Week 03 - Domain Name System & TCP/UDP (L06-L07) Flashcards
How does a TCP connection termination works?
- ESTABLISHED:
- FIN WAIT 1 (A):
- CLOSE WAIT (B):
- LAST ACK (B):
- TIME WAIT (A):
- CLOSED (B):
What is usage of Sequence Number in Reliable Transmission?
To resamble packets in the right order
What is a socket?
A pair of IP address + port
Explain the following record entries: A, AAA, C, MX, PTR, NS, SOA, SRV, TXT, NAPTR
- A: IPv4 records
- AAA: IPv6 records
- C: Canonical name (aliases)
- MX: points to mail server of the domain
- PTR: IP to domain name, NS: authorative name server of domain
- SOA: Start Of Authority, 1st record
- SRV: Service Location Record
- TXT: Text Records
- NAPTR: Name Authority Pointer Records
Explain difference between connection oriented and connectionless.
oriented: important that all packets arrive in the right order
connecitonless: best effort
What are four common connection issues?
- Delay
- Drops
- Packet lost
- wrong order
What is TCP?
Transport Control Protocol: establishes reliable comm. between A&B by error correct (retransmission, reassemble)
What is Delegation?
Is a concept of delegating DNS requests to other servers to avoid big loads on top level DNS servers
How is DNS hirachically organized?
Root - Top Level Domain - Domain - Sub-domains
How does a three-way handshake work?
- SYN: A sends SYN + his ISN to B
- SYN-ACK: Be sends ACK + his ISN to A
- ACK: A sends ACK to B. Connection established
What is DNS?
Domain Name System. Service for translating Domain names to IP addresses.
What is UDP?
Universal Datagram Protocol. Connectless. Works with best effort, doesnt care if packets are drop. Streaming, Voice, Video
What is ISN?
Initial Sequence Number; used in TCP
What is a default gateway?
If destination node of a packet is not in the same local network, the sending node sends packet to the default gateway. It’s kind of an exit point to another network. A default gateway can be a router or a firewall
Why are ports used?
To have multiple session on a single node.
