國立清華大學資訊系黃能富教授 1 resource reservation protocol (rsvp) all rights...

國立清華大學資訊系黃能富教授 1

Resource ReSerVation Protocol

(RSVP)

All rights reserved. No part of this publication and file may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior written permission of Professor Nen-Fu Huang (E-mail: [email protected]).

國立清華大學資訊工程學系黃能富教授Tel: 03-573-1063Fax: 03-572-3694E-mail: [email protected]:http://www.cs.nthu.edu.tw/~nfhuang


RSVP Documents

RFC 2205 Resource ReSerVation Protocol (RSVP) -- Functional Specification

RFC 2209 Resource ReSerVation Protocol (RSVP) -- Message Processing Rules

RFC 2210 The Use of RSVP with IETF Integrated ServicesRFC 2211 Specification of Controlled-Load Network Eleme

nt ServiceRFC 2212 Specification of Guaranteed Quality ServiceRFC 2215 General Characterization Parameter for Integrat

ed Service Network ElementsRFC 2216 Network Element Service Specification Template


Introduction of RSVP

RSVP makes resource reservations for both unicast and multicast applications, adapting dynamically to changing group membership and routes.

A resource reservation setup protocol designed for an integrated services Internet.

Used by a host to request a specific QoS from the network.

Also used by the routers to deliver QoS requests to all nodes along the path(s) of the data stream and to establish and maintain state to provide the requested service.



RSVP reserve resources for simplex data streams (only one direction).

Operates on top of IP (either IPv4 or IPv6), like ICMP, IGMP.

Not a routing protocol, but designed to operate with current and future unicast and multicast routing protocol, like DVMRP (Distance Vector Multicast Routing Protocol), CBT (Core Based Tree), PIM (Protocol Independent Multicast), etc.

An RSVP daemon consults the local routing database(s) to obtain routes.



In the multicast case, a host sends IGMP messages to join a multicast group and then sends RSVP Resv messages to reserve resources along the delivery path(s) of that group.

Incoming packets are passes through a packet classifier which determines the route and the QoS class for each packet.

On outgoing interface, a packet scheduler then makes forwarding decisions for every packet, to achieve the promised QoS on the particular link-layer medium.



Admission control determines whether resources are sufficient to support the requested QoS.

Policy control determines whether the user is allowed to make the reservation.

Uses soft state in the routers. RSVP sends periodic refresh messages to maintain the state along the reserved path(s); in absence of refreshes, the state will automatically time out and be deleted.


RSVP in Hosts and Routers

AP

RSVPdaemon

Classifier PacketScheduler

PolicyControl

AdmisControl

RoutingProtocolDaemon

RSVPdaemon

Classifier PacketScheduler

PolicyControl

AdmisControl

RSVP RSVP

Data

Data

Data

Host Router

PacketScheduler Data


RSVP Operation Example

R1

SessionManager

CA

B

Resv

path

R3

R2 R4

R5

R6

IGMP

IGMP

DVMRP

path

path

Resv

Resv

21

3

4 5

6

78

9

10

12

13

14

15

Resvpath

Session (Ipa,PID,Port)

Receive (Ipa,PID,Port)

11 Receive (Ipa,PID,Port)


Data Flows

RSVP defines a session to be a data flow with a particular destination and transport-layer protocol (TCP/UDP).

The destination of a session is defined byDstAddr, the IP destination address of the data p

ackets.Protocol ID,DstPort, a generalized destination port (some fu

rther demultiplexing point in the transport or application protocol layer).


Reservation Model

An elementary RSVP reservation request consists of a

flow descriptor = (flowspec, filter spec).The flowspec defines a desired QoS and is used

to set parameters in the node’s packet scheduler.

The filter spec defines the set of data packets (flow) to receive the QoS defined by the flow spec, and is used to set parameters in the node’s packet classifier.


Reservation Model

The flow spec includes a service class and two sets of numeric parameters:an Rspec (R for reserve) that defines the QoS,

anda Tspec (T for Traffic) that describes the data

flow.The filter specs may select arbitrary subsets of t

he packets in a given session. The one used in present RSVP consisting of sender IP addr and optionally the UDP/TCP port number SrcPort.


Reservation Styles

A reservation request includes a set of options that are collectively called the reservation style. One concerns the treatment of reservations for diffe

rent senders within the same session : establish a distinct reservation for each upstream sender, or else make a single reservation that is shared among all packets of selected senders.

Another controls the selection of senders; an explicit list of all selected senders, or a wildcard that implicity selects all the senders to the session.


Reservation Styles

Fixed-Filter (FF) StyleShared-Explicit (SE) StyleWildcard-Filter (WF) Style

SenderSelection

Reservation

Distinct Shared

Explicit

Wildcard

Fixed-Filter (FF) Style

Shared-Explicit (SE) Style

Wildcard-Filter (WF) Style(None

defined)


Reservation Styles

Wildcard-Filter (WF) StyleShared reservation and wildcard sender selection. Creates a single reservation shared by all upstream senders.

WF ( *{Q} )Fixed-Filer (FF) Style

Distinct reservation and explicit sender selection.Creates a distinct reservation for data packets from a particular sender.

FF ( S {Q} ) <= a flow descriptorFF ( S1 {Q1}, S2 {Q2}, ... ) : The total reservation is the sum of Q1, Q2, ...


Reservation Styles

Shared Explicit (SE) StyleShared reservation and explicit sender selection.

Creates a single reservation shared by selected upstream senders.

SE ( {S1,S2,...}, {Q} )


Reservation Styles

These styles are all mutually incompatible.Shared reservations, created by WF and SE st

yles, are appropriate for those multicast applications in which multiple data sources are unlikely to transmit simultaneously (packetized audio).

Distinct reservation (FF style) is appropriate for the flows from different senders (video signals).


Example of Styles

WF (*{4B} )

Router

LANRouter

Router

R2

R3

R1S1

S2,S3

a

b

c

d

Router

LANRouter

Router

R2

R3

R1S1

WF (*{4B} )

*{4B}

*{3B}

WF (*{4B} )

WF (*{3B} )

WF (*{2B} )

(a) Router Configuration

(b) WF Reservation Example

S2,S3


Example of StylesFF (S1{4B} )

Router

LANRouter

Router

R2

R3

R1S1

S2,S3

FF (S2{5B},S3{B} )

FF (S1{4B},S2{5B} )

FF (S1{3B},S3{B} )

FF (S1{B} )

S1{4B}

S2{5B}

S1{3B}

S3{B}

SE (S1{3B} )Router

LANRouter

Router

R2

R3

R1S1

S2,S3

SE ((S2,S3){3B} )

SE ((S1,S2){B} )

SE( (S1,S3){3B} )

SE (S2{2B} )

(S1,S2) {B}

(S1,S2,S3) {3B}

(d) SE Reservation Example

(c) FF Reservation Example


Example of StylesRouter

LANRouter

Router

R2

R3

R1S1

S2,S3

a

b

c

d

(a) Router Configuration

WF (*{4B} )

Router

LANRouter

Router

R2

R3

R1S1

S2,S3WF (*{3B} )

*{4B}

*{3B}

WF (*{4B} )

WF (*{3B} )

WF (*{2B} )

(b) WF Reservation Example -Partial Routing


RSVP Protocol Mechanisms

There are two fundamental RSVP message types:Resv and Path

Each receiver host sends Rsev messages upstream towards the senders. These messages follow exactly the reverse of the path(s) the data packets will use, to all the selected senders. Each node along the path(s) creates and maintains the reservation state.

Router

LAN

CA a

b

c

dB

B’

D

D’

PreviousHops

IncomingInterfaces

OutgoingInterfaces

Next Hops

LANdata

path

Resvdata

data

data path

path

ResvResv

path

Resv


RSVP Protocol Mechanisms

Each RSVP sender issues Path messages downstream along the uni-multicast routes provided by the routing protocol(s), following the paths of the data.

Each node along the path(s) stores the path state (includes at least the IP address of the previous hop node).

An RSVP session is normally defined by the triple:(Dest IP Address, Protocol ID, DstPort)

TCP = 6, UDP = 17


Path Message Format

<Path Message> ::= <Common Header> [<Integrity>]

<Session> <RSVP_Hop> <Time_Values> [<Policy_Data> ... ] [<Sender Descriptor>]<Sender Descriptor> ::= <Sender_Template> <Sender_Tspec> [<ADspec>]


Common Header Format

Vers Flags Msg Type RSVP Checksum

Send_TTL (Reserved) RSVP Length

0 1 2 3

Message Type1 : Path 2 : Resv3 : PathErr4 : ResvErr5 : PathTear6 : ResvTear7 : ResvConf


Object Formats

Length (bytes) Class-Num C-Type

(Object contents)

0 1 2 3


Class-Num

NULLSESSION : (DestAddress, protocol ID, port)RSVP_HOP : The IP address of the RSVP-capable node th

at sent this message and logical outgoing interface handle (LIH).

TIME_VALUES : Refresh period R.STYLE : Reservation style plus style-specific information.FLOWSPEC : Defines a desired QoS, in a Resv message.FILTER_SPEC : Defines a subset of session data packets t

hat should receive the desired QoS, in a Resv message.


Class-Num

ADSPEC : Carries OPWA (one path with advertising) data, in a path message.

ERROR_SPEC : Specifies an error in a PathErr, ResvErr, or a confirmation in a ResvConf message.

POLICY_DATA : Carriers information for a local policy module to decide the permission of a reservation.

INTEGRITY : Carriers cryptographic data to authenticate the originating node and to verify the contents of the RSVP message.

SCOPE : Carriers an explicit list of sender hosts.RESV_CONFIRM : Carriers the IP address of a receiver t

hat requested a confirmation.


Path MessageRSVP_Hop: IP address of previous RSVP nodeSender Template :

Describes the format of the data packets that the sender will originate.

Sender TspecDefines the traffic characteristics of the data flow that the sender

will generate.Used by traffic control to prevent over-reservation.r : Token Bucket Rate (32-bit IEEE Floating Point number)b : Token Bucket Size (32-bit IEEE Floating Point number)p : Peak Data Rate (32-bit IEEE Floating Point number)m : Minimum Policed Unit (32-bit integer)M : Maximum Packet Size (32-bit integer)


Sender Traffic Specific

r

b

p

M

x <= (rT+b) min[pT+M, rT+b]

p > r

M < b

min[pT, rT+b]

(packetize version)

data

b : Maximum burst size

Sender


Resv Message

<Resv Message> ::= <Common Header> [<Integrity>] <Session> <RSVP_Hop> <Time_Values> [<Resv_Confirm>] [ <Scope>] [<Policy_Data>...] [<Style> <flow descriptor list>]

<flow descriptor list> ::= <empty> | <flow descriptor list> <flow descriptor>


Host ModelBefore a session can be created, the

session ID must be assigned and communicated to all the senders and receivers by some out-of-band mechanism.

When an RSVP session is being set up, the following events happen at the end systems:


Host Model

A receiver joins the multicast group specified by DstAddr (Multicast), using IGMP.

A potential sender starts sending RSVP Path messages to the DstAddr.

A receiver application receives a Path message.A receiver starts sending appropriate Resv mes

sages, specifying the desired flow descriptors.A sender application receives a Resv message.A sender starts sending data packets.


RSVP AttributesRSVP makes reservations for both unicast and multi

cast applications, adapting dynamically changing of group membership and routes.

RSVP is simplex, it makes reservations for unidirectional data flows.

RSVP is receiver-oriented. The receiver of a data flow initiates and maintains the resource reservation used for that flow.

RSVP maintains soft state in the routers, providing graceful support for dynamic membership changes and automatic adaptation to routing changes.


RSVP Attributes

RSVP is not a routing protocol but depends upon present and future routing protocols.

RSVP transports and maintains opaque state for traffic control and policy control.

RSVP provides several reservation models to fit a variety of applications.

RSVP provides transparent operation through routers that do not support it.

RSVP supports both IPv4 and IPv6.