NETWORKING FINAL EXAM QUESTIONS
WITH COMPLETE ANSWERS
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
, Buffering Equation - Answer-Old: RTT * C
New: (RTT * C) / sqrt(N)
Head-of-Line Blocking - Answer-Data that is not at the front of the queue can't move
through the fabric because data in front of it is waiting to move
Ideal Rate of Fabric - Answer-(# of lines)*(Transmission rate per line)
Network Layer functions - Answer-Routing protocols, IP protocol, ICMP protocol
IP Fragmentation - Answer-Header takes up 20 byes
Offset = Data Chunk start byte / 8
IP Address Bit Format - Answer-Higher order bits identify network. Lower order bits
identify interface
Classful addressing - Answer-IPs are divided differently depending on the range that
they fall within. (Class A: 1-byte network .... Class D: 4-byte network)
CIDR (Classless Interdomain routing) - Answer-Network portion of address of arbitrary
length. Address format a.b.c.d/x where x is # bits in network portion of address
DHCP - Answer-- Host broadcasts "DHCP discover" msg
- DHCP server responds with "DHCP offer" msg
- Host requests IP address: "DHCP request" msg
- DHCP server sends address: "DHCP ack" msg
- DHCP can send system configuration data too
NAT (Network address Translation) - Answer-The process of translating your public IP
address to your private network address
ICMP (Internet Control Message Protocol) - Answer-Protocol for network level errors
Duel Stack - Answer-Some routers can translate between formats
Tunneling - Answer-IPV6 carried as payload in IPv4 datagram among IPv4 routers
ICANN (Internet Corpoation for Assigned Names and Numbers) - Answer-Manages
DNS, allocates IP addresses, assigns domain names, resolves disputes
Distance Vector Routing Algorithm - Answer-Each node has a distance table that
displays the cost to a node via other nodes as next hop. Distance table yields routing
table by assigning the least cost path to the outgoing link
WITH COMPLETE ANSWERS
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
, Buffering Equation - Answer-Old: RTT * C
New: (RTT * C) / sqrt(N)
Head-of-Line Blocking - Answer-Data that is not at the front of the queue can't move
through the fabric because data in front of it is waiting to move
Ideal Rate of Fabric - Answer-(# of lines)*(Transmission rate per line)
Network Layer functions - Answer-Routing protocols, IP protocol, ICMP protocol
IP Fragmentation - Answer-Header takes up 20 byes
Offset = Data Chunk start byte / 8
IP Address Bit Format - Answer-Higher order bits identify network. Lower order bits
identify interface
Classful addressing - Answer-IPs are divided differently depending on the range that
they fall within. (Class A: 1-byte network .... Class D: 4-byte network)
CIDR (Classless Interdomain routing) - Answer-Network portion of address of arbitrary
length. Address format a.b.c.d/x where x is # bits in network portion of address
DHCP - Answer-- Host broadcasts "DHCP discover" msg
- DHCP server responds with "DHCP offer" msg
- Host requests IP address: "DHCP request" msg
- DHCP server sends address: "DHCP ack" msg
- DHCP can send system configuration data too
NAT (Network address Translation) - Answer-The process of translating your public IP
address to your private network address
ICMP (Internet Control Message Protocol) - Answer-Protocol for network level errors
Duel Stack - Answer-Some routers can translate between formats
Tunneling - Answer-IPV6 carried as payload in IPv4 datagram among IPv4 routers
ICANN (Internet Corpoation for Assigned Names and Numbers) - Answer-Manages
DNS, allocates IP addresses, assigns domain names, resolves disputes
Distance Vector Routing Algorithm - Answer-Each node has a distance table that
displays the cost to a node via other nodes as next hop. Distance table yields routing
table by assigning the least cost path to the outgoing link
