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Cisco Systems CCNA Version 3 Semester 1

Module 5

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This is the Connector

This is the Jack

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This is the Jack

This is the Connector568A

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This is the Jack

This is the Connector

568B

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Properly Crimped

Good Jacket Length

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Transmit Data

Tip +ve

Transmit Data

Ring -ve

Receive DataTip +ve

Receive DataRing -ve568B

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Signal leaves the NIC and enters the cable on the Orange pair. White-Orange is +ve, solid Orange is

negative.

Signal leaves the cable and enters the NIC on the SPLIT Green pair. White-Green is +ve, solid Green is

negative.

568B

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568B 568A

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Use straight-through cables for… •Switch to router •Switch to PC or server •Hub to PC or server

Use crossover cables for…•Switch to switch •Switch to hub •Hub to hub •Router to router •PC to PC •Router to PC

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No more than four repeaters can be used between hosts on a LAN. This rule is used to limit latency added to frame travel by each repeater.

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•Passive – A passive hub serves as a physical connection point only. It does not boost or clean the signal and does not need electrical power. •Active – An active hub needs power to repeat the signal before passing it out the other ports. •Intelligent – Intelligent or smart hubs are active hubs with a microprocessor chip and diagnostic capabilities.

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•Devices attached to a hub receive all traffic traveling through the hub. •The more devices there are attached to the hub, the more likely there will be collisions. •A collision occurs when two or more workstations send data over the network wire at the same time. •All data is corrupted when that occurs. •Every device connected to the same network segment is said to be a member of a collision domain.

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Two approaches currently being used to implement spread spectrum for WLAN transmissions are Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS).

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•There are times when it is necessary to break up a large LAN into smaller, more easily managed segments. •This decreases the amount of traffic on a single LAN and can extend the geographical area past what a single LAN can support. •The devices that are used to connect network segments together include bridges, switches, routers, and gateways. •Switches and bridges operate at the Data Link layer of the OSI model. •The function of the bridge is to make intelligent decisions about whether or not to pass signals on to the next segment of a network

If placed strategically, a bridge can greatly improve network performance.

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•If the destination device is on the same segment as the frame, the bridge blocks the frame from going on to other segments. This process is known as filtering.

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•If the destination device is on a different segment, the bridge forwards the frame to the appropriate segment. •If the destination address is unknown to the bridge, the bridge forwards the frame to all segments except the one on which it was received. This process is known as flooding.

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A bridge or switch determines whether the frame should be forwarded to the other network segment based on the destination MAC address.

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A switch has many ports with many network segments connected to them. A switch chooses the port to which the destination device or workstation is

connected.

Ethernet switches are becoming popular connectivity solutions because, like bridges, switches improve network performance by improving speed and

bandwidth.

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1. A switch is sometimes described as a multiport bridge.

2. Switches build forwarding tables to determine the destination of data being sent by one

computer to another computer on the network.     3. A switch is a more sophisticated device than a bridge.

4. Switching is a technology that alleviates congestion in Ethernet LANs by reducing the

traffic and increasing the bandwidth.

5. Switches can easily replace hubs because switches work with existing cable infrastructures.

This improves performance with a minimum of intrusion into an existing network.

6. Switches equipment performs two basic operations. The first operation is called switching

data frames. Switching data frames is the process by which a frame is received on an input

medium and then transmitted to an output medium. The second is the maintenance of

switching operations where switches build and maintain switching tables and search for

loops.

7. Switches operate at much higher speeds than bridges and can support new functionality,

such as virtual LANs (VLANs).

8. An Ethernet switch allows many users to communicate in parallel through the use of virtual

circuits and dedicated network segments in a virtually collision-free environment.    

9. This maximizes the bandwidth available on the shared medium. Another benefit is that

moving to a switched LAN environment is very cost effective because existing hardware and

cabling can be reused.

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The function of a NIC is to connect a host device to the network medium.

NICs are considered Layer 2 devices because each NIC carries a unique code called a MAC address.

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•Two computers typically communicate with each other by using request/response protocols. •The requestor takes on the role of a client, and the responder takes on the role of a server.

•In a peer-to-peer network, networked computers act as equal partners, or peers. •As peers, each computer can take on the client function or the server function.

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In a peer-to-peer network, individual users control their own resources.

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•Peer-to-peer networks are relatively easy to install and operate.

•No additional equipment is necessary beyond a suitable operating system installed on each computer. •Since users control their own resources, no dedicated administrators are needed.

•As networks grow, peer-to-peer relationships become increasingly difficult to coordinate.

•A peer-to-peer network works well with 10 or fewer computers.•Their efficiency decreases rapidly as the number of computers on the network increases. •Also, individual users control access to the resources on their computers, which means security may be difficult to maintain. •The client/server model of networking can be used to overcome the limitations of the peer-to-peer network.

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•In a client/server arrangement, network services are located on a dedicated server. •The server is a central computer that is continuously available to respond to requests from clients for file, print, application, and other services. •Most network operating systems adopt the form of a client/server relationship. •Typically, desktop computers are the clients and one or more computers with additional processing power, memory, and specialized software function as servers.

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5.2.1 WAN physical layer

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xDSL - Digital Subscriber Line Technology

• The key in xDSL technology is modulation, a process in which one signal modifies a properties of another.

• Hardware: DSL requires modems and splitters for end-users; carriers use DSLAMs (digital subscriber line access multiplexers)

• Differences between xDSL technologies: speed, operating distance, applications, ratio between up and downstream

• Different approaches: ATM-based ADSL, ISDN DSL.

• The important thing is what is running over xDSL...

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xDSL - Digital Subscriber Line Technology

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xDSL Digital Subscriber Line Technology

ADSL - Asymmetric Digital Subscriber Line •expected in general use in 1999 •twisted pair copper (single loop) •asymmetric: most commonly: 6Mbps (down), 640 Kbps (up)

•downlink: 1.5 Mbps-8 Mbps •uplink : 176 Kbps - 1 Mbps

•limited distance (18000 feet over 26-gauge copper)

RADSL - Rate-Adaptive Digital Subscriber Line •varying speeds depending upon line quality; asymmetric

•downlink: 1.5 Mbps-8 Mbps •uplink : 176 Kbps - 1 Mbps

•limited distance (18000 feet over 26-gauge copper)

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xDSL Digital Subscriber Line Technology (cont.)

HDSL - High-speed Digital Subscriber Line •full-duplex, symmetric

•1.544 Mbps or 2.048 Mbps in each direction •two twisted pairs (for T1) and 3 pairs (for E1) •max distance 12,000 feet

VDSL - Very-high-bit-rate Digital Subscriber Line (known as BDSL)

•asymmetric •downlink: 12.96-51.84 Mbps •uplink : 1.6 - 2.3 Mbps

•max 4,500 - 1,000 feet •applications: High definition TV, multimedia

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1. A network interface card (NIC) provides network communication capabilities to and from a PC. 

2. Use a crossover cable to connect between two similar devices, such as switches, routers, PCs, and hubs.

3. Use a straight-through cable to connect between different devices, such as connections between a switch and a router, a switch and a PC, or a hub and a router.

4. There are two major types of LANs, peer-to-peer and client/server. 5. WANs use serial data transmission. WAN connection types include

ISDN, DSL, and cable modems. 6. A router is usually the DTE and needs a serial cable to connect to a

DCE device like a CSU/DSU. 7. The ISDN BRI has two types of interfaces, S/T and U interfaces. To

interconnect the ISDN BRI port to the service-provider device, a UTP Category 5 straight-through cable with RJ-45 connectors, is used.

8. A phone cable and an RJ-11 connector are used to connect a router for DSL service.

9. Coaxial cable and a BNC connector are used to connect a router for cable service.

10. Rollover cable is used to connect a terminal and the console port of an internetworking device.

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FIN