What is the purpose of TTL field in IP header?
For example, TTL is a value in an Internet Protocol (IP) packet that tells a network router when the packet has been in the network too long and should be discarded. The time-to-live value instructs a network router when a packet should be discarded.
What is TTL in multicast?
The multicast time to live (net. slp. The default value of the multicast TTL is 255, which means, theoretically, that the packet routing is unrestricted. However, a TTL of 255 causes a multicast packet to penetrate the intranet to the border routers on the edge of your administrative domain.
Is there a TTL threshold for multicast traffic?
There is a need to limit how “long” multicast traffic will expand across routers. That’s what the TTL is used for. Routers have a TTL threshold assigned to each of its interfaces, and only datagrams with a TTL greater than the interface’s threshold are forwarded.
How does multicast work on a TCP / IP network?
As said before, any multicast-capable hosts join the all-hosts group at start-up , so “pinging” 224.0.0.1 returns all hosts in the network that have multicast enabled. Finally, consider that for a process to receive multicast datagrams it has to ask the kernel to join the group and bind the port those datagrams were being sent to.
Why is TTL value 1 in IGMP?
The reason that it doesn’t have to leave the LAN is that IGMP (or MLD if you use IPv6) only talks to the multicast router on the LAN. The multicast router will take care of the routing. TTL == 1 means stay on this network; it will not be forwarded by any router.
Are there different levels of support for multicast?
Hosts can be in three different levels of conformance with the Multicast specification, according to the requirements they meet. Level 0 is the “no support for IP Multicasting” level. Lots of hosts and routers in the Internet are in this state, as multicast support is not mandatory in IPv4 (it is, however, in IPv6).