It looks like time to put up or shut up! Where can you get yourself some multicast for your network? The sense I get is that people are using it because it just works, with relatively little fuss. You do have to buy the hardware and architect your solution to scale, but the actual video administration can probably be done by a PC technician.
|Published (Last):||27 July 2007|
|PDF File Size:||7.46 Mb|
|ePub File Size:||12.13 Mb|
|Price:||Free* [*Free Regsitration Required]|
It looks like time to put up or shut up! Where can you get yourself some multicast for your network? The sense I get is that people are using it because it just works, with relatively little fuss.
You do have to buy the hardware and architect your solution to scale, but the actual video administration can probably be done by a PC technician. Unsolicited plug! For more information, see:. The following table should make sure that everyone is equally confused. The way I think of multicast is that it is like subscribing to a magazine.
Admittedly, the magazine is being shared around with others. The routers are the subscription agency, tracking whether any LAN group of readers needs a copy of a particular multicast feed, and where they are. That way, the routers can ensure that a single copy of the multicast feed is transmitted on each link, at least most of the time. This conserves bandwidth. The catch here is that multicast is like watching TV. If there is sharing, you turn on your viewer and watch the same thing as many other people.
The above picture is the state of streaming video or audio in the Internet right now. Everyone gets their own personal copy. Even for content that could potentially be shared, such as Internet radio. The users can use multicast to transmit to each other. Or the conference bridge can use multicast to reach all participants. The benefit here is that the conference bridge just sends multicast packets, then the routers deliver them. This is a lot less work than duplicating packets for each client on the conference.
But suppose. The PC then notifies the router that it is interested in receiving the multicast in question. IGMP version 1 only sends join notifications as in, joining the group of viewers. That way, if nobody cares anymore, the router can stop duplicating and transmitting copies of the multicast feed, to save bandwidth.
Periodic means every 60 seconds by default, but this is configurable. That in turn means the router has a chance to save bandwidth, sooner. IGMP version 3 allows the client to specify the sources of multicast traffic, sources that it is interested in, for each multicast group of interest. Suppose the multicast feed is hi-resolution video using a lot of bandwidth. If on full duplex, replies to the packets they send are delayed by the multicast packet flooding.
The problem there is the PC CPU then gets bombarded by multicast packets, both those it wishes to receive and others. This saps the power of the CPU. In that way, each PC will only receive the multicasts it asked for. CGMP also does some other messaging, basically the router letting the switch know which port it is connected to, and housekeeping functions such as keepalives.
It uses the chip set for the switch port to snoop on IGMP packets. This is automated in the Cisco implementation details: see the following link. GMRP is part of Whatever could they have been thinking of? The question here is: are there NIC card drivers that support this probably there are by now, RGMP is a relatively new Cisco protocol. Normally, all multicasts are forwarded to the router port. The purpose of RGMP is so the router can tell the switch which multicast groups it wishes to receive.
One way to use this might be to have multiple routers, each forwarding certain high-volume multicast groups. With RGMP, the chip set in the switch can filter which multicasts go where, instead of using the CPU in the router for this and overwhelming it, probably. Dense mode is named that because you have to be dense to run it. Just kidding! Dense mode is characterized by flooding every 3 minutes, which is rather anti-social if you have significant volumes of multicast in your network.
This feature is enabled by default as of Sparse mode works by routers sending Join messages, to start the multicast feed being sent across links. Very quickly, router-to-router Join messages cause the multicast feed to be sent across links to where it is needed. This scales well. These are other protocols for multicast, pre-dating PIM.
CBT comes from research, scales to very large scale at the price of some possibly delay in reaching the viewer. It requires OSPF as unicast routing protocol, and furthermore is generally conceded to not scale well. Multiprotocol BGP can carry routing information about several protocols. RPF checking uses the unicast routing table. When a multicast source wishes to transmit multicast, it just starts sending. It is up to the routers to do the right thing with the multicast.
The RP is the crucial router that is aware of sources and multicasts in the network. It contains links to other documents with multicast configuration samples and tips. A principal consultant with broad knowledge and experience in high-end routing and network design, as well as data centers, Pete has provided design advice and done assessments of a wide variety of networks.
Nick has over 20 years of experience in Security Operations and Security Sales. John is our CTO and the practice lead for a talented team of consultants focused on designing and delivering scalable and secure infrastructure solutions to customers across multiple industry verticals and technologies.
In that capacity, he led a team managing network architecture and services. He is an expert in working with groups to identify business needs, and align technology strategies to enable business strategies, building in agility and scalability to allow for future changes.
John is experienced in the architecture and design of highly available, secure, network infrastructure and data centers, and has worked on projects worldwide. He has worked in both the business and regulatory environments for the design and deployment of complex IT infrastructures.
Click here to request a Network Assessment! Why Multicast? Contrast the following pictures. Peter Welcher Architect, Operations Technical Advisor A principal consultant with broad knowledge and experience in high-end routing and network design, as well as data centers, Pete has provided design advice and done assessments of a wide variety of networks.
Ccip: Multicast and QOS Study Guide
Questions? Contact a Training Specialist