Fourth day of multicast learning and sharing

 

13. multicast routing protocol-PIM (protocol-Independent Multicast Routing Protocol)

 

Multicast Routing Protocol classification-dense mode and Sparse Mode

 

Multicast branch tree

 

1. STP ---- source tree, Shortest Path Tree

 

To maintain table items (S, G), it indicates the tree closest to S)

 

It consumes a lot of memory because it needs to maintain one S and G for each source.

 

Fast data forwarding and low latency

 

2. Shared tree ---- RP tree, core tree (CBT, not described) ------- SPARSE-MODE

 

First, determine the RP, which can be manually specified or dynamically learned.

 

Maintenance (*, g). The RP tree is a shared tree formed by RP as the root.

 

When the Source sends traffic to the RP, the RP sends the traffic received by the source along the sharing tree.

 

RP to source is the source tree

 

Less memory consumption, data forwarding may be performed on sub-optimal path forwarding

 

Latency may increase.

 

Dense-mode

 

1. push mode

 

Is to send leaflets.

 

2. flood and prune

 

Send traffic to you first, and you don't want me to trim it slowly

 

Initialize flooding for all nodes and trim them later.

 

3. ip pim dense-mode Under the interface. flood is once every 3 minutes.

 

4. Use assert to view which vro to forward the data under the Multi-Channel Access link.

 

5. Suitable for small networks, because small networks usually have a large number of recipients.

 

6. For the intermediate network router, even if it is trimmed, the (S, G) Table item must be maintained.

 

7. the PIM data packet will be sent to 224.0.0.13, And the PIM V2 protocol number is 103, HELLO 30S once.

 

8. show ip pim nei, show ip mroute

 

Sparse mode

 

1. pull Mode

 

Show add model, the last hop router will pull traffic to RT only after receiving the receiver's report

 

 

PIM multicast distribution tree construction using unicast routing protocol, join/prune/graft messages

 

 

14. pim assert Mechanism

 

Two vrouters can forward multicast packets to the upstream of a Multi-Channel Access Network. At this time, we need only one vro to send data packets. At this time, the two routers will send an assert comparison to compare two things, distance and metric. This is the comparison of the route for each router to reach the source. If they are all the same, a device with a higher IP address will send messages. The winner will become DR, And the loser will send a prune message to the upstream router.

 

Priority can be configured to affect the election. ip pim dr-priority under the interface is configured.

 

Use show ip pim nei to determine DR

 

14. PIM-SPARSE

 

1. Support for source and sharing trees

 

2. Explicit pull-based model

 

3. Based on the RP concept, the sender and receiver will meet in the RP

 

4. The sender registers with the RP based on the first-hop router.

 

Add recipients to the RP-based shared tree

 

5. Suitable for large and scalable Networks

 

6. high efficiency.

 

7. Extended Mode: bidirectional mode and specified Source Multicast

 

Working principle:

 

The Multicast Source sends a multicast message to the First-hop router. The first-hop router sends a registration message (unicast) to the RP)

 

The last hop router sends (*, G) join information to the RP after receiving the request

 

The receiver and the source establish (s, g) join message, now the multicast sends along the source tree

 

The RP sends a registration stop message to the first hop router.

 

The last hop router will send a trim to the RP, And the RP will forward the trim

 

15. Why switch STP?

 

What is the network bottleneck of the shared tree RP?

 

You can set ip pim spt-threshold to see the rate of Multicast Reception. Switch if the speed is fast

 

16. IGMP

 

It runs in the receiver segment and is used by the receiver to send the multicast message to the last hop route.

 

 

 

This article is from the "Network Technology" blog