intern

Networking

ArjunRahul

SheebaTushar

ONGC

July 6, 2012

Outline

IntroductionONGCOur Experience

Network DevicesModemsFDDI802.3 - Ethernet

NetworksTopologyNetwork Interface CardsTypes of NetworkIP AddressingDNS

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Acknowledgement

We like to thank Mrs Chaddha for her guidance throughout ourinternship.

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ONGC

Oil and Natural Gas Corporation Limited (ONGC) is an Indianstate-owned oil and gas company headquartered in Dehradun, India.It is one of the largest Asia-based oil and gas exploration andproduction companies, and produces around 77% of India’s crude oil(equivalent to around 30% of the country’s total demand) and around81% of its natural gas. ONGC is one of the largest publicly tradedcompanies by market capitalization in India. It is ranked 361st in the2011 Fortune Global 500 list and is among the Top 250 Global EnergyCompany by Platts.

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Our Experience (1)

Through our intership at ONGC we were exposed to the innerworking of the server room at Telbhawan. We examined the workingof the following servers

• AD - Active Director, used for authentication of employees of theONGC by verifying theirs CPF numbers.

• DHCP - Dynamic Host Control Protocol, used to allocateddynamic IP address.

• Anti-virus - It is used for verifying if the client has anti-virusinstalled in it.

• IWSS - It is used for scanning the computers in the network

• Blue Coat - It is the Internet distribution proxy

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Our Experience (2)

• WSUS - Windows System Update Server, used to update thesoftware of all the computers in the network.

• Websense - It filters the computers for possible threat

The ISP provider to ONGC is BSNL. Four lease lines of 2 Kbps isconnecting Delhi to Dehradun. The main router used in ONGC is IASfrom Cisco. At Dehradun, various routers & switch of Cisco are used.The intranet of ONGC at Telbhawan is connected to KDMIP thoughL3 switches. The optical fiber is extended to City Hospital.We then visited KDMIP which uses SATCOM for communication.The satellite works in the Ka Band channel with 3 GHz.

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Modem (1)

A modem (modulator-demodulator) is a device that modulates ananalog carrier signal to encode digital information, and alsodemodulates such a carrier signal to decode the transmittedinformation. The goal is to produce a signal that can be transmittedeasily and decoded to reproduce the original digital data.

The most familiar example is a voice band modem that turns thedigital data of a personal computer into modulated electrical signalsin the voice frequency range of a telephone channel. These signalscan be transmitted over telephone lines and demodulated by anothermodem at the receiver side to recover the digital data.

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Modem (2)

Figure: Modem

Modems are generally classified by the amount of data they can sendin a given unit of time, usually expressed in bits per second (bit/s, orbps). Modems can alternatively be classified by their symbol rate,measured in baud. The baud unit denotes symbols per second, or thenumber of times per second the modem sends a new signal. Modemsare of two types :

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Modem (3)

Figure: Internal ModemFigure: External Modem

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Fiber Distributed Data Interface (1)

The Fiber Distributed Data Interface (FDDI) topology is ring withtwo counter rotating rings for reliability with no hubs. Cable type isfiber-optic. Connectors are specialized. The media access method istoken passing. The maximum length is 100 kilometers. Themaximum number of nodes on the network is 500. Speed is 100Mbps. FDDI is normally used as a backbone to link other networks.A typical FDDI network can include servers, concentrators, and linksto other networks.

Devices called concentrators provide functions similar to hubs. Mostconcentrators use dual attachment station network cards but singleattachment concentrators may be used to attach more workstationsto the network.

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Figure: FDDI

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FDDI token passing allows multiple frames to circulate around thering at the same time. Priority levels of a data frame and token canbe set to allow servers to send more data frames. Time sensitive datamay also be given higher priority. The second ring in a FDDI networkis a method of adjusting when there are breaks in the cable. Theprimary ring is normally used, but if the nearest downstream neighborstops responding the data is sent on the secondary ring in attempt toreach the computer. Therefore a break in the cable will result in thesecondary ring being used.

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Figure: FDDI

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There are two network cards which are:

• Dual attachment stations (DAS) used for servers and concentratorsare attached to both rings.

• Single Attachment stations (SAS) attached to one ring and usedto attach workstations to concentrators.

A router or switch can link an FDDI network to a local area network(LAN). Normally FDDI is used to link LANs together since it coverslong distances.

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Ethernet (1)

In 1973, at Xerox Corporations Palo Alto Research Center (morecommonly known as PARC), researcher Bob Metcalfe designed andtested the first Ethernet network. While working on a way to linkXeroxs ”Alto” computer to a printer, Metcalfe developed the physicalmethod of cabling that connected devices on the Ethernet as well asthe standards that governed communication on the cable. Ethernethas since become the most popular and most widely deployed networktechnology in the world. Many of the issues involved with Ethernetare common to many network technologies, and understanding howEthernet addressed these issues can provide a foundation that willimprove your understanding of networking in general.

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Ethernet (2)

The Ethernet standard has grown to encompass new technologies ascomputer networking has matured, but the mechanics of operation forevery Ethernet network today stem from Metcalfes original design.The original Ethernet described communication over a single cableshared by all devices on the network. Once a device attached to thiscable, it had the ability to communicate with any other attacheddevice. This allows the network to expand to accommodate newdevices without requiring any modification to those devices already onthe network.

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Ethernet Cabling (1)

Figure: Ethernet Cabling

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Ethernet Cabling (2)

Figure: The most common kinds of Ethernet cabling

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Network Topologies

• Topology - Physical and logical network layout◦ Physical actual layout of the computer cables and other network

devices◦ Logical the way in which the network appears to the devices that use

it.

• Common topologies◦ Bus, ring, star, mesh and wireless

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Bus Topology

• Uses a trunk or backbone to which all of the computers on thenetwork connect.

• Uses a trunk or backbone to which all of the computers on thenetwork connect.

• Coaxial cablings ( 10Base-2, 10Base5) were popular options yearsago.

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Advantages

• Cable faults are easily located,making troubleshooting easier

• Ring network are moderatelyeasy to install

Disadvantages

• Expansion to the network cancause network disruption

• A single break in the cable candisrupt the entire network

Figure: Bus Topology

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Star Topology

• All computers/devices connect to a central device called hub orswitch.

• Each device requires a single cable

• point-to-point connection between the device and hub.

• Most widely implemented

• Hub is the single point of failure

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Figure: Star Topology

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Advantages

• Easily expanded withoutdisruption to the network

• Cable failure affects only asingle user

• Easy to troubleshoot & isolateproblems

Disadvantages

• Requires more cable

• A central connecting deviceallows for a single point offailure

• More difficult to implement

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Mesh Topology

• Each computer connects to every other

• High level of redundancy.

• Rarely used◦ Wiring is very complicated◦ Cabling cost is high◦ Troubleshooting a failed cable is tricky◦ A variation hybrid mesh create point to point connection between

specific network devices, often seen in WAN implementation.

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Advantages

• Provides redundant pathbetween devices

• The network can be expandedwithout to current uses

Disadvantages

• Requires more cable than theother LAN topologies

• Complicated

Figure: Mesh Topology

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Wireless

• Do not require physical cabling

• Particularly useful for remote access for laptop users

• Eliminate cable faults and cable breaks.

• Signal interference and security issue.

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Advantages

• Allows for wireless remoteaccess

• Network can be expandedwithout disruption to currentusers

Disadvantages

• Potential security issuesassociated with wirelesstransmission

• Limited speed in comparison toother network topologies

Figure: Wireless

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NIC

• A network interface card, more commonly referred to as a NIC, is adevice that allows computers to be joined together in a LAN, orlocal area network .

• The network interface card acts as the liaison for the machine toboth send and receive data on the LAN .

• In computer networking, a NIC provides the hardware interfacebetween a computer and a network.

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Figure: Network cards are typically available in 10/100/1000 Mbit/svarieties. This means they can support a notional maximum transfer rate of10, 100 or 1000 Megabits per second

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NIC...Need

• Most computer networks transfer data across a medium at a fixedrate, often faster than the speed at which computers can processindividual bits.

• To accommodate the mismatch in speed, each computer attachedto a network contain special purpose hardware known as a networkinterface card (NIC).

• The NIC functions like an I/O device: it is built for a specificnetwork technology.

• It handles the details of frame transmission or reception withoutrequiring the CPU to process each bit.

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NIC (1)...Working

• A computer or device on a network can be reached by its MAC(media access control) address through the NIC card.

• Every Ethernet network card has a unique 48-bit serial numbercalled a MAC address, which is stored in ROM carried on the card.

• The MACs on the network are used to direct traffic between thecomputers.

• An example of a MAC address: A1B2C3D4E5F6

• The first 6 hex digits in the MAC address is the OUI(organizationally unique identifier), assigned by the IEEE to eachmanufacturer (e.g. Cisco, Intel etc).

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NIC (2)...Working

• The rest of the MAC address can be assigned in any way by themanufacturer to the individual networking devices that itmanufactures

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NIC...Port

• The back plate of the network interface card features a port thatlooks similar to a phone jack, but is slightly larger.

• A network card typically has a twisted pair, BNC, or AUI socketwhere the network cable is connected, and a few LEDs to informthe user of whether the network is active, and whether or not thereis data being transmitted on it.

• That port accommodates an Ethernet cable, which resembles athicker version of a standard telephone line.

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Figure: Network Interface Card for connection of a computer to an EthernetNetwork

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NIC...on a Network

• The card implements the electronic circuitry required tocommunicate using a specific physical layer and data link layerstandard such as Ethernet or token ring.

• This provides a base for a full network protocol stack, allowingcommunication among small groups of computers on the sameLAN and large-scale network communications through routableprotocols, such as IP.

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Types of Network

• Local Area Network

• Wide Area Netwok

• Metropolitan Area Network

• Wireless Networks

• Home Networks

• Internetworks

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LAN

A LAN connects network devices over a relatively short distance. Anetworked office building, school, or home usually contains a singleLAN, though sometimes one building will contain a few small LANs(perhaps one per room), and occasionally a LAN will span a group ofnearby buildings.

In TCP/IP networking, a LAN is often but not always implemented asa single IP subnet.

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Figure: An isolated IAN connecting 12 computers to a hub in a closet

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WAN

As the term implies, a WAN spans a large physical distance. TheInternet is the largest WAN, spanning the Earth.

A WAN is a geographically-dispersed collection of LANs. A networkdevice called a router connects LANs to a WAN. In IP networking, therouter maintains both a LAN address and a WAN address.

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Wireless (1)

Wireless network refers to any type of computer network that is notconnected by cables of any kind. It is a method by which homes,telecommunications networks and enterprise (business) installationsavoid the costly process of introducing cables into a building, or as aconnection between various equipment locations. Wirelesstelecommunications networks are generally implemented andadministered using a transmission system called radio waves. Thisimplementation takes place at the physical level (layer) of the OSImodel network structure.

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Wireless (2)

Figure: Wireless

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Types of wireless networks (1)

• Wireless PAN◦ Wireless personal area networks (WPANs) interconnect devices within

a relatively small area that is generally within a person’s reach. Forexample, both Bluetooth radio and invisible infrared light provides aWPAN for interconnecting a headset to a laptop. Wi-Fi PANs arebecoming commonplace as equipment designers start to integrateWi-Fi into a variety of consumer electronic devices.

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• Wireless LANs◦ A wireless local area network (WLAN) links two or more devices over

a short distance using a wireless distribution method, usually providinga connection through an access point for Internet access. The use ofspread-spectrum or OFDM technologies may allow users to movearound within a local coverage area, and still remain connected to thenetwork. Products using the IEEE 802.11 WLAN standards aremarketed under the Wi-Fi brand name. Fixed wireless technologyimplements point-to-point links between computers or networks attwo distant locations, often using dedicated microwave or modulatedlaser light beams over line of sight paths. It is often used in cities toconnect networks in two or more buildings without installing a wiredlink.

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• Wireless mesh network◦ A wireless mesh network is a wireless network made up of radio nodes

organized in a mesh topology. Each node forwards messages on behalfof the other nodes. Mesh networks can ”self heal”, automaticallyre-routing around a node that has lost power.

• Wireless MAN◦ Wireless metropolitan area networks are a type of wireless network

that connects several wireless LANs. WiMAX is a type of WirelessMAN and is described by the IEEE 802.16 standard.

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• Wireless WAN◦ Wireless wide area networks are wireless networks that typically cover

large areas, such as between neighboring towns and cities, or city andsuburb. These networks can be used to connect branch offices ofbusiness or as a public internet access system. The wirelessconnections between access points are usually point to pointmicrowave links using parabolic dishes on the 2.4GHz band, ratherthan omnidirectional antennas used with smaller networks. A typicalsystem contains base station gateways, access points and wirelessbridging relays

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Other Types of Area Networks (1)

• Metropolitan Area Network - a network spanning a physical arealarger than a LAN but smaller than a WAN, such as a city. AMAN is typically owned an operated by a single entity such as agovernment body or large corporation.

• Campus Area Network - a network spanning multiple LANs butsmaller than a MAN, such as on a university or local businesscampus.

• Storage Area Network - connects servers to data storage devicesthrough a technology like Fibre Channel.

• System Area Network - links high-performance computers withhigh-speed connections in a cluster configuration. Also known asCluster Area Network.

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OSI Model

Virtually all networks in use today are based in some fashion on theOpen Systems Interconnection (OSI) standard. OSI was developed in1984 by the International Organization for Standardization (ISO), aglobal federation of national standards organizations representingapproximately 130 countries.

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The Layers

Think of the seven layers as the assembly line in the computer. Ateach layer, certain things happen to the data that prepare it for thenext layer.

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Application Set

• Application - This is the layer that actually interacts with theoperating system or application whenever the user chooses totransfer files, read messages or perform other network-relatedactivities.

• Presentation - Layer 6 takes the data provided by the Applicationlayer and converts it into a standard format that the other layerscan understand.

• Session - Layer 5 establishes, maintains and ends communicationwith the receiving device.

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Transport Set (1)

• Transport - This layer maintains flow control of data and providesfor error checking and recovery of data between the devices. Flowcontrol means that the Transport layer looks to see if data iscoming from more than one application and integrates eachapplication’s data into a single stream for the physical network.

• Network - The way that the data will be sent to the recipientdevice is determined in this layer. Logical protocols, routing andaddressing are handled here.

• Data - In this layer, the appropriate physical protocol is assigned tothe data. Also, the type of network and the packet sequencing isdefined.

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Transport Set (2)

• Physical - This is the level of the actual hardware. It defines thephysical characteristics of the network such as connections, voltagelevels and timing.

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Benefits of the OSI Model

By separating the network communications into logical smaller pieces,the OSI model simplifies how network protocols are designed. TheOSI model was designed to ensure different types of equipment (suchas network adapters, hubs, and routers) would all be compatible evenif built by different manufacturers. A product from one networkequipment vendor that implements OSI Layer 2 functionality, forexample, will be much more likely to interoperate with anothervendor’s OSI Layer 3 product because both vendors are following thesame model.

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IPv4 Addressing

An IP address is an identifier that is assigned at the Internet layer toan interface or a set of interfaces. Each IP address can identify thesource or destination of IP packets. For IPv4, every node on a networkhas one or more interfaces, and you can enable TCP/IP on each ofthose interfaces. When you enable TCP/IP on an interface, youassign it one or more logical IPv4 addresses, either automatically ormanually. The IPv4 address is a logical address because it is assignedat the Internet layer and has no relation to the addresses that areused at the Network Interface layer. IPv4 addresses are 32 bits long

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Figure: IPv4 Address Syntax

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Types of IPv4 Addresses

Internet standards define the following types of IPv4 addresses:

• UnicastAssigned to a single network interface located on a specific subnet;used for one-to-one communication.

• MulticastAssigned to one or more network interfaces located on varioussubnets; used for one-to-many communication

• BroadcastAssigned to all network interfaces located on a subnet; used forone-to-everyone on a subnet communication.

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Public address

• Most IP addresses are public addresses. Public addresses areregistered as belonging to a specific organization.

• Internet Service Providers (ISP) and extremely large organizationsin the U.S. obtain blocks of public addresses from the AmericanRegistry for Internet Numbers (ARIN http://www.arin.net). Otherorganizations obtain public addresses from their ISPs.

• There are ARIN counterparts in other parts of the world, and all ofthese regional registration authorities are subject to the globalInternet Assigned Numbers Authority (IANA http://www.iana.org).

• Public IP addresses are routed across the Internet, so that hostswith public addresses may freely communicate with one anotherglobally.

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Private Address

• RFC 1918 designates the following as private addresses.◦ Class A range: 10.0.0.0 through 10.255.255.255.◦ Class B range: 172.16.0.0 through 172.31.255.255.◦ Class C range: 192.168.0.0 through 192.168.255.255.

• Private addresses may be used by any organization, without anyrequirement for registration.

• Because private addresses are ambiguous - cant tell where theyrecoming from or going to because anyone can use them - privateaddresses are not permitted to be routed across the Internet

• ISPs block private addresses from being routed across theirinfrastructure.

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Classful IP Addressing (1)

Three main classes• Class A networks

◦ First octet values range from 1 through 126.◦ First octet starts with bit 0◦ Network mask is 8 bits, written /8 or 255.0.0.0.◦ 1.0.0.0 through 126.0.0.0 are class A networks with 16777214 hosts

each.

• Class B networks◦ First octet values range from 128 through 191.◦ First octet starts with binary pattern 10.◦ Network mask is 16 bits, written /16 or 255.255.0.0.◦ 128.0.0.0 through 191.255.0.0 are class B networks, with 65534 hosts

each.

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Classful IP Addressing (2)

• Class C networks◦ First octet values range from 192 through 223.◦ First octet starts with binary pattern 110.◦ Network mask is 24 bits, written /24 or 255.255.255.0.◦ 192.0.0.0 through 223.255.255.0 are class C networks, with 254 hosts

each

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Two additional classes and reserved addresses

• Class D addresses◦ First octet values range from 224 through 239.◦ First octet starts with binary pattern 1110.◦ Class D addresses are multicast addresses, which will not be discussed

in this tutorial.

• Class E addresses◦ Essentially everything thats left.◦ Experimental class, which will not be discussed in this tutorial.

• Reserved addresses

◦ 0.0.0.0 is the default IP address, and it is used to specify a defaultroute. The default route will be discussed later.

◦ Addresses beginning with 127 are reserved for internal loopbackaddresses. It is common to see 127.0.0.1 used as the internalloopback address on many devices.

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Subnet Masks (1)

Extending the classful network mask

• Subnet masks are used to make classful networks more manageableand efficient, by creating smaller subnets and reducing the numberof host addresses per subnet to what is actually required.

• Subnet masks were first used on class boundaries.

• Example◦ Take class A network 10.0.0.0 with network mask 255.0.0.0.◦ Add additional 8 subnet bits to network mask.◦ New subnet mask is 255.255.0.0.◦ New subnets are 10.0.0.0, 10.1.0.0, 10.2.0.0, and so on with 65534

host addresses per subnet. Still too many hosts per subnet.

• Example◦ Take class A network 10.0.0.0 with network mask 255.0.0.0.

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Subnet Masks (2)

◦ Add additional 16 subnet bits to network mask.◦ New subnet mask is 255.255.255.0◦ New subnets are 10.0.0.0, 10.0.1.0, 10.0.2.0, ..., 10.1.0.0, 10.1.1.0,

10.1.2.0, ..., 10.2.0.0, 10.2.1.0, 10.2.2.0, and so on with 254 hostaddresses per subnet.

• Example◦ Take class B network 172.16.0.0 with network mask 255.255.0.0.◦ Add additional 8 subnet bits to network mask.◦ New subnet mask is 255.255.255.0◦ New subnets are 172.16.0.0, 172.16.1.0, 172.16.2.0, and so on with

254 host addresses per subnet.

• As shown in these examples...◦ A class A network can be subnetted to create 256 (28 ) /16 subnets.◦ A class A network can be subnetted to create 65536 (216) /24 subnets.◦ A class Bnetwork can be subnetted to create 256 (28) /24 subnets.

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DNS

Short for Domain Name System (or Service or Server), an Internetservice that translates domain names into IP addresses. Becausedomain names are alphabetic, they’re easier to remember. TheInternet however, is really based on IP addresses.

Every time you use a domain name, therefore, a DNS service musttranslate the name into the corresponding IP address. For example,the domain name www.example.com might translate to198.105.232.4.

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Figure: DNS

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Figure: The DNS client program sends a request to a DNS server to mapthe e-mail address to the corresponding IP address

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Namespace (1)

A name space that maps each address to a unique name can beorganized in two ways: flat or hierarchical.

Flat Name Space

In a flat name space, a name is assigned to an address. A name inthis space is a sequence of characters without structure. The maindisadvantage of a fiat name space is that it cannot be used in a largesystem such as the Internet because it must be centrally controlled toavoid ambiguity and duplication.

Hierarchical Name Space

In a hierarchical name space, each name is made of several parts.The first part can define the nature of the organization, the second

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Namespace (2)

part can define the name of an organization, the third part can definedepartments in the organization, and so on. For example, assume twocolleges and a company call one of their computers challenger. Thefirst college is given a name by the central authority such as jhda.edu,the second college is given the name berkeley.edu, and the company isgiven the name smart. com. When these organizations add the namechallenger to the name they have already been given, the end result isthree distinguishable names: challenger.jhda.edu,challenger.berkeley.edu, and challenger.smart.com. The names areunique without the need for assignment by a central authority.

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Figure: The domain names are always read from the node up to the root

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Figure: The last label is the label of the root (null) as below

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Domain

Figure: A domain is a subtree of the domain name space. The name of thedomain is the domain name of the node at the top of the subtree

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DISTRIBUTION OF NAME SPACE

Hierarchy of Name Servers

The solution to these problems is to distribute the informationamong many computers called DNS servers. One way to do this is todivide the whole space into many domains based on the first level.

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Zone

Since the complete domain name hierarchy cannot be stored on asingle server, it is divided among many servers. What a server isresponsible for or has authority over is called a zone. The servermakes a database called a zone file and keeps all the information forevery node under that domain.

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Root Server

A root server is a server whose zone consists of the whole tree.There are several root servers, each covering the whole domain namespace.

Primary and Secondary ServersA primary server loads all information from the disk file; the

secondary server loads all information from the primary server. Whenthe secondary downloads information from the primary, it is calledzone transfer.

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Figure: DNS is a protocol that can be used in different platforms. In theInternet, the domain name space (tree) is divided into three differentsections: generic domains, country domains, and the inverse domain

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Generic Domains

Figure: The generic domains define registered hosts according to theirgeneric behavior. Each node in the tree defines a domain, which is an indexto the domain name space database

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Country Domains

Figure: The country domains section uses two-character countryabbreviations (e.g., us for United States). Second labels can beorganizational, or they can be more specific, national designations.

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Inverse Domain

The inverse domain is used to map an address to a name. This mayhappen, for example, when a server has received a request from aclient to do a task. Although the server has a file that contains a listof authorized clients, only the IP address of the client (extracted fromthe received IP packet) is listed. The server asks its resolver to send aquery to the DNS server to map an address to a name to determine ifthe client is on the authorized list.

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