About time-to-live values
A multicast stream is distributed over a specific number of routers in a network, which is determined by the time-to-live (TTL) value. The time-to-live value decreases every time the content passes through a router. When the value reaches zero, the multicast stream travels no further. The WMS Multicast Data Writer plug-in has the following preset time-to-live values based on the type of distribution:
- 1 : Local network
- 32 : Intranet
- 64 : Internet, intra-continent
- 128 : Internet, inter-continent
- 255 : Maximum-allowed value
You may also specify any whole number between 1 and 255 to meet the needs of your multicast.
If you use an IPv6 multicast address, the time-to-live value is included in the first field of the address. For example, the first field in the address FF01:0000:0000:0000:0000:0000:0000:0000 is FF01, which indicates the address is locally scoped, meaning that the content is restricted to the local computer and the time-to-live value is set to 1. The following list shows the standard first field values and their corresponding scopes:
- FF01 : local node or computer
- FF02 : local area network (LAN)
- FF05 : local site
- FF08 : organization
- FF0E : Internet
Notes
- IP addresses in the range 239.*.* are administratively scoped, which means that TTL values do not have a special meaning. For example, the value 32 does not limit the stream to an intranet, and the value 64 does not limit the stream to the intra-continent Internet. The TTL assignment should be used to limit addresses in the range 239.192.000.000 through 239.255.255.255 to a single organization, and addresses from 239.255.000.000 through 239.255.255.255 to a single site.
- Multicast streaming and the WMS Multicast Data Writer plug-in are available only if Windows Media Services 9 Series is running on the following editions of the operating system: Windows Server 2003, Enterprise Edition and Windows Server 2003, Datacenter Edition. If you are running Windows Server 2003, Standard Edition, these features are not supported.
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