This document discusses software-defined networking (SDN) as it relates to cloud networking. It provides an overview of SDN and how it addresses some of the challenges with traditional network architectures. Specifically: - Traditional networks separate the control plane and data plane, which limits flexibility. SDN abstracts the network through centralization of the control plane. - SDN is useful for cloud service providers to provide multi-tenancy, security isolation, scalable routing/switching, and programmability through APIs. Edge-to-edge overlays are a good model for cloud networking by decoupling virtual networks from the physical underlay. - While overlays address some issues, a scalable SDN

1. Networking in
the cloud: An
SDN primer
Ben Cherian
Chief Strategy Officer
@bencherian
Midokura

2. The current state of
networking is too manual

3. Telecom
has this
problem
before

4. Almon Strowger –
mortician, inventor,
and possibly
paranoid

5. Strowger’s switches

6. Wanted to solve:
Privacy
Intended human errors
Solved these too:
Unintended human errors
Speed of connections
Lowering operational costs
of running a local exchange

7. What is SDN?

8. Traditional networks

9. Control Plane:
Responsible for making
decision on where the
traffic is sent

10. Data Plane:
Responsible for
forwarding traffic to the
selected destination

11. The network needs better
abstraction

12. A basic example of SDN
Contoller
Control Control Control
Data Data

13. Categories of SDN
Definition Example
Cloud Service
Providers
(CSP／CAP)
• Distributed control plane • Midokura
IaaS • VMWare/Nicira
• Software solution for IaaS Cloud
Cloud use • Nuage
Enterprises
SDN
• Centralized control plane • Juniper Qfabric
Fabric • Hardware solution for DC use • NEC Programmable Flow
• Big Switch
• Hybrid control plane (CP) • Google
Carrier/ • Distributed CP with BGP
WAN • Centralized CP using
OpenFlow
13

14. Iaas Cloud Networking Requirements
• Multi-tenancy • ACLs
• L2 isolation • Stateful (L4) Firewall
 Security Groups
• L3 routing isolation
 VPC • VPN
 Like VRF (virtual  IPSec
routing and forwarding) • BGP gateway
• Scalable control • REST API
plane • Integration with CMS
 ARP, DHCP, ICMP  OpenStack
• NAT (Floating IP)  CloudStack, etc.

15. Iaas Cloud Networking Requirements
Typical Network Topology
uplink
- Creat e one provider rout er upon deployment - Link to uplink
- Creat e a rout er f or a t enant - BGP multi-homing
- M ap a bridge f or a quant um net work - Global NAT/route settings,
e.g. for floating ip
Provider Virtual
Router (L3)
- Tenant router for
FW, LB, DHCP and NAT
Tenant/Project A Tenant/Project B
Tenant B
Tenant A
Virtual Router
Virtual Router
Network A1 Network A2 Network B1
TenantB office
Virtual L2 Virtual L2 Virtual L2
Switch A1 Switch A2 Switch B1 Tenant B
VPN Router
VM1 VM3 VM5 VM2 VM4 VM6
Office
Network

16. Candidate models
• Traditional network
• Centrally controlled OpenFlow based hop-
by-hop switching fabric
• Edge to edge overlays

17. Traditional Network
• Ethernet VLANs for L2 isolation
 4096 limit
 VLANs will have large spanning trees terminating on many hosts
 High churn in switch control planes doing MAC learning non-stop
 Need MLAG for L2 multi-path
 Vendor specific
• VRFs for L3 isolation
 Not scalable to cloud scale
 Expensive hardware
 Not fault tolerant

18. OpenFlow Fabric
• State in switches
 Proportional to virtual network state
 Need to update all switches in path when provisioning
 Not scalable, not fast enough to update, no atomicity of
updates
• Not good for IaaS cloud virtual networking

19. Edge to Edge IP Overlays
• Isolation not using VLANs
 IP encapsulation
• Decouple from physical network
• Provisioning VM doesn’t change underlay state
• Underlay delivers to destination host IP
 Forwarding equivalence class (FEC)
• Use scalable IGP (iBGP, OSPF) to build multi-path
underlay
• Inspired by VL2 from MSR

20. Market trends supporting overlay solutions
• Packet processing on x86 CPUs (at edge)
– Intel DPDK facilitates packet processing
– Number of cores in servers increasing fast
• Clos Networks (for underlay)
– Spine and Leaf architecture with IP
– Economical and high E-W bandwidth
• Merchant silicon (cheap IP switches)
– Broadcom, Intel (Fulcrum Micro), Marvell
– ODMs (Quanta, Accton) starting to sell directly
– Switches are becoming just like Linux servers
• Optical intra-DC Networks

21. Example of an overlay solution
Logical Topology
vPort Virtual
Tenant A
Switch A1
Virtual vPort
Router
vPort Provider Virtual
Virtual Switch A2
vPort
Router
Tenant B
vPort Virtual Virtual
Router Switch B1
vPort
VM
MN MN VM
BGP BGP
Multi To ISP1
Homing
Internet Private IP VM
MN Network MN VM
BGP
To ISP2 Tunnel
BGP
To ISP3
VM
MN MN VM
MN MN MN
Network State Database
Physical Topology
21

22. Overlays are the right approach!
But not sufficient.
We still need a scalable control plane.

23. Questions?