DiffServ

1
DiffServ

• An Overview
• Jean WalrandEECS

2
Outline

• DiffServ
• Goal
• Solution
• Worst Case Admission Control
• Measurement-Based Admission Control
• Bandwidth Allocation
• A Note on CoS
• Notes on Smart Networks Project

3
DiffServ

• Goal

• CoS without per-connection state

• Solution

• No route-pinning (OSPF-BGP routing)
• Planning and operations based on aggregate
  statistics and worst-case routing
• Peer-to-peer SLAs that specify total rate but not
  traffic destination

4
DiffServ (continued)
Policing Shaping
5
DiffServ (continued)
DiffServ SLA Worst Case Admission Control
Ingress 3
Ingress 3
Ingress 1
Ingress 1
Ingress 2
Ingress 2
Worst Case
Typical Case
Terribly wasteful!
6
DiffServ (continued)
Worst Case R ? 10

• Example

R
Symmetric Case R ? 20
10
R
Worst Case, 1F R ? 5
10
Symm. Case, 1F R ? 10
10
R
7
DiffServ (continued)
DiffServ SLA Measurement-Based Admission Control
Admit if peak(new) lt Gap at all times
8
Bandwidth Allocation

• Problems
• How to share bandwidth
• How to renegotiate SLAs
• Issues
• Scalability
• Efficiency
• Fairness, Optimality, ...

9
Bandwidth Allocation (cd)
Sharing one link
10
Bandwidth Allocation (cd)
Dynamic
11
Bandwidth Allocation (cd)
N1
N2
Admission policies SLAs (Committed Access Rates)
Static
12
Bandwidth Allocation (cd)
13
Bandwidth Allocation (cd)
Closer Look
Assume Poisson demands, i.i.d. holding times ...
For large links, the variance is small. gt
Static ? Dynamic
However, rates change gt must adapt
14
Bandwidth Allocation (cd)
Proposed Adaptation Scheme Renegotiate
blocks of permits based on thresholds
4
5
15
20
6
7
5
6
7
40
15
Bandwidth Allocation (cd)

• Economic Model

Cost(rate)
Cost(rate)
Cost(rate)
Computation
Marginal Costs
16
Bandwidth Allocation (cd)

• Economic Model (cd)

Recursive calculation of preferred path and
its marginal cost.
17
Note on CoS

• Model TCP/DRR

Without DRR
y
p
x
C
y
1 - p
With DRR
RTTx gtgt RTTy
x
C
pC
18
Tools for Smart Networks Project

• Joint UCB - Cisco Project
• DARPA Funding Cisco
• Combines

• Measurements
• Analysis Simulation
• Real-time Control

• Objective Product

19
What are Smart Networks?
Modify
Analyze
Measure