copyright: ipv6@bits rsvp the reservation protocol by sujay koduri

copyright: IPv6@BITScopyright: IPv6@BITS

RSVPRSVP

The ReSerVation ProtocolThe ReSerVation Protocol

byby

Sujay koduriSujay koduri


RSVP, Is it required?RSVP, Is it required?

QOS Requirements??QOS Requirements?? Real-time applicationsReal-time applications

Interactive applications are sensitive Interactive applications are sensitive to packet delays (telephone)to packet delays (telephone)

Non-interactive applications can adapt Non-interactive applications can adapt to a wider range of packet delays to a wider range of packet delays (audio, video broadcasts)(audio, video broadcasts)

Guarantee of maximum delay is usefulGuarantee of maximum delay is useful


QOS Required??QOS Required??

What is the problem?What is the problem? Different applications have different Different applications have different

delay, bandwidth, and jitter needsdelay, bandwidth, and jitter needs Some applications are very sensitive to Some applications are very sensitive to

changing network conditions: the packet changing network conditions: the packet arrival time distribution is importantarrival time distribution is important

SolutionsSolutions Make applications adaptiveMake applications adaptive Build more flexibility into networkBuild more flexibility into network


What is RSVP?What is RSVP?

Protocol that guarantees QoS Protocol that guarantees QoS It reserves resources in the internet It reserves resources in the internet

(resources include BW and router (resources include BW and router buffers)buffers)

Can also be used by routers to Can also be used by routers to forward BW reservation requestsforward BW reservation requests


DefinitionDefinition

RSVP: It is a network control protocol that RSVP: It is a network control protocol that allows data receiver to request a special end allows data receiver to request a special end to end quality of service for its data flows.to end quality of service for its data flows.

Although it sits on top of the IP protocol Although it sits on top of the IP protocol stack, it is stack, it is not a routing protocolnot a routing protocol

It is rather an internet control protocolIt is rather an internet control protocol It is designed to operate with current and It is designed to operate with current and

future unicast and multicast routing future unicast and multicast routing protocolsprotocols


Principal characteristicsPrincipal characteristics

Reservations for BWs in multicast Reservations for BWs in multicast treestrees

Unicast is handled as a degenerate Unicast is handled as a degenerate case of multicastcase of multicast

It is receiver oriented ie… receiver of It is receiver oriented ie… receiver of data initiates the processdata initiates the process


sessionsession

Similar to RTP here also session Similar to RTP here also session consists of multiple multicast data consists of multiple multicast data flowsflows

Each sender is a source of one or Each sender is a source of one or more data flowsmore data flows

Each data flow in a session has a Each data flow in a session has a same multicast addresssame multicast address


What RSVP is not?What RSVP is not?

It does not specify how the network It does not specify how the network provide the reserved BW to the data flowsprovide the reserved BW to the data flows

Routers will actually provide the reserved Routers will actually provide the reserved BW (via priority scheduling etc).BW (via priority scheduling etc).

It is not a routing protocol (it does not It is not a routing protocol (it does not determine the links)determine the links)

Also referred as signaling protocol.Also referred as signaling protocol.


Heterogeneous receiversHeterogeneous receivers

Some receivers can receive at 30 Some receivers can receive at 30 Kbps others at 128 Kbps and others Kbps others at 128 Kbps and others at 10Mbpsat 10Mbps

Suppose if a sender is multicasting a Suppose if a sender is multicasting a video to a group of heterogeneous video to a group of heterogeneous receivers ,should the sender encode receivers ,should the sender encode the video for 30,128Kbps or 10Mbps?the video for 30,128Kbps or 10Mbps?


solutionsolution

Layered encoding is often suggested Layered encoding is often suggested Sender need not know the receiving Sender need not know the receiving

rates of all the receiversrates of all the receivers Only need to know the maximum Only need to know the maximum

speed of the receiversspeed of the receivers RSVP mainly deals with the RSVP mainly deals with the

heterogeneous receiversheterogeneous receivers


Reservation MergingReservation Merging

Receiver#1

Receiver#2

Receiver#3

Reservations mergeas they travel up tree.

R6

R3

R1

R4 R7

(1) 50Kbs

(2) 50Kbs

(3) 50Kbs

(4) 100 Kbs

(5) 100 Kbs

(6) 100 Kbs

(7) 100 Kbs

(8) 60Kbs

(9) 60Kbs


Call admissionCall admission

BW reserved by the router should not BW reserved by the router should not exceed the links capacityexceed the links capacity

So a router first determines its down So a router first determines its down stream links can accommodate the stream links can accommodate the reservation or not.reservation or not.

RSVP do not define this admission RSVP do not define this admission tests.tests.


Local decision modulesLocal decision modules

Admission controlAdmission control Policy controlPolicy control

Proceeded only when these two are Proceeded only when these two are verifiedverified

If either check fails RSVP will return an If either check fails RSVP will return an error.error.


Soft stateSoft state

There is a timer associated with There is a timer associated with every reservation of BW stored in a every reservation of BW stored in a routerrouter

It should be periodically refreshed.It should be periodically refreshed. Same principle is used for routing Same principle is used for routing

tables where the entries are tables where the entries are refreshed by newly arriving data refreshed by newly arriving data packetspackets


Reservation stylesReservation styles

1.1.Wildcard Filter Wildcard Filter (WF) Style: It creates a single (WF) Style: It creates a single reservation shared by flows from all upstream reservation shared by flows from all upstream senders WF(*(Q))senders WF(*(Q))*- represents the wildcard sender selection*- represents the wildcard sender selectionQ-flow specQ-flow spec2. 2. Fixed Filter Fixed Filter (FF): It creates a distinct reservation (FF): It creates a distinct reservation for data packets from a particular sender. FF(S(Q))for data packets from a particular sender. FF(S(Q))3. 3. Shared Explicit Shared Explicit (SE): It creates a single (SE): It creates a single reservation shared by selected upstream reservation shared by selected upstream senders.SE((S1,S2,..)(Q)) senders.SE((S1,S2,..)(Q))


RSVP Protocol MechanismsRSVP Protocol Mechanisms

Router

CA

D

D’

B

B’


Describing and Identifying a Describing and Identifying a FlowFlow

Flow spec defines traffic parametersFlow spec defines traffic parameters Traffic parameters: bandwidth, buffering Traffic parameters: bandwidth, buffering

requirementsrequirements Uses token bucket specificationUses token bucket specification

Filter spec identifies packets in flowFilter spec identifies packets in flow Simplest filter: Source, Dest address/port Simplest filter: Source, Dest address/port

pairpair Data filter: classifies packets according to Data filter: classifies packets according to

contentscontents


Resource ReservationResource Reservation

Senders advertise using PATH Senders advertise using PATH messagemessage

Receivers reserve using RESV Receivers reserve using RESV messagemessage Flowspec + filterspec + policy dataFlowspec + filterspec + policy data Travels upstream in reverse direction of Travels upstream in reverse direction of

Path messagePath message Sender/receiver notified of changesSender/receiver notified of changes


Components of pathComponents of path

Each Path message contains the following Each Path message contains the following information:information:1.Sender Template: Describes the format of data 1.Sender Template: Describes the format of data packets that the sender will originate.packets that the sender will originate.2.Sender T- spec: Defines the traffic characteristics of 2.Sender T- spec: Defines the traffic characteristics of the data flow.the data flow.3.Adspec: Used for OPWA (One Pass with 3.Adspec: Used for OPWA (One Pass with Advertisement)Advertisement)

With this scheme, RSVP control packets are sent With this scheme, RSVP control packets are sent downstream , flowing the data paths to gather downstream , flowing the data paths to gather information that can be used to predict the end to end information that can be used to predict the end to end QoS.QoS.


Killer reservation problemKiller reservation problem

It arises when already there is a Q0 in It arises when already there is a Q0 in place and if another receiver makes a place and if another receiver makes a larger Q1>Q0, the result of merging may larger Q1>Q0, the result of merging may be rejected by some intermediate node.be rejected by some intermediate node.

Blockade StateBlockade State: A blocked state in a node : A blocked state in a node modifies the merging process to omit the modifies the merging process to omit the offending flowspec.offending flowspec.


Functional Specifications…Functional Specifications…1.1.VersVers: Usually 1.: Usually 1.2. 2. FlagsFlags: 4 bits 0x01-0x08:Reserved.: 4 bits 0x01-0x08:Reserved.3. 3. Msg TypeMsg Type:8 bits:8 bits 1=Path 1=Path 2= Resv and so on. 2= Resv and so on.4. 4. RSVP ChecksumRSVP Checksum:16 bits:16 bits5. 5. Send_TTLSend_TTL:IP TTL value with which :IP TTL value with which the message was sent.the message was sent.6. 6. RSVP LengthRSVP Length: 16 bits- includes the : 16 bits- includes the common header and variable length common header and variable length objects that follow.objects that follow.


•Objects:Objects:

---------------------------------------------------- ---------------------------------------------------- Length (bytes) | Class-Num | C-Type Length (bytes) | Class-Num | C-Type ---------------------------------------------------- ---------------------------------------------------- // (Object contents) // // (Object contents) // ---------------------------------------------------- ----------------------------------------------------


•Objects…Objects…1. 1. LengthLength: 16 bit containing the total : 16 bit containing the total length in bytes.length in bytes.2. 2. Class-NumClass-Num:Identifies the object :Identifies the object class.class.3. 3. C-TypeC-Type: Object type , unique : Object type , unique within each object class.within each object class.The maximum object content length The maximum object content length is 65528 bytes. The Class-Num and is 65528 bytes. The Class-Num and the C-Type fields may be used the C-Type fields may be used together as a 16 bit number to together as a 16 bit number to define a unique type for each object.define a unique type for each object.


RSVP routing problemsRSVP routing problems

If route changes, reservation must be If route changes, reservation must be made along new routemade along new route New reservation takes time to setupNew reservation takes time to setup New reservation might failNew reservation might fail Old route could still be working fineOld route could still be working fine

Reservation failureReservation failure Primary route has inadequate Primary route has inadequate

bandwidth although secondary has bandwidth although secondary has enoughenough

copyright: ipv6@bits rsvp the reservation protocol by sujay koduri

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