How does IGMPv2 solve these problems?
Using four new capabilities.
IGMPv2 allows for adjustment of many timers,
such as the query interval, query response interval,
also called the max response time, last member query interval,
and many more.
Rather than recite definitions, I'll explain these timers as we encounter them.
This doesn't solve any IGMPv1 problem directly,
but aids in optimizing performance.
The querier election solves our minor IGMPv1 issue.
The router with the lower IP address becomes the
querier on the multi-access network,
bringing standardization to the query process.
The leave group message solves the bigger IGMPv1 problem.
When a client wants to stop getting multicast,
it can use a leave group message to signal disinterest.
The group-specific query message works in tandem with the leave group
message to ensure that if one client wants to leave a group,
others on the LAN can still receive multicast if they need it.
This leave query process is by far the most important improvement,
so we will focus there.
Before diving into the new leave and group-specific query process,
let's briefly review the basic query join process.
It's very similar to IGMPv1, so I won't belabor it.
The router sends a message called a general query,
now making use of the previously 0 code to carry a maximum response timer.
This is the longest the router will wait to hear replies from the clients.
The client response with 1 IGMPv2 membership report in each
group in which it wants to receive multicast.
The max response time exists in all IGMPv2 packets for formatting consistency,
but is set to 0 outside of queries.
How does the leave process work?
It's very intuitive.
First, the client says I don't want multicast on group 239.1 .1 .1 anymore.
It sends this to 224.0 .0 .2, the all multicast routers link local group address,
and carries 239.1 .1 .1 in the message body.
The router replies with okay, is there anyone else who still wants 239.1 .1 .1?
If the answer is yes,
other clients can resend their membership reports for 239.1 .1 .1.
If not, clients simply don't reply.
After only 1 second of waiting,
the router will cut off multicast flow to the segment if there are no interested receivers.