Introduction to Networking James R. Coakley, PhD OEMBA Information Systems

Theoretical Framework: 5-layer network model  Application Layer (Layer-5)  Transport Layer  Network Layer  Data Link Layer  Physical Layer (Layer-1) Application Transport Network Data Link Application Transport Network Data Link Physical Application Transport Network Data Link Physical

Theoretical Framework: 5-layer network model  Application Layer (Layer-5)  Transport Layer  Network Layer  Data Link Layer  Physical Layer (Layer-1) Application Transport Network Data Link Application Transport Network Data Link Physical Application Transport Network Data Link Physical

Five-Layer Network Model Major Functions  Application Layer (top) User interface with application software HTTP (Hyper Text Transfer Protocol) Example of an application layer address: FTP (File Transfer Protocol) Telnet Allows you to log on to remote systems SMTP (Simple Mail Transfer Protocol)

Theoretical Framework: 5-layer network model  Application Layer (Layer-5)  Transport Layer  Network Layer  Data Link Layer  Physical Layer (Layer-1) Application Transport Network Data Link Application Transport Network Data Link Physical Application Transport Network Data Link Physical

Five-Layer Network Model Major Functions  Transport Layer Packetizing Break large messages into smaller packets at source Reassemble packets at final destination Creates/appends TCP (Transmission Control Protocol) header  Packet #  Source/Destination Port ID  80 (Web)  25 ( ) Data PacketTCP Hdr

What is a “Port”?  A channel for passing data in and out of a computing device Input Devices Secondary Storage Output Devices Control Unit Primary Storage ALU Registers The CPU Communication Devices Port

 Numbers allow different applications on the same computer to utilize network resources without interfering with each other The IP address is like a telephone number Identifies the computer on the network The Port is the extension Identifies the channel within the computer

Theoretical Framework: 5-layer network model  Application Layer (Layer-5)  Transport Layer  Network Layer  Data Link Layer  Physical Layer (Layer-1) Application Transport Network Data Link Application Transport Network Data Link Physical Application Transport Network Data Link Physical

Five-Layer Network Model Major Functions – cont’d  Network Layer: Addressing and Routing. Internet Protocol prepares IP header. Contents of IP header include Source/Destination IP Address and Routing Information Example of an IP address: Addressing DHCP Server (Dynamic Host Control Protocol Server)  Assigns IP addresses to client machines requesting an IP address DNS Server (Domain Name Service Server)  Similar to directory assistance – used for finding destination IP addresses. Routing Routing tables; Routers (Tracert); Routing Protocols Data PacketTCP HdrIP Hdr

Theoretical Framework: 5-layer network model  Application Layer (Layer-5)  Transport Layer  Network Layer  Data Link Layer  Physical Layer (Layer-1) Application Transport Network Data Link Application Transport Network Data Link Physical Application Transport Network Data Link Physical

Five-Layer Network Model Major Functions – cont’d  Data Link Layer Media Access Control (Handling message collisions) Error Detection/Error Correction Message Delineation (Identifying beginning and ending of packets – since all computer transmissions go out as 0s and 1s over the physical layer) DL layer appends a DL header and DL Trailer Data PacketTCP HdrIP HdrDL Hdr

Data Link Layer Data Direction Methods  Methods to direct data between locations Circuit switching Packet switching Frame relay Faster, less expensive Does not perform error correction ATM, etc.

Data Link Layer Protocols  What: the communication language used by computing devices in a network

Data Link Layer Protocols  Ethernet: Bus with CSMA/CD Carrier Sense Multiple Access/Collision Detection Fast Ethernet (100 mbps) Gigabit Ethernet  Token Ring  FDDI Fiber Distributed Data Interface Token Ring on fiber

FDDI

FDDI (Continued)

Local Area Network  Connects PCs together Peer-to-peer Server-based File server  Distance restrictions Between 1000 and 5000 feet Why?

Wide Area Network  What is it?  How connect? Leased Lines Satellite  Other options VAN Private, data-only network managed by third party Virtual Private Network Run WAN over internet (tunneling)

Data Link Layer Internetworking Devices  Gateway: Where one network meets another  Routers & Bridges: Gateways that determine the next network point to which a packet should be forwarded Bridge – same network protocol – works at data link layer Router – different network protocol – works at network layer  Switch & Hub: Joins computers together within a LAN Switches can inspect packets and forward only to address Hub forwards to all nodes

Internetworking Devices  Connect Networks together Gateway (NL) Connect networks with different protocols Router (NL) Connect networks with different protocols Bridge (DL) Connect networks with same protocol Hubs (PL) Route messages on network using broadcast Switch (PL) Route messages on network using Point-to- point

Data Link Layer Internetworking Devices  Broadband router Combines the features of a traditional network switch, firewall, and DHCP server Dynamic Host Configuration Protocol DHCP assigns unique IP addresses to devices Releases and renews these addresses as devices leave and re-join the network Eliminates need for pre-configured IP address Firewall Restricts access to network based on IP address of sender

Theoretical Framework: 5-layer network model  Application Layer (Layer-5)  Transport Layer  Network Layer  Data Link Layer  Physical Layer (Layer-1) Application Transport Network Data Link Application Transport Network Data Link Physical Application Transport Network Data Link Physical

Layer 1 - Physical Layer  Wired Media/Wireless Media: Examples Twisted pair; Coaxial; Fiber Optic Cables Microwave; Satellites and wireless (cell phones)

Physical Layer Background on Telecommunications  Modem Modulate – demodulate Multiplexing

Physical Layer Telecommunications Media  Criteria that determine ability to transmit data: Frequency: cycles per second (baud). Hertz is one cycle per second. measure of speed. (assume send one bit per cycle) Bandwidth: difference between highest and lowest frequencies which can be transmitted. measure of capacity (pulse-code modulation) Attenuation: signal strength weakens as it travels over distance. Interference: EMI (electromagnetic) and RFI (radio frequency)

Physical Layer Telecommunications Media (cont’d)  Physical: Twisted Pair: standard telephone lines High availability, lower speeds, poor security High-speed data lines  T1 (1.54 mbps)  T3 (45 mbps) Cable: coaxial cable Less interference, higher bandwidth Higher cost, low security Optical Greater speed, better security

Physical Layer Telecommunications Media (cont’d)  Electronic Microwave Towers spaced 30 miles apart (line of sight) Easier than trenching wires into dirt Susceptible to interference Satellite Eliminates line-of-sight issue Propagation delay HF (high frequency)/RF (radio frequency) Use for short range (within warehouse)

Backbone

Physical Layer Broadband Communications  High-speed connections Distinguish “upstream” and “downstream” 56K modem has upstream of 31.2 and downstream of 56 For Internet use, need higher downstream rates  Three options: DSL (telephone lines) Cable Modem (cable) Satellite (microwave)

Cable Modem  Send and receive data over the coaxial cable used in cable television system

DSL - Digital Subscriber Lines  Brings high bandwidth information to homes or small businesses over ordinary telephone lines Can use telephone and PC on the same line and at the same time

Satellite Technologies  A device used to transmit and receive signals from a satellite transponder

How does it work?

Ping  Used to test connection to a specific site  Ping Sends four, 32-byte packets to the destination

Multiple competing technologies CDMA - 1xRTT : code-division multiple access  70 kbps data rate  Mostly US, Canada, Korea GSM-GPRS: global system for mobile communication  40 kbps data rate  Available world-wide  T-Mobile has roaming agreements in Europe CDPD: Cellular Digital Packet Data  Based on IP (packet switched) and conforms to ISO standards  Up to 19.2 kbps data rate Physical Layer Wireless Wide Area Network

 Closer to having standards for WLAN Wi-Fi: families  (b) – wireless ethernet.  2.5 Ghz band  11 mbps (5 mbps data rate)  (a) – proposed standard. 54 mbps on 5 Gig radio band  (g) – works in b band, but delivers 54 mbps speed (20 mbps data rate) Bluetooth  Connect devices to PC within 30 feet  710 kbps IR devices  6 feet, 4 mbps WiMax Physical Layer Wireless Local Area Network

Application Layer Wireless Application Protocol  WAP Format web pages for display on wireless devices Move to fully synchronized PDAs Providence Health Care