Network function virtualization (NFV) is a promising technique of high quality, flexible and scalable service for telecommunication companies clients and for enterprise data center clients. One of the important capabilities of this technique is providing a virtual service as a combination of multiple virtual functions. There are two types of virtual functions: those intended for a single customer (su-VF) and those that can serve multiple users (mu-VF). In case when output of mu-VF is chained with inputs of several different su-VFs, there is a need for a mechanism of identification and separation of users network flows passing through mu-VF to allocate them correctly between inputs of su-VFs in the NFV infrastructure. In the cloud environment, it is not always possible to use VLAN tags, IP and MAC addresses for that. In this paper, we consider the problem of identification of network traffic coming from a certain user inside an NFV platform and present a solution implemented in C2 MANO-platform.