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CSCI 3171 > Chapter 4 > Flashcards

Chapter 4 Flashcards

1
Q

What is the primary role of routers?

A

Forward datagrams from input links to output links.

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2
Q

What layer manages packet forwarding?

A

Network

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3
Q

What layer manages packet routing?

A

Network

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4
Q

What is the packet forwarding process at a router?

A

When the packet arrives at a router’s input link, the must move the packet to the appropriate output link.

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5
Q

What is the packet routing process at the network layer?

A

Routing refers to the network-wide process that determines the end-to-end paths that packets take from source to destination.

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6
Q

What process is used to determine a packet’s route?

A

Routing algorithms.

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7
Q

What critical network layer component each router has?

A

Forwarding table.

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8
Q

At the network layer, what is guaranteed delivery?

A

This service guarantees that the packet will eventually arrive at its destination.

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9
Q

At the network layer, what is guaranteed delivery without bounded delay?

A

This service not only guarantees delivery of the packet, but delivery within a specified host-to-host delay bound (for example, within 100 msec).

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10
Q

At the network layer, what is in-order packet delivery?

A

This service guarantees that packets arrive at the desti- nation in the order that they were sent.

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11
Q

At the network layer, what is guaranteed minimal bandwidth?

A

This network-layer service emulates the behavior of a transmission link of a specified bit rate (for example, 1 Mbps) between send- ing and receiving hosts. As long as the sending host transmits bits (as part of packets) at a rate below the specified bit rate, then no packet is lost and each packet arrives within a pre-specified host-to-host delay (for example, within 40 msec).

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12
Q

At the network layer, what is maximum jitter?

A

This service guarantees that the amount of time between the transmission of two successive packets at the sender is equal to the amount of time between their receipt at the destination (or that this spacing changes by no more than some specified value).

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13
Q

At the network layer, what are security services?

A

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 then 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.

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14
Q

What is the single service offered by the Internet at the network layer? What does it guarantee?

A

Best-effort service - guarantees nothing

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15
Q

What are the three input processing steps?

A
  1. Line termination
  2. Data link processing (protocol decapsulation)
  3. Lookup, forwarding queueing

on to….

________________
Switch Fabric
________________

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16
Q

What is the name of a ‘network-layer packet’?

A

Datagram

17
Q

What is the size of an IPv4 address (bits)?

A

32 bits

18
Q

How many IPv4 addresses are available? (approx)

A

2^32 ~4 billion

19
Q

What is the interconnection of hosts to one router interface?

A

A subnet.

20
Q

What is a subnet mask?

A

It is an interconnection of hosts to a single router interface using the /24 notation.

Example:

223.1.1.0/24

The first leftmost 24 bits (223.3.1.1) are the subnet address

21
Q

What is the Internet’s address assignment strategy?

A

Classless Interdomain Routing (CIDR)

22
Q

What does NAT stand for?

A

Network address translation.

23
Q

What is the purpose of NAT?

A

Translate wide area network IPs to the private home address

Example:

138.23.122.3, 5001 –> 10.0.0.1. 3345

24
Q

Why is NAT controversial?

A

Because it uses port numbers to identify hosts within the home network, where ports (application layer) should only be used to identify processes (according to ‘purists’)

25
Q

What is an alternative solution to NAT’s controversy?

A

IPv6

26
Q

What is the bit size difference between IPv4 and IPv6?

A

IPv4: 32 bits
IPv6: 128 bits

IPv6 could assign an address to every grain of sand on the planet (according to the book)

27
Q

What are the major differentiators between IPv6 and IPv4?

A
  • Fragmentation and reassembly is deprecated in v6. If packet is too big, the router will send and error message
  • Removal of the checksum (Transport layer protocols do this - redundancy)
28
Q

Are IPv6-capable systems compatible with IPv4?

A

Yes

29
Q

Are IPv4-capable systems compatible with IPv6?

A

No

30
Q

What are the hardware solution to transitioning to IPv6 from IPv4?

A

Dual-stack nodes (handles both datagrams)

31
Q

What is an alternative to the dual-stack approach to transition from IPv4 to IPv6?

A

Tunnelling, taking the entire IPv6 datagram in an IPv4 datagram. The payload will eventually be recognized by next IPv6 node.

CSCI 3171 (4 decks)

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