1. The Medium Access Control
Physical Media
The Medium Access Control
Sub-Layer
Chapter 6

2. The Medium Access Sub-Layer
Physical Media
The Medium Access Sub-Layer
Networks can be divided into two categories:
Point-to-point connections
Broadcast channels
Broadcast channels are sometimes referred to as multi access channels or random access channels.
Multi-access channel belong to a sub layer of the data link layer called the MAC (Medium Access Control) sub layer.

3. Physical Media
Ethernet
Ethernet is connection media access method that allows all host on a network to share the same bandwidth of a link. Two kinds of Ethernet exist:
Classic Ethernet: which solves the multiple access problem using the multiple access techniques.
Thick Ethernet
Thin Ethernet
Switched Ethernet: In which devices called switches are used to connect different computers.
Fast Ethernet
Gigabit Ethernet
10-Gigabit Ethernet: 10 Gbps is a truly prodigious speed, 1000x faster than the original Ethernet.

4. Classic Ethernet Physical Media
Thick Ethernet: is a classic Ethernet snaked around the building as a single long cable to which all the computers were attached.
Thin Ethernet: which bent more easily and made connections using industry-standard BNC connectors.
A repeater is a physical layer device that receives, amplifies (i.e., regenerates), and retransmits signals in both directions.

5. Switched Ethernet Physical Media
Switched Ethernet: In which devices called switches are used to connect different computers.
Switches only output frames to the ports for which those frames are destined. When a switch port receives an Ethernet frame from a station, the switch checks the Ethernet addresses to see which port the frame is destined for.
Hubs are simpler and cheaper than switches, but due to falling switch prices they have become an endangered species. Modern networks largely use switched Ethernet. Nevertheless, legacy hubs still exist.

6. Fast Ethernet Physical Media
The basic idea behind fast Ethernet was simple: keep all the old frame formats, interfaces, and procedural rules, but reduce the bit time from 100 nsec to 10 nsec.
The main disadvantage of a Category 3 twisted pair is its inability to carry 100 Mbps over 100 meters, the maximum computer-to-hub distance specified for 10-Mbps hubs.
In contrast, Category 5 twisted pair wiring can handle 100 m easily, and fiber can go much farther.

7. Physical Media
Gigabit Ethernet
Gigabit Ethernet: supports both copper and fiber cabling.
Signaling at or near 1 Gbps requires encoding and sending a bit every nanosecond.

8. Physical Media
10-Gigabit Ethernet
10-Gigabit Ethernet: 10 Gbps is a truly prodigious speed, 1000x faster than the original Ethernet.
The long distance connections use optical fiber, while the short connections may use copper or fiber.

9. Wireless LANs Physical Media
The main wireless LAN standard is Wireless LANs can operate in one of two configurations, with a base station and without a base station.
networks can be used in two modes.
In infrastructure mode, each client is associated with an AP (Access Point) that is in turn connected to the other network.
An ad hoc network: This mode is a collection of computers that are associated so that they can directly send frames to each other. There is no access point.

10. Bluetooth Physical Media
Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances (ISM band from  MHz).
Bluetooth 1.0 was released in July 1999.
For higher data rates were added to Bluetooth 2.0 in 2004.
The 3.0 release in 2009, Bluetooth can be used for device pairing in combination with for high-throughput data transfer.
The 4.0 release in December 2009 specified low-power operation.
The basic unit of a Bluetooth system is a piconet, which consists of a master node and up to seven active slave nodes with in a distance of 10 meters.
An interconnected collection of piconets is called a scatternet.
In addition to the seven active slave nodes in a piconet, there can be up to 255 parked nodes in the net.

11. Bluetooth Architecture
Physical Media
Bluetooth Architecture