basic multicast--Interactive intra-domain multicast. Supports multicast applications within an enterprise campus. Also provides
an additional integrity in the network with the inclusion of a reliable multicast transport, PGM.
bidir PIM--Bidirectional PIM is an extension to the PIM suite of protocols that implements shared sparse trees with bidirectional
flow of data. In contrast to PIM-SM, bidir-PIM avoids keeping source specific state in router and thus allows trees to scale
to an arbitrary number of sources.
broadcast--One-to-all transmission where the source sends one copy of the message to all nodes, whether they wish to receive
it or not.
Cisco Group Management Protocol (CGMP)--Cisco-developed protocol that allows Layer 2 switches to leverage IGMP information
on Cisco routers to make Layer 2 forwarding decisions. It allows the switches to forward multicast traffic to only those ports
that are interested in the traffic.
dense mode (DM) (Internet Draft Spec)--Actively attempts to send multicast data to all potential receivers (flooding) and
relies upon their self-pruning (removal from group) to achieve desired distribution.
designated router (DR)--The router in a PIM-SM tree that instigates the Join/Prune message cascade upstream to the RP in response
to IGMP membership information it receives from IGMP hosts.
distribution tree--Multicast traffic flows from the source to the multicast group over a distribution tree that connects all
of the sources to all of the receivers in the group. This tree may be shared by all sources (a shared-tree), or a separate
distribution tree can be built for each source (a source-tree). The shared-tree may be one-way or bidirectional.
IGMP messages--IGMP messages are encapsulated in standard IP datagrams with an IP protocol number of 2 and the IP Router Alert
option (RFC 2113).
IGMP snooping--IGMP snooping requires the LAN switch to examine, or “snoop,” some Layer 3 information in the IGMP packet sent
from the host to the router. When the switch hears an IGMP report from a host for a particular multicast group, the switch
adds the host’s port number to the associated multicast table entry. When it hears an IGMP Leave Group message from a host,
it removes the host’s port from the table entry.
IGMP unidirectional link routing--Cisco’s other UDLR solution is to use IP multicast routing with IGMP, which has been enhanced
to accommodate UDLR. This solution scales very well for many satellite links.
Internet Group Management Protocol v2 (IGMP)--Used by IP routers and their immediately connected hosts to communicate multicast
group membership states.
Internet Group Management Protocol v3 (IGMP)--IGMP is the protocol used by IPv4 systems to report their IP multicast group
memberships to neighboring multicast routers. Version 3 of IGMP adds support for “source filtering,” that is, the ability
for a system to report interest in receiving packets only from specific source addresses, or from all but specific source
addresses, sent to a particular multicast address.
multicast--A routing technique that allows IP traffic to be sent from one source or multiple sources and delivered to multiple
destinations. Instead of sending individual packets to each destination, a single packet is sent to a group of destinations
known as a multicast group, which is identified by a single IP destination group address. Multicast addressing supports the
transmission of a single IP datagram to multiple hosts.
multicast routing monitor (MRM)--A management diagnostic tool that provides network fault detection and isolation in a large
multicast routing infrastructure. It is designed to notify a network administrator of multicast routing problems in near real
Multicast Source Discovery Protocol (MSDP)--A mechanism to connect multiple PIM sparse mode (PIM-SM) domains. MSDP allows
multicast sources for a group to be known to all rendezvous point(s) (RPs) in different domains. Each PIM-SM domain uses its
own RPs and need not depend on RPs in other domains. An RP runs MSDP over TCP to discover multicast sources in other domains.
MSDP is also used to announce sources sending to a group. These announcements must originate at the domain’s RP. MSDP depends
heavily on MBGP for interdomain operation.
Protocol Independent Multicast (PIM)--A multicast routing architecture defined by the IETF that enables IP multicast routing
on existing IP networks. Its key point is its independence from any underlying unicast protocol such as OSPF or BGP.
prune--Multicast routing terminology indicating that the multicast-enabled router has sent the appropriate multicast messages
to remove itself from the multicast tree for a particular multicast group. It will stop receiving the multicast data addressed
to that group and, therefore, cannot deliver the data to any connected hosts until it rejoins the group.
query--IGMP messages originating from the router(s) to elicit multicast group membership information from its connected hosts.
rendezvous point (RP)--The multicast router that is the root of the PIM-SM shared multicast distribution tree.
report--IGMP messages originating from the hosts that are joining, maintaining, or leaving their membership in a multicast
source tree--A multicast distribution path that directly connects the source’s and receivers’ designated router (or the rendezvous
point) to obtain the shortest path through the network. Results in most efficient routing of data between source and receivers,
but may result in unnecessary data duplication throughout the network if built by anything other than the RP.
sparse mode (SM) (RFC 2362)--Relies upon an explicitly joining method before attempting to send multicast data to receivers
of a multicast group.
UDLR tunnel--Uses a back channel (another link) so the routing protocols believe the one-way link is bidirectional. The back
channel itself is a special, unidirectional, generic route encapsulation (GRE) tunnel through which control traffic flows
in the opposite direction of the user data flow. This feature allows IP and its associated unicast and multicast routing protocols
to believe the unidirectional link is logically bidirectional. This solution accommodates all IP unicast and multicast routing
protocols without changing them. However, it does not scale and no more than 20 tunnels should feed into the upstream router.
The purpose of the unidirectional GRE tunnel is to move control packets from a downstream node to an upstream node.
Unicast--Point-to-point transmission requiring the source to send an individual copy of a message to each requester.
unidirectional Link Routing Protocol (UDLR)--A routing protocol that provides a way to forward multicast packets over a physical
unidirectional interface (such as a satellite link of high bandwidth) to stub networks that have a back channel.
URL rendezvous directory (URD)--URD is a multicast-lite solution that directly provides the network with information about
the specific source of a content stream. It enables the network to quickly establish the most direct distribution path from
the source to the receiver, thus significantly reducing the time and effort required in receiving the streaming media. URD
allows an application to identify the source of the content stream through a web page link or web directly. When that information
is sent back to the application it is then conveyed back to the network using URD.
In this feature, a URD-capable web page provides information about the source, the group, and the application (via media-type)
on a web page. An interested host will click on the web page pulling across the information in an HTTP transaction. The last-hop
router to receiver would intercept this transaction and send it to a special port allocated by IANA. The last-hop router is
also URD capable and uses the information to initiate the PIM source, group (S,G) join on behalf of the host.