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    There are 34 entries in the glossary.
    Pages: 1 2


    A common and cost-effective data radio technology is 802.11.  802.11b specifies radio transceivers that operate at up to 11Mbps.  802.11g operates at up to 54Mbps.  Both B and G standards have several fall-back speeds and attempt to initiate or maintain the highest bit rate conditions allow.  There is significant overhead in the wireless protocol.  Real-world best-case data transfer performance is approx. 5Mbps for B and 20Mbps for G.  Distance, radio interference, objects between radio endpoints, and the number of radios participating in a cell are all factors affecting actual performance.


    Access Point, typically in the context of 802.11 networks.  Access Points provide the required management protocol infrastructure to allow multiple clients to roam across multiple APs connected to the same underlying network.


    Bits per second.  Most network communications gear report its throughput in bps, Kbps, Mbps, or Gbps.  Note that the case is significant.  Bps is bytes per second, a different value.


    De-Militarized Zone.  Refers to a network that is separate from internal LANs where sensitive information exists and public or partner access networks like the Internet.  Allowing customers to view the status of their purchase orders, for example, is typcially done with a server installed in a DMZ network.  Customers access the server via the Internet, but only the server itself has any access into sensitive business databases to retrieve customer order information and present it to the user.


    DS-3 is a communications protocol that delivers 45Mbps throughput, full duplex.  DS-3 is commonly delivered over copper or fiber, and has a protocol similar to that of T-1.


    Digital Subscriber Lines are an alternative to T-1 circuits for connecting to a Network Service Provider. DSL circuits have distance limitations not imposed by T-1 circuits but can be much faster. Circuit speeds vary based upon the type of DSL technology used, the quality of the lines carrying the signal, and the length of the signal lines. Common speeds range from 144kbps to 8Mbps; send and receive rates are often different. DSL is almost exclusively used today for delivering a connection to an IP backbone, over which other services such as Internet connectivity and VOIP can be delivered. DSL is suitable for creating VPN and RAS connections across the Internet if throughput and upload speeds are sufficient.


    Ethernet is a ubiquitous wireline network protocol and is almost always the best choice for building Local Area Networks.  Ethernet is capable of carrying various types of network traffic but is most commonly used to carry IP traffic.  Ethernet comes in four speeds and several physical formats.  Speeds are 10mbps, 100mbps, and 1Gbps, and 10Gbps in either half-duplex or full-duplex modes.  These speeds represent the bit rates of the ethernet transceivers.  Actual throughput across an ethernet segment depends upon a number of factors, including the overhead incurred by the network and application layer protocols used.  Realistic IP throughput over an ethernet network may often be 80% of the transceiver bit rate but can be higher or lower.  Common physical media for ethernet are twisted pair copper wire and various types of fiber cable.

    Fault Tolerant

     A fault tolerant product like the Titanium Mirror TM1000 can still perform its intended functions even if a failure has occurred.


    A firewall is a networking device that selectively decides which network packets are allowed to pass through it and which are not.  Contemporary firewalls are stateful, in that they understand several networking layers and can associate related network packets.  Connection-based firewalls are bidirectionally stateful and can operate if necessary on all seven layers of the network protocol stack.

    Fractional T-1

    See T-1.  A fractional T-1 is a T-1 that is configured to deliver a bandwidth less than its full rating of 1.544Mbps.  Common fractions are 1/4T (384Kbps) and 1/2T (768Kbps), however most equipment can support a fraction at any multiple of 64Kbps.

    Frame Relay

    A type of Wide Area Network, Frame Relay interconnections are available through various interconnects, such as X-25, leased line, and T-1.  Frame relay is a predominant legacy method for interconnecting Local Area Networks which is being supplanted in many applications by VPN over Internet connections.

    High Availability

    A highly available system is one that infrequently suffers a failure that cause interruption in its intended functions, and when such interruptions occur, their duration is short.  See MTBF and MTTR.

    Hot Swap

    Hot Swap denotes the ability for functional components of an overall product to be removed and inserted while the product is in operation and without powering it down.  In fault tolerant systems like the TM1000, components are redundant, allowing additional capability.  The worload of a failed or removed component is dynamically re-assigned to another active component, and, similarly, an inserted component is automatically detected and assigned its part of the overall product's workload.


    An internetwork is that part of a company's computer network that interconnects office locations, remote users, and often customers, vendors, or other business partners.  It is comprised of hardware components, like firewalls and VPN devices, and third-party networks, like the Internet or Frame Relay, leased from Network Service Providers (NSPs).


    Internet Protocol Security.  IPSEC is a VPN standard providing encrypted IP communications between two endpoints.  It tends to be interoperable and vendor neutral.  IPSEC has a large number of options and configurations that tend to make it more difficult to configure and manage.


    Internet Service Providers facilitate the connection of their customers' networks to the public internet.  ISPs are a special and very common case of NSP.


    Kilo-bits per second.  1,024bps (bits per second) = 1 kbps.


    Local Area Network.  Generally used to desctibe a common collection of computing equipment interconnected on a typically high speed, low latency network.

    Load Balancing

    An offered load is sub-divided across two or more workers for speed.  Many load balancing approaches offer higher availability by dynamically reassigning the load of a failed worker.  Titanium Mirror uses load balancing algorithms to sub-divide network traffic when two or more network paths exist to the same destination.


    Mega-bits per second.  1mbps = 1,024kbps = 1,024 * 1,024bps


    Mean Time Between Failures.  Highly Available systems strive for a very high MTBF.  Fault tolerant strategies can dramatically increase operational MTBF because a component failure does not prevent the overall system from performing its intended function.


    Mean Time To Repair, or the average time a system is not functioning in its intended capacity due to a failure condition.  Highly available systems strive for very low MTTR.


    Network Address Translation.  Contemporary NAT features also incorporate PAT, or Port Address Translation, as well.  There are specialized forms of NAT, such as DNAT, where the destination address is altered, and SNAT, where a source address is altered.  NAT has the most expressive power in systems that provide connection tracking, so packets relating to a single bidirectional communication are treated consistently.


    A traffic reporting protocol used by a large number of networking devices to send flow aggregated traffic data to centralized collectors that process, store, and analyze the data. Several versions of the NetFlow protocol exist. Version 5 is perhaps the most commonly used. Similar protocols like sFlow used in other products are often usable with minor additional work at the collector.


    Network Service Providers provide interconnections between a customer network and any public or private network not owned by the customer.  Examples include the Internet (see ISP), Frame Relay providers, even companies offering point-to-point data services over T-1 or other physical media.  NSPs are used by companies to provide internetwork connectivity between their offices and business partners.