Title Slide

1
Providing Guaranteed Services Without Per Flow
Management
By Ion Stoica, Hui Zhang Presented by Sanjeev
R. Kulkarni
2
Outline

• Problems with the current QoS architectures
• Stateless Core Architecture(SCORE)
• Dynamic Packet State
• Core Jitter Virtual Clock Algorithm
• Admission Control
• Implementation details
• Extensions to IPv6

3
Current QoS architectures

• Integrated Services
• Differentiated Services

4
Integrated Services

• All Routers maintain per-flow state
• State
• Control Plane
• Admission Control per flow signaling
• Data Plane
• Classifier per flow flow-ids
• scheduler per flow scheduling algorithm
  parameters

5
Integrated Services

• All Routers maintain per-flow state
• State
• Control Plane
• Admission Control per flow signaling
• Data Plane
• Classifier per flow flow-ids
• scheduler per flow scheduling algorithm
  parameters
• Scalability??

6
Jitter Virtual Clock

• For each packet
• eligible time
• deadline
• Scheduling done in the order of the deadline
• e1i,j a1i,j
• eki,j max ( aki,j gki,j-1, dk-1i,j)
• dki,j eki,j lki/ri

7
Core-routers and Edge routers
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Differentiated Services

• A small number of traffic classes
• Only Edge routers maintain per flow state
• Control Plane
• Admission Control per flow signaling
• Data Plane
• Classifier per class classification
• Scheduler per class scheduling

9
Differentiated Services

• A small number of traffic classes
• Only Edge routers maintain per flow state
• Control Plane
• Admission Control per flow signaling
• Data Plane
• Classifier per class classification
• Scheduler per class scheduling
• Quality of QoS??

10
Stateless Core Solution

• Idea similar to DiffServ
• Only Edge Routers maintain per flow state
• Dynamic Packet State (DPS) is inserted into each
  packet by edge routers
• Core routers update DPS and schedule packets
  accordingly

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DPS
Ingress
Egress
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How it works
a
b
c
d
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How it works
a
b
c
d
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How it works
a
b
c
d
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How it works
a
b
c
d
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How it works
a
b
c
d
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How it works
a
b
c
d
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How it differs from DiffServ

• DPS versus Per Hop Behavior (PHB)
• DPS is dynamic
• Routers change DPS and schedule packets based on
  the DPS state
• DPS change mirrors a Core-Jitter Virtual Clock
  scheduling

19
Core Jitter Virtual Clock

• eki,j max ( aki,j gki,j-1, dk-1i,j)
• The main culprit is dk-1i,j
• Introduce a slack variable such that
• aki,j gki,j-1 gt dk-1i,j

ik max (0, ik-1 (lik-1 - lik)/ri -
(ei,1k - ei,1k-1 - lik-1/ri)/(h-1) )
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Example
a
b
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Example
a
ea1
da1
b
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Example
ga1
a
ea1
da1
b
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Example
ga1
a
ea1
da1
eb1
db1
b
ga1
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Example
a
ea1
da1
eb1
db1
b
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Example
a
ea1
ea2
da2
eb1
db1
b
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Example
a
ea2
da2
eb1
db1
b
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Example
a
ea2
da2
gb1
eb1
b
db1
ga1
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The algorithm

• Parameter Initialization by Ingress Routers
• Core routers examine the parameters and modify g
• Egress Routers strip the packet of these labels

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Admission Control
r
s
d
a
c
b
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Admission Control
Resv
r
s
d
a
c
b
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Admission Control
r
s
d
1
a
c
b
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Admission Control
r
s
d
a
c
b
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Admission Control
r
s
d
a
c
b
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Admission Control
r
s
d
a
c
b
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Admission Control
r
s
d
3
a
c
b
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Admission Control
Resv
r
s
d
a
c
b
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Admission Control

• Each core router maintains an upper bound R on
  the Total Bandwidth reserved
• Local Admission Control
• Accept if R ri lt C
• Periodically they run an algorithm that contains
  the deviation between the actual B/w reserved and
  R.

38
Recalibration Algorithm

• Packet state b
• Add all b values on each packet arrival
• Periodically they update based on
• R min ( R, RD/(1-f) Rnew )

39
Implementation
0
31
15
7
11
TOS
IPv4 Header
Frag Offset
18
40
Implementation
0
31
15
7
11
18
F1
F2
F3
Flag
2
5
9
16
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Extension to Ipv6
0
7
11
31
Flow Label
F1
F2
F3
Flag
6
11
19
2
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Summary

• SCORE Network
• Is Scalable
• Gives a QoS similar to Jitter Virtual Clock
• Extensible to Ipv6
• Transparent to the outside network