Musical Instrument Digital Interface (MIDI)

The development of the MIDI system has been a major catalyst in the recent unprecedented explosion of music technology. MIDI has put powerful computer instrument networks and software in the hands of less technically versed musicians and amateurs and has provided new and time-saving tools for computer musicians. The system first appeared in 1982 following an agreement among manufacturers and developers of electronic musical instruments to include a common set of hardware connectors and digital codes in their instrument design. The original goal was to interface instruments of different manufacture to control common functions, such as note events, timing events, pitch bends, pedal information, etc. Though several classes of codes have been added to the MIDI 1.0 Specification (International MIDI Association, 1989) and MIDI applications have grown far beyond the original intent, the basic protocol has remained unchanged. MIDI is a system very much like a player piano roll in that it is used to specify the actions of a synthesizer or other electronic devices, while the tone or effect is generated by the instrument itself.

file transfer protocol (FTP)

File Transfer Protocol, or FTP, is a protocol used for transferring files from one Internet location to another. FTP is the preferred method of exchanging files, because it's faster than other protocols like HTTP. FTP is the method by which you'll upload files into your webhosting account. FTP data is sent and received through port 21. The transfer is asynchronous, and therefore faster.The Original Objectives of FTP are:1. To promote sharing of files (computer programs and/or data),2. To encourage indirect or implicit (via programs) use of remote computers,3. To shield a user from variations in file storage systems among hosts, and4. To transfer data reliably and efficiently. FTP, though usable directly by a user at a terminal, is designed mainly for use by programs.First defined in RFC 172 written in June 1971, the protocol has been through several changes through to the current specification, which is defined in RFC 959. It's worth looking at its basic operation to get a better understanding of how content switching can improve performance and reliability in FTP environments.

HTTP

HTTP stands for Hypertext Transfer Protocol. It's the network protocol used to deliver virtually all files and other data (collectively called resources) on the World Wide Web, whether they're HTML files, image files, query results, or anything else. Usually, HTTP takes place through TCP/IP sockets (and this tutorial ignores other possibilities).A browser is an HTTP client because it sends requests to an HTTP server (Web server), which then sends responses back to the client. The standard (and default) port for HTTP servers to listen on is 80, though they can use any port.

Binary and ASCII transfer

Binary transfers is for binary files, such as executable, graphic or compressed files. ASCII transfers is for text files, such as HTML documents and pure ASCII text (such as notepad files). If you use WS-FTP or CuteFTP as your FTP program, check the AUTO box at the bottom of the program screen to have the software try and determine what method to use automatically. If you transfer Binary files using ASCII transfer method, you will corrupt your files on the server, making them unreadable. If you transfer ASCII files using Binary transfer method you will alter the formatting of the text contained in the file itself. This doesn't seem like such a big deal, until you try to open this file again. Strange things will happen, such as all the carriage returns being stripped out, or if the uploaded HTML or text file needs to be opened by a UNIX-based text editor such as VI or PICO, the user will see a ^M at the end of each line, very ugly and difficult to read.

Binary and ASCII transfer

Binary transfers is for binary files, such as executable, graphic or compressed files. ASCII transfers is for text files, such as HTML documents and pure ASCII text (such as notepad files). If you use WS-FTP or CuteFTP as your FTP program, check the AUTO box at the bottom of the program screen to have the software try and determine what method to use automatically. If you transfer Binary files using ASCII transfer method, you will corrupt your files on the server, making them unreadable. If you transfer ASCII files using Binary transfer method you will alter the formatting of the text contained in the file itself. This doesn't seem like such a big deal, until you try to open this file again. Strange things will happen, such as all the carriage returns being stripped out, or if the uploaded HTML or text file needs to be opened by a UNIX-based text editor such as VI or PICO, the user will see a ^M at the end of each line, very ugly and difficult to read.

Post Office Protocol

Post Office Protocol version 3 (POP3) is an application layer Internet standard protocol used to retrieve email from a remote server to a local client over a TCP/IP connection. Nearly all individual Internet service provider email accounts are accessed via POP3.The earlier versions of the POP protocol, POP (informally called POP1) and POP2, have been thoroughly made obsolete by POP3. In contemporary usage, the less precise term POP almost always means POP3 in the context of email protocols.POP3 and its predecessors are designed to allow end users with intermittent connections such as dial-up connections to retrieve email when connected, and then to view and manipulate the retrieved messages without needing to stay connected. Although most clients have an option to leave mail on server, email clients using POP3 generally connect, retrieve all messages, store them on the user's PC as new messages, delete them from the server, and then disconnect. In contrast, the newer, more capable IMAP email retrieval protocol supports both connected and disconnected modes of operation. Email clients using IMAP generally leave messages on the server until the user explicitly deletes them. This and other facets of IMAP operation allow multiple clients to access the same mailbox. Most email clients can be configured to use either POP3 or IMAP to retrieve messages; however, ISP support for IMAP is not as common.UIDL (Unique IDentification Listing) is a POP3 command typically used in the implementation of a client leave mail on server option. POP3 commands identify specific messages by their ordinal number on the mail server. This creates a problem for a client intending to leave messages on the server, since these message numbers may change from one connection to the server to another. For example if there were five messages when last connected and message #3 is deleted by a different client, when next connecting the last two messages' numbers decrement by one! Luckily, the POP3 RFC specifies a method of avoiding numbering issues. Basically, the server assigns an arbitrary and unique string of characters in the range 0x21 to 0x7E to the message. This ID is never reused for any message. When a POP3-compatible email client connects to the server, it can use the UIDL command to get the current mapping from these message IDs to the ordinal message numbers. Using this mapping the client can then determine which messages it has yet to download, which saves time when downloading.Whether using POP3 or IMAP to retrieve messages, clients use the SMTP protocol to send messages. Email clients are sometimes referred to as either POP or IMAP clients, but in both cases SMTP is also used.Email attachments and non-ASCII text are nearly universally conveyed in email in accordance with MIME formatting rules. Neither POP3 nor SMTP require email to be MIME formatted, but since essentially all internet email is MIME formatted POP clients by default must also understand and use MIME. IMAP is designed to assume email is MIME formatted.Like many other older Internet protocols, POP3 originally supported only an unencrypted login mechanism. Although plain text transmission of passwords in POP3 is still common, POP3 currently supports several authentication methods to provide varying levels of protection against illegitimate access to a user's email. One such method (defined in the base specification as an optional command) is APOP, which uses MD5 in an attempt to avoid replay attacks and disclosure of a shared secret; clients implementing APOP include Mozilla, Thunderbird, Eudora, and Novell Evolution. POP3 can also support IMAP authentication methods via the AUTH extension.It is also possible to encrypt POP3 traffic using SSL.POP3 works over a TCP/IP connection using network port 110.

List of Common Header

· Apparently-To: Messages with many recipients sometimes have a long list of headers of the form "Apparently-To: rth@bieberdorf.edu" (one line per recipient). These headers are unusual in legitimate mail; they are normally a sign of a mailing list, and in recent times mailing lists have generally used software sophisticated enough not to generate a giant pile of headers.· Bcc: (stands for "Blind Carbon Copy") If you see this header on incoming mail, something is wrong. It's used like Cc: (see below), but does not appear in the headers. The idea is to be able to send copies of email to persons who might not want to receive replies or to appear in the headers. Blind carbon copies are popular with spammers, since it confuses many inexperienced users to get email that doesn't appear to be addressed to them.· Cc: (stands for "Carbon Copy", which is meaningful if you remember typewriters) This header is sort of an extension of "To:"; it specifies additional recipients. The difference between "To:" and "Cc:" is essentially connotative; some mailers also deal with them differently in generating replies.· Comments: This is a nonstandard, free-form header field. It's most commonly seen in the form "Comments: Authenticated sender is ". A header like this is added by some mailers (notably the popular freeware program Pegasus) to identify the sender; however, it is often added by hand (with false information) by spammers as well. Treat with caution.· Content-Transfer-Encoding: This header relates to MIME, a standard way of enclosing non-text content in email. It has no direct relevance to the delivery of mail, but it affects how MIME-compliant mail programs interpret the content of the message.· Content-Type: Another MIME header, telling MIME-compliant mail programs what type of content to expect in the message.· Date: This header does exactly what you'd expect: It specifies a date, normally the date the message was composed and sent. If this header is omitted by the sender's computer, it might conceivably be added by a mail server or even by some other machine along the route. It shouldn't be treated as gospel truth; forgeries aside, there are an awful lot of computers in the world with their clocks set wrong.· Errors-To: Specifies an address for mailer-generated errors, like "no such user" bounce messages, to go to (instead of the sender's address). This is not a particularly common header, as the sender usually wants to receive any errors at the sending address, which is what most (essentially all) mail server software does by default.· From (without colon) This is the "envelope From" discussed above.· From: (with colon) This is the "message From:" discussed above.· Message-Id: (also Message-id: or Message-ID:) The Message-Id is a more-or-less unique identifier assigned to each message, usually by the first mailserver it encounters. Conventionally, it is of the form "gibberish@bieberdorf.edu", where the "gibberish" part could be absolutely anything and the second part is the name of the machine that assigned the ID. Sometimes, but not often, the "gibberish" includes the sender's username. Any email in which the message ID is malformed (e.g., an empty string or no @ sign), or in which the site in the message ID isn't the real site of origin, is probably a forgery.· In-Reply-To: A Usenet header that occasionally appears in mail, the In-Reply-To: header gives the message ID of some previous message which is being replied to. It is unusual for this header to appear except in email directly related to Usenet; spammers have been known to use it, probably in an attempt to evade filtration programs.· Mime-Version: (also MIME-Version:) Yet another MIME header, this one just specifying the version of the MIME protocol that was used by the sender. Like the other MIME headers, this one is usually eminently ignorable; most modern mail programs will do the right thing with it.· Newsgroups: This header only appears in email that is connected with Usenet---either email copies of Usenet postings, or email replies to postings. In the first case, it specifies the newsgroup(s) to which the message was posted; in the second, it specifies the newsgroup(s) in which the message being replied to was posted. The semantics of this header are the subject of a low-intensity holy war, which effectively assures that both sets of semantics will be used indiscriminately for the foreseeable future.· Organization: A completely free-form header that normally contains the name of the organization through which the sender of the message has net access. The sender can generally control this header, and silly entries like "Royal Society for Putting Things on Top of Other Things" are commonplace.· Priority: An essentially free-form header that assigns a priority to the mail. Most software ignores it. It is often used by spammers, usually in the form "Priority: urgent" (or something similar), in an attempt to get their messages read.· Received: Discussed in detail above.· References: The References: header is rare in email except for copies of Usenet postings. Its use on Usenet is to identify the "upstream" posts to which a message is a response; when it appears in email, it's usually just a copy of a Usenet header. It may also appear in email responses to Usenet postings, giving the message ID of the post being responded to as well as the references from that post.· Reply-To: Specifies an address for replies to go to. Though this header has many legitimate uses (perhaps your software mangles your From: address and you want replies to go to a correct address), it is also widely used by spammers to deflect criticism. Occasionally a naive spammer will actually solicit responses by email and use the Reply-To: header to collect them, but more often the Reply-To: address in junk email is either invalid or an innocent victim.· Sender: This header is unusual in email (X-Sender: is usually used instead), but appears occasionally, especially in copies of Usenet posts. It should identify the sender; in the case of Usenet posts, it is a more reliable identifier than the From: line.· Subject: A completely free-form field specified by the sender, intended, of course, to describe the subject of the message.· To: The "message To: "described above. Note that the To: header need not contain the recipient's address!· X-headers is the generic term for headers starting with a capital X and a hyphen. The convention is that X-headers are nonstandard and provided for information only, and that, conversely, any nonstandard informative header should be given a name starting with "X-". This convention is frequently violated.· X-Confirm-Reading-To: This header requests an automated confirmation notice when the message is received or read. It is typically ignored; presumably some software acts on it.· X-Distribution: In response to problems with spammers using his software, the author of Pegasus Mail added this header. Any message sent with Pegasus to a sufficiently large number of recipients has a header added that says "X-Distribution: bulk". It is explicitly intended as something for recipients to filter against.· X-Errors-To: Like Errors-To:, this header specifies an address for errors to be sent to. It is probably less widely obeyed.· X-Mailer: (also X-mailer:) A freeform header field intended for the mail software used by the sender to identify itself (as advertising or whatever). Since much junk email is sent with mailers invented for the purpose, this field can provide much useful fodder for filters.· X-PMFLAGS: This is a header added by Pegasus Mail; its semantics are nonobvious. It appears in any message sent with Pegasus, so it doesn't obviously convey any information to the recipient that isn't covered by the X-Mailer: header.· X-Priority: Another priority field, used notably by Eudora to assign a priority (which appears as a graphical notation on the message).· X-Sender: The usual email analogue to the Sender: header in Usenet news, this header purportedly identifies the sender with greater reliability than the From: header. In fact, it is nearly as easy to forge, and should therefore be viewed with the same sort of suspicion as the From: header.· X-UIDL: This is a unique identifier used by the POP protocol for retrieving mail from a server. It is normally added between the recipient's mail server and the recipient's actual mail software; if mail arrives at the mail server with an X-UIDL: header, it is probably junk (there's no conceivable use for such a header, but for some unknown reason many spammers add one)

XHTML

XHTML stands for eXtensable HyperText Markup Language and is a cross between HTML and XML. XHTML was created for two main reasons:To create a stricter standard for making web pages, reducing incompatibilities between browsersTo create a standard that can be used on a variety of different devices without changes The great thing about XHTML, though, is that it is almost the same as HTML, although it is much more important that you create your code correctly. You cannot make badly formed code to be XHTML compatible. Unlike with HTML (where simple errors (like missing out a closing tag) are ignored by the browser), XHTML code must be exactly how it is specified to be. This is due to the fact that browsers in handheld devices etc. don't have the power to show badly formatted pages so XHTML makes sure that the code is correct so that it can be used on any type of browser.XHTML is a web standard which has been agreed by the W3C and, as it is backwards compatible, you can start using it in your webpages now. Also, even if you don't think its really necessary to update to XHTML yet, there are three very good reasons to do so:It will help you to create better formatted code on your siteIt will make your site more accessable (both in the future and now due to the fact that it will also mean you have correct HTML and most browsers will show your page better)XHTML is planned to replace HTML 4 in the future There is really no excuse not to start writing your web pages using XHTML as it is so easy to pick up and will bring many benefits to your site.

Networking cable

Cable is the medium through which data is transmitted from one network device to another. There are several types of cables, which are commonly used with LANs. The growth of Local Area Networks (LANs) and client server computing has produced a great increase in the amount of cabling used.In many cases, a network will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Also the common transmission losses such as attenuation have to be taken care of while choosing the type of cable used.

Networking cable

Cable is the medium through which data is transmitted from one network device to another. There are several types of cables, which are commonly used with LANs. The growth of Local Area Networks (LANs) and client server computing has produced a great increase in the amount of cabling used.In many cases, a network will use a variety of cable types. The type of cable chosen for a network is related to the network's topology, protocol, and size. Also the common transmission losses such as attenuation have to be taken care of while choosing the type of cable used.

types of cable

A cable is a group of insulated conductors enclosed within an Insulator. The main function of a cable is transmitting signal from one point to another. They can be broadly categorized into 5 types depending on their attenuation, cost, immunity to EMI, skilled labor required for installation etc.Given below is the list of cable types used in networking.CoaxialRG6RG8RG58RG59Plenum/PVCUTPCAT3CAT5/eCAT6STPFiberSingle-modeMulti-mode

Coaxial cable

Coaxial cable is commonly used in the cable television industry. This has also gained popularity in use for computer networks, such as Ethernet networks. Coaxial cable is highly resistant to signal interference and can support greater distance between network devices than twisted pair cable.Coaxial cable consists of a single core copper wire surrounded by an insulator and enclosed in a copper mesh, finally covered inside an outside insulationThe main features co-axial cable:When compared to twist pair cable a coaxial cable can support greater cable ths between network devices.They are highly resistant to signal interference.It costs less that other cables.Not flexible and it is more difficult to terminate

Plenum Cable

Plenum grade cable is a cable that uses fire resistant material such as Teflon for insulation. This type of material in the insulation minimizes the amount of smoke in case of fire. However, plenum cabling are more expensive and less flexible than a PVC cable. This type of cable is generally used in space reserver for air circulation in air conditioning and heating systems

twisted cable

The twisting of two insulated wires around each other is known as twisted pair cables. Cables that use twisted pair of wires reduce the Crosstalk between them to a great extent.As shown in the image, the pair of wires may be surrounded either by a shield, or similar pairs of wires. Each pair is uniquely color coded when packaged in multiple pairs. Different uses such as Analog, Digital, and Ethernet require different pair multiples.Twisted pair wiring is commonly used to connect telephones and in computer network technology and are classified according to their maximum transmission frequencies. Today, there are basically only two types used and they are Cat3 and Cat5.Some features of Twisted pair cabling are:It is flexible and easy to terminate.For Cat 5e/6/7 UTP the maximum segment length is 100 meters.10BaseT refers to the specifications for unshielded twisted pair cable (Category 3, 4, or 5) carrying Ethernet signals. Category 6 is relatively new and is used for gigabit connections.Twisted pair cables are available in two variants:Shielded Twisted Pair (STP) andUnshielded Twisted pair (UTP)

Fibre-optic cable

It is a cabling technology that uses optical fibers to carry digital data signals in the form of modulated pulses of light. The core of fiber-optic cable is made of glass or plastic and the cladding that are enclosed by a protective coating. Outer insulating jacket is made of Teflon or PVC. Kevlar fibers are used to strengthen the cable and prevent from breakages.A brief overview of the advantages of fiber-optic cable over coaxial and twisted pair:Speed: Fiber optic networks operate at high speeds in the gigabits range.Bandwidth: High-capacity data transmission.Distance: Due to lack of attenuation Signals can be transmitted over long distances without using repeaters.Resistance: Greater resistance to outside interferences such as radios, motors and electromagnetic noise.Expensive and very fragile.

TCP/IP

TCP and IP were developed by a Department of Defense (DOD) research project to connect a number different networks designed by different vendors into a network of networks (the "Internet"). It was initially successful because it delivered a few basic services that everyone needs (file transfer, electronic mail, remote logon) across a very large number of client and server systems. Several computers in a small department can use TCP/IP (along with other protocols) on a single LAN. The IP component provides routing from the department to the enterprise network, then to regional networks, and finally to the global Internet. On the battlefield a communications network will sustain damage, so the DOD designed TCP/IP to be robust and automatically recover from any node or phone line failure. This design allows the construction of very large networks with less central management. However, because of the automatic recovery, network problems can go undiagnosed and uncorrected for long periods of time.As with all other communications protocol, TCP/IP is composed of layers:IP - is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from department to organization to region and then around the world.TCP - is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received.Sockets - is a name given to the package of subroutines that provide access to TCP/IP on most systems.