SPEC-India

This field seems to confuse many people, so let’s state what it does up front. Time to Live (TTL) indicates the amount of time that a datagram is allowed to stay on the network. It is not used by the routers to count up to 16 to know when to discard a packet. There are two functions for the TTL field: to limit the lifetime of a TCP segment (transmitted data) and to end routing loops.

 The initial TTL entry is set by the originator of the packet, and it varies. To be efficient, a routing update will set this field to a 1 (RIP will). Why set it to anything else, when that update is sent only to its local segments? Multicast protocols set it to many different sizes to limit the scope of the multicast. For normal usage, many applications set it to 32 or 64 (2 and 4 times the size of a RIP network). Time to live is a field that is used by routers to ensure that a packet does not endlessly loop around the network. This field (currently defined as the number of seconds) is set at the transmitting station and then, as the datagram passes through each router, it will be decremented. With the speed of today’s routers, the usual decrement is 1. One algorithm is that the receiving router will notice the time a packet arrives, and then, when it is forwarded, the router will decrement the field by the number of seconds the datagram sat in a queue waiting for forwarding. Not all algorithms work this way. A minimum decrement will always be 1. The router that decrements this field to 0 will discard the packet and inform the originator of the datagram (through the ICMP protocol) that the TTL field expired and the datagram did not make it to its destination.

 The time–to–live field may also be set to a certain time (i.e., initialized to a low number like 64) to ensure that a packet stays on the network for only a set time. Some routers allow the network administrator to set a manual entry to decrement. This field may contain any number from 0 to 255 (an 8–bit field).

Remote terminal emulation is provided through the TELNET protocol. For new users of the TCP/IP protocol, this is not Telenet, a packet switching technology using the CCITT standard X.25. It is pronounced TELNET. This is an application–level protocol that allows terminal emulation to pass through a network to a remote network station. TELNET runs on top of the TCP protocol and allows a network workstation to appear as a local device to a remote device (i.e., a host).

 The File Transfer Protocol (FTP) is similar to TELNET in terms of control, but this protocol allows for data files to be reliably transferred on the Internet. FTP resides on top of TCP and uses it as its transport mechanism. TFTP is a simplex file transfer protocol (based on an unreliable transport layer called UDP), and is primarily used for boot loading of configuration files across an internet.

 The Simple Mail Transport Protocol (SMTP) is an electronic mail system that is robust enough to run on the entire Internet system. This protocol allows for the exchange of electronic mail between two or more systems on an internet. Along with a system known as Post Office Protocol, individual users can retrieve their mail from centralized mail repositories.

 The Domain Name Service (DNS) is a centralized name service that allows users to establish connections to network stations using human–readable names instead of cryptic network addresses. It provides a name–to–network address translation service. There are many other functions of DNS, including mail server name to IP address translation. Mail service would not exist if not for the DNS.

 The Boot Protocol (BOOTP) and Dynamic Host Configuration Protocol (DHCP) allow for management of IP parameters on a network. These protocols do not provide for router configurations but endstation configurations. BOOTP was the original protocol that provided not only a workstation’s IP address but possibly its operating image as well. DHCP is best known for its management allocation scheme of IP addresses and is a superset of BOOTP that provides extended functions of IP as well as IP address management.

Grid computing is all about using the untapped resources of computers connected to a network. IBM perhaps defines it most succinctly: Grid computing is applying resources from many computers in a network-at the same time-to a single problem.

The development of the World Wide Web revolutionized the way we think about and access information. We really don’t think twice anymore about logging on to the web and pulling up information on almost any topic imaginable. What the Web did for information, Grid computing aims to do for computation. Grid computing is really the next logical evolution of the Internet.

 The Internet began with TCP/IP and networking; then came communication with e-mail, followed by information sharing with the World Wide Web. Next will be the advent of grid computing, the sharing of actual computer resources, such as memory, storage, and processing power.

 It is almost mind boggling to imagine the types of applications that could be developed if access to distributed supercomputers, mass storage and vast memory were as straightforward as access to the web. So there are several ways of looking at Grid Computing: as a way to connect the computational power of all the big computers together and give access to companies and academia alike; as a way to connect ALL the computers both big and small and derive computational efficiencies (think peer-to-peer networks); as the next logical step in providing a computational platform for Web Services; as a business on demand or computing as a utility model which IBM and others are touting.

 All of the above are in effect true. Through a variety of different means and technologies, computers will learn to share each other’s processors, storage and memory, much as they share communications and information today, and applications will take advantage of these resources. While we are far from realizing the full effects that Grid computing will bring, it is upon us and there are both short-term and long-term ramifications for the enterprise.

 The actual brains of the computers will be connected, not just the arteries. This means that users will begin to experience the Internet as a seamless computational universe. Software applications, database sessions, and video and audio streams will be reborn as services that live in cyberspace.

 Once plugged into the grid, a desktop machine will draw computational power from all the other machines in the grid. The Internet itself will become a computing platform. Grid computing is the next logical step for the Internet to take.

What XML is?

1. Very easy to use and code. The complete specification document is less than 40 pages long. XML is designed to be easier to code than either HTML or full SGML.
2. It is an open standard - XML is a subset of SGML
3. a learning curve - XML was designed by people with many years of experience, including members of the governing bodies for both SGML and HTML.
4. By its very name - extensible - you have the power to invent and use your own tags and, if you choose, share them with others.
5. Very efficient - XML can re-use document elements and fragments, so you only have to transmit them once.
6. Ready to use - web browsers can read XML today, just like HTML. You can use hyperlinks and images and multimedia, exactly as you do in HTML.
7. Fully international - it has built-in support for texts in the major global alphabets, including a method to signal what language and encoding is being used.

What XML is not?

1. It is not a  replacement for good old HTML. HTML is an excellent tool for displaying documents across a network. XML is designed for information providers who want to expand the horizons - something HTML is not geared up for.
2. It is not a replacement for SGML. To make XML simple, many features of SGML
3. It is not constrained to a defined set of tags
4. It is not clunky - you can use it secure in the knowledge that it is as efficient as possible.

Before you start putting everything in cache, you need to consider the following benefits and risks.

 The benefits include

1. A reduced number of round trips to the data source, such as the database server, keeping the server resources more available for other operations.
2. An increase in the number of users supported, due to a faster response time to each user’s request.

 The risks include

1. Easily filling a computer’s memory, which is relatively small, if you put a large amount of data in cache. As the memory gets full, the performance starts to decline, eventually leading to an unacceptable response time from the server.
2. Problems in a server farm environment, when we cache information in the server’s memory, where various Web pages for the same user session may be served by different Web servers.
3. No guarantee of faster performance. It all depends on how effectively you manage objects in memory.

 In general, caching is useful when you have a large amount of relatively static information. A prime candidate for caching is product catalog information. There is little value in using SQL to search the database to retrieve the same list of products for each user who visits your Web site. It is a waste of database and network resources (assuming that the database is installed on a separate server than the Web site). You can easily store information like this in data cache. However, before you go wild and put your entire product catalog in one large XML DOM object (or DataSet object), consider this fact: Even though it is easier to get access to an object stored in memory, it is not necessarily faster to search that object.

 A prime example of this fact is the DataSet object. The ADO.NET enthusiasts love to glorify this object by focusing on its ability to provide in-memory cache of the database. They often neglect to tell their listeners about the slow performance of its search mechanism.

There are a variety of techniques that may be used to improve the efficiency of a program. These techniques are usually applied to the intermediate representation. If several optimization techniques are written as transformations of the intermediate representation, then these techniques can be applied over and over until some termination condition is reached.

 The following list describes some standard optimizations:

1.  Common Subexpression Elimination: If a program calculates the same value more than once and the compiler can detect this, then it may be possible to transform the program so that the value is calculated only once and stored for subsequent use.
2.  Copy Propagation: If a program contains an assignment such as x=y, then it may be possible to change subsequent statements to refer to y instead of to x and to eliminate the assignment.
3.  Dead-Code Elimination: If some sequence of instructions can never be reached, then it can be eliminated from the program.
4.  Loop Optimizations: There are several techniques that can be applied to remove instructions from loops. For example, if some expression appears inside a loop but has the same value on each pass through the loop, then the expression can be moved outside the loop.
5.  In-Lining Function Calls: If a program calls function f, it is possible to substitute the code for f into the place where f is called. This makes the target program more efficient, as the instructions associated with calling a function can be eliminated, but it also increases the size of the program. The most important consequence of in-lining function calls is usually that they allow other optimizations to be performed by removing jumps from the code.

RFID has really been set alight by the endorsement of the technology by the retail industry. RFID tags are miniscule microchips, which already have shrunk to half the size of a grain of coffee. RFID tags work by listening for a brief radio signal and then respond with their own, completely unique ID code. The beauty of these devices is that they require no batteries - they are powered by the original radio signal.

Historically, companies, like Wal-Mart, needed a way of capturing accurate, real-time information about the products they make, move and sell. RFID offers that capability and helps companies boost supply chain efficiencies, reduce inventories, limit theft, improve product availability and add convenience for consumers.

Wal-Mart is not alone, Tesco, the biggest retail chain in the UK have also adopted this technology by installing Smart Shelves with networked RFID readers. 

The brains behind RFID were driven by the Auto-ID Center, based at MIT, an unusual cooperative effort between academia and global companies to develop the Electronic Product Code (EPC), a system for identifying objects and sharing information about them securely over the Internet.

Proponents of the technology insist that this is not a big brother technology - the range limitations ensure this - once a customer leaves a store the unique identifier code becomes useless. If the RFID tags are used on packaging then once the packaging is discarded there should be no problem.

A wireless technology that enables short-range wireless data connections between devices. The name came from: Harald Bluetooth, a Viking and king of Denmark from the years 940 to 981, was renown for his ability to help people communicate. During his reign, he united Denmark and Norway.

Bluetooth wireless technology is a worldwide specification for low-cost radio that provides links between mobile computers, mobile phones, other portable handheld devices, and connectivity to the Internet. There is a written specification developed, published and promoted by the Bluetooth Special Interest Group (SIG). This SIG includes Agere, Ericsson, IBM, Intel, Microsoft, Motorola, Nokia and Toshiba, and hundreds of Associate and Adopter member companies. In mid 2002, the Bluetooth SIG established its global headquarters in Overland Park, Kansas, USA.

The Bluetooth wireless technology is essentially designed to replace cables between cell phones, laptops, and other computing and communication devices within a 10-meter range. When Bluetooth wireless technology connects devices to each other, they become paired. An example of such device pairings includes:

1. Your wireless headset connecting to the cell phone in your pocket
2. Your PDA automatically synchronizes with your computer when you walk into the office.

And this is only the tip of the iceberg. Bluetooth Technology is poised to expand into areas such as industrial automation, gaming and delivery tracking. It is not too far off from when you will use a Bluetooth pen to write on an image board located in a different office. 

Bluetooth has already managed to immerse itself into the automotive industry. Your mobile phone headset will be wirelessly connected to the car’s in-built audio system enabling completely hands-free

GSM phones use encrypted technology that enables secure voice and data transfer during calls. GSM technology uses an algorithm to ensure the authenticity of the caller and the integrity of the channel, even when you are roaming in a foreign country.

The most interesting, and potentially contentious area of wireless security is that concerning wireless LANs or Wi-Fi networks, these are fast becoming the connection method of choice. Wireless signals do not recognize corporate or geographical boundaries and are only limited by the propagation configuration of the network. Even in an office environment you will find small areas or “blind spots” where the coverage is very weak or non-existent. So, it is possible for the random surfer to “happen upon” on someone else’s network. How can one protect against this happening?

Wireless local area networks use spread-spectrum technology - a technique that makes the radio signals difficult to intercept. Most Wi-Fi systems also include a form of user logon and password protection. Of course, the spread spectrum signals can be intercepted with a relatively simple wireless card and many networks do not properly set up the password feature and will allow ready access to anyone. The fact that “employees” have to go through some form of physical security before they can access the network only adds to the notion that wireless networks may not be as secure as equipment manufacturers would have us believe.

The problem with wireless security is essentially a technical issue with the way the signals are encrypted. The original wireless LANs (WLANs) used the Wireless Encryption Protocol (WEP). This was then replaced in late 2002 with the Wi-Fi Protected Access (WPA). Essentially, WPA offered improved data encryption through the use of temporal key integrity protocol (TKIP). The TKIP feature scrambles the keys using a hashing algorithm and ensures that the keys have not been tampered with. WEP only uses a static key that is seldom changed by users. This cryptographic weakness caused many of the security breaches in WLANs because intruders could, with relative ease, generate an encryption key and access a wireless network.

While WPA offers enhanced security features over WEP, not all industry observers are completely satisfied. A recent problem was highlighted with WPA concerning the use of poorly chosen passwords for a network. Criminals intent on compromising a WLAN can use simple dictionary software to overcome the system password. In fairness, this weakness only manifests itself when short, text-based keys are used and does not signify a fault in the WPA protocol. WLAN manufacturers can circumvent this problem by incorporating the ability to generate random keys across the network and putting in place user requirements concerning the length and style of passwords.

Microsoft responded to this potential threat by providing a Windows XP download that alters the way the operating systems communicates with the Wi-Fi network - using separately generated keys for each system user rather than one, albeit encrypted, key for the network connection.

Web Services are basically a set of tools and protocols, which enable software applications to communicate, pass data and issue commands to each other over the Internet or any other network. Web Services are a kind of plumbing that connects different programs together using a network and can be used both inside the organization and to integrate with other organizations.

Unlike websites, which are pages designed to be viewed in a browser by a person, a Web service is designed to be accessed directly by another service or software application.

There’s a pretty good chance your business is dependant on its IT systems and the data steams those systems produce. Web services are likely to become the standard for connecting and integrating these systems and the conduit for converging all these data streams in one place.

One of the core ideas behind Web Services it that it reduces the complexity of business integration and offers companies the ability to use a core set of standards and best-of-breed technologies. This means you can leverage the many investments in Internet technologies and training you may have made over the last few years and allows IT managers to spend more time on the underlying infrastructure that makes your business more efficient and less time on the actual “plumbing.”

Web Services is, at its simplest, an XML transfer over HTTP protocol. This is the message and the transport mechanism. As we get deeper in the specification we encounter the concept on an “envelope” or SOAP (Simple Object Access Protocol), which basically adds levels of protection and accountability to the transaction. We also see directory services and listing protocols so companies can, in theory, automatically search directories for services provided by other companies and automatically negotiate for and use these services. Protocols like eBXML (electronic business XML) essentially round out the picture by creating a secure, robust and “corporate” standard for organizations to connect to each other via Web Services.

Remember Web services are not the be all and end all. Web services can be viewed as the middle men. Without robust, relevant and functional applications behind them they become quite irrelevant. Companies should view web services as a complement to what they already have; a way to get more out of the stuff you’ve already invested in, NOT as a replacement!