CH1 - Introduction to WANs
A WAN is a data communications network that operates beyond the geographic scope of a
LAN.
As companies grow, adding more employees, opening branch offices, and expanding into
global markets, their requirements for integrated services change. These business
requirements drive their network requirements.
The Cisco Enterprise Architecture expands upon the Hierarchical Design Model by further
dividing the enterprise network into physical, logical, and functional areas.
Implementation of a Cisco Enterprise Architecture provides a secure, robust network with
high availability that facilitates the deployment of converged networks.
WANs operate in relation to the OSI reference model, primarily on Layer 1 and Layer 2.
Devices that put data on the local loop are called data circuit-terminating equipment, or
data communications equipment (DCE). The customer devices that pass the data to the DCE
are called data terminal equipment (DTE). The DCE primarily provides an interface for the
DTE into the communication link on the WAN cloud.
The physical demarcation point is the place where the responsibility for the connection
changes from the enterprise to the service provider.
Data Link layer protocols define how data is encapsulated for transmission to remote sites
and the mechanisms for transferring the resulting frames.
A circuit-switching network establishes a dedicated circuit (or channel) between nodes and
terminals before the users may communicate.
A packet-switching network splits traffic data into packets that are routed over a shared
network. Packet-switching networks do not require a circuit to be established and allow
many pairs of nodes to communicate over the same channel.
A point-to-point link provides a pre-established WAN communications path from the
customer premises through the provider network to a remote destination. Point-to-point
links use leased lines to provide a dedicated connection.
Circuit-switching WAN options include analog dialup and ISDN. Packet-switching WAN
options include X.25, Frame Relay, and ATM. ATM transmits data in 53-byte cells rather than
frames. ATM is most suited to video traffic.
Internet WAN connection options include broadband services, such as DSL, cable modem or
broadband wireless, and Metro Ethernet. VPN technology enables businesses to provide
secure teleworker access through the Internet over broadband services.
A WAN is a data communications network that operates beyond the geographic scope of a
LAN.
As companies grow, adding more employees, opening branch offices, and expanding into
global markets, their requirements for integrated services change. These business
requirements drive their network requirements.
The Cisco Enterprise Architecture expands upon the Hierarchical Design Model by further
dividing the enterprise network into physical, logical, and functional areas.
Implementation of a Cisco Enterprise Architecture provides a secure, robust network with
high availability that facilitates the deployment of converged networks.
WANs operate in relation to the OSI reference model, primarily on Layer 1 and Layer 2.
Devices that put data on the local loop are called data circuit-terminating equipment, or
data communications equipment (DCE). The customer devices that pass the data to the DCE
are called data terminal equipment (DTE). The DCE primarily provides an interface for the
DTE into the communication link on the WAN cloud.
The physical demarcation point is the place where the responsibility for the connection
changes from the enterprise to the service provider.
Data Link layer protocols define how data is encapsulated for transmission to remote sites
and the mechanisms for transferring the resulting frames.
A circuit-switching network establishes a dedicated circuit (or channel) between nodes and
terminals before the users may communicate.
A packet-switching network splits traffic data into packets that are routed over a shared
network. Packet-switching networks do not require a circuit to be established and allow
many pairs of nodes to communicate over the same channel.
A point-to-point link provides a pre-established WAN communications path from the
customer premises through the provider network to a remote destination. Point-to-point
links use leased lines to provide a dedicated connection.
Circuit-switching WAN options include analog dialup and ISDN. Packet-switching WAN
options include X.25, Frame Relay, and ATM. ATM transmits data in 53-byte cells rather than
frames. ATM is most suited to video traffic.
Internet WAN connection options include broadband services, such as DSL, cable modem or
broadband wireless, and Metro Ethernet. VPN technology enables businesses to provide
secure teleworker access through the Internet over broadband services.
