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Information about Traffic Shaping

Traffic shaping (also known as "packet shaping") is an attempt to control computer network traffic in order to optimize or guarantee performance, low latency, and/or bandwidth by delaying packets.[1] Traffic shaping deals with concepts of classification, queue disciplines, enforcing policies, congestion management, quality of service (QoS), and fairness.

Summary

Traffic shaping provides a mechanism to control the volume of traffic being sent into a network (bandwidth throttling), and the rate at which the traffic is being sent (rate limiting). For this reason, traffic shaping schemes are commonly implemented at the network edges to control traffic entering the network. This control can be accomplished in many ways and for many reasons but traffic shaping always simply consists in delaying packets. Traffic policing is the related practice of packet dropping and packet marking. Traffic shaping can be applied by the traffic source (for example, computer or network card) or by an element in the network.

Implementation

A traffic shaper works by delaying metered traffic such that each packet complies with the relevant traffic contract. Metering may be implemented with for example the leaky bucket or token bucket algorithms (the former typically in ATM and the latter in IP networks). Metered packets or cells are then stored in a buffer until they can be transmitted in compliance with the prevailing traffic contract. This may occur immediately (if the traffic arriving at the shaper is already compliant), after some delay (waiting in the buffer until its scheduled release time) or never (in case of buffer overflow).

Overflow Condition

All traffic shaper implementations have a finite buffer, and must cope with the case where the buffer is full . A simple and common approach is to drop traffic arriving while the buffer is full (tail drop), thus resulting in traffic policing as well as shaping. A more sophisticated implementation could apply a dropping algorithm such as Random Early Discard; a crude alternative would be to allow overflowing traffic through unshaped.

Traffic Classification

Simple traffic shaping schemes shape all traffic uniformly by rate. More sophisticated shapers first classify traffic. 'Traffic classification categorises traffic (for example, based on port number or protocol number); each resulting traffic class can be treated differently to differentiate service. For example, each traffic class could be subject to a different rate limit, shaped separately and/or prioritised relative to other traffic classes. This differentiation can be used by a network operator to treat different types of application traffic differently (for example, prioritise voice over file sharing), and to offer premium services at a higher price point than basic ones[2].

Classification is achieved by various means. Matching bit patterns of data to those of known protocols is a simple, yet widely-used technique. An example to match the BitTorrent Protocol Handshaking phase would be a simple check to see if a packet began with character 19 which was then followed by the 19-byte string 'BitTorrent protocol'.[3] Upon classifying a traffic flow using a particular protocol, a policy can be applied to it and other flows to either guarantee a certain quality (as with VoIP or media streaming service[4]) or to provide best-effort delivery. This may be applied at the ingress point (the point at which traffic enters the network) with a granularity that allows the traffic-shaping control mechanism to separate traffic into individual flows and shape them differently [5].

Relationship to Traffic Management

Traffic shaping is a specific technique and one of several which combined comprise Traffic Management[6]. Current common usage, particularly in discussion of domestic Internet service provision, frequently confuses traffic shaping with traffic management and traffic policing, with classification policies and in general with any measure deliberately taken by an ISP which is detrimental to the user's IP traffic performance.

ISPs

Traffic shaping is of interest especially to Internet Service Providers (ISPs). Their high-cost, high-traffic networks are their major assets, and as such, are the focus of all their attentions. They often use traffic shaping as a method to optimize the use of their network, sometimes by intelligently shaping traffic according to importance, other times by discouraging uses of applications by harsh means.

Benefits

To ISPs, mere protocol identification (a large part of modern traffic shaping mechanisms) gives the intangible yet significant benefit of seeing what internet traffic is flowing through the network. From this they can see which subscribers are doing what on their network and can target services to the subscriber base they have attracted.

In addition, intelligent shaping schemes can guarantee a particular Quality of Service (often measured in jitter, packet loss, and latency) for an application or a user while still allowing other traffic to use all remaining bandwidth. This allows ISPs to offer Differentiated services and to upsell existing services to subscribers (such as offering minimum-latency computer gaming for an additional fee on top of basic internet).

Three Types of Traffic

Internet traffic as viewed by ISPs can be thought of as placed into three categories: Sensitive, Best-Effort, and Undesired.

Sensitive Traffic

Sensitive traffic is traffic whose Quality of Service ISPs care about. This usually includes VoIP, online gaming, video streaming, and web surfing, but basically any application or protocol could fall under this umbrella. Shaping schemes are generally tailored in such a way that the Quality of Service of these selected uses is guaranteed, or at least prioritized over other classes of traffic. This can be accomplished by the absence of shaping schemes on these, or by positive shaping (prioritization over others).

Best-Effort Traffic

Best effort traffic is all other kinds of non-detrimental traffic. This is traffic that is either not sensitive to Quality of Service metrics (jitter, packet loss, latency) or traffic that is, and the ISP is not concerned about its Quality of Service. A typical example of the former would be peer-to-peer traffic, the latter: online gaming (though there are exceptions such as [1]). Shaping schemes are generally tailored in such a way that this traffic gets 'what is left' of the bandwidth after sensitive traffic has 'taken its share'.

Undesired Traffic

This category is generally limited to the delivery of spam and traffic created by worms, botnets, and other malicious attacks. In some countries (for example, China), this definition can (and does) expand to such traffic as non-local VoIP (Skype) or video streaming services, which are squelched to create a market for the 'in-house' services of the same type. Shaping schemes usually involve identifying and blocking this traffic entirely, or just by severely hampering its operation. Rogers Communications in Canada has been accused of applying this type of shaping to peer-to-peer traffic in violation of Canadian Radio-television and Telecommunications Commission (CRTC) regulations.[7]

Peer-To-Peer

Peer-to-peer (P2P) traffic is particularly troublesome for traffic shaping efforts for ISPs because it is designed to use any and all available bandwidth which impacts QoS-sensitive applications (like online gaming) that use comparatively small amounts of bandwidth. Most, if not all, popular P2P applications are location-agnostic (they care not/little if they download from a user halfway around the world or one next door) makes them even more problematic, as traffic outside of a network, which is the more expensive kind, will increase.

This has given P2P a bad reputation with internet service providers trying to roll out quality-dependent services (again, like VoIP). Some may even view P2P as an 'attack' on their networks.

However, P2P is often listed as the reason subscribers choose broadband internet. Recent figures show that the usage of one-fifth of the highest-usage subscribers must be added together to make up only close to 80% of P2P traffic on ISP networks. [2] Sandvine Incorporated has determined through traffic analysis that P2P traffic accounts for up to 60% of traffic on most networks.[8] This shows, in contrast to previous studies and forecasts, that P2P has become more mainstream than a handful of P2P users on the network.

These figures have influenced service providers to consider subscriber experience when implementing traffic shaping. If P2P is being used by more than the top fifth of an ISP's subscriber base, a harsh anti-P2P policy may have disastrous consequences on subscriber numbers, increasing the subscriber Churn rate. In some extreme cases (like that of Rogers Communications and ihaterogers.ca) this may damage the ISPs reputation permanently.

P2P protocols are designed specifically to avoid being identified and with enough robustness that it is agnostic to standard QoS metrics (out-of-order packets (jitter) just increase buffering, packet loss and latency just increase the download time) means that it is best classified as Best-Effort traffic. At peak times when sensitive traffic is at its height, download speeds will decrease. However, since P2P downloads are often background activities, it affects the subscriber experience little, so long as the download speeds increase to their full potential when all other subscribers hang up their VoIP phones.

Enterprises

Traffic Shaping and Prioritization is becoming more and more common in the corporate market. Most companies with remote offices are now connected via a WAN (Wide Area Network). Applications tend to become centrally hosted at the head office and remote offices are expected to pull data from central databases and server farms. As applications become more hungry in terms of bandwidth and prices of dedicated circuits being relatively high in most areas of the world, instead of increasing the size of their WAN circuits, companies feel the need to properly manage their circuits to make sure business-oriented traffic gets priority over best-effort traffic. Traffic shaping is thus a good means for companies to avoid purchasing additional bandwidth while properly managing these resources.

Other upcoming technologies to this regards are Application Acceleration and WAN Optimization and Compression which are fundamentally different from Traffic Shaping. Traffic Shaping defines bandwidth rules (or [https://packeteer.custhelp.com/cgi-bin/packeteer.cfg/php/enduser/std_adp.php?p_faqid=60&p_created=984707874&p_sid=-nyQb5Ai&p_accessibility=0&p_redirect=&p_lva=&p_sp=cF9zcmNoPTEmcF9zb3J0X2J5PWRmbHQmcF9ncmlkc29ydD0mcF9yb3dfY250PTEzNSZwX3Byb2RzPTAmcF9jYXRzPSZwX3B2PSZwX2N2PSZwX3NlYXJjaF90eXBlPWFuc3dlcnMuc2VhcmNoX2ZubCZwX3BhZ2U9MSZwX3NlYXJjaF90ZXh0PXBhcnRpdGlvbg**&p_li=&p_topview=1 partitions] as some vendors call them) whereas Application Acceleration using multiple techniques like TCP Performance Enhancing Proxy. WAN Optimization and Compression (WOC) on the other hand would use compression and differential algorithms and techniques to compress data streams or send only differences in file updates. The latter is quite effective for chatty protocols like CIFS.

Uses

Traffic shaping is often used in combination with:

See also

Companies With Products Employing Traffic Shaping

Major Internet Service Providers Using Traffic Shaping

References

1. ^ IETF RFC 2475 "An Architecture for Differentiated Services" section 2.3.3.3 - definition of "Shaper"
2. ^ PlusNet's Traffic Classes show classification and prioritisation policies used to differentiate between more and less expensive Internet service
3. ^ BitTorrent Protocol
4. ^ SIN 450 Issue 1.2 May 2007 Suppliers' Information Note For The BT Network BT Wholesale - BT IPstream Advanced Services - End User Speed Control and Downstream Quality of Service - Service Description
5. ^ Ferguson P., Huston G., Quality of Service: Delivering QoS on the Internet and in Corporate Networks, John Wiley & Sons, Inc., 1998. ISBN 0-471-24358-2.
6. ^ ATM Forum Traffic Management Specification, Version 4.0 Approved Specification 0056.00, Section 5.5, Traffic Shaping
7. ^ Geist, Michael. The Unintended Consequences of Rogers' Packet Shaping.
8. ^ Leydon, John. P2P swamps broadband networks.
  • "Deploying IP and MPLS QoS for Multiservice Networks: Theory and Practice" by John Evans, Clarence Filsfils (Morgan Kaufmann, 2007, ISBN 0-12-370549-5)
  • "Peer-to-Peer File Sharing: The Impact of File Sharing on Service Provider Networks", Sandvine Incorporated, copyright 2002

External links

as a college campus, industrial complex, or a military base. A CAN, may be considered a type of MAN (metropolitan area network), but is generally limited to an area that is smaller than a typical MAN.
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Bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a filter, a communication channel, or a signal spectrum, and is typically measured in hertz.
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Quality of Service, abbreviated QoS, refers to resource reservation control mechanisms. Quality of Service can provide different priority to different users or data flows, or guarantee a certain level of performance to a data flow in accordance with requests from the
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as a college campus, industrial complex, or a military base. A CAN, may be considered a type of MAN (metropolitan area network), but is generally limited to an area that is smaller than a typical MAN.
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Bandwidth throttling is a method of ensuring a bandwidth intensive device, such as a server, will limit ("throttle") the quantity of data it transmits and/or accepts within a specified period of time.
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In computer networks, rate limiting is used to control the rate of traffic sent or received on a network interface. Traffic that is less than or equal to the specified rate is sent, whereas traffic that exceeds the rate is dropped or delayed.
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Traffic policing is monitoring network traffic for conformity with a traffic contract and if required, dropping traffic to enforce compliance with that contract. Traffic sources which are aware of a traffic contract sometimes apply Traffic Shaping in order to ensure their output
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Network Card

A 1990s Ethernet network interface controller card which connects to the motherboard via the now-obsolete ISA bus.

Connects to:
  • Motherboard via one of

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traffic contract.

The Traffic descriptor

When a connection is requested by an application, the application indicates to the network[2]:
  • The Type of Service required
  • The Traffic Parameters of each data flow in both directions

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Although the leaky bucket algorithm has several uses, it is best understood in the context of network traffic shaping or rate limiting. Typically, the algorithm is used to control the rate at which data is injected into a network, smoothing out "burstiness" in the data rate.
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Although the token bucket algorithm has several uses, it is best understood in the context of network traffic shaping or rate limiting. Typically, the algorithm is used to control the amount of data that is injected into a network, allowing for "bursts" of data to be sent.
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Asynchronous Transfer Mode (ATM) is a cell relay, packet switching network and data link layer protocol which encodes data traffic into small (53 bytes; 48 bytes of data and 5 bytes of header information) fixed-sized cells.
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Internet protocol may refer to:
  • The Internet Protocol, a data-oriented protocol used for communicating data across a packet-switched internetwork
  • The Internet protocol suite, a set of communications protocols that implement the protocol stack on which the Internet runs

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Buffer can refer to:
  • Buffer state, a country lying between two potentially hostile greater powers, thought to prevent conflict between them
  • Buffer zone, any area that keeps two or more other areas distant from one another, may be demilitarized

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Random early detection (RED), also known as random early discard or random early drop is an active queue management algorithm. It is also a congestion avoidance algorithm.
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TCP and UDP are transport protocols used for communication between computers. The IANA is responsible for assigning port numbers to specific uses.

Ranges

The port numbers are divided into three ranges.
  • The Well Known Ports are those in the range 0–1023.

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BitTorrent is a peer-to-peer file sharing (P2P) communications protocol. BitTorrent is a method of distributing large amounts of data widely without the original distributor incurring the entire costs of hardware, hosting and bandwidth resources.
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handshake is a short ritual in which two people grasp their right or left hands, often accompanied by a brief shake of the grasped hands.

The handshake is initiated when the two hands touch, immediately.
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Voice over Internet Protocol, also called VoIP, IP Telephony, Internet telephony, Broadband telephony, Broadband Phone and Voice over Broadband is the routing of voice conversations over the Internet or through any other IP-based network.
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In computer networking, bandwidth management is the process of measuring and controlling the communications (traffic, packets) on a network link, to avoid filling the link to capacity or overfilling the link, which would result in network congestion and poor performance.
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Internet service provider (abbr. ISP, also called Internet access provider or IAP) is a business or organization that provides consumers or businesses access to the Internet and related services. In the past, most ISPs were run by the phone companies.
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Jitter is an unwanted variation of one or more signal characteristics in electronics and telecommunications. Jitter may be seen in characteristics such as the interval between successive pulses, or the amplitude, frequency, or phase of successive cycles.
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Packet loss occurs when one or more packets of data traveling across a computer network fail to reach their destination.

Causes

Packet loss can be caused by a number of factors, including signal degradation over the network medium, oversaturated network links, corrupted
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Latency is a time delay between the moment something is initiated, and the moment one of its effects begins or becomes detectable. The word derives from the fact that during the period of latency the effects of an action are latent, meaning "potential" or "not yet observed".
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DiffServ or Differentiated Services is a computer networking architecture that specifies a simple, scalable and coarse-grained mechanism for classifying, managing network traffic and providing quality of service (QoS) guarantees on modern IP networks.
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peer-to-peer (or "P2P") computer network exploits diverse connectivity between participants in a network and the cumulative bandwidth of network participants rather than conventional centralized resources where a relatively low number of servers provide the core value to a
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This page contains Chinese text.
Without proper rendering support, you may see question marks, boxes, or other symbols instead of Chinese characters.
China (Traditional Chinese:
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Maintainer: Skype Limited

OS: Cross-platform

Use: P2P/VoIP/instant messaging/
video call/videophone
License: Freeware (with some non-free features)
Website: www.skype.
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Rogers Communications Inc.

Public (TSX:  RCI.A , TSX:  RCI.B , NYSE:  RCI )
Founded Toronto, Ontario (1920)
Headquarters Rogers Building, Toronto, Ontario

Key people Ted Rogers - President & CEO
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This page is currently protected from editing until disputes have been resolved.
Protection is not an endorsement of the current [ version] ([ protection log]).
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