CS 2204 Networking

What is the bandwidth delay to get 1500 bytes onto the wire for Gigabit Ethernet?

12 microseconds

The size of the UDP port field is:

16 bits

The IPv6 fixed header is twice the size of the IPv4 header, so it amounts to:

40 bytes

Fast (100 Mbps) Ethernet uses the following encoding:

4B/5B

The Open Shortest Path First (OSPF) protocol is an intra-domain routing protocol based on _______ routing.

link state

A link-state routing algorithm computes routes from the network map using:

the Shortest Path First algorithm

The HTTP Set-Cookie header is used by:

the web server

ATM packets are often called cells which are of the following size:

Fixed-size 53 bytes

In the IPv6 fixed header, the IPv4 header Time To Live (TTL) field has become the:

Hop Limit

Which HTTP header is used by the server to inform the client about how it agrees to use the persistent connection?

Keep-Alive

BGP implements policy through filtering rules which allow rejection of certain routes at three different stages. Which of the following is NOT one of those stages?

Route path optimization

Which information is found in the UDP header?

Source and Destination Port

The UDP 16-bit Internet checksum on the data can be disabled by setting the checksum field to:

all 0 bits

The mobile telephone has a removable chip with account information called ____ card.

Subscriber Identity Module (SIM)

The telephone system is tightly intertwined with (wide area) computer networks. The limiting factor for networking purposes turns out to be:

"the last mile" over which telephone customers connect

A common recommendation is to have no more than _____ hosts per LAN or VLAN

1000

Wi-Fi WPA2 uses the presumptively stronger encryption system called:

Advanced Encryption Standard (AES)

Question text Wi-Fi designers can improve throughput through a variety of techniques, including: a. Improved radio modulation techniques b. Improved error-correcting codes c. Increasing the channel width d. Allowing multiple spatial streams via multiple antennas e. All of the above

All of the above

Different VLANs can usually be connected together via:

An IP router

AMI (Alternate Mark Inversion) still has synchronization problems with long runs of 0-bits. The solution used on North American T1 lines (1.544 Mbps) is known as

B8ZS

Question text The physical layer is concerned with the transmission of _______ over the physical medium.

Bits

How is an Ethernet card (or network interface) assigned a unique MAC address?

By the Ethernet card manufacturer

The legacy mechanism for designating the IPv4 network and host address portions was to make the division according to the rst few bits. Which one of the following is not one of the resulting the IPv4 address classes?

Class E

In datagram switching, packets are addressed by destination. In virtual-circuit switching, packets are "addressed" by a connection ID. So, datagram switching and virtual-circuit switching are examples of:

Connectionless, connection-oriented services respectively

The term "frames" normally refers to data packets at which layer?

Data Link (e.g. Ethernet)

Which of the following is not a key element of a protocol

Entities

Path MTU is the smallest packet size which gets fragmented when sent along a path.

False

The TCP the Congestion Window is just another name for the receiver's Advertised Window.

False

The following protocol assumes that all the e-mail will remain on the server indefinitely in multiple mailboxes:

IMAP

showed that if the cut-o frequency is B Hz, the ltered signal can be reconstructed by making 2B samples. No more, no less.

Nyquist

A network cable lies in the ____________ layer.

Physical

TFTP prevents internal old duplicates simply by not allowing its 16-bit block numbers to wrap around; this is effective, but limits the maximum file size to:

about 32 MB

Home ADSL Internet access run over this type of cable (in most cases):

coaxial

IPv4 addresses are half the size of IPv6 addresses.

false

If a given IPv4 destination address matches the first k bits of one of the host's addresses (w.x.y.z/k), the destination is on the local LAN.

false

The subnet mask for an IPv4 147.126.16.0/20 subnet would be 255.255.224.0.

false

A possible Internet compatibility issue is that a packet is too large for a given network. IPv4 handles this by supporting:

fragmentation

Generally speaking, IPv6 addresses consist of a 64-bit network prefix (perhaps including subnet bits) followed by a 64-bit part called:

interface identifier

The checksum field in the IPv4 packet header is the "Internet checksum" applied to:

the header only

The TCP Persist Timer is used to poll when the window size is zero. This timer is used by:

the sender side

All else being equal, the data rate achievable with a radio signal is proportional to:

the width of the frequency band

The CIDR longest-match rule for choosing the routing table entry to be used means:

using the most specific matching prefix

If Wi-Fi error rates or collision rates are high, a sender can send a large packet as multiple fragments, each receiving its own link-layer ACK.

True

In Asynchronous Transfer Mode (ATM), there is no mechanism for physical (LAN) broadcast.

True

TCP adds its own checksum because data errors can be introduced within routers where Data Link Layer checksums do not protect.

True

The degeneration of a signal over distance on a network cable is called attenuation.

True

The documents that contain all the formal Internet protocol standards are referred to as:

Request For Comments (RFCs)

Distance-vector is the simplest routing-update algorithm and it is used by:

Routing Information Protocol

In terms of the TCP sequence and acknowledgment numbers, which of the following count as 1?

SYN and FIN, but not ACK

In most TCP implementations, data can be sent only after the 3-way handshake completes. Therefore, the delay before any data can be sent is:

1 RTT

Bluetooth is a low-power network; for many applications the working range is about:

10 m

Which one of the following IPv4 addresses can be used as a valid host IP address?

10.0.0.80/24

Category 5 UTP cable is often used in which networks?

100 Mbps Ethernet

What is the size of IPv6 addresses?

128 bits

In order to fix the slow-convergence problem, most flavors of the RIP protocol use a value of "infinity" set to:

16

In the Plain Old Telephone System (POTS), the local loop between customer and local central oce consists of:

2 wires

The TCP TIMEWAIT state is supposed to last for a time equal to:

2 x MSL (maximum segment lifetime)

What are the frequency bands used by Wi-Fi 802.11n?

2.4 GHz and 5 GHz

Wi-Fi uses one or both of the following 2 frequency bands:

2.4 GHz and 5 GHz

Which of the following IPv4 addresses is NOT a private address?

24.4.202.93

How many TCP segments are normally exchanged to complete a normal close (from the ESTABLISHED state)?

3

The number of bits in the network part of IPv4 class A, B, C addresses are:

8, 16, 24 respectively

The 2 types of DNS Resource Records used to encode the IPv4 and IPv6 addresses that correspond to the specified domain name are respectively:

A and AAAA

An example of distance-vector routing-update algorithms that eliminate routing loops is:

A and B Only a. Destination-Sequenced Distance Vector b. Enhanced Interior Gateway Routing Protocol

In 4B/5B encoding, some symbols are used for signaling rather than data. The following provide an example of these: Select one: a. START b. END c. RESET d. All of the above

All of the above

What is the functionality that TCP ports provide?

Allow communication with a specific process within the host

What is the functionality that UDP ports provide?

Allow communication with a specific process within the host

Which layer of the OSI model supplies services that allow users to interface with the network?

Application Layer

A DNS record which comes from a name resolver that manages the record and is thus always correct is called:

Authoritative Record

The job of handling exterior routing (that is handling exchange of routing information between Autonomous Systems) is done by the following protocol:

Border Gateway Protocol

In the Internet, most packet losses are due to:

Congestion

Which of the following message types is NOT a valid TFTP message type?

Connection request

IPv4 multicast addresses remain as the last remnant of the Class A/B/C/... scheme. Multicast addresses are class:

D

What is a possible effect of improperly applying a connector to a network cable?

Data transmitted through that cable may experience signal loss.

Manchester encoding is principally designed to

Ensure that a transition occurs in the centre of each bit period

From the TCP "ESTABLISHED" connection state, what is the next state after the application closes ("active close")?

FIN WAIT 1

If an Ethernet switch does not have an entry for a particular destination, it will:

Fall back to flooding

A TCP connection cannot remain idle for a long period of time without getting terminated by the OS.

False

A store-and-forward switch or router begins forwarding a packet before it has fully arrived.

False

ARP (Address Resolution Protocol) takes advantage of the existence of LAN-level multicast frames.

False

According to Nyquist, a perfect (noiseless) channel has infinite transmission capacity.

False

An IPv6 address has 2 times the number of bits compared to IPv4.

False

At least one MAC sublayer protocol guarantees reliable delivery.

False

Copper wires have lower attenuation compared to fiber optic cables.

False

Fully qualified domain names (FQDN) are case-sensitive.

False

IPv6 routers periodically send Router Advertisement (RA) packets to the IPv6 broadcast address.

False

If a web server receives the line below in an HTTP request, it is missing the desired web page and should send an error back. GET / HTTP/1.1

False

If an 8 KB block of data is sent as a single UDP send operation over Ethernet (without jumbo frames), IP fragmentation is just avoided.

False

If there is no LISTENING TCP socket at the host TCP port to which a SYN request is sent, the response is to ignore the SYN segment and send no reply.

False

In Stop-and-Wait, deadlock can be avoided by the sender side doing retransmit-on-timeout while the receiver does not do retransmissions.

False

In distance-vector routing, each node has a complete view of the network topology.

False

Internet Service Providers (ISPs) always connect to one another directly via high-speed links.

False

MD-5 and SHA-1 secure-hash codes are often used in network errordetection because they are very fast to compute.

False

Making the stack non-executable prevents stack buffer overflow attacks that place a shellcode on the stack and also prevents return-to-libc attacks.

False

Short Message Service (SMS) first became available on 3G mobile phones.

False

Since essentially all links on the Internet have link-layer checksums to protect against data corruption, TCP's own checksum is strictly speaking unnecessary.

False

Subnetting allows aggregation of IP address blocks in a way that is visible to the Internet backbone.

False

Suppose a Sun RPC read() request ends up executing twice. In between successive read() operations, the block of data is updated by another process. So different data is returned. This is failure of idempotence.

False

Switches are used to connect distant LANs whereas a Router is most often used to connect individual computers.

False

TCP is stream-oriented, meaning that the application can write very small or very large messages and the TCP layer will take care of preserving message boundaries on the wire.

False

The DNS protocol runs over UDP but cannot run over TCP

False

The DNS protocol runs over UDP but cannot run over TCP.

False

The IEEE 802.1Q 32-bit VLAN tag is required to be added to frames with source and destination ports on the same switch.

False

The IPv4 Time-to-Live (TTL) header field is incremented by 1 at each router; if it reaches 10, the packet is discarded.

False

The Internet Checksum is usually better than CRC at detecting transposition errors.

False

The Real-time Transport Protocol (RTP) is built on top of UDP because of its packet loss intolerance.

False

The Simple Mail Transfer Protocol (SMTP) is used to retrieve email messages from older email servers.

False

The TCP congestion window update strategy called "Additive Increase, Multiplicative Decrease" (AIMD) is used during the slow-start phase of TCP connections.

False

The popular USB (Universal Serial Bus) standard for connecting computer peripherals uses Manchester encoding.

False

The preferred Wi-Fi encryption standard is Wired-Equivalent Privacy, or WEP.

False

The terms "throughput" and "data rate" are considered to mean the same thing.

False

The terms URI and URL are related: URL is a more specific kind of URI.

False

To avoid stop-and-wait becoming a performance bottleneck, TFTP has an option to allow small window size sliding windows operation.

False

UDP (like TCP) avoids IP fragmentation by relying on the Path MTU Discovery mechanism.

False

UDP packets with spoofed source address are difficult to deliver to the application.

False

UDP ports are considered a shared namespace with TCP ports. Therefore, 2 processes cannot share the same port number even if one process is using UDP and the other is using TCP.

False

WEP Wi-Fi encryption is still considered very strong nowadays.

False

With IPv6, routers can use CIDR (Classless Internet Domain Routing) but must base forwarding decisions on prefixes longer than /64.

False

Without a network connection (no Wi-Fi, no Ethernet, etc.), it is not possible for 2 apps on the same computer to communicate with each other via IP.

False

baud rate = bit rate / N, where N is the number of bits represented by each signal shift.

False

Ethernet switches have incorporated a switch-to-switch protocol to construct a subset of the switch-connections graph that has no loops and yet allows reachability of every host. This protocol is called:

Spanning Tree

What version of IP is the most common in the world?

IPv4

What is the purpose of the preamble in an Ethernet frame?

It is used for timing synchronization with alternating patterns of ones and zeros

Which of the following is not supported by IPv6?

LAN broadcast

What OSI layer identifies the communicating applications?

Layer 4

What kind of routing-update algorithm is a preferred choice for networks such as those of ISPs?

Link State Routing

A TCP connection is defined by the combination of the following:

Local <IP address, port> and remote <IP address, port>

Because of the inability to detect collisions directly, the Wi-Fi protocol has link-layer ____ packets for unicast transmission.

NACK

Which application made the greatest use of early Remote Procedure Call?

Network File System

For the Internet Checksum, the value 0000 in the checksum represents:

No checksum calculated

Wi-Fi Link-Layer ACKs contain the following information:

None

Gigabit Ethernet 1000Base-T uses the following encoding:

PAM-5

A protocol that allows mail users agents to copy email from the email server to the user is:

POP3

The general term for the Protocol Data Unit (PDU) used at the TCP layer is:

Packet

A traditional, land line, telephone network is typically a _______________ network.

Packet Switched

The following TCP segment can be sent by either side at any time to abort the TCP connection:

RST

A virtual private network, or VPN, supports creation of virtual links that join far-flung nodes via:

The Internet

A DNS query issued via IPv4 can only return IPv4 addresses, IPv6 addresses can only be returned if the DNS query is done via IPv6.

True

A TCP receiver can shrink the advertised window size to 0, so that the sender must stop sending data.

True

A VLAN looks like a single LAN and all VLAN members will see broadcast packets sent by other members.

True

ATM Adaptation Layer AAL 5 uses a CRC-32 checksum and is able to detect lost ATM cells.

True

All Ethernet devices also agree on a broadcast address of all 1's: a packet sent to the broadcast address will be delivered to all attached hosts.

True

At the LAN layer, traffic-engineering mechanisms are historically/generally limited.

True

BGP speakers exchange with neighbors only the routes they (and thus their AS) use themselves.

True

Bandwidth delay is more significant than propagation delay within a small LAN.

True

Ethernet LAN-layer addresses are most often called MAC addresses.

True

Ethernet switches have an additional privacy advantage in that traffic does not flow where it does not need to flow.

True

Ethernet-like collision detection is no longer feasible over radio communications:

True

Fast Ethernet introduced the concept of full-duplex Ethernet which is entirely collision-free.

True

For long (multi-kilometer) electrical serial lines, in addition to the clock-related serial-line requirements, we also want the average voltage to be zero.

True

Gigabit Ethernet slot time is largely irrelevant, as full-duplex (bidirectional) operation is almost always supported.

True

HTTP 1.1 supports persistent TCP connections. A persistent connection is a TCP connection over which a client may send several HTTP requests.

True

HTTP is stateless protocol, i.e. the behavior of a request does not depend on previous requests.

True

IMAP assumes that all the e-mail will remain on the server inde nitely in multiple mailboxes.

True

IPv6's extension headers must be processed in order.

True

IPv6's link-local addresses are intended to be used only within a LAN and never routed.

True

In Manchester Encoding, a 0 bit is indicated by the absence of a transition, and a 1 bit is indicated by the presence of a transition.

True

In Wi-Fi, after a collision is presumed to have occurred when the link-layer ACK is not received, there is an exponential-backo mechanism similar to Ethernet's.

True

In a baseband transmission, the entire bandwidth of the cable is consumed by a single signal. In broadband transmission, signals are sent on multiple frequencies, allowing multiple signals to be sent simultaneously.

True

In link-state routing implementations, link-state records must be periodically renewed.

True

In link-state routing, each node keeps a maximum amount of network information about of all nodes and all links.

True

In the context of Sun RPC's at-least-once semantics, duplicate request execution is a possibility.

True

In the context of data networking, a protocol is a formal set of rules and conventions that governs how computers exchange information over a network medium. A protocol implements the functions of one or more of the OSI layers.

True

In the context of data rates, one megabit per second (Mbps) is 1000000 bits per second.

True

In unswitched Ethernets, every packet is received by every host and it is up to the network card in each host to determine if the arriving packet is addressed to that host.

True

No matter the available bandwidth, every TCP connection must go through the slow-start phase.

True

One thing DNS makes possible is changing a website's IP address while leaving the fully qualified domain name (FQDN) alone.

True

Overlapping TCP segments raises the possibility of signature-based detection evasion (the attacker might arrange the packets so that the detection reassembles them one way and the target another way).

True

Routers are used to connect two computers that use dierent connection-oriented transport protocols.

True

Routers have the option of fallback-to-flooding for unknown destinations (i.e. those which are not in their routing table).

True

Sliding Windows can work even if the receiver assumes that the window size is much less than the sender's window size value.

True

Starting from the TCP ESTABLISHED state, the side that closes the connection first (active CLOSE) will end up in the TIME WAIT state.

True

The HTTP Content-Type header value used for HTML pages is text/html.

True

The Internet protocols use big-endian byte order (also referred to as network byte order).

True

The Split Horizon fix to the slow-convergence problem prevents all linear routing loops.

True

The Wi-Fi 5 GHz band (vs. 2.4 GHz) has increased ability to penetrate walls, often resulting in a higher effective range.

True

The essence of DNS is a hierarchical domain-based naming scheme and a distributed database system for implementing this naming scheme.

True

The most common binary data encoding on the Internet - at least below the application layer - is big-endian encoding.

True

The network layer interacts with the Wi-Fi LAN exactly as it does with Ethernet; no changes are required.

True

The reverse address resolution protocol (RARP) allows a host to discover its Internet address when it knows only its physical address.

True

The terms autonomous system (AS) and routing domain are used to refer to a set of routers under common administration, using a common link-cost assignment.

True

To restart the flow after packet loss, TCP uses threshold slow start which transitions to congestion avoidance.

True

Token Ring LAN is a simple multiple-access mechanism that is not only collision-free, but which supports fairness in the sense that if N stations wish to send then each will receive 1/N of the opportunities.

True

UDP is sometimes the protocol of choice for ooding attacks on the Internet because it is easy to send UDP packets with spoofed source address.

True

UDP is used by the Remote Procedure Call (RPC) protocol.

True

Wi-Fi MAC (physical) addresses have the same 48-bit size as Ethernets and the same internal structure.

True

What is the fundamental alternative to datagram stateless forwarding?

Virtual circuits

Baseband transmission may be defined as the transmission of a signal over a link:

Without any change in frequency

Most network intrusion-detection systems (NIDS) detect intrusions based either on traffic anomalies or on pattern-based signatures. Which of the following would fall under "traffic anomalies"?

a. pings directed to non-existent hosts b. TCP connection attempts targeting many different ports c. a large number of ping requests d. all of the above

The Border Gateway Protocol's primary goal is to provide support for choosing routes based on:

administrative input

If an IPv4 address has all 1-bits for the host bits, it is of type:

broadcast

How does a DNS client match the received answer with the question that it has sent?

by the client chosen Id header value which is returned in the response

HDLC (High-level Data Link Control) supports the following method(s) for frame separation:

byte stuffing over asynchronous links, bit stuffing over synchronous links

ATM's small packets (53 bytes) are called ________ and they are forwarded using ________ routing.

cells, virtual-circuit

When no other route to the destination exists, what does a host use to access a host outside of the local network?

default route

A TCP socket application can use setsockopt() with the TCP_NODELAY flag to:

disable the TCP Nagle algorithm for the connection in question

The link-state flooding algorithm avoids the usual problems of broadcast in the presence of loops by:

discarding old or duplicate Link State Advertisements

The Routing Information Protocol (RIP) is an intra-domain routing protocol based on _________ routing

distance vector

If the IPv4 "Don't Fragment" (DF header flag) is set to 1 by the sender, then a router must not fragment the packet and must _____ instead.

drop it

Two things are gained from station "A " doing gratuitous ARP on starting up: first, all stations that had A in their cache are now updated with A's most current LAN address, and second:

duplicate IP address may be detected

The usual approach to prevent eavesdropping on a communication channel is the use of:

encryption

What is the primary reason for the development of IPv6?

expanded addressing capabilities

Bluetooth uses a radio technology called:

frequency hopping spread spectrum

ARP-cache entries eventually expire and the timeout interval is on the order of:

from half a minute to a few minutes

Which of the following is a characteristic of single-mode fiber-optic cable?

generally uses semiconductor lasers as the light source

What makes UDP into a proper transport protocol?

it supports IPv4 and IPv6 addressing

What is the primary reason for the eventual retirement of IPv4?

limited addressing capabilities

The IPv6 address ::1 (i.e. 127 0-bits followed by a 1-bit) is called the:

loopback address

Which is an important characteristic of UDP?

minimal delays in data delivery

IPv4 class D addresses are used for:

multicast traffic

An essential feature of IPv4 (and IPv6) addresses is that they can be divided into 2 parts:

network part and host part

Linux systems support assigning to an unprivileged process any of several "capabilities". One of these is CAP_NET_BIND_SERVICE which allows the following:

opening ("binding" to) a privileged port

In Sliding Windows, once a full timeout has occurred, there are usually no packets remaining in flight and this is referred to as:

pipeline drain

An attack that keeps changing in relatively trivial ways to avoid signature-based detection is sometimes said to be:

polymorphic

The use of _________ lets the base station receive CDMA messages from unsynchronized mobile phones.

pseudorandom sequences

In Sliding Windows, if a sender chooses window size larger than the bandwidth x RTT product, then the RTT simply grows until the bandwidth x RTT matches the chosen window size. RTT increase is due to:

queueing delays

In bridged LANs, the _______ algorithm creates a topology in which each LAN can be reached from any other LAN through one path only.

spanning tree

What enables an Internet site to appear to the outside world as a single IP network, but further IP-layer routing to be supported inside the site?

subnets

In TCP's congestion avoidance phase, the Congestion Window adjustment rule introduced by TCP Tahoe says that, after packet loss has been detected:

the Congestion Window is cut by half

CIDR has essentially eliminated the IPv4 Class A/B/C mechanism from the:

the Internet backbone

Which field of the IPv4 packet header contains a value to identify the contents of the packet body?

the Options Field

If the TFTP client changes its port number on a subsequent connection, but the server does not, what prevents an old duplicate data packet sent by the server from being accepted by the new client?

the old dup packet has the wrong client UDP port number

What characteristic of UTP cable helps reduce the effects of interference?

the twisting of the wires in the cable

In the C language, a stack buffer overflow is not detected at the time it occurs because:

there is no array bounds checking at run-time

What is the primary purpose of ARP?

to resolve IPv4 addresses to MAC addresses

Which statement describes the purpose of a default route?

to transfer data to a host outside the local network when no other route to the destination exists.

When a packet is to be sent via a VPN, it is encrypted, encapsulated and sent along the normal Internet connection to the VPN server. This process is called:

tunneling

In Sliding Windows, the sender is allowed to send up to this many packets (starting with the next packet after the last acknowledged packet):

window size

TCP's congestion management is

window-based