1. Network Fundamentals Flashcards
(30 cards)
Open Systems Interconnection Reference Model (OSI)
a universal language for computer networking. It’s based on the concept of splitting up a communication system into seven abstract layers, each one stacked upon the last. 1. Physical 2. Data 3. Networking 4. Transport 5. Session 6. Presentation 7. Application
Layer 1 - Physical Layer
The physical layer defines the means of transmitting raw bits rather than logical data packets over a physical link connecting network nodes. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium.
Layer 2 - Data Link
The data link layer is concerned with local delivery of frames between devices on the same LAN. Data-link frames, as these protocol data units are called, do not cross the boundaries of a local network.
Layer 3 - Network Layer
The main tasks of the network layer is one of providing cross-network addresses, the routing and the construction and updating of routing tables and the fragmentation of data packets.
Layer 4 - Transportation Layer
Layer 4 of the OSI model, also known as the transport layer, manages network traffic between hosts and end systems to ensure complete data transfers. Transport-layer protocols such as TCP, UDP, DCCP, and SCTP are used to control the volume of data, where it is sent, and at what rate.
Layer 5 - Session
The session layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e., a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. Session-layer services are commonly used in application environments that make use of remote procedure calls (RPCs).
Layer 6 - Presentation
The presentation layer is responsible for the delivery and formatting of information to the application layer for further processing or display. The presentation layer is the lowest layer at which application programmers consider data structure and presentation, instead of simply sending data in the form of datagrams or packets between hosts.
Layer 7 - Application
provides functionalities and services that user-facing software applications use to present data. If an application is like a house, then layer 7 is the foundation, not the house itself.
TCP FLAG - SYN
Synchronize sequence numbers
TCP FLAG - PSH
Push the data to the application without buffering
TCP FLAG - RST
Reset the connection
TCP FLAG - FIN
Last packet from the sender
TCP Header
Describes or identifies the payload. Contains TCP flags which act as control information.
Maximum Transmission Unit (MTU)
Maximum IP packet to transmit
Star Topology
Hub and spoke. All devices connected to a central device. Switched ethernet network. Used in large and small organizations.
Ring Topology
Network configuration where device connections create a circular data path. Each networked device is connected to two others, like points on a circle. In a ring network, packets of data travel from one device to the next until they reach their destination.
Bus Topology
type of network topology in which all devices in the network are connected by one single RJ-45 cable. The cable is referred to as the bus. More devices slow down the network. If it breaks somewhere whole network goes down or split in two.
Mesh
a network setup where each computer and network device is interconnected with one another. Commonly used for wireless networks. Allows for most transmissions to be distributed even if one of the connections goes down.
Hybrid
A combination of one or more physical topologies. Most networks are hybrid.
Wireless Topologies
All devices communicate through an access point. Ad hoc devices work together to form a “mesh” cloud
Peer to peer topology
All devices are both clients and servers. Everyone talks to everyone. Difficult to administer and secure. Easy to deploy and low cost.
Client Server
Clients talk to central server with no client to client communication. Good performance and easy administration. Cost is high and deployment can get complex.
LAN - Local Area Network
a group of computers and peripheral devices that share a common communications line or wireless link to a server within a distinct geographic area.
MAN - Metropolitan Area Network
a computer network that is larger than a single building local area network (LAN) but is located in a single geographic area that is smaller than a wide area network (WAN).
