In this DemoFriday, Cisco’s Jose Liste and Derek Tay demonstrate how to achieve full wide area network (WAN) and metropolitan area network (MAN) orchestration through software-defined networking (SDN) and Segment Routing. During the live presentation, Cisco gave a brief introduction to Segment Routing along with an overview of its application engineered capabilities, followed by a live demo. After the presentation, Jose and Derek took questions from the audience. Read the full Q&A below!
Is the demo based on shipping software?
Cisco: Yes. The network used in this demo is built with ASR 9000 and XRv router instances running IOS XR 5.3.2. The WAN controller is running WAE 6.2 release.
What other type of policies have you implemented or plan to implement?
Cisco: We plan to implement:
- Low Latency
- Resource Avoidance
- Capacity Optimization
- Multi-Domain networks
- Multi-Layer networks
- And others
Is it possible to “manually” configure the tunnel from the app and simply delegate the path computation to the controller?
Cisco: Yes. This is another mode of operation that we support. Called REQUEST/REPLY model, where the controller does not need to dynamically create the tunnel, but simply request computation to the controller.
Can this solution work in a multi-vendor solution?
Cisco: Yes. This solution has been designed from ground up to be a multi-vendor solution. The building blocks communicate with each other using standard protocol and/or interfaces such as BGP-LS and PCEP.
I noticed that it took some time for the controller to re-optimize paths after the failures. Will this impact how the traffic traverses these paths?
Cisco: There is no extra impact to the traffic. The solution includes network intelligence to protect against failures in less than 50ms. With a Segment Routing network, we protect against link and node failures using TI-LFA.
How does Segment Routing architecture & protocols integrate in VXLAN and VTEP environments?
Cisco: Segment Routing will provide end-t0-end LSP from ToR to DCI to WAN-PE to access router seamlessly, VXLAN, L3VPN or L2VPN, or IP will run on top.
Is it possible to demonstrate the Segment Routing capabilities using the VIRL without the WAE?
Cisco: Yes, for a single domain or intra-domain use cases.
With large networks, is there a limitation for the number of hops within a network?
Cisco: An intelligent label compression algorithm is used for path computation. Most of HW supporting Segment Routing will support 8 to 16 label push.
Will BGP-LA take over RSVP?
Cisco: BGP-LS is used for propagating link-state and TE attributes to controller. RSVP signaling is not used.
Can you load balance traffic across different segments?
Is the TE PAth is used to all traffic/services towards PE2? Or can we divert traffic for a specific service/traffic?
Cisco: We can use policy-based routing to steer subset of traffic to PE2.
Are you supporting EL for ECMP (in order to improve the load balancing hash)?
Cisco: It is a roadmap feature for now.
If TI-LFA is used will the label stack be changed or each router will use its own backup interface to get the next label of existed label stack?
Cisco: Yes, the backup label stack is chosen by the point of local repair.
Is PCEP a kind of tool to dynamically create/delate SR-TE?
Cisco: PCEP is a protocol used for TE path computation. It can also be used to instantiate, report, and delegate tunnels.
How will the WAE measure the delay of the links?
Cisco: The router measures the link and reports to WAE.
Where does the prefix-SID value come from?
Cisco: The SID is configured manually by a tool or operator and learn via IGP.
Do you know the number of RFC?
Cisco: We do have many RFCs. Go to www.segment-routing.net. There are a lot of tutorials posted with more to come.
What are the constrains supported in WAE?
Cisco: Today, we support latency and avoidance but have plans to support disjointness and capacity in the future.
Does WAE have the capacity to be used in each link of the network?
Cisco: WAE can use the demand-deduction algorithm to predict traffic demands and in XR 6.0.0 (CCO Dec ’15), we will support Demand Matrix via XR-Telemetry.
Does the convergence depend on the PCEP update sent by WAE after detecting link failure (BGP-LS update)?
Cisco: Convergence is received by WAE from BGP-LS updates and WAE correlates the appropriate update to the Segment Routing contract that has been deployed and controlled by WAE.
How latency monitored? Can you give us more details? And who is informing the PCE about it?
Cisco: In the demonstration we used IP SLA to monitor delay on the links. The resulting information was used to adjust link’s TE metric. This ultimately, triggers a BGP-LS update message towards the controller.
Is Segment Routing applicable to L2VPN?
Cisco: Segment Routing is agnostic of the service layer. It can carry L3VPN or L2VPN services. Segment Routing is concerned with setting up the transport LSPs (PSN).
Is Segment Routing supported by OSPF?
Cisco: Yes, Segment Routing introduces extensions to both IS-IS and OSPF in order to propagate label information. IOS XR implementation supports both of them.