Post Midterm: Lectures 12: WANs Flashcards
What is circuit switching? in WAN
dedicated circuit connects 2+ parties, same path from source to the destination
fee is according to time connected to the circuit
What is packet switching? in WAN
travels one at a time from source, might take different physical paths
fixed fee for users
2 types of circuit switched services?
POTS (plain old telephone service): each LAN is connected to a modem which is connected to a common carrier network
ISDN (integrated services digital network): provides digital dial up lines, but acceptance has been slow
*low data transmission, need to make separate connection each time, but cheap and easy
What is a dedicated circuit and how is it billed?
leased circuits, used to create site to site links between organizational locations
billed at flat fee per month
What is a Packet Switched Service? how it is billed?
user buys connection into common carrier network and connects via a PAD (packet assembly device)
pay fixed price for connection and fees for amount of data transmitted
what is frame relay? who offers it?
a delivery service, error free circuits
offered by phone companies for LAN interconnection
what is ATM? (asynchronous transfer mode) and why is it faster and more predictable?
international standard for frame relay
segments packets in 53 byte cells, the consistent lengths allow for faster and more predictable delivery times
protocols are supported by both LAN and WAN
what is MPLS? (multi protocol label switching)
it labels packets when it enters a label, it is used in forwarding decisions and traffic engineering
what is VPLS? (virtual private LAN service)
Ethernet-based point-to-multipoint Layer 2 virtual private network (VPN)
connects geographically dispersed ethernet LAN sites using MPLS backbone
how do VPN services work?
encapsulates packets with special protocols to encrypt the IP packets.
creates permanent virtual circuits/tunnels that run over the public internet
what makes a VPLS different than a layer 2 VPN?
VPLS is a multi-point to multipoint/ any to any
(they are able to communicate with other end users regardless of whether or not they are on the same network)
layer 2 VPN (point to point, PPP, a direct communication between two nodes in a network)
what is PPP (point to point protocol)?
TCP/IP protocol that is used to connect one computer system to another
Exists when two systems are physically connected through a telephone line.
What is frame relay?
What is ATM? (asynchronous transfer mode)
