OSI MODEL
(OPEN SYSTEMS INTERCONNECTION)
Application
Presentation
Session
Transport
Network
Data Link
Physical
APPLICATION LAYER
- Provides the interface between the software application on a system and the network.
- Provides access to the network for applications.
- PROTOCOL: HTTP, TELNET, FTP, SMTP, SSH
PRESENTATION LAYER
- The Presentation Layer is responsible for data translation and encoding.
- Encryption/Decryption and Compression/Decompression
- PROTOCOL: SSL, TLS
SESSION LAYER
- Synchronizes the data exchange between applications on separate devices.
- Responsible for establishing, management, and terminating connection between applications
- PROTOCOL: NetBIOS, L2TP
TRANSPORT LAYER
- End to end transfer of data across the network
- How data is transmitted, connection is established
- PROTOCOL: TCP (Transmission Control Protocol), UDP (User Datagram Protocol)
NETWORK LAYER
- Path determination and logical addressing to another network
- Routing protocol
- Routers function at this layer
- PROTOCOL: IP, OSPF (Open Shortest Path First)
DATA LINK LAYER
- Movement of data within a local network
- Switches function at this layer
- Physical to logical connection
- PROTOCOL: ARP/RARP (Address/Reverse Address Resolution Protocol), PPP (Point-to-Point Protocol)
PHYSICAL LAYER
- Hardware: The type of media used on the network, such as type of cable, type of connector, and pinout format for cables.
- Topology: The physical layer identifies the topology to be used in the network. Common topologies include ring, mesh, star, bus, and hybrid.
- Electrical Signal, Ethernet, Fiber
MESH TOPOLOGY
Mesh topology, is a collection of point-to-point links that connect every site to every other site.
ADVANTAGE: optimal routing, fault tolerant, easy to add new devices without network disruption
DISADVANTAGE: expensive, difficult to scale, complex implementation
RING TOPOLOGY
In a ring topology, data travels in a circular fashion from one computer to another on the network
ADVANTAGE: cable faults are easily located, moderately easy to install
DISADVANTAGE: network disruption when adding or removing devices
BUS TOPOLOGY
A bus topology uses a trunk or backbone to connect all the computers on the network
ADVANTAGE: cheap and easy to implement, less cable, no specialized network equipment
DISADVANTAGE: network disruption when adding or removing devices, a break in the cable prevents all systems from accessing the network, difficult to trouble shoot
STAR TOPOLOGY
The star topology is the most popular physical LAN topology in use today, with an Ethernet switch at the center of the star and unshielded twisted-pair cable (UTP) used to connect from the switch ports to clients
ADVANTAGE: easy to add new devices without network disruption, cable failure only affects a single user
DISADVANTAGE: requires more cable than other topologies, center of star is single point of failure
ENCAPSULATION
The upper layer places packaging around the message that describes the application used to generate the message. This is called the header. The package and header are then passed to the next layer down. Each layer completes its own required encapsulation operation.
APPLICATION = Data, TRANSPORT = Segment, NETWORK = Packet, DATA LINK = Frame, PHYSICAL = BITS
TCP/IP MODEL
- Application
- Transport
- Network
- Physical
OSI vs TCP/IP Model
Application / Presentation / Session = Application
Transport = Transport
Network = Internet
Data Link / Physical = Network Access
IPV4
- provides the unique, numerical IP addresses necessary for Internet-enabled devices to communicate
- 32 bit address
- X.X.X.X; Each ‘X’ is called an octet and all the four octets added together makes a 32bit address (IPv4 address)
IPV6
- unique, numerical IP addresses necessary for Internet-enabled devices to communicate
- 128-bit Internet addresses
- hexadecimal
SUBNET
- subdivision of an IP network
- dividing a network into smaller network sections
- Exclusiv
