CoGS: Enabling distributed network functions with global states

A flow handover protocol to support state migration in softwarized networks

“…In addition, more specific approaches that focus on joint traffic steering and state migration of VNFs have been proposed. The most prominent ones are Split/Merge and its extension called Pico Replication, OpenNF with its extensions, CoGS , as well as a novel approach called SliM and a tagging‐based solution presented in the study of Wang et al…”

“…An example for a complementary state management solution is our E‐State ; it works seamlessly with SHarP. Other distributed state management solutions, like the recently introduced CoGS , SliM, or FogStore approaches, are also complementary to SHarP and could benefit from its loss‐less flow migration procedures. In contrast to OpenNF, our system distributes the buffering process required for loss‐less handovers to the destination VNF instances; this heavily reduces the controller load and provides better scalability.…”

“…10 In addition, more specific approaches that focus on joint traffic steering and state migration of VNFs have been proposed. The most prominent ones are Split/Merge 5 and its extension called Pico Replication, 11 OpenNF 4 with its extensions, 12,13 CoGS, 14 as well as a novel approach called SliM 15 and a tagging-based solution presented in the study of Wang et al 16 With Split/Merge, 5 an orchestrator can migrate flows and move the corresponding function state using a simple application programming interface (API) call. However, its failure recovery and migrate operation can cause lost or out-of-order state updates at the network function as flow processing is stopped during handover and arriving packets are dropped.…”

“…Based on this, the packets are either buffered in ctrl_buff (12) or sw_buff (13). During this phase, VNFn_IMPL triggers the actual state migration by requesting a state transfer from the source VNF 1 (11), which FIGURE 4 Handover procedure from the perspective of the involved VNFs and their HSLs transfers the state to the destination VNF n (14). This state transfer might take an arbitrary amount of time, depending on, eg, the used state management solution and network conditions, in which the VNFn_HSL keeps buffering incoming packets.…”