SDN Overlays
Possibilities and Implications
Sharon Barkai
Co-founder ConteXtream
Santa Clara, CA USA April-May 2014
Agenda
▪ Coupling
network services with bridging-routing,
subnets-interfaces
• Complexity, fragmentation, and scale pressures created
▪
SDN decoupling and inline orchestration of network
services
• Limitations of SDN without structure • Mitigation by SDN overlay structure
Coupling Functions and Routing
3
Re-Aggregation, Rails of Permutations
Lots of Special hardware
Fragmentation, Design for Peak
SDN-OpenFlow.. A Start
Innovative dynamic Control without compromising performance-density
Subscriber Application Network Aware
Services Decoupled from
Subnets & Hardware Interfaces
Challenge 1:
Non-Polynomial (NP) Hops
5 Add a Switch or Function? DST F(x) SRC A B C D Controller • Src > B > Switch <> F(x) > A > Dst = Best!• But A might fail, best pre-prepare alt. • But then so might B, or D
Challenge 2:
Non Shared Fate (CAP) Distribution
? ? ? ? ? ? DST F(x) SRC Reachable Y/N >> << Reachable Y/N Y/N >> <<Reachable Y/N <<Reachable Y/N Y/N >> Controller <<Y/N <<Y/N <<Y/N <<Y/N
[
Overlay!!!
]
P(topo inconsistent) >> 1Consistency, Availability, Partition (CAP) challenges Amplified by Loss of Autonomicity
Solution:
Overlays Complete Virtualization
7 Separate
Control-Forwarding Functions-Junctions Separate
Separate
Identities-Locations
Network
Virtualization
Overlays
Adding SDN Overlays
8
IP or Ethernet Underlay
Overlays Separate ID-Location and Scale By Underlay + Mapping
EndPoint (IP or Ethernet Addresses) EndPoint EndPoint Landmark or Function (RTR, BGP ,Firewall…)
• Autonomous Bridging & Routing is resorted in the underlay location network • Underlay striped from apploication complexity orders of magnitude less
addresses
Local decision synced to local forwarding using global mapping awareness
With Freedom of movement Mapping by Hashing keys to IP/ Ethernet addresses
Adding NVO Standards to SDN
9
Location Identity Separation Protocol (RFC6830)
Additions in draft-lisp-sdn-nfv for LISP-NVO
•Support SDN: XTR mapping-caching based on Flows (5-Tuple), Mapping supports Pub-Sub using
SMR
•Support NFV: Mapping is subscriber-affinity aware, flowHandlers protocol specific XTR,
MANO-Mapping
IP or Ethernet
Service Chains
Use Case 1:
Collapsed Packet Core
▪ Mobile access traffic is aggregated using an IP network into data-centers for network function processing
▪ Processing can occur in multiple racks and also in multiple distribution-centers to balance loads
▪ Network functions are applied per subscriber-flow based on user profile, application and network conditions. Example functions:
• TCP window RAN optimization, Video transcoding, Filters and firewalls, Header enrichment, Analytics, Web proxy …
▪ The SDN-NVO Fabric needs to map subscriber-flows to applications through functions by doing the following:
• Classify-map each flow at each re-entrant forwarding point • Apply and maintain inner NVE flows per mapping lookup • Maintain state affinity where flows stick to NFV instances
Use Case 1:
Collapsed Packet Core
11
(Gi, EPC,WAG,IMS,SBC..)
RAN Internet
Overlay & Mapping
TCP opt Transcode H-Enrich Router PDN
!
!
!
Gateway AAA Subscriber Registration and Map-InstantiateUse Case 2:
Managed Network Service
▪ Classic managed network services: departmental, Multi-application, Multi-tenants connected across Multiple sites and branches
▪ While Multi-Netting was always supported by IP much more
separated Virtual Private Networking was initially delivered by ATM-FRAME, and today delivered mostly using MPLS. Example:
• Virtual Routing Forwarding (VRF) in Provider Overlay Edges • Label Switching Paths (LSP) configured across the underlay
▪ Current methodology is relatively static, changes to VRFs can
destabilize route convergence and LSPs plant states on each hop ▪ This methodology is replaced by dynamic FlowMapping overlay
edges, emulated if needed (MPLS LSP tags to untouched PEs)
• Downstream tags are classified as flows, mapped and encaped • Decapsulated and re-tagged at the other end of the network
13
(MPLS-E, IP Transit, Backhaul)
Overlay & Mapping
PE Location CE PE RSVP or LDP SDN-Edge 121.1 MPLS Port1 IP port MPLS Port2 IP port MPLS port3 IP port SDN-Edge 141.2 IP port MPLS Port1 IP port MPLS Port2 IP port MPLS Port3 <<Tag17 Map&Encap 141.2.3.17>> <<Tag7
Dynamic MPLS Emulation Mapping 121.1:2:7 141.2.3:17 141.2.3:17 121.1:2:7
Use Case 2:
Use Case 3:
Distributed Packet Core Backhaul
Overlay & Mapping
eNB Locations IP Locations
Segment Routing Landmark 1: Butterfly flows Segment Routing Landmark 2: Elephant flows Collapsed Packet Core Signaling
SDN for NFVs
15
Small NFVs Big NFVs
Enterprise class discrete VMs Carrier class multi-VM systems Like Gi filters, Transcoders … Collapsed packet core EPC/IMS Integrated inline orchestration Forwarding Control
Chaining each of the functions per each subscriber flow, Local and global load balancing of the micro instances, affinity protection from topology changes due to network conditions or VM mobility
Emulate / abstract a switch for control software by tapping OpenFlow or the 3gpp control
Global load balancing of cores, flat core sites for the state-sharing middleware
How SDN Overlays support NFVs
Summary
▪ Examined limitation of tying network services to Layer 2/3
topology, and SDN to alleviate these
▪ Saw that unstructured SDN can have even greater
scale-consistency issues, can be solved by the standard
structure of overlays:
• SDN OpenFlow should not cross routing locations • SDN flows cross locations by "Map & Encap"
• Distribution is based purely by underlay & mapping
▪ Examined 3 use cases: collapsed mobile packet core
data-center, managed network services, and mobile
(human-machine) backhaul
17 IP Mapping Database North Bound NVE NVE NVE NVE Functions Users < - - FlowMapping - - >
