Chapter 7: TCP/IP Basics Flashcards
Protocol Stack
The software installed on a system that enables a specific protocol suite to function
Internet Protocol (IP)
Works at the Internet layer, taking data chunks from the Transport layer, adding addressing, and creating the final IP packet.
ICMP
Internet Control Message Protocol (ICMP) is an error reporting and diagnostic utility and is considered a required part of any IP implementation.
ping
- Command used to query if a host is reachable
- Shows the round trip time (RTT) for the ICMP packet it sends
What is the structure of a simple IP header?
version -> 32 bits (Header Length) -> DSCP -> TTL -> Protocol
Version field of an IP header
Defines the IP address type, i.e. 4 for IPv4 and 6 for IPv6
Header Length field of an IP header
The total size of the IP portion of the packet, which happens to be 32 bits
DSCP field of an IP header
- Differentiated Services Code Point
- Contains data used by bandwidth-sensitive applications
TTL field of an IP packet
- Time To Live
- A counter that decrements by one every time a packet goes through a router.
- Usually 128, can’t be higher than 256
Protocol field of an IP packet
Usually either TCP or UDP, and identifies what’s encapsulated inside the packet
What percentage of TCP/IP applications use TCP?
~95%
ACK/NACK
TCP’s communication rule that requires both the sending and receiving machines to acknowledge the other’s presence and readiness to send and receive data.
Port Number
Used by systems to determine what application needs the received data.
Structure of a simple TCP header
Source p# -> Dest p# -> Sequence # -> ACK
Sequence Number and ACK fields of a TCP header
Enable the sending and receiving computers to keep track of the various pieces of data.
Flags
An optional portion of a header that gives both sides detailed info about the state of the connection
Checksum
A portion of a TCP header that checks it for errors
Application Layer Protocols
Used by TCP/IP applications to move data back and forth between servers and clients
Universal MAC Address
FF-FF-FF-FF-FF-FF
In Windows -> ipconfig
In UNIX/Linux/OSX -> ifconfig
Provide lots of info regarding a system’s TCP/IP settings
Netword ID
The part of an IP address that every computer on a network starts with
Host ID
The part of an IP address that distinguishes each computer from each other