Cloud Infrastructure (NFV and SDN)
Cloud Infrastructure (NFV and SDN)
This domain tests designing and operating virtualized network functions and separating control from forwarding. You need to know ETSI NFV building blocks, SDN interfaces, and where Juniper virtual platforms fit.
Core rules
- NFV decouples network functions from proprietary hardware: VNFs or CNFs run on NFVI, managed by MANO. ETSI MANO has NFVO for service orchestration, VNFM for VNF lifecycle, and VIM for virtualized infrastructure management, commonly OpenStack.
- SDN centralizes control-plane logic and programs forwarding devices through southbound interfaces such as OpenFlow, NETCONF/YANG, PCEP, and gRPC/gNMI. Northbound APIs expose intent to orchestration.
- Service chaining steers traffic through an ordered set of VNFs. In Contrail, service templates and service instances plus policies define the chain; the vRouter encapsulates traffic to the service VM.
- Performance depends on the data plane: DPDK, SR-IOV, and vhost-user reduce overhead; virtio alone may not meet line-rate NFV requirements.
Worked example
A tenant needs Internet-to-web traffic inspected by vSRX before reaching vMX. Create a Contrail service template with a vSRX instance, attach left and right interfaces, and write a network policy that steers the flow through the service. Reasoning: the policy provides classification and next-hop; the service instance provides the ordered VNF; the vRouter handles encapsulation. Without a service policy, the VNF is deployed but traffic bypasses it.
Traps
- Treating NFV and SDN as synonyms. NFV virtualizes functions; SDN separates control and data planes.
- Forgetting the VIM in MANO. The VNFM does not place VMs; the VIM does.
- Ignoring MTU and encapsulation overhead in overlays, which breaks large packets.