Serial Point-to-Point Encapsulation Explained

Posted April 20, 2006 by aaronm in Cisco router

This is an explanation of serial connection encapsulation (HDLC / PPP) and suggestions on it’s use.

There are a couple of different encapsulation methods for PtP connections. Making sure you choose the correct one for your network can be a daunting task. Hopefully, this article will provide you with some information to make your choice.

1. HDLC is the primary (and default method on Cisco devices) for encapsulation on synchronous serial links. There are two types of HDLC: Standard and Cisco. Standard HDLC only supports single-protocol environments, where Cisco HDLC can support multiple environments.

2. HDLC works best for connection between two Cisco devices where you control the link. It doesn’t offer much in the way of security, but is really easy to use. Great for connections between routers in the office or leased lines through the Net.

3. PPP uses NCP (Network Control Program) to encapsulate multiple protocols (TCP/IP, Novell, IPX). PPP also uses LCP (Link Control Protocol) to establish and maintain the link. PPP can be configured to provide different features, such as Authentication, Compression, Multilink and Error Detection.

4. PPP is a more robust encapsulation method, providing some security (CHAP is the best way to go), error detection and the ability to load balance over multiple links. It is more difficult to setup and the debug options can be a pain to sort through. I would use this protocol to load balance or across unsecured WAN connections.

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