CCNA4 Chapter 1: Intro to WANs
The Cisco Enterprise Branch Architecture enables enterprises to offer important network services
such as security, new communication services, and improved application performance to every
office regardless of its size or proximity to headquarters
The Cisco Enterprise Teleworker Architecture allows the enterprise to deliver secure voice and data
services no matter where or when they work
The distribution layer of the hierarchical model layer is responsible for containing network problems
to the workgroups in which they occur
The local loop is the cabling that connects the customer’s site to the nearest exchange of the WAN
service.
Circuit Switching – A switching technology that has pre-established dedicated circuit or channel
between nodes and terminal
Connection –oriented Packet Switching – A switching technology where a VC is only physical in
existence while a packet is travelling through it
Packet switching – A switching technology where a VC is only physically in existence while a packet is
travelling through it.
X.25 - Operates at the network layer, and the SVC is identified by a channel number
Frame Relays – Operates at the data-link later and the PVC is identified by a data link control
identifier (DLCI)
ATM – Built on a cell-based architecture in which the cell has a fixed length of 53 bytes
Metro Ethernet – Providers a high-bandwidth Layer 2 network capable of managing data, voice, and
video all on the same infrastructure.
Leased line is a type of WAN connection that should be chosen when dedicated P-to-P WAN
communications path from the customer premises through the provider network to a remote
destination.
Frame relay circuits are identified using DLCI (Data-Link control identifier)
ATM is designed to deliver data, voice and video simultaneously over as TDM (Time division
multiplexing) infrastructure
ISDN (PRI) is composed of 23 B channels in Nth America.
DSU/CSU (Data service unit, Channel service unit)
CSU provides data termination and DSU converts T-carrier frames into framers the LAN can interpret
(i.e. IP)
WAN switch, multiport internetworking device that is used on carrier networks. They typically switch
WAN traffic such as Frame Relay, ATM or X.25 and operate in the Data-link layer.
WAN Cabling types
TIA 232 – 25pin D-connector – 64kbps
TIA 449 – 36pin D-Connector – 2Mbps
TIA 612-3 – 60pin D-connector – 52Mbps
V.35 – 34pin rectangular connector- 2.048Mbps
X.21 – 15pin D connector
Data-link Protocols
Dedicated P-to-P
Cisco HDLC
PPP
Packet Switched
X.25
Frame Relay
ATM
Circuit Switched
ISDN