Re: [MMUSIC] RTSP: Connectionless vs. connection-based

[Magnus Westerlund <magnus.westerlund@era.ericsson.se>]

Hi Venkat,

Thanks for the TCP keep alive information. As I have written in my 
suggested specification text a connection seeing no traffic for a RTSP 
timeout period may be closed by the server. However I would strongly 
recommend that servers would use a bigger timeout. As long as the 
resource situation for the server is not severe there exist no reason 
for the server to timeout a connection.  There exist two good reasons 
for keeping the connections alive, first the server to client requests 
can be used, secondly any request goes faster as it save the 1.5 RTT it 
takes to set up a TCP connection.

I don't think we need special keep alive traffic for the connection as 
the RTSP methods can be used. That also has the advantage of keeping 
also the RTSP session alive.

Regards

Magnus

Venkat N wrote:

> Hi Magnus ,
>
> There are two things we could consider here :
>
> 1.
> I presume that most  application protocols like ftp  implement
> timeouts  in such a way that a crossing of a particular time-period
> would imply  closing the connection (i.e if nothing comes from the client
> then it is as good as connection closed ).
>
> 2. If the  connnection has to be maintained  for a long time period then
>    there arises a possibility of using SO_KEEPALIVE .
>    On linux  systems this is present in the file 
> proc/sys/net/ipv4/tcp_keepalive_time
>    and defaults to  7200 secs .
>   This seems too big a value  and would affect all TCP connections 
> with the
>    option set.
>  
>
> Another possibility could be a mechanism running btn client
> and server for maintaining the connections.The drawback
> with this approach is that it may not be applicable to
> all clients as the protocol or mechanism is only between
> a particular client and server .
>
> It looks to me that keeping the connection open for sending
> a subsequent "SETUP" request is definitely an advantage
> but we also need to consider the polling done by the server
> on all the connected filedescriptors. If there are 100 connections
> to a server and 90 of them are idle for a long time then this
> would amount to clogging the system resources.
>
> So deciding on the timeout is still a question and my  view is that 
> the connection
> need not remain open if there is no transmission of data .
>  
>
>-- 
> Regards,
>-Venkat
>
>Visit http://cdn.hcltech.com/
>
>  


-- 

Magnus Westerlund 

Multimedia Technologies, Ericsson Research ERA/TVA/A
----------------------------------------------------------------------
Ericsson Radio Systems AB  | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: magnus.westerlund@era.ericsson.se




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