Network Glossary F

Fast Secure Roaming Enables a wireless client to securely roam between access points in the same subnet or between subnets with access point handoff times within 50 ms.

fast switching An optimized Layer 3 forwarding path through a router. Fast switching optimizes routing table lookup by creating a special, easily searched table of known flows between hosts.

FD See feasible distance.
feasibility condition With EIGRP, for a particular route, the case in which the RD is lower than the FD.

Feasible distance With EIGRP, the metric value for the lowest-metric route to a particular subnet.

feasible successor With EIGRP, a route that is not a successor route, but that meets the feasibility condition; can be used when the successor route fails, without causing loops.

FEC See Forwarding Equivalence Class.

FECN See Forward Explicit Congestion Notification.

FHSS See frequency hopping spread spectrum.

FIB See Forwarding Information Base.

finish time A term used with WFQ for the number assigned to a packet as it is enqueued into a WFQ queue. WFQ schedules the currently lowest FT packet next.

flash updates See triggered updates.

Flush timer With RIP, a per-route timer, which is reset and grows with the Invalid timer. When the Flush timer mark is reached (default 240 seconds), the router removes the route from the routing table, and now accepts any other routes about the failed subnet.

ForeSight A Cisco-proprietary messaging protocol implemented in WAN switches that can be used to signal network status, including congestion, independent of end-user frames and cells.

Forward Delay timer An STP timer that dictates how long a port should stay in the listening state and the learning state.

Forward Explicit Congestion Notification A bit in the LAPF Frame Relay header that, when set to 1, implies that the frame has experienced congestion.

Forwarding Equivalence Class A set of packets in an MPLS network for which the MPLS network will apply the exact same forwarding behavior.

Forwarding Information Base A neighbor state that signifies the other router has reached neighbor status, having passed the parameter check.

forwarding state An 802.1d STP port state in which the port sends and receives frames.

fraggle attack An attack similar to a smurf attack, but using packets for the UDP Echo application instead of ICMP.

fragmentation In wireless LANs, a mechanism that counters issues related to RF interference by dividing a larger 802.11 data frame into smaller frames that are sent independently to the destination. See also LFI.

Frame Relay Forum A vendor consortium that formerly worked to further Frame Relay common vendor standards.

framing From a Layer 1 perspective, the process of using special strings of electrical signals over a transmission medium to inform the receiver as to which bits are overhead bits, and which fit into individual subchannels.

frequency hopping spread spectrum A type of spread spectrum that spreads RF signals over the frequency spectrum by transmitting the signal at different frequencies according to a hopping pattern. One of the original 802.11 physical layers used FHSS to offer data rates of 1 and 2 Mbps.

FRF See Frame Relay Forum.

FRF.5 An FRF standard for Frame Relay-to-ATM Service Interworking in which both DTEs use Frame Relay, with ATM in between.

FRF.8 An FRF standard for Frame Relay-to-ATM Service Interworking in which one DTE uses Frame Relay and one uses ATM.

FRF.9 An FRF standard for payload compression.

FRF.11-c An FRF standard for LFI for VoFR (FRF.11) VCs, in which all voice frames are interleaved in front of data frames’ fragments.

FRF.12 An FRF standard for LFI for data (FRF.3) VCs.

FT See finish time.

full drop A WRED process by which WRED discards all newly arriving packets intended for a queue, based on whether the queue’s maximum threshold has been exceeded.

full duplex Ethernet feature in which a NIC or Ethernet port can both transmit and receive at the same instant in time. It can be used only when there is no possibility of collisions. Loopback circuitry on NIC cards is disabled to use full duplex.

full SPF calculation An SPF calculation as a result of changes inside the same area as a router, for which the SPF run must examine the full LSDB.

full update A routing protocol feature by which the routing update includes the entire set of routes, even if some or all of the routes are unchanged.

fully adjacent (OSPF) Any OSPF neighbor for which the database flooding process has completed.