On Thu, Jul 21, 2011 at 06:27:49PM +0200, Iñaki Baz Castillo wrote:
2011/7/21 David Endicott <dendicott(_at_)gmail(_dot_)com>:
DNS resolution is not a function of a transport protocol. DNS SRV has no
special association with WS. It is my opinion that this would be
additional cruft that is only marginally related to the purpose and function
of websockets. It does not address a general use case. DNS SRV applies
only to a (small?) subset of server-side implementations. It is a good
and useful mechanism, but I do not believe it should be tied tightly to
websockets, nor included as part of the core spec.
An WebSocket URI is given to a WebSocket client, and the client MUST
locate the corresponding WS server, right? and for locating the server
the client MUST follows a procedures which, for now, involve (if it's
not an IP) DNS A/AAAA resolution, right? So now imagine that the
location mechanism is a bit more powerful and also involves SRV
queries (not always).
If you think that a transport protocol (like WebSocket) must not
resolve a server destination then also remove the WS URI inspection
and resolution from the core spec, don't you agree? or just DNS A/AAA
is valid?
I don't agree with your opinion at all. Regards.
Iñaki,
I understand the point David is making. DNS is something independant of
WS and conversely. It is one way of resolving addresses, just like there
will be people using hosts files. At no place the protocol specification
dictates how a client should resolve a name to an IP address. The protocol
specifies the transport part only.
This is the same for other protocols. For instance, neither FTP nor HTTP
explain how a client is supposed to resolve a host name, still the later
explains how to parse a URI. DNS SRV is a DNS extension which only concerns
resolvers. Not all clients will be using resolvers, just a part of them.
Some others will simply forward the request to their HTTP proxy which will
apply whatever DNS resolving method they know, including possibly DNS SRV.
In practice, if there are new elements of DNS SRV that are specific to WS,
they should probably be added to the DNS SRV spec and not the WS spec.
Maybe the WS spec should mention that it addresses transport only and
not address resolving. It may recommend to follow some principles to
perform the resolving but should not specify how to do it.
Hoping it's a bit clearer,
Willy
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