snu inc lab 2015-09-06 integrated services rsvp differentiated services 전산과학과 정보통신...
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23年 4月 19日 SNU INC LabSNU INC Lab
Integrated ServicesRSVP
Differentiated Services
전산과학과 정보통신 연구실최 선 웅9 월 23 일
23年 4月 19日 SNU INC LabSNU INC Lab
History IP-based Internet
provide a simple best-effort delivery service to all applications
New real-time, multimedia, and multicasting applications are not well supported, in IP-based Internet. construct a second networking infrastructure for real-time tra
ffic replace the existing IP-based configuration with ATM
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Integrated Services Architecture(ISA) Strong need to support a variety of traffic with a
variety of QoS requirements, within the TCP/IP architecture
Fundamental requirement add new functionality to routers and a means for requesting
QoS-based service from Internet
IETF is developing a suite of standards under the general umbrella of the Integrated Services Architecture(ISA)
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Integrated Services(intserv) Integrated Services
The transport of audio, video, real-time, and classical data traffic within a single network infrastructure
Purpose of this working group Define the enhanced Internet service model Defining the application service, router scheduling and
(general) subnet interfaces Developing router validation requirements which can ensure
that the proper service is provided
RFC’s Specification of the Controlled-Load Network Element
Service (RFC 2211) Specification of Guaranteed Quality of Service (RFC 2212)
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Internet Traffic Elastic Traffic
can adjust to change in delay and throughput across Internet and still meet the needs of its applications
non-real-time application FTP, SMTP, TELNET, SNMP, HTTP
Inelastic Traffic does not easily adapt to changes in delay and throughput
across Internet real-time application
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Inelastic traffic Inelastic traffic
Tolerant / Intolerant depending on whether they can tolerate occasional loss
Adaptive / Non-adaptive depending on their adaptability Delay-adaptive / Rate-adaptive
Requirement for inelastic traffic need of means to give preferential treatment to applications
with more demanding requirements elastic traffic must still be supported
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ISA Service Class Guaranteed(RFC 2212)
provide assured capacity level, or data rate specified upper bound on the queuing delay no queuing losses
Controlled load(RFC 2211) approximation no specified upper bound on the queuing delay, but ensure
that a very high percentage of the packets do not experience delays that greatly exceed the minimum transit delay
almost no queuing loss
Best effort
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Flow Flow
distinguishable stream of related IP packets that results from a single user activity and requires the same QoS
Flow vs. TCP connection A flow is unidirectional There can be more than one recipient of a flow(multicast)
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Internet Traffic Control Conventional Traffic Control
Routing algorithm Most routing protocols in use in Internet allow routes to be
selected to minimize delay Packet discard
When overflows, discard packets Typically, the most recent packet is discarded
These tools have worked reasonably well
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Requirements ISA Approach
Flowspec Admission Control Routing algorithm
may be based on a variety of QoS parameters, not just minimum delay
Queuing discipline Discard policy Resource reservation
Reservation Protocol(RSVP)
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IS Router Components Classifier
Incoming packet must be mapped into some class Choice of a class is based on fields in the packet header
Packet scheduler Manage queues for each output port Determine the order of packet transmission and discard Based on a packet’s class, the contents of the traffic control
database, and current and past activity on this outgoing port Determine whether the packet traffic in given flow exceeds
the required capacity and if so, decide how to treat the excess packets policing
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IS Router Components(Cont’d) Admission Control
Implement the decision algorithm Enforce administrative policy Accounting and administrative reporting
Reservation Setup Protocol Create and maintain flow-specific state Carry flowspec to admission control
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IS Host/Router Components
Application
RSVPProcess
PolicyControl
ClassifierPacket
Scheduler
AdmissionControl
RoutingProcess
RSVPProcess
PolicyControl
ClassifierPacket
Scheduler
AdmissionControl
HOST ROUTER
RSVP
DATA
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Resource Reservation: RSVP Design goals
Heterogeneous receivers Dynamic multicast group membership Enable receivers to select one source from among multiple
sources transmitting to a multicast group Deal gracefully with changes in routes, automatically
reestablishing tree the resource reservation along the new paths
Minimize protocol overhead Be independent of routing protocol
RFC’s Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification(RFC 2205)
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RSVP Characteristics Characteristics
Unicast and multicast Soft state Receiver-initiated reservation Simplex Different reservation styles Transparent operation through non-RSVP routers Support for IPv4 and IPv6
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Receiver-initiated Reservation In ATM, the source of a data flow requests resources
In unicast, this approach is reasonable Inadequate for multicasting
Why? Some members of a multicasting group may not require
delivery from a particular source over some period of time Some members of a group may only be able to a portion of
the source transmissions
Sender provide the routers with the traffic characteristics of the transmission
Receiver specify the desired QoS
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Soft State Reservation state is cached information in the router Periodically refreshed by end system If a state is not refreshed within a required time limit,
the router discards the state If a new route becomes preferred for a given flow, the
end systems provide the reservation to the new routers on the route
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RSVP Admission Control RSVP process communicates with two local decision
modules admission control
determines the node has sufficient available resources to supply the requested QoS
policy control determines whether the user has administrative permission to
make the reservation
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RSVP Admission Control(Cont’d) If either check fails,
RSVP returns an error notification to the application process that originated the request
If both check succeed, RSVP sets parameters in a packet classifier and packet
scheduler to obtain the desired QoS The packet classifier determines the QoS class for each packet The packet scheduler orders packet transmission to achieve
the promised QoS for each stream
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RSVP Admission Policy(rap)
Network Node
PEP PDP
Policy Server
LDP
COPS
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Scalability Scalability
Receiver-oriented reservation requests that merge as they progress up the multicast tree
While RSVP protocol is designed specifically for multicast applications, it may also make unicast reservations
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Robustness RSVP is designed to utilize the robustness of current
Internet routing algorithms RSVP does not perform its own routing Use underlying routing protocols to determine where it
should carry reservation requests As routing changes paths to adapt to topology changes,
RSVP adapts its reservation to the new paths wherever reservations are in place
RSVP runs over IP, both IPv4 and IPv6
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Data Flows Session
Destination IP address IP protocol id Destination port
Flow spec Service class RSpec TSpec
Filter spec Source address UDP/TCP source port
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Relationship
Filterspec
FlowspecQoS
delivery
Best-effortdelivery
Packets thatpass filter
Otherpackets
Packets
PacketScheduler
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RSVP Operation: Filtering An example of filtering
Fig. Filtering a substream
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Reservation Styles Reservation attribute
shared/ distinct
Sender selection explicit/ wildcard
Reservation AttributeSender
SelectionDistinct Shared
ExplicitFixed-filter(FF) style
Shared-explicit(SE) style
Wildcard -Wildcard-filter
(WF) style
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Reservation Style Notation Notation
Filterspec{Flowspec}
Wildcard Filter(WF) style WF(*{Q})
Shared Explicit style SE(S1, S2, … {Q})
Fixed Filter(FF) style FF(S1{Q1}, S2{Q2}, …)
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Basic RSVP Message Two basic message type
Resv / Path
Path message Provide upstream routing information Each host that wishes to participate as a sender in a
multicast group issues a Path message Transmitted throughout the distribution tree to all multicast
destination
Resv message Originate at a receiver and propagate upstream, being
merged Must be repeated periodically to maintain the soft states
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RSVP Mechanism Overview Procedure
a. A receiver joins a multicast group by sending an IGMP join message to a neighboring router
b. A potential sender issues a Path message to the multicast group address
c. A receiver receives a Path message identifying a sender
d. The receiver sends Resv messages, specifying the desired flow descriptors
e. The Resv message propagates through the internet and is delivered to the sender
f. The sender starts sending data packets
g. The receiver starts receiving data packets
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Reservation ExampleR1
S1
S2
R2N1 N2
R3
Path(S1, S1) Path(N1, S1) Path(N2, S1)
Path(N2, S1)
Path(N2, S1)
Path(N1, S2)
Path(N2, S2)
Path(N2, S2)
Path(N2, S2)Path(N2, S2)
Filterspec Phop ReservedN1 S1 S1 0
N2 S1 N1 0
Filterspec Phop Reserved
S1 S1 0N1
S2 S2 0S1 N1 0
N2S2 N1 0
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Reservation Example : WFR1
S1
S2
R2N1 N2
R3
Resv(WF(*{5B}))
Resv(WF(*{3B}))
Resv(WF(*{2B}))
Resv(WF(*{5B}))
Filterspec Phop Reserved
S1 S1 5BN1
S2 S2 5BS1 N1 5B
N2S2 N1 5B
Resv(WF(*{5B})
Resv(WF(*{5B}))
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Reservation Example : FFR1
R2N2
R3
Resv(FF(S1{4B}, S2{2B}))
Resv(FF(S1{B}, S2{3B}))
Resv(FF(S1{5B}))
Filterspec Phop ReservedS1 S1 5B
N1S2 S2 3BS1 N1 5B
N2S2 N1 3B
S1
S2
N1Resv(FF(S1{5B}, S2{3B}))Resv(FF(S1{5B}))
Resv(FF(S2{3B}))
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Reservation Example : SER1
R2N2
R3
Resv(SE(S1, S2{2B}))
Resv(SE(S1, S2{3B}))
Resv(SE(S2{5B}))
Filterspec Phop ReservedS1 S1 5B
N1S2 S2 5BS1 N1 5B
N2S2 N1 5B
S1
S2
N1Resv(SE(S1, S2{5B}))Resv(SE(S1{5B}))
Resv(SE(S2{5B}))
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Flow Specification Flowspec = Traffic Spec + QoS Spec
= TSpec + RSpec TSpec : Peak rate(p), bucket rate(r), bucket size(b),
max datagram size(M), min policed unit(m) All datagrams less than m are counted as m bytes Peak rate may be unknown or unspecified
RSpec : Rate(R) and delay slack(S) S = Extra acceptable delay over that obtainable with R Zero slack ==> Reserve exactly R.
RSpec specified only for guaranteed rate service.
Not for controlled load service.
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Guaranteed Service Firm end-to-end delay bound
Error terms : C, D
)rRp(DR
CM
)rp(R
)Rp)(Mb(Q tot
totenddelayend
2
)rpR(DR
CMQ tot
totenddelayend
2
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Path Message Phop
last node address
Sender Template Filter specification
Sender TSpec Optional ADSPEC
One Path With Advertising(OPWA) information
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Processing Path Message Update the path state
If no path state exists, create it
Store Phop In order to route Resv message
Set cleanup timer Expiration of the cleanup timer triggers deletion of the path
state Soft-state
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ADSPEC Optional object to advertise to receivers the
characteristics of the end-to-end communication path ADSPEC format
Message header Default General Parameters fragment
minimum path latency, Global break bit, Path bandwidth, Integrated Service Hop Count, PathMTU
Guaranteed Service fragment Ctot, Dtot, Csum, Dsum, Guaranteed Service Break bit, Guaranteed
Service General Parameters Header/Values Controlled-Load Service fragment
Controlled-Load Service Break Bit, Controlled-Load Service General Parameters Headers/Values
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Reservation using OPWA Qdelreq : the required bound on end-to-end queuing
delay End-to-end delay required by the receiver’s application – the
minimum path latency
Initial check (R = p) Choose an equation
Find R
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Slack Term S : slack term
End-to-end delay required by the application – End-to-end delay bound
Ctot i : the cumulative sum of the error terms, C for all the routers that are upstream of, and including, the current element i
)RRr(R
C
R
bS
R
C
R
bS inout
in
tot i
inin
out
tot i
outout
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Problems of Intserv Resource reservations for flow-based traffic
High overheads of setting-up a reservation Difficult determination of required resources Overhead of authentication, authorization, and accounting
per flow Scalability problem
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Differentiated Services(diffserv) Objective
Provide scalable service discrimination in the Internet without the need for per-flow state and signaling at every hop
Simple and coarse methods of providing differentiated classes of service for Internet traffic
How-to-do Setting bits in the TOS octet at network edges and
administrative boundaries Using those bits to determine how packets are treated by
the routers inside the network Conditioning the marked packets at network boundaries in
accordance with the requirements of each service
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Related Proposals Premium Service(V. Jacobson)
Scheduling priority Strict admission control Virtual leases line
Assured Service(D. Clark) Drop priority A better best-effort
User-Share Differentiation(Z. Wang) User
Who are granted some bandwidth Share
How much bandwidth is allocated to a user
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Diffserv Working Group Feb 98
Working group formed
Goals Standardize the 'DS byte’ Assign specific per-hop behaviors to the DS byte Define the framework of the differentiated services
architecture Experiment with other per-hop behaviors that can be used to
produce additional services
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Terminology Behavior aggregate
A collection of packets with the same code point crossing a boundary in a particular direction
DS byte IPv4 TOS octet or IPv6 Traffic Class octet
Per-hop Behavior(PHB) Forwarding treatment applied at a differentiated services-
enabled node to a behavior aggregate
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DS byte
PHB: per-hop behavior CU: currently unused
PHB CU
10 2 3 4 5 6 7
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Per-Hop Behaviors Differentiated services model
Router has a set of parameters that can be used to control how packets are scheduled onto an output interface
N separate queues with settable priorities, queue lengths, round-robin weights, drop algorithm, drop preference weights and thresholds, etc
Two per-hop behaviors Default(DE: 000000)
common, best-effort forwarding Expedited Forwarding(EF: 000010)
high priority behavior typically used for network control traffic such as routing updates
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Traffic Classification and Conditioning Packet classification
Identify the subset of traffic which may receive a differentiated service within the DS domain
Traffic conditioning Metering, shaping, policing and remarking
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Classifier and Conditioner
Classifier Marker
Meter
Shaper/Dropper
Packets
Conditioner
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Traffic Management Traffic conditioner
Meter Measures traffic against profile Passes state information to other conditioning functions
Marker Sets codepoint(possibly based on metering)
Shaper/dropper Delays or drops packets