1.1 Ports and Protocols Flashcards
What is the ICMP protocol type?
answers “is there a computer with this IP?” at the internet layer of the IP stack
ping is an application that runs under ICMP. It will show RTT (round trip time) for the ICMP packet in seconds.
WHAT ARE THE INTERNET LAYER PROTOCOLS
IPv4
IPv6
ICMP
What does the internet layer do?
takes data chunks from the transport layer, adds addressing, creates the final IP packet. then it gives it to layer 2 to be encapsulated into a frame.
WHAT ARE THE TRANSPORT LAYER PROTOCOLS?
TCP
UDP
What does the transport layer do?
Is the communication connection-oriented or connectionless?
connection oriented matters for:
- arriving in the right order
- secure
- slower
connectionless
- doesn’t care if some bits are missing
- fast
95% of app protocols use TCP
Explain TCP
- uses ACK/NACK for the process of knowing if two machines are ready to send and receive data
- chops data into segments
- give segments a sequence number
- verify that all sent segments are received
- request missing segment if not received
source port listed first, then dest port
TCP header fields
- source port (FIRST)
- destination port
- sequence number
- ACK numbers
- flags
- checksum
WHAT ARE THE APPLICATION LAYER PROTOCOLS?
What is the TCP protocol type?
Transmission Control Protocol. A connection-oriented protocol.
95% of apps use TCP, which is why we call it the TCP/IP stack and not UDP/IP.
What is the UDP protocol type?
User Datagram Protocol. A connectionless protocol.
Use when there’s a lot of data that doesn’t need to be perfect or the systems are extremely close to each other and unlikely to have transmission issues.
VoIP calls can afford to drop some frames
It’s FAST
2 famous UDP protocols
DNS and DHCP
how many fields are in an IP packet?
14
What are the fields in the IP packet?
version: IPv4 or IPv6?
header length: e.g. 32 bits
DSCP differentiated services code point: data used by bandwidth sensitive apps like VoIP
TTL Time To Live: TTL prevents an IP packet from infinitely looping if there are issues.
protocol: nearly always TCP or UDP and IDs what’s inside the packet
