CS 2204 Communications and Networking - Term 1, 2018-2019

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

discarding old or duplicate Link State Advertisements or None of the above

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

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

fragmentation

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

from half a minute to a few minutes

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

loopback address

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

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

pseudorandom sequences

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

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

the Internet backbone

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

the Shortest Path First algorithm

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

the header only

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

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

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

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

1000

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

12 microseconds

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

16

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

2.4 GHz and 5 GHz

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

8, 16, 24 respectively

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)

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

Advanced Encryption Standard (AES)

Wi-Fi designers can improve throughput through a variety of techniques, including:

All of the above [FIX_ME]

In 4B/5B encoding, some symbols are used for signaling rather than data. The following provide an example of these:

All of the above [Start, End, Reset]

Different VLANs can usually be connected together via:

An IP router

Which of the following IPv4 addresses is NOT a private address? A) 10.0.0.1 B) 24.4.202.93 C) 172.16.1.1 D) 192.168.11.12

B)

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

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

Bits

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

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

By the Ethernet card manufacturer

In the Internet, most packet losses are due to:

Congestion

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)

Manchester encoding is principally designed to

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

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

Entities

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

FALSE

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

FALSE

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

FALSE

True or False: According to Nyquist, a perfect (noiseless) channel has infinite transmission capacity.

FALSE

True or False: An IPv6 address has 2 times the number of bits compared to IPv4.

FALSE

True or False: IPv4 addresses are half the size of IPv6 addresses.

FALSE

True or False: IPv6 routers periodically send Router Advertisement (RA) packets to the IPv6 broadcast address.

FALSE

True or 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

True or False: Short Message Service (SMS) first became available on 3G mobile phones.

FALSE

True or 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

True or 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

True or False: The Internet Checksum is usually better than CRC at detecting transposition errors.

FALSE

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

FALSE

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

FALSE

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

FALSE

True or False: The subnet mask for an IPv4 147.126.16.0/20 subnet would be 255.255.224.0.

FALSE

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

FALSE

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

FALSE

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

FALSE

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

Fall back to flooding

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 of the following is not supported by IPv6?

LAN broadcast

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

Link State Routing

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

No checksum calculated

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

None [FIX_ME?]

Gigabit Ethernet 1000Base-T uses the following encoding:

PAM-5

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

Request For Comments (RFCs)

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

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

TRUE

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

TRUE

True or False: 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

True or False: At the LAN layer, traffic-engineering mechanisms are historically/generally limited.

TRUE

True or False: Bandwidth delay is more significant than propagation delay within a small LAN.

TRUE

True or False: Ethernet LAN-layer addresses are most often called MAC addresses.

TRUE

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

TRUE

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

TRUE

True or False: Fast Ethernet introduced the concept of full-duplex Ethernet which is entirely collision-free.

TRUE

True or False: 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

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

TRUE

True or False: IP is a best effort system; there are no IP-layer acknowledgments or retransmissions.

TRUE

True or False: IPv6's extension headers must be processed in order.

TRUE

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

TRUE

True or False: 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

True or False: 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

True or False: 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

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

TRUE

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

TRUE

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

TRUE

True or False: 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

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

TRUE

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

TRUE

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

TRUE

True or Fasle: 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

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

The Internet

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

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

broadcast