Introduction
In this chapter, we delve into the SRv6 core concepts, exploring the SRv6 extension header, SRV6 SID, the SRv6 packet forwarding process, protocol extensions rooted in SRv6, and the realm of SRv6 reliability. SRv6 boasts the heritage of source routing mechanisms, introducing a captivating three-dimensional programming realm. Capitalizing on SRv6’s inherent IPv6 attributes, it’s seamlessly deployable alongside IPv6 devices within existing networks, streamlining network evolution. What’s more, SRv6 champions novel reliability technologies (such as TI-LFA and midpoint protection) that harness SRv6 explicit paths for post-failure recovery, bolstering fault protection within IP networks.
Why SRv6 Embraces Native IPv6 Technology?
The inseparable link between SRv6 and IPv6 is indisputable. As elucidated in RFC 8200, an IPv6 packet comprises three fundamental components: the IPv6 basic header, the IPv6 extension header, and the upper-layer Protocol Data Unit (PDU). Let’s dissect the IPv6 packet format:
The IPv6 basic header, boasting eight fields and a steadfast length of 40 octets, is an indispensable element in every IPv6 packet. This header serves as the conduit of rudimentary packet forwarding intelligence, a piece of information dissected by all devices along the corresponding forwarding trajectory.
Conversely, an upper-layer PDU typically comprises an upper-layer protocol header paired with its payload, which could be an ICMPv6, TCP, or UDP packet.
The IPv6 packet format is meticulously engineered to streamline the IPv6 basic header. In contrast to the IPv4 header, the IPv6 variant excludes fields like Fragment Offset, Header Checksum, and Options, instead embracing the Flow Label field. This design choice simplifies and enhances the efficiency of IPv6 header processing. Furthermore, IPv6 leverages extension headers to accommodate a plethora of options sans necessitating alterations to the existing packet format, rendering it remarkably flexible while preserving the elegance of packet headers.
Positioned betwixt the IPv6 basic header and the upper-layer PDU, IPv6 extension headers can grace an IPv6 packet. Or, conversely, none at all. The source node of a packet incorporates one or more extension headers when other nodes demand specialized handling.
In instances where multiple extension headers come into play, the Next Header field takes center stage, signifying the forthcoming header type. As depicted in Figure 4-1, the Next Header field in the IPv6 basic header reveals the type of the initial extension header, which in turn designates the type of the subsequent extension header, and so forth. Ultimately, in the last extension header, the Next Header field unveils the upper-layer protocol type.
IPv6 extension headers and their corresponding protocol numbers are integral to routing device decisions. The protocol number, as dictated by the Next Header field in the basic header, guides the routing device in determining whether an extension header warrants scrutiny and processing. Notably, SRV6 implementation transpires through the RH extension, sans any need to overhaul the original IPv6 packet’s encapsulation structure. This signifies that SRv6 packets retain the status of valid IPv6 entities, readily identifiable by conventional IPv6 devices. Consequently, SRv6 is heralded as a bona fide native IPv6 technology. Its innate IPv6 attributes pave the way for harmonious coexistence with commonplace IPv6 devices, bestowing impeccable compatibility within existing networks.
The transition from IP/MPLS back to native IPv6 signifies a momentous milestone, ushering MPLS out of the realm of IP networks. This transition champions protocol simplification and universal adoption of IPv6. With SRv6 at the helm, services can effortlessly reach their destinations, provided the requisite routes remain accessible. SRv6 enables services to traverse Autonomous Systems (AS) with remarkable ease, thanks to its AS spanning prowess. This streamlines network deployment and catalyzes network expansion.
Conclusion
In conclusion, this article has unveiled the core concepts of SRv6, shedding light on its extension header, SRV6 SID, packet forwarding process, protocol extensions, and reliability aspects. SRv6’s integration of source routing mechanisms and its seamless compatibility with IPv6 devices make it a compelling choice for network evolution. Moreover, the incorporation of novel reliability technologies enhances fault protection within IP networks, making SRv6 a noteworthy technology in the realm of networking.