Intro to Comp Networks Exam 2 (Ch 3 - Ch 4)

rdt2.2

____________ has the same functionality as rdt2.1 but only uses ACKs, making it a NAK-free protocol.

rdt2.2

Duplicating ACK at sender results in the same action as NAK: it retransmits the current packet. Which protocol is sends ACK for last packet received OK instead of NAK?
- rdt2.1
- rdt2.2
- rdt3.0
- rdt2.3

both A and B

Underlying channels can also lose packets (data, ACKs). How does rdt3.0 handle lost sender-to-receiver data?
- sender waits "reasonable" amount of time for ACK
- both A and B
- retransmits if no ACK is received after waiting a certain amount of time
- restarts the entire channel and retransmits data for each ACK

01100101 10101110

Compute the Internet checksum value for these two 16-bit words:
11101011 01011111
01111010 01001110
What is the sum of these two 16 bit numbers?

10011010 01010001

Compute the Internet checksum value for these two 16-bit words:
11101011 01011111
01111010 01001110
What is the checksum of these two 16 bit numbers?

false
(TCP socket is identified by 4-tuple)

(T/F) UDP socket is identified by 4-tuple.

file transfer

Which of the following applications are not potential candidates to use UDP:
- File transfer
- Streaming multimedia apps
- DNS
- SNMP

logical communication

Transport services and protocols provide _________________ between application process running on different hosts

sender

Which transport protocol actions breaks the application messages into segments and passes it to the network layer?
- sender
- receiver
- hosts
- none of the above

receiver

Which transport protocol actions reassembles segments into messages and passes it to the application layer?
- end systems
- sender
- none of the above
- receiver

network

The ___________ layer is the logical communication between hosts.

hosts

The network layer is the logical communication between what?
- end systems
- hosts
- processes
- segments

transport

The ____________ layer is the logical communication between processes.

transport

Which layer is the logical communication between processes?
- network
- application
- link
- transport

handles data from multiple sockets, add transport layer

Multiplexing at sender...
- handles data from multiple sockets, add transport layer
- handles data from multiple headers, add transport layer
- handles segments from multiple sockets, add transport layer
- handles data from multiple sockets, add network layer

uses header info to deliver received segments to correct socket

Demultiplexing at receiver...
- uses socket info to deliver received segments to correct socket
- uses header info to deliver received segments to correct socket
- uses header info to deliver received messages to correct socket
- uses socket info to deliver received messages to correct address

to know where to send it back

Why does demultiplexing need the source port number?
- to carry one transport-layer segment
- to create a datagram
- to receive messages
- to know where to send it back

multiplexing

_______________ at sender handles data from multiple sockets and adds transport header.

demultiplexing

______________ at receiver uses header info to deliver received segments to correct socket.

both a and b

In order for demultiplexing to work, the host uses port numbers & IP address to direct segment to appropriate socket.
- IP address
- port numbers
- segment number
- both a and b

host-local

In connectionless demultiplexing, when creating a socket it must specify what kind of port number?
- IP
- host-global
- host-local
- destination

destination IP address and destination port number

In connectionless demultiplexing, when creating a datagram to send into the UDP socket, it must specify
- destination IP address and destination port number
- source IP address and source port number
- destination IP address and source port number
- source IP address and destination port number

true

(T/F) IP/UDP datagrams with the same destination port number but different source IP and/or source port numbers will be directed to the same socket at the receiving host.

4-tuple

In connection-oriented demultiplexing, the TCP socket is identified by ________________.

source IP address and port number, destination IP address and port number

The 4-tuple that is used to help identify a TCP consists of

false
(each socket is associated with a different connecting client)

(T/F) A server may support many simultaneous TCP sockets where each socket is identified by its own 4-tuple and each socket is associated with its own connecting client.

header field

Multiplexing and demultiplexing are based on segment and datagram ________________ values

destination port number

UDP demultiplexes using
- 4-tuple
- destination port number
- destination IP address
- none of the above

4-tuple

TCP demultiplexes using
- 4-tuple
- destination port number
- destination IP address
- none of the above

true

(T/F) Multiplexing/demultiplexing happens at all layers.

true

(T/F) UDP is connectionless and TCP is connection-oriented.

there's no connection establishment and therefore is faster, it's simple, can function in the face of congestion, it has no congestion control

Why is there a UDP? (Select multiple)
- there's no connection establishment and therefore is faster
- it's simple
- can function in the face of congestion
- it has no congestion control
- handshaking is used between the sender and receiver

true

(T/F) UDP is good to use with DNS because DNS wants the query result as fast as possible.

false
(complexity of reliable data transfer protocol DOES depend on characteristics of unreliable channel)

(T/F) Complexity of reliable data transfer protocol will not depend strongly on characteristics of unreliable channel.

all of the others

When a TCP segment arrives to a host, the socket to which the segment is directed depends on
- all of the others
- the source IP address of the datagram that encapsulated the segment
- the destination port number
- the source port number

none of the others

UDP has which of the following characteristics?
- connection state at the server
- three-way hand shake for connection establishment
- regulated send rate
- none of the others

Host A will retransmit neither segments

Over a TCP connection, suppose host A sends two segments to host B. Host B sends an acknowledgement for each segment, the first acknowledgement is lost, but the second acknowledgement arrives before the timer for the first segment expires.
- Host A will retransmit both segments
- Host A will retransmit the second segment
- Host A will retransmit the first segment
- Host A will retransmit neither segments

all of the others

Pipelining requires which of the following?
- transmitting many packets before receiving acknowledgements
- sender-side buffering of unacknowledged packets
- unique sequence numbers for each in-transit packet
- all of the others

true

(T/F) In the End-End congestion control approach, congestion is inferred from observed loss or delay.

false
(the size of the receiver's buffer never changes)

(T/F) The size of the TCP RcvWindow never changes throughout the duration of the connection.

false
(the sequence number of the subsequent segment depends on the number of 8-byte characters in the current segment)

(T/F) Host A is sending a large file to host B over a TCP connection. If the sequence number for a segment of this connection is m, then the sequence number for the subsequent segment will necessarily be m+1.

increases utilization

TCP uses pipelining to:
- none of the others
- increases utilization
- establish connections
- control congestion

segments

On the sending side, the transport layer converts the application-layer messages it receives from a sending application process into transport-layer packets, known as transport-layer ___________.

0010010100000110

What is the sum of these two 16 bit numbers?
10001011 01001110
10011001 10110111

1101101011111001

What is the checksum of these two 16 bit numbers?
10001011 01001110
10011001 10110111

183, 1118, 2053, 2988

1118, 2053, 2988, x

Consider the figure below in which a TCP sender and receiver communicate over a connection in which the sender->receiver segments may be lost. The TCP sender sends an initial window of 4 segments. Suppose the initial value of the sender->receiver sequence number is 183 and the first 4 segments each contain 935 bytes. The delay between the sender and receiver is 7 time units, and so the first segment arrives at the receiver at t=8. As shown in the figure below, 1 of the 4 segment(s) are lost between the segment and receiver.

What is the sequence numbers associated with each of the 4 segments sent by the sender?

Give the ACK numbers the receiver sends in response to each of the segments. If a segment never arrives, use 'x' to denote it.

5840

In the scenario below, the left and right clients communicate with a server using UDP sockets.

What is the source port # for packet D?

6075

In the scenario below, the left and right clients communicate with a server using UDP sockets.

What is the destination port # for packet D?

6075

In the scenario below, the left and right clients communicate with a server using UDP sockets.

What is the source port # for packet C?

5271

In the scenario below, the left and right clients communicate with a server using UDP sockets.

What is the destination port # for packet B?

forwarding, routing

Network-layer functions
___________: move packets from router's input link to appropriate router output link
____________: determine route taken by packets from source to destination

false
(forwarding moves packets from router's input link to appropriate router output link)

(T/F) One of the two network-layer functions of forwarding determines the route taken by packets from source to destination.

b) determines the route taken by packets from source to destination

One of the two network-layer functions of routing...
a) moves packets from router's input link to appropriate router output link
b) determines the route taken by packets from source to destination
c) determines the router's appropriate input link
d) none of the above

a) data plane and control plane

What are the two planes of the network layer?
a) data plane and control plane
b) local plane and network-wide plane
c) arrival plane and router plane
d) none of the above

local

The data plane of the network layer is ________, per-router function. It determines how the datagram arriving on router input port is forwarded to router output port.

True

(T/F) The data plane of the network layer determines how the datagram arriving on router input port is forwarded to router output port.

network-wide

The control plane of the network layer uses _____________ logic. It determines how datagrams are routed among routers along end-end path from source host to destination host.

False
(it determines how datagrams are routed among routers along end-end path from source host to destination host)

(T/F) The control plane of the network layer controls the flow of datagrams among routers along end-end path from source host to destination host.

c) traditional routing algorithms and software-defined networking (SDN)

What are the two control-plane approaches?
a) end-end routing algorithms and software development systems (SNS)
b) modern routing algorithms and domain name system (DNS)
c) traditional routing algorithms and software-defined networking (SDN)
d) none of the above

routers

One of the two control-plane approaches, traditional routing algorithms, is implemented in ___________.

(remote) servers

One of the two control-plane approaches, software-defined networking (SDN), is implemented in ___________.

a) in each and every router

In the per-router control plane, individual routing algorithm components _______________ interact in the control plane.
a) in each and every router
b) in a singular router
c) in a large database
d) none of the above

True

(T/F) In the software-defined networking (SDN) control plane, a remote controller computes and installs forwarding tables in routers.

a) successful datagram delivery to destination; c) timing or order of delivery; d) bandwidth available to end-end flow

Select what the Internet "best effort" service model has NO guarantees on: (select multiple)
a) successful datagram delivery to destination
b) guaranteed minimum of available bit rate
c) timing or order of delivery
d) bandwidth available to end-end flow
e) constant bit rate

routing, management control plane

_____________________ (software) operates in millisecond time frame.

forwarding data plane

_______________ (hardware) operates in nanosecond time frame.

routing processor

What is the missing part of this router architecture?

high-speed switching fabric

What is the missing part of this router architecture?

link layer

What is the missing function of these input port functions?

physical layer

What is the missing function of these input port functions?

decentralized switching

What is the missing function of these input port functions?

a) datagrams arrive faster than forwarding rate into switch fabric

Decentralized switching uses input port queueing which is if
a) datagrams arrive faster than forwarding rate into switch fabric
b) datagrams arrive slower than forwarding rate into switch fabric
c) datagrams arrive at the same time as the forwarding rate into switch fabric
d) none of the above

destination IP address

Destination-based forwarding is a forward based only on ______________________ (traditional).

header field values

Generalized forwarding is a forward based on any set of ___________________________.

longest address prefix

When looking for forwarding table entry for given destination address, use ___________________ that matches destination address.

interface 0

Which link interface should be used for the given destination address?

interface 1

Which link interface should be used for the given destination address?

content addressable

Retrieving an address in one clock cycle, regardless of table size, is known as ____________________.

True

(T/F) Longest prefix matching is often performed using ternary content addressable memories (TCAMs)

a) memory; c) bus; d) interconnection network

The tree major types of switching fabrics are: (select multiple)
a) memory
b) routers
c) bus
d) interconnection network
e) switcher

bus contention

When switching via bus, ______________ is the switching speed limited by bus bandwidth.

c) switching via interconnection network

Which switching method uses multistage switch, an n x n switch from multiple stages of smaller switches?
a) switching via bus
b) switching via memory
c) switching via interconnection network
d) none of the above

d) there is no queueing delay in the router

Suppose a router has n input ports each with identical line speeds, n output ports each with identical line speeds, and the line speed of an output port is at least n times as that of an input port. Further suppose that the switching fabric speed is at least n times as fast as an input line speed. Then
a) queueing can occur in an output port
b) queueing can occur in an input port
c) queueing can occur in the switching fabric
d) there is no queueing delay in the router

b) in the input ports and in the output ports

In a router, queueing can occur
a) only in the output ports
b) in the input ports and in the output ports
c) none of the others
d) only in the input ports

d) The sending IPv6 router creates an IPv6 datagram and puts it in the data field of an IPv4 datagram

Suppose one IPv6 routers wants to send a datagram to another IPv6 router, but are connected together by intervening IPv4 routers. If the two routers use tunneling, then
a) none of the others
b) The sending IPv6 router creates one or more IPv6 fragments, none of which is larger than the maximum size of an IPv4
c) The sending IPv6 router creates an IPv4 datagram and puts it in the data field of an IPv6 datagram
d) The sending IPv6 router creates an IPv6 datagram and puts it in the data field of an IPv4 datagram

true

(T/F) With a datagram network layer, each packet carries the address of the destination host

true

(T/F) The network portion of an IP address is the same for all the hosts on the same IP network.

b) could increase the end-end delay

Increasing the amount of per-hop buffer
a) could decrease the end-end delay
b) could increase the end-end delay
c) will not decrease packet loss
d) none of the others

true

(T/F) Multiple packets can be transferred by the switch fabric in parallel, as long as their output ports are different.

b) the transmission of packet A will not be interrupted. So, packet B has to wait after fully transmitting packet A

Assume packet A has begun transmission. If packet B (a high-priority packet) arrives during the transmission of packet A (a low-priority packet), then
a) packet B will be transmitted immediately while packet A is still being transmitted
b) the transmission of packet A will not be interrupted. So, packet B has to wait after fully transmitting packet A
c) the transmission of packet A will be interrupted to allow the transmission of packet B
d) transmission cannot be based on priorities

interface 6

Suppose a router uses longest-prefix matching, and has the following forwarding table:

Suppose a datagram arrives at the router, with destination address 01111111. To which interface will this datagram be forwarded?

10.0.1.13

Consider the scenario below:
Suppose that the host with IP address 10.0.1.13 sends an IP datagram destined to host 128.119.173.181. The source port is 3461, and the destination port is 80.

Consider the datagram at step 1, after it has been sent by the host but before it has reached the router. What is the source IP address for this datagram?

135.122.201.210

Consider the scenario below:
Suppose that the host with IP address 10.0.1.13 sends an IP datagram destined to host 128.119.173.181. The source port is 3461, and the destination port is 80.

Now consider the datagram at step 2, after it has been transmitted by the router. What is the source IP address for this datagram?

yes

Consider the scenario below:
Suppose that the host with IP address 10.0.1.13 sends an IP datagram destined to host 128.119.173.181. The source port is 3461, and the destination port is 80.

Will the source port (at step 2) have changed (from step 1)? Y/N

no

Consider the scenario below:
Suppose that the host with IP address 10.0.1.13 sends an IP datagram destined to host 128.119.173.181. The source port is 3461, and the destination port is 80.

Has a new entry been made in the router's NAT table (between step 3 and step 4)? Y/N

forwarding

Moving packets from a router's input link to appropriate router output link is called ______________.

32

In Internet protocol version 4, the IP address consists of ____________ bits.

128

In Internet protocol version 6, the IP address consists of ____________ bits.

b) none of the others

Network-layer service model provide guarantee(s) on:
a) bandwidth available to end-end flow
b) none of the others
c) delivery to destination
d) timing or order of delivery

buffering

Because datagrams might arrive from switch fabric faster than link transmission rate, ____________ is required at the output port.