lecture 2 - application - physical layers

client-server network

clients - network - server

5 layers of the internet model

1. Physical Layer

2. Data Link Layer

3. Network Layer

4. Transport Layer

5. Application Layer

PDU (protocol data unit)

A unit of data at any layer of the OSI model

HTTP (hypertext transfer protocol)

the protocol used for transmitting web pages over the Internet

IP (internet protocol)

Routing protocol that is in charge of forwarding packets on the Internet.

TCP (transmission control protocol)

connection-oriented, guaranteed-delivery

protocol used to send data packets between computers over a network like the Internet.

layer 1: physical layer

-signal transmission

-includes all hardware devices and physical media

-specifies the type of connection/electric signals that pass through

layer 2: data link layer

-message formatting and error correction

-controls physical layer

-decides when to transmit messages

layer 3: network layer

-message routing and addressing

-finds address of computer if it doesnt already know it

layer 4: transport layer

-connection management and message reassembly

-end-to-end connections

-detect lost messages and request they be resent

layer 5: application layer

-user access to the network

-user defines what messages sent over network

layer 2: data link layer - network standards

ethernet (LAN)

layer 3: network layer - network standards

IP (internet and LANs)

layer 4: transport layer - network standards

TCP (internet and LANs)

layer 5: application layer - network standards

HTTP, HTML (web)

importance of standards

-ensure that hardware and software produced by different vendors can work together

-provides customer options for vendors

application layer protocols

-SMTP (simple mail transfer protocol)

-IMAP (internet message access protocol)

-POP (post office protocol)

physical layer cables

- Twisted Pair (most common)

- Coaxial Cable

- Fiber Optic Cable (newest and most efficient)

3 types of addresses

-application layer (ex: web browser)

-network layer (ex: IP)

-data link layer (ex: ethernet)

5 domain names URLs

-EDU

-COM

-GOV

-MIL

-ORG

ICANN (internet corporation for assigned names and numbers)

non-profit organization responsible for managing the assignment of network and application layer addresses

domain name registration past

centralized and non-profit, only had to pay admin fee, too much for ICANN to handle

domain name registration present

commercialized, companies become registrar by applying to ICANN

IPv4

-routing traffic on the Internet, specifying "to" and "from" addresses

-4 bytes, 32 bits

media access control (MAC) address

A unique alphanumeric identifier that is assigned to each physical device on a network, 48-bit

What does DNS stand for?

Domain Name System

What is the primary function of DNS?

Translates human understandable domain names to machine understandable IP addresses

How does DNS improve performance?

By caching information along the way

nslookup command

issues a DNS request on device