qos

1
Edward Jin-Ru Chen QoS 1
Quality of Service
Acute Communication Corp.
Edward 1in-Ru Chen
jzchen¡acutecomm.com.tw
Edward Jin-Ru Chen QoS 2
Contents
!Introduction
!QoS Mechanisms
!QoS Architecture
2
Edward Jin-Ru Chen QoS 3
Definitions
!What is Quality of Service (QoS)?
"describes absolute, quantiIiable level oI network behavior
(e. g. 5Mbps oI bandwidth, 100ms delay)
"per- application, per- connection, per- Ilow granularity
!What is Class of Service (COS)?
"sort all traIIic (Ilows) into a Iew groups
"treat groups with relative level oI service
"per- group/ class granularity
Edward Jin-Ru Chen QoS 4
QoS Examples
!Examples
"IP network - RSVP/Integrated service (IntServ)
"ATM network
!Characteristics
"'Hard ' guaranteed at
# RSVP/IntServ provides per-flow guarantee
# ATM provides per-VC guarantee
3
Edward Jin-Ru Chen QoS 5
Term Definitions
!Flow
"IntServ: distinguishable stream of related datagrams that results from a
single user activity and requires the same QoS
"RSVP: Destination IP and Protocol
"DiffServ: Source IP, Destination IP, Source port, Destination port,
Protocol
!VC/VP
"Virtual Circuit/ Virtual Path
"Decided after the signaling process
"Tag for switching
"Address is used for signaling and forwarding path establish
Edward Jin-Ru Chen QoS 6
COS Examples
!Examples
"IP TOS
"IP DiIIServ
!Characteristics
"'SoIt¨ guarantee at per-class base
4
Edward Jin-Ru Chen QoS 7
QoS Mechanisms
!Traffic Conditioner
"ClassiIier
"Dropper/Shaper
!Queue Management
!Scheduler
Edward Jin-Ru Chen QoS 8
Classifier
!Determine the class/flow of packet based on the
class/flow definition
!Mechanisms for classifier
"Linear search and caching
"Content addressable memory
"Tree search
"Hashing Iunction
5
Edward Jin-Ru Chen QoS 9
Content Addressable Memory
!Pure hardware solution
!Parallel search all stored entries
!Advanced CAM can provide mask for search
"Priority setting Ior conIlict resolution
Edward Jin-Ru Chen QoS 10
What is CAM?
C 19
B 7
A 6
C
D 58
C
C
C
C
19
6
Edward Jin-Ru Chen QoS 11
What is Ternary CAM?
C 19
B 7
A 6
C
D 58
19
Mask A
Mask B
Mask C
Mask D
C
C
C
C
Edward Jin-Ru Chen QoS 12
Ternary CAM
!Store words with three-valued digits
"0, 1, x` (wildcard)
!Stored position represents the priority
"Multiple-match may occurred at ternary CAM
"Priority to resolve the multiple matching problem
7
Edward Jin-Ru Chen QoS 13
Tree Search
!Based on each prefix to construct a searching tree
!Go through the tree and end with the search result
!Improvements
"Extend tree to array Ior speed-up
"Compress tree to reduce space requirement
!Facing multiple path selection problem when
apply to layer4 lookup
Edward Jin-Ru Chen QoS 14
Tree Search Example
a.b.c.x A
a.b.x.x B
a.x.x.x C
a.b.d.x D
a C b B
c A
d D
8
Edward Jin-Ru Chen QoS 15
Hashing Function
!Transfer search key into hashing result
"H(X) ÷ Y
"X may be MAC address, IP address or anything required
"X has more bits than Y
!Using the hashing result to identify the record
position
!Store the search key for collision checking
!Fast but collision may occur
Edward Jin-Ru Chen QoS 16
Classes of Hashing Function
!Assumes: key bits, hashing result bits
!Bit extraction hashing functions
"Selecting f bits out oI the i bits
!Hashing Functions from XOR method
"Such as h(x) ÷ (x
1
xor x
5
)(x
2
xor x
6
)(x
3
xor x
7
)(x
4
xor x
8
)
!Hashing functions from the class H

"Based on Q, which is i x j Boolean matrices
"Hashing result ÷ Q X Key
"H
q
(x) ÷ x(1)q(1) xor x(2)q(2) xor . x(i)q(i)
9
Edward Jin-Ru Chen QoS 17
Policing/Shaping
!Based on token-bucket or leaky-bucket
!Meter measures the traffic characteristics
!Policing checks conformance to a configured (or
signaled) traffic profile
"Data passed when in-proIile
"Dropping or shaping when out-oI-proIile
Edward Jin-Ru Chen QoS 18
Leaky Bucket
10
Edward Jin-Ru Chen QoS 19
Leaky Bucket Parameters
!Parameters
"Token arrival rate : Allowed average packet arrival rate
"Token queue size : Allowed burst size
"Packet queue size : Packet number allowed Ior shaping
!Dropper
"Zero packet queue size
!Shaper
"Non-zero packet queue size
Edward Jin-Ru Chen QoS 20
Queue Scheduling
!Traditional FIFO queuing provides no service
differentiation and can lead to network performance
problems
!IP QoS requires routers to support (some form of) queue
scheduling and management to prioritize outbound
packets and control queue depth (minimize congestion)
11
Edward Jin-Ru Chen QoS 21
Why Queue Management?
!Full Queues are problematic
"New connections cannot get thru (called Lock-Out)
"All packets Irom existing Ilows are dropped resulting in
across-the-board TCP slow-starts (called Global
Synchronization)
"Can't handle bursts oI traIIic
!RED (random early detection) is a queue
management solution
Edward Jin-Ru Chen QoS 22
Queue Management Scheme
!RED
"Random Early Detection
"Drop packet beIore queue is Iull
"Derived Irom TCP Ilow control characteristic
!RIO
"RED with in-proIile/out-oI-proIile awareness
!TSW
"Time-sliding window
"Provide a smooth estimate oI the TCP sending rate
12
Edward Jin-Ru Chen QoS 23
Random Early Detection
!Dropping decision based on Average Queue
Length
Edward Jin-Ru Chen QoS 24
TCP Flow Control
!Sliding window flow control
!Accumulated acknowledgement
!Duplicate ACK to indicate packet loss
!Packet loss represents the occurrence of
congestion
!Reduce the window size when congestion is
detected
13
Edward Jin-Ru Chen QoS 25
TCP Flow Control Figure
Edward Jin-Ru Chen QoS 26
Rough Description
14
Edward Jin-Ru Chen QoS 27
General Algorithm
Eor each packet arrival
Calculate the average queue size avg
II min

·÷ avg · max

calculate probability P

with probability P

mark the arriving packet
Else iI max

·÷ avg
mark the arriving packet
Edward Jin-Ru Chen QoS 28
Pa Calculation
P

·- max

(avg - min

)/(max

- min

)
P

·- P

PacketSize/ MaximumPacketSize
P

·- P

/(1 - count·P

)
15
Edward Jin-Ru Chen QoS 29
Queue Length Calculation
!Low-pass filter is an exponential weighted moving
average (EWMA)
"avg ÷ (1 - w

)avg ¹ w

q
"II w

too large unable to Iilter out transient congestion
"II w

too small, avg is not a reasonable reIlection oI the
current average queue size
Edward Jin-Ru Chen QoS 30
RIO Algorithm
Average Queue Length
Dropping Probability
In-proIile
Out-oI-proIile
16
Edward Jin-Ru Chen QoS 31
Time-sliding window
! Rate estimator and tagging packet as when estimated
rate larger than threshold
!Initially
"Win¸length ÷ a constant
"Avg¸rate ÷ connection`s target rate
"T¸front ÷ 0
!Upon each packet arrival
"Bytes¸in¸TSW ÷ Avg¸rate * Win¸length
"New¸bytes ÷ Bytes¸in¸TSW ¹ pkt¸size
"Avg¸rate ÷ New¸bytes/ (now T¸front ¹ Win¸length)
"T¸front ÷ now
Edward Jin-Ru Chen QoS 32
Scheduler
!Weighted Round Robin
!Deficit Round Robin
!Weighted Fair Queuing
!Class Based Queue
17
Edward Jin-Ru Chen QoS 33
Round Robin Scheduling
!Round Robin
"A server process circularly and repeatedly visits a number
oI clients and perIorms one job Ior each oI them that has
such a need at the time oI the visit
"Eair to each client with identical packet size
Queue A
Queue B
Queue C
Queue D
Queue E
Edward Jin-Ru Chen QoS 34
Weighted Round Robin
!Provide different service instead of fair service
!Some queues are serviced more than one time in a
cycle
Queue A
Queue B
Queue C
Queue D
18
Edward Jin-Ru Chen QoS 35
Weighted Round Robin
!Make the visit more smooth among clients
Edward Jin-Ru Chen QoS 36
Fair Queuing
!Objectives
"Iair access to bandwidth and resources in routers
"no one Ilow shall receive more than its Iair share
!Assume queues are serviced in a bit-by-bit round
robin (BR) fashion
"transmit one bit Irom each queue
"But one cannot interleave bits Irom diIIerent queues
19
Edward Jin-Ru Chen QoS 37
Weighted Fair Queue
!Provide more than fair-share of the bandwidth
!WFQ is work-conserving
"Router will always transmit packets iI they are present in
the queue link is never idle
!What is non-work-conserving?
"Even the queue has packet to send when the output port is
idle, packets may stay at the queue instead oI transmission
"Eor delay and jitter requirement
Edward Jin-Ru Chen QoS 38
WFQ Algorithms
!Deficit Round Robin (DRR)
!Virtual Clock
!Packet-by-packet Generalized Processor Sharing
(PGPS)
!Self-Clocked Fair Queueing (SCFQ)
20
Edward Jin-Ru Chen QoS 39
Deficit Round Robin
Round Robin Pointer
20 750 200
500 500
200 600 100
50 700 180
500
0
0
0
Packet Queue
DeIicit
Counter
Quantum Size
500
Round Robin Pointer
20 750
500 500
200 600 100
50 700 180
300
500
0
0
Packet Queue
DeIicit
Counter
Quantum Size
500
Edward Jin-Ru Chen QoS 40
Time Division Multiplexing
!Guaranteed service rate and service delay
!Service time of each packet is known at the packet
arrival time
!Bandwidth waste when packet not arrived on time
A B C D A B C D A B C D A B C D A B C D
21
Edward Jin-Ru Chen QoS 41
Virtual Clock
Edward Jin-Ru Chen QoS 42
Virtual Clock Concept
Emulate Time Division Multiplexing
EX. A:B:C ÷ 1:2:3
A
B
C
Received service sequence is
based on the expected service
time
22
Edward Jin-Ru Chen QoS 43
Virtual Clock Characteristics
!Achieve fairness and bounded delay service when
all links are full of data traffic
"All packet received the same service time as TDM does
!Unused bandwidth will be accumulated for latter
use
!Not fair for other link
!Sorting is required for selecting the link to be
serviced next
Edward Jin-Ru Chen QoS 44
PGPS
arrived packet every time update is ) (
)} ( , max¦
0























φ
+ =
=
=
−
23
Edward Jin-Ru Chen QoS 45
PGPS Characteristics
!Avoid the bandwidth accumulation weakness of
Virtual Clock Algorithm
"The no-used bandwidth will be used by other link
"The silence link will get its Iair-share when become active
!Centralized virtual clock is required
!Sorting is still required
Edward Jin-Ru Chen QoS 46
SCFQ





















`
` ,
`
) ( `
)) ( ` ,
`
max(
1
`
0
`


≤ < ≅
+ =
=
−
24
Edward Jin-Ru Chen QoS 47
SCFQ Characteristics
!Avoids the centralized virtual clock maintenance
required by PGPS
"Simpler the implementation
"Reduce the level oI delay guarantee
!Sorting is still required
Edward Jin-Ru Chen QoS 48
Link Sharing
!Requirement for link-sharing
"Share bandwidth on a link between multiple organizations
"Share bandwidth on a link between diIIerent protocol
Iamilies
"Share bandwidth on a link between diIIerent traIIic types
!Link-sharing goal
"Rough quantitative bandwidth commitment by the network
"When some class is not using its allocated bandwidth, the
distribution oI the excess` bandwidth among the other
classes should Iollow some appropriate guideline
25
Edward Jin-Ru Chen QoS 49
Class-Based Queueing
A B C
video Itp video Itp video Itp
50°
10°
40°
1, 5° 2, 45° 1, 5° 1, 5° 2, 5° 2, 35°
Edward Jin-Ru Chen QoS 50
QoS Architectures (I)
!Integrated Services (IntServ)
"Internet service model that includes best-eIIort service,
real-time service, and controlled link sharing
"REC1633
!Resource ReSerVation Protocol (RSVP)
"Provide receiver-initiated setup oI resource reservations Ior
multicast or unicast data Ilows, with good scaling and
robustness properties
"REC2205, REC2208, REC2209
26
Edward Jin-Ru Chen QoS 51
QoS Architectures (II)
!Differentiated Services (DiffServ)
"Enable scalable service discrimination in the Internet
without the need Ior per-Ilow state and signaling at every
hop
"A variety oI services may be built Irom a small, well-
deIined set oI building blocks which are deployed in
network nodes
"REC2474, REC2475, REC2597, REC2598
Edward Jin-Ru Chen QoS 52
Traditional Architecture
!Best-effort architecture
!No service guarantee
!No signaling requirement
!Users send as much as they want
!Networks service as much as they can
!Simple FIFO, drop tail
!Drawback
"Hard to achieve real-time requirement
"Hard to give different service quality based on different billing level
27
Edward Jin-Ru Chen QoS 53
Integrated Services
!Extend the best-effort architecture
"An extended service model, IS model
"A reIerence implementation Iramework
!Assumptions
"Resources (e.g., bandwidth) must be explicitly managed in
order to meet application requirements
# Resource reservation
# Admission control
"Use the Internet as a common inIrastructure
Edward Jin-Ru Chen QoS 54
IntServ Framework
!Components
"Packet scheduler
"Admission control routine
"ClassiIier
"Reservation setup protocol
!Traffic control components to provide QoS
"Packet scheduler
"Admission control routine
"ClassiIier
28
Edward Jin-Ru Chen QoS 55
IntServ Reference Model
Input
Driver
ClassiIier
Internet
Eorwarder
Packet
Scheduler
Output Driver
Routing Engine
Routing Database
Reservation Setup Agent
TraIIic Control Database
Admission Control
Management Agent
Edward Jin-Ru Chen QoS 56
IntServ Model
29
Edward Jin-Ru Chen QoS 57
QoS Requirements
!The only quantity are bounds on the maximum
and minimum delays
!Classes of applications
"Real-time applications
# Applications needs the data in each packet by a certain time and, if
the data has not arrived by then, the data is essentially worthless
"Elastic applications
# Applications will always wait for data to arrive
Edward Jin-Ru Chen QoS 58
Link-Sharing Examples
!Multi-entity link-sharing
"Shared among organizations
!Multi-protocol link-sharing
"Shared among deIined protocol groups
!Multi-service sharing
"Shared among deIined applications
30
Edward Jin-Ru Chen QoS 59
Admission Control
!The decision about resource availability
!Require the router understand the demands that
are currently being made on its assets
!Traditional way
"Remember the service parameters oI past requests and
make a computation based on the worst-case bounds on
each service
!Recent proposal for better link utilization
"Measure the actual usage by existing packet Ilows and use
this measured inIormation Ior admission control
Edward Jin-Ru Chen QoS 60
IntServ Components
!Reservation Protocol - RSVP
!Traffic Control:
"Admission/Policy Control Determines iI QoS request
can/should be granted
"ClassiIier maps packets to a service class by looking at
contents oI IP header
"Packet Scheduler Iorwards packets based on service class
using sophisticated queuing mechanisms (e. g. WEQ)
31
Edward Jin-Ru Chen QoS 61
Resource Reservation Protocol
(RSVP)
!RSVP Flow:
"PATH messages mark path and deliver sender and path
QoS inIormation to receiver
"RESV messages Ilow upstream towards sender and lay
down QoS state
"soIt state so PATH and RESV reIresh messages Ilow
periodically
!RFC2205
Edward Jin-Ru Chen QoS 62
RSVP Attributes
!Make resource reservation for both unicast and
many-to-many multicast
!Make reservations for unidirectional data flows
!Receiver-oriented
!Maintains ~soft¨ state in routers and hosts
!Not routing protocol but depends on routing
protocol
!Provides several reservation models or styles
32
Edward Jin-Ru Chen QoS 63
RSVP Flow
Edward Jin-Ru Chen QoS 64
Reservation Model
!Flowspec is a reservation request include
"Rspec: deIines the desired QoS
"Tspec: deIines the data Ilow
!Reserve request actions
"Make a reservation on a link
"Eorward the request upstream
33
Edward Jin-Ru Chen QoS 65
Reservation Styles
!Session is a data flow with a particular destination
and transport-layer protocol
"Transport-layer contains protocol and destination port
!Concerns the treatment of reservations for
different senders with the same session
!Three styles are defined
"Wildcard-Iilter style (WE)
"Eixed-Iilter style (EE)
"Shared explicit style (SE)
Edward Jin-Ru Chen QoS 66
RSVP Style Definition
Shared Distinct
Wildcard-Filter
(WF) Styles
None defined Wildcard
Shared-Explicit
(SE) Style
Fixed-Filter
(FF) Style
Explicit
Reservation
Sender
Selection
34
Edward Jin-Ru Chen QoS 67
RSVP Example Configure

S1
S2, S3
(a)
(b)
(c)
(d)
R1
R2
R3
Edward Jin-Ru Chen QoS 68
WF Reservation Example
WF(*¦3B])
WF(*¦2B])
WF(*¦4B])
b
a
*¦3B]
*¦4B]
d d WF(*¦4B])
c c WF(*¦4B])
Receives Reserves Sends
35
Edward Jin-Ru Chen QoS 69
FF Reservation Example
FF(S1¦3B],
S3¦B])
FF(S1¦B])
FF(S1¦4B],
S2¦5B])
b
a
S1¦3B]
S3¦B]
S1¦4B]
S2¦5B]
d d
FF(S2 ¦5B],
S3¦B])
c c FF(S1¦4B])
Receives Reserves Sends
Edward Jin-Ru Chen QoS 70
SE Reservation Example
SE((S1,S3)¦
3B])
SE(S2¦2B])
SE( (S1,S2)
¦B])
b
a
(S1, S2, S3)
¦3B]
(S1, S2)¦B]
d d
SE((S2, S3)
¦3B])
c c SE(S1¦3B])
Receives Reserves Sends
36
Edward Jin-Ru Chen QoS 71
Differentiated Services
!Uses edge-based packet-marking, local per-class
forwarding behaviors and network provisioning to
support multiple service levels over an IP-based
network
!DiffServ concepts:
"DiIIServ codepoints (DSCP) in packet header indicate how
packet should be serviced at each hop
"DSCP marked at ingress based on analysis oI packet
"Intermediate routers/switches service the packets based on
the codepoints
Edward Jin-Ru Chen QoS 72
Why DiffServ?
!Simpler than RSVP/IntServ or ATM
"no signaling or per-flow state to maintain in network
"Scalable!!
!No change to applications
!Efficient for Core Routers
"couple of bits indicate forwarding treatment
"difficult 'high touch¨ work done at the network edge
!Interior Network Independence
"can be IP, ATM, Erame Relay, MPLS, mixture, etc.
!Different packet handling services and mappings possible:
"Service class indicator (e.g. premium and best-effort)
"Congestion Control low priority packets are discarded first
37
Edward Jin-Ru Chen QoS 73
DiffServ Philosophy
!Push complex/ heavy tasks to edges
"TraIIic conditioning TraIIic conditioning
# Marking, metering, policing, shaping Marking, metering, policing,
shaping
!Make the core case fast
!Assume core is secure
"Marking is trusted
!Use PHBs as building blocks for E2E service
"Myth alert!
Edward Jin-Ru Chen QoS 74
DiffServ Definitions
!Service - what is sold and delivered to customer
!DiffServ Codepoints (DSCP) - bits in packet
header that define the PHB the packet will receive
!Per-Hop Behavior (PHB) - Externally observable
forwarding treatment that packets with the same
DSCP receive from a network node
!Behavior Aggregate (BA)- group of packets with
the same DSCP crossing a link in a particular
direction
38
Edward Jin-Ru Chen QoS 75
DiffServ Definitions
!MF Classifier - examines multiple fields in packet header
!BA Classifier - examines just the DSCP in packet header
!Traffic Conditioning - functions such as policing, marking,
metering, shaping performed at network edge
!DS Boundary Device - positioned at ingress or egress of
DS domain
!DS Interior Device - operates in the core of a DS domain
Edward Jin-Ru Chen QoS 76
DiffServ SLA/TCA
!Traffic Conditioning Agreement (TCA): an agreement
specifying classifier rules and any corresponding traffic
profiles and metering, marking, discarding and/ or shaping
rules which are to apply to the traffic streams selected by
the classifier.
!Service Level Agreement (SLA): a service contract
between a customer and a service provider that specifies
the forwarding service a customer should receive. A
customer may be a user organization (source domain) or
another DS domain (upstream domain). A SLA may
include traffic conditioning rules which constitute a TCA
in whole or in part.
39
Edward Jin-Ru Chen QoS 77
DiffServ Network
Edward Jin-Ru Chen QoS 78
DS-field Format
!Differentiated Services Codepoint (DSCP)
"used to select the service (PHB) the packet will receive at
each DS-capable node
!formerly the IPv4 TOS and IPv6 Traffic Class
fields
!6 bits for DSCP, 2 bits are currently undefined
(ECN??)
!RFC2474
DSCP ECN
40
Edward Jin-Ru Chen QoS 79
DSCP Marking
!CIient may mark DiffServe Code Point (DSCP)
and may aIso mark 802.1P
!Layer 2 switch may mark 802.1P
!1st DiffServ router may mark DSCP using
"802.1P marking, VLAN, physical port, lP
source/destination addresses, lP protocol, TCP/UDP
source/destination ports
!Boarder router may mark/ re-mark
DSCP(using above criteria)
Edward Jin-Ru Chen QoS 80
DiffServ PHBs
!Default - best effort
!Expedited Forwarding (EF)
"low delay, latency, jitter service
"REC2598
!Assured Forwarding (AF)
"4 'relative¨ classes oI service
"3 level oI dropping precedence in each class
"REC2597
41
Edward Jin-Ru Chen QoS 81
EF PHB Definition
!EF PHB ensures a minimum departure rate
"Independently of any other traffic attempting to transit across the node
"DSCP: '101110¨
!EF PHB can be used to build a low loss, low latency, low
jitter, assured bandwidth, e2e service through DS domains
"Because it ensures that BA sees no (very small) queues. The
aggregate`s max arrival rate is less than that aggregate`s min departure
rate
"Strict policing at DS domain boundary (excess of contract must be
dropped!!!)
"Drops on the ingress policer and in the EE-PHB within the DS domain
indicate either denial of service attack or wrong configuration.
Edward Jin-Ru Chen QoS 82
EF PHB Behavior
!The departure rate of the aggregate's packets
from any diffserv node must equal or exceed a
configurable rate
!The configured minimum rate MUST be settable
by a network administrator
!If EF received unlimited preemption, rate limiter
must be implemented
"Priority queue is the example oI unlimited preemption
42
Edward Jin-Ru Chen QoS 83
AF DSCP Definition
!AF Class
"Class1: DSCP 001dd0
"Class2: DSCP 010dd0
"Class3: DSCP 011dd0
"Class4: DSCP 100dd0
!Dropping precedence (dd part)
"01: Low drop priority
"10: Medium drop priority
"11: High drop priority
Edward Jin-Ru Chen QoS 84
AF PHB Definition
!Offer different levels of forwarding assurances for
IP packets received from a customer DS domain
!4 independently forwarded AF classes
!Within each AF class, 3 levels of drop precedence
"Within each AE class, RED-like buIIer management is
used to implement drop precedence
43
Edward Jin-Ru Chen QoS 85
Assured Level
!How much forwarding resources has been
allocated to the AF class that the packet belongs to
!What is the current load of the AF class and in
case of congestion within the class
!What is the drop precedence of the packet
Edward Jin-Ru Chen QoS 86
AF Service Requirement
!Implement all four general use AF classes
"DiIIerent class packets are serviced independently
!Allocate a configurable, minimum amount of
forwarding resources to each AF class
"Resources contain buIIer space and bandwidth
!At least two different levels of loss probability
!Must not reorder packets belong to the same
microflow
44
Edward Jin-Ru Chen QoS 87
Other Codepints
!Best-effort
"DSCP: 000000
!Class Selector
"DSCP: xxx000
!Network control traffic
"DSCP: 11x000
Edward Jin-Ru Chen QoS 88
DiffServ Routers
!Edge router
"At the edge oI the DS domain
"Contains meter, classiIier, DSCP marker and
shaper/dropper
!Interior router
"Inside oI the DS domain
"Contains DS classiIier and PHB provider
45
Edward Jin-Ru Chen QoS 89
DiffServ Edge Router
!Classifier - MF or BA
!Meter - Measures traffic against profile
!Packet Marker - Marks DSCPs
!Shaper/ Dropper - Traffic Conditioners
ClassiIier
Meter
Marker Shaper/Dropper
Edward Jin-Ru Chen QoS 90
DiffServ Interior Router
!Classifier - BA only
!PHB - supported by queue
management/scheduling techniques
ClassiIier PHB
46
Edward Jin-Ru Chen QoS 91
DiffServ Configuration
!Manual setting
!Provided by policy server
"Policy Application defines the rules, filters, etc. of
DiffServ services Client
"LDAP - Lightweight Directory Access Protocol
"COPS - Common Open Policy Service Protocol
Edward Jin-Ru Chen QoS 92
Configuration Model
}z}jzy ,jpjpj,;;z;z;
}z}jzy ;z;vz; }z}jzy ;z;vz;
[j;zz;z;y
;z;vjzz


[zµ;z;

47
Edward Jin-Ru Chen QoS 93
LDAP Overview
!Protocol elements are carried directly over TCP or
other transport protocol
!Many protocol data elements are encoding as
ordinary strings
!Lightweight Basic Encoding Rules (BER)
encoding is used
Edward Jin-Ru Chen QoS 94
LDAP Protocol Model
!One of clients performing protocol operations
against servers
"Client transmits a protocol request describing the operation
to be perIormed to a server
"Server perIorms necessary operation on Directory
!No synchronous behavior are required
"Requests and responses Ior multiple operations may be
exchanged by client and servers in any order
48
Edward Jin-Ru Chen QoS 95
LDAP Operations
!Bind/Unbind
"Protocol session initial related operation
!Search
!Modify/Add/Delete
!Modify RDN
"Change the last component oI the name oI an entry
!Compare
!Abandon
Edward Jin-Ru Chen QoS 96
COPS Protocol
!Common Open Policy Service
"Client-server protocol Client- server protocol
"Outsource policy decisions to an external server
!Exchange policy information between a policy
server (Policy Decision Point or PDP) and its
clients (Policy Enforcement Points or PEPs)
!Begin with a simple but extensible design
49
Edward Jin-Ru Chen QoS 97
COPS Characteristics
!Employ a client/server model
!Use TCP as its transport protocol
!Created for the general administration, configuration, and
enforcement of policies
!Provide message level security
!Stateful in two main aspects
"Request/Decision state is shared between client and server
"State from various events may be inter-associated
!Allow the server to push/remove configuration information
to the client
Edward Jin-Ru Chen QoS 98
COPS Basic Model
PDP
Policy Server
Network Node
PEP
LPDP
COPS
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Edward Jin-Ru Chen QoS 99
Why Would DiffServ Succeed?
!Market Maturity
"DiIIerent era, customers, demands
"More sophisticated equipment
!Manageability & Provisioning
"ISP Peering (vs. exchange point)
"Policy based network management
"Automation oI provisioning