Tema: Re: megaTV, wrt54gl, igmp
Autorius: TZ
Data: 2009-03-25 13:39:18
FINALLY, kai randi paaiškinimą žaliems, tai iš karto ir aišku pasidaro.
Su išoriniu WAN interface pagauni UPSTREAM, ir DOWNSTREAMINI į savo
vidinius interface'sus.
"IGMP proxy is very simple in the sense that it acts as IGMP router for
downstream interfaces and as a host on upstream interfaces. It listens
for IGMP reports coming on downstream interfaces from hosts interested
in listing to multicast traffic. It consolidates report information
coming from different hosts across different downstream interfaces and
send consolidatedreport to upstream routers.
In Office edge routers, the interfaces connected to inside machines are
typically downstream interfaces and WAN interfaces connected to ISP
routers are upstream interfaces. In case of DSLAM, WAN interfaces
towards its customers are downstream interfaces and upstream interface
is connected towards Internet.
Multicast stream providers get unique Multicast IP address for each type
of stream from IANA. This IP address is advertised. Any machines willing
to receive this stream send IGMP membership reports to routers
indicating their willingness to receive packets coming on a particular
multicast IP address. IGMP protocol is used to send membership reports.
IGMP proxy devices receives multicast stream from upstream interfaces,
it knows the downstream interfaces interested in this traffic based on
membership reports it received before. It duplicates the traffic and
send it to these downstream interfaces. It provides great advantage on
cost savings as only one copy of stream is sent on WAN link. Gateway
implementing IGMP proxy duplicates on multiple downstream interfaces."