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: 224.0.0.13 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
0-223.255.255.255 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 224.0.0.0-224.0.0.255/24 IGP application address
2, the public network address 224.0.1.0-238.255.255.255 on the public network can be routed
232.0.0.0-232.255.255.255 SSD
233.0.0.0-233.255.255.255 Glop (Request as gift multicast address)
3, the private network address 239.0.0.0-239.255.255.255 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
Leave
IGP PIM, EGP PIM
Turn on Multicast protocol
PIM mode sparse, dense
IP IGMP join-group 224.1.1.1
IGMPv3
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