The networking of the Resource Pod is highly dependent on the network topology that the telco workloads deployed by the tenant require. This section describes the network building blocks as required by tenant workloads and is applicable to both VNF and CNF telco workloads.
Segments are the layer 2 networks created by NSX-T Data Center to provide connectivity between its services and the VMs. Segments form the basis of the tenant networks in the vCloud NFV OpenStack Edition platform. The primary component in the data plane of the transport nodes is N-VDS. N-VDS forwards traffic between components running on the transport node (that is between VMs) or between VMs and the physical network. In the latter case, N-VDS must own one or more physical interfaces (physical NICs) on the transport node. As with other virtual switches, an N-VDS cannot share a physical interface with another N-VDS. It can coexist with another N-VDS each using a separate set of physical NICs.
The NSX-T Data Center platform provides the ability to interconnect both virtual and physical workloads that are deployed in different logical layer 2 networks. NSX-T enables the creation of network elements like segments and gateways as software logical constructs and embeds them in the hypervisor layer, abstracted from the underlying physical hardware.
Configuring a gateway through the NSX Manager instantiates a gateway on each hypervisor. For the VNFs hosted on the same hypervisor, the East-West traffic does not leave the hypervisor for routing. The gateway is also responsible for routing East-West traffic between hypervisors. The Tier-1 gateway is deployed and managed by the tenants of the vCloud NFV OpenStack Edition platform, for routing services between their respective tenant networks within their tenancy.
In addition to providing optimized distributed and centralized routing functions, NSX-T Data Center supports a multi-tiered routing model with a logical separation between the provider routing function and the tenant routing function. This way, the concept of multitenancy is built in the routing model. The top-tier gateway is called a Tier-0 gateway, whereas the bottom-tier gateway is called a Tier-1 gateway. This structure provides both provider and tenant administrators a complete control over their services and policies. The provider administrator controls and configures Tier-0 routing and services and the tenant administrators control and configure Tier-1 routing services. Northbound, the Tier-0 gateway connects to one or more physical routers or layer 3 switches and serves as an on/off ramp to the physical infrastructure. Southbound, the Tier-0 gateway connects to one or more Tier-1 gateways.
This model also eliminates the dependency on a physical infrastructure administrator to configure or change anything on the physical infrastructure when a new tenant is configured in the data center. For a new tenant, the Tier-0 gateway simply advertises the new tenant routes that are learned from the tenant Tier-1 gateway on the established routing adjacency with the physical infrastructure.