Standardization by IETF and Discussion in Open Communities on Network Virtualization and Unified Method of Configuration

1. Standardization of network virtualization technologies

The implementation of multiple virtual networks on a single network infrastructure using overlay network technologies is becoming more common thanks to software-defined networking (SDN) and network functions virtualization (NFV). This article introduces Virtual eXtensible Local Area Network (VXLAN), Ethernet virtual private network (EVPN), and Segment Routing, which are network virtualization technologies, as well as Network Configuration Protocol (NETCONF) and RESTCONF, which are network management protocols, and the OpenConfig model, a vendor-neutral data model for network management. NTT’s activities related to overlay networks are also explained.

2. Trends in standardization of data models

The standardization documents concerning NETCONF and RESTCONF described above define only protocols for communication. They do not define the content of messages. YANG, as mentioned above, is the language used for the data model (data structure) in messages. Standardization of YANG-based data models is continuing to progress. These data models can be classified into data models for service descriptions and data models for network devices (Fig. 3).

Fig. 3. Classification of data models.

The data models for service description are used for layer 2 and 3 virtual private networks (VPNs) as examples. Layer 3 VPN service data models are already standardized as RFC 8299. Network device data models are used for configuring network interfaces and routing protocols. These data models for configuring network devices have been standardized by IETF and also defined by OpenConfig [3], an organization of service providers such as Google, Microsoft, Facebook, AT&T, BT, and Comcast. Some OpenConfig data models are already implemented in the devices of well-known router vendors. Hence, OpenConfig has the potential to become a common implementation led by service providers for network environments employing the products of multiple vendors. Furthermore, OpenConfig defines not only data models for IP transport devices but also data models for optical devices.

3. Trends in new network virtualization technologies

To date, virtualized networks have been achieved by using MPLS or IP tunneling such as VXLAN. The concept of Segment Routing [4] discussed in the SPRING (Source Packet Routing in Networking) WG in IETF may change the situation. The data plane technology expected to be used for Segment Routing is MPLS (SR-MPLS) or IPv6 (SRv6). Segment Routing is a source routing technology. It can control the forwarding path from the source node by using an embedded node list in a packet header. Therefore, Segment Routing is one of the technologies expected to be implemented to achieve service function chaining. It also enables fast rerouting achieved by TI-LFA (Topology Independent Loop Free Alternative) when routes change in failure cases. Moreover, SRv6 will be able to provide layer 2 and 3 VPNs [5], which have thus far only been achieved on MPLS, on IPv6 data planes by giving new functions to part of the IPv6 address. Hence, SRv6 is expected to be a unified data plane.

4. NTT activities

NTT Network Service Systems Laboratories is developing Multi-Service Fabric (MSF) [6] and publishing it as open source software [7]. MSF is an SDN system that configures and manages multiple vendors’ merchant-silicon-based network devices including white-box switches via NETCONF and other protocols. It is used for deploying layer 2 overlay networks based on VXLAN with EVPN and layer 3 overlay networks based on MPLS to a wide area. MSF was used in a collaborative proof of concept (PoC) [8, 9] with an APAC (Asia Pacific) carrier. In addition, it was introduced into a PoC environment by Dimension Data Asia Pacific [10], which is an NTT Group company. MSF uses IP routing technologies including EVPN to achieve fault tolerance and to prevent high loads from concentrating at a particular node. NTT has joined open communities that carriers and OTT (over the top) players lead collaboratively such as ONF (Open Networking Foundation) and TIP (Telecom Infra Project) to discuss fault tolerant networks achieved by autonomous mechanisms.

References

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Hitoshi Irino Senior Research Engineer, Transport Network Innovation Project, NTT Network Service Systems Laboratories*. He received a B.A. in environmental information and an M.A. in media and governance (I.T.) from Keio University, Kanagawa, in 2003 and 2005. He joined NTT Network Service Systems Laboratories in 2005. He researched traffic analysis technologies using flow information such as NetFlow/IPFIX (IP Flow Information Export) and proposed drafts about IPFIX in IETF as part of standardization efforts. He has been one of the original architects of NTT’s SDN technology for Multi-Service Fabric (MSF) since July 2014. He also initiated a project to construct an original networking OS called Beluganos using open source software and OpenFlow on merchant-silicon-based switches. He is a member of the Institute of Electronics, Information and Communication Engineers (IEICE). *He moved to NTT Communications in July 2018.