TCP/IP model

Question 1

TCP/IP Model

Answer 1

▪ Also known as TCP/IP stack or the DoD Model
▪ Alternative to the OSI Model
▪ More relevant model for network designers since it’s based on TCP/IP
▪ Only a 4-layer mode

Question 2

NEtwork Interface (layer 1)

Answer 2

Physical and electrical characteristics
▪ Describes how to transmit bits across the network (1’s and 0’s)
▪ Determines how interface uses network medium
▪ Coaxial, Optical fiber, or Twisted-pair copper cabling
▪ Examples:
● Ethernet, Token Ring, FDDI, RS-232

Question 3

Internet (layer 2)

Answer 3

▪ Packages data into IP datagrams
● Contains source and destination IPs
● Forwards datagrams between hosts across the networks
▪ Routes IP datagrams across networks
▪ Connectivity occurs externally
▪ Examples:
● IP, ICMP, ARP, RARP

Question 4

Transport (Layer 3)

Answer 4

▪ Provides communication session management between hosts
▪ Defines level of service and status of connection used for transport
▪ Examples:
● TCP
● UDP
● RTP

Question 5

Application (Layer 4)

Answer 5

Defines TCP/IP application protocols
▪ Defines how programs interface with the transport layer service
▪ Layer with which the user interacts
▪ Examples:
● HTTP, TELNET, FTP, SNMP, DNS, SMTP, SSL, TLS, …

Question 6

Data Transfer over networks: Ports

Answer 6

Port numbers can be 0 to 65,535
▪ “Well-known” & Reserved Ports
● Ports 0 to 1023
▪ Ephemeral Ports
● Short-lived transport port that is automatically selected from a
predefined range
● Ports 1024 to 65,535

Question 7

Ipv4 Packets

Answer 7

▪ Source Address
● IP of sender
▪ Destination Address
● IP of receiver
▪ IP Flags
● Allows packet fragmentation
▪ Protocol
● Is this packet using TCP or UDP?