Transcript PowerPoint file - 정보통신연구실(INC LAB)

Integrated Services
RSVP
Differentiated Services
전산과학과 정보통신 연구실
최 선 웅
9월 23일
2016-04-11
 SNU 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
traffic
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


Purpose of this working group




The transport of audio, video, real-time, and classical data
traffic within a single network infrastructure
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



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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)
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
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Controlled load(RFC 2211)




provide assured capacity level, or data rate
specified upper bound on the queuing delay
no queuing losses
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

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Queuing discipline
Discard policy
Resource reservation
 Reservation Protocol(RSVP)
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IS Router Components
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Classifier



Incoming packet must be mapped into some class
Choice of a class is based on fields in the packet header
Packet scheduler

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

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

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Create and maintain flow-specific state
Carry flowspec to admission control
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IS Host/Router Components
HOST
ROUTER
RSVP
Application
RSVP
Process
RSVP
Process
Policy
Control
Policy
Control
Routing
Process
Admission
Control
Classifier
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Packet
Scheduler
Admission
Control
DATA
Classifier
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Packet
Scheduler
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
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Characteristics


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
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
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


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Why?




In unicast, this approach is reasonable
Inadequate for multicasting
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
Policy Server
COPS
LDP
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PDP
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


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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
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Session
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Flow spec

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Destination IP address
IP protocol id
Destination port
Service class
RSpec
TSpec
Filter spec


Source address
UDP/TCP source port
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Relationship
Packet
Scheduler
Packets that
pass filter
Packets
Flowspec
Filterspec
Best-effort
delivery
Other
packets
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QoS
delivery
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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 Attribute
Sender
Selection
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Distinct
Shared
Explicit
Fixed-filter
(FF) style
Shared-explicit
(SE) style
Wildcard
-
Wildcard-filter
(WF) style
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Reservation Style Notation

Notation


Wildcard Filter(WF) style


WF(*{Q})
Shared Explicit style


Filterspec{Flowspec}
SE(S1, S2, … {Q})
Fixed Filter(FF) style

FF(S1{Q1}, S2{Q2}, …)
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Basic RSVP Message

Two basic message type

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Path message




Resv / Path
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 Example
R1
Path(N2, S2)
Path(N2, S1)
Path(N1, S2)
S1
N1
Path(S1, S1)
N2
N1
N2
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Path(N2, S1)
Path(N2, S2)
S2
Phop
S1
N1
R2
Path(N1, S1)
Path(N2, S2)
Filterspec
S1
S1
Path(N2, S2)
Path(N2, S1)
R3
Reserved
0
0
Filterspec Phop Reserved
S1
S1
0
N1
S2
S2
0
S1
N1
0
N2
S2
N1
0
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Reservation Example : WF
R1
Resv(WF(*{3B}))
S1
N1
Resv(WF(*{5B})
N2
Resv(WF(*{5B}))
Resv(WF(*{5B}))
S2
Resv(WF(*{5B}))
Resv(WF(*{2B}))
R3
Filterspec Phop Reserved
S1
S1
5B
N1
S2
S2
5B
S1
N1
5B
N2
S2
N1
5B
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R2
Reservation Example : FF
R1
Resv(FF(S1{4B}, S2{2B}))
S1
N1
Resv(FF(S1{5B}))
N2
Resv(FF(S1{5B}))
Resv(FF(S1{5B}, S2{3B}))
Resv(FF(S2{3B}))
S2
Resv(FF(S1{B}, S2{3B}))
R3
Filterspec Phop Reserved
S1
S1
5B
N1
S2
S2
3B
S1
N1
5B
N2
S2
N1
3B
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R2
Reservation Example : SE
R1
Resv(SE(S1, S2{2B}))
S1
N1
Resv(SE(S1{5B}))
N2
Resv(SE(S1, S2{5B}))
Resv(SE(S2{5B}))
S2
Resv(SE(S2{5B}))
Resv(SE(S1, S2{3B}))
R3
Filterspec Phop Reserved
S1
S1
5B
N1
S2
S2
5B
S1
N1
5B
N2
S2
N1
5B
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R2
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)



RSpec : Rate(R) and delay slack(S)



All datagrams less than m are counted as m bytes
Peak rate may be unknown or unspecified
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
( b  M )( p  R ) M  Ctot
Qdelayend2end 

 Dtot( p  R  r )
R( p  r )
R
M  Ctot
Qdelayend2end 
 Dtot( R  p  r )
R

Error terms : C, D
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Path Message

Phop


Sender Template



last node address
Filter specification
Sender TSpec
Optional ADSPEC

One Path With Advertising(OPWA) information
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Processing Path Message

Update the path state

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Store Phop


If no path state exists, create it
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


Initial check (R = p)


End-to-end delay required by the receiver’s application – the
minimum path latency
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
b
Ctot i
b Ctot i
Sout 

 Sin 

( r  Rout  Rin )
Rout Rout
Rin Rin
Ctot i : the cumulative sum of the error terms, C for all the
routers that are upstream of, and including, the
current element i
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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)


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Assured Service(D. Clark)



Scheduling priority
Strict admission control
Virtual leases line
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


DS byte


A collection of packets with the same code point crossing a
boundary in a particular direction
IPv4 TOS octet or IPv6 Traffic Class octet
Per-hop Behavior(PHB)

Forwarding treatment applied at a differentiated servicesenabled node to a behavior aggregate
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DS byte
0 1
2
3
PHB


4 5
6
7
CU
PHB: per-hop behavior
CU: currently unused
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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
Conditioner
Meter
Packets
Classifier
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Marker
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Shaper/
Dropper
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
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Summary

Support QoS in the Internet


Intserv/RSVP
Diffserv
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