HTTP - Next Generation

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HTTP - Next Generation

• Mike Spreitzer
• Xerox PARC CSL
• 8 June 1998

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Problems with HTTP

• Difficulty of extending/modifying HTTP
• Emerging incompatible object systems
• HTTP used as a reliable datagram protocol
• Increased use of CGI-like Web services
• Performance

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The W3C HTTP-NG Project

• An activity of the World Wide Web Consortium
• Experimental What happens if we factor HTTP
  into distributed-object system application?
• original HTTP attempted a distributed object
  protocol
• Goals greater extensibility, simplicity,
  functionality, efficiency

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Project Structure

• Two working groups
• Web Characterization Group
• Jim Pitkow, Xerox PARC, chair
• Study Web usage and form requirements
• Protocol Design Group
• Jim Gettys, Digital, chair
• Redesign Web as a distributed object application
• Interest Group
• www.w3.org/Protocols/HTTP-NG/Group/IG/

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HTTP-NG Architecture
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Three Layer Structure

• Web API layer on top offers object-oriented
  access to the classic Web operations
• Messaging layer in middle provides
  state-of-the-art distributed object capabilities
• Modular architecture for stackable byte transport
  layers
• MUX layer addresses TCP/IP problems

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Web Application Layer

• Object-oriented network API for the HTTP 1.1
  specification
• The Classic Web Application (TCWA)
• Still under development

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Messaging Layer

• Simple marshalling rules
• Small but powerful type system
• Combines Java RMI, CORBA, DCOM
• Byte-efficient
• Uses session-adaptive compression
• Based on existing IETF standards and registries

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MUX Layer

• Multiplexing multiple streams over single TCP/IP
  connection
• Byte streams or opaque message streams
• Bi-directional over same TCP/IP connection

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Advantages of HTTP-NG

• Efficiency
• Extensibility
• Simplicity

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Efficiency

• MUX provides for state-sharing between multiple
  parallel connections
• Binary message formats reduce the amount of
  string parsing and formatting needed, and
  typically reduce bytes on wire
• Careful protocol design minimizes network round
  trips

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Extensibility

• New interfaces can be defined to add new
  applications such as WebDAV
• Backwards compatibility of interfaces allowed via
  subtyping of object types
• HTTPPEPs optional/mandatory End-to-End/Hop-by-Ho
  p headers mechanism available via property list
  groups
• Ideas on better typing too

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Extensibility (2)

• Extensibility in transport layer with transport
  stacking to transform message streams
• Extensibility in messaging layer with extension
  contexts
• Extensibility in application layer with interface
  definition, subtyping, etc.

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Simplicity

• Highly modular architecture
• Low coupling between modules
• Each module designed to be internally simple
• Predictable architecture

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Relationship with XML

• XML is important in the web
• HTTP-NG will use XML as appropriate
• Plan to develop an RDF-based IDL
• DOM is getting IDL, Java interfaceshope to add
  HTTP-NG interfaces

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Project Phase 1

• W3C Activity
• Demonstrate basic feasibility
• using existing ILU as testbed
• new MUX and messaging protocols
• robotic clients and modified Apache
• First release of drafts in early July
• Ends this summer
• road show ready for September TC mtg

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Project Phase 2

• Starting this summer
• W3C Activity continues (if approved)
• IETF involvement begins

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Come Join Us!

• http//www.w3.org/Protocols/HTTP-NG/
• W3C members can see all
• Others can join the Interest Group
• Next IETF
• August 23--28, Chicago