WAN PROTOCOLS

Protocol

Type

Layer

Characteristics

X25

Packet Switched

Data-link and Physical

ITU-T standard (International Telephone Union – Telecommunications Standardization Sector) Addresses expressed in decimal numbers in the following format:

Frame Relay

Packet Switched

Data-link and Physical

Connection-oriented and similar to X.25 with less overhead but does not provide error correction. More cost-effective than PPP. Uses Permanent Virtual Circuits (PVC) mostly but also Switched Virtual Circuits (SVC)

HLDC

Dedicated Connection Bit Oriented

Data-link

peer-to-peer HDLC not intended to encapsulate multiple Network layer protocols across the same link, which prompted vendors to have their own proprietary HDLC protocol. No authentication is provided by HDLC. Default encapsulation of serial links, which have a default bandwidth of 1.54 Mbps (T1).

SDLC

Bit Oriented

Data-Link

Full-Duplex non peer-to-peer bit oriented serial protocol created by IBM.

ISDN

Circuit Switching

Physical, Data-link and Network, typically used with PPP.

Set of digital services that transmit voice and data over existing phone lines. The Basic Rate Interface (BRI) consists of two B channels at 64 kbps and one D channel at 16 kbps. PRI (Primary Rate Interface) T1 is 23 X 64kbps B channels and 1X 64 kbps D channel, and the PRI E1 is 30 X 64 kbps B channels and 1 X 64kbps D channel.

ATM

Asynchronous Transfer Mode

53-byte cell that allows fast hardware base switching. LANE (LAN Emulation) was created to hite ATM and look like 802.3 Ethernet.

PPP

Dedicated Connection

Data-link

Can be used to create point-to-point links between different vendors’ equipment. Allows authentication and multilink connections and can be run over asynchronous (dial-up) and synchronous (ISDN) links. Created to replace SLIP (Serial Line Internet Protocol) which could only run IP at the Network Layer but was also a dedicated connection protocol. Stacker and Predictor compression methods are supported.

LAPB

Data-link

Connection-oriented, has tremendous amount of overhead for links that are error-prone. Defined by X.25 at the data-link layer