- Private Circuit Technologies
- Dedicated Line: Always available, reserved for communication.
- Leased Line: Type of dedicated line.
- T1: 1.5 Mbps via telephone line.
- T3: 44.7 Mbps via telephone line.
- E1: European standard, 2.048 Mbps digital transmission.
- Serial Line IP (SLIP)
- Function: Used for TCP/IP over slow interfaces for communication with external hosts.
- Limitations: No authentication, supports only half-duplex communication, no error detection, manual link establishment and teardown.
- Point to Point Protocol (PPP)
- Improvement on SLIP: Adds login, password, and error correction (by CHAP and PAP).
- Capability: Supports full-duplex communication.
- Integrated Services Digital Network (ISDN)
- Combination: Digital telephony and data transport.
- Usage: Overtaken by xDSL, limited by “D Channel” for call management.
- xDSL (Digital Subscriber Line)
- Function: Uses telephone lines to transport high bandwidth data.
- Types:
- ADSL: Asymmetric, up to 18,000 feet, more downstream bandwidth.
- SDSL: Symmetric, up to 10,000 feet.
- HDSL: High Rate, T1 speed, up to 12,000 feet.
- VDSL: Very High Speed, 13-52 Mbps down, 1.5-2.3 Mbps up, up to 4,500 feet.
- Circuit-Switched Networks
- Operation: Requires a dedicated physical circuit path during transmission, used for constant communication, typically in voice networks, sensitive to connection loss.
- Message Switching Networks
- Operation: Transmits messages from node-to-node, storing them until a forwarding path is available.
- Packet-Switched Networks (PSN or PSDN)
- Operation: Nodes share bandwidth by sending small data units (packets), which are reassembled at the destination. Creates virtual circuits only when needed, cost-effective, but sensitive to data loss.
This overview of WAN protocols provides a comprehensive understanding of how different communication methods work over wide area networks, highlighting their capabilities and limitations.