Internet Layer and Protocol Flashcards

A set of 100 flashcards based on the Internet Layer lecture, covering IPv4, IPv6, NAT, and deployment statistics.

Internet Layer

The layer in the TCP/IP model responsible for internetworking, hiding routing from the Transport layer, and processing IP datagrams.

Internetworking

The concept of the Internet as a 'network of networks' with LANs at the edges served by routers in the core.

Packetisation

The process of dividing data into datagrams for transmission across the network.

Fragmentation

The process of breaking down packets into smaller units to fit the requirements of the physical network.

Fragment Reassembly

The process of reassembling fragmented packets back into their original form upon reception.

Packet-switched

A property of the Internet Protocol indicating it is connectionless.

Unreliable

An IP property meaning there is no guarantee that any given datagram will arrive.

Best effort basis

The principle by which packets are sent and routed without guarantees of delivery, speed, or quality.

Destination-routed

The standard routing method where routers use routing tables to determine the path based on the destination address.

Routing Table

A data table stored in a router used to determine the next hop for an IP packet.

Store-and-Forward

A packet switching method where a host (e.g., H1) sends a packet to the nearest router (e.g., B), which then passes it on toward its destination.

Quality of Service (QoS)

Methods used to prioritize certain traffic to help manage issues like packet drops or delays.

ICMP

Stands for Internet Control Message Protocol; used for diagnostics and control, such as the ping command.

ICMPv6

The version of the Internet Control Message Protocol used specifically for IPv6.

IPSEC

A protocol suite used for encryption and securing Internet Protocol communications.

IGMP

The Internet Group Management Protocol, which helps establish IPv4 multicast groups.

IPv4 Header Version

A 4-bit field in the IPv4 header used to indicate the protocol version being used.

IHL (Internet Header Length)

A field in the IPv4 header that specifies the length of the header in 32-bit words.

DSCP (Differentiated Services Code Point)

A field in the IPv4 header used for packet classification and quality of service.

ECN (Explicit Congestion Notification)

A field in the IPv4 header used for end-to-end notification of network congestion without dropping packets.

Total Length (IPv4)

A 16-bit field that defines the entire size of the IPv4 packet, including header and data, in bytes.

Identification (IPv4)

A field in the IPv4 header used to uniquely identify the fragments of a single datagram.

Flags (IPv4)

A 3-bit field used to control or identify fragments in the IPv4 header.

Fragment Offset (IPv4)

A field that specifies where in the original datagram a particular fragment belongs.

Time To Live (TTL)

A 8-bit field that prevents packets from circulating indefinitely by decrementing at each router.

Protocol (IPv4 Header)

A field that indicates the next level protocol used in the data portion of the IP datagram.

Header Checksum (IPv4)

A 16-bit field used for error-checking the header to ensure it has not been corrupted during transit.

Source IP Address (IPv4)

The 32-bit address of the originator of the IPv4 datagram.

Destination IP Address (IPv4)

The 32-bit address of the intended recipient of the IPv4 datagram.

Options (IPv4)

An optional field in the IPv4 header used if IHL is greater than $5$.

RIR

Stands for Regional Internet Registry, an organization that manages the allocation and registration of IP addresses.

APNIC

The RIR for the Asia Pacific area, which reached IPv4 exhaustion on $19/04/2011$.

RIPE NCC

The RIR for the EU, Middle East, and Central Asia, which reached IPv4 exhaustion on $14/09/2012$.

LACNIC

The RIR for Latin America & Caribbean, which reached IPv4 exhaustion on $10/06/2014$.

ARIN

The RIR for North America, which reached IPv4 exhaustion on $24/09/2015$.

AFRINIC

The RIR for Africa, which reached IPv4 exhaustion on $22/03/2020$.

NAT (Network Address Translation)

A method to share one public IPv4 address among multiple computers using private addresses.

RFC1918

The document that defines the private IPv4 address spaces such as $10.0.0.0/8$ and $192.168.0.0/16$.

10.0.0.0/8

One of the private address spaces defined by RFC1918.

192.168.0.0/16

A commonly used private address space defined by RFC1918 often used for home routers.

172.16.0.0/16

The address space listed in the notes as part of the RFC1918 private address ranges.

NAPT (Network Address Port Translation)

A mechanism that allows multiple devices on a LAN to be mapped to a single public IP address but breaks the end-to-end principle.

End-to-End Principle

A networking design framework that is broken by NAT and NAPT protocols.

Address Recycling

A market for buying and selling used IP address space, typically costing approximately $50$ per address.

IPv6 Header Version

A 4-bit field in the IPv6 header indicating the version is $6$.

Traffic Class (IPv6)

An 8-bit field used by the source and routers to identify and distinguish between different classes or priorities of IPv6 packets.

Flow Label (IPv6)

A 20-bit field used to tag sequences of packets that should be handled as a specific flow.

Payload Length (IPv6)

A 16-bit field indicating the size of the payload in octets, following the IPv6 header.

Next Header (IPv6)

A field that identifies the type of header immediately following the IPv6 header.

Hop Limit (IPv6)

An 8-bit field that specifies the maximum number of hops a packet can take, replacing the IPv4 TTL.

Source IP Address (IPv6)

The 128-bit address of the originator of the IPv6 packet.

Destination IP Address (IPv6)

The 128-bit address of the intended recipient of the IPv6 packet.

IPv6 Global Adoption (2024 General)

According to the comparison slide, global adoption is at approximately $45\text{\%}$.

IPv6 Adoption France (2024)

Google statistics report an IPv6 adoption rate of $75.45\text{\%}$ for France.

IPv6 Adoption Germany (2024)

Google statistics report an IPv6 adoption rate of $72.68\text{\%}$ for Germany.

IPv6 Adoption India (2024)

Google statistics report an IPv6 adoption rate of $70.22\text{\%}$ for India.

IPv6 Adoption UK (2024)

Google statistics report an IPv6 adoption rate of $43.81\text{\%}$ for the UK.

IPv6 Adoption USA (2024)

Google statistics report an IPv6 adoption rate of $49.83\text{\%}$ for the USA.

Facebook IPv6 Adoption (2025)

As of $27\text{ Jan }2025$, Facebook reported a global IPv6 adoption rate of $40.31\text{\%}$.

Facebook weekly growth (IPv6)

The weekly growth rate for IPv6 adoption reported by Facebook as of Jan 2025 is $0.46\text{\%}$.

Facebook monthly growth (IPv6)

The monthly growth rate for IPv6 adoption reported by Facebook as of Jan 2025 is $0.15\text{\%}$.

IPv6 Adoption India (Facebook 2025)

Facebook statistics show an adoption rate of $75\text{\%}$ in India.

IPv6 Adoption France (Facebook 2025)

Facebook statistics show an adoption rate of $65\text{\%}$ in France.

IPv6 Adoption Germany (Facebook 2025)

Facebook statistics show an adoption rate of $57\text{\%}$ in Germany.

IPv6 Adoption UK (Facebook 2025)

Facebook statistics show an adoption rate of $40\text{\%}$ in the UK.

IPv6 Adoption USA (Facebook 2025)

Facebook statistics show an adoption rate of $60\text{\%}$ in the USA.

IPv4 Death metaphors

Descriptions used in the slides include 'On borrowed time', 'Deadman walking', and 'Running on fumes'.

IoT (Internet of Things)

One of the new application types supported by the massive expansion of address space in IPv6.

Peering Wars

Business and technical conflicts between Tier-1 network providers that act as a barrier to IPv6 deployment.

CGNAT

Carrier-Grade NAT, often cited in myths as a reason why IPv6 might not be needed.

IPv6 Security Myth

The false belief that IPv6 is less secure without NAT; in reality, IPv6 still utilizes firewalls and ACLs.

Leading Os

Zeros at the start of an IPv6 block that can be omitted for address simplification.

Double colon (::)

A convention used to replace a single set of repeated 16-bit blocks of all zeros in an IPv6 address.

16-bit field constraint

In IPv6 address simplification, you cannot shorten a single 16-bit field of all zeros if it is not part of a '::' group.

fe80::/10

The prefix for Link-local addresses in IPv6, which are never routed.

Link-local address

An IPv6 address that every host always has per adapter, used for communication on the local link.

Global unicast address

IPv6 addresses starting with $2xxx$ or $3xxx$ ($2000::/3$).

ULA (Unique Local Address)

An IPv6 address range starting with $fc00::/7$, used for local communication.

IPv4 Addressing bits

IPv4 uses $32$-bit addressing.

IPv6 Addressing bits

IPv6 uses $128$-bit addressing.

IPv4 Header Fields Count

The IPv4 header consists of $13$ fields.

IPv6 Header Fields Count

The IPv6 header consists of $8$ fields.

IPv4 Header Size

The standard IPv4 header size is $20$ bytes.

IPv6 Header Size

The standard IPv6 header size is $40$ bytes.

Address per adapter (IPv4)

In IPv4, hosts usually have exactly one address per adapter.

Address per adapter (IPv6)

In IPv6, hosts typically have multiple addresses per adapter.

Fragmented routing

The state of routing in IPv4, contrasting with the simplified routing found in IPv6.

1970s tech

A description used for IPv4, highlighting that it is past its prime.

ARP

Address Resolution Protocol, a keyword for upcoming topics in Internet Layer $2$.

NDP

Neighbor Discovery Protocol, an IPv6 protocol used for discovering other nodes on the same link.

SLAAC

Stateless Address Autoconfiguration, a method used by IPv6 hosts to configure themselves without a server.

DHCP(v6)

The version of Dynamic Host Configuration Protocol used for IPv6 address and parameter assignment.

NPT

Network Prefix Translation, a routing topic mentioned for future study.

Traceroute

A routing protocol tool used to trace the path packets take across a network.

IPv6 Privacy Addresses

Addresses that hosts may pick for themselves over time to maintain anonymity and privacy.

MAC Table

A table polled from switches to help track which physical devices are connected to specific ports.

NAV

An open source network monitoring package used in ECS to account for device mappings.

ARP Table Polling

A method of tracking device accountability by mapping MAC addresses to IPv4/IPv6 addresses.

10/100Base-TX Ports (1-48)

The specific hardware ports listed on page $1$ of the lecture notes.

xkcd 128 bits

A reference to the IETF finding the right balance so that nanobots can only devour half the planet before running out of addresses.