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Transcript of Internet and Overlay Networks Ram Keralapura ECE Dept [email protected].
Internet and Overlay NetworksInternet and Overlay Networks
Ram KeralapuraRam KeralapuraECE DeptECE Dept
[email protected]@ucdavis.edu
22
Layered ArchitectureLayered Architecture
Five main layersFive main layers• Application layerApplication layer• Transport layerTransport layer• Network (IP) layerNetwork (IP) layer• Link layerLink layer• Physical/Optical layerPhysical/Optical layer Optical switches
Optical fibers
Routers Virtual IP links
Applications/ComputersApplication layer links
33
IntroductionIntroduction
Internet Routing InfrastructureInternet Routing Infrastructure• Intra-domain routing (IGP) Intra-domain routing (IGP)
RIP, OSFP, ISIS, etc.RIP, OSFP, ISIS, etc.
• Inter-domain routing Inter-domain routing BGPBGP
Internet
Domain orAutonomous System
44
Intra-domain RoutingIntra-domain Routing
Links are assigned link costs/weightsLinks are assigned link costs/weights Path between two nodes inside a Path between two nodes inside a
domain follows shortest path (least domain follows shortest path (least cost path) cost path)
A
F E
B C
D
2
1
3
4
1
1
7
2
Dst A
F E
B C
D
55
Network PropertiesNetwork Properties
Important properties of networks that Important properties of networks that service providers look for:service providers look for:• ConnectivityConnectivity• PerformancePerformance• ResiliencyResiliency• Robustness in functionalityRobustness in functionality
Service availability – delivering a given Service availability – delivering a given packet from source to destinationpacket from source to destination
66
Characterizing NetworksCharacterizing Networks
Main causes for concern – resiliency Main causes for concern – resiliency and robustnessand robustness• How does the IGP protocol behave How does the IGP protocol behave
during network component failures?during network component failures?• How does the behavior impact the data How does the behavior impact the data
that the network carries?that the network carries?
77
Characterizing Networks (cont’d)Characterizing Networks (cont’d)
We have developed a model that We have developed a model that captures the dynamic behavior of the captures the dynamic behavior of the network protocols during link failures network protocols during link failures [Keralapura et al, 2004][Keralapura et al, 2004]
Protocol convergence depends on:Protocol convergence depends on:• Topology – nodes and connectivityTopology – nodes and connectivity• Protocol timer settingsProtocol timer settings• Number of entries to update in the Number of entries to update in the
forwarding tablesforwarding tables
88
Characterizing Networks (cont’d)Characterizing Networks (cont’d)
Metrics for service availabilityMetrics for service availability• Service disruption timeService disruption time• Traffic disruptionTraffic disruption
Based on the above metrics we Based on the above metrics we define “goodness factor” for the define “goodness factor” for the networknetwork
99
Results (cont’d)Results (cont’d)
Static properties (like node out-degree) do not capture operational conditions and network dynamics
Out Degree
Out Degree
Ingre
ss N
ode G
oodness
Ingre
ss N
ode G
oodness
1010
Network Diameter
Netw
ork
Goodness
Similar results were also found in the paper “Layered Complex Networks” by Kurant and Thiran
1111
Internet ArchitectureInternet Architecture
Tiered hierarchy in domainsTiered hierarchy in domains
Tier-1
A
Tier-1
A
Tier-1
B
Tier-1
B
Tier-2C
Tier-2C
Tier-2D
Tier-2D Tier-2
E
Tier-2E
Tier-2F
Tier-2F
Peering relationship
Customer-Provider relationship
1212
Inter-domain routingInter-domain routing
Policy-based routingPolicy-based routing• Ad-hoc and can change with agreements Ad-hoc and can change with agreements
with other domainswith other domains Can we capture these policies?Can we capture these policies?
• Domains do not disclose their connectivityDomains do not disclose their connectivity Policies can obstruct views and hinder Policies can obstruct views and hinder
domain-level topology discoverydomain-level topology discovery• Need multiple vantage points for more Need multiple vantage points for more
accurate topology informationaccurate topology information
1313
Application Layer NetworksApplication Layer Networks
Email NetworksEmail Networks World Wide Web (WWW)World Wide Web (WWW) Peer-to-Peer (p2p) NetworksPeer-to-Peer (p2p) Networks Several Content Delivery Networks Several Content Delivery Networks
(CDN)(CDN)
Overlay networks
1414
Background: Overlay NetworksBackground: Overlay Networks
A
A’
X
B
C
D
Y
C’
B’
D’
Domain-1
Domain-2
Domain-3
Domain-4
1515
Interaction between networksInteraction between networks
Overlay networks compete with IP Overlay networks compete with IP networks to provide routing servicenetworks to provide routing service
IP and overlay networks are unaware IP and overlay networks are unaware of key things happening at the other of key things happening at the other layerlayer
Multiple overlay networks co-exist Multiple overlay networks co-exist and make independent decisionsand make independent decisions
How does all this affect IP and How does all this affect IP and overlay networks?overlay networks?
1616
Interactions between NetworksInteractions between Networks
Identified some potential interactions Identified some potential interactions [Keralapura et al, 2005][Keralapura et al, 2005]• Traffic engineering in IP networksTraffic engineering in IP networks
Load balancing issuesLoad balancing issues IP layer traffic matrix estimationIP layer traffic matrix estimation
• Coupling of multiple domainsCoupling of multiple domains Defeats the objective of BGPDefeats the objective of BGP
• Multiple co-existing overlay networksMultiple co-existing overlay networks Traffic oscillationsTraffic oscillations Cascading reactionsCascading reactions
1717
A
BD
C
E
HG
F
NM
5
20
8
8
5
5
5 5
5
5
5 5
55
Load Balancing and TM EstimationLoad Balancing and TM Estimation
1818
Coupling Multiple AS DomainsCoupling Multiple AS Domains
A E
Domain-1 Domain-2
B
C
D H
F
GX
Defeats one of the objectives of BGP to decouple different domains
1919
Traffic OscillationsTraffic Oscillations
Time (ms)
Link
Util
izat
ion
Failure of link 10-12 Failure of link 2-5
Traffic Oscillations
2020
Open questionsOpen questions
Interactions need to be understood Interactions need to be understood better and we need to model thembetter and we need to model them
How to go about characterizing the How to go about characterizing the robustness of a network after we robustness of a network after we model such interactions?model such interactions?
Are there interactions between Are there interactions between networks at other layers?networks at other layers?• If yes, then how to we qualify, quantify, If yes, then how to we qualify, quantify,
and model them?and model them?