27 May
2011
27 May
'11
11:50 a.m.
2011/5/27 Daniel-Constantin Mierla <miconda(a)gmail.com>om>:
Looking at HTTP, when they needed file upload, they
added put/delete -- they
stayed in the same protocol whenever possible. In this ways the
infrastructure nodes remain the same, only higher-level applications have to
be updated. When they needed asynchronous stuff (e.g., ajax) they found the
solution there, not a new spec. In IETF and SIP WGs is different, like a
race for new protocols, not re-use of existing ones. Web does now more
real-time communication methods better than SIP, because IETF hasn't decided
the infrastructure protocol for SIP-related networks. Defining new request
method types or headers is not a change of the protocol. This is one of the
powerful tools of SIP, IETF seemed to forget that.
Just a comment: Realtime communications in HTTP is, today, a hack as
it requires long polling or ugly solutions as Comet (the HTTP 200 body
never ends so the server can send "realtime" data over the same 200
response body).
Now IETF is defining WebSocket protocol, which is a bidirectional TCP
stream between a browser (WebSocket client mainly implemented in
JavaScript) and a server. In this way we get _real_ realtime
communication. All the world is waiting for this to become a standard
for long time, so private solutions as Flash are not needed anymore in
order to implement an ugly chat in a web page.
But WebSocket is a _new_ protocol (even it is uses HTTP
request/response for websocket stream establishment). If fact it's the
same concept as MSRP but it _can_reuse por 80. Note however that HTTP
communications are not end-to-end since a client (webbrowser) just
talks to a server, there is no user-to-user communication through HTTP
proxies.
Cheers.
--
Iñaki Baz Castillo
<ibc(a)aliax.net>