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Protocol Oblivious Forwarding:
Unleash the Power of SDN through
a Future-Proof Forwarding Plane
Haoyu Song
Networks Business Unit, Technology Strategy, IP Research
Huawei Technologies, USA
HUAWEI TECHNOLOGIES CO., LTD.
www.huawei.com
What Happened to Your Mobile Phone: A Metaphor
Past

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
Now
Preloaded with all the features
Get new models for new apps
No way to customize



Download only the apps you need
New features in new software release
Write your own apps
Decoupling the platform and the apps is the key for smart phone’s
success. The real value exists in services provided by software. Better
hardware can carry and deliver the value better.
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Network Device Programming Models
I can only
use the
device as- is.
Data Plane
Device Vendor-driven
Programmability
Closed and proprietary
design that meets the predefined service requirements
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Control Plane
Program
“Black Box”
Control Plane
I can do
whatever I
want.
Control
Management
Control Plane
I can do what
the device has
supported.
OpenFlow 1.x
OpenFlow+
“Gray Box”
“White Box”
Data Plane
Data Plane
Device Vendor/Service
Service Provider-driven
Provider Split Programmability Programmability
Open interface using existing
technology building blocks for
limited programmability
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Open interface using generic
network programming model,
enabling full programmability
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Current OpenFlow-enabled Device is a “Gray Box”
New service required
Yes
No
Wait for new revision of OF Spec.
Wait for the device upgrade to
support the new spec.
Deploy the software to enable the
service
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
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Plane coupling
Protocol/instruction explosion
Stateless/Limited expressivity

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Not future-proof
Slow innovation process
Protocol-specific semantics forces the forwarding elements (FE) to
understand the packet formats and retain the specific packet processing
knowledge. The reactive evolving path needs incessant standard
revisions to accommodate new features and new protocols.
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Ideal path
Does the OF
Spec. support it?
SDN: Operate your Network Device like a PC



Simple & generic
instruction set
Ultimate flexibility &
extensibility
Upgrade only on
performance
Service
Application
API
Sys. Call
Operating
System
Controller
Driver
Instruction Set
Forwarding
Element
CPU system
Peripheral
SDN
Computer System
Computer system components have been decoupled from the vertical
integration model. SDN is on the track to mimic this transition. But
current OpenFlow still doesn’t embrace this model to the full extent.
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Protocol Oblivious Forwarding: Core Concept
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Table search keys
are defined as {offset,
length} tuples
Instructions/Actions
access packet data or
metadata using
{offset, length} tuples
Include other math,
logic, move,
branching, and jump
instructions
Match
Action
~40 matching header
fields defined yet still
many uncovered
protocols/headers
{offset, length} covers
any frame based
formats
OFPAT_COPY_TTL_OUT
OFPAT_COPY_TTL_IN
OFPAT_SET_MPLS_TTL
OFPAT_DEC_MPLS_TTL
OFPAT_PUSH_VLAN
OFPAT_POP_VLAN
OFPAT_PUSH_MPLS
OFPAT_POP_MPLS
OFPAT_SET_NW_TTL
OFPAT_DEC_NW_TTL
OFPAT_PUSH_PBB
OFPAT_POP_PBB
and on and on and on …
POFAT_SET_FIELD
POFAT_ADD_FIELD
POFAT_DELETE_FIELD
POFAT_MOD_FIELD
Period.
Current OpenFlow
POF
Packet field parsing and handling are abstracted as generic instructions
to enable flexible and future proof forwarding elements. This is simple yet
has profound implications to SDN.
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How to Ask a Dumb FE to Do Smart Things

The fine-grained bit-level manipulations used to be hardcoded or
micro-coded in the FE are now explicitly described by controller
Is this an IP
packet?
Data @ {12B, 2B} = 0x0800?
Use destination IP
to search FIB
Extract Data @ {30B, 4B};
Use it as key to search LPM
table x
Process TTL
Decrement Data @ {22B,
1B};
If result is 0, drop the packet
Update Checksum
Clear Data @ {24B, 2B};
Use algorithm y to calculate
checksum over Data @
{14B, 20B}; Write result @
{24B, 2B}
Conventional FE
Forwarding Flow
POF Forwarding
Flow
DMAC
SMAC
Type
Payload
FCS
Ethernet/IPv4 Packet Format
OpenFlow’s high level semantics (“what”) is simple in communication but
demands forwarding plane intelligence; POF’s low level semantics
(“how”) moves all the intelligence up to the controller
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Other POF Features to Enhance OpenFlow

Enable active & stateful data-path
•Add
general flow-based metadata beyond counters
Statistics
• Time stamps
• Anomaly
• Flow states
•
•Add
key
metadata
Flow Entry
instruction
s
data-path instructions that can create and modify flow tables
MAC learning
• Active firewall
• Dynamic load balancing
• Controller offloading
•
Instruction
Execution
Module
Table Update
Flow
Table
Table Search
The flow metadata and data-path table manipulation instructions enrich
the forwarding plane programmability and flexibility
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Other POF Features to Enhance OpenFlow (cont’d)

Add entry-specific parameters and allow multiple flow entries
share the same instruction block
•

Treat statistics counters and flow metadata as shared resource
pool and assign the resource to flow entries on demand
•
•

Save instruction memory and enable fast updates
Aggregated and multi-purpose counters for statistics
Message communication vehicle for flows
Distinguish logical tables and physical tables
•
•
The same physical table used by multiple logical tables (e.g. IP/RPF, MAC
Learning/forwarding)
One physical table resource shared by multiple unrelated logical tables (e.g
TCAM, Hash)
These new features facilitate the efficient hardware implementation,
otherwise it would be difficult or even impossible for FE to figure out the
optimization opportunities.
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POF-based SDN Architecture
Novel Applications
&Services
Protocol Specific
Application
Programming
Languages
Flow Instruction Set
Controller
POF
Instructions
ASIC
POF Data Path
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• High
performance
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Hardware
Abstraction Layer
Flex Flow
Processor
CPU
• Runtime & Remote
reprogrammable
• Table driven &
protocol blind
• Flow instruction set
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Driver
•
•
•
•
Flexible
Generic
Standard
Low level
instruction
set
Forwarding Elements
NPU
• Programmable
• Network
optimized
Flow
Tables
Controller
Compiler
Protocol Agnostic
Tables/Instructions
OpenFlow+
Application API
POF System Prototypes
Forwarding Elements
Controller
Controller
Controller
HUAWEI Core Router
POFSwitch
MPU
Switch Control Module
OpenFlow Connection Management
POFGUI
Protocol
Oblivious
Forwarding
OpenFlow Parse
Bypass
Manager
Module
OpenFlow Encap
LPU
OpenFlow Parse
POFManager
OpenFlow Connection Management
OpenFlow Encap
Resouce Module
Resouce of POFSwitch
Floodlight Provider
(Controller)
HAL of POF
Forwarding Engine Driver
PMDatabase
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Datapath Module
Other
OFMessage
Process Modules
Forwarding
Engine
Based on Floodlight with POF
extension
Open source, cross platform,
Apache licensed, and Javabased software
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Forwarding
Engine
NP-based hardware
implementation on NE5000E or
NE40E router platform
Open source software switch on
Linux server
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Using NPU to Implement POF
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Proprietary NPU runs in RTC (Run To Completion) programming model
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Two modes for POF implementation
•
Function Mode: Each FIS instruction is implemented in FE NPU as a function written in
micro-code. Each instruction is essentially a function call.
•
•
Simple but has a performance hit
Compiling Mode: Controller or the FE driver compiles the FIS instructions into NPU microcode directly and load the code to the program memory.
•
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Better performance but more complex
Current prototype used Function Mode and we are working on Compiling Mode
•
We see up to 30% performance loss
•
•
Mainly due to table search key constructions
Still satisfy typical application scenarios for the 40G line card
It is feasible to use NPU to implement POF, in the long run we prefer to
have some POF-optimized silicon to reduce the cost and boost the
performance.
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POF Use Cases
Forwarding Protocol Enabling
User Defined
Source Routing
NDN
CCN
SCN
…
NVGRE
VXLAN
TRILL
IPX
Fibre Channel
…
L2
IPv4
IPv6
MPLS
…
Network Service Enabling
VPLS, Stateful Firewall, DPI, L4~L7 Applications
Other innovation possibilities
Network processing simplification reduce tunneling and transformation
User defined scratch space in packets
for in-band info communication (OAM)
POF offers unmatched flexibility to the forwarding plane. With it, we can
either deploy sophisticated network services or greatly simplify the
network forwarding process.
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How to realize POF
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Define low-level instruction set FIS
•
Platform-independent generic primitives
•
Expressive for a wide range of applications
•
Programming in “assembly” style
•
Allows layered abstraction and virtualization
•
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No need to be the same as the chip instruction set
Standardization is the key
www.poforwarding.org
•
Stabilize a future-proof OpenFlow specification (OpenFlow 2.0?)
•
Need industry-wide collaboration involving all the player
•
•
Many hard problems (technical and non-technical) to attack
We publish the open-source website to advocate open research and
encourage contributions and adoptions
•
POF has the potential to truly commoditize the forwarding elements while
nourishing an independent controller/application software market.
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Conclusions

POF thoroughly decouples the SDN control plane and the forwarding plane
•
Controller-side software can construct flexible applications without any underlying
constraints
•
Controller applies high level languages and compilers to program the FEs through the
standard instruction set
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POF advocates a standard, flexible and future-proof forwarding plane
•
Allow FEs to focus on performance rather than functionality
•
FE will become simpler and more flexible
POF calls for continuous research to improve
•
Standardize the interface and the FIS, leave the other details for innovation
Service providers will benefit from this technology through:
(1) using standard, simple, and future-proof FEs to save CAPEX/OPEX
(2) quickly deploying customized and innovative services in the form of
application software to generate new revenues.
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Thank you
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Copyright©2013 Huawei Technologies Co., Ltd. All Rights Reserved.
The information in this document may contain predictive statements including, without limitation, statements
regarding
the future
financial and operating
results,
product portfolio, new technology, etc.
There are a
For more
information,
please
gofuture
to www.poforwarding.org
and
number of factors that could cause actual results and developments to differ materially from those expressed or
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implied in the predictive statements. Therefore, such information is provided for reference purpose only and
constitutes neither an offer nor an acceptance. Huawei may change the information at any time without notice.

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