[vlc] Re: vlm experiences

[Marian Durkovic]

On Fri, Dec 23, 2005 at 08:59:40AM +0100, R?mi Denis-Courmont wrote:
> Le Vendredi 23 D?cembre 2005 08:39, Marian Durkovic a ?crit :
> > Well, not necessarily. A decent OS is expected to send back ICMP
> > PORT_UNREACHABLE message if it receives packet for which no
> > application is listening. This is how e.g. traceroute works.
> 
> Yes and no. Most OSes will send an ICMP port unreachable error if the 
> application is closed, but not if there are behind a firewall (most of 
> which drop port unreachable to circumvent UDP port scanning), or if the 
> whole system stopped/got unplugged, in which case we might get an ICMP 
> destination unreachable error instead.

Sure, it's not 100 % safe, but might still work in LAN environment or
with properly implemented firewalls (ICMP blocking is heavily flawed practise
since ICMP is definitely a required protocol and most of the attacks/worms 
use well-known ports anyway). I assume this could only be used together
with RTSP (i.e. for on-demand sessions only).

If RTCP would be available, we could also cancel streams if no RTCP report
has been seen for a defined timeout - this is how e.g. VoIP gateways work.


	With kind regards,

		M.

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----   Marian Durkovic                       network  manager         ----
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