Command Prompt

Code:
ANSI.SYS Defines functions that change display graphics, control cursor movement, and reassign keys.
APPEND Causes MS-DOS to look in other directories when editing a file or running a command.
ARP Displays, adds, and removes arp information from network devices.
ASSIGN Assign a drive letter to an alternate letter.
ASSOC View the file associations.
AT Schedule a time to execute commands or programs.
ATMADM Lists connections and addresses seen by Windows ATM call manager.
ATTRIB Display and change file attributes.
BATCH Recovery console command that executes a series of commands in a file.
BOOTCFG Recovery console command that allows a user to view, modify, and rebuild the boot.ini
BREAK Enable / disable CTRL + C feature.
CACLS View and modify file ACL's.
CALL Calls a batch file from another batch file.
CD Changes directories.
CHCP Supplement the International keyboard and character set information.
CHDIR Changes directories.
CHKDSK Check the hard disk drive running FAT for errors.
CHKNTFS Check the hard disk drive running NTFS for errors.
CHOICE Specify a listing of multiple options within a batch file.
CLS Clears the screen.
CMD Opens the command interpreter.
COLOR Easily change the foreground and background color of the MS-DOS window.
COMP Compares files.
COMPACT Compresses and uncompress files.
CONTROL Open control panel icons from the MS-DOS prompt.
CONVERT Convert FAT to NTFS.
COPY Copy one or more files to an alternate location.
CTTY Change the computers input/output devices.
DATE View or change the systems date.
DEBUG Debug utility to create assembly programs to modify hardware settings.
DEFRAG Re-arrange the hard disk drive to help with loading programs.
DEL Deletes one or more files.
DELETE Recovery console command that deletes a file.
DELTREE Deletes one or more files and/or directories.
DIR List the contents of one or more directory.
DISABLE Recovery console command that disables Windows system services or drivers.
DISKCOMP Compare a disk with another disk.
DISKCOPY Copy the contents of one disk and place them on another disk.
DOSKEY Command to view and execute commands that have been run in the past.
DOSSHELL A GUI to help with early MS-DOS users.
DRIVPARM Enables overwrite of original device drivers.
ECHO Displays messages and enables and disables echo.
EDIT View and edit files.
EDLIN View and edit files.
EMM386 Load extended Memory Manager.
ENABLE Recovery console command to enable a disable service or driver.
ENDLOCAL Stops the localization of the environment changes enabled by the setlocal command.
ERASE Erase files from computer.
EXIT Exit from the command interpreter.
EXPAND Expand a M*cros*ft Windows file back to it's original format.
EXTRACT Extract files from the M*cros*ft Windows cabinets.
FASTHELP Displays a listing of MS-DOS commands and information about them.
FC Compare files.
FDISK Utility used to create partitions on the hard disk drive.
FIND Search for text within a file.
FINDSTR Searches for a string of text within a file.
FIXBOOT Writes a new boot sector.
FIXMBR Writes a new boot record to a disk drive.
FOR Boolean used in batch files.
FORMAT Command to erase and prepare a disk drive.
FTP Command to connect and operate on a FTP server.
FTYPE Displays or modifies file types used in file extension associations.
GOTO Moves a batch file to a specific label or location.
GRAFTABL Show extended characters in graphics mode.
HELP Display a listing of commands and brief explanation.
IF Allows for batch files to perform conditional processing.
IFSHLP.SYS 32-bit file manager.
IPCONFIG Network command to view network adapter settings and assigned values.
KEYB Change layout of keyboard.
LABEL Change the label of a disk drive.
LH Load a device driver in to high memory.
LISTSVC Recovery console command that displays the services and drivers.
LOADFIX Load a program above the first 64k.
LOADHIGH Load a device driver in to high memory.
LOCK Lock the hard disk drive.
LOGON Recovery console command to list installations and enable administrator login.
MAP Displays the device name of a drive.
MD Command to create a new directory.
MEM Display memory on system.
MKDIR Command to create a new directory.
MODE Modify the port or display settings.
MORE Display one page at a time.
MOVE Move one or more files from one directory to another directory.
MSAV Early M*cros*ft Virus scanner.
MSD Diagnostics utility.
MSCDEX Utility used to load and provide access to the CD-ROM.
NBTSTAT Displays protocol statistics and current TCP/IP connections using NBT
NET Update, fix, or view the network or network settings
NETSH Configure dynamic and static network information from MS-DOS.
NETSTAT Display the TCP/IP network protocol statistics and information.
NLSFUNC Load country specific information.
NSLOOKUP Look up an IP address of a domain or host on a network.
PATH View and modify the computers path location.
PATHPING View and locate locations of network latency.
PAUSE Command used in batch files to stop the processing of a command.
PING Test / send information to another network computer or network device.
POPD Changes to the directory or network path stored by the pushd command.
POWER Conserve power with computer portables.
PRINT Prints data to a printer port.
PROMPT View and change the MS-DOS prompt.
PUSHD Stores a directory or network path in memory so it can be returned to at any time.
QBASIC Open the QBasic.
RD Removes an empty directory.
REN Renames a file or directory.
RENAME Renames a file or directory.
RMDIR Removes an empty directory.
ROUTE View and configure windows network route tables.
RUNAS Enables a user to execute a program on another computer.
SCANDISK Run the scandisk utility.
SCANREG Scan registry and recover registry from errors.
SET Change one variable or string to another.
SETLOCAL Enables local environments to be changed without affecting anything else.
SETVER Change MS-DOS version to trick older MS-DOS programs.
SHARE Installs support for file sharing and locking capabilities.
SHIFT Changes the position of replaceable parameters in a batch program.
SHUTDOWN Shutdown the computer from the MS-DOS prompt.
SMARTDRV Create a disk cache in conventional memory or extended memory.
SORT Sorts the input and displays the output to the screen.
START Start a separate window in Windows from the MS-DOS prompt.
SUBST Substitute a folder on your computer for another drive letter.
SWITCHES Remove add functions from MS-DOS.
SYS Transfer system files to disk drive.
TELNET Telnet to another computer / device from the prompt.
TIME View or modify the system time.
TITLE Change the title of their MS-DOS window.
TRACERT Visually view a network packets route across a network.
TREE View a visual tree of the hard disk drive.
TYPE Display the contents of a file.
UNDELETE Undelete a file that has been deleted.
UNFORMAT Unformat a hard disk drive.
UNLOCK Unlock a disk drive.
VER Display the version information.
VERIFY Enables or disables the feature to determine if files have been written properly.
VOL Displays the volume information about the designated drive.
XCOPY Copy multiple files, directories, and/or drives from one location to another.
TRUENAME When placed before a file, will display the whole directory in which it exists
TASKKILL It allows you to kill those unneeded or locked up applications

Internet Explorer Shortcuts

CTRL+A - Select all items on the current page
CTRL+D - Add the current page to your Favorites
CTRL+E - Open the Search bar
CTRL+F - Find on this page
CTRL+H - Open the History bar
CTRL+I - Open the Favorites bar
CTRL+N - Open a new window
CTRL+O - Go to a new location
CTRL+P - Print the current page or active frame
CTRL+S - Save the current page
CTRL+W - Close current browser window
CTRL+ENTER - Adds the http://www. (url) .com
SHIFT+CLICK - Open link in new window
BACKSPACE - Go to the previous page
ALT+HOME - Go to your Home page
HOME - Move to the beginning of a document
TAB - Move forward through items on a page
END - Move to the end of a document
ESC - Stop downloading a page
F11 - Toggle full-screen view
F5 - Refresh the current page
F4 - Display list of typed addresses
F6 - Change Address bar and page focus
ALT+RIGHT ARROW - Go to the next page
SHIFT+CTRL+TAB - Move back between frames
SHIFT+F10 - Display a shortcut menu for a link
SHIFT+TAB - Move back through the items on a page
CTRL+TAB - Move forward between frames
CTRL+C - Copy selected items to the clipboard
CTRL+V - Insert contents of the clipboard
ENTER - Activate a selected link
HOME - Move to the beginning of a document
END - Move to the end of a document
F1 - Display Internet Explorer Help

Windows XP Shortcuts

ALT+ (ALT+hyphen) displays the Multiple Document Interface (MDI) child window's System menu
ALT+ENTER View properties for the selected item
ALT+ESC Cycle through items in the order they were opened
ALT+F4 Close the active item, or quit the active program
ALT+SPACEBAR Display the System menu for the active window
ALT+TAB Switch between open items
ALT+Underlined letter Display the corresponding menu
BACKSPACE View the folder one level up in My Computer or Windows Explorer
CTRL+A Select all
CTRL+B Bold
CTRL+C Copy
CTRL+I Italics
CTRL+O Open an item
CTRL+U Underline
CTRL+V Paste
CTRL+X Cut
CTRL+Z Undo
CTRL+F4 Close the active document
CTRL while dragging Copy selected item
CTRL+SHIFT while dragging Create shortcut to selected iteM
CTRL+RIGHT ARROW Move the insertion point to the beginning of the next word
CTRL+LEFT ARROW Move the insertion point to the beginning of the previous word
CTRL+DOWN ARROW Move the insertion point to the beginning of the next paragraph
CTRL+UP ARROW Move the insertion point to the beginning of the previous paragraph
SHIFT+DELETE Delete selected item permanently without placing the item in the Recycle Bin
ESC Cancel the current task
F1 Displays Help
F2 Rename selected item
F3 Search for a file or folder
F4 Display the Address bar list in My Computer or Windows Explorer
F5 Refresh the active window
F6 Cycle through screen elements in a window or on the desktop
F10 Activate the menu bar in the active program
SHIFT+F10 Display the shortcut menu for the selected item
CTRL+ESC Display the Start menu
SHIFT+CTRL+ESC Launches Task Manager
SHIFT when you insert a CD Prevent the CD from automatically playing
WIN Display or hide the Start menu
WIN+BREAK Display the System Properties dialog box
WIN+D Minimizes all Windows and shows the Desktop
WIN+E Open Windows Explorer
WIN+F Search for a file or folder
WIN+F+CTRL Search for computers
WIN+L Locks the desktop
WIN+M Minimize or restore all windows
WIN+R Open the Run dialog box
WIN+TAB Switch between open items

Introduction to BIOS Passwords

The best method to reset a BIOS password depends on what BIOS the computer has. Common BIOS's include AMI, Award, IBM and Phoenix. Numerous other BIOS's do exist, but these are the most common.

Some BIOS's allow you to require a password be entered before the system will boot. Some BIOS's allow you to require a password to be entered before the BIOS setup may be accessed.

The general categories of solutions to reset a BIOS password are:

* Using a Backdoor BIOS Password
* Resetting the BIOS Password using Software
* Resetting the BIOS Password using Hardware
* Vendor Specific Solutions for resetting the BIOS Password

Using a Backdoor BIOS Password

Some BIOS manufacturers implement a backdoor password. The backdoor password is a BIOS password that works, no matter what the user sets the BIOS password to. These passwords are typically used for testing and maintenance. Manufacturers typically change the backdoor BIOS passwords from time to time.
AMI Backdoor BIOS Passwords

Reported AMI backdoor BIOS passwords include A.M.I., AAAMMMIII, AMI?SW , AMI_SW, BIOS, CONDO, HEWITT RAND, LKWPETER, MI, and PASSWORD.
Award Backdoor BIOS Passwords

One reported Award backdoor BIOS password is eight spaces. Other reported Award backdoor BIOS passwords include 01322222, 589589, 589721, 595595, 598598 , ALFAROME, ALLY, ALLy, aLLY, aLLy, aPAf, award, AWARD PW, AWARD SW, AWARD?SW, AWARD_PW, AWARD_SW, AWKWARD, awkward, BIOSTAR, CONCAT, CONDO, Condo, condo, d8on, djonet, HLT, J256, J262, j262, j322, j332, J64, KDD, LKWPETER, Lkwpeter, PINT, pint, SER, SKY_FOX, SYXZ, syxz, TTPTHA, ZAAAADA, ZAAADA, ZBAAACA, and ZJAAADC.
Phoenix Backdoor BIOS Passwords

Reported Phoenix BIOS backdoor passwords include BIOS, CMOS, phoenix, and PHOENIX.
Backdoor BIOS Passwords from Other Manufacturers

Reported BIOS backdoor passwords for other manufacturers include:

Manufacturer BIOS Password
VOBIS & IBM merlin
Dell Dell
Biostar Biostar
Compaq Compaq
Enox xo11nE
Epox central
Freetech Posterie
IWill iwill
Jetway spooml
Packard Bell bell9
QDI QDI
Siemens SKY_FOX
SOYO SY_MB
TMC BIGO
Toshiba Toshiba

Remember that what you see listed may not be the actual backdoor BIOS password, this BIOS password may simply have the same checksum as the real backdoor BIOS password. For Award BIOS, this checksum is stored at F000:EC60.

OSI model

Introduction

The Open Systems Interconnection (OSI) model is a reference tool for understanding data communications between any two networked systems. It divides the communications processes into seven layers. Each layer both performs specific functions to support the layers above it and offers services to the layers below it. The three lowest layers focus on passing traffic through the network to an end system. The top four layers come into play in the end system to complete the process.

An Overview of the OSI Model

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A networking model offers a generic means to separate computer networking functions into multiple layers. Each of these layers relies on the layers below it to provide supporting capabilities and performs support to the layers above it. Such a model of layered functionality is also called a “protocol stack” or “protocol suite”. Protocols, or rules, can do their work in either hardware or software or, as with most protocol stacks, in a combination of the two. The nature of these stacks is that the lower layers do their work in hardware or firmware (software that runs on specific hardware chips) while the higher layers work in software. The Open System Interconnection model is a seven-layer structure that specifies the requirements for communications between two computers. The ISO (International Organization for Standardization) standard 7498-1 defined this model. This model allows all network elements to operate together, no matter who created the protocols and what computer vendor supports them.

The main benefits of the OSI model include the following:

• Helps users understand the big picture of networking
• Helps users understand how hardware and software elements function together
• Makes troubleshooting easier by separating networks into manageable pieces
• Defines terms that networking professionals can use to compare basic functional relationships on different networks
• Helps users understand new technologies as they are developed
• Aids in interpreting vendor explanations of product functionality

Layer 1 – The Physical Layer

The physical layer of the OSI model defines connector and interface specifications, as well as the medium (cable) requirements. Electrical, mechanical, functional, and procedural specifications are provided for sending a bit stream on a computer network.

Components of the physical layer include:

• Cabling system components
• Adapters that connect media to physical interfaces
• Connector design and pin assignments
• Hub, repeater, and patch panel specifications
• Wireless system components
• Parallel SCSI (Small Computer System Interface)
• Network Interface Card (NIC)

In a LAN environment, Category 5e UTP (Unshielded Twisted Pair) cable is generally used for the physical layer for individual device connections. Fiber optic cabling is often used for the physical layer in a vertical or riser backbone link. The IEEE, EIA/TIA, ANSI, and other similar standards bodies developed standards for this layer.

Note: The Physical Layer of the OSI model is only part of a LAN (Local Area Network).

Layer 2 – The Data link Layer

Layer 2 of the OSI model provides the following functions:

• Allows a device to access the network to send and receive messages
• Offers a physical address so a device’s data can be sent on the network
• Works with a device’s networking software when sending and receiving messages
• Provides error-detection capability

Common networking components that function at layer 2 include:

• Network interface cards
• Ethernet and Token Ring switches
• Bridges

NICs have a layer 2 or MAC address. A switch uses this address to filter and forward traffic, helping relieve congestion and collisions on a network segment.

Bridges and switches function in a similar fashion; however, bridging is normally a software program on a CPU, while switches use Application-Specific Integrated Circuits (ASICs) to perform the task in dedicated hardware, which is much faster.

Layer 3 – Network Layer

Layer 3, the network layer of the OSI model, provides an end-to-end logical addressing system so that a packet of data can be routed across several layer 2 networks (Ethernet, Token Ring, Frame Relay, etc.). Note that network layer addresses can also be referred to as logical addresses.

Initially, software manufacturers, such as Novell, developed proprietary layer 3 addressing. However, the networking industry has evolved to the point that it requires a common layer 3 addressing system. The Internet Protocol (IP) addresses make networks easier to both set up and connect with one another. The Internet uses IP addressing to provide connectivity to millions of networks around the world.

To make it easier to manage the network and control the flow of packets, many organizations separate their network layer addressing into smaller parts known as subnets. Routers use the network or subnet portion of the IP addressing to route traffic between different networks. Each router must be configured specifically for the networks or subnets that will be connected to its interfaces.

Routers communicate with one another using routing protocols, such as Routing Information Protocol (RIP) and Open version of Shortest Path First (OSPF), to learn of other networks that are present and to calculate the best way to reach each network based on a variety of criteria (such as the path with the fewest routers). Routers and other networked systems make these routing decisions at the network layer

When passing packets between different networks, it may become necessary to adjust their outbound size to one that is compatible with the layer 2 protocol that is being used. The network layer accomplishes this via a process known as fragmentation. A router’s network layer is usually responsible for doing the fragmentation. All reassembly of fragmented packets happens at the network layer of the final destination system.

Two of the additional functions of the network layer are diagnostics and the reporting of logical variations in normal network operation. While the network layer diagnostics may be initiated by any networked system, the system discovering the variation reports it to the original sender of the packet that is found to be outside normal network operation.

The variation reporting exception is content validation calculations. If the calculation done by the receiving system does not match the value sent by the originating system, the receiver discards the related packet with no report to the sender. Retransmission is left to a higher layer’s protocol.

Some basic security functionality can also be set up by filtering traffic using layer 3 addressing on routers or other similar devices.

Layer 4 – The Transport Layer

Layer 4, the transport layer of the OSI model, offers end-to-end communication between end devices through a network. Depending on the application, the transport layer either offers reliable, connection-oriented or connectionless, best-effort communications.

Some of the functions offered by the transport layer include:

• Application identification
• Client-side entity identification
• Confirmation that the entire message arrived intact
• Segmentation of data for network transport
• Control of data flow to prevent memory overruns
• Establishment and maintenance of both ends of virtual circuits
• Transmission-error detection
• Realignment of segmented data in the correct order on the receiving side
• Multiplexing or sharing of multiple sessions over a single physical link

The most common transport layer protocols are the connection-oriented TCP Transmission Control Protocol (TCP) and the connectionless UDP User Datagram Protocol (UDP).







Layer 5 – The Session Layer

Layer 5, the session layer, provides various services, including tracking the number of bytes that each end of the session has acknowledged receiving from the other end of the session. This session layer allows applications functioning on devices to establish, manage, and terminate a dialog through a network. Session layer functionality includes:

• Virtual connection between application entities
• Synchronization of data flow
• Creation of dialog units
• Connection parameter negotiations
• Partitioning of services into functional groups
• Acknowledgements of data received during a session
• Retransmission of data if it is not received by a device

Layer 6 – The Presentation Layer

Layer 6, the presentation layer, is responsible for how an application formats the data to be sent out onto the network. The presentation layer basically allows an application to read (or understand) the message. Examples of presentation layer functionality include:

• Encryption and decryption of a message for security
• Compression and expansion of a message so that it travels efficiently
• Graphics formatting
• Content translation
• System-specific translation

Layer 7 – The Application Layer

Layer 7, the application layer, provides an interface for the end user operating a device connected to a network. This layer is what the user sees, in terms of loading an application (such as Web browser or e-mail); that is, this application layer is the data the user views while using these applications. Examples of application layer functionality include:

• Support for file transfers
• Ability to print on a network
• Electronic mail
• Electronic messaging
• Browsing the World Wide Web

Layers 8,9 and 10

Whether a designed to be a humorous extension or a secret technician code, layers 8, 9, and 10 are not officially part of the OSI model. They refer to the non-technical aspects of computer networking that often interfere with the smooth design and operation of the network.

Layer 8 is usually considered the “office politics” layer. In most organizations, there is at least one group who is favored, at least temporarily, by management and receives “special” treatment. When it comes to networking, this may mean that this group always has the latest and/or fastest equipment and highest speed network links.

Layer 9 is generally referred to as the “blinders” layer. This layer applies to organizational managers who have already decided, usually with little or no current information, to dictate a previously successful network plan. They may say things such as:

“It worked in my last company, so we will use it here.”

“Everybody says this is the right solution.”

“I read in an airline magazine that this was the best way to do it so that is what we will do.”

What these managers seem to forget is that they are paying a highly qualified staff to provide them with useful information. These managers bypass planning in order to make a quick decision.

Layer 10, the “user” layer, is in every organization. But users are much more than a layer. While they are one of the reasons the network exists, users can also be a big part of the need for troubleshooting. This is especially true when the users have computers at home and have decided to “help” the network administrator or manager by making changes to the network without consulting the network staff. Equally challenging is the user who “didn’t do anything” when the network segment in his/her immediate vicinity suddenly stopped working. In these cases, the layer 10 identification coincides with layer 10 troubles (and the “ID10T” label some technicians have used).

TCP/IP Model Overview

The OSI model describes computer networking in seven layers. While there have been implementations of networking protocol that use those seven layers, most networks today use TCP/IP. But, networking professionals continue to describe networking functions in relation to the OSI layer that performs those tasks.

The TCP/IP model uses four layers to perform the functions of the seven-layer OSI model.

The network access layer is functionally equal to a combination of OSI physical and data link layers (1 and 2). The Internet layer performs the same functions as the OSI network layer (3).

Things get a bit more complicated at the host-to-host layer of the TCP/IP model. If the host-to-host protocol is TCP, the matching functionality is found in the OSI transport and session layers (4 and 5). Using UDP equates to the functions of only the transport layer of the OSI model.

The TCP/IP process layer, when used with TCP, provides the functions of the OSI model’s presentation and application layers (6 and 7). When the TCP/IP transport layer protocol is UDP, the process layer’s functions are equivalent to OSI session, presentation, and application layers (5, 6, and 7).

Equipment at the Layers

Some of the layers use equipment to support the identified functions. Hub related activity is “Layer One”. The naming of some devices designates the functional layer such as “Layer Two Switch” or “Layer Three Switch”. Router functions focus on “Layer Three”. User workstations and servers are often identified with “Layer Seven”.

Speed up Mac OS X Leopard

After a year and a half of running Mac OS X Snow Leopard things have become extraordinarily slow on my MacBook Pro. After a quick googling on the subject of how to speed up Mac OS X Leopard I have decided to write my own brief tutorial on a handful of things you can do to effectively increase the performance of OS X. This is meant as a programmer’s quick reference guide so if you are not technically savvy you may want to google “performance tune mac os x” for more verbose explanations.

13 Mac Performance Tuning Applications and Tips

1. Run the Mac OS X disk repair utility location in Applications > Utilities > Disk Utility and then run repair disk permissions. See this article on the repair functions of the disk utility.
2. Download and run Monolingual to remove all the additional languages that are built into OS X by default and you are likely to never use. I removed everything except English, Spanish, German and French since those are core languages on websites I sometimes frequent.
3. Download and run XSlimmer to remove all unnecessary PPC (PowerPC) code from Universal Binaries. Only use this if you are using an Intel based Mac. Additionally it is worthwhile noting that I had problems with Photoshop after slimming the application, so perhaps avoid using XSlimmer on CS3 or CS4.
4. Download and run OnyX.Run the daily, weekly and monthly scripts. Clear out all log files.
5. Removing unnecessary login items by going to System Preferences > Accounts > Login Items. Note that in order to actually remove a login item you need to select the item and then hit the minus button at the bottom of the preferences screen.
6. Even though Mac OS X has a journaled filesystem that should automatically handle defragmentation on the fly, it doesn’t do a great job of keeping the drive from becoming fragmented. iDefrag.solves these problems and more, by defragmenting and optimizing your Mac’s filesystem at boot time. All you have to do is restart your computer, run the iDefrag boot DVD and it will defragment the entire hard-drive. I noticed a substantial performance boost (I would say up to around 20%) after using this.
7. Minimize by using the scale effect by going to System Preferences > Dock and changing the default from the Genie effect to the Scale effect. Also you can uncheck “animate opening applications” to boost performance.
8. Ensure you have a minimum of 10% disk space available so that OS X can run effectively. If you don’t have this much space free try using GrandPerspective to determine what is using space on your hard drive and what you might be able to delete.
9. Remove fonts that you don’t use. You can do this by going to the finder and removing fonts from your home folder > library > fonts.
10. Turn off Universal Access by navigating to System Preferences > Universal Access and turn off anything you’re not using.
11. Turn off Bluetooth by navigating to to System Preferences > Bluetooth.
12. Turn off Internet Sharing by navigating to to System Preferences > Sharing > Internet.
13. Check the Activity Monitor located in Applications > Utilities > Activity Monitor to see if there is anything running that is consuming processing or memory resources. This should go without saying.

Command Line Performance Tuning Tips

1. You can speed up TCP connections by opening the terminal.app and typing pico /etc/sysctl.conf and adding the following lines to the file:
   net.inet.tcp.mssdflt=1460
net.inet.tcp.sendspace=262144
net.inet.tcp.recvspace=262144
net.inet.udp.recvspace=74848
net.inet.udp.maxdgram=65535
2. You can speed up SSH connections by opening the terminal.app and typing pico ~/.ssh_config and adding the following lines to the file:
   host *
controlmaster auto
controlpath /tmp/ssh-%r@%h:%p
   It should be noted here that this may cause some glitches as I have run into some odd controlmaster errors after implementing this command. You can always try it and remove the code if it gives you problems.
3. Disable dashboard by opening up the terminal.app and running the command:
   defaults write com.apple.dashboard mcx-disabled -boolean YES
   and then run killall dock to restart the dock.
4. To optimize firefox’s tab/bookmarks/cache databases on OSX, close firefox, open terminal.app and run #cd ~/Library/Caches/Firefox/Profiles; for i in */*.sqlite; do sqlite3 $i VACUUM;done; cd ~/Library/Application\ Support/Firefox/Profiles; for i in */*.sqlite; do sqlite3 $i VACUUM;done;

Network topology

Physical topologies

The mapping of the nodes of a network and the physical connections between them – i.e., the layout of wiring, cables, the locations of nodes, and the interconnections between the nodes and the cabling or wiring system^[

Classification of physical topologies

Point-to-point

The simplest topology is a permanent link between two endpoints (the line in the illustration above). Switched point-to-point topologies are the basic model of conventional telephony. The value of a permanent point-to-point network is the value of guaranteed, or nearly so, communications between the two endpoints. The value of an on-demand point-to-point connection is proportional to the number of potential pairs of subscribers, and has been expressed as Metcalfe's Law.

Permanent (dedicated)

Easiest to understand, of the variations of point-to-point topology, is a point-to-point communications channel that appears, to the user, to be permanently associated with the two endpoints. Children's "tin-can telephone" is one example, with a microphone to a single public address speaker is another. These are examples of physical dedicated channels.

Within many switched telecommunications systems, it is possible to establish a permanent circuit. One example might be a telephone in the lobby of a public building, which is programmed to ring only the number of a telephone dispatcher. "Nailing down" a switched connection saves the cost of running a physical circuit between the two points. The resources in such a connection can be released when no longer needed, for example, a television circuit from a parade route back to the studio.

Switched:

Using circuit-switching or packet-switching technologies, a point-to-point circuit can be set up dynamically, and dropped when no longer needed. This is the basic mode of conventional telephony.

Bus

Linear bus

The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has exactly two endpoints (this is the 'bus', which is also commonly referred to as the backbone, or trunk) – all data that is transmitted between nodes in the network is transmitted over this common transmission medium and is able to be received by all nodes in the network virtually simultaneously (disregarding propagation delays)

Note: The two endpoints of the common transmission medium are normally terminated with a device called a terminator that exhibits the characteristic impedance of the transmission medium and which dissipates or absorbs the energy that remains in the signal to prevent the signal from being reflected or propagated back onto the transmission medium in the opposite direction, which would cause interference with and degradation of the signals on the transmission medium (See Electrical termination).

'Distributed bus

The type of network topology in which all of the nodes of the network are connected to a common transmission medium which has more than two endpoints that are created by adding branches to the main section of the transmission medium – the physical distributed bus topology functions in exactly the same fashion as the physical linear bus topology (i.e., all nodes share a common transmission medium).

Notes:

1.) All of the endpoints of the common transmission medium are normally terminated with a device called a 'terminator' (see the note under linear bus).

2.) The physical linear bus topology is sometimes considered to be a special case of the physical distributed bus topology – i.e., a distributed bus with no branching segments.

3.) The physical distributed bus topology is sometimes incorrectly referred to as a physical tree topology – however, although the physical distributed bus topology resembles the physical tree topology, it differs from the physical tree topology in that there is no central node to which any other nodes are connected, since this hierarchical functionality is replaced by the common bus.

Star

The type of network topology in which each of the nodes of the network is connected to a central node with a point-to-point link in a 'hub' and 'spoke' fashion, the central node being the 'hub' and the nodes that are attached to the central node being the 'spokes' (e.g., a collection of point-to-point links from the peripheral nodes that converge at a central node) – all data that is transmitted between nodes in the network is transmitted to this central node, which is usually some type of device that then retransmits the data to some or all of the other nodes in the network, although the central node may also be a simple common connection point (such as a 'punch-down' block) without any active device to repeat the signals.

Notes:

1.) A point-to-point link (described above) is sometimes categorized as a special instance of the physical star topology – therefore, the simplest type of network that is based upon the physical star topology would consist of one node with a single point-to-point link to a second node, the choice of which node is the 'hub' and which node is the 'spoke' being arbitrary

2.) After the special case of the point-to-point link, as in note 1.) above, the next simplest type of network that is based upon the physical star topology would consist of one central node – the 'hub' – with two separate point-to-point links to two peripheral nodes – the 'spokes'.

3.) Although most networks that are based upon the physical star topology are commonly implemented using a special device such as a hub or switch as the central node (i.e., the 'hub' of the star), it is also possible to implement a network that is based upon the physical star topology using a computer or even a simple common connection point as the 'hub' or central node – however, since many illustrations of the physical star network topology depict the central node as one of these special devices, some confusion is possible, since this practice may lead to the misconception that a physical star network requires the central node to be one of these special devices, which is not true because a simple network consisting of three computers connected as in note 2.) above also has the topology of the physical star.

4.) Star networks may also be described as either broadcast multi-access or nonbroadcast multi-access (NBMA), depending on whether the technology of the network either automatically propagates a signal at the hub to all spokes, or only addresses individual spokes with each communication.

Extended star

A type of network topology in which a network that is based upon the physical star topology has one or more repeaters between the central node (the 'hub' of the star) and the peripheral or 'spoke' nodes, the repeaters being used to extend the maximum transmission distance of the point-to-point links between the central node and the peripheral nodes beyond that which is supported by the transmitter power of the central node or beyond that which is supported by the standard upon which the physical layer of the physical star network is based.

Note: If the repeaters in a network that is based upon the physical extended star topology are replaced with hubs or switches, then a hybrid network topology is created that is referred to as a physical hierarchical star topology, although some texts make no distinction between the two topologies.

Distributed Star

A type of network topology that is composed of individual networks that are based upon the physical star topology connected together in a linear fashion – i.e., 'daisy-chained' – with no central or top level connection point (e.g., two or more 'stacked' hubs, along with their associated star connected nodes or 'spokes').

Ring

The type of network topology in which each of the nodes of the network is connected to two other nodes in the network and with the first and last nodes being connected to each other, forming a ring – all data that is transmitted between nodes in the network travels from one node to the next node in a circular manner and the data generally flows in a single direction only.

Mesh

The value of fully meshed networks is proportional to the exponent of the number of subscribers, assuming that communicating groups of any two endpoints, up to and including all the endpoints, is approximated by Reed's Law.

Full

Fully connected

The type of network topology in which each of the nodes of the network is connected to each of the other nodes in the network with a point-to-point link – this makes it possible for data to be simultaneously transmitted from any single node to all of the other nodes.

Note: The physical fully connected mesh topology is generally too costly and complex for practical networks, although the topology is used when there are only a small number of nodes to be interconnected.

Partial

Partially connected

The type of network topology in which some of the nodes of the network are connected to more than one other node in the network with a point-to-point link – this makes it possible to take advantage of some of the redundancy that is provided by a physical fully connected mesh topology without the expense and complexity required for a connection between every node in the network.

Note: In most practical networks that are based upon the physical partially connected mesh topology, all of the data that is transmitted between nodes in the network takes the shortest path (or an approximation of the shortest path) between nodes, except in the case of a failure or break in one of the links, in which case the data takes an alternate path to the destination. This requires that the nodes of the network possess some type of logical 'routing' algorithm to determine the correct path to use at any particular time.

Tree

Also known as a hierarchical network.

The type of network topology in which a central 'root' node (the top level of the hierarchy) is connected to one or more other nodes that are one level lower in the hierarchy (i.e., the second level) with a point-to-point link between each of the second level nodes and the top level central 'root' node, while each of the second level nodes that are connected to the top level central 'root' node will also have one or more other nodes that are one level lower in the hierarchy (i.e., the third level) connected to it, also with a point-to-point link, the top level central 'root' node being the only node that has no other node above it in the hierarchy (The hierarchy of the tree is symmetrical.) Each node in the network having a specific fixed number, of nodes connected to it at the next lower level in the hierarchy, the number, being referred to as the 'branching factor' of the hierarchical tree.

1.) A network that is based upon the physical hierarchical topology must have at least three levels in the hierarchy of the tree, since a network with a central 'root' node and only one hierarchical level below it would exhibit the physical topology of a star.

2.) A network that is based upon the physical hierarchical topology and with a branching factor of 1 would be classified as a physical linear topology.

3.) The branching factor, f, is independent of the total number of nodes in the network and, therefore, if the nodes in the network require ports for connection to other nodes the total number of ports per node may be kept low even though the total number of nodes is large – this makes the effect of the cost of adding ports to each node totally dependent upon the branching factor and may therefore be kept as low as required without any effect upon the total number of nodes that are possible.

4.) The total number of point-to-point links in a network that is based upon the physical hierarchical topology will be one less than the total number of nodes in the network.

5.) If the nodes in a network that is based upon the physical hierarchical topology are required to perform any processing upon the data that is transmitted between nodes in the network, the nodes that are at higher levels in the hierarchy will be required to perform more processing operations on behalf of other nodes than the nodes that are lower in the hierarchy. Such a type of network topology is very useful and highly recomended

Signal topology

The mapping of the actual connections between the nodes of a network, as evidenced by the path that the signals take when propagating between the nodes.

Note: The term 'signal topology' is often used synonymously with the term 'logical topology', however, some confusion may result from this practice in certain situations since, by definition, the term 'logical topology' refers to the apparent path that the data takes between nodes in a network while the term 'signal topology' generally refers to the actual path that the signals (e.g., optical, electrical, electromagnetic, etc.) take when propagating between nodes.

Example

Logical topology

The mapping of the apparent connections between the nodes of a network, as evidenced by the path that data appears to take when traveling between the nodes.

Classification of logical topologies

The logical classification of network topologies generally follows the same classifications as those in the physical classifications of network topologies, the path that the data takes between nodes being used to determine the topology as opposed to the actual physical connections being used to determine the topology.

Notes:

1.) Logical topologies are often closely associated with media access control (MAC) methods and protocols.

2.) The logical topologies are generally determined by network protocols as opposed to being determined by the physical layout of cables, wires, and network devices or by the flow of the electrical signals, although in many cases the paths that the electrical signals take between nodes may closely match the logical flow of data, hence the convention of using the terms 'logical topology' and 'signal topology' interchangeably.

3.) Logical topologies are able to be dynamically reconfigured by special types of equipment such as routers and switches.

Daisy chains

Except for star-based networks, the easiest way to add more computers into a network is by daisy-chaining, or connecting each computer in series to the next. If a message is intended for a computer partway down the line, each system bounces it along in sequence until it reaches the destination. A daisy-chained network can take two basic forms: linear and ring.

• A linear topology puts a two-way link between one computer and the next. However, this was expensive in the early days of computing, since each computer (except for the ones at each end) required two receivers and two transmitters.
• By connecting the computers at each end, a ring topology can be formed. An advantage of the ring is that the number of transmitters and receivers can be cut in half, since a message will eventually loop all of the way around. When a node sends a message, the message is processed by each computer in the ring. If a computer is not the destination node, it will pass the message to the next node, until the message arrives at its destination. If the message is not accepted by any node on the network, it will travel around the entire ring and return to the sender. This potentially results in a doubling of travel time for data.