From previous posts, we gained a general understanding of the SDN-based IP+optical solution. In this post, we will have a look at how this solution implements automated multi-layer network deployment.

What Is Automated Multi-layer Network Deployment?

Automated multi-layer network deployment refers to the process in which the centralized SDN controller drives the IP and optical layers to automatically establish IP links and optical paths based on network deployment configurations delivered through the NetMatrix, preparing the network for subsequent service deployment. The centralized SDN controller obtains the multi-layer network topology information from forwarders and the NetMatrix and constructs a resource pool with optical resources and router ports.

This resource pool enables an IP+optical network to quickly adapt to network traffic changes by adjusting network topology and bandwidth resources, improving network utilization and deployment flexibility.

Non-SDN-based networks are often confronted with problems such as long network deployment time, high resource consumption, heavy site maintenance workload, and complex topology design.

The SDN-based IP+optical solution, which allows for agile automated network deployment, significantly reduces network OPEX and improves network efficiency.

VNTM, a Bridge Between IP and Optical Layers

The virtual network topology manager (VNTM) is essential to IP+optical synergy. Now lets have a look at how the VNTM implements resource integration between the IP and optical layers.

After the optical network devices and resources are deployed, the optical bandwidth pool supports many virtual IP links. These inactivated IP links form a virtual network topology (VNT), which is visible to the IP layer and can be activated on demand when IP traffic changes or requires protection.

The VNTM enables the IP and optical PCEs to work in collaboration to calculate end-to-end multi-layer paths. The virtual IP links can be dynamically activated or inactivated based on IP service requirements.

On the network shown in the preceding figure, PE1 and PE2 are reachable to each other at the optical layer, but not at the IP layer. There is no GMPLS UNI tunnel between routers P3 and P4, and the VNT link status is Down. After an end-to-end path (including the optical path) is activated between P3 and P4, a GMPLS UNI tunnel will be established between them, and the corresponding VNT link will be activated. PE1 and PE2 can then have an IP link established.

The VNT is a collection of planned virtual IP links. VNT links can share reserved optical resources. The VNT is a subset of possible IP links supported by the IP and optical resources.

?  The optical PCE refreshes VNT link status in real time based on optical resource changes.

?  A physical IP port consisting of multiple VLAN sub-interfaces or UNIIF logical interfaces can map to multiple connections in different directions.

?  A network administrator can dynamically add, delete, and modify VNT links based on network resource changes or dynamically add and delete VNT links based on traffic changes.

VNT links are Layer 3 logical links. Each VNT link maps to a GMPLS UNI tunnel. The entity of a VNT link can be regarded as a combination of the ingress nodes pigtail + transmission path + the egress nodes pigtail. A VNT link can go Up only after the corresponding GMPLS UNI tunnel goes Up. When a GMPLS UNI tunnel is Down, the corresponding VNT link is also Down.

This characteristic of VNT links allows us to conveniently adjust network resources to implement on-demand network deployment and release unneeded links in a timely manner.

                                       

 

A VNT link is established between a source C node and a sink C node, which are uniquely identified by IP router IDs (usually interface IP addresses).

A VNT link contains the following attributes:

• Cost
• MTU
• Bandwidth
• Delay
• HA (protection, restoration, or rerouting)
• SRLG constraint