About time-to-live values

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Applies To: Windows Server 2008, Windows Server 2008 R2

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 TTL 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 TTL 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 TTL 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 TTL 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

Note

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.