Day 7 & 8 : WAN Protocols

WAN protocols specifications are defined in lower layers of OSI protocols, most of them at physical and data link layer and some at network layer.

Physical layer specifications define speed and channel. There are
1. Unchannelized circuits
2. Channelized circuits (ISDN PRI, ISDN-BRI)

Both channelized and unchannelized circuits are available at different speed. Minimum speed is 64Kbps and is known as DS0 speed.
DS1, also known as T1, has 24 times of DS0 channel and thus operates at 1.54Mbps.
DS3, also known as T3, has 30 times of DS1 channel and thus operates at 45Mbps
More information about T career
Up to DS3 circuit is delivered over copper cabling. Speed higher than DS3 circuits are delivered over optical cable. More information about Optical career

Data link layer specifications define framing. For example,
1. HDLC (proprietary to Cisco equipment)
2. PPP
3. Frame Relay
4. LAPD (framing for ISDN D channel)

ISDN
ISDN stands for Intergrated Services Digital Network. ISDN protocols define lower 3 layers of OSI protocol.
ISDN BRI has 2 data channels and 1 control channel. Data channel is called B channel and control channel, D channel. ISDN BRI is also called 2B1D. Each B channel has 64Kbps and can carry either a voice conversation or 64Kbps of data. D channel has 16Kbps.
ISDN PRI has 23 data channels and 1 control channel and thus it is called 23B1D. Each B channel has 64Kbps and D channel also has 64Kbps. ISDN PRI is mainly used in PBX systems.