[Live-devel] Concerning multicast TTL of zero

[Ross Finlayson]

> For my application I need to send differently scoped multicast RTP.
> I have found that I use both the multicast address and the TTL to try different configurations.
> However, I cannot send multicast packets with a TTL of zero (meaning traffic restricted to the same host). They get sent but with a TTL of 1 (meaning traffic restricted to the same subnet, not what I want).
> I have seen the problem lies in writeSocket in GroupsockHelper: it skips the setsockopt to set the TTL if it is 0.
> Removing the condition seems to work (meaning such packets reach receivers in the same host but are not seen by other hosts in the subnet or traffic analysers), but I wonder if not setting TTL 0 is intentional and by enabling it I will be having "collaterals".
> So, should everything work as expected when enabling TTL 0?
> Would this be filed as a "bug" and be corrected in the next version?

Yes, probably.  Thanks for the note.


Ross Finlayson
Live Networks, Inc.
http://www.live555.com/

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