Quality of Service in Dynamic Source Routing DSR

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Quality of Service in Dynamic Source Routing
(DSR)
QoS modifications in DSR Pizza
Talk 05/14/01
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People Involved

• Dr. David B. Johnson
• Amit Kumar Saha
• Yih-Chun Hu

QoS modifications in DSR
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Outline of the talk

• Basic DSR protocol and its drawbacks
• Flow-State changes
• Data Structure
• Logic
• How Flow-State framework is used to get QoS
• Current status
• Performance evaluation for simple cases

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Basic mechanism of DSR

• On demand route-discovery
• On demand route-maintenance
• Data packet has complete sequence of hops
• Various kinds of optimizations made

QoS modifications in DSR
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Animation of DSR
B
C
D
S
S,B,C
Broadcast ROUTE REQUEST
S
S,B
Route Discovery
S,B,C,D
S,B,C,D
S,B,C,D
Unicast ROUTE REPLY
S,(B),C,D
S,B,(C),D
S,B,C,(D)
Data Received
Data sent
C moves away
Route Maintenance
S,(B),C,D
S,B,(C),D
Data sent
Forwarding fails
B -gt C dead
ROUTE ERROR
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Drawbacks of DSR

• High routing overhead
• More collision
• More dropped packets
• Less effective throughput
• Does not have support for better-than-best-effort
  QoS.

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Flow-State extensions

• Constant routing overhead for most packets
• Provides a framework for supporting QoS

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Basic steps in Flow-State

• Flow establishment
• Receiving and forwarding establishment packets
• Sending packets along established flows
• Receiving and forwarding packets along
  established flows

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Basic steps in Flow-State

• Error Processing
• Automatic Route Shortening
• Loop Detection
• Rate Limiting

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Animation of Flow-State
B
C
D
S
S,B,C
Broadcast ROUTE REQUEST
S
S,B
Route Discovery
S,B,C,D
S,B,C,D
S,B,C,D
Unicast ROUTE REPLY
S,(B),C,DFlow1
S,B,(C),DFlow1
S,B,C,(D)Flow1
Data Received
Data sent
Flow1
Flow1
Flow1
Data sent
Data Received
Route Maintenance
C moves away
Flow1
Flow1
Data sent
Flow1,error
FLOW ERROR
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Data structures for Flow-State
Flow Table

• Previous hop
• Source Route
• Next hop in range
• Last used time

• IP Source
• IP Destination
• Flow ID
• Outgoing interface
• Outgoing MAC
• Hop Count
• Expected TTL
• Default flow or not

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Data structures for Flow-State
Automatic Route Shortening Table

• IP Source
• IP Destination
• Flow ID

ltpacket, shortened routegt
ltpacket, shortened routegt
ltpacket, shortened routegt
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Data structures for Flow-State
Default Flow ID Table

• IP Source
• IP Destination
• Largest odd Flow ID
• Current Flow ID
• Current Flow ID valid or not

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Using Flow-State to support QoS
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Explicit resource management
Flow ID
Resource Identifier
Minimum Required value for the resource
Desired value for the resource

• Resource
• Interface Q Length
• Rate of Interface Q draining
• Quiet time fraction
• Packet Loss Rate

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Resource Promise
Source asks for resources during flow
establishment
Yes
No
Can I keep the request ?
Tentatively set aside resource
Return Error
Stop Propagating Request
Update desired value
Forward packet towards destination node
Request could be integrated with route request
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Breaking a promise

• Notify the node to which the promise was made
• Minimum set of promises to be broken
• Optimistic Forwarding of packets containing
  indication of a break in promise.

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Present Status

• Flow State modifications have been made
• Debugging stage Completed
• Generating interesting scenarios
• Running simulations
• QoS logic yet to be added

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Performance results
Scenario 1
Un-reachable
Reachable
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2
3
4
5
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• Complete graph
• 512B packets
• CBR at 0.25s interval

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Packet Delivery
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Drops and Collisions
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Bytes transferred
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Thats all folks
QoS modifications in DSR