LAYER 1

Represents services that directly support user applications such as software for file transfers, terminal emulation, database access and query processing, and e-mail

Translates data into a commonly recognized, intermediary format;

LAYER 2

Responsible for syntax conversion between systems that have different text and data character representations, such as ASCII and EBCDIC

PRESENTATION LAYER

Responsible for Data compression, translation, encryption/decryption, conversion between graphic file types, and protocol conversion

SESSION LAYER

LAYER 3

Protocols coordinate and maintain communications between two network nodes; Keeps communication secure

Establish and maintain communications link for duration of session

LAYER 4

Manages end-to-end delivery of data; Protocols also handle flow control

Establish connection before transmitting data; Ensure data transferred reliably, in correct sequence, and without errors

breaks large data units received from prevous layer

into smaller segments (segmentation)

Reassembing and Sequencing:

does not establish connection before transmitting; transmits faster

NETWORK LAYER

LAYER 5

Translates network addresses into physical counterparts;

Decides how to route data from sender to receiver

adds logical addressing information; handles routing - Determining best network path; fragmentation

subdivides segments it receives from Transport layer into smaller packets

2 ADDRESSES

1. Network (logical) address

2. Physical address

DATA LINK LAYER

LAYER 6

divides received data into distinct frames;

DATA LINK LAYER

Ensures data at destination exactly matches data issued from source

DATA LINK LAYER

HAS 2 LAYERS

Logical Link Control (LLC) sublayer

Media Access Control (MAC) sublayer

Media Access Control (MAC)

Data link sublayer

Manages access to Physical layer - Appends destination computer’s physical address onto data frame

Data link sublayer

Provides interface to Network layer protocols

Manages flow control

PHYSICAL LAYER

LAYER 7

Bottom layer of OSI model. Sees all data as stream of bits. Translates bits of data into a format suitable for transmission or receives a transmission and translates it back into bits.

PHYSICAL LAYER

Protocols accept frames and generate voltage to transmit signals;

Provides interface to the cable