PHY and MAC (Media Access Control)

PHY:

PHY is a common abbreviation for the physical layer of the OSI model.

A PHY connects a link layer device (often called a MAC (Medium Access Controller)) to a physical medium such as an optical fibre or copper cable. A PHY typically includes a PCS and a PMD layer. The PCS encodes and decodes the data that is transmitted and received. The purpose of the encoding is to make it easier for the receiver to recover the signal.

MAC:

The Media Access Control (MAC) data communication protocol sub-layer, also known as the Medium Access Control, is a sublayer of the Data Link Layer specified in the seven-layer OSI model (layer 2).

It provides addressing and channel access control mechanisms that make it possible for several terminals or network nodes to communicate within a multi-point network, typically a local area network (LAN) or metropolitan area network (MAN).

The hardware that implements the MAC is referred to as a Medium Access Controller.

The MAC sub-layer acts as an interface between the Logical Link Control (LLC) sublayer and the network's physical layer. The MAC layer emulates a full-duplex logical communication channel in a multi-point network. This channel may provide unicast, multicast or broadcast communication service.


IEEE 802 LAN architecture:

Practical, connectionless LANs began with the pre-IEEE Ethernet specification, which is the ancestor of IEEE 802.3. This layer manages the interaction of devices with a shared medium, which is the function of a Media Access Control sublayer. Above this MAC sublayer is the media-independent IEEE 802.2 Logical Link Control (LLC) sublayer, which deals with addressing and multiplexing on multiaccess media.

While IEEE 802.3 is the dominant wired LAN protocol and IEEE 802.11 the wireless LAN protocol, obsolescent MAC layers include Token Ring and FDDI. The MAC sublayer detects but does not correct errors


OSI Model

7 Application Layer
6 Presentation Layer
5 Session Layer
4 Transport Layer
3 Network Layer
2 Data Link Layer

* LLC sublayer
* MAC sublayer

1 Physical Layer

Reference:

http://en.wikipedia.org/wiki/PHY_%28chip%29

http://en.wikipedia.org/wiki/Media_Access_Control

http://en.wikipedia.org/wiki/Logical_Link_Control

http://en.wikipedia.org/wiki/OSI_model