Transcript Router

VROOM: Virtual ROuters On
the Move
Jennifer Rexford
Joint work with Yi Wang, Eric Keller,
Brian Biskeborn, and Kobus van der Merwe (AT&T)
http://www.cs.princeton.edu/~jrex/papers/vroom08.pdf
Virtual ROuters On the Move
• Key idea
– Routers should be free to roam around
• Useful for many different applications
– Simplify network maintenance
– Simplify service deployment and evolution
– Reduce power consumption
–…
• Feasible in practice
– No performance impact on data traffic
– No visible impact on routing protocols
2
The Two Notions of “Router”
• IP-layer logical functionality, and physical equipment
Logical
(IP layer)
Physical
3
Tight Coupling of Physical & Logical
• Root of many network-management challenges (and
“point solutions”)
Logical
(IP layer)
Physical
4
VROOM: Breaking the Coupling
• Re-mapping logical node to another physical node
VROOM enables this re-mapping of logical to
Logical
physical through virtual router migration.
(IP layer)
Physical
5
Case 1: Planned Maintenance
• NO reconfiguration of VRs, NO reconvergence
VR-1
A
B
6
Case 1: Planned Maintenance
• NO reconfiguration of VRs, NO reconvergence
A
VR-1
B
7
Case 1: Planned Maintenance
• NO reconfiguration of VRs, NO reconvergence
A
VR-1
B
8
Case 2: Service Deployment/Evolution
• Move (logical) router to more powerful hardware
9
Case 2: Service Deployment/Evolution
• VROOM guarantees seamless service to existing
customers during the migration
10
Case 3: Power Savings
• $ Hundreds of millions/year of electricity bills
11
Case 3: Power Savings
• Contract and expand the physical network according
to the traffic volume
12
Case 3: Power Savings
• Contract and expand the physical network according
to the traffic volume
13
Case 3: Power Savings
• Contract and expand the physical network according
to the traffic volume
14
Virtual Router Migration: Challenges
1. Migrate an entire virtual router instance
•
All control plane & data plane processes / states
15
Virtual Router Migration: Challenges
1. Migrate an entire virtual router instance
2. Minimize disruption
•
•
Data plane: millions of packets/sec on a 10Gbps link
Control plane: less strict (with routing message retrans.)
16
Virtual Router Migration: Challenges
1. Migrating an entire virtual router instance
2. Minimize disruption
3. Link migration
17
Virtual Router Migration: Challenges
1. Migrating an entire virtual router instance
2. Minimize disruption
3. Link migration
18
VROOM Architecture
Data-Plane Hypervisor
Dynamic Interface Binding
19
VROOM’s Migration Process
• Key idea: separate the migration of control
and data planes
1.Migrate the control plane
2.Clone the data plane
3.Migrate the links
20
Control-Plane Migration
• Leverage virtual server migration techniques
• Router image
– Binaries, configuration files, etc.
21
Control-Plane Migration
• Leverage virtual server migration techniques
• Router image
• Memory
– 1st stage: iterative pre-copy
– 2nd stage: stall-and-copy (when the control plane
is “frozen”)
22
Control-Plane Migration
• Leverage virtual server migration techniques
• Router image
• Memory
CP
Physical router A
DP
Physical router B
23
Data-Plane Cloning
• Clone the data plane by repopulation
– Enable migration across different data planes
– Avoid copying duplicate information
Physical router A
DP-old
CP
Physical router B
DP-new
24
Remote Control Plane
• Data-plane cloning takes time
– Installing 250k routes may take several seconds
• Control & old data planes need to be kept “online”
• Solution: redirect routing messages through tunnels
Physical router A
DP-old
CP
Physical router B
DP-new
25
Remote Control Plane
• Data-plane cloning takes time
– Installing 250k routes takes over 20 seconds
• Control & old data planes need to be kept “online”
• Solution: redirect routing messages through tunnels
Physical router A
DP-old
CP
Physical router B
DP-new
26
Remote Control Plane
• Data-plane cloning takes time
– Installing 250k routes takes over 20 seconds
• Control & old data planes need to be kept “online”
• Solution: redirect routing messages through tunnels
Physical router A
DP-old
CP
Physical router B
DP-new
27
Double Data Planes
• At the end of data-plane cloning, both data
planes are ready to forward traffic
DP-old
CP
DP-new
28
Asynchronous Link Migration
• With the double data planes, links can be
migrated independently
A
DP-old
B
CP
DP-new
29
Prototype Implementation
• Virtualized operating system
– OpenVZ, supports VM migration
• Routing protocols
– Quagga software suite
• Packet forwarding
– Linux kernel (software), NetFPGA (hardware)
• Router hypervisor
– Our extensions for repopulating data plane,
remote control plane, double data planes, …
30
Experimental Evaluation
• Experiments in Emulab
– On realistic Abilene Internet2 topology
31
Experimental Results
• Data traffic
– Linux: modest packet delay due to CPU load
– NetFPGA: no packet loss or extra delay
• Routing-protocol messages
– Core router migration (intradomain only)
• Inject an unplanned link failure at another router
• At most one retransmission of an OSPF message
– Edge router migration (intra and interdomain)
• Control-plane downtime: 3.56 seconds
• Within reasonable keep-alive timer intervals
– All routing-protocol adjacencies stay up
32
Where To Migrate
• Physical constraints
– Latency
• E.g, NYC to Washington D.C.: 2 msec
– Link capacity
• Enough remaining capacity for extra traffic
– Platform compatibility
• Routers from different vendors
– Router capability
• E.g., number of access control lists (ACLs) supported
• Constraints simplify the placement problem
– By limiting the size of the search space
33
Conclusions on VROOM
• VROOM: useful network-management primitive
– Separate tight coupling between physical and logical
– Simplify network management, enable new applications
• Evaluation of prototype
– No disruption in packet forwarding
– No noticeable disruption in routing protocols
• Future work
– Migration scheduling as an optimization problem
– Extensions to router hypervisor for other applications
34
Other Projects Related to Router
Virtualization
Bug-Tolerant Routers
• Seriousness of routing software bugs
– Cause serious outages, misbehavior, vulnerability
– Violate protocol semantics, so not handled by
traditional failure detection and recovery
• Handling bugs at run time
– Run multiple routing instances in parallel
– Use different execution environments, message
timings/orderings, or code bases
– Vote on “answers” forwarding-table entries and
messages to neighboring routers
Collaboration with Matt Caesar and Yuanyuan Zhou at UIUC
Virtual Network Infrastructure (VINI)
• Experimental platform for network research
– Evaluating prototypes of network architectures
– Supporting multiple experiments in parallel
– Carrying real user traffic & connecting to Internet
• VINI platform (www.vini-veritas.net)
– Virtual nodes, links, and network stack in Linux
– Instantiation of virtual topology for experimenters
– VINI nodes deployed in NLR and Internet2
Collaboration with Nick Feamster (GA Tech) and
Andy Bavier and Larry Peterson (Princeton)
Concurrent Architectures are Better
than One (CABO)
• Overcome limitations of today’s Internet
– Applications with diverse requirements
– Too many (sometimes conflicting) goals
– Difficulty of coordinating across domains
• New architecture based on virtualization
– Infrastructure providers: own and manage
equipment, and host virtual nodes and links
– Service providers: run virtual networks customized
to their end-to-end services
Collaboration with Nick Feamster (GA Tech) and Lixin Gao (UMass)
Dynamically Adaptive Virtual Networks
for a Customized Internet (DaVinci)
• Multiple applications with different goals
– E.g., throughput-sensitive and delay-sensitive
– Want to operate customized network protocols
• How to allocate bandwidth between classes?
– Static is inefficient, but dynamic may be risky
• Theoretical foundation based on optimization
– Customized protocol for each traffic class
– Dynamic bandwidth allocation rule for each link
– Provably maximizes aggregate performance
Collaboration with Mung Chiang (Princeton)
Conclusions
• Router virtualization is exciting
– Enables wide variety of new networking techniques
– … for network management & service deployment
– … and even rethinking the Internet architecture
• Fascinating space of open questions
– What is the right interface to router hardware?
– What is the right programming environment for
customized protocols on virtual networks?
• Looking forward to discussing more!