPP History

XMPP = eXtensible Messaging and Presence Protocol

- 1999: Jabber starts as an Open Source project
- 2001: Jabber Software Foundation (JSF) is established
- 2002: XMPP Working Group started at IETF
- 2004: XMPP RFCs (3920-3923)
- 2006: JSF becomes the XMPP Standards Foundation

OMG DDS SIG

Core XMPP Features

- XMPP started as a standard for messaging and
presence. Today it is more than simply messaging
and presence, providing:
 Channel encryption and authentication
 Presence and Contact Lists
 One-to-one and Multi-Party Messaing
 Alerts and Notifications (XMPP Pub/Sub extension)
 Peer-to-Peer Media Sessions (Jingle)
 Data Forms and Remote Command

OMG DDS SIG

XMPP Architecture
- Client/Server
- Network of Decentralized Servers
- (Authenticated) Long Lived Connection from Client to Servers

Server Server
jabber.org mac.com

<message to=‘giorgia@jabber.org’>
<body> Have you seen my new
stratocaster?
</body>
</message>

Carmen Giorgia
carmen@jabber.org OMG DDS SIG giorgia@mac.com

Addressing

- User are addressed by Jabber ID (JID)
 es. carmen@jabber.com

- Resource can be addressed via full JID
 es. carme@jabber.com/concerts

OMG DDS SIG

Communication Primitives

- XMPP defines three different communication
primitives--called stanzas

- XMPP Stanzas are:
 <message/>
 <presence/>
 <iq/>

OMG DDS SIG

<message/>

- A <message/> stanza contains:
 From, To
 Type
 Subject + Body (Payload)

<message from=‘carmen@jabber.com
to=‘giorgia@jabber.org’>
<subject>Got a new Strato!</subject>
<body> Have you seen my new
stratocaster?
</body>
</message>

OMG DDS SIG

<presence/>

- The <presence/> stanza is used to advertise
presence and contains:
 Status
 Status Message

<presence from=‘carmen@jabber.com>
<show>xa</show>
<status>C9sus</status>
</presence>

OMG DDS SIG

<iq/>

- The <iq/> stanza is used to perform Request/
Response interactions (similar to HTTP GET, POST,
PUT)
<iq type=”get”>
<query xmlns=”jabber:iq:roster”/>
</iq>

<iq type=”result”>
<query xmlns=”jabber:iq:roster”>
<item jid=”carmen@jabber.org”/>
<item jid=”mario@jabber.org”/>
<item jid=”franco@jabber.org/>
</query>
</iq>
OMG DDS SIG

Pub/Sub Extension

- XMPP has been extended with basic Pub/Sub
capabilities

- <iq/> stanzas are used to manage subscriptions,
as well as to do pub/sub

OMG DDS SIG

Pub/Sub Extension - Subscription

<iq from=”carmen@jabber.org”
id=”cc7409”
to=”notify.jabber.org”
type=”set”>

<pubsub xmlns=”http://jabber.org/protocol/pubsub”>
<subscribe node=”musicisti-ct”
jid=”carmen@jabber.org”/>
</iq>

OMG DDS SIG

Pub/Sub in XMPP
musicisti-ct {
carmen@jabber.org
Mario
giorgia@mac.com Server
mario@xmpp.org mario@xmpp.org
} xmpp.org

Server Server
jabber.org mac.com

Carmen Giorgia
carmen@jabber.org giorgia@mac.com
OMG DDS SIG

Pub/Sub in XMPP
musicisti-ct {
carmen@jabber.org
Mario
} xmpp.org

Server Server
jabber.org mac.com

<iq
from=”carme@jabber.org”
to=notify.jabber.org”>
...
</iq>

Carmen Giorgia
OMG DDS SIG

Pub/Sub in XMPP
musicisti-ct {
carmen@jabber.org
Mario
giorgia@mac.com
<iq Server
mario@xmpp.orgfrom=”carme@jabber.org” mario@xmpp.org
to=notify.jabber.org”> xmpp.org
} ...
</iq>

Server Server
jabber.org mac.com
<iq
...
</iq>

Carmen Giorgia
OMG DDS SIG

Pub/Sub in XMPP <iq
...
</iq>
musicisti-ct {
carmen@jabber.org
Mario
} xmpp.org

Server Server
jabber.org mac.com

<iq
...
</iq>

Carmen Giorgia
OMG DDS SIG

Jingle Extension

- XMPP is not designed for distributing data with
real-time constraints

- XMPP Jingle is used to set-up direct connections
between points for streaming
 Voice
 Audio
 Video
 ...

- After negotiating a connection via XMPP,
communication goes through other protocols, e.g.,
RTP, etc.
OMG DDS SIG

What is Standardized?
- DDS - XMPP
 API Standard
 Wire Protocol Standard  Wire Protocol Standard

Application
Application
Object/Relational Mapping

Data Local Reconstruction Layer (DLRL)

DDS v1.2
Content
Ownership Durability
Subscription

Minimum Proﬁle
API (?)
Data Centric Publish/Subscribe (DCPS)
DDSI v2.1

RFC-3920/9
eXtensible Messaging and
Real-Time Publish/Subscribe Protocol Presence Protocol

DDS Interoperability Wire Protocol Wire Protocol

UDP/IP TCP

OMG DDS SIG

Architecture
- DDS - XMPP
 Fully Distributed  Store and Forward
 Topic-Based Pub/Sub  Client/Server
 QoS Enabled  Pub/Sub as a protocol extension
 Data Centric (keys, queries, etc.)  “Source Addressing”-based
discovery
 Dynamic Discovery

DDS XMPP
Subscriber
Publisher
Server Server
B

m
jabber.org mac.com
A F

Subscriber
Publisher J
D C

K
E

Publisher
Client Client
Subscriber

OMG DDS SIG

Type/Message Encoding

- DDS - XMPP
 Efficient binary encoding  XML encoding for both data
for both data-payload payload and protocol
and protocol messages messages
 Strongly Typed Topic  Just one message type, an
Types XML message
 Polymorphic Type
 Type extensibility/  Type extensibility/evolvability
evolvability supported by by leveraging XML
upcoming xTopics RFP

 Note: Multiple encoding
supported via xTopics

OMG DDS SIG

Performance

- DDS - XMPP
 Targeting high performance  Targeting interactive systems
systems  Discovery traffic often shown
 Very low latencies to introduce non-negligible
 Very high throughputs load
 Real-Time determinism

OMG DDS SIG

Concluding Remarks

- DDS and XMPP target different application domains
- DDS is able to address very sophisticated data
distribution needs, where complex QoS need to be
satisfied

- XMPP is targeting interactive web applications
- DDS provides complete transparency w.r.t changes
in the infrastructure

- Due to its “source-addressing”-based discovery
XMPP might propagate back to the application
changes into the infrastructure

OMG DDS SIG

DDS and XMPP

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