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NVO3 Requirements for Tunneling . Igor Gashinsky and Bruce Davie IETF. Why tunnels?. M anage overlapping addresses between multiple tenants Decouple virtual topology provided by tunnels from physical network topology

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nvo3 requirements for tunneling

NVO3 Requirements for Tunneling

Igor Gashinsky and Bruce Davie

IETF

why tunnels
Why tunnels?
  • Manage overlapping addresses between multiple tenants
  • Decouple virtual topology provided by tunnels from physical network topology
  • Decouple virtual network service from physical network (e.g. provide an L2 service over an L3 fabric)
  • Support VM mobility independent of the physical network
  • Support larger numbers of virtual networks (vs. VLANs for example)
  • Reduce state requirements for physical network (e.g. MAC addresses)
  • Because all CS problems can be solved with another level of indirection
disclaimers
Disclaimers
  • We have a horse in this race, but we’ve tried hard to be objective
  • AFAICT, no existing protocol meets all the requirements in this presentation
  • We’ve put a lot of emphasis on compatibility with existing HW – others may differ on the importance of that
requirements overview
Requirements Overview
  • Control Plane independence
  • Backwards compatibility
    • Lots of installed devices & services to consider
  • Context identification
control plane independence
Control Plane Independence
  • Data planes tend to get baked into HW, control planes evolve
    • Best not to specify control plane as part of tunnel encaps
backwards compatibility 1
Backwards Compatibility (1)
  • With switches and routers
    • IP-based encaps likely to be most compatible
    • ECMP – mostly looks at IP src/dst and TCP or UDP ports, so make use of that
  • With NICs
    • Most tunneling methods break TSO, causing major performance hit for host-terminated tunnels
    • For current generation NICs, only way to keep TSO is to completely match TCP header – see draft-davie-stt-01
backwards compatibility 2
Backwards Compatibility (2)
  • Middle Boxes
    • Should be possible to transit them
    • They may need to inspect payload (e.g. for stateful firewall)
    • Stream or Frame Reassembly may be needed for L4/L7 services
  • Hardware or software-based “NV Edge”
    • “Edge” may be in hypervisor, physical switch, appliance etc.
  • With WAN services (e.g. Public IP, L3VPNs, VPLS)
    • These services carry IP or Ethernet, so compatible with IP-based encaps
context identification
Context Identification
  • As packets exit from tunnels, need to deliver them to the right “context”
    • A context may be simply a “tenant”, or a “virtual network instance” but these are special cases
    • Can also use it for other metadata (state versioning, distributed lookup, etc.)
    • Note that L3VPNs don’t have any single field that is the VPN-ID, and that’s a good thing
      • Allows much more complex notions of VPN membership than “a member of exactly one VPN”
    • An opaque context ID with control-plane defined semantics also supports control-plane independence goal