enabling innovation inside the network joint with nate foster, david walker, rob harrison, chris...
TRANSCRIPT
Enabling Innovation Inside the Network
Joint with Nate Foster, David Walker, Rob Harrison, Chris Monsanto, Cole Schlesinger, Mike Freedman, Mark Reitblatt, Joshua Reich
Jennifer RexfordPrinceton University
http://www.cs.princeton.edu/~jrex
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What is Networking?
end-hosts need to communicate
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What is Networking?
Ethernet switches connect them
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What is Networking?
which decide how packets should be forwarded
Control Plane
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What is Networking?
and actually forward them
Data Plane
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What is Networking?
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What is Networking?
servers
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What is Networking?
connected by routers
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w/ similar data planes
What is Networking?
connected by routers
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What is Networking?
connected by routers
but completely different control planes
plug-and-play
structured and optimized
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What is Networking?
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What is Networking?
we need gateway to bridge them
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What is Networking?
and load balancing for servers
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What is Networking?
there are other ISPs
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What is Networking?
requiring inter-domain routers
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What is Networking?
and a firewall to handle malicious
traffic
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What is Networking?
and mobile endpoints
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What is Networking?
requiring wireless basestations
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What is Networking?
and more middleboxes for
billing, lawful intercept, DPI
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What is Networking?
Ad absurdum
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This is a Control Plane Issueeach color represents a different set of control-
plane protocols and algorithms
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This is a Control Plane Issuewhose implementation
may vary by vendor and model
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Software Defined Networks
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decouple control and data planes
Software Defined Networks
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decouple control and data planesby providing open standard API
Software Defined Networks
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(Logically) Centralized Controller
Controller Platform
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Protocols Applications
Controller PlatformController Application
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Payoff
• Cheaper equipment• Faster innovation• Easier management
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Entire backbone
runs OpenFlow
A Major Trend in Networking
Bought for $1.2 x 109
(mostly cash)
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But How Should We Program SDNs?
Controller Platform
Controller ApplicationNetwork-wide visibility and control
Direct control via open interface
Today’s controller APIs are tied to the underlying hardware
OpenFlow Networks
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Data Plane: Packet Handling
• Simple packet-handling rules– Pattern: match packet header bits– Actions: drop, forward, modify, send to controller – Priority: disambiguate overlapping patterns– Counters: #bytes and #packets
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1. src=1.2.*.*, dest=3.4.5.* drop 2. src = *.*.*.*, dest=3.4.*.* forward(2)3. src=10.1.2.3, dest=*.*.*.* send to controller
Control Plane: Programmability
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Events from switchesTopology changes,Traffic statistics,Arriving packets
Commands to switches(Un)install rules,Query statistics,Send packets
Controller Platform
Controller Application
E.g.: Server Load Balancing• Pre-install load-balancing policy• Split traffic based on source IP
src=0*
src=1*
Seamless Mobility/Migration• See host sending traffic at new location• Modify rules to reroute the traffic
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Programming Abstractions for Software Defined Networks
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Network Control Loop
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Readstate
OpenFlowSwitches
Writepolicy
Compute Policy
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Reading State
SQL-Like Query Language
Reading State: Multiple Rules
• Traffic counters– Each rule counts bytes and packets– Controller can poll the counters
• Multiple rules– E.g., Web server traffic except for source 1.2.3.4
• Solution: predicates– E.g., (srcip != 1.2.3.4) && (srcport == 80)– Run-time system translates into switch patterns
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1. srcip = 1.2.3.4, srcport = 802. srcport = 80
Reading State: Unfolding Rules
• Limited number of rules– Switches have limited space for rules– Cannot install all possible patterns
• Must add new rules as traffic arrives– E.g., histogram of traffic by IP address– … packet arrives from source 5.6.7.8
• Solution: dynamic unfolding– Programmer specifies GroupBy(srcip)– Run-time system dynamically adds rules
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1. srcip = 1.2.3.41. srcip = 1.2.3.42. srcip = 5.6.7.8
Reading: Extra Unexpected Events
• Common programming idiom– First packet goes to the controller– Controller application installs rules
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packets
Reading: Extra Unexpected Events
• More packets arrive before rules installed?– Multiple packets reach the controller
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packets
Reading: Extra Unexpected Events
• Solution: suppress extra events– Programmer specifies “Limit(1)”– Run-time system hides the extra events
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packets
not seen byapplication
Frenetic SQL-Like Query Language
• Get what you ask for– Nothing more, nothing less
• SQL-like query language– Familiar abstraction– Returns a stream– Intuitive cost model
• Minimize controller overhead– Filter using high-level patterns– Limit the # of values returned – Aggregate by #/size of packets
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Select(bytes) *Where(in:2 & srcport:80) *GroupBy([dstmac]) *Every(60)
Select(packets) *GroupBy([srcmac]) *
SplitWhen([inport]) *Limit(1)
Learning Host Location
Traffic Monitoring
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Computing Policy
Parallel and Sequential Composition
Abstract Topology Views
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Combining Many Networking Tasks
Controller Platform
Monitor + Route + FW + LB
Monolithic application
Hard to program, test, debug, reuse, port, …
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Modular Controller Applications
Controller Platform
LBRout
eMonit
orFW
Easier to program, test, and debugGreater reusability and portability
A module for each task
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Modules Affect the Same Traffic
Controller Platform
LBRout
eMonit
orFW
How to combine modules into a complete application?
Each module partially specifies the handling of the traffic
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Parallel Composition [ICFP’11, POPL’12]
Controller Platform
Route on dest
prefix
Monitor on source
IP+
dstip = 1.2/16 fwd(1)dstip = 3.4.5/24 fwd(2)
srcip = 5.6.7.8 countsrcip = 5.6.7.9 count
srcip = 5.6.7.8, dstip = 1.2/16 fwd(1), countsrcip = 5.6.7.8, dstip = 3.4.5/24 fwd(2), countsrcip = 5.6.7.9, dstip = 1.2/16 fwd(1), countsrcip = 5.6.7.9, dstip = 3.4.5/24 fwd(2), count
• Spread client traffic over server replicas– Public IP address for the service– Split traffic based on client IP– Rewrite the server IP address
• Then, route to the replica
Example: Server Load Balancer
clients
1.2.3.4
load balancer
server replicas
10.0.0.1
10.0.0.2
10.0.0.3
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Sequential Composition [NSDI’13]
Controller Platform
RoutingLoad Balancer >>
dstip = 10.0.0.1 fwd(1)dstip = 10.0.0.2 fwd(2)
srcip = 0*, dstip=1.2.3.4 dstip=10.0.0.1srcip = 1*, dstip=1.2.3.4 dstip=10.0.0.2
srcip = 0*, dstip = 1.2.3.4 dstip = 10.0.0.1, fwd(1)srcip = 1*, dstip = 1.2.3.4 dstip = 10.0.0.2, fwd(2)
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Dividing the Traffic Over Modules
• Predicates– Specify which traffic traverses which
modules– Based on input port and packet-header
fields
Routing
Load Balancer
Monitor
Routing
dstport != 80
dstport = 80 >>
+
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High-Level Architecture
Controller Platform
M1 M2 M3Composition
Spec
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Partially Specifying Functionality
• A module should not specify everything– Leave some flexibility to other modules– Avoid tying the module to a specific
setting
• Example: load balancer plus routing– Load balancer spreads traffic over
replicas– … without regard to the network paths
Load Balancer
Routing>>
Avoid custom interfaces between the modules
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Abstract Topology Views [NSDI’13]
• Present abstract topology to the module– Implicitly encodes the constraints – Looks just like a normal network– Prevents the module from overstepping
55Real network Abstract view
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Separation of Concerns
• Hide irrelevant details– Load balancer doesn’t see the internal
topology or any routing changes
Routing view Load-balancer view
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High-Level Architecture
Controller Platform
View Definitions
M1 M2 M3Composition
Spec
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Supporting Topology Views
• Virtual ports– (V, 1): [(P1,2)]– (V, 2): [(P2, 5)]
• Simple firewall policy– in=1 out=2
• Virtual headers– Push virtual ports– Route on these ports– From (P1,2) to (P2,5)
V1 2
firewall
routing
P1 P2
1 122
3 3
4
4
5
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Writing State
Consistent Updates
Writing Policy: Avoiding Disruption
Invariants• No forwarding loops• No black holes• Access control• Traffic waypointing
Writing Policy: Path for New Flow
• Rules along a path installed out of order?– Packets reach a switch before the rules do
61Must think about all possible packet and event orderings.
packets
Writing Policy: Update Semantics
• Per-packet consistency– Every packet is processed by– … policy P1 or policy P2 – E.g., access control, no loops
or blackholes
• Per-flow consistency– Sets of related packets are processed by– … policy P1 or policy P2,– E.g., server load balancer, in-order delivery,
…
P1
P2
Writing Policy: Policy Update
• Simple abstraction– Update entire configuration at once
• Cheap verification– If P1 and P2 satisfy an invariant– Then the invariant always holds
• Run-time system handles the rest– Constructing schedule of low-level updates– Using only OpenFlow commands!
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P1
P2
Writing Policy: Two-Phase Update
• Version numbers– Stamp packet with a version number (e.g., VLAN tag)
• Unobservable updates– Add rules for P2 in the interior– … matching on version # P2
• One-touch updates– Add rules to stamp packets
with version # P2 at the edge
• Remove old rules– Wait for some time, then
remove all version # P1 rules
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Writing Policy: Optimizations
• Avoid two-phase update– Naïve version touches every switch– Doubles rule space requirements
• Limit scope – Portion of the traffic– Portion of the topology
• Simple policy changes– Strictly adds paths– Strictly removes paths 65
Frenetic Abstractions
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SQL-likequeries
OpenFlowSwitches
ConsistentUpdates
Policy Composition
Related Work
• Programming languages– FRP: Yampa, FrTime, Flask, Nettle– Streaming: StreamIt, CQL, Esterel, Brooklet, GigaScope– Network protocols: NDLog
• OpenFlow– Language: FML, SNAC, Resonance– Controllers: ONIX, POX, Floodlight, Nettle, FlowVisor– Testing: NICE, FlowChecker, OF-Rewind, OFLOPS
• OpenFlow standardization– http://www.openflow.org/– https://www.opennetworking.org/
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Conclusion
• SDN is exciting– Enables innovation– Simplifies management– Rethinks networking
• SDN is happening– Practice: useful APIs and good industry traction– Principles: start of higher-level abstractions
• Great research opportunity– Practical impact on future networks– Placing networking on a strong foundation
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Frenetic Project
http://frenetic-lang.org
• Programming languages meets networking– Cornell: Nate Foster, Gun Sirer, Arjun Guha, Robert Soule,
Shrutarshi Basu, Mark Reitblatt, Alec Story
– Princeton: Dave Walker, Jen Rexford, Josh Reich, Rob Harrison, Chris Monsanto, Cole Schlesinger, Praveen Katta, Nayden Nedev
Short overview at http://www.cs.princeton.edu/~jrex/papers/frenetic12.pdf