Networking Final Exam Questions with
Complete Answers
Path Determination - Answer-Route taken by packets from source to destination
(routing algorithms)
Switching - Answer-Move packets from router's input to appropriate router output
Call setup - Answer-Some network architectures require router call setup along path
before data flows
Forwarding - Answer-Move packets from router's input to appropriate router output
Analogy: Process of getting through single interchange
Routing - Answer-Determine route taken by packets from source to destination
Analogy: Process of planning trip from source to destination
Connection Setup - Answer-Before datagrams flow, two end hosts and intervening
routers establish virtual connection
Difference between connection setup in the network layer vs. the transport layer -
Answer-Network layer connects two hosts (may also involve intervening routers),
transport layer connects two processes
Guaranteed Delivery - Answer-This service guarantees that the packet will eventually
arrive at its destination
Guaranteed delivery with bounded delay - Answer-This service not only guarantees
delivery of the packet, but delivery within a specific host to host delay bound (for
example, within 100 ms)
Network Service Model - Answer-Defines the characteristics of end-to-end transport of
packets between sending and receiving end systems
Services for individual datagrams - Answer-- Guaranteed Delivery
- Guaranteed Delivery with bounded delay
Services for a flow of datagrams - Answer-- In-order datagram delivery
- Guaranteed minimum bandwidth to flow
- Guaranteed maximum jitter
- Security services
In-order packet delivery - Answer-This service guarantees that packets arrive at the
destination in the order that they were sent
, Guaranteed minimal bandwidth - Answer-This network-layer service emulates the
behavior of a transmission link of a specified bit rate between sending and receiving
hosts. As long as the sending host transmits bits at a rate below the specified bit rate,
then no packet is lost and each packet arrives within a pre-specified host-to-host delay
Security Services - Answer-Using a secret session key known only by a source and
destination host, the network layer in the source host could encrypt the payloads of all
datagrams being sent to the destination host. The network layer in the destination host
would the be responsible for decrypting the payloads. With such a service,
confidentiality would be provided to all transport-layer segments (TCP and UDP)
between the source and destination hosts. In addition to confidentiality, the network
layer could provide data integrity and source authentication services.
Best-Effort Service - Answer-The timing between packets is not guaranteed to be
preserved, packets are not guaranteed to be received in the order in which they were
sent, not is the eventual delivery of transmitted packets guaranteed.
Provides network-layer connection-less service - Answer-Datagram Networks
Provides network-layer connection service - Answer-Virtual-Circuit Networks
Virtual Circuits - Answer-A network-layer connection that consists of a path between the
source and destination hosts, numbers for each link along the path, and entries in the
forwarding table in each router along the path.
Key router functions - Answer-- Run routing algorithms / protocol
- Switching datagrams from incoming to outgoing link
Decentralized switching - Answer-Given datagram destination, lookup output port using
forwarding table in input port memory
Memory Switching Fabrics - Answer-Traditional computers with switching under direct
control of CPU. Packet copied into system's memory, CPU looks up dest and sends to
output port. Limited bu memory bandwidth
Bus Switching Fabrics - Answer-Datagram from input port memory to output port
memory via a shared wire
Crossbar Switching Fabrics - Answer-Forwards multiple packets in parallel. Controller
closes cross point at intersections of busses
Buffering - Answer-Required when datagrams arrive at output port from fabric faster
than the transmission rate
Scheduling Discipline - Answer-Chooses among queued datagrams from transmission
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