INTRODUCTION TO COMPUTER NETWORKS Computer Centre Indian Institute of Technology Kanpur Kanpur INDIA
INTRODUCTION TOCOMPUTER NETWORKS
Computer CentreIndian Institute of Technology Kanpur
Kanpur INDIA
Course Content
Course Content
Lecture 1: Overview of the Course and Network Fundamentals: 2 Hour Lecture 2: OSI Model& TCP/IP Model : 2 HourLecture 3: Physical Media (Copper, Fiber Optic and Wireless) : 2 HourLab 1: IIT Kanpur Datacenter Visit: 2 Hour Lecture 4: UTP & Fiber Cabling: 2 HourLecture 5: LAN Technologies (Ethernet, Fast Ethernet, Gigabit Ethernet, Wireless LAN) : 2 Hour Lab 2: Demo and Practice of UTP & Fiber Cabling: 2 HourLecture 6: LAN Technologies (contd.) : 2 Hour
Course Content
Course Content
Lecture 7: WAN Technologies (Dialup, Leased Line, ISDN, ADSL, Cable Modem, VSAT) : 2 HourLab 3: Demo and Practice of Ethernet & Wireless LAN Setup : 2 HourLecture 8: WAN Technologies (contd.) : 2 HourLecture 9: Internet Protocol (IP) and IP Addressing: 2 HourLab 4: Demo and Practice of Setting up Subnets and IP Address Assignment : 2 Hour Lecture 10: Routing, VLAN, TCP and UDP: 2 Hour Lecture 11: SNMP, Natting, Firewall and VPN: 2 HourLecture 12: Internet and Internet Applications (DNS, Email, Web..): 2 Hour
Course Content
Course Content
Lecture 13: Cisco Basics: 2 Hour Lecture 14: Cisco Switch and Router Configuration : 2 Hour Lab 5: Demo and Practice of Cisco Switch Configuration : 2 HourLab 6: Demo and Practice of Cisco Router Configuration : 2 HourLecture 15: DNS & Web Server Setup on Linux : 2 Hour Lab 7: Demo and Practice of DNS and Web Server Setup : 2 HourLecture 16: Enterprise Network Implementation: 2 Hour
Course Content
Course Content
Lecture 17: Mail Server, Proxy Server & Firewall Setup on Linux : 2 Hour
Lab 8: Demo and Practice of Mail Server , Proxy Server and Firewall Setup : 2 Hour
References
Books
Andrew S. Tanenbaum, Computer Network, Prentice-HallDoughlas E. Comer, Computer Networks and Internethttp://www.cisco.com/public/support/tac/documentation.htmlhttp://www.redhat.com/docshttp://home.iitk.ac.in/~navi/sidbinetworkcourse
Grading Guidelines
Grading
Two Exams: 40% eachLab Assignments: 20%
Minimum 80% attendance and minimum 60% marks are necessary to clear the course.
Introduction to Computer Networks
INTRODUCTION TO COMPUTER NETWORKS
Computer NetworksComputer network connects two or more autonomous computers.
The computers can be geographically located anywhere.
Introduction to Computer Networks
LAN, MAN & WAN
Introduction to Computer Networks
Network in small geographical Area (Room, Building or a Campus) is called LAN (Local Area Network)
Network in a City is call MAN (Metropolitan Area Network)
Network spread geographically (Country or across Globe) is called WAN (Wide Area Network)
Applications of Networks
Introduction to Computer Networks
Resource SharingHardware (computing resources, disks, printers)Software (application software)
Information SharingEasy accessibility from anywhere (files, databases)Search Capability (WWW)
CommunicationEmailMessage broadcast
Remote computingDistributed processing (GRID Computing)
Network TopologyThe network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.
Introduction to Computer Networks
Bus Topology
Commonly referred to as a linear bus, all the devices on a bus topology are connected by one single cable.
Introduction to Computer Networks
Star & Tree Topology
Introduction to Computer Networks
The star topology is the most commonly used architecture in Ethernet LANs. When installed, the star topology resembles spokes in a bicycle wheel.Larger networks use the extended star topology also called tree topology. When used with network devices that filter frames or packets, like bridges, switches, and routers, this topology significantly reduces the traffic on the wires by sending packets only to the wires of the destination host.
Ring Topology
Introduction to Computer Networks
A frame travels around the ring, stopping at each node. If a node wants to transmit data, it adds the data as well as the destination address to the frame. The frame then continues around the ring until it finds the destination node, which takes the data out of the frame.
Single ring – All the devices on the network share a single cable
Dual ring – The dual ring topology allows data to be sent in both directions.
Mesh TopologyThe mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance. It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions. Implementing the mesh topology is expensive and difficult.
Introduction to Computer Networks
Network Components
Introduction to Computer Networks
Physical MediaInterconnecting DevicesComputersNetworking SoftwareApplications
Networking Media
Networking media can be defined simply as the means by which signals (data) are sent from one computer to another (either by cable or wireless means).
Introduction to Computer Networks
Networking Devices
Introduction to Computer Networks
HUB, Switches, Routers, Wireless Access Points, Modems etc.
Computers: Clients and ServersIn a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients.
The server contains the file, print, application, security, and other services in a central computer that is continuously available to respond to client requests.
Introduction to Computer Networks
Networking Protocol: TCP/IP
Introduction to Computer Networks
ApplicationsE-mailSearchable Data (Web Sites)E-CommerceNews GroupsInternet Telephony (VoIP)Video ConferencingChat GroupsInstant Messengers Internet Radio
Introduction to Computer Networks
OSI Model
OSI MODEL
Communication ArchitectureStrategy for connecting host computers and other communicating equipment.Defines necessary elements for data communication between devices.A communication architecture, therefore, defines a standard for the communicating hosts.A programmer formats data in a manner defined by the communication architecture and passes it on to the communication software.Separating communication functions adds flexibility, for example, we do not need to modify the entire host software to include more communication devices.
OSI Model
Layer ArchitectureLayer architecture simplifies the network design.It is easy to debug network applications in a layered architecture network.The network management is easier due to the layered architecture.Network layers follow a set of rules, called protocol.The protocol defines the format of the data being exchanged, and the control and timing for the handshake between layers.
OSI Model
Open Systems Interconnection (OSI) Model
International standard organization (ISO) established a committee in 1977 to develop an architecture for computer communication.Open Systems Interconnection (OSI) reference model is the result of this effort.In 1984, the Open Systems Interconnection (OSI) reference model was approved as an international standard for communications architecture.Term “open” denotes the ability to connect any two systems which conform to the reference model and associated standards.
OSI Model
OSI Reference ModelThe OSI model is now considered the primary Architectural model for inter-computer communications.The OSI model describes how information or data makes its way from application programmes (such as spreadsheets) through a network medium (such as wire) to another application programme located on another network.The OSI reference model divides the problem of moving information between computers over a network medium into SEVEN smaller and more manageable problems .This separation into smaller more manageable functions is known as layering.
OSI Model
OSI Reference Model: 7 Layers
OSI Model
OSI: A Layered Network ModelThe process of breaking up the functions or tasks of networking into layers reduces complexity.Each layer provides a service to the layer above it in the protocol specification. Each layer communicates with the same layer’s software or hardware on other computers. The lower 4 layers (transport, network, data link and physical —Layers 4, 3, 2, and 1) are concerned with the flow of data from end to end through the network. The upper four layers of the OSI model (application, presentation and session—Layers 7, 6 and 5) are orientated more toward services to the applications. Data is Encapsulated with the necessary protocol information as it moves down the layers before network transit.
OSI Model
Physical LayerProvides physical interface for transmission of information.
Defines rules by which bits are passed from one system to another on a physical communication medium.Covers all - mechanical, electrical, functional and procedural - aspects for physical communication.Such characteristics as voltage levels, timing of voltage changes, physical data rates, maximum transmission distances, physical connectors, and other similar attributes are defined by physical layer specifications.
OSI Model
Data Link LayerData link layer attempts to provide reliable communication over the physical layer interface.
Breaks the outgoing data into frames and reassemble the received frames.Create and detect frame boundaries.Handle errors by implementing an acknowledgement and retransmission scheme.Implement flow control.Supports points-to-point as well as broadcast communication.Supports simplex, half-duplex or full-duplex communication.
OSI Model
Network LayerImplements routing of frames (packets) through the network.
Defines the most optimum path the packet should take from the source to the destinationDefines logical addressing so that any endpoint can be identified. Handles congestion in the network.Facilitates interconnection between heterogeneous networks (Internetworking).The network layer also defines how to fragment a packet into smaller packets to accommodate different media.
OSI Model
Transport LayerPurpose of this layer is to provide a reliable mechanism for the exchange of data between two processes in different computers.
Ensures that the data units are delivered error free.Ensures that data units are delivered in sequence.Ensures that there is no loss or duplication of data units.Provides connectionless or connection oriented service.Provides for the connection management.Multiplex multiple connection over a single channel.
OSI Model
Session LayerSession layer provides mechanism for controlling the dialogue between the two end systems. It defines how to start, control and end conversations (called sessions) between applications.
This layer requests for a logical connection to be established on an end-user’s request.Any necessary log-on or password validation is also handled by this layer.Session layer is also responsible for terminating the connection.This layer provides services like dialogue discipline which can be full duplex or half duplex.Session layer can also provide check-pointing mechanism such that if a failure of some sort occurs between checkpoints, all data can be retransmitted from the last checkpoint.
OSI Model
Presentation LayerPresentation layer defines the format in which the data is to be exchanged between the two communicating entities. Also handles data compression and data encryption (cryptography).
OSI Model
Application LayerApplication layer interacts with application programs and is the highest level of OSI model.Application layer contains management functions to support distributed applications.Examples of application layer are applications such as file transfer, electronic mail, remote login etc.
OSI Model
OSI in ActionA message begins at the top application layer and moves down the OSI layers to the bottom physical layer. As the message descends, each successive OSI model layer adds a header to it. A header is layer-specific information that basically explains what functions the layer carried out. Conversely, at the receiving end, headers are striped from the message as it travels up the corresponding layers.
OSI Model
TCP/IP Model
TCP/IP MODEL
OSI & TCP/IP Models
TCP/IP Model
TCP/IP Model
TCP/IP Model
Application LayerApplication programs using the network
Transport Layer (TCP/UDP)Management of end-to-end message transmission,
error detection and error correction
Network Layer (IP)Handling of datagrams : routing and congestion
Data Link LayerManagement of cost effective and reliable data delivery,
access to physical networks
Physical LayerPhysical Media
Physical Media
PHYSICAL MEDIA
Physical Media
Physical Media
Physical MediaCopper
Coaxial Cable - Thick or ThinUnshielded Twisted Pair - CAT 3,4,5,5e&6
Optical FiberMultimodeSinglemode
WirelessShort RangeMedium Range (Line of Sight)Satellite
Physical Media
Copper Media: Coaxial CableCoaxial cable is a copper-cored cable surrounded by a heavy shielding and is used to connect computers in a network.Outer conductor shields the inner conductor from picking up stray signal from the air.High bandwidth but lossy channel.Repeater is used to regenerate the weakened signals.
Physical Media
Category Impedance Use
RG-59RG-59 75 Cable TV
RG-58RG-58 50 Thin Ethernet
RG-11RG-11 50 Thick Ethernet
Copper Media: Twisted PairTwisted-pair is a type of cabling that is used for telephone communications and most modern Ethernet networks. A pair of wires forms a circuit that can transmit data. The pairs are twisted to provide protection against crosstalk, the noise generated by adjacent pairs. There are two basic types, shielded twisted-pair (STP) and unshielded twisted-pair (UTP).
Physical Media
Shielded Twisted Pair (STP)
Physical Media
Unshielded Twisted Pair (UTP)
Physical Media
Unshielded Twisted Pair (UTP)Consists of 4 pairs (8 wires) of insulated copper wires typically about 1 mm thick.The wires are twisted together in a helical form. Twisting reduces the interference between pairs of wires.High bandwidth and High attenuation channel.Flexible and cheap cable.Category rating based on number of twists per inch and the material usedCAT 3, CAT 4, CAT 5, Enhanced CAT 5 and now CAT 6.
Physical Media
Categories of UTPUTP comes in several categories that are based on the number of twists in the wires, the diameter of the wires and the material used in the wires. Category 3 is the wiring used primarily for telephone connections.Category 5e and Category 6 are currently the most common Ethernet cables used.
Physical Media
Categories of UTP: CAT 3
Bandwidth 16 Mhz11.5 dB Attenuation100 ohms ImpedanceUsed in voice applications and 10baseT (10Mbps) Ethernet
Physical Media
Categories of UTP: CAT 4
20 MHz Bandwidth7.5 dB Attenuation100 ohms ImpedanceUsed in 10baseT (10Mbps) Ethernet
Physical Media
Categories of UTP: CAT 5
100 MHz Bandwidth24.0 dB Attenuation100 ohms ImpedanceUsed for high-speed data transmissionUsed in 10BaseT (10 Mbps) Ethernet & Fast Ethernet (100 Mbps)
Physical Media
Categories of UTP: CAT 5e
150 MHz Bandwidth24.0 dB Attenuation100 ohms ImpedanceTransmits high-speed dataUsed in Fast Ethernet (100 Mbps), Gigabit Ethernet (1000 Mbps) & 155 Mbps ATM
Physical Media
Categories of UTP: CAT 6
250 MHz Bandwidth19.8 dB Attenuation100 ohms ImpedanceTransmits high-speed dataUsed in Gigabit Ethernet (1000 Mbps) & 10 Gig Ethernet (10000 Mbps)
Physical Media
Fiber Media
Optical fibers use light to send information through the optical medium.It uses the principal of total internal reflection.Modulated light transmissions are used to transmit the signal.
Physical Media
Total Internal Reflection
Physical Media
Fiber MediaLight travels through the optical media by the way of total internal reflection. Modulation scheme used is intensity modulation.Two types of Fiber media :
MultimodeSinglemode
Multimode Fiber can support less bandwidth than Singlemode Fiber.Singlemode Fiber has a very small core and carry only one beam of light. It can support Gbps data rates over > 100 Km without using repeaters.
Physical Media
Single and Multimode FiberSingle-mode fiber
Carries light pulses along single pathUses Laser Light Source
Multimode fiberMany pulses of light generated by LED travel at different angles
Physical Media
Fiber MediaThe bandwidth of the fiber is limited due to the dispersion effect.Distance Bandwidth product of a fiber is almost a constant.Fiber optic cables consist of multiple fibers packed inside protective covering.62.5/125 µm (850/1310 nm) multimode fiber 50/125 µm (850/1310 nm) multimode fiber 10 µm (1310 nm) single-mode fiber
Physical Media
Fiber-Optic CableContains one or several glass fibers at its coreSurrounding the fibers is a layer called cladding
Physical Media
Fiber Optic CableFO Cable may have 1 to over 1000 fibers
Physical Media
Wireless MediaVery useful in difficult terrain where cable laying is not possible.Provides mobility to communication nodes.Right of way and cable laying costs can be reduced.Susceptible to rain, atmospheric variations and Objects in transmission path.
Physical Media
Wireless MediaIndoor : 10 – 50m : BlueTooth, WLAN
Short range Outdoor : 50 – 200m: WLAN
Mid Range Outdoor : 200m – 5 Km : GSM, CDMA, WLAN Point-to-Point, Wi-Max
Long Range Outdoor : 5 Km – 100 Km : Microwave Point-to-Point
Long Distance Communication : Across Continents : Satellite Communication
Physical Media
Frequency BandsFrequency Bands
Physical Media
BandBand RangeRange PropagatioPropagationn ApplicationApplication
VLFVLF 3–30 KHz Ground Long-range radio navigation
LFLF 30–300 KHz Ground Radio beacons andnavigational locators
MFMF 300 KHz–3 MHz Sky AM radio
HF HF 3–30 MHz Sky Citizens band (CB),ship/aircraft communication
VHF VHF 30–300 MHz Sky andline-of-sight
VHF TV, FM radio
UHF UHF 300 MHz–3 GHz Line-of-sight
UHF TV, cellular phones, paging, satellite
SHF SHF 3–30 GHz Line-of-sight Satellite communication
EHFEHF 30–300 GHz Line-of-sight Long-range radio navigation
Wireless LAN
Physical Media
Internet Router Switch
Access Point
Access Point
PC
PC
Terrestrial MicrowaveMicrowaves do not follow the curvature of earthLine-of-Sight transmissionHeight allows the signal to travel fartherTwo frequencies for two way communicationRepeater is used to increase the distance Hop-by-Hop
Physical Media
Satellite Communication
Physical Media
Cabling
UTP AND FIBER CABLING
Structured Cabling InfrastructureMounted and permanentAllows patchingComfort that infrastructure is OKComponents:
Information Outlet with Face PlatePatch PanelUTP CablePatch Cord
Cabling
I/O & FaceplatesFaceplate mounts on or in wall or in racewaySingle or Dual Information Outlet (I/O)Provide network connectivity to the Hosts through a Patch Cord
Cabling
Patch PanelTermination punchdown in backPatch cord plugin in front
Cabling
Patch Cord & UTP Connectors
Cabling
Color CodesData Tx: 1 & 2 Data Rx: 3 & 6Crossover
1 32 6
PoE +VDC: 4 & 5 PoE -VDC: 7 & 8
Cabling
Cutting, Striping & Crimping ToolsMake your own patch cordsCuts and strips pairsRJ45 end crimped onto ends of wire
Cabling
Punching ToolTerminates wires to back of patch panels and in Information Outlets
Cabling
Making Cables
Cabling
Wire Testing EquipmentTest wire for correct termination of 8 wiresTest for speed capabilities
Cabling
Cabling RulesTry to avoid running cables parallel to power cables.Do not bend cables to less than four times the diameter of the cable.If you bundle a group of cables together with cable ties (zip ties), do not over-cinch them. You should be able to turn the tie with fingers.Keep cables away from devices which can introduce noise into them. Here's a short list: copy machines, electric heaters, speakers, printers, TV sets, fluorescent lights, copiers, welding machines, microwave ovens, telephones, fans, elevators, motors, electric ovens, dryers, washing machines, and shop equipment.Avoid stretching UTP cables (tension when pulling cables should not exceed 25 LBS).Do not run UTP cable outside of a building. It presents a very dangerous lightning hazard!Do not use a stapler to secure UTP cables. Use telephone wire/RJ6 coaxial wire hangers which are available at most hardware stores.
Cabling
Fiber Optic Cabling Infrastructure
Components:Fiber Cable Fiber PigtailFiber ConnectorsLIUCouplerFiber Patch Cord
Cabling
Fiber Optic ConnectorsTerminates the fibersConnects to other fibers or transmission equipment
Cabling
Fiber Patch Cords & PigtailsEnds are typically either SC or STPigtails have connectors on only one side and Patch Cords have it on both sides.Pigtails are spliced to the fiber to terminate the fiberPatch Cord connects switches to the Fiber cable
Cabling
LIU & Couplers
Cabling
Fiber Optic Installation – Outside Plant
Cabling
Fiber Optic Installation – Outside Plant
Fiber is blown in HDPE Pipes, 1 m deep. The HDPE pipes is covered with sand and brick liningFiber Roles are typically 2 Km. Fiber cables are spliced using JointersFaults like fiber cut are located using OTDR (Optical Time Domain Reflectometer)
Cabling
LAN Technologies
LAN TECHNOLOGIES
Technology OptionsEthernetFast EthernetGigabit Ethernet10 Gig Ethernet
WLAN
LAN Technologies
Media AccessEthernet and Wi-Fi are both “multi-access” technologies
Broadcast medium, shared by many hostsSimultaneous transmissions will result in collisions
Media Access Control (MAC) protocol requiredRules on how to share medium
The Data Link Layer is divided into two Part MAC Media Access Control) Sublayer and LLC (Logic Link Control) Sublayer
LAN Technologies
802.3 EthernetCarrier-sense multiple access with collision detection (CSMA/CD).
CS = carrier sense MA = multiple accessCD = collision detection
Base Ethernet standard is 10 Mbps.100Mbps, 1Gbps, 10Gbps standards came later
LAN Technologies
Ethernet CSMA/CDCSMA/CD (carrier sense multiple access with collision detection) media access protocol is used.
Data is transmitted in the form of packets. Sense channel prior to actual packet transmission.Transmit packet only if channel is sensed idle; else, defer the transmission until channel becomes idle.After packet transmission is started, the node monitors its own transmission to see if the packet has experienced a collision.If the packet is observed to be undergoing a collision, the transmission is aborted and the packet is retransmitted after a random interval of time using Binary Exponential Backoff algorithm.
LAN Technologies
Ethernet AddressEnd nodes are identified by their Ethernet Addresses (MAC Address or Hardware Address) which is a unique 6 Byte address.
MAC Address is represented in Hexa Decimal format e.g 00:05:5D:FE:10:0A
The first 3 bytes identify a vendor (also called prefix) and the last 3 bytes are unique for every host or device
LAN Technologies
Ethernet Frame StructurePreamble:
7 bytes with pattern 10101010 followed by one byte with pattern 10101011Used to synchronize receiver, sender clock rates
Addresses: 6 bytes, frame is received by all adapters on a LAN and dropped if address does not matchLength: 2 bytes, length of Data fieldCRC: 4 bytes generated using CR-32, checked at receiver, if error is detected, the frame is simply droppedData Payload: Maximum 1500 bytes, minimum 46 bytes
If data is less than 46 bytes, pad with zeros to 46 bytes
LAN Technologies
Length
Ethernet10 Base 5 (Thicknet) (Bus Topology)10 Base 2 (Thinnet) (Bus Topology)10 Base T (UTP) (Star/Tree Topology)10 Base FL (Fiber) (Star/Tree Topology)
LAN Technologies
Ethernet BUS Topology
LAN Technologies
Repeater
Ethernet STAR Topology
LAN Technologies
Hub
EthernetPhysical Media :-
10 Base5 - Thick Co-axial Cable with Bus Topology 10 Base2 - Thin Co-axial Cable with Bus Topology 10 BaseT - UTP Cat 3/5 with Tree Topology 10 BaseFL - Multimode/Singlemode Fiber with Tree
Topology
Maximum Segment Length 10 Base5 - 500 m with at most 4 repeaters (Use Bridge to extend the network) 10 Base2 - 185 m with at most 4 repeaters (Use Bridge to extend the network) 10 BaseT - 100 m with at most 4 hubs (Use Switch to extend the network)
LAN Technologies
Fast Ethernet100 Mbps bandwidthUses same CSMA/CD media access protocol and packet format as in Ethernet.100BaseTX (UTP) and 100BaseFX (Fiber) standards Physical media :-
100 BaseTX - UTP Cat 5e100 BaseFX - Multimode / Singlemode Fiber
Full Duplex/Half Duplex operations.
LAN Technologies
Fast EthernetProvision for Auto-Negotiation of media speed: 10 Mbps or 100Mbps (popularly available for copper media only).
Maximum Segment Length100 Base TX - 100 m100 Base FX - 2 Km (Multimode Fiber)100 Base FX - 20 km (Singlemode Fiber)
LAN Technologies
Gigabit Ethernet1 Gbps bandwidth.Uses same CSMA/CD media access protocol as in Ethernet and is backward compatible (10/100/100 modules are available).1000BaseT (UTP), 1000BaseSX (Multimode Fiber) and 1000BaseLX (Multimode/Singlemode Fiber) standards.Maximum Segment Length
1000 Base T - 100m (Cat 5e/6)1000 Base SX - 275 m (Multimode Fiber)1000 Base LX - 512 m (Multimode Fiber) 1000 Base LX - 20 Km (Singlemode Fiber)1000 Base LH - 80 Km (Singlemode Fiber)
LAN Technologies
10 Gig Ethernet10 Gbps bandwidth.
Uses same CSMA/CD media access protocol as in Ethernet.
Propositioned for Metro-Ethernet
Maximum Segment Length1000 Base-T - Not available10GBase-LR - 10 Km (Singlemode Fiber)10GBase-ER - 40 Km (Singlemode Fiber)
LAN Technologies
802.11 Wireless LAN
Provides network connectivity over wireless media
An Access Point (AP) is installed to act as Bridge between Wireless and Wired Network
The AP is connected to wired network and is equipped with antennae to provide wireless connectivity
LAN Technologies
Network connectivity
to the legacy
wired LAN
Desktop with PCI 802.11 LAN card
Laptop with PCMCIA 802.11 LAN card
Access Point
802.11 Wireless LANRange ( Distance between Access Point and WLAN client) depends on structural hindrances and RF gain of the antenna at the Access Point
To service larger areas, multiple APs may be installed with a 20-30% overlap
A client is always associated with one AP and when the client moves closer to another AP, it associates with the new AP (Hand-Off)
Three flavors:802.11b802.11a802.11g
LAN Technologies
Multiple Access with Collision Avoidance (MACA)
Before every data transmission Sender sends a Request to Send (RTS) frame containing the length of the transmissionReceiver respond with a Clear to Send (CTS) frameSender sends dataReceiver sends an ACK; now another sender can send data
When sender doesn’t get a CTS back, it assumes collision
LAN Technologies
sender receiverother node in sender’s range
RTSCTS
ACK
data
other node in receiver’s range
WLAN : 802.11bThe most popular 802.11 standard currently in deployment.Supports 1, 2, 5.5 and 11 Mbps data rates in the 2.4 GHz ISM (Industrial-Scientific-Medical) band
LAN Technologies
WLAN : 802.11aOperates in the 5 GHz UNII (Unlicensed National Information Infrastructure) band Incompatible with devices operating in 2.4GHzSupports Data rates up to 54 Mbps.
LAN Technologies
WLAN : 802.11gSupports data rates as high as 54 Mbps on the 2.4 GHz bandProvides backward compatibility with 802.11b equipment
LAN Technologies
Repeater, HUB, Bridge & Switch
REPEATER, HUB, BRIDGE AND SWITCH
RepeaterA repeater receives a signal, regenerates it, and passes it on. It can regenerate and retime network signals at the bit level to allow them to travel a longer distance on the media.It operates at Physical Layer of OSIThe Four Repeater Rule for 10-Mbps Ethernet should be used as a standard when extending LAN segments. This rule states that 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.
Repeater, Hub, Bridge & Switch
HubHubs are used to connect multiple nodes to a single physical device, which connects to the network. Hubs are actually multiport repeaters.
Using a hub changes the network topology from a linear bus, to a star.
With hubs, data arriving over the cables to a hub port is electrically repeated on all the other ports connected to the same network segment, except for the port on which the data was sent.
Repeater, Hub, Bridge & Switch
BridgeBridges are used to logically separate network segments within the same network. They operate at the OSI data link layer (Layer 2) and are independent of higher-layer protocols. 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.
When a bridge receives a frame on the network, the destination MAC address is looked up in the bridge table to determine whether to filter, flood, or copy the frame onto another segment
Broadcast Packets are forwarded
Repeater, Hub, Bridge & Switch
SwitchSwitches are Multiport Bridges. Switches provide a unique network segment on each port, thereby separating collision domains. Today, network designers are replacing hubs in their wiring closets with switches to increase their network performance and bandwidth while protecting their existing wiring investments.Like bridges, switches learn certain information about the data packets that are received from various computers on the network. Switches use this information to build forwarding tables to determine the destination of data being sent by one computer to another computer on the network.
Repeater, Hub, Bridge & Switch
Switches: Dedicated AccessHosts have direct connection to switchFull Duplex: No collisionsSwitching: A-to-A’ and B-to-B’ simultaneously, no collisionsSwitches can be cascaded to expand the network
Repeater, Hub, Bridge & Switch
switch
A
A’
B
B’
C
C’
WAN Technologies
WAN TECHNOLOGIES
Technology OptionsDial-upLeased LineISDNX.25Frame RelayATMDSLCable ModemMicrowave Point-to-Point LinkVSAT
WAN Technologies
Dial-upUses POTS (Plain Old Telephone System)Provides a low cost need based access.Bandwidth 33.6 /56 Kbps.
On the Customer End: Modem is connected to a Telephone LineOn the Service Provider End: Remote Access Server (RAS) is connected to Telephone Lines (33.6 Kbps connectivity) or E1/R2 Line (56 Kbps connectivity)RAS provide dialin connectivity, authentication and metering.Achievable bandwidth depends on the line quality.
WAN Technologies
Dial-up
WAN Technologies
Dial-up
WAN Technologies
RAS
Dial-up
WAN Technologies
33.6 Kbps
Modem
Telephone switch
Telephone switch
Telephone switch ?
Access server
Modem
Modem
E1
Analog line
56 Kbps
Leased LineUsed to provide point-to-point dedicated network connectivity.Analog leased line can provide maximum bandwidth of 9.6 Kbps.Digital leased lines can provide bandwidths : 64 Kbps, 2 Mbps (E1), 8 Mbps (E2), 34 Mbps (E3) ...
WAN Technologies
Leased Line Internet Connectivity
WAN Technologies
ISP Broadba
nd Internet Connecti
vity
ISPRouter
Interface Converter
LL ModemG.703
LLModem
V.35Router
ISP PREMISES CUSTOMER PREMISES
PSTN
ISDNAnother alternative to using analog telephones lines to establish a connection is ISDN. Speed is one advantage ISDN has over telephone line connections. ISDN network is a switched digital network consisting of ISDN Switches.Each node in the network is identified by hierarchical ISDN address which is of 15 digits.ISDN user accesses network through a set of standard interfaces provided by ISDN User Interfaces.
WAN Technologies
ISDN
WAN Technologies
Two types of user access are defined Basic Access - Consists of two 64Kbps user channels (B channel) and one 16Kbps signally channel (D channel) providing service at 144 Kbps.Primary access - Consists of thirty 64Kbps user channels (B channels) and a 64 Kbps signally channel (D channel) providing service at 2.048Mbps (One 64 Kbps channel is used for Framing and Synchronization).
BasicB
BD
Information 128 Kbps(Voice & Data)
Signaling 16Kbps
Primary
B
B
D
Information 1920 KbpsVoice & Data
Signaling 64 Kbps
ISDN
WAN Technologies
TE1
TE2 TA
NT12W4W
ISDN devices
S/T interface U interface
DevicesNT1 - Interface ConverterTE1 - ISDN devicesTE2 – Non ISDN Devices (need TA)TA - Terminal Adapter (ISDN Modem)
X.25Packet switched Network consisting of X.25 switches.X.25 is a connection oriented protocol (Virtual Circuits).End nodes are identified by an X .25 address.Typical bandwidth offered is 2.4/9.6 kbps. IP networks interface with X .25 through IP- X.25 routers.
WAN Technologies
X.25 and Virtual Circuits
WAN Technologies
Frame RelayDesigned to be more efficient than X.25Developed before ATMCall control carried in separate logical connectionNo hop by hop error or flow controlEnd to end flow and error control (if used) are done by higher layerSingle user data frame sent from source to destination and ACK (from higher layer) sent backTwo type of Virtual Circuits defined
Permanent virtual circuits (PVCs) Switched virtual circuits (SVCs)
WAN Technologies
ATMSmall fixed size packets of 53 bytes, called cells, are used for transferring information.Each cell has 5 bytes of header and 48 bytes of payload for user information.Connection oriented protocol. A virtual Circuit is established between the communicating nodes before data transfer takes place.Can be seamlessly used in LANs and WANs.Almost unlimited scalability.Provides quality of service guaranties.
WAN Technologies
Digital Subscriber Line (DSL)Digital Subscriber Line (DSL) uses the Ordinary Telephone line and is an always-on technology. This means there is no need to dial up each time to connect to the Internet.Because DSL is highly dependent upon noise levels, a subscriber cannot be any more than 5.5 kilometers (2-3 miles) from the DSL ExchangeService can be symmetric, in which downstream and upstream speeds are identical, or asymmetric in which downstream speed is faster than upstream speed.DSL comes in several varieties:
Asymmetric DSL (ADSL)High Data Rate DSL (HDSL) Symmetric DSL (SDSL) Very High Data Rate DSL (VDSL)
WAN Technologies
ADSL
WAN Technologies
Cable ModemsThe cable modem connects a computer to the cable company network through the same coaxial cabling that feeds cable TV (CATV) signals to a television set.Uses Cable Modem at Home End and CMTS (Cable Modem Termination System) at Head End.Characteristics:
Shared bandwidth technology 10 Mbps to 30 Mbps downstream 128Kbps-3 Mbps upstream Maximum Distance from provider to customer site: 30 miles
WAN Technologies
Cable Modems
WAN Technologies
Point-to-Point Microwave Link
WAN Technologies
ISP Network
NetworkRFModemRouter
RFModem Router
MICROWAVE LINK
ISP PREMISESCUSTOMER PREMISES
Point-to-Point Microwave LinkTypically 80-100 MHz Band or 5 GHz Radio Link band2.4 GHz WiFi links are becoming popularRequires Line of Sight
WAN Technologies
VSATVery Small Aperture Terminal (VSAT) provide communication between two nodes through a powerful Earth station called a Hub.If two terminals want to communicate, they send their messages to the satellite, which sends it to the Hub and the Hub then broadcasts the message through the satellite.Typical Bandwidth offered is 9.6/19.2/32/64/128/256/512 Kbps.Operating modes are TDM/TDMA, SCPC PAMA & DAMA
WAN Technologies
VSATEach satellite sends and receives over two bands
Uplink: From the earth to the satelliteDownlink: From the satellite to the earth
Satellite frequency bandsBand Downlink UplinkC 3.7-4.2 GHz 5.925-6.425
GHzKu 11.7-12.2 GHz 14-14.5 GHz
Ku-band based networks, are used primarily in Europe and North America and utilize the smaller sizes of VSAT antennas.C-band, used extensively in Asia, Africa and Latin America, require larger antenna.
WAN Technologies
Internet Protocol
INTERNET PROTOCOL
IP as a Routed ProtocolIP is a connectionless, unreliable, best-effort delivery protocol. IP accepts whatever data is passed down to it from the upper layers and forwards the data in the form of IP Packets.All the nodes are identified using an IP address. Packets are delivered from the source to the destination using IP address
Internet Protocol
Packet Propagation Internet Protocol
IP AddressIP address is for the INTERFACE of a host. Multiple interfaces mean multiple IP addresses, i.e., routers.
32 bit IP address in dotted-decimal notation for ease of reading, i.e., 193.140.195.66
Address 0.0.0.0, 127.0.0.1 and 255.255.255.255 carries special meaning.
IP address is divided into a network number and a host number.
Also bits in Network or Host Address cannot be all 0 or 1.
Internet Protocol
IP Address
Internet Protocol
IP Address
Internet Protocol
IP AddressClass A : Address begins with bit 0. It has 8 bit network number (range 0.0.0.0-to-127.255.255.255), 24 bit host number.Class B : Address begins with bits 10. It has 16 bit network number (range 128.0.0.0-to-191.255.255.255), 16 bit host number.Class C : Address begins with bits 110. It has 24 bit network number (range 192.0.0.0-to-223.255.255.255), 8 bit host number.Class D : Begins with 1110, multicast addresses (224.0.0.0-to-239.255.255.255)Class E : Begins with 11110, unused
Internet Protocol
Subnet Mask
Internet Protocol
Consider IP address = 192.168.2.25First few bits (left to right) identify network/subnet Remaining bits identify host/interface
Number of subnet bits is called subnet mask, e.g.
Subnet IP Address range is 192.168.2.0 – 192.168.2.255 or Mask = 255.255.255.0
Subnet IP Address range is 192.168.2.0 – 192.168.2.15 or Mask = 255.255.255.240
IP Address, Subnet Mask and Gateway
IP Address and Subnet Mask define the SubnetFor Example IP address 172.31.1.0 and Subnet Mask of 255.255.240.0 means that the subnet address ranges from 172.31.0.0 to 172.31.15.255Another notation is 172.31.1.0/28The first Address is the Network Address and the last Address is the Broadcast Address. They are reserved and cannot be assigned to any node.The Gateway Address is the Address of the router where the packet should be sent in case the destination host does not belong to the same subnet
Internet Protocol
IP Configuration of an Interface
Internet Protocol
Static DHCP
ARPARP (Address Resolution Protocol) is used in Ethernet Networks to find the MAC address of a node given its IP address.
Source node (say 192.168.2.32) sends broadcast message (ARP Request) on its subnet asking ``Who is 192.168.2.33’’.
All computers on subnet receive this request
Destination responds (ARP Reply) since it has 192.168.2.33
Provides its MAC address in response
Internet Protocol
IPv6Internet Protocol Version 4 is the most popular protocol in use today, although there are some questions about its capability to serve the Internet community much longer. IPv4 was finished in the 1970s and has started to show its age. The main issue surrounding IPv4 is addressing—or, the lack of addressing—because many experts believe that we are nearly out of the four billion addresses available in IPv4. Although this seems like a very large number of addresses, multiple large blocks are given to government agencies and large organizations. IPv6 could be the solution to many problems posed by IPv4
Internet Protocol
IPv6IPv6 uses 128 bit address instead of 32 bit address.
The IPv6 addresses are being distributed and are supposed to be used based on geographical location.
Internet Protocol
Routing
ROUTING
RouterA router is a device that determines the next network point to which a packet should be forwarded toward its destinationAllow different networks to communicate with each otherA router creates and maintain a table of the available routes and their conditions and uses this information to determine the best route for a given packet.A packet will travel through a number of network points with routers before arriving at its destination.There can be multiple routes defined. The route with a lower weight/metric will be tried first.
Routing
Routing
Routing
Routing ProtocolsStatic RoutingDynamic Routing
IGP (Interior Gateway Protocol): Route data within an Autonomous System
RIP (Routing Information Protocol)RIP-2 (RIP Version 2)OSPF (Open Shortest Path First)IGRP (Interior Gateway Routing Protocol)EIGRP (Enhanced Interior Gateway Routing Protocol)IS-IS
EGP (Exterior Gateway Protocol): Route data between Autonomous Systems
BGP (Border Gateway Protocol)
Routing
Internetworking Devices
Internetworking Devices
Device Description
Hub Hubs are used to connect multiple users to a single physical device, which connects to the network. Hubs and concentrators act as repeaters by regenerating the signal as it passes through them.
Bridge Bridges are used to logically separate network segments within the same network. They operate at the OSI data link layer (Layer 2) and are independent of higher-layer protocols.
Switch Switches are similar to bridges but usually have more ports. Switches provide a unique network segment on each port, thereby separating collision domains. Today, network designers are replacing hubs in their wiring closets with switches to increase their network performance and bandwidth while protecting their existing wiring investments.
Router Routers separate broadcast domains and are used to connect different networks. Routers direct network traffic based on the destination network layer address (Layer 3) rather than the workstation data link layer or MAC address.
VLAN
VLAN
VLANsVLANs (Virtual LAN) enable network managers to group users logically (based on functions, project teams or applications) rather than by physical location.
Traffic can only be routed between VLANs.
VLANs provide the segmentation traditionally provided by physical routers in LAN configuration.
VLAN
VLANs and Inter VLAN Routing
VLAN
Advantages of Using VLANsBroadcast Control— Just as switches physically isolate collision domains for attached hosts and only forward traffic out a particular port, VLANs provide logical bridging domains that confine broadcast and multicast traffic to the VLANs.
Security— If you do not allow routing in a VLAN, no users outside of that VLAN can communicate with the users in the VLAN and vice versa. This extreme level of security can be highly desirable for certain projects and applications.
Performance— You can assign users that require high-performance or isolated networking to separate VLANs.
VLAN
TCP/UDP
TCP/UDP
TCP/UDPTransport Layer ProtocolTCP is connection Oriented (uses checksum and acknowledgment)UDP is ConnectionlessBoth use the concept of Connection Port Number (16 Bit Source Port Number and Destination Port Number)Standard Applications have standard Port Numbers (Email 25, Telnet 23, FTP 20 & 21, SSH 22)
TCP/UDP
Natting
NATTING
Private vs Public IP AddressesWhatever connects directly into Internet must have public (globally unique) IP addressThere is a shortage of public IPv4 addressSo Private IP addresses can be used within a private networkThree address ranges are reserved for private usage
10.0.0.0/8172.16.0.0/16 to 172.31.0.0/16192.168.0.0/24 to 192.168.255.0/24
A private IP is mapped to a Public IP, when the machine has to access the Internet
Natting
NATNAT (Network Address Translation) Maps Private IPs to Public IPs
It is required because of shortage of IPv4 Address
Natting
H1
Router/NAT
H2
10.0.1.3
10.0.1.1
10.0.1.2
H3
Router/NAT
H4
10.0.1.310.0.1.2
Private network 2Internet
H5
10.0.1.1Private network 1
128.195.4.119 128.143.71.21
213.168.112.3
NATStatic NAT : Maps unique Private IP to unique Public IP
Dynamic NAT : Maps Multiple Private IP to a Pool of Public IPs (Port Address Translation : Maps a Public IP and Port Number to a service in Private IP)
Natting
H1
Private address: 10.0.1.2
Private network
Source = 10.0.1.2Source port = 2001
Source = 128.143.71.21Source port = 3200
NAT
H2
Private address: 10.0.1.3
Source = 10.0.1.3Source port = 1090
Internet
Source = 128.143.71.21Destination = 4444
128.143.71.21
SNMP
SNMP
Simple Network Management Protocol
SNMP is a framework that provides facilities for managing and monitoring network resources on the Internet. Components of SNMP:
SNMP agentsSNMP managersManagement Information Bases (MIBs)SNMP protocol itself
SNMP
SNMP agentSNMP
manager
SNMP agent
SNMP agent
SNMPprotocol
messages
SNMPSNMP is based on the manager/agent model consisting of a manager, an agent, a database of management information, called as MIB. The manager provides the interface between the human network manager and the management system. The agent provides the interface between the manager and the physical device(s) being managed.
SNMP
SNMPSNMP uses five basic messages (GET, GET-NEXT, GET-RESPONSE, SET, and TRAP) to communicate between the manager and the agent. The GET and GET-NEXT messages allow the manager to request information for a specific variable. The agent, upon receiving a GET or GET-NEXT message, will issue a GET-RESPONSE message to the manager with either the information requested or an error indication as to why the request cannot be processed. A SET message allows the manager to request a change be made to the value of a specific variable in the case of an alarm remote that will operate a relay. The agent will then respond with a GET-RESPONSE message indicating the change has been made or an error indication as to why the change cannot be made. The TRAP message allows the agent to spontaneously inform the manager of an ‘important’ event.
SNMP
VPN
VPN
VPNVPN is a private connection between two systems or networks over a shared or public network (typically Internet).VPN technology lets an organization securely extend its network services over the Internet to remote users, branch offices, and partner companies. In other words, VPN turns the Internet into a simulated private WAN.VPN is very appealing since the Internet has a global presence, and its use is now standard practice for most users and organizations.
VPN
VPN
VPN
How VPN WorksTo use the Internet as a private Wide Area Network, organizations may have to address two issues :
First, networks often communicate using a variety of protocols, such as IPX and NetBEUI, but the Internet can only handle TCP/IP traffic. So VPN may need to provide a way to pass non-TCP/IP protocols from one network to another.
Second data packets traveling the Internet are transported in clear text. Therefore, anyone who can see Internet traffic can also read the data contained in the packets. This is a problem if companies want to use the Internet to pass important, confidential business information.
VPN
How VPN WorksVPN overcome these obstacles by using a strategy called Tunneling. Instead of packets crossing the Internet out in the open, data packets are fist encrypted for security, and then encapsulated in an IP packet by the VPN and tunneled through the Internet.The VPN tunnel initiator on the source network communicates with a VPN tunnel terminator on the destination network. The two agree upon an encryption scheme, and the tunnel initiator encrypts the packet for security.
VPN
Advantages of Using VPNVPN technology provides many benefits. Perhaps the biggest selling point for VPN is cost savings. One can avoid having to purchase expensive leased lines to branch offices or partner companies. On another cost-related note, you can evade having to invest in additional WAN equipment and instead leverage your existing Internet installation.
Another benefit of VPN is that it is an ideal way to handle mobile users.
VPN
Enterprise Network
ENTERPRISE NETWORK IMPLEMENTATION
Small Office NetworkUse Unmanaged 10/100 SwitchesUse Enhanced Cat 5 Pathcords
Enterprise Network
Campus Network ArchitectureEnterprise Network
Internet
Server Farm
Backbone Switch
Access Switch
Distribution Switch
Firewall
Campus Network ArchitectureUses Three Tier Switching Architecture (Popularly known as Cisco’s Switching Architecture)Backbone Switch
Layer 3/4 Chassis based switchMultiple 100Fx or 1000SX/LX or 10GLX/LH ports for connectivity to Distribution switchesMultiple 10/100/1000 ports for connectivity to Servers
Distribution SwitchLayer 2/3 Managed Fixed configuration switch1/2 100Fx or 1000Sx/Lx or 10GLX/LH ports for connectivity to the Backbone switchMultiple 10/100 or 10/100/1000 ports for connectivity to the Access switches
Access SwitchLayer2 Managed/Unmanaged Fixed configuration switchMultiple 10/100 or 10/100/1000 ports for desktop connectivity
Enterprise Network
Campus Network CablingCampus backbone cabling—This is typically single- or multimode cable that interconnects the central campus Backbone Switch with each of the building Distribution Switches. Typically Ring Architecture is used to connect the Backbone switch to the Distribution switch to provide redundant routes.
Building backbone cabling—This is typically Category 5e or 6 UTP cable that interconnects the building distributor with each of the floor distributors in the building. Horizontal cabling—This is predominantly Category 5e or 6 UTP cabling.
Enterprise Network
DistributionSwitch
DistributionSwitch
DistributionSwitch
Backbone Switch
Backbone Switch
DistributionSwitch
DistributionSwitch
DistributionSwitch
Backbone Switch
DistributionSwitch
DistributionSwitch
DistributionSwitch
Campus NetworkThe residential connectivity can be provided on Ethernet/Dial-up/ADSL.The Internet connectivity can be provided on leased line.
Enterprise Network
Enterprise WAN ArchitectureA typical scenario will have Corporate Headquarter connected to Remote Offices (Branch Offices, Retail Counters etc.)The Remote offices would be interconnected to the corporate office through
A dedicated network implemented over Leased-Lines and/or IPLC (International Private Leased Circuit) (Microsoft, IBM, Cisco, Infosys etc.)A dedicated network implemented over VSAT (Banks’ ATM Network, Reserve Bank network, BSE Online Trading, NSE Online Trading etc.) VPNs on the Internet (Asian Paint Supplier Network, Bajaj Auto Retail Network etc.)A mix of above technologies
The backup links may provided through Redundant route through an alternate leased lineDial backup on ISDN (The Head Office has a PRI connectivity and the Remote offices have BRI connectivity)
Enterprise Network
Enterprise WAN ArchitectureThe Disaster Recovery site would be connected through multiple links to the main site VoIP infrastructure may be available (A Call Manager will be placed at the Head Office and VoIP phones would be available in all the offices)The NOC (Network Operation Center) may be at the Head Quarter (Infosys) or at a remote site (Reliance, Microsoft)The NOC maintains, monitors and manages the network and application servers. The Data exchange between offices may be through the servers at NOC to ensure security
Enterprise Network
Enterprise WAN Network
Enterprise Network
Enterprise WAN Network
Enterprise Network
Enterprise WAN
Enterprise Network
Server Farm
Service Provider Network
All the locations are connected through a Service Provider Networkover MPLS Backbone
Branch Office
Branch Office
Branch Office
Corporate Head Office
Service Provider Networks: RelianceReliance Data Centers, are connected to 132 countries across 4 continents spanning US, UK, Mid-east and Asia-Pac through Flag Telecom backbone (Reliance Infocomm 's group company) and other undersea cable systems like Se-Me-Wea-3 and i2i and are having public / private peering relationship with large Tier 1 ISPs and content providers at more than 15 Internet Exchange points across the globe. There also exists peering relationship with other popular domestic ISPs on STM-1 bandwidth levels.The data centers further are connected to Reliance's country wide optic fiber based IP network with terabytes of capacity having points of presence at more than 1100 cities. Customers' can access the Internet by connecting to any of these 1100 PoPs using multiple means like local dedicated leased lines, PSTN -ISDN dialup links OR simply by using Reliance's 3G CDMA mobile services.The Reliance Data Centers at various locations are also interconnected through redundant fiber ring with bandwidth capacity of STM-4 for data replication purposes for providing Disaster Recovery services.
Enterprise Network
Service Provider Networks: Reliance
Enterprise Network
Service Provider Networks: Reliance
Enterprise Network
Service Provider Networks
Enterprise Network
• Customers connect to an ISP
• ISPs connect to backbone
Backbonenetworks
ISP networ
k
ISP networ
k
ISPnetwork
Customer Networks
Bandwidth-limitedlinks
Service Provider Networks: FLAG
Enterprise Network
http://www.flagtelecom.com/Global_network.swf
Cisco Devices
CONFIGURING CISCO SWITCH AND ROUTER
Cisco’s LAN Switches
Cisco Devices
Cisco’s Routers
Cisco Devices
Hardware Components
Cisco Devices
Depending on the model/series (at least)Mother Board/Back PlaneCPU (RISC - MIPS or Motorola)MemoryBusI/O interfaces/Modules
Memory Components
Cisco Devices
Flash Memory – Holds the IOS; is not erased when the router is reloaded; is an EEPROM [Electrically Erasable Programmable Read-Only Memory] created by Intel, that can be erased and reprogrammed repeatedly through an application of higher than normal electric voltageNVRAM – Non-Volatile RAM - holds router configuration; is not erased when router is reloadedRAM – Holds packet buffers, ARP cache, routing table, software and data structure that allows the router to function; running-config is stored in RAM, as well as the decompressed IOS in later router modelsROM – Starts and maintains the router
What is IOS?
Cisco Devices
Internetwork Operating System
Operating System of all Cisco Devices
A derivative of BSD UNIX
Custom built by Cisco for each platform
Pre-packaged and static. Complete IOS is upgraded.
Features available in different versions (for a price!)
GUI’s available, but 90%+ of users still prefer command-line configuration.
IOS is designed to be hardware independent.
Configuring Cisco Devices
Cisco Devices
Provides Command Line Interface (CLI) and HTTP interface
HTTP Interface may be an extention of CLI
CLI can be accessed using Consol Port (through Hyper Terminal) or by Telnetting the device
Configuring Cisco Devices
Cisco Devices
Two modes of Operation :
Consol Mode : Only Status can be monitored
Enable Mode : Configuration can be changed and seen
Router> enable (disable)
Router#
CLI Commands
Cisco Devices
Exhaustive Command List
Type help or ? to see list of commands
Type command ? to see the possible command options
Commands can be auto-completed using TAB
Up-Arrow, Down-Arrow can be used to see command history
Abbreviations of Commands can be used
Show Configuration
Cisco Devices
sh run : To see running configuration
sh conf : To see saved configuration
Save Configuration
Cisco Devices
wr mem
Configuration Mode
Cisco Devices
conf t
Disable or Delete the Configuration
Cisco Devices
Use “no” before the configuration line
General Commands
Cisco Devices
hostname
ip default-gateway
ip name-server
ip routing
ip route
ip multicast-routing
banner
Interface Configuration Commands
Cisco Devices
Interfaces are named by type and position; e.g.:ethernet0, ethernet1/0,... Fastethernet0,fastethernet1/0,… gigabitethernet0,gigabitethernet1/0serial0, serial1 ... serial3/1
Can be abbreviated:ethernet0 or eth0 or e0serial0 or ser0 or s0
IP address and netmask configuration, status configuration etc. are done using interface commands:
router#config terminalrouter(config)#interface e0router(config-if)#ip address 195.176.118.254 255.255.255.0router(config-if)#exitrouter#
Interface Commands
Cisco Devices
ip address < ip address > < netmask >
ip address < ip address > < netmask > secondary
duplex full/half/auto
speed 10/100/1000/auto
bandwidth < bandwidth in kbps >
description < interface description >
shutdown
encapsultaion hdlc/ppp
Static Routing Commands
Cisco Devices
ip route <network address> <netmask> <gateway router address>
ip route 172.16.20.0 255.255.255.0 172.16.10.2
ip default-gateway < default gateway router address>
ip default-gateway 172.16.10.1
ip route 0.0.0.0 0.0.0.0 172.16.10.1
Backup & Restore Configuration
Cisco Devices
Copy (from cisco device to tftp server and vice-versa)
copy startup-config tftp (it will ask the tftp server ip address and destination filename)
copy tftp startup-config (it will ask the tftp server ip address and destination filename)
Static NAT Commands
Cisco Devices
ip nat inside (on the port where you have private IP)
ip nat outside (on the port where you have public IP)
ip nat inside source static <private ip> <public ip> (global command)
NAT Pool Commands
Cisco Devices
ip nat inside (on the port where you have private IP)
ip nat outside (on the port where you have public IP)
ip nat pool <name of the nat pool> <starting ip address> <last ip address> <netmask of the public ip addresses> (global command)
ip nat inside source list 1 pool <name of the nat pool> overload (global command)
access-list 1 permit <private ip> (global command)
Diagnostic Commands
Cisco Devices
ping
traceroute
General Monitoring and Administration Commands
Cisco Devices
reload
sh ver
sh int
Upgrading Cisco IOS
Cisco Devices
Download and install TFTP server (http://www.download.com)Download Cisco IOS Software Image to be upgradedCopy this image in the outbound directory of TFTP serverEstablish a Console or Telnet session with the routerUse sh flash command to check that you have enough space in flash to install the new imageBackup the existing IOS image on the TFTP server using the command copy flash tftp (it will ask the tftp server ip address and source and destination filename)Copy the new IOS image from TFTP server to the flash using the command copy tftp flash (it will ask for the tftp server ip address and source and destination filename)Reboot the Router
Internet Applications
INTERNET APPLICATIONS
Internet Applications
Internet Applications
Domain Name Service
Proxy Service
Mail Service
Web Service
DNS
DNS
Internet Naming Hierarchy
DNS
The silent dot at theend of all addresses
.com .net .org .in
.tcd
www
.ac .co
.iitk
www
DNS OperationDNS Setup
A DNS server maintains the name to IP address mapping of the domain for which it is the name server.The DNS server for a domain is registered with the domain registrar and the entry is maintained by the Internet Root-Servers (13) or Country Level Root-Servers.Whenever a server is queried, if doesn’t have the answer, the root servers are contacted.The root servers refer to the DNS server for that domain (in case the domain is a top level domain) or the Country Root Server (in case the domain is country level domain).
Proxy Server
PROXY SERVER
Internet Connections
Proxy Server
• Customers connect to an ISP
• ISPs connect to backbone
Backbonenetworks
ISP networ
k
ISP networ
k
ISPnetwork
Customer Networks
Bandwidth-limitedlinks
Internet Connections
Proxy Server
Cost of connections is based on bandwidth
Cost of connection is a major part of network cost
Organisations only obtain as much bandwidth as they can afford
Many organisations in Asia-Pacific only have 64kb/s – 2Mb/s connections (as compared to their counterpart in US and Europe who have bandwidths of 2.4 Gbps – 10 Gbps)
What is a Web Proxy?
Proxy Server
A proxy is a host which relays web access requests from clients
Used when clients do not access the web directly
Used for security, logging, accounting and performance
browser proxy web
What is Web Caching?Storing copies of recently accessed web pages
Pages are delivered from the cache when requested again
Browser caches
Proxy caches
Proxy Server
Why Cache?Shorter response time
Reduced bandwidth requirement
Reduced load on servers
Access control and logging
Proxy Server
Popular Proxy CachesApache proxy
MS proxy server
WinProxy
Squid
Squid is popular because it is powerful, configurable and free
Many others
Proxy Server
Web Server
WEB SERVER
Web ServerHTTP (Hyper Text Transfer Protocol) is used to transfer web pages from a Web Server to Web Client (Browser)Web Pages are arranged in a directory structure in the Web ServerHTTP supports CGI (Common Gateway interface)HTTP supports Virtual Hosting (Hosting multiple sites on the same server)Popular Web Servers
ApacheWindows IISIBM Websphere
Web Server
Mail Architecture
Internet
Mail Server
Mail Server
Mail ClientMail Client
Mail Architecture
Mail Architecture
Simple Mail Transfer Protocol (SMTP) is used to transfer mail between Mail Servers over Internet
Post Office Protocol (PoP) and Interactive Mail Access Protocol (IMAP) is used between Client and Mail Server to retrieve mails
The mail server of a domain is identified by the MX record of that domain
Popular Mail Servers Sendmail/Postfix Microsoft Exchange Server IBM Lotus
DNS Setup
DNS CONFIGURATION
DNS ConfigurationDNS Setup
named daemon is usedA DNS Server may be caching/master/slave server The named.ca file has information of all Root Servers.There is a Forward Zone file and a Reverse Zone file for every domain. Configuration file: /var/named/chroot/etc/named.confForward Zone File:/var/named/chroot/var/named/<forward_zone_file>Reverse Zone File:/var/named/chroot/var/named/<reverse_zone_file>
Sample Master named.confDNS Setup
zone "." { type hint; file "named.ca";};zone "0.0.127.in-addr.arpa" { type master; file "named.local"; allow-query {any;};};zone "iitk.ac.in" { type master; file "hosts.db"; allow-query {any;};};zone "95.200.203.IN-ADDR.ARPA" { type master; file "hosts.rev.203.200.95"; allow-query {any;};}; zone "iitk.ernet.in" { type slave; file "hosts.iitk.ernet.in"; masters { 202.141.40.10; }; allow-query {any;};
Sample Forward Zone FileDNS Setup
$TTL 86400@ IN SOA ns1.iitk.ac.in. root.ns1.iitk.ac.in. ( 200605091 ; Serial 10800 ; Refresh - 3 hours 3600 ; Retry - 1 hour 1209600 ;Expire - 1 week 43200 ) ; Minimum TTL for negative answers - 12 hours IN NS ns1.iitk.ac.in. IN NS ns2.iitk.ac.in.
IN MX 5 mail0.iitk.ac.in. IN MX 10 mail1.iitk.ac.in. IN MX 20 mail2.iitk.ac.in.
$ORIGIN iitk.ac.in.ns1 IN A 203.200.95.142mail0 IN A 203.200.95.144proxy IN CNAME mail0
Sample Reverse Zone FileDNS Setup
$TTL 86400$ORIGIN 200.203.in-addr.arpa.95 IN SOA ns1.iitk.ac.in. root.ns1.iitk.ac.in. ( 200605091 ; Serial 10800 ; Refresh - 5 minutes 3600 ; Retry - 1 minute 1209600 ; Expire - 1 weeks 43200 ) ; Minimum TTL for negative answers - 12 hours IN NS ns1.iitk.ac.in. IN NS ns2.iitk.ac.in.
$ORIGIN 95.200.203.in-addr.arpa.;;142 IN PTR ns1.iitk.ac.in.144 IN PTR mail0.iitk.ac.in.
Configuring Local ResolverDNS Setup
/etc/resolv.conf
server 127.0.0.1
Test DNSDNS Setup
nslookup
host
dig
Test your DNS with the following DNS diagnostics web site: dnsstuff.com
Apache Setup
APACHE SETUP
Web ServerWeb Server Setup
Apache Web Server is usedDaemon is httpd (service httpd start/stop/restart)
Files used by ApacheWeb Server Setup
Configuration file: /etc/httpd/conf/httpd.conf
Log files: /var/log/httpd/access_log and /var/log/httpd/error_log
Modules /etc/httpd/modules
Default Document Root /var/www/html
Default CGI Root /var/www/cgi-bin
Apache Configuration Directives
Web Server Setup
Server Name
Min and Max Servers
Document Root
CGI Enable/Disable User DirectoryDirectory IndexMime TypesModulesAccess RestrictionsSecure Server Virtual Hosting
Basic SettingsWeb Server Setup
Change the default value for ServerName www.<your-domain.com> in httpd.conf and put the website content in /var/www/htmlAdditionally you can configure Name based Virtual Hosting (allow more than one websites to run on the same server)
Virtual HostingWeb Server Setup
NameVirtualHost *:80
<VirtualHost *:80>ServerName server-nameDocumentRoot path-to-virtual-document-root</VirtualHost>
<VirtualHost *:80>ServerName server-nameDocumentRoot path-to-virtual-document-root</VirtualHost>
Squid Setup
SQUID SETUP
Obtaining Squid
Squid Setup
Source code (in C) from www.squid-cache.org
Binary executablesLinux (comes with RedHat and others)FreeBSDWindows
Pre-installed in Fedora/Enterprise Linux
Basic Settings
Squid Setup
Edit the /etc/squid/squid.conf file to configure squid
Configuration options:Disk Cache size and locationAuthenticationAllowed HostsAny other access restrictions (sites, content, size, time of access etc.) using ACL
service squid start/stop/restart
Disc Requirements
Squid Setup
Squid makes very heavy use of disc because of heavy read/write in cache
Needs discs with low seek times
SCSI is better
Can spread cache over 2 or more discs
Raid not recommended
Cached data is not critical
Calculating Disc Space
Squid Setup
Recommend keeping at least 2 days worth of objects
10 days may be betterExample:
256Kbps link loaded 10 hrs/day ~= 1GBassume 50% cacheable - .5GB / day2 days objects - 1GB10 days objects - 5 GB
Squid.conf Basic Configuration
Squid Setup
cache_dir ufs /var/spool/squid/cache 100 16 256
auth_param basic program /usr/lib/squid/ncsa_auth /etc/shadow
acl sidbiusers proxy_auth required
http_access allow sidbiusers
acl our_network src 172.28.250.0/24
http_access allow our_network
(Note: use squid –z for the first time to create the cache directory and its subdirectories)
Sendmail Setup
SENDMAIL SETUP
Sendmail ConfigurationMail Server Setup
Daemon: sendmailConfiguration File: /etc/mail/sendmail.mcEdit the following lines
LOCAL_DOMAIN(`localhost.localdomain')dnl(Replace localhost.localdomain by the domain name for which the mail server is being configured)DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl(comment this line by adding dnl at the start of the line)
dnl MASQUERADE_AS(`mydomain.com')dnl (remove dnl & replace mydomain.com by the domain name)
Sendmail Configuration
Sendmail Setup
Add the range of IP addresses of your network in access file(e.g. 172.31. Relay)Run “make –C /etc/mail” command to compile sendmail.mc and generate sendmail.cf file.
Restart sendmail and watch for errors
PoP & IMAP Server
Sendmail Setup
PoP3 & IMAP Server can be started using dovecot server. (service dovecot start)
Firewall
FIREWALL
Basic Setup
Firewall
Internet
Database
ApplicationWeb Server
Firewall
Firewall RulesIP Address of Source (Allow from Trusted Sources)
IP Address of Destination (Allow to trusted Destinations)
Application Port Number (Allow Mail but restrict Telnet)
Direction of Traffic (Allow outgoing traffic but restrict incoming traffic)
Firewall
Firewall ImplementationHardware Firewall: Dedicated Hardware Box (Cisco PIX, Netscreen )
Software Firewall: Installable on a Server ( )
Host OSs (Windows XP/Linux) also provide software firewall features to protect the host
These days Firewalls provide IDS/IPS (Intrusion Detection System/Intrusion Prevention System) services also.
Firewall
LINUX FirewallLinux Security
Use GUI (Applications ->System Settings-> Security Level) to activate the firewallAllow standard services and any specific port based applicationAll other services and ports are blocked
LINUX FirewallLinux Security