Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Wake-on-LAN wikipedia , lookup
Computer network wikipedia , lookup
Distributed firewall wikipedia , lookup
Network tap wikipedia , lookup
Airborne Networking wikipedia , lookup
Recursive InterNetwork Architecture (RINA) wikipedia , lookup
Piggybacking (Internet access) wikipedia , lookup
School of Business Eastern Illinois University Review for Exam 4 © Abdou Illia, Fall 2005 School of Business Eastern Illinois University The Internet 3 The Internet addressing system Network deliver messages based on network addresses – Host The Internet has two addressing systems for hosts IP addresses. Example: 139.67.8.3 Host names (or domain names or Unique Resource Locators). Example: eiu.edu Host IP Address 4 IP addresses – – – Are really strings of 32 bits (1s and 0s) Example: 10000000101010100001000100001101 Usually represented by four number segments separated by dots: dotted decimal notation Example: 128.171.17.13 Official addresses for hosts 127.18.47.145 127.47.17.47 5 Assigning Parts Most Organizations have multiple Segments within the Organizational Network So, usually Local Part is broken in two parts – – a Segment Part to represent each segment Remaining Bits are the Host Part, designating a particular station on that segment Local Part Network Part Segment Part IP Address (32 bits total) Host Part 6 IP address Position Place Value Bit Decimal (N) (2N) Binary 10100011 = Decimal 163 Note: Starts with 0 7 6 5 4 3 2 1 0 128 64 32 16 8 4 2 1 1 0 1 0 0 0 1 1 128 0 32 0 0 0 2 1 163 7 Network classes The value of the first octet in an IP address determines the Network class Class Leftmost bits Class A 0xxx Class B 10xx Class C 110x Network Part Length Address range 8 bits 16 bits 24 bits 0.x.x.x to 127.x.x.x 128.0.x.x to 191.255.x.x 192.0.0.x to 223.255.255.x Position (N) 1) For each of the following IP addresses, give the class and the network bits. 10101010111110000101010100000001 01010100111110000101010100000001 2) To which class belong Eastern’s network? (Net. Part =139.67) 7 6 5 4 3 2 1 0 Place Value (2N) 128 64 32 16 8 4 2 1 Bit Decimal Summary Questions 8 1. a) Distinguish between IP address and host name. b) Which is the official address of a host? c) Does a server host need an IP address? d) Does your home PC need an IP address when you are on the Internet? e) Does a server host need a host name? f) Does your home PC need a host name when you are on the Internet? 2. Using the conversion system on slide #10, convert the following IP address to dotted decimal notation: 10101010 11110000 11001100 01010101. (Spaces are included to facilitate reading.) 9 Summary Questions 3. a) What are the three parts in IP addresses? b) What part(s) do border routers look at to determine whether the destination host is within the network or outside of it? 4. a) Who assigns the Network part? b) The Segment part? c) The Host part? 5. a) When do we need DNS? b) What information do you send in a DNS request message? c) What information do you receive in a DNS response message? 4. a) What is autoconfiguration? b) What information do we get back, at a minimum, in an autoconfiguration response message? c) What other information may we get back? Other questions 10 Make sure you are able to answer questions in Internet exercises available in the Notes’ section of the course web site. You can get the files containing these questions through the following links: InternetExercise.doc IPAddressExercise1.doc IPAddressExercise2.doc Network Management Availability 12 Availability: probability that a particular component or system will be available during a fixed time period Availability is function of: – – Mean time between failures (Given by manufacturer or generated based on past performance) Mean time to repair (Found in studies or in our archives) Mean time between failures (MTBF) is the average time a device or system will operate before it fails. Mean time to repair (MTTR) is the average time necessary to repair a failure Availability Standard equation: A(t) = a/(a+b) + b/(a+b) x e-(a+b)t in which: a = 1/MTTR b = 1/MTBF e = natural log function t = the time interval Approximation equation: Availability% = (Total available time – Downtime)/Total available time 13 Availability A(t) = a/(a+b) + b/(a+b) x e-(a+b)t 14 Suppose we want to calculate the availability of a modem that has a MTBF of 3000 hours and a MTTR of 1 hour. The availability of this modem for an 8-hour period is: a = 1/1 b = 1/3000 = 0.00033 A(8 hours) =1/(1 + 0.00033) + 0.00033/(1 + 0.00033) x e-(1 + 0.00033)8 = 0.9997 + 0.00033 x 0.000335 = 0.9997 Q: What will be the availability of the modem if the Approximation equation is used? Availability 15 A component has been operating continuously for three months. During that time, it has failed twice, resulting in downtime of 4.5 hours. Calculate the availability of the component during that threemonth period using the Approximation method. Availability To calculate the availability of a system of components: – – Calculate the availability of each component Find the product of all availabilities Example: If a network has tree devices with availabilities of 0.992, 0.894, and 0.999, the availability of the network is: 0.992 x 0.894 x 0.999 = 0.886 16 Reliability 17 Reliability: probability that a component or system will be operational for the duration of a transaction time t. Reliability is function of: – – Mean time between failures Transaction time Mean time between failures (MTBF) is the average time a device or system will operate before it fails. Transaction time is the time interval of operation to complete a given transaction. 18 Reliability Reliability is defined by the equation: R(t) = e -bt in which: b = 1/MTBF t = the time interval of the operation Reliability 19 What is the reliability of a modem if the MTBF is 3000 hours and a transaction takes 20 minutes, or 1/3 of an hour (0.333 hours): R(t) = e -bt b = 1/MTBF = 1/3000 t = 0.333 R(0.333 hours) = e -(1/3000)(0.333) = e -0.000111 = 0.99989 Q: If a component has a MTBF of 500 hours and a transaction takes 4 seconds, calculate the reliability of the component