In all Open NFV Solution deployments we come to a situation of asymmetrical port/bandwidth planning in NFVI , as an example In both Huawei solutions like based on Huawei Switch CX310, CX910, CX912 or based on HP Flex Net design normally the Down link ports are as much twice (2X) compared to up link (1X) ports but because traffic move from server to vNIC to switch module and outward for both UL and DL case so why is this so.
The answer is NFV horizontal and vertical traffic scenario as the south-north traffic takes the uplink, and the east-west traffic will takes the down link. The uplink and downlink is asymmetric because of the following reasons.
1) East-West traffic is usually greater than North-South because transactions are multiplied during the computation process. NFV based system, once it receives request from north-south direction it needs to communicate with the computing modules to compute the final result. During this process many internal transfers take place and execution thread spans many multiple computing module before delivering final response in the uplink direction.
2) The downlink handles not only computational tasks assigned to the server but it also needs to deal with the auxiliary processes relevant to the chassis and computing module health. Those include heartbeat and management transactions which are run in the background but consume switch bandwidth in parallel to computing transactions therefore additional throughput needs to be factored into.
3) The computing node redundancy requires that it has two ports are used. As result there must be 2 times more ports on the downlink.
4) If we enable (Micro segmentation) e.g. in VMware the ACL and Security analysis need to be performed on each Compute host before it leaves the server. In fact all this overhead is populated in East –West and hence the down link traffic
5) Finally In open stack HCI or High performance computing many of the functions are split from controller to host like DVR, DLR (VMware) , Neutron Host and control node . This architecture means the direction is more processing related tasks to be delegated to compute. An architecture with more processing also require lot of message exchange across the direct pipe between compute and hence leads to asymmetric traffic between uplink and downlink
This are some of key reasons why the two directions are asymmetric and that both the traffic as well as ports need to be planned this way to satisfy Fast Data Stack requirements stimulated by NFV use Cases specially for VNF involving data plane.
About Author: Sheikh is Huawei Middle East Senior Architect for NFV , Telco Cloud ,SDN with focus on ICT Service delivery through Telco DevOps . Focused to define the Roads for future 5G Core Network . Always interested in those disruptive technology driving the industry transformation