18 - TCP/IP Stack: Intro and Physical Layer Flashcards
What is a Network?
Medium for communication between entities connected to it
Is the Internet a network?
It is a network of interconnected networks
What is a Host?
Computer connected to a network
What is a Protocol?
Description of a set of procedutes to follow when communicating
What is a Service?
It is a function useful to a user on a network
- Ex. e-mail uses the SMTP protocol
What is a Utility?
A tool used on a network
- Ex. ping utility - takes an IP address and sends an ICMP “echo request” packet to that address
What is Protocol Layering?
Complex communications systems composed of several simpler protocols
- Each protocol solves a distinct class of problems
- Provides a specific service each later only needs to know how to interact with the layers directly above/below it.
How is the TCP/IP Stack structured?
- Application
- Transport
- Network
- Data Link
- Physical
Describe the Application Layer
Deals with programs on different hosts that want to communicate.
User-program interaction + protocol
Examples:
- Hypertext Transer Protocol (HTTP) - Web pages
- Simple Mail Transfer Protocol (SMTP) - Email
- Domain Name System (DNS) - name resolution
- Secure Shell (SSH) - encrypted remote shell access
Describe the Transport Layer
Facilitates transfer of bytes from host to host by breaking up data into packets.
Breaks files into datagrams + provides addresses/port info + reconstitues packets on the other end.
Responsible for getting the data from process A to process B, since it creates the packed and assigns the addresses and port numbers.
Describe the Network Layer
Routes packets via internet from source to destination
The Internet Protocol (IP) is the most common Network layer protocol
IP makes no guarantees about packet delivery
Describe the Data Link Layer
Moves packets from one host to another within a network
Provides means to transfer packets (called frames) between hosts
Describe the Physical Layer
Actual infrastucture that facilitates communication (i.e. wires and radio waves)
Describe Encapsulation
Data from a higher layer are encapsulated inside a lower layer “wrapper”
Lower layer protocol “carries” higher layer data
- Only has to know which higher layer protocol to pass the data to
