What is frame relay of PPP?

There are many things worth learning about in the PPP protocol. Here we will focus on the content of PPP frame relay. First, let's take a look at the basic concepts. PPP: Point-to-Point Protocol. Huawei routers are encapsulated by default and are character-oriented control protocols. HDLC: Advanced Data Link Control Protocol. It is a bit-Oriented Control Protocol and is the default encapsulation of Cisco routers. Fram-relay: indicates the Frame relay switching network. It is an improvement of the x.25 group switching network and works in the form of a virtual circuit.

What is HDLC?

HDLC indicates the High-level Data Link Control Protocol, which is the same as the two other Wan protocols mentioned in this article, HDLC is a layer 2 protocol (refer to the OSI Network Model for more layer information ). HDLC is a simple protocol used To connect a Point-To-Point serial device. For example, you have a point-to-point lease line connecting two places in different cities. HDLC connections can have connections with the least configuration requirements. The HDLC protocol runs on the Wide Area Network in two different places. Each router will unencapsulate the HDLC data packets and forward them to the LAN or discard them.

HDLC's correction of errors is similar to Ethernet. The Cisco version of HDLCA is more private, and they specifically add a protocol type domain. Therefore, Cisco HDLC can only work on Cisco devices.

HDLC is actually a default setting on all Cisco serial interfaces. If you create a showrunning-config on a Cisco router, your serial interfaces (default) are not encapsulated because they are configured as the default HDLC, if you enter show interface serial 0/0, you will see the running HDLC protocol.

What is PPP?

You may have heard of the Point to Point Protocol (PPP) because it is applied to most dialing connections to the Internet. The PPP document describes RFC1661. PPP is based on HDLC and is very similar. They can all work well.

The leased line at the point. The difference between PPP and HDLC is as follows:

◆ The PPP protocol is not private to the Cisco Router

◆ PPP has several sub-protocols to implement its functions

◆ PPP is the same as dialing network features.

Because PPP has many dial-up network features, it has become the most popular dial-up network protocol today. The following are the dial-up network features it can provide:

◆ Connection Quality Management monitors the quality of dial-up connections and the number of errors that have occurred. If too many errors are accepted, the connection will be closed.

◆ Multiple links can accommodate multiple PPP dial-up connections and are combined with one PPP dial-up connection.

◆ PAP and CHAP support identity authentication. When you dial, these protocols will accept your account name and password to ensure that you can access the network you want to connect.

Change HDLC to PPP on a Cisco router. Run the following command: after encapsulation ppp changes the encapsulation type to PPP, enter: PPP? Available PPP options are listed. Compared with HDLC, the PPP protocol has many options.

What is frame-relay)

Frame relay is a layer 2 protocol, which is commonly used as a carrier service. For example, people would say that I have set a frame resumption circuit. Frame Relay creates a private network through the carrier network, which will generate a persistent virtual circuit (PVC). a pvc is a connection from one site to another through the carrier network. This is a configuration entry that is actually generated by the carrier on the frame relay switch.

Set a T1 or T1 part to obtain a frame relay circuit from the carrier. On this part, you set a frame relay port to match the size of your frame relay circuit. Finally, you need to set up a PVC to connect your frame relay port to another port on your network. Frame Relay has the following advantages:

A single circuit is capable of connecting to the "Frame Relay cloud" to access all other sites (as long as you have PVCs ). When the number of sites increases, you can save more and more money because you don't need so many virtual circuits to patch your network when you adopt PPP.

This improves disaster recovery because all you need to do is to set up a circuit to the frame relay cloud, so that PVC can access all remote sites.

By using PVCs, you can design your WAN based on your own ideas. This means that you can define the sites that can be directly connected to other sites. You only need to pay a small fee for PVC connection each month.

For frame relay, you should also know other related terms:

◆ LMS: Local Management Interface (LMS), which is the Management protocol for Frame Relay. LMIS is sent to communicate with the vswitch about what DLCI is available and whether the network is congested.

◆ DLCI: Data Link Connection Identifier, which is used to identify the number of each PVC in the frame relay network.

◆ CIR: the Rate of submitted Information (Committed Information Rate) indicates the amount of bandwidth consumed to ensure your receipt. In each PVC, you should have a CIR speed lower than your port speed. Of course, you can speed up your traffic to exceed the accept speed of your port, but the traffic will be marked as DE (Discard Eligible ).

◆ DE: (Discard Eligible) Discard. Traffic marked with DE can be discarded when the network is congested.

◆ FECN/BECN: forward direct congestion notification (forward explicit congestion notification)/backward direct congestion notification (backward explicit congestion notification ). These bits are set in the LMS package to notify the Frame Relay Device of network congestion!