Lect 1 Wan Overview Flashcards
Differences btn WAN and LAN?
- Wan occupy large area
- Wan controlled by multiple organizations/LAN single admin
- Lans have high speed connections.
- Wan carries multiple services btn many sites.
- Wan are owned by service providers, Lan owned by organizations.
4 WAN topologies
- Point to point.
- Hub-and-spoke.
- Full Mesh.
- Dual homed technology.
Point to point
Involves leased line connection btn two end points transparent to customer’s network.
Hub and Spoke
Single interface to the hub can be shared by spoke ckts which are connected using virtual ckts.
Full mesh
Sites can communicate with any other site directly using virtual ckts.
Dual homed
Provides a redundancy & load balancing tho expensive to implement.
Layers that WAN operates?
Layer 1 and 2 -> Physical and Data link Layers
Data Terminal Equipment - DTE
Customer devices that pass data from a customer net for transmission over the WAN.
Demarcation point
Point in a building to separate customer equipment from service provider equipment.
Local loop/Last mile
Copper or fiber cable connecting CPE to the Central Office CO of service provider.
Central Office CO
Local service provider facility/building that connects CPE to the provider network.
Toll network
Consists long haul, all-digital, fiber optic communication lines and other equipments inside WAN network.
Dialup modem
Tech that converts digital signals into voice frequencies transmitted over analog lines of public telephone network.
Access Server
Tech that controls and coordinates dialup modem, dial-in and dial-out user communications.
Broadband Modem
Type of digital modem used with high speed DSL or cable internet service.
Channel Service Unit CSU
Provides termination for the digital signal and ensure connection integrity through error correction and monitoring.
Data Service Unit - DSU
Converts line frames into frames that the LAN can interpret and vice versa.
Core router/multilayer switch
Router or switch that resides within the middle or backbone of the WAN.
Circuit-switched network
One that establishes a dedicated ckt/channel btn nodes and terminals b4 users communicate.
Common types of Circuit Switched Network
- Public Switched Telephone Network (PSTN)
- Integrated Services Digital Network (ISDN)
Packet-switched network
One that splits traffic data into packets that are routed over a shared network.
Packet switched net link determination approach
- Connectionless eg internet
- Connection oriented systems eg frame relay
WAN link connection options
- Public - internet - broadband vpn - e.g DSL Cable wireless.
- Private
i. Dedicated - leased lines e.g T1/E1 and T3/E3.
ii. Switched- Pkt Switched e.g MPLS, ATM.
- Ckt Switched e.g PSTN, ISDN.
Two types of ISDN interface
- Basic Rate Interface - BRI
- Primary Rate Interface - PRI
BRI
Provides two 64 Kb/s bearer(B) channels for carrying voice and data and a 16 Kb/s delta(D) channel for signaling, call setup and other purposes.
PRI
Provides 23 B channels with 64 Kb/s and one D channel with 64 Kb/s for total bit rate of 1.544 Mb/s
WAN standards include
- Physical Adressing
- Flow Control
- Encapsulation
Delay/Latency
Caused when device processes the frame b4 sending.
Jitter
Variation in delay of received packets.
Types of Virtual Circuits
- Switched Virtual Circuit
- Permanent Virtual Circuit
Integrated Services Digital Network (ISDN)
Is a ckt switching tech that enables local loop of a PSTN to carry digital signals thru TDM.
Frame Relay
Layer 2 non broadcast multi-access (NBMA) WAN tech used to interconnect enterprise LANs.
Asynchronous Transfer Mode(ATM)
Tech capable of transfering voice,video and data thru private and public networks.
Multi Protocol Label Switching (MPLS)
Is a multiprotocol high performance WAN tech that directs data from one router to the next.
Very Small Aperture Terminal VSAT
Is a solution that creates a private WAN using satellite communications.
Digital Subscriber Line DSL
An always on connection that uses existing twisted pair telephone lines to transport high bandwidth data, and provides IP services to subscribers.
VPN
Is an encrypted connection between a private net over a public net such as the internet.
Benefits of VPN
- Cost saving
- Security
- Scalability
- Compatibility with broadband technology
Two types of VPN access
- Site to site VPNs
- Remote Access VPNs
Site to site VPN
Connects entire networks to each other. E.g a branch office net to company HQ.
Remote access VPNS
Enables mobile users to access company’s net securely over the internet.
