Just a few questions related to wide area network services

thedrama

You know, Ethernet networks(LAN) handle MAC addressing during packet transmission. (Destination MAC address is learned through ARP request if its not placed on its ARP cache before if transmitting device is a PC or router.
However, on leased lines which packet encapsulation is made via HDLC or PPP protocols, how is the addressing made? I mean, HDLC or PPP frame has an "address" field but does it have a special name as it was on MAC and while packet is on the network layer of transmitting router, what should be learned from the other end instead of MAC?


Second and the last,

On point to point dedicated lines, is the router on one end "directly connected" to the one on the other? or between these routers, is it possible to mention that WAN switches are interconnecting them even though
this type is called point-to-point ?
Edit : i asked this because it is shown as "link going through WAN switches following a dedicated path" in my study guides but it is written "point-to point" without any intermediate device which sticks its nose into.

Greenmet29

Point to point leased lines are exactly that... leased, or dedicated, lines. They do go through some type of service provider, but what happens behind the csu/dsu, stays behind the csu/dsu. At least at the CCNA level it does.

In other words, they [probably] are switched, but it is a dedicated line, that no one else has access to, that is from router A to router B. Therefore there is no need for a mac address type field. It would be like if your having lunch with your friend John, and everytime you say something to him you say his name first. You could do it, but there is no need for it because it is a conversation between you and John.

In frame relay there is, because they are many to many connections. For FR, they mac address type field is called the "dlci", or data link control identifier.