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We said that grid computing is now based upon Internet protocols.

We said that grid computing is now based upon Internet protocols. So let’s first review some well-known Internet technologies. It is expected that the audience knows this information, but it is included for completeness. If you have laptop, can follow alone with simple exercises.

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We said that grid computing is now based upon Internet protocols.

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  1. We said that grid computing is now based upon Internet protocols. • So let’s first review some well-known Internet technologies. • It is expected that the audience knows this information, but it is included for completeness. • If you have laptop, can follow alone with simple exercises. ITCS 4010 Grid Computing, 2005, UNC-Charlotte, B. Wilkinson, slides 2 version 0.1.

  2. Networked Computers, Internet and World Wide Web Technology - BasicsSome really basic stuff!

  3. Network Interfaces Computers connect to the Internet through a network interface (mostly Ethernet). MAC (Media Access Controller) address Each network interface has a unique 48-bit address called a MAC address assigned during manufacture of the interface. Allocation of MAC addresses controlled by IEEE Registration Authority.

  4. Internet Protocol (IP) Address Slightly higher level than MAC addresses. Also assigned to interfaces. Example 129.49.82.1 (IP version 4). Divided into fields to allow various network decoding arrangements. IP address can be static or dynamically changing. Mapped to MAC address with a software table.

  5. Network Typically connection through a switch Unique MAC address and an assigned IP address NIC Computer

  6. TCP-IP Network Protocol(Transmission Control Protocol/Internet • Standard that establishes basic low level rules for networked computers to communicate and pass data. • Higher level protocols build on top of TCP/IP.

  7. Some Network Protocols (on top of TCP/IP) Telnet: An insecure Internet protocol that allows you to connect to another computer. FTP: File Transmission Protocol -- Insecure protocol to exchange files. SMTP: Simple Mail Transfer Protocol -- For email HTTP: Hypertext Transfer Protocol -- Basic way to access web pages (see later)

  8. Secure Connections • Secure connections needed in many computer related activities, including e-business and grid computing. • Telnet and FTP are very insecure - information is transmitted in clear text.

  9. SSL Protocol(Secure Socket Layer) • Proposed by Netscape Communications and adopted widely - Latest version SSL 3.0. • Uses Public Key Cryptography - see later in course. • Can be used with FTP (SFTP) and other protocols (e.g. HTTPS). • Transport Layer Security protocol (TLS) subsequently proposed to SSL - no major differences.

  10. Ports • In addition to IP addresses that identify the host computer (actually the interface), a port number is used to identify the process (application) that will handle requests with a given protocol.

  11. “Well-known” ports Used for processes for handling standard protocols and requests. Examples • FTP uses 20 for data and 21 for control • telnet uses port 23 • SMTP uses port 25 • HTTP uses port 80

  12. Applications telnet HTTP FTP 23 80 Port numbers 20/21 TCP UDP 06 02 User Datagram Protocol IP TCP/IP “stack” 0800 Ethernet driver Network interface Network

  13. “Ephemeral” Ports(Short-lived ports) • Allocated to client applications. • Allocation of port numbers in Linux/Unix or Windows system can be found with the netstat command – we’ll try this later.

  14. FTP server FTP protocol Telnet protocol TCP protocol IP protocol Servers(Network services) Implementation of a protocol with a set of capabilities. Example - FTP server

  15. World Wide Web • Started in earnest in early 1990’s when HTTP developed at CERN and Mosaic browser at NCSA. • HTTP (Hypertext Transfer Protocol) - basic way of accessing web pages. • World wide web expanded at an amazing rate (1 million hosts in 1993 to 200 million+ hosts in 2004.

  16. Domain Name • For ease of use by humans, names are used rather than IP addresses. Example cs.uncc.edu

  17. Conversion between IP address and domain name Done by a domain name service (DNS), a distributed name database.

  18. Using netstat After getting a command line (on Windows, All Programs -> Accessories -> Control prompt), type netstat My response at home : C:>netstat Active Connections Proto Local Address Foreign Address State TCP Barry:1311 localhost:1312 ESTABLISHED TCP Barry:1312 localhost:1311 ESTABLISHED TCP Barry:1297 email.wcu.edu:imap ESTABLISHED TCP Barry:1309 email.wcu.edu:imap CLOSE_WAIT TCP Barry:1437 coitweb.uncc.edu:http CLOSE_WAIT TCP Barry:1445 images.usairways.com:http ESTABLISHED TCP Barry:1555 unccmail.uncc.edu:imap ESTABLISHED C:>

  19. type netstat –n That is, ask for network addresses, ports, and users as numbers. My response at home: C:\>netstat -n Active Connections Proto Local Address Foreign Address State TCP 127.0.0.1:1311 127.0.0.1:1312 ESTABLISHED TCP 127.0.0.1:1312 127.0.0.1:1311 ESTABLISHED TCP 192.168.1.101:1297 152.30.22.216:143 ESTABLISHED TCP 192.168.1.101:1309 152.30.22.216:143 CLOSE_WAIT TCP 192.168.1.101:1437 152.15.42.26:80 CLOSE_WAIT TCP 192.168.1.101:1445 151.193.204.146:80 ESTABLISHED TCP 192.168.1.101:1555 152.15.47.136:143 CLOSE_WAIT TCP 192.168.1.101:1756 192.168.1.100:139 TIME_WAIT C:\>

  20. type netstat –rn that is, ask for route and network addresses C:\>netstat -rn Route Table =========================================================================== Interface List 0x1 ........................... MS TCP Loopback interface 0x2 ...00 11 11 b9 e9 4a ...... Intel(R) PRO/100 VE Network Connection - Packet Scheduler Miniport =========================================================================== =========================================================================== Active Routes: Network Destination Netmask Gateway Interface Metric 0.0.0.0 0.0.0.0 192.168.1.1 192.168.1.101 20 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1 1 192.168.1.0 255.255.255.0 192.168.1.101 192.168.1.101 20 192.168.1.101 255.255.255.255 127.0.0.1 127.0.0.1 20 192.168.1.255 255.255.255.255 192.168.1.101 192.168.1.101 20 224.0.0.0 240.0.0.0 192.168.1.101 192.168.1.101 20 255.255.255.255 255.255.255.255 192.168.1.101 192.168.1.101 1 Default Gateway: 192.168.1.1 =========================================================================== Persistent Routes: None C:\>

  21. Question What is “localhost”? Answer The computer one is logged onto.

  22. Question What is localhost’s IP address on my computer? Answer 127.0.0.1 but on local network the computer has the address 192.168.1.101 (Address 127.0.0.0 used as loopback to itself)

  23. Barry’s home set-up Telephone line DSL modem 166.82.166.82 Also does IP address translation Router/switch wireless Ethernet 192.168.1.101 192.168.1.100 Windows XP computers

  24. URL(Uniform Resource Locator) Way of identifying and accessing a web page: Example http://www.cs.uncc.edu/~abw/index.html “where” Address or name of server “how” Type of transaction (protocol) “what” Resource requested

  25. URI(Uniform Resource Identifier) Identifies a resource and includes URLs, but broader in context. See http://www.w3.org/Addressing/ for more details

  26. Mark-up Languages • A way of describing information in a document. • Standard Generalized Mark-Up Language (SGML) - a specification for a mark-up language ratified in 1986. • Key aspect - using pairs of tags that surround information - a begin tag <tag_name> and a matching end tag </tag_name> . Example <title> CS 493 home page </title>

  27. HyperText Markup Language (HTML) A mark-up language used in web pages. “Hypertext” refers to the text’s ability to link to other documents. “Markup” refers to providing information to tell browser how to display page and other things.

  28. HTML page format <HTML> <HEAD> </HEAD> <BODY> </BODY> </HTML> Signifies an HTML document Head section includes information about document - “metadata” Body section contains text and references to images to be displayed End of document

  29. HTML Tags • Tags specify details such as type of text. Example <B> to start bold text </B> to end bold text <I> to start italic text </I> to end italic text

  30. HTML page <HTML> <HEAD> </HEAD> <BODY> Hello world <I> My name is <B>Barry</B> </I> </BODY> </HTML>

  31. Question What does the previous HTML page display? Answer Hello World My name is Barry

  32. HTML page <HTML> <HEAD> </HEAD> <BODY> <BR> Hello world <P> <I> My name is <B>Barry</B> </I> </BODY> </HTML> Line break tag - some tags in HTML are not in pairs

  33. Attributes Many tags can have attributes which specify something about the body between tag pair. Example <FONT COLOR=red SIZE=3 FACE=Times> This text is displayed in red in Times font, about 12 pt. </FONT> Attributes

  34. More information about HTML See HTML/Javascript course: http://www.cs.uncc.edu/~abw/CS130F04/

  35. Extensible Mark-up LanguageXML • Ratified in 1998 - very important standard mark-up language - a “simplified” SGML. • Developed to represent textual information in a structured manner that could be read and interpreted by a computer. • A foundation for web services and grid services.

  36. Some key aspects of XML • Tags always used in pairs delineate information to make it easy to process. (There is an exception, when the body between the tags holds nothing.) • Tags can be nested. They can have attributes. • Names of tags can be defined broadly at will. (In HTML, tags are predefined.)

  37. XML Application Areas • Used for two applications areas: • Document-centric XML • Data-centric XML

  38. Document-Centric XML • Documents usually meant for humans, although could be processing by computers. • Semi-structured - some tags can be placed more-or-less anywhere, similar to HTML tags.

  39. Sample document-centric XML <H1>Prerequisites for grid computing course</H1> <P><B>Fall 2005</B></P> <LIST> <ITEM>CS I Programming I or equivalent</ITEM> <ITEM>CS II Programming II or equivalent desirable</ITEM> <ITEM>Able to program in Java or learn quickly.</ITEM> <ITEM>Able to program in C/C++ or learn quickly.</ITEM> <ITEM>Able to use Linux system or learn quickly.</ITEM> </LIST> <P> For more information look at <LINK HREF=“outline.xml”>Outline</LINK>.</P>

  40. Data-Centric XML • Usually generated and meant to be read by computer programs. • Structured. • Nesting useful to create a clearly structured and computer-readable document.

  41. Sample data-centric XML <po id=“53912” submitted=“2004-08-05”> <billTo> <name>Department of Computer Science</name> <company>University of North Carolina at Charlotte</company> <street> 9201 University City Blvd.</street> <city>Charlotte</city> <state>NC</state> <postalCode>28223</postalCode> </billTo> <shipTo> <name>Department of Computer Science</name> <company> University of North Carolina at Charlotte </company> <street>9201 University City Blvd.</street> <city>Charlotte</city> <state>NC</state> <postalCode>28223</postalCode> </shipTo> <order> <item sku=“456-CS” quantity=“7”> <description>computer system type 1234 </description> </item> <item sku=“135-GS” quantity=“12”> <description>Unmanaged 16 port GigE switch.</description> </item> </order> </po>

  42. Sample data-centric XML <po id=“53912” submitted=“2004-08-05”> <billTo> <name>Department of Computer Science</name> <company>University of North Carolina at Charlotte</company> <street> 9201 University City Blvd.</street> <city>Charlotte</city> <state>NC</state> <postalCode>28223</postalCode> </billTo>

  43. Quiz 1. (Test of any prior knowledge - answer not in slides.) What is the name of the file, and where exactly is the file stored with the URL given as www.cs.uncc.edu/~abw/ITCS4010F05 and what is its name (be careful) ? Answer

  44. Quiz 2. Why are the FTP and telnet protocols insecure? Answer

  45. Quiz 3. How are tags defined in HTML? Answer

  46. Quiz 4. How are tags defined in XML? Answer

  47. Quiz 5. A pair of XML tags with empty contents: <tag_name></tag_name> can be written as <tag_name/> Under what circumstances would such a construction make sense? Answer

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