OSI Model Flashcards
Used by end-user software such as web browsers and email clients. It provides protocols that allow software to send and receive information and present meaningful data to users.
– Apps, web browsing, email, file transfer, management sessions.
Application Layer (7)
Defines how two devices should encode, encrypt, and compress data so it is received correctly on the other end.
–Data conversion, formatting, encrypt/decrypt, file types, data compression.
Presentation Layer (6)
Creates communication channels, called sessions, between devices. It is responsible for opening sessions, ensuring they remain open and functional while data is being transferred, and closing them when communication ends.
–NetBIOS, SAP, ZIP, SQL
Session Layer (5)
Takes data transferred in the session layer and breaks it into “segments” on the transmitting end. It is responsible for reassembling the segments on the receiving end, turning it back into data that can be used by the session layer.
Carries out flow control, sending data at a rate that matches the connection speed of the receiving device, and error control, checking if data was received incorrectly and if not, requesting it again.
–TCP/UDP, port #’s
Transport Layer (4)
Has two main functions; one is breaking up segments into network packets, and reassembling the packets on the receiving end. The other is routing packets by discovering the best path across a physical network.
Uses network addresses (typically Internet Protocol addresses) to route packets to a destination node.
–Adds network addresses, routing, data becomes a packet. IPV4, IPV6, ICMP, IPSEC, ARP, MPLS, IGMP, RIP
Network Layer (3)
Establishes and terminates a connection between two physically-connected nodes on a network. It breaks up packets into frames and sends them from source to destination.
This layer is composed of two parts—Logical Link Control (LLC), which identifies network protocols, performs error checking and synchronizes frames, and Media Access Control (MAC) which uses MAC addresses to connect devices and define permissions to transmit and receive data.
– LLC and MAC sublayers ARP, CDP, HDLC, STP, RAPA, PPP, Frame Relay, ATM, Fiber Cable
Data Link layer (2)