The Broadband Guide
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List of netowrking, wireless, broadband, satellite, telephony, general computing and other technical terms used throughout the site.
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Term Description
SDM SDM (Space Division Multiplexing) is a method by which metallic, radio, or optical transmission media are physically separated by insulation, waveguides, or space in order to maintain channel separations. Within each physically distinct channel, multiple channels can be derived simultaneously through frequency, time, or wavelength division multiplexing. Some Passive Optical Network (PON) implementations employ space division multiplexing, with the downstream transmissions occurring over one fiber of a duplex fiber optic cable and upstream transmission occurring over the other fiber.

Space Division Multiplexing is an integral part of the new 802.11n wireless standard. It allows for different data streams to be transmited over different antennas simultaneously with the goal of increased capacity (throughput) and better SNR performance. These different data streams can then be recombined at the receiver using multiple antennas as well.

In fiber optics, SDM is the condition in which each fiber of a bundle carries a separate channel.
SDSL SDSL (Single line DSL, Symmetric DSL) is a DSL variation that uses just one twisted pair. SDSL is also symmetric, ie, the maximum data rate both upstream and downstream is the same, as opposed to ADSL.
SLA SLA (Service Level agreement) is a document outlining the service that a carrier provides to a customer. SLAs normally include acceptable levels of latency, packet loss, availability, as well as other expectations of the customer and carrier. In the event that the carrier does not meet their SLA (customer experiences carrier-caused outage, for example), the customer may be eligible for billing credit.
SMTP SMTP (Simple Mail Transfer Protocol) is a TCP/IP protocol used in sending and receiving e-mail. It is usually used together with POP3 or IMAP, protocols that let the user save messages in a mailbox and download them periodically from a server. In other words, client programs typically use SMTP for sending e-mail and POP3/IMAP for downloading email messages from their local mail server.
sneakernet sneakernet (jargon, generally ironic, a.k.a. floppy-net, foot-net) - transfer of data by physically carrying floppy disks, hard disks, tape or other removable medium from one place to another.

"Never underestimate the bandwidth of a station wagon filled with magtape, or a 747 filled with CD-ROMs."
SNMP SNMP (Simple Network Management Protocol) is an internet standard protocol defined in RFC 1157, developed to manage nodes on an IP network.

SNMP is used most often by network administrators to monitor and map network availability, performance, and error rates. To work with SNMP, network nodes utilize a distributed database of object definitions called the Management Information Base (MIB). All SNMP compliant devices contain a MIB which supplies the pertitent attributes of a device. Some of the attributes are hard coded in the MIB while others can be dynamic values suplied by software running on the device.
SNR SNR or S/N (Signal-to-Noise Ratio)
In communications, signal-to-noise ratio is a measure of signal strength relative to background noise (measured as signal level divided by noise). The ratio is usually measured in decibels (dB).

Higher SNR numbers repesent cleaner signals, with less noise. Decreasing noise, and/or increasing signal increases/improves the SNR value.
SOHO Small Office/Home Office (SoHo) - a market for relatively inexpensive consumer electronics targeted towards individuals and small companies.
SONET SONET (Synchronous Optical Network) is an optical networking standard, defining specific aspects of how the network will be automatically restored during service outages via redundant links, as well as how it will be synchronized to facilitate time division multiplexing (TDM).
SPI SPI (Stateful Packet Inspection) is a firewall technology that monitors the state of a transaction to verify the destination of an inbound packet matches the source of a previous outbound request.
SSD SSD (Solid State Drive) is a data storage device that uses solid-state memory to store persistent data in the same manner as traditional block i/o mechanical hard disk drives (HDDs).

SSDs retain data in non-volatile memory chips, contain no moving parts, they're faster, less susceptible to physical shock, quieter, with much lower access time and latency, and use less power than traditional traditional HDDs.
SSID SSID (service set identifier) is a 32 byte set of characters that uniquely names a WLAN (Wireless LAN). This name allows stations to connect to the desired network when multiple independent networks operate in the same physical area.

A set of wireless devices communicating directly with each other is called a basic service set (BSS). Several BSSs can be joined together to form an extended service set (ESS), a logical WLAN segment. A Service Set Identifer (SSID) is simply a 32 byte alphanumeric name given to such ESS.
STBC STBC (Space-Time Block Coding) is a technique used in wireless communications to transmit multiple copies of the same data stream across a number of antennas (and frequency channels) to improve the reliability of data transfer.

Wirelessly transmitted signal traverses a potentially difficult environment with scattering, reflections, noise, etc. Data redundancy results in a higher chance of being able to use one of more of the received copies to correctly decode the received signal. Space-Time Block coding combines all the copies of the received signal to extract as much information as possible.

TCP interprets frame/packet loss as sign of network congestion and cuts the transmission rate to half whenever thoese error events occur. STBC essentially presents a smoother transmission to TCP, allowing for a more reliable wireless communication with a minimal throughput impact.
SWAG Scientific Wild ass Guess :D
sysadmin SysAdmin (systems administrator). Knows the answer to life, the universe and everything.

...and how to fix a server.

On a more serious note, a SysAdmin is a person whose responsibility is the integrity and security of a network. The job often includes maintaining networked computers and peripherals as well.
TC-PAM TC-PAM (Trellis Coded Pulse Amplitude Modulation) is the modulation format that is used in both HDSL2 and SHDSL, and provides robust performance over a variety of loop conditions.

SHDSL uses TC-PAM to provide a rate/reach adaptive capability, offering enhanced performance (increased rate or reach) and improved spectral compatibility with ADSL when compared to today's 2B1Q SDSL offerings. Compared to HDSL2, SHDSL offers lower power consumption through the use of lower-power, intelligently shaped transmit waveforms.
TCP/IP TCP/IP (Transmission Control Protocol/Internet Protocol) is the suite of communications protocols (the main ones being TCP and IP) used to connect hosts on the Internet.

TCP/IP is used by the Internet, making it the de facto most widely spread standard for transmitting data over networks. TCP and IP were developed by a DOD (Department of Defense) research project to connect a number different networks designed by different vendors into a network of networks (the Internet).
Tcp1323Opts Tcp1323Opts - TCP Large Window support ( Windows 98 and later ). Used when an application requests a Winsock socket to use buffer sizes greater than 64KB. In previous implementations the TCP window size was limited to 64KB, this limit is raised to 2**30 through the use of TCP large window support as defined in [RFC1323] and implemented in Winsock 2. Tcp1323Opts also controls Timestamps.
TDM TDM (Time Division Multiplexing) is a type of multiplexing that combines data streams by assigning each stream a different time slot in a set. TDM repeatedly transmits a fixed sequence of time slots over a single transmission channel.

See also: WDM, FDM.
TDMA TDMA (Time Division Multiple Access) is a wireless technology using TDM (time-division multiplexing). TDMA is used by the GSM digital cellular system. It works by dividing a frequency into multiple time slots, and then allocating them to multiple calls. This way, a single frequency can support multiple data channels simultaneously.
TELCO Telephone Company
tethering tethering refers to using an internet-capable mobile phone as a modem to share its internet access with other devices, such as laptops and PCs. This internet sharing can be accomplished over Wi-Fi, Bluetooth, or by physical connection using a cable.

In the case of tethering over Wi-Fi, the mobile phone acts as a portable router and the feature is aslo called a mobile hotspot.

Many modern mobile phones, including Windows Phone 7 (from version 7.5 Mango), Android (from version 2.2 Froyo), and iOS (4.3 or higher) offer tethered Intnernet access. The feature is sometimes disabled, or requires extra monthly fees by operators to reduce strain on their networks.
TFTP TFTP (Trivial File Transfer Protocol) is a simplified version of FTP that uses UDP, rather than TCP for data transport. It is easier to implement than FTP, but it is insecure (no authentication), lacks directory services, and UDP is not a reliable transport protocol.

TFTP is intended for use with small file transfers, often used to allow diskless devices to boot over the network, or for firmware transfers.
throughput Throughput (or transfer rate) in data transmission is the amount of data moved successfully from one place to another in a given time period.

For data networks, throughput is usually measured in number of bits per second (bps) that are transmitted, also quoted as Kilobits per second (Kbps) or Megabits per second (Mbps).
Timestamps Timestamps is defined in TCP Options ( RFC 1323 ) and used for two distinct mechanisms: RTTM (Round Trip Time Measurement) and PAWS (Protection Against Wrapped Sequences).

The disadvantage of using Timestamps is it adds 12 bytes to the 20 byte TCP header.

TKIP TKIP (Temporal Key Integrity Protocol) is an enhancement to WEP security, part of a draft standard 802.11i.

TKIP enhances WEP security by adding functions for remixing keys per packet, making it more resistant to attacks involving key reuse (the main WEP weakness).

TKIP utilizes RC4 stream cipher with 128-bit keys for encryption and 64-bit keys for authentication.
topology The shape of a local-area network (LAN) or other communications system (either physical or logical).

The principal network topologies are listed below:

bus topology: (a.k.a. linear topology) All devices are connected to a central cable, called the bus or backbone. Bus networks are relatively inexpensive and easy to install for small networks.
star topology: All devices are connected to a central hub(switch). Star networks are relatively easy to install and manage, but bottlenecks can occur because all data must pass through the hub.
ring topology: All devices are connected to one another in the shape of a closed loop, so that each node is connected directly to two other devices, one on either side of it. Ring topologies are relatively expensive and difficult to install, but they offer high bandwidth and can span large distances.
mesh topology: A network topology in which there are at least two nodes with multiple paths between them.
hybrid topology: A combination of any two or more network topologies. For example, a bus-star hybrid network consists of a high-bandwidth bus (the backbone), which connects a collections of slower-bandwidth star segments.
tree topology: a hybrid topology that combines characteristics of linear bus and star topologies. It consists of groups of star-configured nodes connected to a linear bus backbone cable.
TR-069 TR-069 (Technical Report 069) is a Broadband Forum technical specification entitled "CPE WAN Management Protocol" (CWMP). It defines an application layer protocol for remote management of end-user devices (e.g. modems, routers, gateways, set-top boxes, VoIP phones).

TR-069 provides the communication between customer-premises equipment (CPE) and Auto Configuration Servers (ACS). It includes auto configuration, dynamic service activation, firmware updates/version management, status and performance control, diagnostics, logs, etc. It is a platform that works through the Internet, and regardless of the device(s) manufacturer.
traceroute traceroute is a utility that records the route between your computer and a destination computer on the Internet. It measures the time it takes to reach each node (specific gateway computer at each hop) needed to make the connection.

Traceroute is a handy tool both for understanding where problems are in the network (packet loss, high latency) and for getting a detailed sense of the network itself. The traceroute utility sends 3 ICMP packets to each node, increasing the "time to live" value of packets and seeing how far they get until they reach the given destination; thus, a trail of hosts passed through and time to them is built up.

The traceroute utility comes included with most current operating systems as part of the TCP/IP package. In Windows, traceroute can be used from the Command Prompt, by typing:

transponder transponder is the portion of a communications satellite that acts as a receiver, amplifier, and retransmitter for the signals communicated up to and down from the satellite.
trojan trojan (a.k.a trojan horse) - a program that pretends to be something else. Usually a piece of malicious code contained in another seemingly harmless program in such a way that it can get control and/or damage your PC. It could erase some files (even your entire hard disk) and/or give other people full access to your system... Sounds ridiculous? It happens every single day to computer users near you.

According to legend (Homer's Iliad), the Greeks won the Trojan war by hiding warriors in a huge, hollow wooden horse, who later opened the gates and helped them get into the fortified city of Troy. This a symbolic explanation of what a computer trojan horse is: it can open your PC to anyone, even if no immediate damage is done.

Note: In a much more limited use the term was also used for counter-measures, such as a program for cleaning a virus.
TTL TTL (Time To Live) is a value set in the header of outgoing IP packets. TTL determines the maximum amount of time (in seconds) an IP packet can live, or the number of routers an IP packet may pass through before being discarded (whichever is lower).
tunneling Tunneling refers to the ability to encapsulate packets of data formatted for one network protocol (or a private secure network) in packets used by another protocol (or a public network). Tunneling allows the use of the (public) Internet to transfer data on behalf of a private network. See also: VPN, PPTP.

Note that tunneling and VPN is not intended as a substitute for data encryption by itself. For a higher security level strong encryption should be used within the VPN.
TurboQAM TurboQAM is a Broadcom 802.11 wireless technology that makes it possible for the 2.4GHz band with 40MHz channels to achieve a maximum transfer rate of 200 Mbps per data stream, instead of the standard 150 Mbps. This is achieved by using QAM-256, instead of the standard QAM-64 used until now by 802.11n wireless networks.

TurboQAM requires 40MHz channels and clients that support QAM-256. Current routers revert back to 20MHz channels when there is interference from another radio that is within two channels of them.
twisted pair Two single core copper wires twisted around ach other to reduce crosstalk or electromagnetic induction. Twisted pair is usually installed in two or more pairs, all within a single cable. For some locations, twisted pair is enclosed in a shield that functions as a ground, and is known as shielded twisted pair (STP). Ordinary wire to the home is unshielded twisted pair (UTP).
UAC UAC (User Account Control) is a Windows Vista/2008 feature intended to provide aditional security by reducing user access.

It is intended to prevent access to core Windows components, prompting the user for access to perform any administrative tasks.

As a result from UAC, local administrative accounts run as standard user accounts by default, with their administrative priviledges disabled until they attempt to run an application or task that requires administrative token. When attempting to start such applications, the user is prompted to consent to running the application with elevated priviledges.

Applications can be configured to always run as elevated, or UAC can be reconfigured from from Control Panel > User Accounts > Turn User Account Control On or Off.

See Also: How to change Vista UAC settings
UAC UAC (User Account Control) is a Windows Vista/2008 feature intended to provide aditional security by reducing user access.

It is intended to prevent access to core Windows components, prompting the user for access to perform any administrative tasks.

As a result from UAC, local administrative accounts run as standard user accounts by default, with their administrative priviledges disabled until they attempt to run an application or task that requires administrative token. When attempting to start such applications, the user is prompted to consent to running the application with elevated priviledges.

Applications can be configured to always run as elevated, or UAC can be reconfigured from from Control Panel > User Accounts > Turn User Account Control On or Off.
UDP UDP (User Datagram Protocol, RFC 768) is a communications protocol, an alternative to TCP (Transmission Control Protocol), and uses the Internet Protocol (IP) to actually get a data units (datagrams) from one network node to another.

UDP does not provide the service of dividing a message into packets (unlike TCP) and reassembling it at the other end. Specifically, UDP doesn't provide sequencing of the packets that the data arrives in.

UDP is a stateless protocol, meaning it doesn't acknowledge that packets being sent have been received. For this reason, the UDP protocol is typically used for streaming media, where a lost packet should not stop the transmission of data, or for simple applications where very little processing power is a requirement. TFTP (Trivial File Transfer Protocol) uses UDP as well.
UMTS UMTS (Universal Mobile Telecommunications System) is a third-generation (3G) broadband, packet-based data transmission technology with data rates up to 2 Mbps. UMTS is based on the GSM communication standard.
uncap Uncapping refers to the concept of somehow lifting the bandwidth cap many cable modem service providers (MSO's) impose. Some users want to do this in order to improve the speed of their cable modem, obviously circumventing the service provider and may be considered theft of service.

Some early pre-DOCSIS cable modems could be hacked to remove upstream limitations, however, those days are long gone.

Note that speed tweaks (changing TCP Receive Window, etc.) to improve speed are not considered "uncapping" and are absolutely legal way of fixing/tuning your OS to improve network performance.
Term Description
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