a network-state management service · 2014-12-10 · a network-state management service peng sun...
TRANSCRIPT
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A Network-State Management Service
Peng SunRatul Mahajan, Jennifer Rexford,
Lihua Yuan, Ming Zhang, Ahsan ArefinPrinceton & Microsoft
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Complex Infrastructure
1
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Complex Infrastructure
1
Number of 2010
Data Center A few
NetworkDevice 1,000s
NetworkCapacity 10s of Tbps
Microsoft Azure
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Complex Infrastructure
1
Number of 2010 2014
Data Center A few 10s
NetworkDevice 1,000s 10s of 1,000s
NetworkCapacity 10s of Tbps Pbps
Microsoft Azure
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Complex Infrastructure
Variety of vendors/models/time1
Number of 2010 2014
Data Center A few 10s
NetworkDevice 1,000s 10s of 1,000s
NetworkCapacity 10s of Tbps Pbps
Microsoft Azure
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Management Applications
2
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Management Applications
2
Traffic Engineering
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Management Applications
2
Traffic Engineering
Load Balancing
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Management Applications
2
Traffic Engineering
Load Balancing Link
Corruption Mitigation
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Management Applications
2
Traffic Engineering
Load Balancing Link
Corruption MitigationDevice
Firmware Upgrade
……
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Our Question
How to safely run multiple management applications on shared infrastructure
3
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Naïve Solution
• Run independently
4
Traffic Engineering
Link Corruption Mitigation
Firmware Upgrade
Network Devices
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• It does not work due to 2 problems
Naïve Solution
4
Traffic Engineering
Link Corruption Mitigation
Firmware Upgrade
Network Devices
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AggA
ToRs
AggB
Core1 2
Problem #1: Conflict
5
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AggA
ToRs
AggB
Core1 2
Problem #1: Conflict
5
Link-corruption-mitigation adjusts traffic away from Core1
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AggA
ToRs
AggB
Core1 2
Problem #1: Conflict
5
Link-corruption-mitigation adjusts traffic away from Core1
TE tunes traffic among links to Core1, 2
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AggA
ToRs
AggB
Core1 2
Problem #2: Safety Violation
6
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AggA
ToRs
AggB
Core1 2
Problem #2: Safety Violation
6
Link-corruption-mitigation shuts down faulty Agg A
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AggA
ToRs
AggB
Core1 2
Problem #2: Safety Violation
6
Link-corruption-mitigation shuts down faulty Agg A
Firmware-upgrade schedules Agg B to upgrade
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Potential Solution #1
7
Traffic Engineering
Firmware Upgrade
Link Corruption Mitigation
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Potential Solution #1
• One monolithic application
7
Traffic Engineering
Firmware Upgrade
Link Corruption Mitigation
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Potential Solution #1
• One monolithic application
• Central control of all actions
7
Traffic Engineering
Firmware Upgrade
Link Corruption Mitigation
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Too Complex to Build
• Difficult to develop• Combine all applications that are
already individually complicated
8
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Too Complex to Build
• Difficult to develop• Combine all applications that are
already individually complicated
• High maintenance cost• for such huge software in practice
8
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Potential Solution #2
9
Traffic Engineering
Firmware Upgrade
Link Corruption Mitigation
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Potential Solution #2• Explicit coordination among
applications
9
Traffic Engineering
Firmware Upgrade
Link Corruption Mitigation
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Potential Solution #2• Explicit coordination among
applications
• Consensus over network changes
9
Traffic Engineering
Firmware Upgrade
Link Corruption Mitigation
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Still Too Complex
• Hard to understand each other• Diverse network interactions
10
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Still Too Complex
• Hard to understand each other• Diverse network interactions
10
Application Routing Device Config
TrafficEngineering
Firmwareupgrade
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Still Too Complex
• Hard to understand each other• Diverse network interactions
10
Application Routing Device Config
TrafficEngineering
Firmwareupgrade
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Still Too Complex
• Hard to understand each other• Diverse network interactions
10
Application Routing Device Config
TrafficEngineering
Firmwareupgrade
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Main Enemy: Complexity
• Application development
• Application coordination
11
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Main Enemy: Complexity
• Application development
• Application coordination
11
MonolithicIndepen-dent
Explicitlycoordinate
Simple Complex
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What We Advocate
• Loose coupling of applications
• Design principle:• Simplicity with safety guarantees
12
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What We Advocate
• Loose coupling of applications
• Design principle:• Simplicity with safety guarantees
• Forgo joint optimization• Worthwhile tradeoff for simplicity• Applications could do it out-of-band
12
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Overview of Statesman
• Network operating system for safe multi-application operation
13
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Overview of Statesman
• Network operating system for safe multi-application operation
• Uses network state abstraction• Three views of network state
13
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Overview of Statesman
• Network operating system for safe multi-application operation
• Uses network state abstraction• Three views of network state• Dependency model of states
13
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The “State” in Statesman
• Complexity of dealing with devices• Heterogeneity• Device-specific commands
14
Network Devices
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The “State” in Statesman
• Complexity of dealing with devices• Heterogeneity• Device-specific commands
14
Network Devices
Network State
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State Variable Examples
State Variable Value
Device Power Status Up, down
Device Firmware Version number
Device SDN Agent Boot Up, down
Device Routing State Routing rules
Link Admin Status Up, down
Link Control Plane BGP, OpenFlow, …15
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Simplify Device InteractionPast Now
16
Network Devices Network Devices
Network State
Application Application
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Simplify Device InteractionPast Now
16
SNMP, OF, vendor API, …
Network Devices Network Devices
Network State
Application
Device Statistics
Application
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Simplify Device InteractionPast Now
16
SNMP, OF, vendor API, …
Network Devices Network Devices
Network State
Application
Device Statistics
Application
Device-specificcmds
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Simplify Device InteractionPast Now
16
SNMP, OF, vendor API, …
Read
Network Devices Network Devices
Network State
Application
Device Statistics
Application
Device-specificcmds
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Simplify Device InteractionPast Now
16
SNMP, OF, vendor API, …
Read Write
Network Devices Network Devices
Network State
Application
Device Statistics
Application
Device-specificcmds
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Views of Network State
17Network Devices
Network State
ApplicationApplicationApplication
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Views of Network State
17Network Devices
Observed State
Observed State Actual state of the whole network
Target State Desired state to be updated on the whole network
Target State
ApplicationApplicationApplication
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Network Devices
Two Views Are Not Enough
18
Observed State
Target State
ApplicationApplicationApplication
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Network Devices
Two Views Are Not Enough
18
Observed State
Target State
One More View
Proposed State A group of entity-variable-valuesdesired by an application
Proposed State
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Network Devices
Two Views Are Not Enough
18
Observed State
Target State
One More View
Proposed State A group of entity-variable-valuesdesired by an application
Proposed State
ApplicationApplicationApplication
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Network Devices
Two Views Are Not Enough
18
Observed State
Target State
One More View
Proposed State A group of entity-variable-valuesdesired by an application
Proposed State
ApplicationApplicationApplication
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How Merging Works• Combine multiple proposed states
into a safe target state
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How Merging Works• Combine multiple proposed states
into a safe target state
• Conflict resolution• Last-writer-wins• Priority-based locking• Sufficient for current deployment
19
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How Merging Works• Combine multiple proposed states
into a safe target state
• Conflict resolution• Last-writer-wins• Priority-based locking• Sufficient for current deployment
• Safety invariant checking• Partial rejection & Skip update
19
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Choose Safety Invariants
20
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Choose Safety Invariants
20
TightLoose
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Choose Safety Invariants
20
Hinder application too frequently
TightLoose
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Choose Safety Invariants
20
Hinder application too frequently
TightLoose
Cannot protect network operation
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Choose Safety Invariants
• Our current choice• Connectivity: Every pair of ToRs in
one DC is connected• Capacity: 99% of ToR pairs have at
least 50% capacity
20
Hinder application too frequently
TightLoose
Cannot protect network operation
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Recap of Three-View Model• Simplify network management
21
Observed State
Target StateProposed
State
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Recap of Three-View Model• Simplify network management
21
Observed State
Target StateProposed
State
ApplicationApplicationApplication
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Recap of Three-View Model• Simplify network management
21
Observed State
Target StateProposed
State
What we see from
the network
ApplicationApplicationApplication
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Recap of Three-View Model• Simplify network management
21
Observed State
Target StateProposed
State
What we see from
the network
What we want the network
to be
ApplicationApplicationApplication
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Recap of Three-View Model• Simplify network management
21
Observed State
Target StateProposed
State
What we see from
the network
What we want the network
to be
What can be actually done on the network
StatesmanApplicationApplicationApplication
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Yet Another Problem
• What’s in Proposed State• Small number of state variables that
application cares
22
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Yet Another Problem
• What’s in Proposed State• Small number of state variables that
application cares
• Implicit conflicts arises
22
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Yet Another Problem
• What’s in Proposed State• Small number of state variables that
application cares
• Implicit conflicts arises• Caused by state dependency
22
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Implicit Conflict
23
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A
B C
D
Implicit Conflict
23
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A
B C
D
Implicit Conflict
23
TE writes new value of routing state of B for tunneling traffic
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A
B C
D
Implicit Conflict
23
TE writes new value of routing state of B for tunneling traffic
Firmware-upgrade writes new value of firmware state of B
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Dependency Relations
24
Device
Link
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Dependency Relations
24
PowerState Device
Link
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Dependency Relations
24
PowerState
FirmwareVersion
Device
Link
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Dependency Relations
24
PowerState
FirmwareVersion
ConfigurationState
Device
Link
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Dependency Relations
24
PowerState
FirmwareVersion
ConfigurationState
Device
Link
bgpd SDN
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Dependency Relations
24
PowerState
FirmwareVersion
ConfigurationState AdminState
ConfigurationState
Device
Link
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Dependency Relations
24
PowerState
FirmwareVersion
ConfigurationState
RoutingState
AdminState
ConfigurationState
Device
Link
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Dependency Relations
24
PowerState
FirmwareVersion
ConfigurationState
RoutingState
AdminState
ConfigurationState
PathState
Device
Link
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Build in Dependency Model
• Statesman calculates it internally
• Only exposes the result for each state variable• Whether the variable is controllable
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Statesman System
26
TargetState
Proposed State
Observed State
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Statesman System
26
TargetState
Proposed State
Observed State
Storage Service
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Statesman System
26
TargetState
Monitor
Proposed State
Observed State
Storage Service
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Statesman System
26
TargetState
Monitor
Checker
Proposed State
Observed State
Storage Service
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Statesman System
26
TargetState
Monitor Updater
Checker
Proposed State
Observed State
Storage Service
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Deployment Overview
• Operational in Microsoft Azure for 12 months
• Cover 10 DCs of 20K devices
27
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Deployment Overview
• Operational in Microsoft Azure for 12 months
• Cover 10 DCs of 20K devices
27
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Production Applications
• 3 diverse applications built• Device firmware upgrade• Link corruption mitigation• Traffic engineering
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Production Applications
• 3 diverse applications built• Device firmware upgrade• Link corruption mitigation• Traffic engineering
• Finish within months
• Only thousands of lines of code
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Case #1: Resolve ConflictInter-DC TE &
Firmware-upgrade
29
BR 1
BR 2DC 1
BR 8
BR 7DC 4
BR 3BR 4
DC 2
BR 5
DC 3
BR 6
DC = Data CenterBR = Border Router
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……
……
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……
……
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Firmware-upgrade acquires lock of BR1
……
……
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TE fails to acquire lock, and moves traffic away
……
……
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TE fails to acquire lock, and moves traffic away
……
……
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BR1 firmware upgrade starts
……
……
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BR1 firmware upgrade starts
BR1 firmware upgrade ends. Lock released.
……
……
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BR1 firmware upgrade starts
TE re-acquires lock, and moves traffic back
……
……
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BR1 firmware upgrade starts
TE re-acquires lock, and moves traffic back
……
……
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Case #1 Summary
• Each application: • Simple logic• Unaware of the other
• Statesman enables: • Conflict resolution• Necessary coordination
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Case #2: Maintain Capacity Invariant
Firmware-upgrade & Link-corruption-mitigation
32
…
ToR
Agg
…… …
Core
…Pod 4
41
1 n…Pod 1
41
1 n …Pod 10
41
1 n
1 4
Link corrupting packets
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……
……
…
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Upgrade proceeds in normal speed in Pod 3 and 5
……
……
…
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Upgrade proceeds in normal speed in Pod 3 and 5
……
……
…
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Upgrade proceeds in normal speed in Pod 3 and 5
……
……
…
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Upgrade proceeds in normal speed in Pod 3 and 5
Upgrade in Pod 4 is slowed down by checker due to lost
capacity
……
……
…
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Upgrade proceeds in normal speed in Pod 3 and 5
Upgrade in Pod 4 is slowed down by checker due to lost
capacity
……
……
…
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Case #2 Summary
• Statesman:• Automatically adjusts application
progresses• Keeps the network within safety
requirements
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Conclusion
• Need network operating system for multiple management applications
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Conclusion
• Need network operating system for multiple management applications
• Statesman• Loose coupling of applications• Network state abstraction
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Conclusion
• Need network operating system for multiple management applications
• Statesman• Loose coupling of applications• Network state abstraction
• Deployed and operational in Azure
35
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36
Thanks!
Questions?Check paper for related works