Computer Networking: A Top-Down
Approach, Chapter 4 UPDATED ACTUAL
Exam Questions and CORRECT Answers
Network layer availability - CORRECT ANSWER - In every host and router
2 key network-layer functions - CORRECT ANSWER - forwarding and routing
Forwarding - CORRECT ANSWER - move packets from router's input to appropriate
router's output
Routing - CORRECT ANSWER - determine route take by packets from source to
destination
Why use address ranges? - CORRECT ANSWER - 4 billion IP addresses
longest prefix matching - CORRECT ANSWER - when looking for forwarding table entry
for given destination address, use longest address prefix that matching destination address
2 key router functions - CORRECT ANSWER - run routing protocols, forward datagrams
routing architecture - CORRECT ANSWER - routing processor (compute forwarding
tables, routing, management control plane, done in software), high-speed switching fabric
(forwarding data plane, done in hardware)
Input ports - CORRECT ANSWER - line termination (physical layer); link layer protocol
to receive; lookup, forwarding, queueing
, decentralized switching - CORRECT ANSWER - given datagram destination, lookup
output port using forwarding table in input port memory. Complete input port processing at line
speed. Queuing if datagrams arrive faster than forward rate into switch fabric
switching fabric - CORRECT ANSWER - transfer packet from input buffer to output
buffer
switching rate - CORRECT ANSWER - rate at which packets are transfered from input to
output, desirable at N * line rate, with N inputs
switching fabric types - CORRECT ANSWER - memory, bus, crossbar
switching via memory - CORRECT ANSWER - switching under control of CPU, packet
copied to main memory, speed limited by memory bandwidth
switching via bus - CORRECT ANSWER - datagram moves via a shared bus, bus
contention (speed limited by bus bandwidth)
switching via crossbar - CORRECT ANSWER - overcome bus bandwidth, connect
processors to multiprocessors, parallel transmissions
output ports - CORRECT ANSWER - datagram buffer and queue, link layer protocol to
send, line termination
output port buffering - CORRECT ANSWER - required when datagrams arrive from
fabric faster than transmission rate. queuing and loss due to buffer overflow.
scheduling discipline - CORRECT ANSWER - choose among queued datagrams for
transmission
Approach, Chapter 4 UPDATED ACTUAL
Exam Questions and CORRECT Answers
Network layer availability - CORRECT ANSWER - In every host and router
2 key network-layer functions - CORRECT ANSWER - forwarding and routing
Forwarding - CORRECT ANSWER - move packets from router's input to appropriate
router's output
Routing - CORRECT ANSWER - determine route take by packets from source to
destination
Why use address ranges? - CORRECT ANSWER - 4 billion IP addresses
longest prefix matching - CORRECT ANSWER - when looking for forwarding table entry
for given destination address, use longest address prefix that matching destination address
2 key router functions - CORRECT ANSWER - run routing protocols, forward datagrams
routing architecture - CORRECT ANSWER - routing processor (compute forwarding
tables, routing, management control plane, done in software), high-speed switching fabric
(forwarding data plane, done in hardware)
Input ports - CORRECT ANSWER - line termination (physical layer); link layer protocol
to receive; lookup, forwarding, queueing
, decentralized switching - CORRECT ANSWER - given datagram destination, lookup
output port using forwarding table in input port memory. Complete input port processing at line
speed. Queuing if datagrams arrive faster than forward rate into switch fabric
switching fabric - CORRECT ANSWER - transfer packet from input buffer to output
buffer
switching rate - CORRECT ANSWER - rate at which packets are transfered from input to
output, desirable at N * line rate, with N inputs
switching fabric types - CORRECT ANSWER - memory, bus, crossbar
switching via memory - CORRECT ANSWER - switching under control of CPU, packet
copied to main memory, speed limited by memory bandwidth
switching via bus - CORRECT ANSWER - datagram moves via a shared bus, bus
contention (speed limited by bus bandwidth)
switching via crossbar - CORRECT ANSWER - overcome bus bandwidth, connect
processors to multiprocessors, parallel transmissions
output ports - CORRECT ANSWER - datagram buffer and queue, link layer protocol to
send, line termination
output port buffering - CORRECT ANSWER - required when datagrams arrive from
fabric faster than transmission rate. queuing and loss due to buffer overflow.
scheduling discipline - CORRECT ANSWER - choose among queued datagrams for
transmission
