(lecture 6) IP packets are also known as ___

IP datagrams

(lecture 6) Bytes in an IP packet are also known as

octets

(lecture 6) IP is a layer ___ protocol

3

(lecture 6) Time to Live (TTL) is?

How long before the packet is discarded

(lecture 6) IP addresses are divided into what 2 parts?

Network and Host

(lecture 6) IP Addresses are ___ bits

32

(lecture 6) Is today's internet classful or classless?

classless

(lecture 6) What are the available addresses? 131.94.0.0/16

131.94.x.x

(lecture 6) what are the available addresses? 68.45.160.0/19

68.45.160-191.x

(lecture 6) What are the available addresses? 199.45.64.0/18

199.45.64-127.x

(lecture 6) Network: The Host portion of the network address is filled with ___

0

(lecture 6) Network: The Host portion of the broadcast address is filled with ___

1

(lecture 6) What are the network and broadcast addresses? 131.94.133.12/16

Network: 131.94.0.0/16 Broadcast: 131.94.255.255

(lecture 6) What are the network and broadcast addresses? 68.45.167.245/19

Network: 68.45.160.0/19 Broadcast: 68.45.191.255

(lecture 6) What are the network and broadcast addresses? 199.45.78.199/18

Network: 199.45.64.0/18 Broadcast: 199.45.127.255

(lecture 6) How many /24 are in a /16?

2^(24-16) = 2 ^8 = 256 new subnets

(lecture 6) How many /26 are in a /22?

2^(26-22) = 2^4 = 16 subnets

(lecture 6) How many /28 are in /26?

2^(28-26) = 2^2 = 4 new subnets

(lecture 6) What is 127.0.0.0/8?

It is a loopback network where traffic loops back to the sender

(lecture 6) What is 255.255.255.255?

It is a non-directed broadcast address which will reach all hosts on the network.

(lecture 7) How do you calculate how many subnets can be created by increasing the netmask.

2 ^(y-x)

(lecture 7) 200.45.60.0/22 is 1 network with 2^10 hosts (1024). How do we get ? networks that can accommodate 50 hosts each?

by using a /26 subnet

(lecture 7) How many /26 subnets are in a /22 network?

2^(26-22) = 2^4 = 16 subnets

(lecture 9) What is ARP's job?

To take an IP address and find out which ethernet address is associated with it

(lecture 9) ARP is technically which layer?

It's technically a Layer 3 protocol but only works on the network it operates on.

(lecture 9) Are ARP requests routed?

No

(lecture 9) ARP can be considered a glue between which Layers?

Layers 2 and 3.

(lecture 9) If Station A needs to find the Ethernet address associated with station B's IP address, what steps must be done with ARP?

1. is the information in the ARP's cache? Yes: Create Ethernet frame and send it directly to B No: Go to step 2

2. Send out a broadcast ARP request asking all hosts what is the Ethernet address associated with B's IP address

3. Station B should send back an ARP reply to A with its Ethernet address

4. Station A puts B's information in the ARP cache

(lecture 8) When a router receives a packet, it follows what steps?

1. Is it one of my addresses? Yes: Process the packet No: Go to step 2

2. Is it on a network that I'm connected to? Yes: send the packet through the interface connected to that network No: go to step 3

3. Is it on a route in the Routing Table? Yes: send it to the next hop No: send it to the default route

(lecture 8) What is a Next Hop?

Next Hop is the address to a device that can get the data packet closer to its destination address.

(lecture 8) When the destination address does not match any entries in the routing table, where do we send it?

The default route

(lecture 8) What does every Routing Table need to operate on the internet?

A default route

(lecture 10) IP packets can be as large as ___ bytes.

65535

(lecture 10) What is IP Fragmentation?

Divide the IP packet into smaller pieces that will fit within the MTU of the Layer 2 frame being used

(lecture 10) When the total length is greater than the MTU of the underlying Layer 2 network, what is needed?

IP Fragmentation

(lecture 10) What are the two flags of IP Fragmentation?

DF - Don't Fragment

MF - More Fragments

(lecture 10) To find out the actual Fragment offset multiply this field by ___ to get the number of bytes.

8

(lecture 10) To know the value of the Fragment Offset field, divide by ___ if you have the offset in bytes.

8

(lecture 10) How do you determine how many fragments are needed?

Divide the (IP Packet Length – IP Header Size) by (MTU - IP Header size) and round up. (MTU – IP Header size) must be a multiple of 8. In other words, the size of the data fragment is bounded by 8 bytes

(lecture 10)
IP packet Length = 4096
MTU = 1500
IP Header Length = IHL field value x 4 = 5x4 = 20.
How many fragments are needed?

(4096 – 20) / (1500 – 20) = 4076 / 1480 = 2.75 = 3 fragments

(lecture 10) In IP Fragementation, initial data will be split into chunks of ____ bytes or less to fit within the MTU limits.

1480

(lecture 10) In IP Fragmentation, if any fragment is lost, what happens?

The reassembly will timeout and the entire packet will be dropped. All fragments will have to be sent again.

(lecture 10) Is IP Fragmentation TCP?

No, TCP is Layer 4.

(lecture 10) IP fragmentation happens when the IP packet is ___ than the MTU of the Layer 2 below

larger

(lecture 10) In IP Fragmentation, an IP packet is divided into smaller fragments, on a ___ byte boundary

8

(lecture 10) In IP Fragmentation, the receiver will start a ___ upon receiving a fragment.

Timer. If the timer expires and fragments have not arrived, it will drop the entire packet.

(lecture 10) MF bit and Fragment Offset (FO) field If MF = 1 and FO = 0

First Fragment

(lecture 10) MF bit and Fragment Offset (FO) field If MF = 1 and FO != 0

MIddle Fragment

(lecture 10) MF bit and Fragment Offset (FO) field If MF = 0 and FO != 0

Last Fragment

(lecture 10) MF bit and Fragment Offset (FO) field If MF = 0 and FO = 0

Not a fragment. Just a regular Packet.

(lecture 10) ICMP stands for?

Internet control Message Protocol

(lecture 10) ICMP is a Layer ___ protocol used to signal information about Layer ___ events.

4, 3

(lecture 10) ICMP is called an ___ signaling protocol

in-band

(lecture 10) What is ICMP useful for?

diagnostics about hosts and networks and routers.

(lecture 10) What is ICMP Type 3?

Destination unreachable message

(lecture 10) What is ICMP Type 5?

Redirect

(lecture 10) What is ICMP Type 8?

Echo Request (ping)

(lecture 10) What is ICMP Type 0?

Echo Reply (ping response)

(lecture 10) What is ICMP Type 11?

TTL Exceeded

(lecture 10) Traceroute program actually ___ the ICMP protocol to gather information about routes.

exploits

(lecture 10) How does Traceroute work?

Initially sends packets with TTL=1. When first hop sees a packet, it decrements TTL and sends back a TTL exceeded message. Traceroute writes down the information about this first hop and sends more packets, now with TTL=2. The first hop decrements the TTL=1. Second hop sends back TTL exceeded message. Traceroutes repeats this process, increasing the TTL and sending packets until the destination is reached

(lecture 11) How many available ports are there?

65535

(lecture 11) Which ports are reserved by the system and used for well known applications and protocols.

1-1023

(lecture 11) ports 1024-65535 are called ___ ports.

ephemeral

(lecture 11) UDP stands for?

User Datagram Protocol

(lecture 11) Multiplexing is provided by ___

UDP

(lecture 11) Does UDP guarantee delivery?

No

(lecture 11) For VOIP, streaming audio, or video it is best to use ___

UDP

(lecture 11) TCP stands for?

Transmission Control Protocol

(lecture 11) in TCP, ACK stands for?

Acknowledgement

(lecture 11) In TCP, a 3 way ___ establishes a connection and negotiates parameters

handshake

(lecture 11) IN TCP, active participant sends a ___ message to the passive participant

SYN

(lecture 11) In TCP, passive participant sends a ___ message to the active participant

SYN/ACK

(lecture 11) In TCP, during a 3 way handshake, devices negotiate a ___

receive window

(lecture 11) In TCP, a ___ is the maximum amount of data a device is willing to receive before having to send back an ACK message

window

(lecture 11) During a 3 way handshake, ___ ensures effective use of bandwidth so that ACKs are not needed for every segment

A window

(lecture 11) In TCP, what happens when data arrives out of order.

TCP will put it back together in order

(lecture 11) What are the 5 things that identify a connection or "Flow"

1. Protocol
2. Source Address
3. Source Port
4. Remote Address
5. Remote Port

(lecture 11) What is TCP Flow?

When a single network connection can be multiplexed into many flows that carry data separately to each application

(lecture 11) When servers listen, it's also known as?

Passive connection

(lecture 11) When clients connect, it's also know as?

Active connection

(lecture 12) DHCP stands for?

Dynamic Host Configuration Protocol

(lecture 12) DHCP hands out information such as?

1. IP Address
2. Netmask
3. Gateway
4. Host name
5. Lease Time
6. DNS servers

(lecture 12) Does DHCP work with UDP or TCP

UDP

(lecture 12) With the DHCP Discover Mesage (Client > Server) what is the SrcAddr and DstAddr?

SrcAddr: 0.0.0.0 DstAddr: 255.255.255.255

(lecture 12) How does the client maintain leased IP?

At 1/2 the lease time, client will make another request to the DHCP server

(lecture 12) What are the 3 private IP addresses?

10.0.0.0/8
172.16.0.0/12
192.168.0.0/16

(lecture 12) Can Private IP addresses be routed on the internet?

No

(lecture 13) What does DNS stand for?

Domain Name System

(lecture 13) What does DNS do?

In order to make it easier to find hosts on a network, a system was developed to associate a name to an IP address.

(lecture 13) In DNS, the first "." is the?

Root Zone

(lecture 13) In DNS, edu would be?

A top level domain server delegate to second level domain server

(lecture 13) In DNS, fiu would be?

Second level domain that may have a sub zone.

(lecture 13) In DNS, www would be?

The machine name

(lecture 13) DNS servers can be what 3 types?

Authoritative, Resolver, and Caching

(lecture 13) In a DNS record type: A means?

Address

(lecture 13) In a DNS record type: MX means?

Mail exchanger

(lecture 13) In a DNS record type: CNAME means?

(lecture 13) In a DNS record type: NS means?

Name server

(lecture 13) In a DNS record type: SOA means?

Start of Authroity

(lecture 13) In a DNS record type: PTR means?

Pointer (Reverse DNS - finding the name when you have the number)

(lecture 13) In DNS, what would happen if you were looking for www.cis.fiu.edu?

1. A Host crafts a DNS UDP packet asking for the A record of ww.cis.fiu.edu and sends it to port 53 of the configured DNS resolver.
2. Resolver sends NS query for the “edu.” top level domain to one of the Root Servers.
3. Root server replies with list of name servers for the edu. Zone.
4. Resolver sends another NS query to one of the servers in the reply of 3, now asking for fiu.edu.
5. It gets another list of servers. It then sends another NS query for cis.fiu.edu. To one of the servers in this list.
6. Resolver gets a list of name servers for cis.fiu.edu.
7. Resolver sends an A record query for www.cis.fiu.edu to one of the servers in 6.
8. Resolver receives an IP address as a response.
9. Resolver forwards the above response to the host that was asking for it in step 1.

(lecture 7) In a IP Packet, IHL stands for?

IP Header Length - Length of the IP header as a multiple of 4 bytes. If value is 5, then IP Header is 20bytes long.

(lecture 7) In a IP Packet, TOS stands for?

Type of Service - Usually 0. High throughput, high reliability, low cost

(lecture 7) In a IP Packet, TTL stands for?

Time to live - How long before this packet is discarded.