- Integrated services
computer networking, IntServ or integrated services is an architecture that specifies the elements to guarantee quality of service(QoS) on networks. IntServ can for example be used to allow video and sound to reach the receiver without interruption.
IntServ specifies a fine-grained QoS system, which is often contrasted with DiffServ's coarse-grained control system.
The idea of IntServ is that every
routerin the system implements IntServ, and every application that requires some kind of guarantees has to make an individual reservation. "Flow Specs" describe what the reservation is for, while "RSVP" is the underlying mechanism to signal it across the network.
There are two parts to a flow spec:
* What does the traffic look like? Done in the Traffic SPECification or TSPEC part.
* What guarantees does it need? Done in the service Request SPECification or RSPEC part.
token bucketalgorithm parameters. The idea is that there is a token bucketwhich slowly fills up with tokens, arriving at a constant rate. Every packet which is sent requires a token, and if there are no tokens, then it cannot be sent. Thus, the rate at which tokens arrive dictates the average rate of traffic flow, while the depth of the bucket dictates how 'bursty' the traffic is allowed to be.
TSPECs typically just specify the token rate and the bucket depth. For example, a video with a refresh rate of 75 frames per second, with each frame taking 10 packets, might specify a token rate of 750Hz, and a bucket depth of only 10. The bucket depth would be sufficient to accommodate the 'burst' associated with sending an entire frame all at once. On the other hand, a conversation would need a lower token rate, but a much higher bucket depth. This is because there are often pauses in conversations, so they can make do with less tokens by not sending the gaps between words and sentences. However, this means the bucket depth needs to be increased to compensate for the traffic being burstier.
RSPECs specify what requirements there are for the flow: it can be normal internet 'best effort', in which case no reservation is needed. This setting is likely to be used for webpages, FTP, and similar applications. The 'Controlled Load' setting mirrors the performance of a lightly loaded network: there may be occasional glitches when two people access the same resource by chance, but generally both delay and drop rate are fairly constant at the desired rate. This setting is likely to be used by soft QoS applications. The 'Guaranteed' setting gives an absolutely bounded service, where the delay is promised to never go above a desired amount, and packets never dropped, provided the traffic stays within spec.
The Resource ReSerVation Protocol (RSVP) is described in RFC 2205. All machines on the network capable of sending QoS data send a PATH message every 30 seconds, which spreads out through the networks. Those who want to listen to them send a corresponding RESV (short for "Reserve") message which then traces the path backwards to the sender. The RESV message contains the flow specs.
The routers between the sender and listener have to decide if they can support the reservation being requested, and, if they cannot, they send a reject message to let the listener know about it. Otherwise, once they accept the reservation they have to carry the traffic.
The routers then store the nature of the flow, and also police it. This is all done in soft state, so if nothing is heard for a certain length of time, then the reader will time out and the reservation will be cancelled. This solves the problem if either the sender or the receiver crash or are shut down incorrectly without first cancelling the reservation. The individual routers may, at their option, police the traffic to check that it conforms to the flow specs.
The problem with IntServ is that many states must be stored in each router. As a result, IntServ works on a small-scale, but as you scale up to a system the size of the Internet, it is difficult to keep track of all of the reservations. As a result, IntServ is not very popular.
One way to solve this problem is by using a multi-level approach, where per-microflow resource reservation (i.e. resource reservation for individual users) is done in the edge network, while in the core network resources are reserved for aggregate flows only. The routers that lie between these different levels must adjust the amount of aggregate bandwidth reserved from the core network so that the reservation requests for individual flows from the edge network can be better satisfied. See RFC 3175.
* "Deploying IP and MPLS QoS for Multiservice Networks: Theory and Practice" by John Evans, Clarence Filsfils (Morgan Kaufmann, 2007, ISBN 0-12-370549-5)
* RFC 1633 - Integrated Services in the Internet Architecture: an Overview
* RFC 2211 - Specification of the Controlled-Load Network Element Service
* RFC 2212 - Specification of Guaranteed Quality of Service
* RFC 2215 - General Characterization Parameters for Integrated Service Network Elements
* RFC 2205 - Resource ReSerVation Protocol (RSVP)
* Cisco Whitepaper about IntServ and DiffServ - http://www.cisco.com/en/US/products/ps6610/products_white_paper09186a00800a3e2f.shtml
Wikimedia Foundation. 2010.
Look at other dictionaries:
Integrated Services Digital Network — ➔ ISDN * * * ► See ISDN … Financial and business terms
Integrated Services Digital Broadcasting — [ˈɪntɪɡɹeɪtɪd ˈsɜːvɪsɪz ˈdɪdʒɪtəl ˈbɹɔːdkɑːst] (ISDB) ist ein auf MPEG 2 basierender Standard für digitale Medienübertragung. Er wurde 1999 in Tokio eingeführt und sieht die Verbreitung von HDTV, SDTV, Audio und Text vor. ISDB erlaubt mehrere… … Deutsch Wikipedia
Integrated Services Digital Network — Integrated Services Digital Network, ISDN … Universal-Lexikon
integrated services digital network — see ↑ISDN • • • Main Entry: ↑integrate … Useful english dictionary
Integrated Services Digital Network — ISDN redirects here. For other uses, see ISDN (disambiguation). Integrated Services Digital Network (ISDN) is a set of communications standards for simultaneous digital transmission of voice, video, data, and other network services over the… … Wikipedia
Integrated Services Digital Network — Réseau numérique à intégration de services Suite de protocoles RNIS Couche Protocoles Canal D Protocoles Canal B Signali sation Paquet Télémétrie Commut. Circuit Semi Permanent Commut. paquet Ap … Wikipédia en Français
Integrated Services Digital Network — ISDN Telefon Integrated Services Digital Network (ISDN) ist ein internationaler Standard für ein digitales Telekommunikationsnetz und lässt sich sinngemäß als diensteintegrierendes digitales Netz übersetzen. Über dieses Netz werden verschiedene… … Deutsch Wikipedia
Integrated Services Architecture — Abbreviated ISA. A proposed extension to the Internet standards that would provide integrated services in support of real time applications over the Internet. Using current standards, real time applications do not work well over the… … Dictionary of networking
Integrated Services Digital Network — Abbreviated ISDN. A standard for a worldwide digital communications network originally designed to replace all current systems with a completely digital, synchronous, fullduplex transmission system. Computers and other devices connect to ISDN… … Dictionary of networking
integrated services digital network — skaitmeninis visuminių paslaugų tinklas statusas T sritis informatika apibrėžtis Skaitmeninis tinklas, kuriuo didele sparta (iki 128 Kb/s) persiunčiama tekstinė, vaizdinė, garsinė ir kitokia informacija panaudojant įprastas telefono linijas.… … Enciklopedinis kompiuterijos žodynas