[streaming] SAP problem

[Tomasz Szewczyk]

Rémi Denis-Courmont pisze:
> Le Monday 15 October 2007 16:26:16 Tomasz Szewczyk, vous avez écrit :
>   
>> I just tried to start multicast stream announced by SAP/SDP with VLC
>> 0.8.6c. The problem is that SAP message contains (almost) random
>> Originating Source IP address. I captured the SAP packet (with wireshark).
>>     
>
> Which address do you mean? the originating address (o=) is purely 
> informational, so while it should not be random, it should not matter either.
>
> I recall some bug whereby the source filter specification contained the 
> destination multicast address instead of the source - I thought that was 
> fixed in 0.8.6c, but you can try the development tree if not.
>
> Could you paste the faulty SDP please?
>
>   
Here is the example (output from Cisco)

Session Name: psnc-test
  Description:
  Group: 233.35.152.11, ttl: 0, Contiguous allocation: 0
  Uptime: 00:00:25, Last Heard: 00:00:00
  Announcement source: 120.1.62.0, destination: 224.2.127.254
  Created by: - 339647032040 898 IN IP4 150.254.210.89
  Phone number:
  Email:
  URL:
  Media: video 1234 RTP/AVP 33


I attached the SAP packet captured with wireshark. I think SDP contains 
correct information but take a look at SAP Originating Source value. It 
differs form IP packet source and "o=" value in SDP message. Moreover, 
the SAP originating source field changes everytime when the streaming is 
stopped and started again (Stop/Play buttons).

I think this could cause that some routers can discard the SAP message 
with wrong address. For instance the SAP is "vissible" on first-hop 
cisco router, but it doesn't appear on neighboring juniper router.

Tomek

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