The Cisco IOS WAN can support many different WAN protocols that can
help you extend your LANs to other LANs at remote sites. Connecting
company sites together so information can be exchanged is imperative in
today’s economy. However, it would take a truckload of money to put in
your own cable or connections to connect all of your company’s remote
locations. Service providers allow you to lease or share connections
that they already have installed, which can save money and time.
It is important to understand the different types of WAN support provided by Cisco. Although this chapter does not cover every type of Cisco WAN support, it does cover the HDLC, PPP, Frame Relay, and ISDN protocols.
A Wide Area Network (WAN) is similar to a Local Area Network (LAN). The main difference is that a WAN operates beyond the geographic scope of a LAN. The major characteristics of a WAN are as follows:
HDLC
PPP
Frame-Relay
HDLC and ppp are point-to-point protocols. if you have two sites, let's say one in new Yourk and the other one in Washington you might get a leased line. A leased line is an example of a point-to-point link and this is where you would run HDLC or PPP.
There is not much to tell you about HDLC It's a point-to-point protocol and it's the default for cisco Routers. HDLC is a standard but running HDLC between routers from different vendors is not going to work. keep this in mind. Every vendor has a proprietary field in their HDLC implementation which is what makes it incompatible between vendores.
PPP ( point-to-point protocol ) is a protocol that I'm going to tell you more about. still have the OSI-model fresh in mind ? I told you WAN protocols operate on the physical and data link layeer I just told you about the physical layer and its serial cables, now it's time for the data link layer.
PPP operates ont the data link layer ( layer 2 ) but as you can see the data link layer has been split into two pieces:
NCP: Network control protocol
LCP: Link control protocol
NCP will make sure you can run different protocols over our PPP link like IP,IPv6 but also
CDP (Cisco Discovery Protocol ) and older protocols like IPX or appletalk.
If you want to use Authentication for PPP you have two options:
PAP (Password Authentication Protocols ) this is plaintext it will send the username and passoword over the PPP link and the router on the other side will check it.
CHAP (challenge Authentication Protocol): Instead of sending the password in plaintext we are going to send a " challenge" which is a hash of the password. this is far more secure.
Frame-Relay
Before we start looking at frame relay let me tell you a little story. We have a network with four sites: there's New York , Los Angeles, Miami and Boston. Since we want connectivity between the sites we have an ISP who sold us there leased line
Between New York and Los Angeles.
Between New York and Miami.
Between New York and Boston.
Using leased lines is awesome you are the only person using these lines since you are paying for them this means high quality and probably a low chance of congestion it's also pretty secure since it's only your traffic that's flowing through these lines.
This is a picture of frame relay and it works a bit different. the idea behind frame relay is that you have a single infrastructure from the service provider and multiple customers are connected to it. effectively sharing everything.
in the middle you see a cloud with an icon you probably haven't seen before this icon is the frame relay switch. the cloud is called the frame relay cloud and the reason it has this name is because for us as customer it's unknown what happens in the frame relay cloud. this is the service provider's infrastructure and we really don't care what happens there we are the customer and all we want is connectivity
It is important to understand the different types of WAN support provided by Cisco. Although this chapter does not cover every type of Cisco WAN support, it does cover the HDLC, PPP, Frame Relay, and ISDN protocols.
A Wide Area Network (WAN) is similar to a Local Area Network (LAN). The main difference is that a WAN operates beyond the geographic scope of a LAN. The major characteristics of a WAN are as follows:
- WANs connect devices located in different geographic regions.
- WANs utilize carriers (WAN service providers) such as cable companies to communicate across the different geographic regions.
- WANs utilize various types of serial connections (typically lower bandwidth than LANs) for communication.
HDLC
PPP
Frame-Relay
HDLC and ppp are point-to-point protocols. if you have two sites, let's say one in new Yourk and the other one in Washington you might get a leased line. A leased line is an example of a point-to-point link and this is where you would run HDLC or PPP.
There is not much to tell you about HDLC It's a point-to-point protocol and it's the default for cisco Routers. HDLC is a standard but running HDLC between routers from different vendors is not going to work. keep this in mind. Every vendor has a proprietary field in their HDLC implementation which is what makes it incompatible between vendores.
PPP ( point-to-point protocol ) is a protocol that I'm going to tell you more about. still have the OSI-model fresh in mind ? I told you WAN protocols operate on the physical and data link layeer I just told you about the physical layer and its serial cables, now it's time for the data link layer.
PPP operates ont the data link layer ( layer 2 ) but as you can see the data link layer has been split into two pieces:
NCP: Network control protocol
LCP: Link control protocol
NCP will make sure you can run different protocols over our PPP link like IP,IPv6 but also
CDP (Cisco Discovery Protocol ) and older protocols like IPX or appletalk.
If you want to use Authentication for PPP you have two options:
PAP (Password Authentication Protocols ) this is plaintext it will send the username and passoword over the PPP link and the router on the other side will check it.
CHAP (challenge Authentication Protocol): Instead of sending the password in plaintext we are going to send a " challenge" which is a hash of the password. this is far more secure.
Frame-Relay
Before we start looking at frame relay let me tell you a little story. We have a network with four sites: there's New York , Los Angeles, Miami and Boston. Since we want connectivity between the sites we have an ISP who sold us there leased line
Between New York and Los Angeles.
Between New York and Miami.
Between New York and Boston.
Using leased lines is awesome you are the only person using these lines since you are paying for them this means high quality and probably a low chance of congestion it's also pretty secure since it's only your traffic that's flowing through these lines.
This is a picture of frame relay and it works a bit different. the idea behind frame relay is that you have a single infrastructure from the service provider and multiple customers are connected to it. effectively sharing everything.
in the middle you see a cloud with an icon you probably haven't seen before this icon is the frame relay switch. the cloud is called the frame relay cloud and the reason it has this name is because for us as customer it's unknown what happens in the frame relay cloud. this is the service provider's infrastructure and we really don't care what happens there we are the customer and all we want is connectivity
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