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Internet and Overlay Networks. Ram Keralapura ECE Dept rkeralapura@ucdavis.edu. Layered Architecture. Five main layers Application layer Transport layer Network (IP) layer Link layer Physical/Optical layer. Applications/Computers Application layer links. Routers Virtual IP links.

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internet and overlay networks

Internet and Overlay Networks

Ram Keralapura

ECE Dept

rkeralapura@ucdavis.edu

layered architecture
Layered Architecture
  • Five main layers
    • Application layer
    • Transport layer
    • Network (IP) layer
    • Link layer
    • Physical/Optical layer

Applications/Computers

Application layer links

Routers

Virtual IP links

Optical switches

Optical fibers

introduction
Introduction
  • Internet Routing Infrastructure
    • Intra-domain routing (IGP)
      • RIP, OSFP, ISIS, etc.
    • Inter-domain routing
      • BGP

Internet

Domain or

Autonomous System

intra domain routing

4

B

C

B

C

2

2

A

D

A

3

7

Dst

D

1

1

F

E

F

E

1

Intra-domain Routing
  • Links are assigned link costs/weights
  • Path between two nodes inside a domain follows shortest path (least cost path)
network properties
Network Properties
  • Important properties of networks that service providers look for:
    • Connectivity
    • Performance
    • Resiliency
    • Robustness in functionality
      • Service availability – delivering a given packet from source to destination
characterizing networks
Characterizing Networks
  • Main causes for concern – resiliency and robustness
    • How does the IGP protocol behave during network component failures?
    • How does the behavior impact the data that the network carries?
characterizing networks cont d
Characterizing Networks (cont’d)
  • We have developed a model that captures the dynamic behavior of the network protocols during link failures [Keralapura et al, 2004]
  • Protocol convergence depends on:
    • Topology – nodes and connectivity
    • Protocol timer settings
    • Number of entries to update in the forwarding tables
characterizing networks cont d1
Characterizing Networks (cont’d)
  • Metrics for service availability
    • Service disruption time
    • Traffic disruption
  • Based on the above metrics we define “goodness factor” for the network
results cont d
Results (cont’d)

Ingress Node Goodness

Static properties (like node out-degree) do not capture

operational conditions and network dynamics

Out Degree

Ingress Node Goodness

Out Degree

slide10

Network Goodness

Network Diameter

Similar results were also found in the paper

“Layered Complex Networks” by Kurant and Thiran

internet architecture
Internet Architecture
  • Tiered hierarchy in domains

Peering relationship

Tier-1

B

Tier-1

A

Tier-2

C

Tier-2

D

Tier-2

F

Tier-2

E

Customer-Provider relationship

inter domain routing
Inter-domain routing
  • Policy-based routing
    • Ad-hoc and can change with agreements with other domains
  • Can we capture these policies?
    • Domains do not disclose their connectivity
  • Policies can obstruct views and hinder domain-level topology discovery
    • Need multiple vantage points for more accurate topology information
application layer networks
Application Layer Networks
  • Email Networks
  • World Wide Web (WWW)
  • Peer-to-Peer (p2p) Networks
  • Several Content Delivery Networks (CDN)

Overlay networks

background overlay networks
Background: Overlay Networks

B’

D’

Domain-2

A’

B

Y

X

D

C’

A

Domain-4

Domain-1

Domain-3

C

interaction between networks
Interaction between networks
  • Overlay networks compete with IP networks to provide routing service
  • IP and overlay networks are unaware of key things happening at the other layer
  • Multiple overlay networks co-exist and make independent decisions
  • How does all this affect IP and overlay networks?
interactions between networks
Interactions between Networks
  • Identified some potential interactions [Keralapura et al, 2005]
    • Traffic engineering in IP networks
      • Load balancing issues
      • IP layer traffic matrix estimation
    • Coupling of multiple domains
      • Defeats the objective of BGP
    • Multiple co-existing overlay networks
      • Traffic oscillations
      • Cascading reactions
load balancing and tm estimation
Load Balancing and TM Estimation

F

5

5

G

H

5

5

5

8

M

N

5

A

E

20

5

8

5

5

B

D

5

5

C

coupling multiple as domains
Coupling Multiple AS Domains

F

B

X

G

C

E

A

H

D

Domain-2

Domain-1

Defeats one of the objectives of BGP to decouple different domains

traffic oscillations

Link Utilization

Time (ms)

Traffic Oscillations

Traffic Oscillations

Failure of link 10-12

Failure of link 2-5

open questions
Open questions
  • Interactions need to be understood better and we need to model them
  • How to go about characterizing the robustness of a network after we model such interactions?
  • Are there interactions between networks at other layers?
    • If yes, then how to we qualify, quantify, and model them?