SDN

1. Centralized and Distributed Control
and Data Planes
SDN – Chapter 1

2. Introduction
The separation of the control and data planes is
indeed one of the fundamental tenets of SDN.

3. Figure 2-2. Control and data planes of a typical network

4. Figure 2-3. Control and data planes of a typical network device

5. Ingress feature application on a
traditional router
Figure 2-4. Generic example of ingress feature application on a traditional router/
switch.

6. Figure 2-6. Control and data plane example implementation

7. Why Can Separation Be Important?
• Scale matters
– The scalability of a routing and switching system can
take place in myriad ways, coupled with issues that
might range from raw packet forwarding performance
to power consumption.
• Evolution
• Cost
• Innovation
• Stability
• Complexity and its resulting fragility

8. Figure 2-7. Separating the integrated management, control, service, and
forwarding planes so that they can scale independently

9. Figure 2-8. The cluster and multichassis system designs

10. Figure 2-9. Process interaction in an IGP/BGP/MPLS network

11. Distributed Control Planes
•
•
IP and MPLS
Creating the IP Underlay
– Convergence Time
Convergence is the time it takes from when a network
element introduces a change in reachability of a destination
due to a network event to when this change is seen and
instantiated by all other relevant network elements
– Load Balancing
– High Availability
Redundancy at the network level
Redundancy at the element level using redundant route
processors/switch control module.

12. Consistency of routing state
Figure 2-10. Eventual consistency of routing state

13. Route recursion
Figure 2-11. Route recursion

14. Figure 2-12. An MPLS VPN (VRF label distribution via route reflection)
over an OSPF multiarea underlay

15. MPLS label
Figure 2-13. MPLS label

16. Figure 2-14. An MPLS VPN (VRF label
distribution via route reflection) over an MPLS
TE core (all over an OSPF underlay)
Figure 2-14. An MPLS VPN (VRF label distribution via route reflection)
over an MPLS TE core (all over an OSPF underlay)

17. Centralized Control Planes
• Logical Versus Literal
– Scale
– High Availability
– Geography
• ATM/LANE
• Route Servers

18. ATM/LANE
Asynchronous Transfer Mode (ATM) is a connection-
oriented cell switching and multiplexing
technology
LAN emulation (LANE) makes an ATM network
appear like an Ethernet network—providing the
same MAC-layer service interface.
To create this overlay, some ATM-connected, role-
specific servers were required.
This is illustrated in Figure 2-15. The required
servers were the LES, the LEC, and the BUS.

19. ATM/LANE
The LES (LAN Emulation Server) provided a MAC registration
and control server to LAN Emulation Clients (LEC)—
essentially, the role of ARP server for the ELAN (LE-ARP).
The LES was paired with a BUS.
The BUS (Broadcast and Unknown Server) was a multicast
server that handled BUM (Broadcast, Unicast and
Multicast) traffic for a specific ELAN.
The LECS (LAN Emulation Configuration Server) maintained a
domain-wide database of LEC/ELAN mappings was a query
point for this level of resolution (providing the ATM address
of the LES serving a specific ELAN).

20. ATM/LANE
Figure 2-15. LANE clients and servers

21. Route Servers
Figure 2-16. Route server architecture
The route server evolved as a means for Internet service
providers to handle the scale of peers and policies at
external peering points.

22. Figure 2-17. IIR and route server interconnection

23. Route reflection of prefix
Figure 2-18. Route reflection of prefix 11.11.11.11/24 from one client across
a hierarchy of reflectors to all clients