[zeromq-dev] why PGM is not a complete multicast protocol?

[Noh, Jangho]

Hello,

I have questions about PGM.

Question#1.
According to Juniper Networks, PGM is not a complete multicast protocol. Why is that?
How PGM makes distribution path???

PGM adds reliability to multicast traffic streams. It is not a complete multicast protocol like the Distance Vector Routing Multicast Protocol (DVMRP) or Protocol Independent Multicast (PIM). Adding PGM to a router does not enable the router to perform multicast functions. Instead, a PGM router with multicast capabilities and a preconfigured multicast protocol such as PIM can offer more reliable multicast services to PGM sources and receivers. PGM is not an alternative to multicast routing protocols, but an enhancement of the multicast capabilities already present and configured on the router.
http://www.juniper.net/documentation/en_US/junos13.2/topics/topic-map/mcast-pgm.html

Question#2.
How PGM receivers handle out of order packets?? (related to sliding window)
Suppose a PGM receiver expects to get packet#1 but it received packet#3. And later on, the receiver got packet#1 and packet#2.
Is there any specified document for this scenario?


Any comments are welcome.
Appreciate.

Sincerely,
Jangho Noh

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