Network Devices and Topologies: Components of a Network PC
- Components used by a computer to enable network connectivity:
- CPU
- bus
- drives
- memory components
- port
- cards
As well as drivers and memory the NIC needs:
- I/O address – to read or write data to the computer. The I/O address identifies a part of memory that is assigned for use by the NIC
- IRQ signal – identifies which device in the computer is requestingthe CPU to perform a funcion. For example, when data arrives into a NIC its IRQ indicates to the CPU that is had data that needs to be processed for the NIC.
To install a NIC you need to understand:
- EPROM – Erasable Programmable Read-Only Memory
- Jumpers and switch settings
- Pulg and Play software
If there is a problem with the NIC you should be able to:
- Use Card diagnostics – such as loop back tests and diagnostic procedures supplied by the vendor
- fix hardware resource conflicts with IRQ and DMA (direct memory access).
Network Devices and Topologies: Network Devices
OSI L1 – (Physical Layer/Bit Layer)
- Repeaters – regenerate and retransmit electrical signals so they can travel greater distances without deteriorating. The operate at the bit level. A multiport repeater is called a Hub
- Hub – a multiport repeater receives on one port and transmits on all the other ports
OSI L2 – (Data-Link/Frame Layer – MAC address)
- NIC – each NIC has a unique MAC address
- Bridge – create LAN segments. Provides extra bandwidth for data exhcange by
- filtering local LAN traffic
- Maintaining connectivity between network segments directly connected to it
- Bridges (unlike hubs) can effeciently manage data transmission between connected segments based on MAC addresses and filter out unnecessary traffic from reaching a segment
- Gathers and manages MAC address in a table. Each port created a separate collision domain – so a collision on one segment does not affect other segments.
- Switch – create multiple bridge connections
- conect LAN segments into single networks and use MAC addresses to decide where to forward the traffic. Faster than bridges because switching decisions are performed using specialized hardware instead of software.
- each port behaves like a separate bridge (sometimes called “microsegmentation”)
OSI L3 (Network Layer/Packet Layer – IP Addres)
Router – uses L3 addresses (IP Addresses) to transmit data packets between networks. Uses IP instead of MAC to determine path.
- can connect differnt L2 technologies (ie – Token Ring and Ethernet)
- can examine L4 (Transport Layer) information when sending data between devices or networks.
Multilayer Switches – can use L3 as well as L2 addresses. Cand deliever L3 functions with the same spped as L2 functions.
Multilayer Devices:
Gateways: A complex network device that connects disparate network environments. (ie a LAn to a mainframe)
- Uses a combination of hardware and software and can carry out translations at various layers of the OSI model
- E-Mail programs typically use gateways to communicate with internet mail servers. They use gateways to translate LAN-based mail mesage into SMTP (Simple Mail Transfer Protocol) format.
Firewalls: Positioned on the edge of private networks to protect them from any unwanted traffic or attacks attempting to access the internal network.
- Examines all traffic and packets to ensure that they are legitimate dropping any that fail to conform to its rules of entry.
AAA Server: Authentication, Authorization and Accounting. Processs requests from users to gain access to network resources.
- only allows authenticated users onto the network
- gives usuer access only to the resources they are authroized to use
- keeps an account of user behavior.
Network Devices and Topologies: Network Topologies
A Topologies describes how a network is laid out and how data is transmitted on it.
- Logical Topology - describes structure and path connection types between different parts of the network. It defines how data flows in the network.
- Physical Topology – Describes the physical arrangement of devices on the network
Bus Topology - all devices are connected to a common cable. A signal terminator is used to absorb the signal at the end of the cable so that is does not reflect back.
Star Topology – all devices are on the network are linked to a common device, such as a switch.
Ring Topology – network is arranged in a logical circle. data is passed on a “token” around the circle. Eliminates the need for a termination device. There are no packet collisions on a ring topology network.
- Single Ring – one ring, data travels in one direction only
- Dual Ring – uses two rings, data travels in both directions. incorporates fault tolerance. FDDI (Fiber Distributed Data Interface) typically uses a dual ring topology.
Mesh topology – each device is connected to the others in the network
- Full - every host is connected to every other host. Allows for redundancy and high level of fault tolerance. Complex and expensive to implement.
- Partial - One host is connected to a number of other hosts. The other hosts are connected to some, but not all of the other hosts.
