need for wan encapsulation?

[ashish1542]

Hi,

The question may seem stupid, but i do want to know what is the need for WAN encapsulation (HDLC, PP etc.). Is it there only to distinguish between frames, provide synchronisation and provide CRC error indications, or there some other reason. Also when a router prepares a packet for transmission across a WAN (assuming a point to point link), what sort of layer 2 to layer 3 mappings would be used(as arp is not used on WAN ). Just a little confused, and need some solid theory to clear my doubts. Thanks in advance

 

[svermill]

WAN encapsulation is used for all of the reasons you listed above. In some network architectures, routing information is encoded into the WAN header (think ATM PVCs). In the case of p-t-p WAN connections for routers, the mapping is the routing table. Network such and such is available through network such and such, which is directly attached to serial interface so and so.

Probably the most important thing that most WAN protocols/encapsulations do in a traditional serial interface router environment is to ensure data integrity.

 

[ashish1542]

Thanks svermill, can you suggest some reading material for the same.

 

[svermill]

I can't personally recommend a single source that I myself have read. There are just so many protocols out there and each is a course of study on its own. However, Howard Berkowitz wrote a book called "WAN Survival Guide." I hope to get around to reading for myself someday soon. Based on what I know of Howard, it is in all likelihood an excellent, accurate, insightful tome on all things WAN. You might want to check it out.

 

[Lucas2]

You may try a document "Wan Quick Start" at Cisco.com