IP Flashcards
What happens if everyone sets their packets to the fastest service in Type of Service?
The service becomes ineffective as all packets are treated equally
Why are fragments not commonly used anymore?
Fragments are not commonly used anymore because they create security risks, such as enabling DDoS attacks and packet reassembly vulnerabilities, which attackers can exploit to bypass security measures or disrupt networks.
What happens if an attacker sends unfinished fragments repeatedly?
The system buffers indefinitely leading to a DDOS attack
What is fragmentation in IP?
Breaking large packets into smaller ones to fit the MTU
(MTU (Maximum Transmission Unit) is the largest size of a packet that can be sent over a network without needing fragmentation.)
Where does fragmentation happen?
At networks with smaller MTU sizes
Where does packet reassembly happen?
Only at at the destination host (e.g., the client or server receiving the data).
What happens if one fragment is lost?
The entire packet must be retransmitted
What does MTU stand for?
Maximum Transmission Unit
What is the primary issue with fragmentation?
It is inefficient and unreliable
Does IPv6 support fragmentation?
No IPv6 does not support fragmentation
What does TTL stand for in IP?
Time To Live
What happens when a packet’s TTL reaches zero?
The packet is discarded and an ICMP error is generated
What is the default initial TTL value?
Commonly 64 hops but varies by system
Does IP guarantee delivery of packets?
No IP does not guarantee delivery
Does IP provide sequencing for packets?
No IP does not provide sequencing.
(it treats each packet independently and does not ensure they arrive in order)
Sequencing and reassembly of packets are handled by higher-layer protocols like TCP.
Does IP ensure packet reliability?
No IP does not ensure reliability
How large are IPv4 addresses?
IPv4 addresses are 32 bits long
What is the role of the IP header checksum?
To detect accidental corruption in the header
Does the header checksum improve security?
No it does not improve security
What are the fields in the IP header measured in?
They are measured in bytes
What is the typical size of an IP header without options?
Twenty bytes
What is the purpose of the Version field in the IP header?
To specify the version of the protocol
What does the IHL field in the IP header represent?
The length of the header in 32-bit words (aka 4 bytes)
(Internet Header Length)
What happens if the IHL field is greater than five?
It indicates that options are present in the header
Why are IP options generally removed by firewalls?
They are insecure and largely obsolete
(IP options are insecure as they can bypass firewalls, exhaust resources, and exploit outdated features, making them a target for attacks.)
What is the purpose of the Type of Service field?
It is used for tagging packets based on priority or security
Is the Type of Service field widely used today?
No it is not widely used
What is the Total Length field in the IP header?
It specifies the total size of the packet in bytes
What is the Identification field used for?
To group fragments of the same packet together
What is the purpose of the More Fragments flag?
It indicates whether more fragments are expected
What is the Fragment Offset field?
It specifies the position of a fragment in the original packet
Why are fragments often dropped by firewalls?
Fragments are often dropped by firewalls because they lack enough information for security checks, making them harder to verify and increasing the risk of exploitation.
What is Path MTU Discovery?
A process to find the smallest MTU along a packet’s route
(MTU - maximum transmission unit)
How does Path MTU Discovery work?
It sends packets with the DF (don’t fragment) flag set.
If they get an error back with that packet, then it reduces size and tries again until it receives no error.
What happens if ICMP messages are blocked by firewalls?
Path MTU Discovery fails causing transmission issues
What does ICMP stand for?
Internet Control Message Protocol
What is the purpose of ICMP?
To send error and diagnostic messages
(Internet control message protocol)
What is an Echo Request in ICMP?
A message used for pinging another device
What is the role of Protocol Numbers in IP?
To identify the next layer protocol such as TCP or UDP
What is the protocol number for TCP?
Protocol number six (used in the IP header)
What is the protocol number for UDP?
Protocol number seventeen
What does the Source Address field in the IP header specify?
The address of the sender
What does the Destination Address field in the IP header specify?
The address of the receiver
What is RFC791?
The standard that defines IPv4
What is RFC1122?
A document providing implementation guidance for IPv4
What is the significance of the ARPANET?
It was the precursor to the modern internet
Why were IPv4 addresses limited to 32 bits?
Due to hardware limitations (constrained storage and processing power) and anticipated small network sizes
Why was classful addressing initially used?
It simplified routing for early hardware
What are Class A addresses?
Addresses where the first eight bits identify the network
What are Class B addresses?
Addresses where the first sixteen bits identify the network
Remaining 16 bits used for host allocations.
Provides a good network to host allocation balance.
What are Class C addresses?
Addresses where the first twenty-four bits identify the network
What are Class D addresses used for?
Multicast
What are Class E addresses reserved for?
Experimental purposes
What is CIDR?
Classless Interdomain Routing which replaced classful addressing
What is the benefit of CIDR?
It allows flexible allocation of address space
What does /24 mean in CIDR notation?
It means the first twenty-four bits represent the network
What is the private IP range for Class A?
10.0.0.0/8 - 10.255.255.255
The first 8 bits are fixed.
What is the private IP range for Class B?
One seventy-two dot sixteen dot zero dot zero slash twelve
What is the private IP range for Class C?
One ninety-two dot one sixty-eight dot zero dot zero slash sixteen
What is NAT?
Network Address Translation
What is the main reason IPv4 addresses are exhausted?
The rapid growth of the internet and devices
How many bits are IPv6 addresses?
IPv6 addresses are 128 bits long
What is the primary advantage of IPv6 over IPv4?
IPv6 provides a vastly larger address space
What does the Flow Label field in IPv6 do?
It groups related traffic to minimize delay
(Ex: realtime streaming)
What does the Hop Limit field in IPv6 represent?
The maximum number of hops a packet can take
What is the purpose of link-local addresses in IPv6?
They are used for communication only within a local network
What is the standard notation for IPv6 addresses?
Hexadecimal separated by colons
What does double colon in IPv6 addresses mean?
It represents consecutive zeros
How does IPv6 simplify routing compared to IPv4?
It reduces reliance on NAT and allows direct global addressing
How likely are we to run out of IPv6 addresses?
Extremely unlikely due to the enormous address space
What is the minimum MTU size for IPv6?
One thousand two hundred eighty bytes
What happens if IPv6 packets are too large for a link?
The source must adjust and resend smaller packets
What is the purpose of Neighbour Discovery Protocol in IPv6?
It replaces ARP for address resolution
What is the main goal of IPv6 adoption?
To address scalability and future growth of the internet
