Verifiable Network Function Outsourcing Seyed K. FayazbakhshMichael K. ReiterVyas Sekar 1

Case for Network Function Outsourcing (NFO) Internet Cloud Provider + Economies of scale, pay-per use + Simplifies configuration & deployment 2 Today: High CapEx, OpEx, Delay in innovation

Concerns with ceding control Internet Cloud Provider e.g., Is this equivalent to in-house? e.g., Am I really getting cost reduction? 3

Our Vision: Verifiable NFO 4 Our focus is meeting customer expectations Key correctness properties: – Behavior – Performance – Accounting Other issues outside our scope: isolation, privacy, bandwidth costs..

What makes this challenging? Lack of visibility into the workload Dynamic, traffic-dependent, and potentially proprietary actions of the middleboxes Stochastic effects introduced by the network 5

Outline Motivation for verifiable NFO Formalizing properties A roadmap for vNFO Ongoing work and discussion 6

Formal Framework Management Interface f1f1 fnfn …. σ1σ1 σnσn B CPU, B Mem, B Net Customer CPU, Mem Net CPU, Mem π 1 in, π 2 in, … π 1 out, π 2 out,... State SpacePacket Space Reference implementation 7

Behavioral equivalence? 8 Are packets being modified or incorrectly processed? Cloud IPS Customer

Blackbox Behavioral Correctness …. σ1σ1 σnσn π 1 in π 1 out visible to customer …. σ1σ1 σnσn π 1 in Is there some viable state? π 1 out ? ? 9

Snapshot Behavioral Correctness …. σ1σ1 σnσn π 1 in π 1 out visible to customer …. σ1σ1 σnσn π 1 in Would I get the same output? π 1 out ? 10

Performance impact? 11 Is the cloud processing introducing delays? 11 Cloud IPS t1t1 t2t2 t3t3 Customer

Performance Correctness …. σ1σ1 σnσn π 1 in, π 2 in, … π 1 out, π 2 out,... …. σ1σ1 σnσn π 1 in, π 2 in, … π 1 out, π 2 out,... Would it really take this long? t 1 out, t 2 out,... observed provider performance reference performance 12

Accounting correctness? Is the provider overcharging me? 13 Cloud IPS Customer 13

Did-It Accounting Correctness …. σ1σ1 σnσn π 1 in, π 2 in, … π 1 out, π 2 out,... Did It actually consume? Charged value of resource r Consumption of resource r by provider 14

Should-It Accounting Correctness …. σ1σ1 σnσn π 1 in, π 2 in, … π 1 out, π 2 out,... Should It really cost this much? 15 Consumption of resource r by provider Consumption of resource r by reference implementation

Summarizing Correctness Properties Behavioral correctness – Blackbox: Function states are not visible to customer. – Snapshot: Function states are visible to customer Performance correctness – Is performance metric within Δ (SLA) of reference? Accounting correctness – Did-It: Were resources actually consumed? – Should-It: Was the consumption necessary? 16

Outline Motivation for NFO + vNFO Formalizing vNFO properties A roadmap for vNFO Ongoing work and discussion 17

Verifiable NFO (vNFO) Overview Management Interface B CPU, B Mem, B Net Customer CPU, Mem Net CPU, Mem π 1 in, π 2 in, … π 1 out, π 2 out,... …. Each function is implemented as a virtual appliance. NFO provider deploys a trusted shim for logging. 18

Idealized view Management Interface B CPU, B Mem, B Net Customer CPU, Mem Net CPU, Mem π 1 in, π 2 in, … π 1 out, π 2 out,... …. Shim logs every packet, instantaneous VM state, and resource usage, timestamps per packet 19

Challenges with Idealized view Management Interface B CPU, B Mem, B Net Customer CPU, Mem Net CPU, Mem π 1 in, π 2 in, … π 1 out, π 2 out,... …. 1. Middlebox actions make it difficult to correlate logs 2. Scalability and performance impact due to logging 20

Potential solutions to challenges 1.Lack of visibility into middlebox actions: – Packets may be modified by middleboxes. 1.Scalability – Infeasible to log all packets and processing stats. 21 FlowTags Trajectory Sampling

Ongoing work Leveraging nested virtualization – NFO provider does not need any platform change Adding hooks to KVM – Trustworthy accounting (CPU, memory) – Trajectory sampling + FlowTags – Instantaneous snapshotting Benchmark memory/time overheads associate with: – Packet sampling – Resource consumption calculations – Snapshotting 22

Discussion Does the customer trust the NFO provider? Is the NFO provider willing to deploy the shim layer? – Market forces: Premium service, competitive edge, etc. What are the market factors for customers? – Can customer easily switch to a different NFO provider? What is the role of SLA? – Can the billed amount always be formulated in terms of resource consumption? … 23