WAN Connection

WAN Connection – As the messages travel trough the WAN cloud, it will travel from point to point differently depending on the physical WAN connections and protocols in use. WAN connection types are normally dictated by the Wide Area Network service provider, and relate to the physical interface used by the connecting router. Numerous connection types exist, but when possible connections should be made using technologies that support higher data rates and support flexible configurations for the future growth.

Connecting the WAN cloud includes considering the designing the IP addresses within the large corporate network that consists of multiple remote sites, and properly designed the subnet mask that will support the future growth. Some network administrators might think this as difficult jobs especially for beginners. It is not like building a simple network at home, questions like what is my computer IP address is frequently appears. The diagram below is typical structure of WAN connection.

WAN Connection diagram

Notes: DTE is data terminal equipment on the network side of a WAN connection link that sends and receives data. The DTE resides on the subscriber’s premises and marks the point of entry between the LAN and the WAN. DTEs are usually routers, but computers and multiplexers can also act as DTEs. Broadly, DTEs are any equipment at the customer’s site that communicates with the DCE at the other end. Demarc is a demarcation point where the telephone company wiring connects to the customer wiring.

Typically the customer is responsible for all equipment on one side of the demarc, and the phone company is responsible for all equipments on the other side of the demarc. Local loop is the cable that extends from the demarc to the central telephone office. Central office is the switching facility and provides WAN-cloud entry and exit points for incoming and outgoing calls, and acts as a switching point to forward data to other central office. A CO provides services such as switching incoming telephone signals to outgoing trunk lines. It also provides reliable DC power to the local loops to establish an electric circuit.

DCE is data circuit terminating equipment that communicates with DTE and WAN cloud. DCEs are typically routers at the service provider that relay messages between the customers and the WAN cloud. DCE is any device that supplies clocking signals to DTEs. A modem or CSU/DSU at the customer site is often classified as DCE. DCEs maybe devices similar to DTE such as routers except that each device plays a different role.

PSE is packet switching exchange – a switch at the carrier packet-switched network. PSEs are the intermediary points in the WAN cloud. WAN cloud is the hierarchy of trunks, switches, and central offices that make up the network of telephone lines. It is represented as a cloud because the physical structure varies, and different networks with common connection points may overlap.

WAN Connection standard

Minimum recommended standard for WAN connection is:

1. For WAN services using serial WAN connection, use V.35 serial cable.
2. For low speed WAN connection (<64Kbps) commonly associated with analogue PSTN, use RS-232 serial cable.
3. For ISDN BRI connections, the corresponding UTP (CAT5) cable shall use a different color cable (yellow or white) to that of regular LAN cables (blue) to indicate it is a WAN connection. Equipment damage may result if an ISDN circuit is connected to a non-ISDN device.
4. For ISDN WAN connection, Terminal Adapters (TAs) should be avoided; rather native ISDN routers should be used.
5. All cabling shall be secure, documented and clearly labeled. Many carriers offer connection choices when provisioning WAN services.WAN connection typically has 3 categories as follows: 1. Dedicated point-to-point or leased lines (synchronous serial), such as T1, T3 2. Circuit-switched networks (asynchronous serial), such as ISDN 3. Packet-switched networks (synchronous serial), such as Frame relay, X.25

Dedicated wan connection or leased line

A dedicated WAN connection or leased line connection is a permanent, dedicated point-to-point connection between one device and another with the following characteristics:

1. Dedicated point-to-point – synchronous serial
2. Permanent connection, such as T1, T3
3. High availability
4. Lines are usually leased from a WAN service provider
5. Lease line is more expensive than other WAN solutions
6. Use separate WAN connections between each point

WAN Connection - Leased line

When should we use this type of WAN connection? We can use this dedicated leased line WAN connection when you:

1. Have a high data traffic over the WAN connection
2. Need constant connectivity between sites
3. Have few interconnected sites See also Point-to-point protocol - one of WAN protocol that use this type of WAN connection

Circuit switched networks

This circuit switched WAN connection type gives you an alternative to leased lines, letting you use shared lines. This WAN connection type works both ways, allowing both dial-in and dial-up WAN connections. When you use this circuit switched WAN connection:

1. The sending computer dials-in to the line and the WAN connection is set up.
2. The receiving computer sends acknowledgement and locks the line.
3. The sending computer transmit the data over this WAN connection
4. After the transmission is complete, the connection is released for other users.

WAN Connection switched circuit

A circuit switched network uses switched virtual circuit (SVCs). A dedicated data transmission path is established before communication begins by throwing electrical switches. The path remains until the communication ended. See also ISDN circuit-switched network that use this type of WAN connection.

Packet switched networks

Packet switched networks do not require a dedicated or temporary reserved line. Instead, a message’s path is dynamically set as the data flows through the network. This WAN connection type has the following characteristics:

1. Messages are divided into packets.
2. Packets travel independently through the internetwork (i.e. take different paths)
3. Packets are reassembled into the correct order at the receiving end
4. Sending and receiving devices assume an ‘always on’ connection (no dials-up needed)

This wan connection type – packet switched networks use permanent virtual circuits (PVCs). Although a PVC looks like a direct, dedicated WAN connection, the path each packet can take through the internetwork can vary.

WAN Connection - packet switched

Note that dedicated and packet switched networks have an always available WAN connection to the network, while circuit switched network must first establish the physical WAN connection between devices (through dial-up). Dial-on-demand routing (DDR) can simulate an always on WAN connection without the cost. With DDR, routers automatically open new WAN connections when data needs to be sent, and close them when the line is idle. Newer WAN connection technologies further improve this process by shortening the WAN connection establishment (dialing) process.

See also:

• frame relay solution that uses this type of WAN solution.
• Best wireless routers for home usage – a guideline
• Router connections – the guideline