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Networks II > Naming & Addressing IP Protocol > Flashcards

Naming & Addressing IP Protocol Flashcards

1
Q

What is name resolution?

A

The process of determining an address from a name

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2
Q

Why do we need both names and addresses?

A

Because names are human understandable but they waste space in packet headers and are hard to parse. Addresses are machine understandable and once fixed size is easy to carry in headers and parse. Indirection in the fact that multiple names may point to the same address which means you can move a machine and just update the resolution table. You do not have to change the hostname that people use.

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3
Q

What is the Domain Name System?

A

The phone book for the internet, it translates human readable hostnames into IP addresses.

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4
Q

What are characteristics of addressing?

A

Addresses need to be globally unique
And addresses and domain names are hierarchical

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5
Q

What is the command line tool to query DNS?

A

nslookup

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6
Q

Do telephone networks have names and addresses?

A

Telephone networks only have addresses

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7
Q

What does the ITU(International Telecommunication Union) do?

A

It assigns each country a unique country code

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8
Q

Why is it okay for telephone numbers to have variable length?

A

It is ok since they are only used in call establishment

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9
Q

Does an IP address refer to a host and if not why?

A

No an IP address does not refer to a host, it refers to the network interface. If a host has two network interface cards (NICs) it will have two IP addresses.

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10
Q

Does every host interface have its own IP address?

A

Yes

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11
Q

How many bytes are needed to address in internet? And what is the breakdown of these?

A

4 bytes in a 2 part hierarchy. This contains a network number and a host number with boundaries identified with a subnet mask which can aggregate addresses within subnets

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12
Q

What is the IP (internet protocol)?

A

This is a protocol used for communication data across a packet switched network.

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13
Q

What does the IP do?

A

It delivers a packet from the source to the destination solely based on its address.

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14
Q

What are features of IP?

A

Addressing
Routing
Connectionless service
Packetization
Best effort delivery (e.g. post office)
Used in a packet switched network

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15
Q

What is packetization?

A

This is the process of encapsulating data from an upper layer protocol into one or more packets.

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16
Q

What does IP not provide?

A

End to end data reliability & flow control (this is done by TCP or application layer protocols)
Sequencing of packets (like TCP)
Connection setup (it is connectionless)
Error reporting (ICMP Internet Control Message Protocol)

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17
Q

Can IP be used by itself if reliability is important?

A

No it must be paired with a reliable protocol such as TCP since it is in fact a best effort delivery service.

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18
Q

What is a real life example of a best effort delivery service?

A

The post office does its best to deliver mail however it doesn’t always succeed. If an unregistered letter is lost, it is up to the sender or would be recipient to discover the loss and fix the problem. The post office does not keep track of every letter and cannot notify a sender of loss or damage.

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19
Q

What does IP being a connectionless protocol for a packet switched network mean?

A

This means that each packet is handled independently and each packet can follow a different route to the destination. Packets sent by the same source to the same destination could arrive out of order. Some packets can be lost or corrupted during transmission.

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20
Q

What is the IP address?

A

It is a 32 bit identifier for host/router network interface

21
Q

How does a host get an IP address?

A

It is either hard-coded by the system admin in a file.

OR

It is dynamically assigned by the DHCP (Dynamic Host Configuration Protocol)

22
Q

How does the network get the network part of the IP address?

A

It gets allocated a portion of its provider ISP’s address space

23
Q

How does an ISP get a block of addresses?

A

Through the ICANN (Internet Corporation for Assigned Names and Numbers)

24
Q

What does the ICANN do?

A

It allocates addresses
Manages DNS
Assigns domain names, resolves disputes

25
Q

Every host has one unique IP address (true/false)?

A

False. The IP address is associated with the interface and not the host. Therefore a host with multiple NICs, routers would have multiple ip addresses.

26
Q

What is the interface?

A

This is the connection between the host/router and physical link

27
Q

What is classful addressing?

A

This is where you allocate address blocks on eight bit boundaries forcing 8, 16 or 24 bit network portions.

28
Q

What is a downside of using classful addressing?

A

It is the inefficient use of address space which causes address space exhaustion. E.g. class B is net allocated for 65k hosts even if only 2k hosts are in that network

29
Q

Is classful addressing still used today?

A

No it is obsolete in modern internet

30
Q

What is classless interdomain routing? (CIDR)

A

Network portion of address of arbitrary length. It’s address format is a.b.c.d/n where n is # bits in network portion of address.

31
Q

How are IP addresses represented within in a subnet mask?

A

The network part is assigned high order bits and the host part is assigned the low order bits

32
Q

What is a subnet?

A

A device interface with the same network part of an IP address

33
Q

What can a subnet do?

A

It can physically reach other subnets without intervening the router

34
Q

What is a subnet mask?

A

This is a screen of numbers used for routing traffic within a subnet.

35
Q

What are characteristics of a subnet mask?

A

It is a 32 bit number in which the n leftmost bits are 1s and 32-n rightmost bits are 0s

36
Q

What is the difference of the values of n in classful vs classless addressing?

A

In classful addressing n can must only be 8, 16, or 24. Whereas in classless addressing n can be any value from 0 to 32

37
Q

How do we define an address and its subnet mask or a block of addresses?

A

You give the address and the value of n preceded by a slash.

38
Q

How must the addresses within a block be defined?

A

They must be contiguous, one after another and the number of addresses within the block must be a power of 2

39
Q

Are subnet masks necessary?

A

Yes they are critical to communication on an IP network since the network devices use the packet’s Ip addresses and the subnet masks to determine if the destination is on a local subnet or on a remote network. This is because devices act differently depending on this result.

40
Q

What happens if the destination IP address is local?

A

The device will send an ARP request to retrieve the MAC address of the destination and use it

41
Q

What happens if the destination IP address is remote?

A

The device will send an ARP request to retrieve the MAC address of the gateway/router in it’s routing table and use that

42
Q

What does subnetting reduce?

A

It reduces the router table space

43
Q

What does ipconfig /all do?

A

It returns the IP address and MAC address for each NIC

44
Q

What is the ARP protocol?

A

The ARP protocol is a layer 2 protocol

45
Q

What is the process of ARP protocol if A wants to send packet to B and A knows B’s IP address but not their MAC address?

A

A broadcasts ARP query frame containing B’s IP
B receives the ARP frame replies to A with its MAC address
A caches IP to MAC address pair in its ARP table until it times out

46
Q

Why do we say ARP is plug and play?

A

Nodes create their ARP tables without intervention from network administrator

47
Q

What are the 4 cases ARP is used in?

A

The sender is a host and wants to send a packet to another host on the same network.

The sender is a host and wants to send a packet to a host on a different network.

The sender is router that has received a packet destined for a host on a different network.

The sender is a router that has received a packet destined for a host on the same network.

48
Q

What is the Dynamic Host Configuration Protocol?

A

The protocol used by networked computers to obtain IP addresses and other parameters such as subnet mask and default gateway and IP of DNS Servers. It ensures that all Ip addresses are unique meaning it also performs IP address pool management.

Networks II (7 decks)

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