PPP and Multilink PPP – CompTIA Network+ N10-006 – 1.4

PPP has been around for a long time, but we continue to expand its capabilities. In this video, you’ll learn how to use Multilink PPP to extend the capabilities of PPP and scale the available bandwidth available over PPP networks.

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In an earlier video, we talked about PPP. Let’s quickly review how PPP works. That stands for point-to-point protocol. And it’s a way to create a connection between two devices. It’s a layer 2 protocol. And you can really put anything inside of it. So we could communicate using IP or any number of protocols and simply encapsulate them inside of a PPP frame.

This works almost anywhere. You’ll see PPP in use on dial-up connections, wide area network links, serial lines. Things like mobile phones and DSL uses PPP. This gives you a lot of functionality down at that layer, because you can set up authentication.

You’ve got compression mechanisms built into PPP. Error detection is built into the protocol as well. And you can do an interesting capability called multilink. Multilink PPP is used when you need more than just the bandwidth that a single link might give you. And by adding additional links to a PPP connection, you can increase the amount of bandwidth and use all of those at the same time for a single flow of traffic going across.

This allows you to scale up and get higher bandwidths than what you would get by using just a single link in a single connection. But you have to keep in mind that every single link that you increase will need of course separate lines themselves.

You will need separate modems or connections on each side for the multilink. And generally those have to be tied together with something that can see across all of those simultaneously, so that it can provide the multilink PPP functionality. So you’ll need additional hardware and additional network links. And that does, of course, increase the cost of the communication over those connections.

Whenever you’re working with a technology that has multiple links that are going from one place to the other, one of the challenges you have is keeping everything in the right order. When you send information through these multiple links, sometimes the frames will come out out of order on the other side. And in networking, of course, everything needs to be received in the exact same order that it was set.

With multilink PPP, a numbering system is included when the data is sent over the link. And on the other side, as the data is being put back together, the multilink PPP connection examines that number and determines if anything might be out of order. And if it is it switches things around, so all of the data that’s received is in the exact same order as when it was sent.