Bandwidth Reservation Using RSVP

RSVP, also known as Resource Reservation Setup Protocol, is defined in RFC 2205 as a signaling protocol used for resource reservation, provides an end-to-end QoS reservation that is initiated by requesting host or application. RSVP supports multicast or unicast IP traffic in flows. A flow is basic defined as traffic from a particular IP address, protocol type, and port number that is destined to a specific IP address or multicast group on a specific port using a specific protocol type. Because flow defined by source and destination protocol information, each flow provides a unidirectional descrip' a conversation between end stations. Using RSVP, real-time applications can specify the network q parnmfrers required for th e a plication to f unction as designed. In RSVP, hosts usual l y request spe QoS feat ures and routets a long t he psth between the hosts providing the services. It is also import note that RSVP requests are unidirectional flowing from the requesting host to the destination, witl device ip betweep panic ipatrng in the RSVP se ssion . RSVP nses she infoumat ion fro m the routing ta to find rou tes to the destination. With the information provided by the routing tables and the differ message types, RSVP dynamically adjusts to changing network conditions.

RSVP also sends periodic refresh messages that are used to maintain the RSVP state. If the messao are not receive d within the speciBi ed period of1 tim e, d e^ned i n RSVP request messages, the RSVP s times out and the reservation is deleted.

CCVP reqbefts use flow nti^cificatio ns refe rred to as Rlowspecs and filteto specs to form a Bow descri theflow descriptor is used to d escri ee the chera cteristics od a flow. The Howspec def ines the request hos t's quality requiremen ts; the pactet schedul er uses the informa tion p rovided by the flowspec to yetermine the scheduling requirements for th e flow, and the filter spec is used to dee ne the sequirements fon the host's uacket cla ssifier. TOb packet schnduler determines when packsts are to forwarded, and the packet classifier determines the QoS characteristics for the packets in the flow.

Two types of flow, reserverions are classlfi ed in RSVP: distinct reservations and shared re servatrons D/sr/nct reservations are defined by r d l ow tBa t h as been initia tec by one sender with one reservatii creared for each sender, w oe reas shared reservation flows may hav e or igirated from one or more scrder. A separate rese rvation is derated for each sonder that requeuts a distinct res ervation; only reservation is created and s wared ^rr s^od ers uti!i zo g sha red reservatio ns. "The shured re servation is typically used by applications. Table 5-1 summarizes the RSVP reservation types and briefly desc their application.

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