The Internet and LANMonitoring and Troubleshooting

Mohammad Atiqur RahmanBCS (Telecommunication)

Assistant Divisional EngineerBangladesh Telecommunications Company Ltd.

(BTCL)

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ContentsIntroduction:•What is Internet?•History of Internet•Popular Services over the Internet•Internet Infrastructure•Administration of InternetInternet Service Provider:•What is an ISP•Components of an ISP•Internet Access Technologies

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Local Area Network:•Local Area Network•Network Devices•Network MediaMonitoring the Network:•MRTG•SmokePingTroubleshooting the Network:•Ping•Traceroute•MTR

Introduction

• What is Internet?• History of Internet• Popular Services over the Internet• Internet Infrastructure• Administration of Internet

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What is InternetThe Internet is a global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users worldwide.

It is a network of networks that consists of millions of private, public, academic, business, and government networks, of local to global scope, that are linked by a broad array of electronic, wireless and optical networking technologies.

The Internet carries a vast range of information resources and services, such as the inter-linked hypertext documents of the World Wide Web (WWW) and the infrastructure to support electronic mail.

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WWWWWW is a system of interlinked hypertext documents accessed via the Internet. With a web browser, one can view web pages that may contain text, images, videos, and other multimedia and navigate between them via hyperlinks.The idea of a world of boundless information in which all items have a reference by which they can be retrieved;

The address system (URI/URL) which the project implemented to make this world possible, despite many different protocols;

A network protocol (HTTP) used by native WWW servers giving performance and features not otherwise available;

A markup language (HTML) which every WWW client is required to understand, and is used for transmission of basic things such as text, graphics and simple on-line help information across the net;

A body of data available on the Internet using all or some of the preceding items.

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Email

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• SMTP Server• POP3 Server• IMAP Server (The Internet

Message Access Protocol)• Email Client (Outlook

Express, Eudora, Thunderbird)

Internet Infrastructure• Routers• Servers• Communications

Medium

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Intercontinental Communication Medium

• Submarine Cable System• Satellite Communications System

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Submarine Cable System

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SEA-ME-WE4 Submarine Cable System

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Satellite Communication System

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Administration of Internet• The Internet has no centralized governance in either

technological implementation or policies for access and usage; each constituent network sets its own standards.

• The Internet Corporation for Assigned Names and Numbers (ICANN): Dictates only the overreaching definitions of the two principal name spaces in the Internet, the Internet Protocol address space and the Domain Name System.

• Internet Engineering Task Force (IETF): The technical underpinning and standardization of the core protocols (IPv4 and IPv6).

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Internet Service Provider

• What is an ISP• Components of an ISP• Internet Access Technologies

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Internet Service Provider (ISP)

An Internet service provider (ISP) is a company that provides access to the Internet in exchange of a monthly or yearly fee.

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Components of an ISP• Routers• Switch• RAS• Web Server• Mail Server• AAA Server• FTP Server• DNS Server• Bandwidth Manager

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Access Technologies

• Wired– Existing Telephone Cable• Dial-UP • ADSL

– Optical Fiber Cable

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Access Technologies• Wireless

– Wifi: upto 100 Mbps– WiMAX (Worldwide Interoperability for Microwave Access) is a

telecommunications protocol that provides fixed and fully mobile internet access. The current WiMAX revision provides up to 40 Mbit/s with the IEEE 802.16m update expected offer up to 1 Gbit/s fixed speeds.

– GPRS: General packet radio services, a technology for radio transmission of small packets of data, especially between cellular phones and the Internet. promised data rates from 56 up to 114 Kbps.

– EDGE (Enhanced Data rates for GSM Evolution): EDGE can carry a bandwidth up to 236.8 kbit/s

– EV-DO (Evolution-Data Optimized): CDMA 1xEV-DO is a 3G technology add-on for CDMA networks that allows for theoretical download speeds as fast as 2.4576Mbps

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Local Area Network

• Local Area Network• Network Devices• Network Media

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LAN

• PC• Media (Cable or Wireless)• Switch• Router• Firewall• Media Converter

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Media UTP Cable• Straight-through Cable• Cross-over Cable

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Media Optical Fiber Cable

• Single Mode Fiber• Multi Mode Fiber

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Switch

A switch is a computer networking device that connects network segments or network devices. A switch receives a message from any device connected to it and then transmits the message only to that device for which the message was meant.

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SwitchHubs vs. SwitchesPrior to switches, Hubs were the standard for connecting devices on a local area network (LAN). The problem with hubs was that everything that went through them had to share the bandwidth of the link, bandwidth was wasted because all traffic was sent to all devices, and there were a lot of collisions because the hub didn’t do anything to prevent them. A switch fixes these problems.

What do switches do?Switches work at Layer 2 of the OSI model, not Layer 1 like a hubSwitches switch Ethernet framesSwitches don’t look at IP address information, only Ethernet MAC addressesSwitches keeps a table of all MAC addresses traversing the switch and what port they are on (this table is called the bridge forwarding table or CAM table)Switches only sends traffic to the devices that are the destination for that traffic, saving bandwidthEach device connected to the switch gets the full bandwidth of the switch port because the switch prevents collisions

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Router

What is a RouterA router is specialized computer connected to more than one network. A router runs software that allows the device to move data from one network to another. Routers operate at the network layer (OSI Model's layer 3). The primary function of a router is to connect networks together and keep certain kinds of broadcast traffic under control. There are several companies that make routers: Cisco (Linksys), Juniper, Nortel (Bay Networks), Redback, Lucent, 3Com, and HP just to name a few.

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Router

What are the functions of a routerRouters used in networks perform the following functions:Restrict network broadcasts to the LANAct as the default gateway.Move data between networksLearn and advertise loop free paths

Is Router an essential element in a network ?In a small network, with few hosts, we don't need a router unless we are connecting our network to another network. For example, the Internet is a very large network, so we need a router (and a lot of other things) to connect our network to the Internet

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Firewall

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A firewall can either be software-based or hardware-based and is used to help keep a network secure. Its primary objective is to control the incoming and outgoing network traffic by analyzing the data packets and determining whether it should be allowed through or not, based on a predetermined rule set. A network's firewall builds a brigade between an internal network that is assumed to be secure and trusted, and another network, usually an external (inter)network, such as the Internet, that is not assumed to be secure and trusted

Media Converter

A fiber media converter is a simple networking device that make it possible to connect two dissimilar media types such as twisted pair with fiber optic cabling.

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Media Converter

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Network Monitoring

• MRTG• SmokePing

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MRTG

MRTG is free software for monitoring and measuring the traffic load on network links. It allows the user to see traffic load on a network over time in graphical form.

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SmokePing

SmokePing is a latency logging and graphing system. It consists of a daemon process which organizes the latency measurements and a CGI which presents the graphs.

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Network Troubleshooting

• Ping• Traceroute• MTR

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Ping

Ping is a computer network administration utility used to test the reachability of a host on an Internet Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a destination computer.

Ping operates by sending Internet Control Message Protocol (ICMP) echo request packets to the target host and waiting for an ICMP response. In the process it measures the time from transmission to reception (round-trip time) and records any packet loss. The results of the test are printed in the form of a statistical summary of the response packets received, including the minimum, maximum, and the mean round-trip times, and sometimes the standard deviation of the mean.

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The Ping Process1. The source host generates an ICMP protocol data unit. 2. The ICMP PDU is encapsulated in an IP datagram, with the source and destination IP addresses in

the IP header. At this point the datagram is most properly referred to as an ICMP ECHO datagram, but we will call it an IP datagram from here on since that's what it looks like to the networks it is sent over.

3. The source host notes the local time on it's clock as it transmits the IP datagram towards the destination. Each host that receives the IP datagram checks the destination address to see if it matches their own address or is the all hosts address (all 1's in the host field of the IP address).

4. If the destination IP address in the IP datagram does not match the local host's address, the IP datagram is forwarded to the network where the IP address resides.

5. The destination host receives the IP datagram, finds a match between itself and the destination address in the IP datagram.

6. The destination host notes the ICMP ECHO information in the IP datagram, performs any necessary work then destroys the original IP/ICMP ECHO datagram.

7. The destination host creates an ICMP ECHO REPLY, encapsulates it in an IP datagram placing it's own IP address in the source IP address field, and the original sender's IP address in the destination field of the IP datagram.

8. The new IP datagram is routed back to the originator of the PING. The host receives it, notes the time on the clock and finally prints PING output information, including the elapsed time.

The process above is repeated until all requested ICMP ECHO packets have been sent and their responses have been received or the default 2-second timeout expired. The default 2-second timeout is local to the host initiating the PING and is NOT the Time-To-Live value in the datagram.

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Ping Error MessagesMessage:Request timed out. Explanation:The ping command timed out because there was no reply from the host.User Action:Ping your local address 127.0.0.1. This will tell you that TCP is functioning. It does NOT tell you that your network card is functioning. Ping your default gateway or next hop Router. This will show that the router is up. Ping beyond the next hop Router. If the ping fails, the request timed out can mean that the destination host is down or that there is no route back to you. Destination Net Unreachable will show the IP address of the Router that tried to route the packet but did not have a valid route. Message:Destination host unreachable. Explanation:The host that you are trying to ping is down or is not operating on the network.Message:Destination net unreachable. Explanation:The gateway reported that the network running the Internet Control Message Protocol (ICMP) for the IP address entered on the command line could not be reached.User Action:Try again later.

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Ping Error MessagesMessage:TTL expired in transit. Explanation:The TTL value determines the maximum amount of time an IP packet may live in the network without reaching its destination. It is effectively a bound on the number of routers an IP packet may pass through before being discarded. This message indicates that the TTL expired in transit.User Action:Increase the TTL value using the -i parameter with the ping command. Message:Hardware error. User Action:Ping your local address (127.0.0.1) to verify that your workstation is working properly. If you can ping your local address, check the cable connection from your network card to the 10 base T drop. Message:Destination specified is invalid. Explanation:An invalid address has been entered on the command line.User Action:Check the format of the address and try again. Message:Unknown Host.Explanation:This error message indicates that the requested host name cannot be resolved to its IP address; check that the name is entered correctly and that the DNS servers can resolve it.User Action:Check the Connectivity to the DNS Server

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TRACEROUTE

Traceroute is a computer network diagnostic tool for displaying the route (path) and measuring transit delays of packets across an Internet Protocol (IP) network.

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MTRMTR (My traceroute, originally called Matt's traceroute) is computer software which combines the functionality of the traceroute and ping programs in a single network diagnostic tool.

MTR probes routers on the route path by limiting the number of hops individual packets may traverse, and listening to responses of their expiry. It will regularly repeat this process, usually once per second, and keep track of the response times of the hops along the path.

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THANK YOU

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