Data Center Interconnect (DCI) extends data centers beyond traditional boundaries using transport options like dark fiber or layer 2/3 services. DCI is necessary for VM migrations, IP renumbering, VLAN scaling, geo-cluster applications, and disaster recovery. Challenges of DCI include broadcast storms, loops, tromboning, security issues, and STP problems. Technology options for DCI include OTV, EVPN+VXLAN, and VPLS, with EVPN+VXLAN being preferred due to support for large VLAN scales, MAC learning in the control plane, and support on both virtual and physical devices. SDN/cloud technologies are changing DCI through orchestration of seamless virtual networks

1. Data Center Interconnect
By: Anuj Tyagi

2. What’s DCI ?
Extending data centers beyond traditional boundaries
Transport Options?
• Dark Fiber
• Layer 2 Services aka LAN extension
• Layer 3 Services

3. Why we need DCI ?

4. Why DCI is necessary?
• VM migrations
• IP renumbering
• VLAN Scaling
• Geo-cluster applications
• Disaster recovery

5. Challenges ?
• Broadcast storms: Unknown and broadcast frames may create excessive flood
• Loops: Easy to form loops in large networks
• Tromboning: Dual attached servers and switches generate excessive cross
traffic
• Security: Data on LAN extension must be encrypted
• STP Issues:
diameter: more than 7
Root can become bottleneck
Multiple path remain unused

6. Technology selection

7. OTV vs EVPN+VXLAN vs VPLS
• VXLAN gives us liberty to use 2^24 VLANS. VXLAN-EVPN is the data
centre technologies. In VPLS we have limited number of VLANS.
• In EVPN the mac-learning happens in control plane whereas in VPLS it
happens in data plane. Hence, In EVPN this feature reduces the
unknown unicast broadcast packets and wastage of resources.
• VXLAN is supported by virtual devices and as well as routers. VPLS Is
totally based on our backbone. No role in virtual devices.

8. OTV vs EVPN+VXLAN vs VPLS
• OTV does the L2 stretch at the core of the network as opposed to the
edge with EVPN.
• For core, more cost to deployment as there will be separate circuits
• Core is more expensive than Edge

9. OTV vs EVPN+VXLAN vs VPLS
• VPLS relies on MPLS transport; if your DCI link has to use IP
infrastructure, you have to configure MPLS over GRE tunnels before
you can configure VPLS.
• VPLS cannot do all-active forwarding

10. Design approach?

11. Design approach?

12. Design approach?

13. Design approach?

14. Design approach?

15. Consideration for best practices
• How STP avoid loops and broadcast storms?
• When we combine vMotion with stateful device
• Long distance vMotion led to trombing, only suggested in case of Disaster
avoidance
• How does provider router detect active IP address or subnet?
• Which scaling protocols, technology or products to use?

16. How SDN/Cloud era changing DCI?
Orchestration for seamless stretch virtual networks and policies
SDN products:
• Cisco ACI
• VMware NSX
• Juniper Contrail

18. Resources
• https://forums.juniper.net/t5/Data-Center-Directions/Does-E-VPN-
Spell-the-End-for-OTV/ba-p/231783
• http://www.opencontrail.org/multi-datacenter-interconnect-using-
opencontrail/
• https://www.ipspace.net/Data_Center_Interconnects
• http://www.cisco.com/c/en/us/products/collateral/switches/catalyst-
6500-series-switches/qa_c67_494606.html
• http://demo.ipspace.net/get/X1%20Redundant%20Data%20Center%
20Internet%20Connectivity.mp4
• http://demo.ipspace.net/get/A1%20L2%20DCI%20Mythbusting.mp4