A special-function device that combines integrated software and hardware into a single solution in order to eliminate the installation and configuration issues associated with implementing software applications on general-purpose server platforms.
The numerous interactions and acknowledgements between client and server required to perform each specific task. The more “turns” an application requires, the greater the effect of network latency is multiplied – potentially leading to significant negative impact on end-to-end application performance.
An approach to network management that focuses on the performance and behavior of applications – rather than the generic movement of packets across local and wide-area links.
The capacity of a network link to carry packets. Also referred to as network speed or WAN speed, bandwidth is measured in bytes per second (bps).
A technique used in network emulation to recreate the limited bandwidth of a WAN link by restricting throughput on a LAN link in the lab.
A set of techniques for improving application performance over the network by keeping certain data close a processing resource (i.e. a server or a client) where it is likely to be needed based on previous behaviors or actions.
A set of techniques for using network resources more efficiently by taking advantage of opportunities to reduce the total volume of bits that need to be transmitted, such as those that arise because of redundancies in data.
Customer relationship management. A category of software that manages and integrates customer-facing business processes such as sales, service/support, and market analytics.
Creation of a model based on actual characteristics captured from a live production environment – as opposed to theoretical modeling.
The response times of an application across the entire application infrastructure, measured from the application front end (usually the end-user’s desktop) through the network to the back-end server(s).
The generation of traffic loads that reflects the behavior of end-users as they interact with an application. Also referred to as client simulation.
The behavior and responsiveness of an application as it actually manifests on an end-user’s remote desktop.
Enterprise Resource Planning. A category of software that manages and integrates a variety of core business functions such as financials, supply-chain management, human resources, and project management.
A high-speed protocol used primarily for transferring data in storage area networks (SAN).
The fixed time it takes for a packet to be transmitted over a specific network link, determined by the speed of the link and the size of the packet. Insertion delay accumulates at each hop in a multi-hop network route, since the entire packet must be received (stored) before it can be transmitted (forwarded) to the next hop.
The variation in latency between successive packets across a given network connection. Jitter can be quantified as the weighted average of the latency difference between every pair of consecutive packets received.
Local Area Network – that is, the network infrastructure within a room, building, lab or department.
Also referred to as theoretical modeling. Creation of a model based purely on algorithms and formulas – as opposed to empirical modeling.
Mean Opinion Score. A numerical indication of the perceived quality of received media after compression and/or transmission, expressed as a single number from 1 to 5 with 1 being the worst quality and 5 being the best.
Multiprotocol Label Switching. An IETF standard originally developed by Cisco to simplify and optimize IP transport based on characteristics of both the network and the type of data being transporte
A category of solution used to assess the state of a network’s physical infrastructure – including the integrity of intended connections, the presence of unintended connections (or “shorts”), measurement of resistance between circuit end-points, and any errors in the way the network is wired.
A technique whereby the properties of an existing, planned and/or non-ideal network are reproduced in a lab in order assess performance, predict the impact of change, or otherwise optimize technology decision-making. Network emulation includes the introduction of WAN speeds through bandwidth throttling and the creation of network impairments such as latency, jitter, packet loss and congestion.
Network errors are divided to two main categories: packet loss and packet corruption. Packet loss is determined by the several factors, including:
- Network load, which can cause a packet queue in a network hop to overflow – causing new packets to be dropped due to lack of memory space. This typically results in a “burst” loss, where several packets from one endpoint are lost at once.
- Limited bandwidth, including QoS parameters such as Frame Relay CIR (Committed Information Rate) or Diffserv bandwidth polices that define a data rate limit which, when exceeded, can result in dropped packets.
- Congestion avoidance mechanisms, such as RED (Random Early Detection), can selectively decode and drop packets in order to avoid what seems to be an upcoming congestion trend.
- IP header corruption, which will cause the next router receiving the corrupted packet to drop it.
- Hardware faults, such as link disconnections and device shutdown.
Packet corruption on a route is caused by errors in the physical layer, which in turn cause data bits to toggle. This phenomenon is measured in BER (Bit Error Rate).
Network impairment is used in WAN/network emulation/simulation to recreate network latency, jitter, packet loss, and other attributes of a real-world WAN on a LAN link in the lab.
The links, routers, switches, gateways, firewalls and other components that enable the transport of data packets across the enterprise.
The time it takes for a packet to traverse an end-to-end network path, determined primarily by the cumulative effect of the propagation delays across each link, the insertion delays at every device along the path, and the queuing delays at every device along the path.
A technique whereby the behavior of a network is modeled using software. When a network simulation program is used in conjunction with live applications in order to observe end-to-end performance to the user desktop, this technique is also referred to as network emulation.
The failure of packets to reach their destination or, more specifically, the rate at which this phenomenon occurs. Packet loss can result from a variety of factors – including overflow in the memory space of a network device, limited bandwidth, congestion avoidance mechanisms, IP header corruption and hardware faults.
A dedicated service provider network connection with a capacity of less than a T1, which is 1.544 Mbit/s.
The time it takes for a packet to traverse a given network link, determined primarily by the distance between the transmitter and the receiver.
Quality Assurance. Specifically, the testing performed on applications during and after development to ensure their ability to provide required functionality, stability, speed of response, etc.
Quality-of-Service. The assurance that packets will be forwarded at a certain rate across the network and/or the prioritization of certain packets over others.
Functions provided over the network that enable basic data operations and/or support business applications. Examples include directory services (Active Directory, LDAP), FTP (File Transfer Protocol), HTTP (Hypertext Transfer Protocol), and SMTP (Simple Mail Transfer Protocol).
Business applications that are accessed over the network, but require the presence of some minimal amount of code (such as a Java “applet”) on the desktop.
The re-creation of an enterprise network within a lab environment.
Voice-Over-IP. The transport of voice traffic over the same IP networks used for data communications, rather than separate analog infrastructure.
Virtual Private Network. A set of techniques for dedicating and securing network resources to a specific user, application and/or service – even though the network is in fact shared by multiple users, applications and/or services.
Wide Area File Services. A set of techniques (which may include protocol optimization, compression, caching and replication) for enabling remote users on a WAN to share files with LAN-like performance.
Wide Area Network – that is, the network infrastructure that connects enterprise locations to each other.
A set of technology solutions that overcome the effects of network latency by a variety of techniques such as allowing protocol interactions to take place in parallel, rather than sequentially, caching, QoS and compression.
See "network emulation".
Applications that are accessed over the network and only require the presence of a standard browser on the desktop.