Learn the principle notes of multicast

Source: Internet
Author: User

Disadvantages of broadcasting: routed isolation, non-cross-network segments, wasted traffic, and hardware resources
OSPF Build neighbor: Unicast: Too troublesome broadcast: wasting resource multicast: IGP

Benefits of Multicast:
1, the concept of the group
2, send data reasonable use of bandwidth resources, reduce the sender's CPU resource consumption
3, do not know the address of the recipient
4. Real-time sex

UDP-based (data plane)
TCP Head 20Byte retransmission mechanism
UDP Header 8Byte
1. Fast speed
RTP real-time Transmission protocol: UDP message is unordered, through RTP to control the disorder of UDP

Multicast protocol: PIM (Protocol-Independent multicast) multicast address: Send Hello packet multicast address

Multicast Disadvantages:
1, the message is the best possible transmission (no ACK)
2. No congestion avoidance mechanism (no sliding window)
3. Disorderly transmission (using RTP correction)
4. Duplicate packages (PIM resolution)

Application Type:
One-to-many, many-to-many (video conferencing), multi-pair (monitoring)

Multicast Service model
First-hop Router: The first router to receive a multicast
Last-hop Router

IGMP: Applies to the protocol that is associated between the router and PC, whether the PC is joined to a group

0- A, B, C address:
The difference between unicast address and multicast address: Unicast address can be configured under the routing interface, unicast address can do source address and destination address, multicast address can only do destination address, multicast address can not configure subnet mask

1, reserved address IGP application address
2, the public network address on the public network can be routed SSD Glop (Request as gift multicast address)
3, the private network address can not be routed on the public network

IGMPv1, IGMPv2, IGMPv3 Internet Group Management Protocol

The basic Group member query and reporting process is defined in IGMPV1
Query Package: Router sends every 60s
Report package: PC sends, represents join a group role: 1. Act as ACK 2. Actively respond to a group. No off-group messages

IGMPv2 default (added a mechanism for group members to leave quickly on IGMPv1 basis)
Query multi-redundant when the first to send the packet than the address of Querier, the query sent a query package
Report: act as ACK and proactively tell the route I joined the group, suppressing other group members

Turn on Multicast protocol
PIM mode sparse, dense
IP IGMP join-group


Two-tier multicast address:
The IGMP snooping industry standard only splits on the switch to the three-tier address
Cisco Group Management Protocol CGMP

Multicast forwarding:
Unicast routing table only cares about how this package goes out, the multicast routing table only cares about how this package comes in.
PIM solves the problem of duplicate packets and cares which interface this package comes from

Multicast interface called RPF interface reverse path forwarding reverse path forwarding anti-ring mechanism

RPF interface Election method: An IP address that is the smallest of the ad and is smaller than the metric and has a large interface

Group-based control of load sharing, change cost, multicast static routes only for election of RPF interfaces, no multicast forwarding, multicast static routes with AD value 0

Tree-shaped structure:
source-rooted source Tree, alias: Shortest Path tree SPTs: A source tree to view multicast routing table
Pros: Shortest Path
Cons: There are multiple sources, all stored in a table, consuming resources
Dense mode (dense mode) receiver many, push

Shared trees Share Tree alias: RP:RP collection point, let the source to advertise to the RP, and then by the RP to send down
Advantages: Combined with dense mode
Spare mode (sparse mode)

Learn the principle notes of multicast

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