T1 A name acclimated for DS1 curve central the North American TDM hierarchy.
T3 A name acclimated for DS3 curve central the North American TDM hierarchy.
TACACS+ A Cisco-proprietary agreement that defines how to accomplish affidavit amid an
authenticator (for example, a router) and an affidavit server that holds a account of usernames
and passwords.
Tag Administration Agreement The aboriginal MPLS agreement acclimated to acquaint the binding
(mapping) advice about anniversary accurate IP prefix and associated label. It is hardly different
from LDP, but functionally equivalent. See additionally LDP.
tail bead An accident in which a new packet arrives, defective to be placed into a queue, and the
queue is full—so the packet is discarded.
Tc See Time Interval.
TDP See Tag Administration Protocol.
Time Breach (Tc) Variable name for the time breach acclimated by shapers and by CAR.
900 TCP cipher bits
TCP cipher $.25 Single-bit fields in the TCP header. For example, the TCP SYN and ACK code
bits are acclimated during affiliation establishment.
TCP flags The aforementioned affair as TCP cipher bits. See TCP cipher bits.
TCP advance compression The action of demography the IP and TCP headers of a packet, compressing
them, and again uncompressing them on the accepting router.
TCP ambush A Cisco router affection in which the router works to anticipate SYN attacks either
by ecology TCP admission abounding through the router, or by actively absolute TCP
connection until the TCP affiliation is accustomed and again knitting the client-side connection
with a server-side TCP connection.
TCP SYN flood An advance by which the antagonist initiates abounding TCP admission to a server, but
does not complete the TCP connections, by artlessly not sending the third articulation commonly used
to authorize the connection. The server may absorb assets and adios new affiliation attempts
as a result.
TDM See time-division multiplexing.
TDM bureaucracy The anatomy central telcos’ aboriginal agenda ambit build-out in the mid-1900s,
based aloft application TDM to amalgamate and banish abate DS levels into beyond levels, and
vice versa.
Temporal Key Integrity Agreement An added adaptation of WEP that is allotment of the 802.11i
standard and has an automated key-update apparatus that makes it abundant added defended than WEP.
TKIP is not as able as AES in agreement of abstracts protection.
terminal history The affection in a Cisco IOS accessory by which a terminal session’s previously
typed commands are remembered, acceptance the user to anamnesis the old commands to the command
line through a simple key arrangement (for example, the up-arrow key).
time-division multiplexing The action of accumulation assorted synchronized ascribe signals over
a distinct average by giving anniversary arresting its own time slot, and again breaking out those signals.
Time to Live A acreage in the IP advance that is decremented at anniversary canyon through a Band 3
forwarding device.
TKIP See Temporal Key Integrity Protocol.
token brazier A conceptual archetypal acclimated by shapers and policers to represent their centralized logic.
ToS byte 901
ToS byte See Blazon of Account byte.
totally NSSA breadth A blazon of OSPF NSSA breadth for which neither alien (type 5) LSAs are
introduced, nor blazon 3 arbitrary LSAs; instead, the ABRs arise and inject absence routes into
the area. Alien routes can be injected into a absolutely NSSA area.
totally chubby breadth A blazon of OSPF butt breadth for which neither alien (type 5) LSAs are
introduced, nor blazon 3 arbitrary LSAs; instead, the ABRs arise and inject absence routes into
the area. Alien routes cannot be injected into a absolutely chubby area.
traffic arrangement In abstraction and policing, the analogue of ambit that calm betoken the
allowed amount and bursts.
transient multicast accumulation Multicast addresses that are not assigned by IANA.
transit arrangement (OSPF) A network/subnet over which two or added OSPF routers accept become
neighbors, thereby actuality able to advanced packets from one router to addition beyond that network.
transit router (OSPF) A router that is accustomed to accept a packet from an OSPF router and
then advanced the packet to addition OSPF router.
transmit ability The arresting courage of the RF arresting at the achievement of the radio agenda or access
point transmitter, afore actuality fed into the antenna. Measured in milliwatts, watts, or dBm.
Trap In the ambience of SNMP, the Trap command is beatific by an SNMP agent, to a manager, when
the abettor wants to accelerate unsolicited advice to the manager. Trap is not followed by a Response
message from the accepting SNMP manager.
Triggered Extensions to RIP for On-Demand Circuits Authentic in RFC 2091, the extensions
define how RIP may accelerate a abounding amend once, and again accelerate updates alone back routes change,
when an amend is requested, or back a RIP interface changes accompaniment from bottomward to up.
triggered updates A acquisition agreement affection for which the acquisition agreement sends routing
updates anon aloft audition about a afflicted route, alike admitting it may commonly alone send
updates on a approved amend interval.
trunking Additionally alleged VLAN trunking, a adjustment (using either the Cisco ISL agreement or the
IEEE 802.1Q protocol) to abutment accustomed cartage amid switches for assorted VLANs that have
members on added than one switch.
TTL See Time to Live.
TTL scoping Controls the administration of multicast cartage by blockage the TTL values
configured on the interfaces. It assiduously the multicast packet alone on those interfaces whose
configured TTL amount is beneath than or according to the TTL amount of the multicast packet.
Type of Account byte A 1-byte acreage in the IP header, originally authentic by RFC 791 for QoS
marking purposes.
U/L bit The additional best cogent bit in the best cogent byte of an Ethernet MAC address,
a amount of bifold 0 implies that the abode is a Universally Administered Abode (UAA) (also
known as Burned-In Abode [BIA]), and a amount of bifold 1 implies that the MAC abode is a
locally configured address.
UDLD See UniDirectional Articulation Detection.
unicast MAC abode Ethernet MAC abode that represents a distinct NIC or interface.
UniDirectional Articulation Apprehension A aegis adjoin problems acquired by unidirectional links
between two switches. Uses messaging amid switches to ascertain the loop, err-disabling the port
when the articulation is unidirectional.
Update (EIGRP) An EIGRP bulletin that informs neighbors about acquisition information.
Update letters crave an Ack.
Update timer With RIP, the approved breach at which updates are sent. Anniversary interface uses an
independent timer, behind to 30 seconds.
UplinkFast Cisco-proprietary STP affection in which an admission band about-face is configured to be
unlikely to become Root or to become a alteration switch. Also, aggregation aloft the accident of the
switch’s Root Port takes abode in a few seconds.
upstream router From one multicast router’s perspective, the upstream router is addition router
that has aloof forwarded a multicast packet to that router.
User Priority A 3-bit acreage in an 802.1Q advance acclimated for appearance frames.
variance An accumulation ambience for EIGRP and IGRP. Any FS avenue whose metric is beneath than this
variance multiplier times the successor’s metric is added to the acquisition table, aural the
restrictions of the maximum-paths command.
variable-length subnet appearance A action for subnetting a classful arrangement for which masks/
prefixes are altered for some subnets of that one classful network.
VC 903
VC See basic circuit.
violate A class acclimated by a policer to allocate packets about to the cartage contract. These
packets are advised to be aloft the cartage arrangement in all cases.
virtual ambit A analytic abstraction that represents the aisle over which frames biking between
DTEs. VCs are decidedly advantageous back comparing Frame Relay to busy concrete circuits.
virtual IP abode The IP abode acclimated by hosts as the absence aperture in a VRRP
configuration. This abode is aggregate by two or added VRRP routers, abundant as HSRP works.
virtual LAN A accumulation of accessories on one or added LANs that are configured (using
management software) so that they can acquaint as if they were absorbed to the aforementioned wire,
when, in fact, they are amid on a cardinal of altered LAN segments. Because VLANs are based
on analytic instead of concrete connections, they are acutely flexible.
virtual articulation With OSPF, the encapsulation of OSPF letters central IP, to a router with which
no accepted subnet is shared, for the purpose of either acclimation abstracted areas or accouterment a
connection from some alien breadth to the courage area.
Virtual Router Back-up Agreement A accepted (RFC 3768) affection by which multiple
routers can board interface IP abode back-up so that hosts application the shared, basic IP
address as their absence aperture can still ability the blow of a arrangement alike if one or added routers fail.
Virtual Acquisition and Forwarding table In MPLS VPNs, an article in a distinct router that
provides a agency to abstracted routes in altered VPNs. The VRF includes per-VRF instances of
routing protocols, a acquisition table, and an associated CEF FIB.
VLAN See basic LAN.
VLAN Trunking Agreement A Cisco-proprietary protocol, acclimated by LAN switches to
communicate VLAN configuration.
VLSM See variable-length subnet masking.
VoFR See Articulation over Frame Relay.
Voice over Frame Relay Authentic in FRF.11, an FR VC that uses a hardly assorted header, as
compared with FRF.3 abstracts VCs, to board articulation payloads anon encapsulated central the
Frame Relay LAPF header.
904 VPN label
VPN assuming The centermost MPLS advance in an packet traversing an MPLS VPN, with the label
value anecdotic the forwarding capacity for the departure PE’s VRF associated with that VPN.
VRF table See Basic Acquisition and Forwarding table.
VRRP See Basic Router Back-up Protocol.
VRRP Master router The router in a VRRP accumulation that is currently actively forwarding IP
packets. Conceptually the aforementioned as an HSRP Active router.
VTP See VLAN Trunking Protocol.
VTP pruning VTP action that prevents the breeze of broadcasts and alien unicast Ethernet
frames in a VLAN from actuality beatific to switches that accept no ports in that VLAN.
WCCP See Web Accumulation Communication Protocol.
WCCP array A analytic accumulation of agreeable engines active WCCP amid them. The lead
content agent determines the cartage administration aural the cluster, for optimum achievement and
scalability.
Web Accumulation Communication Agreement The agreement acclimated by agreeable engines to administer traffic
flow amid routers configured for WCCP and amid agreeable engines. WCCP takes advantage
of the actuality that abounding web pages (and added content) are consistently accessed by users in a given
network. Therefore, routers can alter agreeable requests to a accumulation agent or a array of cache
engines to advance acknowledgment time and abate WAN acceptance for buried agreeable afore new requests
are fabricated beyond the WAN.
weight A bounded Cisco-proprietary BGP ambience that is not advertised to any peers. A beyond value
is advised to be better.
weighted fair queuing A Cisco IOS queuing apparatus best notable for its automated classification
of packets into abstracted per-flow queues.
weighted accidental aboriginal apprehension WRED is a adjustment of bottleneck abstention that works by
dropping packets afore the achievement chain becomes absolutely full. WRED can abject its dropping
behavior on IP Precedence or DSCP ethics to bead low-priority packets afore high-priority
packets.
weighted round-robin A queuing scheduler concept, abundant like CQ’s scheduler, in which
queues are accustomed some account in sequence. This appellation is generally acclimated with queuing in Cisco LAN
switches.
weighted appendage bead 905
weighted appendage bead A adjustment that creates three thresholds per departure chain in the Cisco 3560
switch. Cartage is disconnected into the three queues based on CoS value, and accustomed altered likelihoods
(weight) for appendage bead back bottleneck occurs based on which departure chain is involved.
well-known arbitrary A assuming of a BGP aisle aspect in which all BGP
implementations charge abutment and accept the aspect (well known), but BGP Updates can
either accommodate the aspect or not depending on whether a accompanying affection has been configured
(discretionary).
well-known binding A assuming of a BGP aisle aspect in which all BGP
implementations charge abutment and accept the aspect (well known), and all BGP Updates
must accommodate the aspect (mandatory).
WEP See Wired Agnate Privacy.
WFQ See abounding fair queuing.
Wi-Fi Protected Admission A aegis accepted that includes both TKIP and AES and was ratified
by the Wi-Fi Alliance.
window Typically acclimated by protocols that accomplish breeze ascendancy (like TCP), a TCP window is the
number of bytes that a sender can accelerate afore it charge abeyance and delay for an accepting of
some of the yet-unacknowledged data.
Wired Agnate Privacy The antecedent 802.11 accepted key encryption mechanism; vulnerable
to hackers.
wireless LAN ambassador Controls admission to the Internet in accessible wireless LANs.
Wireless LAN Threat Defense Solution An advance apprehension arrangement that safeguards the
wireless LAN from awful and crooked access.
WLSE See Cisco Wireless LAN Solution Engine.
WPA Wi-Fi Protected Access. A aegis accepted that includes both TKIP and AES and was
ratified by the Wi-Fi Alliance.
WRED See abounding accidental aboriginal detection.
WRR See abounding round-robin.
WTD See abounding appendage drop.
Yellow Anxiety A T1 anxiety accompaniment that occurs back a accessory receives a Yellow Anxiety signal. This
typically agency that the accessory on the added end of the band is in a Red Anxiety state.