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Frequently Asked Questions

QoS General Topics
1. What is the terminology used by QOS?
2. Why should I implement QOS?
3. What are the queuing mechanisms?
4. What are QOS Policies and how do they translate to business applications?
5. What is Differentiated Services (Diff-Serv)?
6. What is Traffic Shaping / Conditioning?
7. What is Bandwidth Brokering?
8. What is MPLS?

NeuTrans
1. How does NeuTrans do network discovery?
2. How can "Adaptive Learning" help manage QoS on my Network?
3. What are the Fault Tolerant Capabilities of NeuTrans?
4. Will NeuTrans scale with the growth of my network?
5. Does NeuTrans work with all vendor hardware?
6. What are Role definitions?
7. What are 'point bandwidth management solutions' and how is Asce Networks NeuTrans different?

Development (COPS / API / SDK)
1. What is Common Open Policy Service (COPS)?
2. What is Resource Reservation Protocol (RSVP)?
3. What is the Difference between COPS-PR and COPS-RSVP?
4. What is "Self-Provisioning", and how can this be integrated into NeuTrans?

QoS General Topics

1. What is the terminology used by QoS?

Asce Networks has put together a glossary of terms to assist you as a resource in getting familiar with QoS terminology.Go to our Glossary for more info.

2. Why should I implement QOS?

Quality of Service can encompass many aspects of a network. People, users and/or customers view network quality as the process of delivering data in a reliable and efficient manner. As the reliable delivery of data has moved from a luxury to a necessity, so has the intelligence of the network. As customer demand increases, the ability to provide this intelligence has become a focus. The addition of increased bandwidth is no longer an option. The convergence of Voice, Video, and Data has necessitated that not only should the data path be reliable but efficient. Some applications require not only reliable delivery but also require managed latency. With Quality of Service this has now become a reality and Asce Networks' NeuTrans is the tool needed to manage these mechanisms.

3. What are the queuing mechanisms?

There are typically three methods of queuing:
FIFO (First in First Out) - FIFO queuing is a strict queuing method of transmitting packets in the order in which they are received.
CBQ (Class Based Queuing) - A queuing methodology in which traffic is divided into classes and separated into queues according to the assigned class.
WFQ (Weighted Fair Queuing) - WFQ allows multiple queues to be defined for multiple traffic flows. The administrator creates different queue sizes and delegates what traffic is destined for a particular queue.
In addition to the 3 basic queuing mechanisms, Asce Networks' NeuTrans utilizes advanced queuing methodologies for Cisco, Juniper and Nortel Networks etc. routers that combine characteristics of the basic types. Examples of these mechanisms are; CQ (Custom Queuing), PQ (Priority Queuing), CCBQ (Custom Class Based Queuing) and CBWFQ (Class Based Weighted Fair Queuing).

4. What are QOS Policies and how do they translate to business applications?

QOS policies are a compiled set of instructions that define how networking devices should prioritize and forward network traffic. Business applications can suffer tremendously when combined with other traffic types. In a best-effort networking environment, QOS can truly be appreciated when Business Applications compete with non-business downloads, or a company's CRM application is battling the morning rush of web browsing. For the Service Provider, the ability to offer premium services based on flexible quality levels that are adaptive to the changing demands of users can prove to be the competitive edge needed.

5. What is Differentiated Services (Diff-Serv)?

Diff-Serv is a methodology used to specify and control network traffic so that certain types of traffic get priority. Diff-Serv is more complex than traffic tagging in that Diff-Serv has the ability to handle packets according to a Per Hop Behavior (PHB) that is selected on the basis of the contents of the DS field in the packet header.

6. What is Traffic Shaping/Conditioning?

Traffic Shaping or Conditioning is the enforcement of the rules on network packets based upon QOS policies. In QOS networks, it is necessary to specify the traffic profile for a "connection" to decide how to allocate various network resources. Traffic Shaping/Conditioning ensures that traffic entering at an edge or a core node adheres to a specified profile.

7. What is Bandwidth Brokering?

Bandwidth Brokering is the concept of providing service levels with quantitative, absolute bandwidth assurance. The service may be provided entirely within one domain, from domain-edge to domain-edge or across a number of domains. Bandwidth brokers are designed to be configured with policies within an organization that monitor current allocation of marked traffic and make decisions on new requests based on current network resources.

8. What is MPLS?

MPLS (Multi Protocol Label Switching) is a technology that overlays a label swapping approach to packet forwarding on top of the well-understood hop-by-hop routing mechanisms of IP networks. Fundamentally, it separates the "where" of packet forwarding from the "how". This technique brings a number of benefits meeting the needs of business and ecommerce with IP networks.
A new standard for a new world of networking, MPLS is an emerging Internet Engineering Task Force (IETF) standard based on Cisco Tag Switching. MPLS is an innovative approach that uses a label-based forwarding paradigm. Labels indicate both routes and service attributes. At the ingress edge, incoming packets are processed and labels selected and applied. The core merely reads labels, applies appropriate services, and forwards packets based on the label. Processor-intensive analysis, classification, and filtering happens only once, at the ingress edge. At the egress edge, labels are stripped, and packets forwarded to their final destination.

NeuTrans

1. How does NeuTrans do network discovery?

NeuTrans discovers network devices using two methods, based on whether or not the device support the Common Open Policy System (COPS). For COPS compliant devices, the device itself initiates communication with the Policy Server. Non-COPS devices are discovered via the SNMP. The system administrator enters one or more SNMP community strings into the Policy Console, and discovery of devices is based on matched community strings.

2. How can "Adaptive Policy Technology" help manage QoS on my Network?

Adaptive Policy Technology simplifies Policy administration by detecting the QoS capabilities of different OS versions. NeuTrans interrogates the router to determine its QoS capabilities. The system then implements policies based on capabilitiesit received during the interrogation process. This allows users to upgrade the OS on their current QoS enabled devices, without necessitating the upgrade of NeuTrans.

3. What are the Fault Tolerant Capabilities of NeuTrans?

Every component of the NeuTrans has fault tolerant capabilities. The flexibility of the Policy Server allows for configuration as a "Hot-Standby" or "Load Balancing", where the Policy Servers would share managed devices. The Policy Administrator can be configured as a Primary or Backup component. In the event of a failure of the Primary Policy Administrator the Backup Administrator would assume responsibility as the Primary Policy Server. The system also supports the autonomous operation of Policy Servers and could preclude the necessity of the Policy Administrator. In this error condition the current deployed policies would be enforce, but new policies could not be deployed.

4. Will NeuTrans scale with the growth of my network?

Absolutely. Asce Networks NeuTrans has been designed to handle tens of thousands of devices under management, through its scalable, distributed architecture. When it comes to the number of users and applications, the limits of the devices in the network will be reached well before NeuTrans.

5. Does NeuTrans work with all vendor hardware?

Asce Networks' mission is to allow network managers who manage IP networks to deliver stable, predictable performance from those networks using a powerful, policy-based management approach. Asce Networks is committed to maximizing the capabilities of existing network infrastructure, and to that end, we support multi-vendor networks and existing devices through our open Device API and SDK, ensuring network managers have a free choice of device vendors in the future. So, networks can be built with specialist devices such as traffic shapers and firewalls, safe in the knowledge that the maximum abilities of these devices can be unleashed by Asce Networks. Currently, NeuTrans supports Cisco, Juniper, Nortel Networks, Lucent, Riverstone, Unisphere, Avici etc.

6. What are Role definitions?

Role definitions allow users to assign particular interface types and speeds to groups (Roles). These Roles can then be used in the definition of Policy. This provides for greater ease in the creation of policy by allowing the user to incorporate these roles, rather than the individual interfaces, into the Policy definition.

7. What are 'point bandwidth management solutions' and how is Asce Networks NeuTrans different?

'Point bandwidth management solutions' are extremely effective in addressing issues of traffic prioritization at the access link to a web server farm for instance. Without Asce Networks NeuTrans and the appropriate device driver, they require prohibitive levels of effort to deliver differentiated levels of service on a co-ordinated, network-wide basis in any sizable network.

Development (COPS / API / SDK)

1. What is Common Open Policy Service (COPS)?

COPS is a reliable, responsive protocol for policy-based network management systems, enabling the dynamic and proactive management of network devices. By integrating COPS, hardware manufactures and equipment providers can "policy-enable" their products, offering complete support for industry standard policy management systems such as Asce Networks' NeuTrans. By integrating the standards-based COPS protocol, networking companies can extend their products to access intuitive, policy-enabled networking solutions.

2. What is Resource Reservation Protocol (RSVP)?

One of the key IETF protocols that communicates the QoS requirements for a given application to a device in the path of the transmission. A reservation for the required bandwidth is allowed or denied depending on the current network conditions. By itself, Resource ReSerVation Protocol provides a way to reserve capacity one device at a time. In a centrally managed QoS system, Resource ReSerVation Protocol can be implemented according to policies that apply across the network. Resource ReSerVation Protocol is expected to be utilized predominantly in the campus-level networks.
RSVP is designed to operate within the framework of current and future routing protocols. An RSVP process consults the local routing database(s) to obtain routes. Routing protocols determine where packets get forwarded; RSVP is only concerned with the Quality-of-Service for those packets that are forwarded in accordance with a routing protocol.

3. What is the Difference between COPS-PR and COPS-RSVP?

As previously stated, COPS is a reliable, responsive protocol for policy-based network management systems, enabling the dynamic and proactive management of network devices.
The differences between COPS-PR and COPS-RSVP are as follows: The COPS-PR architecture is one of provisioning. The Policy Enforcement Point (PEP) sends to the Policy Decision Point (PDP) a request with a list of policy requirements (Queuing, Marking¡ etc.). The PDP provides the policy in a PDP-decision. Afterwards the COPS-conversation can be potentially limited to Keep-Alive. The PDP may send unsolicited policy updates later, and the PEP may issue more requests or update past requests. In the COPS-PR architecture the Global pre-prepared policy is used to manage all devices.
The COPS-RSVP architecture is one of outsourcing. There is no global pre-prepared policy. The PEP requests the PDP for policy action only when an outside source triggers it for action. The PDP decision is relatively simple, permit/deny. As an example the RSVP flow receiver (the outsource) sends a reservation request to the PEP (a router), asking for a certain bandwidth for the RSVP Flow. The PEP forwards the request to the PDP. The PDP decision might be: accept / reject / accept with changes. To summarize, in the provisioning model, all QOS is pre-prepared and dynamic provisioning is managed and allocated by the PDP. In the outsourcing model the QOS is not provisioned until an outside source (outsourcing) requests QOS.

4. What is "Self-Provisioning", and how can this be integrated into NeuTrans?

Self-Provisioning is a methodology that allows customers / clients to select and deploy QoS mechanisms. Part of Asce Networks' overall solution is the ability to have customers /clients provision network bandwidth and QoS without the need for IT / IS intervention.
From a Service Providers perspective they could have available 4 classes of service (Bronze, Silver, Gold, and Platinum). The customer decides to upgrade from their current class of service (Bronze) to Gold. The customer would supply customer information and then select the appropriate service (Gold). The underlying functions would then provide the appropriate bandwidth / QoS, and adjust billing records as appropriate. From an enterprise perspective, it can be used when the CEO wants to do video conferencing. The CEO can select the appropriate attendees, conference length, and the network will be provisioned accordingly.

Glossary of Terms

This document provides brief definitions for key Performance Provisioning and Quality of Service (QoS) terms. These terms are used on the Asce Networks' Web site and throughout the industry.

● Adaptive Policy Technology
A component of the Asce Networks NeuTrans Policy Server. Adaptive Policy technology allows Policy Servers to dynamically adapt to changes in the network infrastructure. QoS capabilities are highly dependent upon vendor type, model number, technology type, and software version. The Adaptive Policy technology automatically learns this information and ensures that NeuTrans will dynamically adapt to network changes.

● Administrative Domain
Any separately managed network, whether departmental, divisional, or company-wide. There are several different kinds of domains, such as NT domains and IP domains. For quality of service enforcement purposes, a network domain refers to any domain that shares a common QoS policy. Usually managed by a single corporate entity.

● Admission Control
Admission Control Any technique for controlling the admission of network traffic from outside a given administrative domain.

● Asynchronous Transfer Mode (ATM)
A data framing and transmission architecture designed to carry voice, video and data, which has built-in QoS capabilities. Operates at Layer 2 of the OSI model. Although relatively few native ATM applications exist, TCP/IP traffic can be sent over an underlying ATM layer. This practice is now prevalent for the implementation of Wide-Area Networks and the Internet backbones operated by major telecommunications companies. ATM-based technology is also finding its way into systems for improving TCP/IP connectivity on corporate networks. Although generally considered too costly to be an end-to-end (desktop-to-desktop) QoS solution, ATM services are likely to co-exist with QoS-enabled IP networks for many years to come.

● Backbone
The superstructure of the Internet where the national Internet Service Providers link directly to each other. Sometimes used to refer to the trunkline of any network. Usually the backbone speed is significantly higher than that of the networks that it connects. A connecting network highway for major networks including large enterprise networks and the Internet.

● Bandwidth
A measure of data transmission capacity, usually expressed in kilobits per second (Kbps) or megabits per second (Mbps). Bandwidth indicates the theoretical maximum capacity of a connection, but as the theoretical bandwidth is approached, negative factors such as transmission delay can cause deterioration in quality. If you increase bandwidth, you can transfer more data. Network bandwidth can be visualized as a pipe that transfers data. The larger the pipe, the more data can be sent through it.

● Bandwidth Manager
A rudimentary traffic management solution deployed at congestion points that limits access to network resources (e.g., it might prevent Pointcast-like "push" traffic from entering the network). Because a bandwidth manager solution often requires locating a proprietary hardware device directly on the network, it may be an additional point-of-failure. Not an end-to-end solution, a bandwidth manager cannot coordinate multiple traffic flows or resolve conflicting QoS requests made by multiple clients. See also PointQoS.

● Best-effort Service
The default behavior of TCP/IP networks in the absence of QoS measures. TCP/IP nodes will make their best effort to deliver a transmission but will drop packets indiscriminately in the event of congestion.

● Class-based Queuing (CBQ)
A methodology for classifying packets and queuing them according to criteria defined by an administrator. The queuing system is designed to prevent any one application from monopolizing the system. Also known as Custom Queuing. See also Weighted Fair Queuing.

● Class of Service (CoS)
A category based on type of user, type of application, or some other criteria that QoS systems can use to provide differentiated classes of service.

● Congestive Avoidance
An attempt to head off congestion before it can occur. Random Early Detection (RED) is an example. See also Congestion Management.

● Congestion Management
A mechanism that imposes order when traffic exceeds network capacity. It determines whether some packets must be discarded, and, if so, it preserves the more important packets. Queuing, scheduling, and traffic shaping are among the most popular techniques. See Also Congestion Avoidance.

● Controlled-load Service
A high level but not guaranteed service. In the proposed IETF Integrated Service model, this level of service is designed for multimedia applications where time delay is not critical but quality of the delivery is important. This service is appropriate for applications such as one-way voice or video, but not for real-time applications, such as teleconferencing. See also Guaranteed Service.

● Converged Network
A network that combines varied traffic types such as data, voice, and multimedia. Most analysts expect the converged network of the future to be based on Internet protocols. This trend is evident in corporate networks, which are starting to combine videoconferencing on their traditional data networks, as well as in the merging of the telephone, cable television, and Internet service industries.

● Common Open Policy Service (COPS)
An IETF proposed standard for implementing QoS policies as an end-to-end service. Common Open Policy Service allows a policy server to control the devices on the network, such as routers and switches, so that a cohesive policy based on business priorities can be achieved. Common Open Policy Service is a companion protocol to Resource ReSerVation Protocol. The QoS policy exchange mechanism. See IETF Internet Draft: http://ietf.org/internet-drafts/draft-ietf-rap-cops-02.txt

● Custom Queuing (CQ)
See Class-based Queuing

● Differentiated Services (DiffServ)
An emerging Quality of Service standard. A superset of IP Precedence/CBQ. By utilizes an entire TOS byte in the IP header, it offers up to 256 levels of priority. This protocol is expected to be used predominanty in the IP backbone environments. See IETF Internet Draft: http://ietf.org/internet-drafts/draft-ietf-diffserv-arch-01.txt

● Edge Device
A device such as a router or a gateway that is deployed at the border of an administrative domain. Such devices control traffic through one point only. Contrast with End-to-End QoS.

● Ene-to-End QoS
A system that enforces consistent Quality of Service policies throughout a network. Has the ability to provide both class of service and reserved bandwidth for different types of network traffic. End-to-end QoS coordinates and enforces predefined traffic management policies across multiple network devices.

● Guaranteed Service
A service level that attempts to guarantee a minimal delay for traffic delivery. In the proposed IETF Integrated Service model, guaranteed service is intended for real-time applications, such as teleconferencing. The guarantee is not absolute, but such traffic is a level above controlled-load service. See also Controlled-load Service

● IEEE 802. 1p Standard
An IEEE standard that governs the prioritization of packets in the Ethernet and Token Ring networks. Offers eight discrete priority levels., ranging from the default of best effort, through excellent effort (a business-critical application, but tolerant of some delay), interactive multimedia (sensitive to delay or jitter), and reserved (highest priority). This is a Layer 2 (Data Link) priority setting, as opposed to the ToS and IP Precedence/CBQ bits, which are Layer 3 (Network Level) settings carried in the IPv4 header. Because it must be implemented in the hardware of network devices, existing switches and routers need to be replaced with ones supporting this technology. See also IP Precedence/CBQ, Type of Service.

● Integrated Services
The practice of supporting audio, video, and real-time data within a single network infrastructure. The IETF's Integrated Services (IntServ) working group has proposed a variety of QoS standards to support such systems. See also Controlled-load Service, Guaranteed Service. See IETC RFC 1633 http://info.internet.isi.edu/in-notes/rfc/files/rfc1633.txt and 2210 http://info.internet.isi.edu/in-notes/rfc/files/rfc2210.txt

● Internet Engineering Task Force (IETF)
The international organization that defines Internet protocols and standards, including refinements to improve QoS.

● Internet Service Provider (ISP)
A telecommunications company that provides dialup or leased-line connections to the Internet. Local and regional ISPs forward traffic to backbone ISPs, the large carrier-class ISPs that own the national and international Internet backbone infrastructure. Many ISPs offer additional services, such as Web site hosting, Voice over IP (VoIP), or virtual private networks (VPN).

● IP Performance Provisioning
A proactive, business-policy driven, IP traffic management solution that utilizes Policy Based Network Management (PBNM) technology to optimize network performance. IP Performance Provisioning simplifies network traffic management and complex configuration issues by automating labor intensive, error-prone configuration tasks, affecting many network devices with one policy rule.

● IPv4 (Internet Protocol)
The most widely deployed version of the Internet Protocol, IPv4 provides some basic traffic classification mechanisms with its IP Precedence/CBQ and Type of Service header fields. However, network hardware and software traditionally have not been configured to use them.

● IPv6 (Internet Protocol)
An update to the Internet Protocol that is in the early phases of adoption. Most of the refinements concentrate on basics such as expanding the IP address numbering scheme to accommodate the growth of the Internet. However, IPv6 does include a Class header field that is explicitly intended to designate a Class of Service (an extension of IPv4's IP Precedence/CBQ field).

● IP Multicast
A technique for making a single transmission fan out to multiple recipients. Instead of sending a copy of each packet to multiple destinations, the sender transmits one packet to a multicast group address. Specialized multicast systems then retransmit each packet to the individuals in the group. IP Multicast makes more efficient use of bandwidth by minimizing duplication, particularly in multipoint applications such as broadcast video traffic (e.g., distance learning).

● IP Precedence/CBQ
One of the key QoS transmission standards. A 3-bit value in the IP packet header meant to designate the relative priority of a packet. Offers eigth levels of priority from 0 to 7. For example, a brokerage firm might assign a higher IP Precedence/CBQ value to real-time stock trades than to e-mail to ensure that the trading gets expedited delivery. Same as TOS bits - see IETF RFC 1349 http://info.internet.isi.edu/in-notes/rfc/files/rfc1349.txt

● Jitter
A type of distortion that is caused by packets arriving at irregular intervals. This distortion is particularly damaging to multimedia traffic. For example, the playback of audio or video data may have a jittery or shaky quality.

● Layer 1
The Physical network layer in the Open Systems Interconnection model. Applies to basic wiring. Examples of Layer 1 protocols include 10BaseT, V.35, and AAL1.

● Layer 2
The Data Link layer in the Open Systems Interconnection model. Examples include Ethernet, Token Ring, and HDLC.

● Layer 3
The Network protocol layer in the Open Systems Interconnection model. Examples include IP and IPX.

● Leaky Bucket
A traffic-shaping mechanism in which only a fixed amount of traffic is admitted to the network. Excess traffic is held in a queue until either it can be accommodated or must be discarded. The analogy is with water flowing into a leaky bucket. If the water continues to flow in faster than it can leak out the bottom, the bucket eventually overflows. See also Token Bucket

● Lightweight Directory Access Protocol (LDAP)
A standard for repositories that store user profiles and other information about the network. LDAP repositories make it easier for users to find the e-mail addresses and public key encryption codes of other users. Currently, there is no stanadard governing storing the QoS policy information in the LDAP format. However, such suport is expected in the future. LDAP repositories are not capable of issuing dynamic policy authorizations and do not have policy enforcement capabilities.

● Over-provisioned Bandwidth
An expensive approach to addressing current limitations of "best effort" networks by provisioning more bandwidth than expected network peak requirements. over-provisioning increases the probability, but does not guarantee the quality, of transmission of time-sensitive and bandwidth-intensive applications.

● Peering Agreement
A reciprocal agreement that lets Internet Service Providers share backbone links, so traffic can reach destinations beyond the ISP's management domain.

● Point QoS
PointQoS offers proprietary hardware-based solutions that address traffic flow congestion on a single point in the network, usually at the network edge. Based on the negative principle of blocking and filtering specific data types or applications (e.g., PointCast), PointQoS introduces an extra point of failure, does not guarantee the quality of the data transmission across the entire data path, and does not address the needs of time-critical applications.

● Policy Administrator
A component of the Asce Networks NeuTrans suite. It is a centralized repository that maintains all QoS policies for the entire network. Automatically distributes up-to-date policy information to all Asce Networks NeuTrans Policy Servers and provides failover protection in the event a NeuTrans Policy Server stops functioning.

● Policy Server
A component of the Asce Networks NeuTrans Open Policy System. It is a server that authorizes QoS requests received from Common Open Policy Service-enabled routers or Policy Gateways and coordinates bandwidth usage on multiple network devices to ensure consistent end-to-end service throughout the data-path. The Policy Server ensures that packets receive the appropriate Quality of Service, based on a set of policies defined by the network administrator.

● Quality of Service (QoS)
Quality of Service is the network's ability to match user and application requirements to network capabilities. It is based on a set of intelligent network protocols and services used to efficiently control the movement of information through local or wide area networks. QoS software sorts and classifies IP packet requests into different traffic classes and allocates the proper resources to direct traffic based on various criteria including application type, user or application ID, source or destination IP address, time of day, and other user-specified variables.

● QoS Signalling
Any system for transmitting QoS requests and parameters between devices or applications. Resource ReSerVation Protocol is an example of a QoS signaling system.

● Queuing
A method for metering the flow of traffic by placing packets in holding queues, and retransmitting them according to a sorting algorithm, typically a simple first-in-first-out (FIFO) formula. Queues of different sizes can be used to assign levels of importance according to Class of Service designations. Queues that overflow typically discard packets to reduce network congestion.

● Random Early Detection (RED)
A basic congestion avoidance technique built on the base-level TCP behavior of automatically slowing transmissions when packet loss is detected. RED tries to anticipate congestion by monitoring a queue. When the specified threshold is reached, it randomly discards packets. This is an implicit signal that the originating applications should slow their transmissions before congestion becomes severe. See also Weighted Random Early Detection

● Resource ReSerVation Protocol (RSVP)
One of the key IETF protocols that communicates the QoS requirements for a given application to a device in the path of the transmission. A reservation for the required bandwidth is allowed or denied depending on the current network conditions. By itself, Resource ReSerVation Protocol provides a way to reserve capacity one device at a time. In a centrally managed QoS system, Resource ReSerVation Protocol can be implemented according to policies that apply across the network. Resource ReSerVation Protocol is expected to be utilized predominantly in the campus-level networks. See also Common Open Policy Service. See IETF RFC 2205 http://info.internet.isi.edu/in-notes/rfc/files/rfc2205.txt

● SLA (Service Level Agreement)
An agreement between a business or residential customer and a network service provider or between two independent service providers that specifies the minimum service levels that must be provided. Cooperative service level agreements can be written to ensure consistent handling of differentiated traffic flows across multiple network domains, allowing end-to-end quality of service for Internet traffic.

● TCP/IP (Transmission Control Protocol/Internet Protocol)
The standard protocol suite for the Internet and an increasing number of corporate networks. IP is the base network protocol (on which multiple transport protocols have been implemented) and TCP controls the behavior of packet transmission.

● TCP Rate Control
A technology implemented at network end points that attempts to regulate the introduction of traffic into the network.

● Token Bucket
A traffic-shaping mechanism in which a predetermined amount of tokens in a bucket represent the capacity allowed to each class of traffic. Packets are forwarded until they exhaust their supply of tokens. When the token supply is exhausted, packets may be discarded or delayed until the bucket is replenished. In some systems, a customer's token supply might correspond to a service fee. See also Leaky Bucket.

● Traffic Shaping
A group of techniques that attempt to regulate or meter the flow of packets through the network. See also Leaky Bucket, Token Bucket

● Type of Service (ToS)
A 4-bit value in an IP packet's message header that identifies the type of application generating a given traffic flow. Like the IP Precedence/CBQ field, the ToS value can be used for traffic classification. Functionally, TOS and IP Precedence/CBQ are identical.

● Virtual Private Network (VPN)
A way of duplicating the security and reliability of a dedicated network connection over a less expensive Internet link. This requires that each network participating in the VPN deploy a compatible firewall for encrypting messages and for permitting authorized access from remote locations. A combination of VPN and ThruQoS offers guaranteed quality and reliability of traffic flow and allows for the migration of customers from dedicated lines to shared IP infrastructure.

● Voice over IP (VoIP)
An emerging technology for carrying phone conversations over the Internet and intranets. VoIP is sometimes provided as part of a package with other collaborative applications, such as text-based chat. ThruQoS is important for VoIP because the audio signal must come through in a steady stream, just as it would over a traditional telephone switch.

● Weighted Fair Queuing (WFQ)
A methodology for segmenting traffic into multiple queues, giving greater weight to certain traffic types by assigning larger queues. Like class-based queuing (CBQ), WFQ is designed to prevent any one traffic type from entirely eclipsing another. By default, WFQ favors lower-volume traffic flows over higher-volume ones (for example, a routine e-mail over a large FTP download). See also Class-based Queuing.

● Weighted Random Early Detection (WRED)
A congestion avoidance technique that takes advantage of TCP's interpretation of packet loss as a sign to slow transmissions. WRED monitors a queue until it fills to a specified threshold. It then begins discarding packets, starting with those that have the lowest IP Precedence/CBQ. See also Random Early Detection.

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