Evolving Toward a Self-Managing Network

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Evolving Toward a Self-Managing Network

• Jennifer Rexford
• Princeton University
• http//www.cs.princeton.edu/jrex

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Why is Network Management So Darn Hard?

• Oodles and oodles of complex features
• Many protocols
• Many mechanisms
• Many configurable parameters
• Little guidance for network administrators
• How to select and compose features?
• How to set the configurable parameters?
• Managing boxes, rather than networks
• Routers, switches, firewalls, IDSes, servers,
  etc.
• Low-level, box-specific configuration languages

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The Enemy is Complexity

• Goal raising the level of abstraction
• Network-level design and configuration
• Composition of protocols and mechanisms
• Idea 1 add abstraction on top
• Compile high-level spec into box configuration
• But, must grapple with inherent complexity
• Idea 2 design system for manageability
• Identify network-level abstractions
• and change the boxes and protocols
• But, must grapple with backwards compatibility

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Example Border Gateway Protocol

• ASes exchange reachability information
• IP prefix block of destination IP addresses
• AS path sequence of ASes along the path
• Configurable routing policies
• Path selection (which route to use?)
• Path export (who to tell about the route?)

12.34.158.0/24 path (7018,1,88)
12.34.158.0/24 path (88)
88
1
7018
data traffic
data traffic
12.34.158.5
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Some Things I Hate About BGP

• Routers in an AS have different views
• Effect protocol oscillation and loops
• Point fix testing sufficient conditions
• Routing policy distributed across routers
• Effect routers need to share information
• Point fix complex tagging of BGP routes
• Policy has only an indirect effect on traffic
• Effect selecting the right policy is hard
• Point fix what if tools for traffic
  engineering
• BGP route selection depends on the IGP
• Effect disruptions from small internal changes
• Point fix what if tools to identify risks

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Interdomain Routing Design for Manageability

• Routing Control Platform
• Represents the AS to others
• Has complete view of candidate routes
• Computes answers for the ASs routers
• Communicates with other ASes
• Using BGP or (ideally) a brand new protocol

Inter-AS Protocol
RCP
RCP
RCP
AS 1
AS 2
AS 3
Physical peering
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Advantages of RCP Approach

• Lower management complexity
• Complete, network-wide view
• Direct control over the routers
• Single specification of policies and objectives
• Simpler routers
• Much less control-plane software
• Much less configuration state
• Enabling innovation
• New algorithms for selecting paths within an AS
• New approaches to inter-AS routing

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Deployability Backwards Compatibility using BGP

• Border Gateway Protocol (BGP)
• Protocol messages sent between routers
• Decision logic route-selection process
• Policy configurable rules for path
  selection/export
• The key point is that BGP has
• Complex decision logic and policies
• Yet a simple protocol (and message format)
• Use BGP messages to program the routers

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Phase 1 Flexible Path Selection in One AS
Before conventional use of BGP in backbone
network
eBGP
iBGP
After RCP learns routes and sends answers to
routers
eBGP
RCP
iBGP
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Phase 2 AS-Wide Path Selection and Export
Before RCP gets best iBGP routes (and IGP feed)
eBGP
RCP
iBGP
After RCP gets all eBGP routes from neighbors
eBGP
RCP
iBGP
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Phase 3 Direct Communication Between RCPs
Before RCP gets all eBGP routes from neighbors
eBGP
RCP
iBGP
After ASes exchange routes via RCP
Inter-AS Protocol
RCP
RCP
RCP
iBGP
AS 1
AS 2
AS 3
Physical peering
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Systems Considerations (NSDI05)

• Reliability
• Problem single point of failure
• Solution replication of RCP components
• Consistency
• Problem inconsistent decisions by replicas
• Solution consistency without inter-replica
  protocol
• Scalability
• Problem storing and computing for all routers
• Solution store each route once and amortize work

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Example Network Management Applications

• Customer-driven route selection
• Customized load-balancing policies
• Geographic rules for route selection
• Blocking denial-of-service attacks
• Blackhole routes that drop traffic
• Only for routers carrying attack traffic
• Hitless maintenance
• Move traffic away from certain routers
• Before the operators bring down the routers

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Conclusion

• Network management is too hard
• IP was not designed for management
• Complex, distributed operation of routers
• Must reduce complexity
• Network-wide views and objectives
• Direct control over the data plane
• RCP approach is feasible
• Deployable, scalable, and reliable
• Solves important management problems
• Many interesting open problems

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Backup Slides
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Routing Control Platform (RCP)
Routing Control Platform (RCP)
Route Control Server (RCS)
Answers
Options
Topology
OSPF Viewer
BGP Engine

BGP updates
OSPF link-state advertisements
BGP updates


Network
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Scalability Standard Computing Platform

• Prototype on a high-end PC
• 3.2 GHz Pentium-4 with 8 GB of RAM
• Running the Linux 2.6.5 kernel
• Workload from the ATT backbone
• Replay the BGP and OSPF messages
• Good RCP performance
• Memory usage less than 2GB
• Speed, BGP changes less than 40 msec
• Speed, topology changes 0.1-0.8 seconds

Short answer the system can keep up
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Reliability Replication and Consistency

• Replication avoid single point of failure
• Multiple RCPs in a network
• Connected at different places
• Consistency no explicit coordination
• Replica has full view of each partition
• Replicas perform the same algorithm on the same
  data, and get the same answer

A, B
A
B
RCP A
RCP B