Chapter 9: Wide Area Networks (WAN) Complete Exam Questions And Correct Detailed Answers.

Wide Area Networks (WANs) - correct answer Run long distances Connect different offices in different cities or countries or different buildings in the same city WANs are rented/leased through? - correct answer Common carriers such as AT&T Dedicated-circuit network (private line services) - correct answer User leases circuit from carrier for exclusive 24/7 use Private network but managed by carrier Channel Service Unit (CSU) / Data Service Unit (DSU) - correct answer WAN equivalent of a NIC in a LAN Takes outgoing packets and translate it to use the data link layer and network protocols used in the WAN How are dedicated-circuit networks charged? - correct answer Flat fee/month with unlimited use of the circuit Why do dedicated-circuit networks require careful planning in terms of locations and capacity purchased? - correct answer Changing your contract/plan could be expensive and lead to rewiring and a new contract Ring Architecture - correct answer Connects all computers in a closed loop Full-duplex and half-duplex so messages flow either way Disadvantage of a ring architecture - correct answer Messages can take a long time to travel Star Architecture - correct answer Connects all computers to one central computer that routes messages Advantages of star architecture - correct answer Easy to manage Faster than ring architecture If central computer fails, entire network fails Disadvantage of star architecture - correct answer Most susceptible to traffic problems Full-Mesh Architecture Every computer is connected to every other computer Why aren't full-mesh networks used often? - correct answer Very costly Partial-Mesh Architecture (Mesh Architecture) - correct answer Many computers are connected, but not all Fairly common Why are mesh networks often used? - correct answer Combine performance benefits of both ring and star networks Short routes w/ many possible routes Disadvantage of mesh networks? - correct answer Use decentralized routing so each computer does its own routing Requires more processing Types of Dedicated-Circuit Services - correct answer T carrier and SONET T Carrier Circuits - correct answer Copper Lease a dedicated circuit from one building in one city to another building in the same/different city Costs are fixed per month SONET Services - correct answer Fiber American standard for high-speed dedicated-circuit services Packet-Switched Networks - correct answer They enable multiple connections to exist simultaneously between computers over the same physical circuit unlike dedicated-circuit/dialed-circuit and circuit-switched which is only between two computers Packet Assembly/Disassembly Device (PAD) - correct answer Owned by either customer or common carrier converts sender's data and sends them through the packet-switched network and then reassembles the packet and delivers to appropriate computer Advantage of packet-switched services - correct answer Different locations can have different connection speeds and the PAD compensates for differences in transmission speed Are dedicated-circuit or packet-switched circuit networks harder to design? - correct answer Dedicated-circuits Making changes are expensive and often mean rewiring Permanent Virtual Circuits - correct answer Connections between different locations in the packet network (switched is not as common) Committed Information Rate (CIR) - correct answer Data rate the PVC guarantees to transmit Maximum Allowable Rate (MAR) - correct answer Maximum rate that the network will attempt to provide Discard Eligible (DE) - correct answer When packets go over the CIR, they are marked this and could be discarded if the network becomes overloaded Point of Presence (POP) - correct answer Location at which the packet-switched network connects to the local telephone exchange Types of packet-switched services - correct answer Frame relay MPLS Ethernet services IP services Frame Relay - correct answer Most common but unreliable b/c doesn't perform error control Checks for errors and discards those packets MPLS - correct answer Sometimes called layer 2.5 technology b/c it inserts four-byte header that contains information between layer-2 frame and layer 3 IP packet IP services - correct answer A long-term winning because the internet utilized TCP/IP Virtual Private Network (VPN) - correct answer Private packet-switched network over public internet VPN Gateway - correct answer A specially designed router to provide access to the VPN How do VPNs work? - correct answer They take the outgoing packet and encapsulates it with a protocol that travels through a tunnel to the VPN gateway on the other side Backbone → VPN gateway → VPN tunnel (internet) → VPN Gateway → Backbone Best Practice WAN Design - correct answer Small WANs with low/moderate data can use VPNs or frame relay services High-traffic networks should use ethernet, IP, and MPLS service