Data pathways used in WAN communications links

Circuit switching requires a dedicated physical connection between each communication endpoint.

Virtual circuit switching forms a logical connection between each communication endpoint.

ISDN (Integrated Services Digital Network)

Each ISDN channel has 64 Kbps capacity:

• ISDN BRI interface has 2 bearer channels for total capacity of 128 Kbps
• ISDN PRI interface has 23 bearer channels for total capacity of 1.544 Mbps

T-carrier leased lines

Commonly used T-carrier leased lines:

• T1 has capacity of 1.544 Mbps
• T3 has capacity of 44.736 Mbps
• E1 has capacity of 2.048 Mbps
• E3 has capacity of 34.368 Mbps

SONET (Synchronous Optical Network)

SONET networks:

• OC-1 has capacity of 51.84 Mbps
• OC-3 has capacity of 155.52 Mbps
• OC-12 has capacity of 622.08 Mbps
• OC-24 has capacity of 1.244 Gbps
• OC-48 has capacity of 2.488 Gbps
• OC-96 has capacity of 4.976 Gbps
• OC-192 has capacity of 9.953 Gbps
• OC-768 has capacity of 39.813 Gbps

The European counterpart to SONET is known as SDH (Synchronous Digital Hierarchy).

X.25

The maximum capacity of X.25 networks is 56 Kbps. It was one of the original packet switching technologies, which was particularly successful with supply chain networks.

Frame Relay

Frame Relay improved on X.25 by using virtual circuits and smaller variable-length packets to deliver capacity of up to 1.544 Mbps.

ATM (Asynchronous Transfer Mode)

ATM is similar to Frame Relay because it uses virtual circuits and it improved on it by using fixed length cells to deliver capacity of up to 622 Mbps.

Internet VPN (Virtual Private Network)

Internet VPN uses encryption to establish a virtual circuit running over IP networks.