T-Flash card

A T-Flash card -also known as a TransFlash or MicroSD card- is a removable flash memory card (15 x 11 x 0.77 mm in size) commonly used in mobile devices such as cellphones for storing data.

T.38 Fax Relay

T.38 is an ITU-T standard that VoIP devices use to send fax messages over the Internet.

T1

A T1 line consists of 24 voice channels packed into a 193 bit frame and transmitted at 1.544 Mbps. The unframed version, or payload, is 192 bits at a rate of 1.536 Mbps.

TACACS

The Terminal Access Controller Access-Control System (TACACS) protocol authenticates network users by means of an external authentication server. It is similar to RADIUS. TACACS usually uses TCP or UDP port 49.

TACACS+

The Terminal Access Controller Access-Control System Plus (TACACS+) protocol provides authentication, authorization and accounting for a network by means of an external authentication server. TACACS+ uses TCP, usually on port 49. Although TACACS+ is based on TACACS, it is not compatible with TACACS.

Tagged VLAN

A tagged VLAN uses a VLAN ID to identify VLAN group membership. The VLAN ID associates traffic with a specific VLAN group and provides the information needed to process the traffic across a network.

Tag Protocol Identifier (TPID)

The Tag Protocol Identifier (TPID) is a standard Ethernet-type code identifying the frame and indicates whether the frame carries IEEE 802.1Q tag information. The value of this field is 0x8100 as defined in IEEE 802.1Q.

TAT

In ATM, the Theoretical Arrival Time is the time when the next cell is expected to arrive. TAT is calculated based on the PCR or SCR. See PCR and SCR.

TCP (Transmission Control Protocol)

TCP is a connection-oriented transport service that ensures the reliability of message delivery. It verifies that messages and data were received. A network protocol for transmitting data that requires acknowledgement from the recipient of data sent.

TCP/IP
Transmission Control Protocol over Internet Protocol. The TCP/IP protocol defines how data can be transmitted in a secure manner between networks. TCP/IP is the most widely used communications standard and is the basis for the Internet.

TCP/IP Filter Rules

TCP/IP filter rules allow you to base the rule on the fields in the IP and the upper layer protocol, for example, UDP and TCP headers.

Teaming Mode

The teaming mode sets how a device’s multiple Ethernet interfaces behave. They can act independently, one can back up another, they can share the traffic load, or they can be grouped into a logical link.

TEK

Data encryption key used in PKM-EAP data transfer.

Telnet

Telnet is the login and terminal emulation protocol common on the Internet and in UNIX environments. It operates over TCP/IP networks. Its primary function is to allow users to log into remote host systems.

TEMPEST

Electromagnetic signals radiate from electronic equipment and cables. Extra shielding is used on cables and equipment to meet TEMPEST requirements, in order to stop these signals from going out to unauthorized listeners.

Terminal

A device that allows you to send commands to a computer somewhere else. At a minimum, this usually means a keyboard, display screen and some simple circuitry.

Terminal Software

Software that pretends to be (emulates) a physical terminal and allows you to type commands to a computer somewhere else.

Test In

On a VoIP line card that supports the connection of external testing devices, the TEST IN port is used for testing internal POTS circuits.

Test Out

On a VoIP line card that supports the connection of external testing devices, the TEST OUT port is used for testing the external wire loop to the customers phone.

TFTP (Trivial File Transfer Protocol)

TFTP is an Internet file transfer protocol similar to FTP (File Transfer Protocol), but it is scaled back in functionality so that it requires fewer resources to run. TFTP uses the UDP (User Datagram Protocol) rather than TCP (Transmission Control Protocol).

Thin server
A network-based device that is designed to perform a specialized set of server functions, such as a print server or NAS (Network Attached Storage). A thin server offloads general-purpose application servers and makes using the network more efficient by providing functionality that is easier to install and more reliable than a conventional server.

Throughput

The amount of data moved successfully from one node to another in a given time period.

Time (RFC 868)

A network protocol for retrieving the current time from a server. The computer issuing the command compares the time on its clock to the information returned by the server, adjusts itself automatically for time zone differences, then calculates the difference and corrects itself if there has been any temporal drift.

TKIP

Temporal Key Integrity Protocol (TKIP) is an encryption protocol that uses 128-bit keys that are dynamically generated and distributed by the authentication server. TKIP regularly changes and rotates the encryption keys so that the same encryption key is never used twice.

TLS

Transport Layer Security (TLS) is a protocol that enables secure transactions of data by ensuring confidentiality (an unauthorized party cannot read the transferred data), authentication (one party can identify the other party) and data integrity (you know if data has been changed). TLS is the application protocol-independent successor to the Secure Socket Layer (SSL) protocol. Is a protocol that guarantees privacy and data integrity between client/server applications communicating over the Internet.

TLS (VLAN)

Transparent LAN Service (TLS) allows a service provider to distinguish multiple customer VLANs within its network, even those with the same (customer-assigned) VLAN ID. This is also known as VLAN stacking or Q-in-Q.

TMSS

TMSS (Trend Micro Security Services) identifies vulnerabilities and protects computers and networks that have Internet connections through a broadband router.

Token Bucket

The token bucket algorithm is used to prevent network congestion. It uses tokens in a bucket to control when traffic can be transmitted. The bucket is a buffer that temporarily stores outgoing packets and transmits them at an average rate.

Topology

The physical layout of a network.

TPC

TPC (Transmit Power Control) helps reduce a wireless device’s transmission power to avoid interference with satellites. See also IEEE 802.11h.

Traceroute

Traceroute is a utility used to determine the path a packet takes between two endpoints.

Traffic Encryption Key

A traffic encryption key (TEK) is any cryptographic key used specifically to encrypt the data flow (and not for authentication or other purposes). In a WiMAX security association, the base station generates the TEK, encrypts it using the authentication key, and transmits it to the mobile station. The mobile station decrypts the TEK, also using the authentication key. Both stations can then exchange data traffic.

Traffic Flow Anomaly

Traffic flow anomaly is an intrusion detection method where certain applications, for example, peer-to-peer applications, can be defined as “abnormal” and therefore an “intrusion”. See also Anomaly Analysis, Heuristic Analysis, Protocol Decode and Protocol Anomaly Detection.

Traffic Policing

Traffic policing identifies whether a traffic flow conforms to a Service Level Agreement (SLA) between a provider and subscriber of network services. If a traffic flow exceeds the SLA, then the network services provider can limit the use of its services to the subscriber. See TRTCM.

Traffic Shaping

Traffic shaping is an ATM networks built-in traffic management. It is an agreement between the carrier and the subscriber to regulate the average rate and fluctuations of data transmission over an ATM network. Traffic shaping helps fine-tune the levels of services based on the priority of the traffic flow.

Traffic Redirect

Traffic Redirect forwards WAN traffic to a backup gateway on the LAN when the router cannot connect to the Internet, thus acting as an auxiliary backup.

Transport

IPSec uses transport mode to protect upper layer protocols and affects only the data in the IP packet. The IP packet contains the security protocol (AH or ESP) located after the original IP header and options, but before any upper layer protocols contained in the packet (such as TCP and UDP).

Transparent Firewall

A transparent firewall, also known as a bridge firewall, is a device that can act as a bridge and also filter/inspect packets. You do not have to change other network settings when you add a transparent firewall to the network.

Transmission Rate

This is a measurement of the speed of a network connection.

Transceiver

A transceiver is a single unit that houses a transmitter and a receiver.

Trap

In the Simple Network Management Protocol (SNMP), a TRAP message is sent by an SNMP agent to an SNMP manager. The trap is an alert triggered by specific event changes on the agent’s host device. Unlike other messages sent by SNMP agents it is not sent in response to an SNMP manager’s request, but is sent autonomously. In later versions of SNMP, traps are known as notifications.

Trellis Encoding

Trellis encoding helps to reduce the noise in ADSL transmissions. Trellis may reduce throughput but it makes the connection more stable.

Trigger Port Forwarding

Trigger Port Forwarding allows computers on your LAN to dynamically take turns communicating with servers on the WAN that do not accept NAT port translation.

Triple DES

This is a stronger variant of DES (Data Encryption Standard). Triple DES is a widely-used method of data encryption that applies three separate private (secret) 56-bit keys to each 64-bit block of data.

Triple Churning Algorithm

A triple churning algorithm is a data encryption-decryption method in an EPON system, which is based on single churning and standardized by the China Ministry of Information Industry. Triple churning uses three churning operations to provide stronger encryptions.

TRTCM

Two Rate Three Color Marker (TRTCM) as defined in RFC 2698, is a type of traffic policing that measures IP packet streams against two user defined criteria: Peak Information Rate (PIR) and Committed Information Rate (CIR). TRTCM marks IP packets with DiffServ Code Point values. RFC 2698 refers to the different DiffServ Code Point values as the colors red, yellow and green. Red indicates the packets have the highest chance of being dropped, yellow indicates a medium chance of being dropped and green indicates a low chance of being dropped. TRTCM marks the IP packets that exceed the PIR red, the packets that exceed the CIR yellow, and the packets that do not exceed the CIR are marked green. See DiffServ, CIR, PIR, Traffic Policing, DSCP.

Trunking

Trunking (link aggregation) is the grouping of physical ports into one logical higher-capacity link. You may want to trunk ports of for example, if it is cheaper to use multiple lower-speed links than to under-utilize a higher-speed, but more costly, port link. However, the more ports you aggregate to get higher bandwidth then the fewer available ports you have.

Trusted Ports

In IP source guard, there are two sets of trusted ports, one for DHCP snooping and one for ARP inspection. For DHCP snooping, trusted ports are connected to DHCP servers or other switches, so the system learns dynamic bindings from trusted ports. For ARP inspection, ARP packets are never discarded on trusted ports.

Tunnel

IPSec uses tunnel mode to encapsulate the entire IP packet and transmit it securely. Tunnel mode is fundamentally an IP tunnel with authentication and encryption and is required for gateway services to provide access to internal systems.

Tunnel Port

In VLAN Stacking, this is an egress port on a service provider’s edge devices. It replaces all VLAN tags belonging to a customer with a single service provider’s VLAN.

Tunnel TPID

Tunnel TPID is the VLAN stacking tag type that is added to outgoing frames sent through a Tunnel Port of the service provider’s edge devices.

Twisted Pair

Two insulated wires, usually copper, twisted together and often bound into a common sheath to form multi-pair cables. In ISDN, the cables are the basic path between a subscriber’s terminal or telephone and the PBX or the central office.

Tx Gain

On a VoIP line card, Tx gain increases or decreases the volume of the audio signal the subscriber sends to the SIP server.

TX Rate

This is used in measurements and statistics about what is transmitted by a device. Transmission Rate.

Type Of Service

Type of Service (ToS) is a field description in the Internet Protocol (IP) header that indicates the desired quality of the route over which data packets are transmitted.