Medical School Exams…

Once upon a time, a Sardar applied to Medical School needless to say he never made it –

do you know why ????

These are the answers he gave …

ANTIBODY – against everyone

ARTERY – the study of fine paintings

BACTERIA – back door to a cafeteria

COMA – punctuation mark

DIAGNOSIS – person with a slanted nose

DILATE – the late British princess

GALLBLADDER – bladder in a girl

GENES – blue denim

HERNIA – she is close by

HYMEN – greeting to several males

IMPOTENT – distinguished, well-known

LABOR PAIN – hurt at work

LACTOSE – person without digits on the foot

LIPOSUCTION – a French kiss

LYMPH – walk unsteadily

MICROBES – small dressing gowns

OBESITY – city of Obe

SECRETION – hiding anything

TABLET – small table

ULTRASOUND – radical noise

CAESARIAN SECTION – a district in Rome

CARDIOLOGY – advanced study of playing cards

CAT SCAN – searching for lost kitty

CHRONIC – neck of a crow

The right PING!!

I am a total network freak and just love to network computers and do all sorts of R&D on it.. Yest, when I wanted to Remote Login on a Machine, I just couldnt do it.. Then called for “GOD” and he asked me to use “PING”.. So finally my “neck” savor told me the problem and i rectified the errors in IP Address..

Well, most of US definately must have or will have to use “PING” at one point or other.. So here is something to give you and Inside Story on How does Ping work..

  • The source device generates an ICMP protocol data unit.
  • The ICMP PDU is encapsulated in an IP datagram, with the source and destination IP addresses in the IP header.
  • The source machine notes the local time on it’s clock as it transmits the IP Datagram towards the destination. Each machine that receives the datagram checks the destination address to see if it matches their own, or is the ‘all hosts’ address.
  • If the destination IP address in the IP datagram does not match the local machine’s address, the datgram is forwarded to the network where the IP address resides.
  • The destination machine receives the packet, finds a match between itself and the destination address in the IP packet.
  • The destination machine notes the ICMP information in the ICMP ECHO, performs any necessary work, and destroys the complete original IP/ICMP Echo packet.
  • The destination machine creates an ICMP Echo Reply, encapsulates it in IP placing it’s own address in the source IP address field, and the original sender’s IP address in the destination field of the IP datagram.
  • The packet is routed back to the originator of the first ICMP Echo, who receives it, notes the time on the clock, prints PING output information, including the elapsed time.
  • The process above is repeated until all requested Echo packets have been sent, and responses have been received or timed out.

    Note that since ICMP requires responses, a fully functioning duplex communication environment (a downlink and uplink path) must be in place and be functioning for the PING to work.

    PING does not work where there is a single, one way link.

    What is UDP?

    This one is also one of the imp Protocols. Its always compared with TCP/IP…..

    UDP

    User Datagram Protocol (UDP) provides an unreliable packetized data transfer service between endpoints on an internet. UDP depends on IP to move packets around the network on its behalf.

    UDP does not guarantee to actually deliver the data to the destination, nor does it guarantee that data packets will be delivered to the destination in the order in which they were sent by the source, nor does it guarantee that only one copy of the data will be delivered to the destination. UDP does guarantee data integrity, and it does this by adding a checksum to the data before transmission. (Some machines run with UDP checksum generation disabled, in which case data corruption or truncation can go undetected. Very few people think this is a good idea.)

    What is IP?

    Continuing with different protocols, here is the one which everyone of us should know about.. The basic Protocol of “World Wide Web“…..

    Internet Protocol

    Internet Protocol (IP) is the central, unifying protocol in the TCP/IP suite. It provides the basic delivery mechanism for packets of data sent between all systems on an internet, regardless of whether the systems are in the same room or on opposite sides of the world. All other protocols in the TCP/IP suite depend on IP to carry out the fundamental function of moving packets across the internet.

    In terms of the OSI networking model, IP provides a Connectionless Unacknowledged Network Service, which means that its attitude to data packets can be characterised as “send and forget”. IP does not guarantee to actually deliver the data to the destination, nor does it guarantee that the data will be delivered undamaged, nor does it guarantee that data packets will be delivered to the destination in the order in which they were sent by the source, nor does it guarantee that only one copy of the data will be delivered to the destination.

    Because it makes so few guarantees, IP is a very simple protocol. This means that it can be implemented fairly easily and can run on systems that have modest processing power and small amounts of memory. It also means that IP demands only minimal functionality from the underlying medium (the physical network that carries packets on behalf of IP) and can be deployed on a wide variety of networking technologies.

    The no-promises type of service offered by IP is not directly useful to many applications. Applications usually depend on TCP or UDP to provide assurances of of data integrity and (in TCP’s case) ordered and complete data delivery.

    What is SNMP?

    SNMP Protocol Overview

    The Simple Network Management Protocol (SNMP) is essentially a request-reply protocol running over UDP (ports 161 and 162), though TCP operation is possible. SNMP is an asymmetric protocol, operating between a management station (smart) and an agent (dumb). The agent is the device being managed –

    all its software has to do is implement a few simple packet types and a generic get-or-set function on its MIB variables. The management station presents the user interface. Simple management stations can be built with UNIX command-line utilities. More complex (and expensive) ones collect

    MIB data over time and use GUIs to draw network maps.

    An SNMP operation takes the form of a Protocol Data Unit (PDU), basically a fancy word for packet. Version 1 SNMP supports five possible PDUs:

    • GetRequest / SetRequest supplies a list of objects and, possibly, values they are to be set to (SetRequest). In either case, the agent returns a GetResponse.

    • GetResponse informs the management station of the results of a GetRequest or SetRequest by returning an error indication and a list of variable/value bindings.

    • GetNextRequest is used to perform table transversal,

      and in other cases where the management station does not know the exact MIB name of the object it desires. GetNextRequest does not require an exact name to be specified; if no object exists of the specified name, the next object in the MIB is returned. Note that to support this, MIBs must be strictly ordered sets (and are).

    • Trap is the only PDU sent by an agent on its own initiative. It is used to notify the management station of an unusual event that may demand further attention (like a link going down). In version 2, traps are named in MIB space. Newer MIBs specify management objects that control how traps are sent.

    What is IMAP?

    Well, POP3 was done.. But then I though it would be real good to write stuff about IMAP.. So guys, for all you wanting to know about this protocol, here is the answer…

    IMAP (Internet Mail Access Protocol)

    A method of accessing electronic mail or bulletin board messages that are kept on a (possibly shared) mail server. In other words, it permits a “client” email program to access remote message stores as if they were local. For example, email stored on an IMAP server can be manipulated from a desktop computer at home, a workstation at the office, and a notebook computer while traveling, without the need to transfer messages or files back and forth between these computers.

    IMAP synchronizes the messages with the server with the e-mail client by downloading just the subject and header information from the new messages (instead of the entire message). When a message is read, the body of the message is then sent to the e-mail client but the message remains on the IMAP server. Now if a user moves messages into folders, the messages are saved on the server, not on the user’s computer.

    Advantages:

    1) Can manipulate persistent message status flags.

    2) Can support concurrent upsates and access to shared mailboxes.

    3) Especially useful management over low speed links. More efficient than POP3.

    4) Save valuable bandwidth, because when you check your mail, all you download is headers: you don’t download any message until you ask to read it. Read or download any part of a MIME message without downloading the other parts – no more waiting for attachments to download before you can read your mail.

    5) Access and manipulate your mail and all your mailboxes (mail folders) from anywhere – work, home, on the road, even using someone else’s computer – with total convenience and transparency, without any confusion about what you’ve read, where you’ve stored it, and so on.

    Disadvantages:

    1) More complicated to implement on the server

    2) Less software which supports the IMAP protocol (like older versions of Eudora).

    What is POP3?

    At school, we have a subject on Networking. One of the most important aspect of it was “Mail Protocols”. Suddenly my Prof, goes insane and starts askin questions on POP3, most of which we couldnt answer.. After that lecture, it became a challange to give him a assignment on “What the hell is POP3?”.. So here is the answer to it..

    POP3 (Post Office Protocol):

    The most recent version of a standard protocol for receiving e-mail. POP3 is a client/server protocol in which e-mail is received and held for you by your Internet server. Periodically, you (or your client e-mail receiver) check your mail-box on the server and download any mail. POP3 is built into the Netmanage suite of Internet products and one of the most popular e-mail products, Eudora. It’s also built into the Netscape and Microsoft Internet Explorer browsers.

    This method is designed primarily as an off-line mail reading solution, POP3 e-mail clients require you to “download” all your e-mail before you read it. Basically, POP can be thought of as a “store-and-forward” service.

    Advantages:

    1.) POP is the Simpler protocol; much easier to implement.

    2.) More client software currently available.

    3.) Copies all messages to your local machine every time a connection is made to the server.Thus, if the connection goes down while you’re working, you will still have your messages.

    Disadvantages:

    1.) You must synchronize your local inbox with the server’s mailbox.This can result in downloading new messages over and over (if you save your messages on your server), each time you connect, or can result in messages residing on computers you’ve previously used but to which you may not currently have access. The end result is you are sometimes unable to access all your messages when you need to.

    2.) Slow compared to new protocols.

    What exactly is Centrino Technology from INTEL

    Centrino is, in short, Intel’s name for a a series of hardware features that give Notebook PCs long battery life, wireless data access, and low-voltage processing power, all while focusing on making mobile computers thinner and lighter.


    With Intel Pentium M Processors that use less power, and with new advanced battery technology, Centrino allows you to work longer and smarter. Onboard 802.11 Wi-Fi adapters, including 802.11a, 802.11b & 802.11g, allow you to browse the Internet, check your e-mail, log into home or business networks and more, all without wires tethering you to your desk. Wi-Fi allows you to have wireless networking at speeds up to 54MBPS from your living room, the pool or at the office cafeteria so that you can work wherever you happen to be.

    802 Explained

    Wireless MAN (WMAN)

    A Wireless Metropolitan Area Network; a MAN has historically been used to refer to networks encompassing an area larger than a LAN (such as a city or university campus) but smaller than a WAN (such as a nationwide carrier network).

    Wireless LAN (WLAN)

    A WLAN is now basically a euphemism for any 802.11-based wireless local area, or Wi-Fi, network. Wireless LAN base stations are typically effective for ranges up to 100 meters and can support dozens of users.

    Bluetooth

    A personal area networking technology now standardized by the IEEE 802.15 standard; Bluetooth communications typically occur over a range of 10 meters and consume much lower power than Wi-Fi or WiMAX connections.

    802.11

    The IEEE Wireless Local Area Networking (WLAN) standards effort.

    802.15

    The IEEE Wireless Personal Area Networking (WPAN) standards effort.

    802.16

    The IEEE Wireless Metropolitan Area Networking (WMAN) standards effort.

    802.20

    The IEEE Wireless Wide Area Networking (WWAN) standards effort.

    802.11b

    Often referred to as “Wi-Fi”, 802.11b is the most popular of the 802.11 wireless LAN standards. 802.11b communications occur in the 2.4GHz frequency band and provide speeds up to 11 Mbps.

    802.11a

    Runs at frequencies between 5 GHz and 6 GHz, occupying three separate 100MHz frequency bands in that range, and provides communication speeds up to 54 Mbps. Because it runs in the 5GHz band, 802.11a networks rarely conflict with other wireless devices. 802.11a devices consume more power than their 802.11b counterparts. 802.11a communications maxes out around 60 feet with a base station required every 50 feet.

    802.11g

    Like 802.11b, 802.11g operates in the 2.4GHz frequency band but offers communication speeds up to 54 Mbps. It offers the advantages of 802.11b, albeit at a higher cost.

    802.11e

    Offers Quality of Service (QoS) capabilities, while maintaining backwards compatibility with 802.11a and 802.11b

    802.16: Broadband Wireless

    The IEEE 802.11 LAN MAN Standard Committee is tasked with developing standards for three types of networks: Personal Area Networks (PANs), Local Area Networks (LANs), and broadband wireless Metropolitan Area Networks (MANs).

    The best-known of these is the wildly popular 802.11 Wireless Local Area Network (WLAN) specification, which has become part of our cultural lexicon, through terms like Wi-Fi and hotspot. The 802.16 standard for MANs, however, has been increasingly in the news lately as products based on it look to be available in the next year.

    The 802.16 standard was initially published in 2001 and a recent enhancement (802.16a) was published in 2003. Originally dubbed the WirelessMAN standard, this term has been subsumed by the more popular WiMAX branding introduced by the WiMAX Forum, a consortium of companies that support and jointly co-market the 802.16 standards. The group also will certify 802.16-compliant products.

    The purpose of 802.16 is to standardize broadband wide area wireless networking for both fixed and mobile connections, offering extremely high bandwidth connections without requiring a line-of-site communications between the device and the broadcast antenna.

    To give an idea of the possibilities offered by 802.16, consider the capabilities made available by the recent 802.16a extension. 802.16a operates in the 2-11GHz frequency band over a theoretical maximum range of 31 miles with a theoretical maximum data transfer rate of 70Mbps. The following table provides a quick comparison to 802.11b:

    802.16a 802.11b
    Frequency Band: 2-11GHz 2.4GHz
    Range ~31 miles ~100 meters
    Data transfer rate: 70 Mbps 11 Mbps
    Number of users: Thousands Dozens

    In actuality, WiMAX is envisioned as a complimentary technology to Wi-Fi and Bluetooth, with each designed to solve a specific problem very well.

    For example, a typical deployment scenario would allow your network provider to deliver WiMAX connectivity to your corporate office, offering T1-level connection speeds and reliability. Internal to your corporate office, you may decide to deploy 802.11 hotspots for laptop and PDA users moving from office to conference room to the company lunchroom. These same laptop and PDA users may then opt to print to a local network printer via Bluetooth, allowing your enterprise to utilize wireless standards and economies of scale throughout.

    While 802.16 clearly meets an industry need, its success is by no means a sure thing. It faces competition from wide area cellular 2.5G/3G technologies such as 1xEVDO (U.S. rollout by Verizon in 2004) and W-CDMA (eventual U.S. rollout announced by Cingular). In addition, the IEEE 802.20 standard, defined for wireless Wide Area Network access, could potentially compete with WiMAX since both standards could be seen as separate solutions to a similar problem (Nextel recently launched a pre-standard 802.20 trial in North Carolina using gear from Flarion Technologies).

    For now, the principal advantage of the still-unratified 802.20 is that is supports mobile devices, a capability not officially supported by 802.16 until the 802.16e standard is ready (possibly in mid-2004, see below). However, because 802.16e builds on the work of 802.16a, it is likely that 802.16e devices will be widely available before 802.20-equipped devices.

    While the 2003 ratification of 802.16a essentially made WiMAX ready for prime time, a host of 802.16 enhancements are planned, including:

    802.16b – Quality Of Service

    802.16c – Interoperability

    802.16d – Builds on 802.16c

    802.16e – Mobile