GENA Framework

1
GENA Framework

• Generalized Event Notification Architecture over
  HTTP
• Josh Cohen ltjoshco_at_microsoft.comgt
• http//egg.microsoft.com/gena/

2
Introduction

• Design Goals
• Architecture Layout
• Protocol Overview
• HTCPCP
• An Example Schema Subtype

3
Design Goals

• Internet scale
• Generalized Event Notification
• Leverage XML Extensibility
• Leverage existing infrastructure
• HTTP Proxy Servers and Firewalls
• Use HTTP Object Model and Functionality
• Fit into HTTP extension framework
• Strong Security
• Lightweight / High Performance

4
Scenarios for Base Protocol

• Simple, Lightweight Subscriptions
• Minimum requirements (HTTP only)
• Asynchronous event delivery
• Synchronous (Polled) delivery
• Lightweight UDP delivery
• Variable use of infrastructure intelligence
• Events can carry entity bodies or resource data

5
Architecture Layout

• GENA Base Protocol
• Layer model diagram
• GENA Extension Schemas
• GENA Fan-out Aggregation Routing Protocol
• Base protocol provides an easily implemented
  functionality set but allows clear and easy
  extensibility for complex applications.

6
Architecture Overview
7
Solutions

• Security is via TLS/SSL and Digest Auth
• Pattern / Search View subscriptions via DASL
• Batching notifications via XML or MIME
• UDP Notifications can provoke secure Polling.
• UDP Notifications can be Multicast
• Extensible schemas with XML
• Integration with DAV.

8
Protocol Overview

• New Verbs
• SUBSCRIBE
• UNSUBSCRIBE
• POLL
• NOTIFY

• New Headers
• Subscription-ID
• Notification-Type
• Delivery-Control
• Call-Back

9
Protocol Messages
10
Subscribing to a resource
SUBSCRIBE http//server/resource HTTP/1.1 Man
http//www.iana.org/http/gena Subscription-Type
update Call-Back http//mypc8000/listener
mailto joshco_at_microsoft.com Delivery-Control
poll-interval60 HTTP/1.1 200
Ok Extended-Response 20041 commentSubscrib
ed Subscription-ID ABADCAFE Call-Back
http//mypc8000/listener mailto
joshco_at_microsoft.com
11
Event Notification
NOFITY http//mypc8000/listener HTTP/1.1 Man
http//www.iana.org/http/gena Subscription-Type
update Subscription-ID ABADCAFE HTTP/1.1 200
Ok Extended-Response 20042 commentNotifica
tion Acknowledged
12
Polling a Subscription
POLL http//server/resource HTTP/1.1 Man
http//www.iana.org/http/gena Subscription-Type
update Subscription-ID ABADCAFE Delivery-Control
poll-interval60 batch-modemultipart/related
HTTP/1.1 200 Ok Extended-Response 20043
commentEvents Pending Content-Type
multipart/related Delivery-Control
poll-interval60 batch-modemultipart/related
13
Building upon GENA

• An application specifies an XML schema
• Register a schema subtype identifier
• plug in to notification subtype
• Application specific schema is cleanly layered on
  top of GENA messages.
• Application schemas exist as message bodies or
  sub-bodies.

14
Existing Infrastructure

• Proxy Servers / Firewalls
• Administrators can effectively filter GENA
  message by using any of
• HTTP Extension ID (Mandatory)
• HTTP Method
• Resource URI / Call-back URI
• When policy allows, existing proxies/firewalls
  can already deal with GENA/HTTP messages
• Mail Servers
• mailto callbacks end up in mailbox
• Simple filters (procmail, exchange) can process
  incoming event notifications

15
Intelligent Infrastructure

• GENA aware Proxy Servers
• Fan-Out and Aggregation of Subscriptions
• Subscriptions and Event Notifications become
  Hop-by-Hop
• Allows multi-transport delivery. Long haul
  SMTP, medium haul TCP/HTTP and short haul/LAN
  UDP/HTTP over multicast
• GENA Aware Message Bus
• Mail Server, Proxy, etc
• Allows extended queuing of events

16
Work in Progress

• Proxy routing with Fan-out / Aggregation
• Message encryption and authentication
• Collaborating with SIP Authors
• DAV Property Notification
• Defining a subtype schema for PROPCHANGE
• DASL based search result change notify

17
Example Application
18
HTCPCP Schema

• HyperText Coffee Pot Control Protocol
• Schema ID http//www.iana.org/gena/htcpcp

lthtcpcpgt ltcoffeeTypegtDecaflt/coffeeTypegt
ltcoffeeTypegtCaffeinelt/coffeeTypegt
ltflavorgtregularlt/flavorgt ltflavorgtFrench
Vanillalt/flavorgt ltstatusgtidlelt/statusgt
ltstatusgtbrewinglt/statusgt ltstatusgtreadylt/statusgt lt
/htcpcpgt
19
HTCPCP Subscription

• Start a subscription for an event which indicates
  readiness of regular french vanilla coffee

SUBSCRIBE http//masinter/pot1 HTTP/1.1 Notificati
on-Type update subtypehttp//www.iana.org/gen
a/htcpcp Call-Back http//sleepy/help
mailtosleepy_at_microsoft.com Content-Type
text/xml lt? XML version1.0gt ltHTCPCPgt
ltStatusgtreadylt/statusgt ltflavorgtFrench-Vanillalt/fl
avorgt lttypegtcaffeinelt/typegt ltHTCPCPgt
20
RVP is a GENA-based protocol for Instant Messaging

• Extends GENA based on DAV functionality
• Leverages DAV property model for rich
  notification functionality
• Uses DAV MKCOL, DELETE, PROPFIND, PROPPATCH
  methods
• Implemented by Microsoft for the Exchange Instant
  Messaging Server
• Distributed notifications and status information
  between users, distribution lists, and generic
  resources, across the Internet
• Strong security features, e.g. SSL
• Microsoft is working with ISPs,
  telecommunications vendors to design
  interoperable notifications systems based on RVP

21
Conclusion

• GENA is being implemented by Microsoft Products
• Our wish is to collaborate to agree on a
  standard. GENA or other, we will comply.
• Interested in GENA? Join us.
• Majordomo_at_egg.microsoft.com
• Subscribe gena
• http//egg.microsoft.com/gena/