What are the right abstractions for capturing programming and - - PowerPoint PPT Presentation

What are the right abstractions for capturing programming and intent

Discussion section Thursday Feb 12, 11:25-12:15

Capturing Intent

• Aaron Gember: Infer intent. Can you simply look at configurations or

dataplane to extract intent. What intents do you need to support in a language.

• Karthick:
• undocumented legacy – reverse engineer intent.

Nontechnical challenge: cost of changing intent. To handle security has to cover both what has to be allowed and has to be

• denied. Can be hard/infeasible to enumerate. Two initial buckets: known to

be allowed, known to be denied, third bucket underspecified. Resolve by talking to operators.

• Architected systems – intent is accessible

Performance Intent

• Jennifer, Ratul:
• For resource management and ACLs, configure and optimize network for objectives
• See network as one big switch
• Brighten:
• Wide area network utility being developed
• Canini:
• Are there service level objectives for capturing performance intent.
• [Ratul] availability SLA but not much systematic
• Ratul:
• Hardest part of reasoning about availability is reasoning on time windows
• For resource allocation: have temporal resource buckets, need to think about what

network will look like tomorrow while making decisions today.

Performance Intent

• Aaron:
• Intrigued by dynamo. If we have may to capture intent there, then can we

capture them.

• Brighten:
• Intent discussion is ambitious, infeasible to fully handle. Merlin was a really

good approach to scope intent capturing in a feasible way. Would it be feasible to capture relatively complete intents for network fabrics (or some

• ther domain).
• Canini
• How can we reason about forwarding over time is a challenge not handled

with current techniques. NetQKat an approach for reasoning about quantitative properties of network.

Performance Intent

• Canini:
• Much work relies on policies. Typical policy: there is a minimal bandwidth that

each participants gets, for additional b/w required there is a policy to distribute resources across the network.

• Ratul:
• Missing link: marrying applications intent with network operators intent.
• Arjun:
• One can choose different VMs with varying performance.

Performance Intent

• Karthick:
• Security space: old paper lists 11 goals for security design (separation of duty,

least privilege, …) Most languages try to facilitate these notions in the notions they provide.

• Is there a similar catalogue of intent for SDNs?
• Canini:
• Resource allocation, security, reliability: Are there different abstractions and

programming language features to apply?

• Panda:
• Panogotios:

Languages

• Canini:
• P4 - Low level language
• View of programmability of SDN, and Click where you have potentially arbitrary
• software. Not sure if there is a way to unify this. Vision: as programmer of

application/distributed system I want to write one piece of software that encodes all the operations that application layer information needs to be looked at and

• processed. Want it decomposed and tiered. Where the partition is a function of the

environment as opposed to development time.

• Arjun:
• DSL for discussing network, such as NetKAT
• Then there is FlowLog for programming both data and control plane.
• Then there is general computation on packets and do it well.
• Dataplane verification becomes harder problem of general purpose program

verification.

Languages

• Tim:
• Don’t need Turing complete languages in general. In FlowLog created abstraction of

adequate but verifiable power.

• Andrey:
• SDN languages are there to create programs.
• How many programs are there?
• [Canini] why would you want to program a network?
• [Jennifer] examples in my talk are real, e.g., wide area network control management

is used by both Google and Microsoft. Open networking foundation for creating an anchor stack, beginning of a path towards adoption.

• [Ratul] are these systems implemented in SDN languages or just implemented?
• [Nate] It is early days.