1. COMMON LAYER 1
DEVICES AND
FUNCTIONALITIES

2. Introduction 7 6 5 4 3 2 1 Devices will be covered starting at layer 1
Routers, PAD’s, X.25 switches
Bridges, LAN switches, ATM switches and terminal servers
Transceivers, repeaters, hubs, FDDI concentrators, MSAU’s, modems, terminal adapters, DSU’s, CSU’s, MUX and NIC’s 3 2 1

3. Transceivers 7
A transceiver connects a network device to the network cable
A transceiver listens to the bus to determine if it is being used by another station
A transceiver determines if the bus is being used by another station
A transceiver alerts the connected device when there is a collision during transmission
A transceiver may have DIP switches for controlling the exchange of SQE or heartbeat signals with the directly connected device. 6 5 4 3 2 1

4. Transceivers
Attachment Interface Unit (AUI): The portion of the Ethernet standard that specifies how a cable is to be connected to an Ethernet card. AUI specifies a coaxial cable connected to a tranceiver that plugs into a 15-pin socket on the network interface card (NIC).

5. Repeaters 7
A repeater is used to connect two segments of the same network
A repeater receives a signal from one segment, cleans and boosts the signal and sends it to the other segment
A repeater is responsible for ensuring that a collision is propagated to all attached segments
A repeater may be used to extend the network beyond the limitations of the network’s architecture by increasing segment length
Cannot add an infinite number of repeaters as this would adversely affect collision propagation. 6 5 4 3 2 1

6. Repeaters

7. Hubs
A hub often attaches at least four nodes and many hubs include connectors for linking to other hubs
A hub provides connectivity by passing incoming signals to connected nodes
Hubs may be cascaded together to allow small workgroups with low-intensity applications to be formed
Hubs typically have LEDs to indicate the status of each port
Hubs may do partitioning to allow isolation of a non-functioning node
Hubs allow connection to different physical media. 7 6 5 4 3 2 1

8. Hubs

9. NIC’s 7
A NIC is an internetworking device that is a component part of a much larger host
NICs are used to connect the systems to the network
NICs will be different for each type of host system and type of network topology (and for each bus type)
Remote access is achieved through remote access to the host system
When installing a NIC it is important to consider the network topology, cabling and electrical considerations to avoid network disruption. 6 5 4 3 2 1

10. NIC’s