DCN286 Introduction to Data Communication Technology Session 6

Review 1) Which of the following describes attenuation? a) A loss of signal strengthb) An increase in signal strength c) The delay experienced during d) The time it takes a signal to reach signal travelits destination 2) Which of the following are tests specified by TIA/EIA-568-B standard for copper cable? (Select 3 answers)? a) Signal harmonicsb) Conductive response c) Wire mapd) Signal absorption e) Insertion lossf) Propagation delay 3) What are three distinct kinds of crosstalk (Select three answers)? a) NEXTb) FEXT c) ANEXTd) SPNEXT e) PSNEXT 4) Which cable type is cheapest to install? a) Coaxialb) Fibre-optic c) STPd) UTP 5) What can be discovered by using an Ethernet cable-testing device to do wire maps? a) Faulty serial circuitsb) The location of a cabling run c) Information about the distance d) Incorrect pinouts to a cabling fault

Objectives Design Considerations Repeaters, Hubs, Bridges and Switches Models for PC Communications Cabling WANs DTE and DCE cables Console

Ethernet LAN Physical Layer 4 Design Considerations Data Link Layer Physical Layer ISO Layers Ethernet IEEE (Logical Link Control - LLC) IEEE (Media Access Control – MAC) 10BASE2 10BASE5 10BASE-T 10BASE-F 100BASE-TX 100BASE-FX 100BASE-T4 1000BASE-T 1000BASE-X

Picking a cable Maximum cable length (per standard) vs. length of run required Cost of the cable Cost of equipment at each end of cable Which cables support different Ethernet speeds Ease of installation Susceptibility to interference 5 Design Considerations

Choosing Ethernet Types (Speeds) When choosing the Ethernet speed, what attribute of a communications link are we selecting? When this is determined – is it a once-size-fits-all installation? Consider the following three ways you can categorize the installation: End-user level – link from Hub/Switch to PC's NIC Workgroup level – links from Hubs/Switches that connect End-user level to other Hubs/Switches in the LAN core Backbone level - links from Hubs/Switches to other Hubs/Switches in the LAN core (no end-user devices) 6 Design Considerations

Choosing Ethernet Types (Speeds) 7 Design Considerations 10/100Mbps 100Mbps-1Gbps 1Gbps-10Gbps End-user Level Workgroup Level Backbone Level Bandwidth Requirement

Choosing Ethernet Types (Speeds) 8 Design Considerations Access Links Uplinks Core Links Access Switches Distribution Switches Core Switches Building Block to other building blocks to other building blocks

Picking UTP Cable Pinouts Straight-through cable Connects what to what? Wire both ends TIA/EIA-T568-A OR Wire both ends TIA/EIA-T568-B 9 Design Considerations

Picking UTP Cable Pinouts Crossover cable Connects what to what? 10BASE-T and 100BASE-TX Wire one side TIA/EIA-T568-A and the other end TIA/EIA-568-B 1000BASE-T Wire one end TIA/EIA-T568-B, on the other end swap the orange/green pair (pairs 1 and 2) with the blue/brown pair (pairs 3 and 4) 10 Design Considerations

Picking UTP Cable Pinouts Transmit PairDevices Pins 1 & 2PCs (NIC cards), routers, servers, wireless access points Pins 3 & 6Switches, hubs bridges, repeaters Straight-though cable when connecting a device that transmits on Pins 1 & 2 to a device that transmits on Pins 3 & 6. Crossover cable when connecting a device that transmits on Pins 1 & 2 to another device that transmits on Pins 1 & 2. Or connecting a device that transmits on Pins 3 & 6 to another device that transmits on Pins 3 & Design Considerations

Picking UTP Cable Pinouts Some devices have built-in crossover capabilities. Look for an 'X' on the port's label 1X1 22X 3XX3X 12 Design Considerations

Connecting Ethernet Networking Devices Repeater Purpose? Rule: maximum 5 cables, maximum 4 repeaters, and maximum 3 cables can have end-user devices Hub Purpose? Passive – no power required to run, does not repeat signal Active – power required, repeats signal Intelligent – Active Hub with some management capability 13 Design Considerations

Connecting Ethernet Networking Devices Bridge Purpose? How does it work? Switch Purpose? 14 Design Considerations

Client A network device that requires use of a resource Server A network device that provides the resource or service used by a client Peer-to-Peer A net model where computers act as equals (peers) providing their service to each other. A PC may act as a client in one moment and as a server in another Client/Server A network model where a PC is designated as being a client or being a server 15 Models for PC Communications

Peer-to-Peer Advantages: Capability is built into modern operating systems Easy to set up Does not require administrator to manage No special hardware or software required Disadvantages: No centralized security controls (user responsible for protecting their own PC) Backups must be performed by each individual PC's performance drops while acting as a server Each user needs to be trained properly manage their own PC 16 Models for PC Communications

Client/Server Servers are more powerful machines that the typical user's. The O/S is a Network Operating System (NOS) that is designed specifically for the purpose. Must be available 24/7 – which implies multiple servers to allow for failure or backups. 17 Models for PC Communications

Client/Server Advantages: Centralized security – controlled through user ID and password Easy to backup data – especially data that has regulatory requirements More scalable than peer-to-peer Disadvantages: Hardware / software costs are greater Personnel costs are higher as you require dedicated Network Administrators Servers can be a single point of failure (through poor design or cost restrictions) 18 Models for PC Communications

Router Router may have dedicated ports for various connection methods (DSL, ISDN,...), however more typically they have a single serial interface. It is up to the network engineer to decide on the serial connection. The N.E. selects the serial device (requires a Channel Service Unit (CSU) and Data Service Unit (DSU)) and orders the appropriate cables. 19 Cabling WANs

Telco Router Sample WAN link: 20 Cabling WANs Cable with RJ-45 Connector CSU / DSU Serial Interface Serial cable (short)

Router 21 Cabling WANs

Router Telco provides: CSU/DSU Data communications cable with RJ-45 jacks Router supplier provides: Router with specific serial interface (EIA-232, EIA-449, V.35, X.21, EIA Appropriate cable (maybe) (built-in CSU/DSU available) Network Engineer provides Appropriate cable for serial interface to CSU/DSU Selection of serial protocol: Point-to-Point Protocol (PPP), High- Level Data Link Control (HDLC), Frame Relay 22 Cabling WANs

WAN Links Cable: Uses CATV coaxial cable DSL: Uses phone line ISDN (Integrated Services Digital Network) Connection dialed like a phone number Used as a fail-over link if leased line goes down BRI (Basic Rate Interface) runs over phone line – 2 x 64Kbps B channels and a 16Kbps D channel PRI (Primary Rate Interface) – 23 x 64Kbps B + 1 x 64Kbps D channels = 1.5Mbps 23 Cabling WANs

WAN Speeds Run at a variety of speeds, eg 2400bps (2.4Kbps) Typically run in multiples of 64Kbps up to 1.536Mbps T1 line runs at 1.536Mbps. Multiples of T1 are available, for example T3 runs 28 times faster, giving about 43Mbps SONET uses fibre-optic cables with a minimum speed of 51.84Mbps. Multiples of 51.84Mbps are available up to 10Gpbs. Telco charges for the service – the faster the service the more you pay. 24 Cabling WANs

WAN Speeds vs Cable Lengths Data (bps)Distance (m)Distance (m) EIA-232EIA-449, V.35, X.21, EIA T1 (1.5Mbps)-15 This is the distance between your router and the CSU/DSU – typically these distances are not an issue as the router and CSU/DSU are in the same room or cabinet. 25 Cabling WANs

Data Communications Equipment (DCE) A device that supplies clocking to another device Modems, Hubs, Bridges, Switches Data Terminal Equipment (DTE) A device that receives clocking from another device and adjusts its clock as needed NIC (PC), Routers, AP (WLAN Access Point) 26 DCE / DTE Cables

Connecting Routers “back-to-back” Used in lab situations Connecting a DTE cable to a DCE cable Performs crossover of transmit and receive lines, and allows router acting as DCE to provide clocking signals. 27 DCE / DTE Cables DTE cableDCE cable Tx Rx

Connecting Asynchronous DTE Devices “back-to-back” Used in lab situations - transmit and receive lines are crossed - other signal lines (CTS, RTS, DSR) are connected together to fool the DTE into believing it is connected to a modem that has an active session to a remote DCE/DTE. 28 NULL Modem Cable