Yaping Zhu Advisor: Prof. Jennifer Rexford With: Andy Bavier and Nick Feamster ( Georgia Tech )
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Transcript of Yaping Zhu Advisor: Prof. Jennifer Rexford With: Andy Bavier and Nick Feamster ( Georgia Tech )
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Yaping ZhuAdvisor: Prof. Jennifer Rexford
With: Andy Bavier and Nick Feamster (Georgia Tech)
UFO: A Resilient Layered Routing Architecture
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Scalability + High Availability ?
Scalability: Scalability of routing control planeEfficiency of routing data plane
High Availability: Quick adaptation and re-route
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Can We Have the Best of Both Worlds?
Scalability Availability
Internet Routing Yes No
Overlay Routing No Yes
UFO Routing Yes Yes
Basic Idea: 1. Layered routing architecture (borrowing idea from overlay routing)2. Underlay Support for efficient and scalable overlay routing
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Outline
• Background– Internet routing architecture– Overlay routing (Resilient Overlay Networks)– Basic idea of Layered routing architecture
• Efficient overlay forwarding
• Scalable overlay monitoring
• Enhancing the scalability of UFO
• Implementation and Evaluation
• Conclusion and deployment
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Internet Routing designed for Scalability
Autonomous System (AS)
AS
AS
AS
AS
AS
AS
AS
AS
AS
AS
AS
AS
AS
ASAS
AS
AS
ASASASAS
AS
Peering
Transit
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Internet Routing without High Availability
• Scalability– Statistics: 25K ASes, 200K prefixes, millions of routers– Hierarchical: intra-domain / inter-domain routing– Prefix aggregation
• Routing protocols oblivious to performance– Intra-domain: static link weights– Inter-domain: routing policies
• Slow outage detection and recovery – Disruptions during convergence– Performance suffers from black-holes and loops
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Scalable Internet Routing without Customization
• IP does destination-based forwarding– All traffic follows the same paths– Independent of the application requirements
• Yet, applications have different needs– Voice and gaming: low latency and loss– File sharing: high throughput
High throughput,but high latency
low latency,but low throughput
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Outline
• Background– Internet routing architecture– Overlay routing (Resilient Overlay Networks)– Basic idea of Layered routing architecture
• Efficient overlay forwarding
• Scalable overlay monitoring
• Enhancing the scalability of UFO
• Implementation and Evaluation
• Conclusion and deployment
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RON: Resilient Overlay Networks (by D. Andersen)
ScalableIP routing substrate
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RON: Resilient Overlay Networks System Components
• Overlay Control Plane– Probing, overlay path evaluation– Disseminate routing messages, update routes
• Overlay Data Plane– Tunnel setup: packet
encapsulation/decapsulation
• User Opt-in Method– DNS redirection to overlay server– Connection to overlay server: tunnels (e.g
VPN)
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Overlay Routing
• Pros:– High availability: End hosts discover network-level path
failure and cooperate to re-route.– Customization: Forwarding paths tailored to the
application
• Applications:– Content distribution (e.g. Akamai SureRoute)– Application layer multicast
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Overlay Routing: Poor Efficiency
• Problem: traffic must traverse bottleneck link both inbound and outbound– Additional latency overhead– Additional traffic consumption
Upstream ISP
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Overlay Routing: Poor Scalability
ScalableIP routing substrate
I don’t know when
failure happens
Let’s just keep
probing
Shall I re-route if one
packet lost?
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Overlay Routing: Poor Scalability
• Fundamental trade-off between probing freq and adaptation– To get Quick adaptation
-> aggressive probing at short time interval-> poor scalability:->RON only supports for a small (i.e.,< 50 nodes) set of connected hosts
• Can not differentiate packet lost due to different events– Failure -> fast re-route– Congestions -> may slower? -> oscillation?
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Outline
• Background– Internet routing architecture– Overlay routing (Resilient Overlay Networks)– Basic idea of Layered routing architecture
• Efficient overlay forwarding
• Scalable overlay monitoring
• Enhancing the scalability of UFO
• Implementation and Evaluation
• Conclusion and deployment
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Can We Have the Best of Both Worlds?
Scalability Availability Customization
Internet
Routing
Yes No No
Overlay
Routing
No Yes Yes
UFO
Routing
Yes Yes Yes
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A Resilient Layered Routing Architecture
• Combination of underlay and overlay routing
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UFO: Underlay Friendly to Overlays
Underlay Friendly to Overlays
• In-network support for overlays
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A Resilient Layered Routing Architecture
• Questions:– Which functionality belong to which layer?– What are the interfaces between both layers?
• Cross-layer design– Efficiency improvement:
• Direct control over forwarding table entries
– Scalability improvement:• Explicit notification about changing network
conditions
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Outline
• Efficient overlay forwarding– Overlay forwarding on line cards– Hosting the overlay control plane
• Scalable overlay monitoring– Registration of overlay links– Notification of network events– Lazy recovery
• Enhancing the scalability of UFO• Implementation and Evaluation • Conclusion and deployment
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Outline
• Efficient overlay forwarding– Overlay forwarding on line cards– Hosting the overlay control plane
• Scalable overlay monitoring– Registration of overlay links– Notification of network events– Lazy recovery
• Enhancing the scalability of UFO• Implementation and Evaluation • Conclusion and deployment
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Efficient Overlay Forwarding
• Problem: traffic must traverse bottleneck link both inbound and outbound
• Solution: reflection points in routers
Upstream ISP
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Overlay Forwarding on Router Line Cards
• Building block: tunnels
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Where the overlay control plane runs? On Routers
• On Routers: by Router virtualization– Pros: fast updates of forwarding tables– Pros: efficient transmission of control
messages– Pros: fate-sharing
Processors
Switching Fabric
Line Cards
Router
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Where the overlay control plane runs? On Servers
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Where the overlay control plane runs? On Servers
• On separate set of servers– Update forwarding table on router line cards– Data packets reflected in-network
• Pros:– Pros: cheap compared to router– Pros: compatibility with legacy overlay server
• Cons:– Lack of fate sharing
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Outline
• Efficient overlay forwarding– Overlay forwarding on line cards– Hosting the overlay control plane
• Scalable overlay monitoring– Registration of overlay links– Notification of different kinds of network events– Lazy recovery
• Enhancing the scalability of UFO• Implementation and Evaluation • Conclusion and deployment
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Scalable Overlay Monitoring
Assumption: Rich connectivity, multiple alternative overlay pathsOverlays could even tolerate “false positive” notification
What to notify? Different applications may want notification of different events
Notification Benefits: Accurate adaptation (compared with RON)Reduce probing overhead, and increase scalability
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Scalable Overlay Monitoring
• Notification preserve overlay link abstractions– Message format:
(overlay source, overlay destination, event)– Routers store states by explicit overlay registration
• Explicit notification about events which affect performance of overlay applications– Physical failures of routers or links– Reachability failures: route withdraw, routing session
failure– Network congestion– few “hello” packets lost
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Registration of Overlay Links
1A 2 3
4
B
C
Overlay Nodes: A, B, C
Routers: 1, 2, 3, 4
Register for uni-directional overlay links A->B and A->C
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Periodical Registration of Overlay Links
1A 2 3
4
B
C
ACK for successful registration
(A,B) (A,B) (A,B) (A,B)
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Periodical Registration of Overlay Links
1A 2 3
4
B
C
(A,B)(A,C)
(A,B)(A,C)
(A,B) (A,B)
(A,C)
(A,C)
Registration kept as soft state
Periodical re-registration
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Notification of Network Events
1A 2 3
4
B
C
(A,B)(A,C)
(A,B)(A,C)
(A,B) (A,B)
(A,C)
(A,C)
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Reactive Routing and Lazy Recovery
• Assumption: rich connectivity
• Reactive routing after notification– Re-route via alternative overlay paths– Disseminate notification message to peers
• Lazy recovery– Stick to alternative overlay paths (e.g. for mins)– Re-register for failed overlay– Reason: transient period during convergence of
recovery, causing loops and blackholes
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Outline
• Efficient overlay forwarding– Overlay forwarding on line cards– Hosting the overlay control plane
• Scalable overlay monitoring– Registration of overlay links– Notification of network events– Lazy recovery
• Enhancing the scalability of UFO• Implementation and Evaluation • Conclusion and deployment
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Unicast Registration is Inefficient
1A 2 3
4
B
C(B,A)(C,A)(D,A)(E,A)
D
E
(B,A)(C,A)(D,A)(E,A)
(B,A)(C,A)
(D,A)(E,A)
(B,A)
(C,A)
(D,A)
(E,A)
• Overlay Nodes: A, B, C, D, E and Routers: 1, 2, 3, 4• Register for overlay links B->A, C->A, D->A, E->A
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Unicast Notification is inefficient
1A 2 3
4
B
C(B,A)(C,A)(D,A)(E,A)
D
E
(B,A)(C,A)(D,A)(E,A)
(B,A)(C,A)
(D,A)(E,A)
(B,A)
(C,A)
(D,A)
(E,A)
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Multicast Registration
1A 2 3
4
B
C
D
E
GroupA GroupA GroupA
GroupA
GroupA
GroupA
GroupA
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Multicast Notification
1A 2 3
4
B
C
D
E
GroupA GroupA GroupA
GroupA
GroupA
GroupA
GroupA
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Benefits of Multicast registration/notification
• Reduce registration states stored at routers– Unicast: store state for each (src, dst) pair,
O(n2)– Multicast: store state each mcast group, O(n)
• Reduce notification message overhead
• Deployment Benefits:– Exploit IP-Multicast (which routers already
have)
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Outline
• Efficient overlay forwarding– Overlay forwarding on line cards– Hosting the overlay control plane
• Scalable overlay monitoring– Registration of overlay links– Notification of network events– Lazy recovery
• Enhancing the scalability of UFO• Implementation and Evaluation • Conclusion and deployment
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Prototype Implementation on VINI
• What’s finished?– RON
• Control plane: probing and reactive routing• Data plane: overlay tunnel setup• User Opt-in: user data packets delivered by overlays
– UFO: Notification of link failure
• What to do next?– UFO
• Evaluate inter-domain routing convergence• Notification of link congestion
– Run applications: e.g. VoIP
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Prototype Implementation on VINI
• Overlay: RON• Overlay FIB• Client opt-in• Notification by Filter
XORPIP Router
UML
eth1 eth3eth2eth0
Click
PacketForwardEngine
Control
DataUmlSwitch
element
Tunnel table
Filters
PlanetLab VM
RON
OverlayFIB
VPN ServerClients
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Evaluation Setup
• Topology– Routers and Overlay nodes
s
d
r
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Evaluation1: Reactive Routing of RON
• How much time does RON spend to detect outage? – RON probe interval : 12s– RON probe timeout: 3s– Average detection time =
Probe interval / 2 + probe timeout * 3
• What to evaluate?– Fundamental trade-off between probe
frequency and detection time– Parameters: probe interval
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Evaluation1: Reactive Routing of RON
• Detection time = probe interval / 2 + probe timeout *3
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Evaluation2: comparison of Convergence Speed
• Controlled Experiment– Fail a link by filtering all the packets
• Comparison of Convergence Speed– IP routing (XORP)– RON reactive routing– Reactive routing with UFO notification
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Evaluation2: comparison of Convergence Speed
– IP Routing (XORP)• Hello-interval: 15s• Router-dead-interval: 45s
Link down Link up
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Evaluation2: comparison of Convergence Speed
– RON• Probe interval: 12s• Probe timeout: 3s• Re-route immediately after outage detection
Link down Link upRON up
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Evaluation2: comparison of Convergence Speed
– UFO routing with explicit notification• Re-route immediately after outage notification
Link down Link upRON upUFO up
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Outline
• Efficient overlay forwarding– Overlay forwarding on line cards– Hosting the overlay control plane
• Scalable overlay monitoring– Registration of overlay links– Notification of network events– Lazy recovery
• Enhancing the scalability of UFO• Implementation and Evaluation • Conclusion and deployment
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Deployability Benefits
• Forwarding Support:– Low barriers to entry– Routers already have hardware for setting
tunnels– Upgrade small fraction for overlay forwarding
• Notification Support:– Upgrade all routers to support notification
(could start with one AS)– Performance benefits and business incentives– Better real-time applications: VoIP
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Related Work
• Overlay routing– Detour (Collins98)– Resilient Overlay Networks (Andersen01)
• Improving forwarding efficiency– Path reflection and path painting (Jannotti02)
• Reducing probing overhead– Routing Underlay for Overlays (Nakao03)
• Network virtualization– VINI, GENI, CABO, VERA
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Conclusion
• Contributions– Scalable overlay routing is feasible with in-
network support– UFO provides strong reliability and a
compelling deployment model
• Future Work– Further performance evaluation– Applications: VoIP– Application Layer Multicast (with NEC Lab)
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Acknowledgement
• General Exam Committee:– Prof. Jennifer Rexford (Advisor)– Prof. Larry Peterson– Prof. Vivek Pai
• Collaborators:– Andy Bavier and Nick Feamster (Georgia Tech)
• Cabernet Research Group
• VINI Support, Planetlab Operations
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Questions?
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FAQ: recovery notification ?
• UFO does NOT support notification of recovery, because:– Alternative overlay paths available (overlays
don’t care !)– Hard for routers to determine intra-domain
convergence: synchronization to determine data-plane convergence
– Hard for routers to determine inter-domain convergence