Access Profiles
Access profiles control all aspects of remote management of Extreme Networks switches. An access profile can consist of a list of IP addresses and net masks. Each remote management method can be independently assigned to an access profile. The remote management methods under access profile control include SNMP Read, SNMP Read/Write, Web/ExtremeWare Vista, Telnet and SSH2 access.

Address
A set of characters that identifies an individual network node.

Address Table
The database maintained by a switch of all addresses it has learned and the switch ports through which these addresses can be reached. It is used by the switch to make packet forwarding and filtering decisions.

Application Switching
A Layer 4-7 data center networking device with the intelligence to detect different applications, and assign each of the requisite network resources and services for customer billing. The SummitPx1 Application Switch from Extreme does all of this at the Gigabit Ethernet line rate, performing network functions – including wire-speed TCP session analysis, termination, origination, and even modification – entirely in hardware.

ASIC
Application-Specific Integrated Circuit. A chip designed for a particular application. ASICs are commonly used in networking devices to maximize performance with minimum cost.

ASP
Application Service Provider. A business that hosts software applications on its own servers within its own facilities. Customers can access these applications via private lines or the Internet.

ATM
Asynchronous Transfer Mode. Cell-based network technology capable of transmitting data, voice, video, and frame-relay traffic.

Auto-negotiating
Two-part process by which a network device automatically senses the speed and duplex capability of another device.

Autosensing
Process during which a network device automatically senses the speed of another device.

Backbone
Interconnection in a LAN or WAN between subnetworks or workgroups. The high-speed connection to lower-speed subnets. For example, a Gigabit Ethernet backbone connected to Fast Ethernet subnets.

Backplane
Bus or switching matrix that resides within a switch or hub chassis; all traffic crosses the backplane at least once.

Bandwidth
The maximum amount of data that can be transmitted in a fixed amount of time; usually expressed in bits-per-second or bytes-per-second.

BGP
Border Gateway Protocol, an Internet protocol that enables groups of routers (called autonomous systems) to share routing information so that efficient, loop-free routes can be established. BGP is commonly used within and between Internet Service Providers (ISPs). The protocol is defined in RFC 1771.

BGP4
An extension of the Border Gateway Protocol, an Internet protocol that enables groups of routers (called autonomous systems) to share routing information so that efficient, loop-free routes can be established. BGP is commonly used within and between Internet Service Providers (ISPs).

Bidirectional Rate Shaping
A hardware-based technology that enforces traffic policies, tracks usage, and manages traffic concurrently by routing data packets to the logical ingress queue and processing policies in a bidirectional fashion. Also referred to as bandwidth by the slice.

BLEC
Building Local Exchange Carrier. A type of service provider that offers Internet access and data network services for multi-tenant buildings owned by commercial and residential real estate firms.

Broadband
The high-bandwidth communications infrastructure, or big pipes, that enable faster data transmissions and future applications for the Internet economy.

Broadcast
Message forwarded to all devices within a network. Broadcasts exist at Layer 2.

Category 5 (CAT5)
Networking standard certifying that a copper wire cable can carry data at up to 100 Mbps. See also UTP.

Chipset
A set of integrated hardware circuits, such as application-specific integrated circuits (ASICs), which perform a particular function. They are commonly used in networking devices to maximize performance with minimum cost. Extreme Networks switches are based on the powerful “i” series chipset. See also ASIC.

CLI
Command Line Interface. An interface that allows the user to interact with the operating system by entering commands and optional arguments.

Client/Server
Distributed computing model where desktop “clients” can access and share information resources from multiple “servers.”

Collapsed Backbone
LAN architecture in which the subnetwork interconnection is concentrated within a Layer 3 switch or router.

Collision
Concurrent Ethernet transmissions from two or more devices on the same segment.

Co-location
Placing equipment owned by a customer in another company's secured facility. Co-location facilities offer the space for equipment, security, and other services, as well as interconnections and Internet access for installed equipment.

Concentrator
Device used in a LAN to combine transmissions from a cluster of clients and/or servers; often called a hub.

COPS
The Common Open Policy Service protocol is used with RSVP and policy-based networking for the communication between a network device and an authoritative policy management entity. Typically, this is a policy server or call admission control server process. It defines the transport and formatting of data used in this communication.

Data-link Layer
See Layer 2.

Destination Address
The IP or MAC address of the node that is to receive the packet.

DHCP
Dynamic Host Control Protocol. An effective way to dynamically assign and reuse a fixed number of IP addresses when there are more devices on the network than addresses available. A DHCP server dynamically assigns IP addresses to devices requesting them. These address assignments expire after a time specified by the network manager. The DHCP server then reassigns these addresses to other devices as needed. DHCP is an extension to BOOTP in which the address assignments are static.

DiffServ
An IETF standard developed to help solve IP quality problems. DiffServ operates at Layer 3 and allows out-of-band negotiation. DiffServ relies on traffic conditioners sitting at the edge of the network to indicate each packet's requirements.

Duplex
A communication mode in which a device can send and receive over data the same link. The device can operate in full-duplex and half-duplex.

Dynamic Link Context System
The Dynamic Link Context System allows policy-setting based on user names or desktop devices, and automatically maps them to lower-layer addresses.

DVMRP
The Distance Vector Multicast Routing Protocol is used for the communication and distribution of multicast routing table information. It is based on the RIP protocol used in unicast routing. See IETF document draft-ietf-dvmrp-v3-07.

Enterprise Desktop Switch
An Enterprise Desktop Switch combines the low cost and simplicity of a stackable edge device with the enterprise-class features found in more expensive chassis-based switches.

Equal Cost Multipath Routing (ECMP)
Distributes network traffic across multiple high-bandwidth links to increase performance. Extreme's OSPF implementation supports multiple equal-cost paths between points and divides traffic evenly among the available paths. As many as four links may be involved in an ECMP link and traffic is shared on an IP source/destination address session basis.

ERP
Enterprise Resource Planning. A business management system that integrates all facets of the business, including planning, manufacturing, sales, and marketing. As the ERP methodology has become more popular, software applications have emerged to help business managers implement ERP.

ESRP
The Extreme Standby Router Protocol enables host devices to continue communicating even if a physical router fails.

Ethernet
An IEEE networking standard, originally developed by Xerox, for transmitting data at 10 Mbps.

Extranet
A secure web site for customers or suppliers rather than the general public. It can provide access to paid research, current inventories and internal databases, virtually any information that is private and not published for everyone. An extranet uses the public Internet as its transmission system, but requires passwords to gain access.

Fast Ethernet
An IEEE networking standard for transmitting data at 100 Mbps. See 100BASE-TX also.

Fault-tolerance
The ability of a device to prevent or recover from network and internal failures. Key elements of fault tolerance include hot-swappable modules, redundant load-sharing power supplies, passive backplanes, and redundant cooling systems.

FDDI
Fiber Distributed Data Interface. An ANSI networking standard for 100 Mbps fiber-optic LANs; widely used as a backbone technology to interconnect several Ethernet or Token Ring networks.

Filter
An action of the switch to discard certain types of data packets.

Firmware
Software routines that are permanently written onto read-only memory.

Full-duplex
The communication mode in which a device simultaneously sends and receives over the same link, doubling the bandwidth. A full-duplex 100Mbps connection has 200Mbps of bandwidth. A full-duplex 1000Mbps connection has 2000Mbps of bandwidth.

GBIC
Gigabit Interface Connector. The physical connection to Gigabit Ethernet media.

Gbps
Gigabits per second.

Gigabit Ethernet
Networking standard for transmitting data at 1000 Mbps.

Half-Duplex
The communication mode in which a device is capable of either sending or receiving, but not simultaneously.

Hardware Address
A device’s physical or media access control (MAC) address.

Header
Special information contained in the beginning of a frame.

Host
Any entity on the network that can initiate a transmission. A router, a server or a workstation.

HTTP
Hypertext Transfer Protocol. Defines how requests for HTML and graphics files which make up a web page are handled between the web server and the client browser.

Hub
An unintelligent network device that sends one signal to all of the stations connected to it.

ICMP
Internet Control Message Protocol. The part of the IP protocol that handles error and control messages. The switch issues ICMP messages to report IP datagram problems back to the their source.

IGMP
Internet Group Management Protocol. A protocol that hosts use to keep local routers informed of their membership in multicast groups. When all hosts leave a group, the router no longer forwards datagrams that arrive for the group.

IGMP Snooping
IGMP Snooping provides a method for intelligent forwarding of multicast packets within a Layer 2 broadcast domain. By snooping IGMP registration information, a distribution list of workstations is formed that determines which end-stations will receive packets with a specific multicast address.

IEEE 802
Set of Institute of Electrical and Electronic Engineers standards for defining methods of access and control on LANs.

Internet
The Internet is made up of more than 65 million computers in more than 100 countries covering commercial, academic and government endeavors.

Intranet
An in-house web site that serves the employees of the enterprise. Although intranet pages may link to the Internet, an intranet is not a site accessed by the general public.

IP
A Layer 3 (network layer) protocol that contains addressing information and control information that allow packets to be routed.

IPX
Internetwork Packet Exchange. A networking protocol used by the Novell® NetWare® operating systems. Like UDP/IP, IPX is a datagram protocol used for connectionless communications.

ISO
International Standards Organization.

Latency
Any delay introduced into the network that prevents packet forwarding at wire speed.

LAN
Local Area Network. A network where computers are connected in close proximity, such as in the same building or office park; a system of LANs connected at a distance is called a wide-area network (WAN).

Layer 1
The first, or physical, layer of the open systems interconnection (OSI) model. Delivers data across a network link. This layer must regulate signaling and keep the signal strong. Hubs, repeaters and concentrators operate at Layer 1. All packets received are repeated on the wire.

Layer 2
The second, or data-link layer, of the open systems interconnection (OSI) model. The media access control (MAC) layer. Transmits packets across a Layer 1 physical link by reading the hardware or MAC source and destination addresses in each packet. Switching operates at Layer 2. Switches have a forwarding table of the hardware addresses of the devices connected to them. When packets arrive, the switch reads the Layer 2 address and if it matches one in the table, forwards it to that port. Otherwise, it forwards or “floods” the packet to all ports.

Layer 3
The third, or routing, layer of the open systems interconnection (OSI) model. The network layer routes data to different LANs and WANs based on network address.

Layer 4
The fourth, or transport, layer of the open systems interconnection (OSI) model. It encompasses network services that provide end-to-end management of a communications session.

Layer 7
The seventh, or application, layer of the open systems interconnection (OSI) model. It defines the services that directly support applications such as software for network management, electronic mail or file transfers.

Link Aggregation
The grouping of multiple network links into one logical high bandwidth link. By grouping four 100 Mbps Ethernet connections into one logical link, you can create up to 800 Mbps of bidirectional throughput between the server and the switch.

MAC
Media Access Control. Layer 2 of the open systems interconnection OSI model. The data-link layer responsible for scheduling, transmitting and receiving data on a local area network.

MAC Address
Media Access Control address. The unique physical address of each device's network interface card.

MAN
Metropolitan Area Network, a data network designed for a town or city. In terms of geographic breadth, MANs are larger than local area networks (LANs), but smaller than wide area networks (WANs). MANs are usually characterized by very high-speed connections using fiber optical cable or other digital media.

Mbps
Megabits per second.

Meshed Topology
A network built with a mixture of different network topologies. For example a high bandwidth backbone network that connects to a collection of slower segments.

MIB
Management Information Base. A database of information that the switch makes available to network management systems. For example, traffic statistics and port settings.

MPLS
Multiprotocol Label Switching. A switching protocol that integrates Layer 2 information about network links into Layer 3 in order to simplify and improve IP packet exchange.

Multicast
A packet, or transmission, destined for many clients.

Multimode Fiber Cable
Fiber cable with a wide core. Light is reflected along the core at multiple angles, and is propagated along multiple paths, each path with a different length and hence a different time to traverse the fiber. These multiple angles or modes cause the signal elements to spread out in time, so that distortions occur that limit the distance over which the integrity of the light signal can be maintained. Multimode fiber is the predominant type of LAN fiber installed within buildings and is less expensive than single mode fiber.

NIC
Network Interface Card. An expansion board which goes into a workstation or server and provides the connection to a network.

Non-blocking
A switch's ability to transmit and receive packets on all ports simultaneously, at wire speed.

OC
Optical Carrier, used to specify the speed of fiber optic networks conforming to the SONET standard. OC-1 = 51.85 Mbps, OC-3 = 155.52 Mbps, OC-12 = 622.08 Mbps, OC-24 = 1.244 Gbps, OC-48 = 2.488 Gbps, OC-96 = 4.976 Gbps, OC-192 = 9.6 Gbps and OC-255 = 13.21 Gbps

Over-subscription
Over-subscription or over-subscription ratios deal specifically with points in a network where bottlenecks occur. The impact of improper over-subscription ratios is congestion, which causes packet loss. Over-subscription ratios are calculated by adding the potential bandwidth requirements of a particular path and dividing the total by the actual bandwidth of the path. Although a ratio larger than 1:0 is considered over-subscribed, it does not necessarily mean congestion will occur.

OSPF
Open Shortest Path First. A routing protocol that maintains a map of all other routers and the networks to which they connect. Sends short messages asking whether a neighbor is alive and reachable. More efficient, scalable than vector-distance routing protocols that maintain tables of all known destinations and number of hops to reach them.

Packet-over-SONET
A metropolitan area network (MAN) or wide area network (WAN) transport technology that carries IP packets directly over SONET transmission without any data link facility such as ATM in between. Packet-over-SONET is intended to transmit data at the highest rates possible, because SONET has a smaller packet header overhead than ATM (28 bytes out of an 810-byte frame compared with 5 out of a 53-byte ATM cell).

PIM Dense Mode
Protocol Independent Multicast Dense Mode. A multicast protocol similar to DVMRP in that it uses Reverse Path Forwarding but does not require any particular unicast protocol.

PIM Sparse Mode
A multicast protocol that works by defining a rendezvous point that is common to both sender and receiver. Sender and receiver initiate communication at the rendezvous point, and when flow begins it occurs over an optimized path.

Policy-Based Quality of Service (QoS)
A network service that provides the ability to prioritize different types of traffic and manage bandwidth over a network.

POP
Point of presence. The point where a long distance carrier connects to a local phone company or to a user if a local company is not involved. For online services and Internet service providers, the POP is the local exchange users dial into via modem.

Port Density
Number of ports, either physical or logical, per network device.

Port Mirroring
A switching feature that allows one port’s media access control (MAC) layer data to be replicated to another port for monitoring by a network analyzer.

RADIUS
Remote Authentication Dial-In User Service, an authentication and accounting system used by many Internet Service Providers (ISPs). When you dial in to the ISP you must enter your username and password. This information is passed to a RADIUS server, which checks that the information is correct, and then authorizes access to the ISP system.

RAN
Regional area network. A data network that interconnects businesses, residences and governments in a specific geographic region. RANs are larger than local area networks (LANs) and metropolitan area networks (MANs), but smaller than wide area networks (WANs). RANs are usually characterized by very high-speed connections using fiber optic cable or other digital media.

Redundant PHY
One of the most effective, least costly and simplest ways to achieve link redundancy with sub-second recovery is by using redundant physical connections, also called redundant PHY (pronounced `fî). With this type of redundancy, there is typically an active primary link and a standby secondary link. For example, a single gigabit port may have two physical connections. If the primary link fails, the secondary link takes over in less than one second.

RIP
Routing Information Protocol. A protocol defined by RFC 1058 that specifies how routers exchange routing table information. With RIP, routers periodically exchange entire tables.

RMON
Remote Monitoring. A network management protocol that allows network information to be gathered at a single workstation.

Routing
The process of delivering a message across a network or networks.

Router
A network device that forwards packets to destinations based on Layer 3 IP addresses. A router implements various protocols to maintain information on the location of other routers. A router reads the Layer 3 network address information in every packet that it receives and determines whether it should be dropped or forwarded. If it is to be forwarded, the router looks in its routing table to find the best route between a sender and receiver.

RSVP
Resource Reservation Protocol. An IETF standard used to provide quality of service by reserving bandwidth before packet transfers to insure its availability.

Secure Shell (SSH)
Secure Shell is a program to log into another computer over a network, to execute commands in a remote machine, and to move files from one machine to another. It provides strong authentication and secure communications over insecure channels. SSH protects a network from attacks such as IP spoofing, IP source routing, and DNS spoofing. An attacker who has managed to take over a network can only force SSH to disconnect. He or she cannot play back the traffic or hijack the connection when encryption is enabled.

Segment
Section of a network that is bounded by bridges, or switches; dividing an Ethernet into multiple segments is a common way to increase bandwidth on a LAN.

Single Mode Fiber Cable
Fiber with a relatively narrow diameter, through which only one mode will propagate. Carries higher bandwidth than multimode fiber, but requires a light source with a narrow spectral width.

SNMP
Simple Network Management Protocol. A standard for gathering statistical data about network traffic and the behavior of network components; SNMP uses management information bases (MIBs), which define what information is available from any manageable network device.

Snooping
Looking into the packet to obtain information.

SONET
Synchronous Optical Network, a standard for connecting fiber-optic transmission systems. SONET defines interface standards at the physical layer of the OSI model. The standard defines a hierarchy of interface rates that allow data streams at different rates to be multiplexed. SONET establishes Optical Carrier (OC) levels from 51.8 Mbps (about the same as a T-3 line) to 9.2 Gbps. With the implementation of SONET, communication carriers throughout the world can interconnect their existing digital carrier and fiber optic systems. The international equivalent of SONET, standardized by the ITU, is called SDH.

Source Address
The IP or media access control (MAC) address of the node issuing the packet.

Spanning Tree
A process used to eliminate redundant data routes and increase network efficiency.

Store-and-forward
Switching feature where the receiving port receives the entire incoming frame and stores it in the buffers before forwarding it to the destination port.

Switching Fabric
A term used to specify the maximum bandwidth of a switch at the backplane.

Subnet Addressing
A method that a manager can use to span multiple physical networks using a single IP network address. Local routers and intelligent switches use extensions of the IP network address to identify and route traffic to local, physical segments.

Subnet Mask
A number that a manager enters to tell the switch how to filter incoming packets. For example, a subnet mask of 255.255.0.0 for the address 192.3.1.254 tells the switch to only accept traffic destined for IP addresses that begin with 192.3. All other packets are dropped.

Switch
A network device that filters and forwards packets between LAN segments and or desktops.

TCP/IP
Transmission Control Protocol/Internet Protocol. The suite of communications protocols used to connect hosts on the Internet.

T1/E1
A dedicated, point-to-point digital connection configured to carry voice or data traffic, widely used for private networks as well as interconnections between an organization's PBX or LAN and the telco.

Telnet
The protocol within the TCP/IP protocol suite which provides a terminal emulation function.

Transparent LAN Service (TLS)
A communications service from a local telephone company or common carrier that links remote LANs together.

Topology
The physical or logical layout, or configuration of a network.

Transparent Web Cache Redirection
The ability inherent in Extreme Networks "i" series switches to redirect web traffic using Layer 4 criteria, such as HTTP Port 80, at wire speed to one or more load-shared ports across several web cache servers without the reconfiguration of browser applications.

Uplink
A connection from a lower to higher device. A hub to a switch, a switch to a router, a router to a server.

UDP
User Datagram Protocol. A connectionless protocol that, like TCP, runs on top of IP networks.

Unicast
A packet destined for only one address.

UTP
Unshielded Twisted Pair. Cabling with wires that are twisted around each other; the individual wires are uninsulated. See also Category 5.

VDSL
Very High Speed Digital Subscriber Line.Transmits data in the 10 Mbps-55Mbps range over short distances, usually between 1000 and 6000 feet, over voice-grade wire.

VID
VLAN Identifier. A number identifying a specific VLAN.

VLAN
Virtual LAN. A logical, not physical, group of devices, defined by software. VLANs allow network administrators to resegment their networks without physically rearranging the devices or network connections.

Voice-grade Wiring
The term generally refers to analog lines with the bandwidth required to transmit human voice, typically about four thousand Hertz (4KHz).

Virtual Private Network (VPN)
A private network that is configured within a public network.

WAN
Wide Area Network. A network that uses telecommunications technology to connect computers or networks over long distances.

WDM
Wavelength Division Multiplexing. A type of multiplexing developed for use on optical fiber. WDM modulates each of several data streams onto a different part of the light spectrum.

Web Hosting
Placing a customer’s web page or web site on a commercially owned web server. A single server can hold hundreds or even thousands of small web sites, while larger web sites use a dedicated server or multiple servers.

WINS
Windows Internet Naming Service. A system that determines the IP address associated with a particular network computer.

Wire Speed
The theoretical, maximum rate at which packets can be transmitted and received on a network interface.

Workgroup
Collection of computers that are grouped for sharing resources such as data and peripherals.