Network Layer
Sometimes abbreviated POTS, this is the original network that used humans as routers
What is the Plain Old Telephony System
These 16-bit identifiers are used in both TCP and UDP to find what socket a packet belongs to.
What is a port?
This network layer protocol for mapping addresses is broadcast over the data link layer by sending the packet an ethernet address that is all 1's
What is ARP
This command is commonly used to check if a host is alive. It uses a network layer level service.
What is ping
Sir. Tim Berners-Lee messed up this protocol (version) and set the networking field back decades.
What is HTTP/1.1
You can use different algorithms to dynamically calculate this such as Distance Vector Routing and Link State Routing.
What is a Forwarding Table? (Routing Table?)
This 1 bit TCP flag signifies that this 32 bit field is valid for this packet. During a normal connection, it will be set for all but the first packet.
What is an ACK?
This RARP replacement allows a single router to assign IP addresses to different devices on the local network.
What is the Dynamic Host Configuration Protocol (DHCP)?
This command is used to query DNS for reverse lookup mappings.
What is dig -x?
It is a best effort datagram protocol.
What is the Internet Protocol?
This class of IPv4 addresses starts with 1110 and is used for multicast.
What is IPv4 Class D
As opposed to a server and client which are found in the application layer, two communicating sockets can be distinguished from each other as these.
What are the active and passive openers?
.edu, .com, and .org are examples of this.
What is a top level domain?
This command is used for sending bytes to a specified host and port. It by default sends packets via TCP.
What is netcat (nc)?
Along with being lost, damaged, duplicated, and arbitrarily delayed, this is a bad thing that can happen to a good packet.
What is being reordered?
In hierarchical routing, these are seen as one destination from outside their network.
What is an autonomous system?
This only exists to calculate the checksum of a TCP or UDP header and is never actually sent over the network. It is comprised of two ip addresses, the protocol, the length, and the packet.
What is the TCP/UDP pseudoheader.
In a normal ARP response, all fields in the payload are the same except for this.
What is the destination physical address?
This combination of ss flags will show all TCP sockets and their corresponding ports.
This book is about the early internet and how it got started. A suggested read from Dr. Donahoo.
What is where wizards stay up late?
Along with the flags and fragmentation offset, this 16 bit field helps make sure that all pieces of a fragmented packet can be put back together at the endpoint.
What is the identification field (frag id)?
An active close socket will wait for twice of this before fully closing. In reality, Linux hard codes it to 60 seconds but we can pretend.
What is the Maximum Segment Lifetime (MSL)?
Along with the question, answers, and additional section that a DNS response provides, this section lists other name servers that may know the answer.
What is the authorities section?
This ip command is used to view the ARP cache.
What is ip ntable (ip n)
This is the name for how each layer stacks on top of each other as it is sent out, and is unpacked on the other side. It uses multiplexing and demultiplexing to do this and is the reason why it is so easy to write network applications now.
What is encapsulation?