INTRODUCTION TO COMPUTER NETWORKS Computer Centre Indian 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 Hour Lecture 3: Physical Media (Copper, Fiber Optic and Wireless) : 2 Hour Lab 1: IIT Kanpur Datacenter Visit: 2 Hour Lecture 4: UTP & Fiber Cabling: 2 Hour Lecture 5: LAN Technologies (Ethernet, Fast Ethernet, Gigabit Ethernet, Wireless LAN) : 2 Hour Lab 2: Demo and Practice of UTP & Fiber Cabling: 2 Hour Lecture 6: LAN Technologies (contd.) : 2 Hour Course Content Course Content Lecture 7: WAN Technologies (Dialup, Leased Line, ISDN, ADSL, Cable Modem, VSAT) : 2 Hour Lab 3: Demo and Practice of Ethernet & Wireless LAN Setup : 2 Hour Lecture 8: WAN Technologies (contd.) : 2 Hour Lecture 9: Internet Protocol (IP) and IP Addressing: 2 Hour Lab 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 Hour Lecture 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 Hour Lab 6: Demo and Practice of Cisco Router Configuration : 2 Hour Lecture 15: DNS & Web Server Setup on Linux : 2 Hour Lab 7: Demo and Practice of DNS and Web Server Setup : 2 Hour Lecture 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 Books References Andrew S. Tanenbaum, Computer Network, PrenticeHall Doughlas Internet E. Comer, Computer Networks and http://www.cisco.com/public/support/tac/documenta tion.html http://www.redhat.com/docs http://home.iitk.ac.in/~navi/sidbinetworkcourse Grading Grading Guidelines Two Exams: 40% each Lab Assignments: 20% Minimum 80% attendance and minimum 60% marks are necessary to clear the course. Introduction to Computer Networks INTRODUCTION TO COMPUTER NETWORKS Introduction to Computer Networks Computer Networks Computer network connects two or more autonomous computers. The computers can be geographically located anywhere. Introduction to Computer Networks LAN, MAN & WAN 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) Introduction to Computer Networks Applications of Networks Resource Sharing Hardware (computing resources, disks, printers) Software (application software) Information Sharing Easy accessibility from anywhere (files, databases) Search Capability (WWW) Communication Email Message broadcast Remote computing Distributed processing (GRID Computing) Introduction to Computer Networks Network Topology The 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 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. Introduction to Computer Networks Ring Topology 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. Introduction to Computer Networks Mesh Topology The 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 Physical Media Interconnecting Devices Computers Networking Software Applications Introduction to Computer Networks 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 HUB, Switches, Routers, Wireless Access Points, Modems etc. Introduction to Computer Networks Computers: Clients and Servers In 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 Applications E-mail Searchable Data (Web Sites) E-Commerce News Groups Internet Telephony (VoIP) Video Conferencing Chat Groups Instant Messengers Internet Radio OSI Model OSI MODEL OSI Model Communication Architecture Strategy 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 Architecture Layer 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 model is the result of this effort. (OSI) reference 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 Model The 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 Model The 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 Layer Provides 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 Layer Data 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 Layer Implements routing of frames (packets) through the network. Defines the most optimum path the packet should take from the source to the destination Defines 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 Layer Purpose 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 Layer Session 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 Layer Presentation 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 Layer Application 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 Action A 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. TCP/IP Model TCP/IP MODEL TCP/IP Model OSI & TCP/IP Models TCP/IP Model TCP/IP Model Application Layer Application 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 Layer Management of cost effective and reliable data delivery, access to physical networks Physical Layer Physical Media Physical Media PHYSICAL MEDIA Physical Media Physical Media Physical Media Physical Media Copper Coaxial Cable - Thick or Thin Unshielded Twisted Pair - CAT 3,4,5,5e&6 Optical Fiber Multimode Singlemode Wireless Short Range Medium Range (Line of Sight) Satellite Physical Media Copper Media: Coaxial Cable Coaxial cable is a coppercored 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. Category Impedance Use RG-59 75 W Cable TV RG-58 50 W Thin Ethernet RG-11 50 W Thick Ethernet Physical Media Copper Media: Twisted Pair Twisted-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 used CAT 3, CAT 4, CAT 5, Enhanced CAT 5 and now CAT 6. Physical Media Categories of UTP UTP 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 Mhz 11.5 dB Attenuation 100 ohms Impedance Used in voice applications and 10baseT (10Mbps) Ethernet Physical Media Categories of UTP: CAT 4 20 MHz Bandwidth 7.5 dB Attenuation 100 ohms Impedance Used in 10baseT (10Mbps) Ethernet Physical Media Categories of UTP: CAT 5 100 MHz Bandwidth 24.0 dB Attenuation 100 ohms Impedance Used for high-speed data transmission Used in 10BaseT (10 Mbps) Ethernet & Fast Ethernet (100 Mbps) Physical Media Categories of UTP: CAT 5e 150 MHz Bandwidth 24.0 dB Attenuation 100 ohms Impedance Transmits high-speed data Used in Fast Ethernet (100 Mbps), Gigabit Ethernet (1000 Mbps) & 155 Mbps ATM Physical Media Categories of UTP: CAT 6 250 MHz Bandwidth 19.8 dB Attenuation 100 ohms Impedance Transmits high-speed data Used 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 Media Light travels through the optical media by the way of total internal reflection. Modulation scheme used is intensity modulation. Two types of Fiber media : Multimode Singlemode 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 Fiber Single-mode fiber Carries light pulses along single path Uses Laser Light Source Multimode fiber Many pulses of light generated by LED travel at different angles Physical Media Fiber Media The 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 Cable Contains one or several glass fibers at its core Surrounding the fibers is a layer called cladding Physical Media Fiber Optic Cable FO Cable may have 1 to over 1000 fibers Physical Media Wireless Media Very 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 Media Indoor : 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 Bands Band Range Propagatio n Application VLF 3–30 KHz Ground Long-range radio navigation LF 30–300 KHz Ground Radio beacons and navigational locators MF 300 KHz–3 MHz Sky AM radio HF 3–30 MHz Sky Citizens band (CB), ship/aircraft communication VHF 30–300 MHz Sky and line-of-sight VHF TV, FM radio UHF 300 MHz–3 GHz Line-ofsight UHF TV, cellular phones, paging, satellite SHF 3–30 GHz Line-ofsight Satellite communication EHF 30–300 GHz Line-ofsight Long-range radio navigation Physical Media Wireless LAN PC Access Point Internet Router Switch PC Access Point Physical Media Terrestrial Microwave Microwaves do not follow the curvature of earth Line-of-Sight transmission Height allows the signal to travel farther Two frequencies for two way communication Repeater is used to increase the distance Hop-by-Hop Physical Media Satellite Communication Cabling UTP AND FIBER CABLING Cabling Structured Cabling Infrastructure Mounted and permanent Allows patching Comfort that infrastructure is OK Components: Information Outlet with Face Plate Patch Panel UTP Cable Patch Cord Cabling I/O & Faceplates Faceplate mounts on or in wall or in raceway Single or Dual Information Outlet (I/O) Provide network connectivity to the Hosts through a Patch Cord Cabling Patch Panel Termination punchdown in back Patch cord plugin in front Cabling Patch Cord & UTP Connectors Cabling Color Codes Data Tx: 1 & 2 Data Rx: 3 & 6 Crossover 13 26 PoE +VDC: 4 & 5 PoE -VDC: 7 & 8 Cabling Cutting, Striping & Crimping Tools Make your own patch cords Cuts and strips pairs RJ45 end crimped onto ends of wire Cabling Punching Tool Terminates wires to back of patch panels and in Information Outlets Cabling Making Cables Cabling Wire Testing Equipment Test wire for correct termination of 8 wires Test for capabilities speed Cabling Cabling Rules Try 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 Pigtail Fiber Connectors LIU Coupler Fiber Patch Cord Cabling Fiber Optic Connectors Terminates the fibers Connects to other fibers or transmission equipment Cabling Fiber Patch Cords & Pigtails Ends are typically either SC or ST Pigtails have connectors on only one side and Patch Cords have it on both sides. Pigtails are spliced to the fiber to terminate the fiber Patch 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 lining Fiber Roles are typically 2 Km. Fiber cables are spliced using Jointers Faults like fiber cut are located using OTDR (Optical Time Domain Reflectometer) LAN Technologies LAN TECHNOLOGIES LAN Technologies Technology Options Ethernet Fast Ethernet Gigabit Ethernet 10 Gig Ethernet WLAN LAN Technologies Media Access Ethernet and technologies Wi-Fi are both “multi-access” Broadcast medium, shared by many hosts Simultaneous transmissions will result in collisions Media Access Control (MAC) protocol required Rules 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 Ethernet Carrier-sense multiple detection (CSMA/CD). CS = carrier sense MA = multiple access CD = collision detection access with collision Base Ethernet standard is 10 Mbps. 100Mbps, 1Gbps, 10Gbps standards came later LAN Technologies Ethernet CSMA/CD CSMA/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 Address End 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 Structure Preamble: 7 bytes with pattern 10101010 followed by one byte with pattern 10101011 Used to synchronize receiver, sender clock rates Addresses: 6 bytes, frame is received by all adapters on a LAN and dropped if address does not match Length: 2 bytes, length of Data field CRC: 4 bytes generated using CR-32, checked at receiver, if error is detected, the frame is simply dropped Data Payload: Maximum 1500 bytes, minimum 46 bytes If data is less than 46 bytes, pad with zeros to 46 bytes Length LAN Technologies Ethernet 10 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 Repeater LAN Technologies Ethernet STAR Topology Hub LAN Technologies Ethernet Physical Media :10 Base5 10 Base2 10 BaseT 10 BaseFL - Thick Co-axial Cable with Bus Topology Thin Co-axial Cable with Bus Topology UTP Cat 3/5 with Tree Topology Multimode/Singlemode Fiber with Tree Topology Maximum Segment Length 10 Base5 10 Base2 10 BaseT - 500 m with at most 4 repeaters (Use Bridge to extend the network) - 185 m with at most 4 repeaters (Use Bridge to extend the network) - 100 m with at most 4 hubs (Use Switch to extend the network) LAN Technologies Fast Ethernet 100 Mbps bandwidth Uses same CSMA/CD media access protocol and packet format as in Ethernet. 100BaseTX (UTP) and 100BaseFX (Fiber) standards Physical media :100 BaseTX - UTP Cat 5e 100 BaseFX - Multimode / Singlemode Fiber Full Duplex/Half Duplex operations. LAN Technologies Fast Ethernet Provision for Auto-Negotiation of media speed: 10 Mbps or 100Mbps (popularly available for copper media only). Maximum Segment Length 100 Base TX - 100 m 100 Base FX - 2 Km (Multimode Fiber) 100 Base FX - 20 km (Singlemode Fiber) LAN Technologies Gigabit Ethernet 1 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 Ethernet 10 Gbps bandwidth. Uses same CSMA/CD media access protocol as in Ethernet. Propositioned for Metro-Ethernet Maximum Segment Length 1000 Base-T - Not available 10GBase-LR - 10 Km (Singlemode Fiber) 10GBase-ER - 40 Km (Singlemode Fiber) LAN Technologies 802.11 Wireless LAN Desktop with PCI 802.11 LAN card Network connectivity to the legacy wired LAN Access Point Laptop with PCMCIA 802.11 LAN card 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 802.11 Wireless LAN Range ( 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: 802.11b 802.11a 802.11g LAN Technologies Multiple Access with Collision Avoidance (MACA) other node in sender’s range sender RTS receiver other node in receiver’s range CTS data ACK Before every data transmission Sender sends a Request to Send (RTS) frame containing the length of the transmission Receiver respond with a Clear to Send (CTS) frame Sender sends data Receiver sends an ACK; now another sender can send data When sender doesn’t get a CTS back, it assumes collision LAN Technologies WLAN : 802.11b The 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 : 802.11a Operates in the 5 GHz UNII (Unlicensed National Information Infrastructure) band Incompatible with devices operating in 2.4GHz Supports Data rates up to 54 Mbps. LAN Technologies WLAN : 802.11g Supports data rates as high as 54 Mbps on the 2.4 GHz band Provides backward equipment compatibility with 802.11b Repeater, HUB, Bridge & Switch REPEATER, HUB, BRIDGE AND SWITCH Repeater, Hub, Bridge & Switch Repeater A 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 OSI The 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 Hub Hubs 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 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 higherlayer 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 Switch Switches 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 Access Hosts have connection to switch A direct Full Duplex: No collisions Switching: A-to-A’ and B-toB’ simultaneously, no collisions C’ B switch Switches can be cascaded to expand the network C B’ A’ WAN Technologies WAN TECHNOLOGIES WAN Technologies Technology Options Dial-up Leased Line ISDN X.25 Frame Relay ATM DSL Cable Modem Microwave Point-to-Point Link VSAT WAN Technologies Dial-up Uses 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 Line On 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 RAS WAN Technologies Dial-up 33.6 Kbps Analog line Telephone switch ? Telephone switch Modem Modem 56 Kbps Access server Telephone switch Modem E1 WAN Technologies Leased Line Used 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 ISP Broadba nd Internet Connecti vity ISP Router Interface Converter ISP PREMISES PSTN LL Modem G.703 LL Modem V.35 Router CUSTOMER PREMISES WAN Technologies ISDN Another 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 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). B Basic Information 128 Kbps (Voice & Data) B D Signaling 16Kbps B Primary B D Information 1920 Kbps Voice & Data Signaling 64 Kbps WAN Technologies ISDN ISDN devices TE1 4W S/T interface TE2 NT1 2W U interface TA Devices NT1 - Interface Converter TE1 - ISDN devices TE2 – Non ISDN Devices (need TA) TA - Terminal Adapter (ISDN Modem) WAN Technologies X.25 Packet switched switches. Network consisting of X.25 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 Relay Designed to be more efficient than X.25 Developed before ATM Call control carried in separate logical connection No hop by hop error or flow control End to end flow and error control (if used) are done by higher layer Single user data frame sent from source to destination and ACK (from higher layer) sent back Two type of Virtual Circuits defined Permanent virtual circuits (PVCs) Switched virtual circuits (SVCs) WAN Technologies ATM Small 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 Exchange Service 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 Modems The 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 MICROWAVE LINK Router ISP Network RF Modem RF Modem Router Network CUSTOMER PREMISES ISP PREMISES WAN Technologies Point-to-Point Microwave Link Typically 80-100 MHz Band or 5 GHz Radio Link band 2.4 GHz WiFi links are becoming popular Requires Line of Sight WAN Technologies VSAT Very 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 9.6/19.2/32/64/128/256/512 Kbps. offered is Operating modes are TDM/TDMA, SCPC PAMA & DAMA WAN Technologies VSAT Each satellite sends and receives over two bands Uplink: From the earth to the satellite Downlink: From the satellite to the earth Satellite frequency bands Band Downlink C 3.7-4.2 GHz Ku 11.7-12.2 GHz Uplink 5.925-6.425 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. Internet Protocol INTERNET PROTOCOL Internet Protocol IP as a Routed Protocol IP 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 Address IP 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 carries special meaning. and 255.255.255.255 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 Address Class 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-to191.255.255.255), 16 bit host number. Class C : Address begins with bits 110. It has 24 bit network number (range 192.0.0.0-to223.255.255.255), 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 Consider IP address = 192.168.2.25 First 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 – Internet Protocol IP Address, Subnet Mask and Gateway IP Address and Subnet Mask define the Subnet For 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 172.31.15.255 Another notation is 172.31.1.0/28 The 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 Static DHCP Internet Protocol ARP ARP (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 IPv6 Internet 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 IPv6 IPv6 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. Routing ROUTING Routing Router A router is a device that determines the next network point to which a packet should be forwarded toward its destination Allow different networks to communicate with each other A 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 Protocols Static Routing Dynamic Routing IGP (Interior Gateway Autonomous System Protocol): Route data within an 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): Autonomous Systems BGP (Border Gateway Protocol) Route data between 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 VLAN VLANs VLANs (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 VLANs Broadcast 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 highperformance or isolated networking to separate VLANs. TCP/UDP TCP/UDP TCP/UDP TCP/UDP Transport Layer Protocol TCP is connection Oriented (uses checksum and acknowledgment) UDP is Connectionless Both 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) Natting NATTING Natting Private vs Public IP Addresses Whatever connects directly into Internet must have public (globally unique) IP address There is a shortage of public IPv4 address So Private IP addresses can be used within a private network Three address ranges are reserved for private usage 10.0.0.0/8 172.16.0.0/16 to 172.31.0.0/16 192.168.0.0/24 to 192.168.255.0/24 A private IP is mapped to a Public IP, when the machine has to access the Internet Natting NAT NAT (Network Address Translation) Maps Private IPs to Public IPs It is required because of shortage of IPv4 Address H1 H3 H2 10.0.1.2 10.0.1.3 Private network 1 H5 213.168.112.3 10.0.1.1 H4 10.0.1.2 10.0.1.1 10.0.1.3 Private network 2 Internet Router/NAT 128.195.4.119 Router/NAT 128.143.71.21 Natting NAT Static 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) Source = 128.143.71.21 Source port = 3200 Source = 10.0.1.2 Source port = 2001 Private address: 10.0.1.2 H1 Private network Private address: 10.0.1.3 H2 Source = 10.0.1.3 Source port = 1090 128.143.71.21 Internet NAT Source = 128.143.71.21 Destination = 4444 SNMP 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 agents SNMP managers Management Information Bases (MIBs) SNMP protocol itself SNMP agent SNMP manager SNMP protocol messages SNMP agent SNMP agent SNMP SNMP SNMP 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 SNMP SNMP uses five basic messages (GET, GET-NEXT, GETRESPONSE, 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 GETRESPONSE 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. VPN VPN VPN VPN VPN 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 Works To 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 Works VPN 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 VPN VPN 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. Enterprise Network ENTERPRISE NETWORK IMPLEMENTATION Enterprise Network Small Office Network Use Unmanaged 10/100 Switches Use Enhanced Cat 5 Pathcords Enterprise Network Campus Network Architecture Server Farm Firewall Backbone Switch Distribution Switch Access Switch Internet Enterprise Network Campus Network Architecture Uses Three Tier Switching Architecture (Popularly known as Cisco’s Switching Architecture) Backbone Switch Layer 3/4 Chassis based switch Multiple 100Fx or 1000SX/LX or 10GLX/LH ports for connectivity to Distribution switches Multiple 10/100/1000 ports for connectivity to Servers Distribution Switch Layer 2/3 Managed Fixed configuration switch 1/2 100Fx or 1000Sx/Lx or 10GLX/LH ports for connectivity to the Backbone switch Multiple 10/100 or 10/100/1000 ports for connectivity to the Access switches Access Switch Layer2 Managed/Unmanaged Fixed configuration switch Multiple 10/100 or 10/100/1000 ports for desktop connectivity Enterprise Network Campus Network Cabling Campus 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. Distribution Switch Backbone Switch Distribution Switch Distribution Switch Distribution Switch Distribution Switch Backbone Switch Distribution Switch Distribution Switch Distribution Switch Backbone Switch Distribution Switch Enterprise Network Campus Network The residential connectivity can be provided on Ethernet/Dial-up/ADSL. The Internet connectivity can be provided on leased line. Enterprise Network Enterprise WAN Architecture A 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 line Dial backup on ISDN (The Head Office has a PRI connectivity and the Remote offices have BRI connectivity) Enterprise Network Enterprise WAN Architecture The 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 Server Farm Corporate Head Office Branch Office Service Provider Network Branch Office All the locations are connected through a Service Provider Network over MPLS Backbone Branch Office Enterprise Network Service Provider Networks: Reliance Reliance 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 ISP networ k ISP networ k Bandwidth-limited links ISP network Customer Networks Backbone networks • Customers connect to an ISP • ISPs connect to backbone Enterprise Network Service Provider Networks: FLAG http://www.flagtelecom.com/Global_network.swf Cisco Devices CONFIGURING CISCO SWITCH AND ROUTER Cisco Devices Cisco’s LAN Switches Cisco Devices Cisco’s Routers Cisco Devices Hardware Components Depending on the model/series (at least) Mother Board/Back Plane CPU (RISC - MIPS or Motorola) Memory Bus I/O interfaces/Modules Cisco Devices Memory Components 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 voltage NVRAM – Non-Volatile RAM - holds router configuration; is not erased when router is reloaded RAM – Holds packet buffers, ARP cache, routing table, software and data structure that allows the router to function; runningconfig is stored in RAM, as well as the decompressed IOS in later router models ROM – Starts and maintains the router Cisco Devices What is IOS? 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 commandline configuration. IOS is designed to be hardware independent. Cisco Devices Configuring 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 Cisco Devices Configuring Cisco Devices Two modes of Operation : Consol Mode : Only Status monitored can be Enable Mode : Configuration can changed and seen be Router> enable (disable) Router# Cisco Devices CLI Commands 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 command history can be used Abbreviations of Commands can be used to see Cisco Devices Show Configuration sh run : To see running configuration sh conf : To see saved configuration Cisco Devices Save Configuration wr mem Cisco Devices Configuration Mode conf t Cisco Devices Disable or Delete the Configuration Use “no” before the configuration line Cisco Devices General Commands hostname ip default-gateway ip name-server ip routing ip route ip multicast-routing banner Cisco Devices Interface Configuration Commands Interfaces are named by type and position; e.g.: ethernet0, ethernet1/0,... Fastethernet0,fastethernet1/0,… gigabitethernet0,gigabitethernet1/0 serial0, serial1 ... serial3/1 Can be abbreviated: ethernet0 or eth0 or e0 serial0 or ser0 or s0 IP address and netmask configuration, status configuration etc. are done using interface commands: router#config terminal router(config)#interface e0 router(config-if)#ip address 195.176.118.254 255.255.255.0 router(config-if)#exit router# Cisco Devices Interface Commands 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 Cisco Devices Static Routing Commands 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 Cisco Devices Backup & Restore Configuration Copy (from cisco device to tftp server and viceversa) 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) Cisco Devices Static NAT Commands 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) Cisco Devices NAT Pool Commands 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) Cisco Devices Diagnostic Commands ping traceroute Cisco Devices General Monitoring and Administration Commands reload sh ver sh int Cisco Devices Upgrading Cisco IOS Download and install TFTP server (http://www.download.com) Download Cisco IOS Software Image to be upgraded Copy this image in the outbound directory of TFTP server Establish a Console or Telnet session with the router Use sh flash command to check that you have enough space in flash to install the new image Backup 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 DNS Internet Naming Hierarchy The silent dot at the end of all addresses .com .net .org .tcd .in .ac .iitk www www .co DNS Setup DNS Operation 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 RootServers. 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 Proxy Server Internet Connections ISP networ k ISP networ k Bandwidth-limited links ISP network Customer Networks Backbone networks • Customers connect to an ISP • ISPs connect to backbone Proxy Server Internet Connections 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) Proxy Server What is a Web Proxy? A proxy is a host which relays web access requests from clients Used when clients do not access the web directly Used for security, performance browser logging, proxy accounting web and Proxy Server 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 Caches Apache proxy MS proxy server WinProxy Squid Squid is popular because configurable and free Many others it is powerful, Web Server WEB SERVER Web Server Web Server HTTP (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 Server HTTP supports CGI (Common Gateway interface) HTTP supports Virtual Hosting (Hosting multiple sites on the same server) Popular Web Servers Apache Windows IIS IBM Websphere Email EMAIL Email Mail Architecture Internet Mail Server Mail Client Mail Server Mail Client Email Mail Architecture Email 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 Setup DNS Configuration named daemon is used A 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.conf Forward Zone File: /var/named/chroot/var/named/<forward_zone_file> Reverse Zone File: /var/named/chroot/var/named/<reverse_zone_file> DNS Setup Sample Master named.conf 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;}; DNS Setup Sample Forward Zone File $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 mail0 IN A proxy IN CNAME 203.200.95.142 203.200.95.144 mail0 DNS Setup Sample Reverse Zone File $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. DNS Setup Configuring Local Resolver /etc/resolv.conf server 127.0.0.1 DNS Setup Test DNS nslookup host dig Test your DNS with the following DNS diagnostics web site: dnsstuff.com Apache Setup APACHE SETUP Web Server Setup Web Server Apache Web Server is used Daemon is httpd (service httpd start/stop/restart) Web Server Setup Files used by Apache 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 Web Server Setup Apache Configuration Directives Server Name Min and Max Servers Document Root CGI Enable/Disable User Directory Directory Index Mime Types Modules Access Restrictions Secure Server Virtual Hosting Web Server Setup Basic Settings Change the default value for ServerName www.<your-domain.com> in httpd.conf and put the website content in /var/www/html Additionally you can configure Name based Virtual Hosting (allow more than one websites to run on the same server) Web Server Setup Virtual Hosting NameVirtualHost *:80 <VirtualHost *:80> ServerName server-name DocumentRoot path-to-virtual-document-root </VirtualHost> <VirtualHost *:80> ServerName server-name DocumentRoot path-to-virtual-document-root </VirtualHost> Squid Setup SQUID SETUP Squid Setup Obtaining Squid Source code (in C) from www.squid-cache.org Binary executables Linux (comes with RedHat and others) FreeBSD Windows Pre-installed in Fedora/Enterprise Linux Squid Setup Basic Settings Edit the /etc/squid/squid.conf file to configure squid Configuration options: Disk Cache size and location Authentication Allowed Hosts Any other access restrictions (sites, content, size, time of access etc.) using ACL service squid start/stop/restart Squid Setup Disc Requirements 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 Squid Setup Calculating Disc Space Recommend keeping at least 2 days worth of objects 10 days may be better Example: 256Kbps link loaded 10 hrs/day ~= 1GB assume 50% cacheable - .5GB / day 2 days objects - 1GB 10 days objects - 5 GB Squid Setup Squid.conf Basic Configuration 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 Mail Server Setup Sendmail Configuration Daemon: sendmail Configuration File: /etc/mail/sendmail.mc Edit 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 Setup Sendmail Configuration 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 Sendmail Setup PoP & IMAP Server PoP3 & IMAP Server can be started using dovecot server. (service dovecot start) Firewall FIREWALL Firewall Basic Setup Internet Application Web Server Database Firewall Firewall Firewall Rules IP Address of Source (Allow from Trusted Sources) IP Address of Destinations) Destination (Allow to trusted Application Port Number (Allow Mail but restrict Telnet) Direction of Traffic (Allow outgoing traffic but restrict incoming traffic) Firewall Firewall Implementation Hardware 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. Linux Security LINUX Firewall Use GUI (Applications ->System Settings-> Security Level) to activate the firewall Allow standard services and any specific port based application All other services and ports are blocked Linux Security LINUX Firewall