NE NE WAN Technologies 2 — Questions and Answers
Question 1: What does 'last-mile connectivity' refer to in WAN terminology?
- The final routing hop before the destination host
- The physical connection between the service provider's network and the customer's premises (Correct answer)
- The backup WAN link used during outages
- The final segment in an MPLS label-switched path
Correct answer: The physical connection between the service provider's network and the customer's premises
Last-mile connectivity is the link from the ISP's nearest point of presence (PoP) to the customer site, often the bottleneck in WAN performance.
Question 2: Which WAN technology uses asymmetric speeds and is delivered over existing telephone copper lines?
- Cable (DOCSIS)
- Fiber optic (GPON)
- DSL (xDSL) (Correct answer)
- T1 leased line
Correct answer: DSL (xDSL)
DSL delivers broadband over telephone copper pairs with faster download speeds than upload, with variants including ADSL, VDSL, and G.fast.
Question 3: What is the purpose of a WAN edge router?
- To connect wireless access points to the LAN
- To connect the enterprise LAN to the service provider WAN and manage routing policies (Correct answer)
- To provide NAT services for internal servers
- To aggregate switch ports in the data center
Correct answer: To connect the enterprise LAN to the service provider WAN and manage routing policies
The WAN edge router sits at the boundary between the enterprise network and the service provider, handling routing protocols like BGP and policy enforcement.
Question 4: In MPLS networks, what is the role of the Label Edge Router (LER)?
- To remove labels from all transit packets
- To impose or dispose of MPLS labels at the edge of the MPLS domain (Correct answer)
- To run BGP between customer sites
- To assign IP addresses via DHCP
Correct answer: To impose or dispose of MPLS labels at the edge of the MPLS domain
LERs (also called Provider Edge routers) add MPLS labels to incoming packets (ingress) and remove them at the destination edge (egress) of the MPLS domain.
Question 5: What is a CIR (Committed Information Rate) in Frame Relay or MPLS services?
- The maximum burst speed allowed on the circuit
- The guaranteed minimum bandwidth the service provider commits to deliver (Correct answer)
- The cost per gigabyte of transferred data
- The latency SLA for the WAN connection
Correct answer: The guaranteed minimum bandwidth the service provider commits to deliver
CIR is the contracted minimum bandwidth that the service provider guarantees to deliver under normal conditions; traffic above the CIR may be discarded during congestion.
Question 6: Which technology allows multiple customer networks to share the same physical fiber infrastructure while maintaining logical separation?
- DWDM
- GPON (Gigabit Passive Optical Network) (Correct answer)
- DOCSIS
- PPPoE
Correct answer: GPON (Gigabit Passive Optical Network)
GPON uses passive optical splitters to deliver shared fiber from a central OLT to multiple ONT devices at customer premises, providing logical separation via VLAN or GPON port IDs.
NE NE WAN Technologies 2
What does 'last-mile connectivity' refer to in WAN terminology?