Introduction:
Segment Routing with IPv6 data plane, commonly known as SRv6, has emerged as a transformative technology in the networking world. Building upon the foundation of Segment Routing (SR) and IPv6, SRv6 combines the best of both worlds, integrating routing and MPLS capabilities while enhancing network programmability. Since its early proposal in 2013, SRv6 has seen significant development, culminating in the revolutionary SRv6 Network Programming architecture. This article explores the evolution of SRv6, its capabilities, industry reception, and how it is reshaping the future of IP bearer networks.
The Genesis of SRv6:
Segment Routing (SR) was initially introduced as a versatile architecture applicable to both MPLS and IPv6 data planes. SR-MPLS employed MPLS labels to encode Segment Identifiers (SIDs), whereas SRv6 utilized IPv6 addresses as SIDs. While SR-MPLS found early adoption due to its maturity, SRv6 was initially considered a distant goal with limited programmability. Its early objective was to steer traffic by inserting IPv6 addresses of nodes and links into Segment Routing headers (SRH).
The Evolution to SRv6 Network Programming:
In March 2017, a significant breakthrough occurred with the submission of the SRv6 Network Programming draft to the Internet Engineering Task Force (IETF). This marked the transition of SRv6 from a basic traffic-steering mechanism to a sophisticated network programming paradigm. SRv6 Network Programming divided the 128-bit SRv6 SID into Locator and Function fields. The Locator provided routing capabilities, while the Function represented processing behaviours and identified services.
Enhancing Programmability and Supporting New Services:
The ingenious design of SRv6 SIDs, combining routing and MPLS capabilities, significantly amplified the programmability of networks. This, in turn, has opened doors for innovative service delivery, intelligent connection management, and better support for new services. The integration of SRv6 into IP bearer networks has become crucial in meeting the demands of the 5G and cloud era.
Industry Reception and Milestones:
SRv6 has garnered immense attention within the networking industry. The world’s first SRv6 Industry Roundtable, held during the MPLS+SDN+NFV World Congress 2019 in Paris, reinforced the notion that SRv6 is the next-generation core protocol for IP bearer networks. Experts unanimously agreed on the necessity for full SRv6 capabilities in bearer networks to embrace intelligent connections and meet evolving requirements.
Industry activities, such as China’s SRv6 industry salon, have played a pivotal role in fostering discussions, promoting innovation, and releasing SRv6 Technology and Industry White Papers. Notably, the European Advanced Networking Test Center (EANTC) conducted successful SRv6 interoperability tests, validating its commercial deployment capabilities.
IETF’s standards work has achieved significant milestones, standardizing the SR architecture (RFC 8402) and basic SRv6 features (RFC 8754 and RFC 8986). With ongoing promotion of IGP, BGP, and VPN extensions for SRv6, the protocol’s maturity will spur further developments within the SRv6 industry.
The Complexity of SR-MPLS and the Enhanced Versatility of SRv6
SR-MPLS, while offering commendable path programmability, faces limitations in supporting services that require metadata handling, such as Service Function Chaining (SFC) and In-situ Operations, Administration, and Maintenance (IOAM). These limitations stem from the relatively constrained extensibility provided by MPLS encapsulation. Moreover, the manner in which MPLS adds labels to the IP packet header compromises the universality of IP technology within packets. Consequently, network devices must support MPLS label forwarding hop by hop, thereby imposing heightened demands on network equipment. As a result, MPLS remains a dedicated technology primarily utilized in carriers’ backbone networks. Its deployment in data centers is rare, confined mostly to carriers’ backbone networks or new metro networks. This inherent constraint leads to the classification of SR-MPLS as the next-generation evolution of MPLS.
In contrast, SRv6, based on the IPv6 data plane, not only inherits all the advantages of SR-MPLS but also offers superior compatibility and extensibility due to its native IPv6 attributes. The extension of SRv6 SIDs bestows upon it powerful network programming capabilities that SR-MPLS lacks.
Conclusion:
The rapid migration to IPv6, coupled with the exhaustion of IPv4 addresses, has accelerated the development and adoption of SRv6-based applications. The evolution of SRv6 from a simple traffic-steering mechanism to a powerful network programming paradigm demonstrates its potential to revolutionize network programmability and shape the future of IP bearer networks. As industry activities continue to thrive and standards mature, SRv6’s overwhelming development promises an exciting era of intelligent, programmable, and dynamic networks.