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FlowTags : Enforcing Network-Wide Policies in the Presence of Dynamic Middlebox Actions

FlowTags : Enforcing Network-Wide Policies in the Presence of Dynamic Middlebox Actions. Seyed K. Fayazbakhsh Vyas Sekar . Minlan Yu . Jeff Mogul. Middleboxes complicate policy enforcement in SDN. Logical view: Specify policy goals. Admin. Physical View. Network OS.

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FlowTags : Enforcing Network-Wide Policies in the Presence of Dynamic Middlebox Actions

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  1. FlowTags:Enforcing Network-Wide Policies in the Presence of Dynamic Middlebox Actions Seyed K. Fayazbakhsh Vyas Sekar Minlan Yu Jeff Mogul

  2. Middleboxes complicate policy enforcement in SDN Logical view: Specify policy goals Admin Physical View Network OS Control Apps Dynamic traffic-dependent modifications! e.g., NATs, proxies Data Plane Policy routing Access control Diagnostics Forensics

  3. Example: Policy Routing H1: NAT  Firewall H2: NAT  IDS NAT IDS Firewall H1 Internet S1 S2 H2 How do we setup correct forwarding rules?

  4. Example: Dynamic Dependence Web ACL: Block H2  xyz Proxy Get xyz.com H1 Cached response Response Internet Get xyz.com S1 S2 Cached response H2 Cached responses may violate policy

  5. Strawman Solutions Key missing piece: Lack of “visibility” into middlebox context • Careful placement? (i.e., manual) • May not always be feasible • Consolidating middleboxes? (e.g., CoMb) • Just “punting” the problem • Inferring flow mappings? (e.g., SIMPLE) • Hard to reason about accuracy + high overhead

  6. FlowTags: High-level Idea • Middleboxes “help” with the lack of visibility • Add FlowTagsto packets to bridge gaps • NAT gives IP mappings; Proxy gives cache hit/miss • Middleboxes “produce” + “consume” FlowTags • Switches only “consume” FlowTags

  7. FlowTags Architecture Overview Control Apps Controller Existing Interfaces e.g., OpenFlow FlowTags API FlowTags Config FlowTags Enhanced Middleboxes SDN enabled Switches FlowTable “decouple” e.g., NAT exposes mappings Proxy gives hit/miss state IDS uses tags to disambiguate

  8. FlowTags Southbound API FlowTags Controller FlowMatch, Action RqstTag(Pkt,Context) FlowMatch, {Tags} RqstAction(Pkt+ Tags) TagsActionTable H1 TagsFlowTable Proxy ACL S2 S1 Pkt Pktw/ Tags Internet H2 8

  9. Policy Implementation via FlowTags Policy: Block H2  xyz TagsFlowTable TagsActionTable H1, MISS  1 H1, HIT  2 H2, MISS  3 H2, HIT  4 H1 Proxy ACL S2 S1 Internet H2

  10. FlowTags Proof-of-Concept • Using Squid (> over 100,000 lines of code) • About 30 lines of code to add FlowTagssupport • Manually identify code chokepoints • Validated use-cases with examples

  11. Conclusions • Middleboxesmake policy enforcement hard • Dynamic modifications are hard to account for • FlowTags can make “flow context” visible • Minimal modifications to middleboxes • No changes to switch/switch APIs • Enabler for new verificationand forensic tasks • Simpler HSA; Dynamic policies; Correlating logs • Early promise, but many challenges remain • E.g., How many bits? Automatic patches? Control apps?

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