Provides interface between software applications and network for interpreting applications’ requests and requirements.
Allows hosts and applications to use a common language; performs data formatting, encryption, and compression. a.k.a. “syntax layer”.
Establishes, maintains, and terminates user connections.
Ensures accurate delivery of data through flow control, sementation and reassembly, error correction and acknowledgement. (TCP)
Establishes network connections; translates network address into their physical counterparts and determines routing through logical addressing (IP addresses).
2. Data link:
Packages data into frames appropriate to network transmission method.
2a. Logical Link Control (LLC) Sublayer:
Addressing and channel access control mechanisms
2b. Media Access Control (MAC) Sublayer:
Node-to-node error control.
Manages signalling to and from physical network connections.
Examples of devices/services:
Physical – Ethernet, Token Ring. A hub or repeater works here.
Data Link – Ethernet, ATM. A switch or bridge works here.
Network – ARP, RIP, IPv4, IPv6. A router works here.
Transport – TCP, UDP, SPX
Session – PPTP, H.245, NetBIOS, AppleTalk, WinSock
Presentation – JPEG, GIF, MPEG
Application – DHCP, DNS, FTP, HTTP, LDAP, SSH, SIP, SMTP