waka
© 2012 Roy T. Fielding
The Waka Protocol
Roy T. Fielding, Ph.D
Principal Scientist, Adobe Systems
Director, The Apache Software Foundation
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DRAFT
© 2012 Roy T. Fielding The Waka Protocol
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Wak a
A new protocol designed to match the efficiency of
well-designed Web Applications
Why “waka”?
Mäori word (pronounced “wah-kah”) for the outrigger
canoes used to travel safely on the Pacific Ocean,
across hundreds of islands, to Aotearoa (New Zealand)
Also, one of the few four-letter words suitable for a
protocol name
Deployable within an HTTP connection
via the HTTP/1.1 Upgrade header field
defined mapping to HTTP/1.1 for proxies
© 2012 Roy T. Fielding The Waka Protocol
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HTTP
The role of HTTP in Web Architecture
Extend uniform interface across the net
Minimize user-perceived latency
Enable layered processing
Enable caching
Enable extension and evolution
Already survived two decades of evolution
1991-93: HTTP/0.9 [Berners-Lee]
1993-97: HTTP/1.0 [RFC 1945]
1996-now: HTTP/1.1 [RFC 2068/2616/HTTPbis]
© 2012 Roy T. Fielding The Waka Protocol
HTTP Syntax
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GET /Test/hello.html HTTP/1.1\r\n
Host: kiwi.ics.uci.edu:8080\r\n
Accept: text/html, text/*, */*\r\n
User-Agent: GET/7 libwww-perl/5.40\r\n
\r\n
HTTP/1.1 200 OK\r\n
Date: Thu, 09 Mar 2000 15:40:09 GMT\r\n
Server: Apache/1.3.12\r\n
Content-Type: text/html\r\n
Content-Language: en\r\n
Transfer-Encoding: chunked\r\n
Etag: “a797cd-465af”\r\n
Cache-control: max-age=3600\r\n
Vary: Accept-Language\r\n
\r\n
4090\r\n
<HTML><HEAD>
…
typical headers
325-400B +
cookies =
1079 Bytes
typical headers
300-400B + set-
cookies =
3487 Bytes
© 2012 Roy T. Fielding The Waka Protocol
Issues: Wasted Syntax
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GET /Test/hello.html HTTP/1.1\r\n
Host: kiwi.ics.uci.edu:8080\r\n
Accept: text/html, text/*, */*\r\n
User-Agent: GET/7 libwww-perl/5.40\r\n
\r\n
HTTP/1.1 200 OK\r\n
Date: Thu, 09 Mar 2000 15:40:09 GMT\r\n
Server: Apache/1.3.12\r\n
Content-Type: text/html\r\n
Content-Language: en\r\n
Transfer-Encoding: chunked\r\n
Etag: “a797cd-465af”\r\n
Cache-control: max-age=3600\r\n
Vary: Accept-Language\r\n
\r\n
4090\r\n
<HTML><HEAD>
…
content
negotiation is a
waste of bits
Dates need 8
bytes max
Useless product
advertising
Header names
need 1-2 bytes
Mostly impacts low-power
and bandwidth-limited devices
© 2012 Roy T. Fielding The Waka Protocol
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GET /Test/hello.html HTTP/1.1\r\n
Host: kiwi.ics.uci.edu:8080\r\n
Accept: text/html, text/*, */*\r\n
User-Agent: GET/7 libwww-perl/5.40\r\n
\r\n
HTTP/1.1 200 OK\r\n
Date: Thu, 09 Mar 2000 15:40:09 GMT\r\n
Server: Apache/1.3.12\r\n
Content-Type: text/html\r\n
Content-Language: en\r\n
Transfer-Encoding: chunked\r\n
Etag: “a797cd-465af”\r\n
Cache-control: max-age=3600\r\n
Vary: Accept-Language\r\n
\r\n
4090\r\n
<HTML><HEAD>
…
Control Data
Message Metadata
Representation
Metadata
Resource/SR
Metadata
Data
Extensions cannot indicate scope or mandate
Messages associated by order sent/received
© 2012 Roy T. Fielding The Waka Protocol
Issues: Head-of-Line Blocking
Message Ordering
Pipelining depends on pairing requests to responses
A slow response delays all later requests
Servers can’t send unsolicited event notifications
Envelope Ordering
Control data must be sent first
server must indicate success before it is actually successful
Metadata must be sent before Data
low-priority metadata is excluded for performance reasons
data cannot be sent until all filters supply metadata
dynamically generated metadata is lost
Data must be entirely delivered
no signal for abnormal termination
limited support for small-memory devices (Range requests)
Control data cannot be updated to reflect events
what if the sender encounters a time-out condition?
what if an intermediary is caught in the middle of a bad stream?
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© 2012 Roy T. Fielding The Waka Protocol
Wak a
A replacement for HTTP (under development)
Token-based, length-delimited syntax*
considering changing this to a derivative of msgpack
Self-descriptive messages
Interleaved message (meta)data packets:
Up to 64 channels per connection
Up to 63 payload streams per message
Complete transport independence
TCP, UDP, SCTP, TLS, multicast, ...
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© 2012 Roy T. Fielding The Waka Protocol
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New Request Semantics
Multiple request targets (GET many subrequests)
Request control data
request/transaction identifier
relative priority (high, low, HiLo)
explicit indication of context (main, embed, js, test)
Methods
RENDER for display/print/speak this representation
MONITOR for notify me when resource state changes
Authoring methods (DAV simplified)
elimination of non-resource identifiers
reintroduction of PATCH
© 2012 Roy T. Fielding The Waka Protocol
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New Response Semantics
Self-descriptive binding to the request
Echo of request id, method, target URI
Cache key explicitly described
Caches no longer need to save request fields
Caches don’t have to guess about Vary info
Enables asynchronous transport
Response indicates authoritative or not
Semantics formerly in status code
Unsolicited Responses
Cache invalidation messages
Multicast event notices
© 2012 Roy T. Fielding The Waka Protocol
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Wak a Synta x
Uniform syntax
Regardless of message type, direction
Padding allowed for 32/64bit alignment
Self-descriptive
Explicit typing for message structure, fields
Indication of mandate and scope of fields
Association of metadata (control, resource, rep.)
Premature termination of request or response
Efficient and Extensible
Tokens for all standard elements
A URI reference can be used in place of any token
Macros (client-defined syntax short-hand)*
Interleaved data and metadata delivery
© 2012 Roy T. Fielding The Waka Protocol
Future Plans
Finish HTTPbis
Finish drafting Tracking Protection
Write a specification for Waka
Decide whether to submit it here.
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