A Differentiated Services Architecture for the Internet

1
A Differentiated Services Architecture for the
Internet

• References
• - K. Nichols, V. Jacobson, L. Zhang
• - D. Clark, J. Wroclawski
• Presented by Liping Zhang

2
Overview

• Introduction
• Two different service types implementation and
  problems
• Two-bit differentiated services architecture
• Problems with end-end bandwidth allocation based
  on level of marked traffic
• Discussion

3
Introduction

• Why do we need differentiated services?
• Different users
• Different applications
• Service allocation
• For example, one goal of assured service is to
  allocate the bandwidth of the Internet to
  different users in a controlled way during
  periods of congestion

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How to describe a service

• What is provided to the customer
• E.g., 1 Mbps, continuously available
• To where is this service provided
• A single destination
• A group
• All nodes on local provider
• Everywhere
• Level of assurance provided to service
• What level of performance uncertainty can user
  tolerate

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Two distinct service types

• Assured service
• D. Clark
• Premium service
• V. Jacobson

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Assured service

• Provide different levels of best-effort service
  at times of network congestion
• Expected capacity
• In packets unlikely to be dropped
• Out packets - no assurance
• Queuing
• Best effort

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Mechanism for assured service
Counter
Counter
Out- and in- dropper
First-hop
Host
Marking packets according to the service profile
RIO scheme, packets are treated preferentially
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RIO algorithm

• RED - Random Early Detection
• Packets dropped with low but increasing
  probability as queue grows instead of waiting
  until it is full and dropping all new packets
• RIO
• Run two RED algorithms for in and out with
  different dropping frequencies

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Premium service

• Fundamentally different Internet best effort
  service - high priority traffic has its own queue
  in routers
• Shaped, hard-limited to provisioned peak rate
• No bursts are injected into net
• Virtual wire, available whenever needed
• Regular flow pattern, no queuing
• Shared, with best-effort

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Mechanism for premium service
Intra-network
Host
Router
First-hop
H-Q premium, no dropping L-Q best effort,
dropping on congestion
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Two-bit differentiated services architecture

• Deploying both services
• More bits available in IP header, why not both
• Forwarding path mechanisms
• Leaf routers
• Input interface a traffic profile
• Output interface two queues (HQ, LQ)
• Intermediate routers
• Only have forwarding function
• Border routers
• A Profile Meter at the input interface

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Traffic flow from end-host to ISP
Company A
Internal Router
Host
2
Border Router
1
First-hop Router
3
ISP
Border Router
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Forwarding path primitives

• General classifier
• In leaf routers, transport-level signature
  matching
• Bit-pattern classifier
• Performs a two-way decision based on bit-pattern
• Bit setter
• A- and P-bits must be set or cleared in several
  places
• Priority queues
• Shaping token bucket
• At the leaf router for Premium traffic
• Policing token bucket
• At border router, for both P and A services

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Block diagram of leaf router input functionality
Marker 1
Flow1
Flow N
Arriving packet
Marker N
Forwarding Engine
Packet Classifier
Clear AP bits
Best Effort
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Markers to implement the two different services
Wait for token
Set P bit
Packet Input
N
Test if token
Set A bit
Packet Input
Y
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Router output interface for two-bit architecture
P-bit set?
High-priority
No
If A-bit set? Inc a_cnt
Low-priority
If A-bit set? dec a_cnt
RIO queue management
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Border router input interface Profile Meters
Token available ?
Clear A bit
N
A set
Y
Forwarding Engine
Is packet marked ?
Not marked
Y
P set
N
Token Available
Drop Packet
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Passing configuration information

• Request to the leaf router
• Average rate, burst, service type (P or A)
• Ways of passing the message
• RSVP, SNMP, network administrator
• Authenticating the sender

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Architectural framework for marked traffic
allocation

• Preconfiguring of usage profiles is practical
• Paying for level of service that is always
  available
• Allocation follows organizational hierarchies
• Each organization must be responsible for its DM
• Only bilateral agreements work

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Bandwidth Brokers (BB)

• Roles
• Allocating and controlling bandwidth shares
• Responsibilities
• Parcel out a regions marked traffic allocation
  and set up the leaf routers within the local
  domain
• Managing messages sent across boundaries to
  adjacent region BBs

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Examples

• A statically configured example with no BB
  message exchanged
• A statically configured example with BB messages
  exchanged
• Dynamic allocation and additional mechanism

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RSVP and BBs

• Existing bilateral relations between BBs of
  adjacent trust regions are necessary for resource
  allocation
• A few bits in the packet header are used to mark
  the service class
• RSVP resource setup hop-by-hop
• Use RSVP between two adjacent ISPs (BB1/BR1 and
  BB2/BR2)

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Discussion

• Extensibility of the current 2-bit architecture
• Service allocation for multicast
• Who should request the service
• Sender or receiver
• Deployment issues
• Security issues

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2-bit differentiated services architecture

• Providing Controlled-Load and Guaranteed service
• P service for C-L service
• A constrained case of C-L service
• P service for G service
• The service model of P service fits G service
  model