Source packet routing in networking, or SPRING, is a standards-based approach to segment routing that is gaining a lot of traction among service providers and cloud operators as they consider new technologies and architectures to efficiently handle their market demands.
With SPRING, a packet is steered through the network using an ordered list of instructions that is applied as an ordered stack of labels by the source node. This source-applied label approach yields significant benefits that make it appealing for the future of IP networking:
- Since all necessary instructions to reach the destination are encoded at the source node, "maintaining state" is not required at any of the intermediate nodes along the route. Relaxing the need to maintain state in all routers eliminates a lot of the operational complexity associated with MPLS traffic engineering. Although explaining the mechanics of SPRING is beyond the scope of this article, the key point is that the implementation is far simpler than previous traffic engineering methods.
- SPRING is complemented by centralized control models, including SDN. For example, centralized controllers that maintain a global view of the network can make decisions based on the global network state, encode those decisions as segments, and push them into the network as label stacks.
- SPRING is fully compatible with existing MPLS networks. In fact, segments are encoded as MPLS labels to run on the existing MPLS network and with no changes required to existing hardware.
- SPRING standards are in development within multiple Internet Engineering Task Force (IETF) working groups, and the importance of standardization cannot be overstated. Operators have learned through hard experience that implementing proprietary technologies proves costly, particularly when the new technologies touch large portions of their networks (such as the IP network). SPRING, which describes a standardized implementation of earlier, proprietary segment routing technologies, removes this barrier to adoption.
Even as SPRING continues to mature through the standards track, early adopters are validating a variety of practical use cases in their production networks. Here, too, industry progress is encouraging and rapid: Recent Heavy Reading research identifies at least three initial use cases that have increasing appeal, as highlighted below:
- IP layer protection in which SPRING performs the fast reroute (FRR) function for sub-50 ms protection switching.
- SPRING can be used to ensure the IP network meets the varied QoS, performance, latency and SLA requirements of the various applications that ride on top of it, even when the applications themselves are delivered by third-party cloud providers (such as OTT providers).
- SPRING can be used for network optimization by moving traffic around dynamically and boosting utilization across the entire network. Here, a centralized controller -- with a global network view -- is essential.
Expect to hear much more about SPRING in 2018, as both standards and use cases are further defined. To that end, I encourage you to join the June 19 Light Reading webinar entitled Network Modernization With Source Packet Routing, sponsored by Juniper Networks.
The webinar will delve into the technology and its emerging use cases, and feature speakers from BCE Inc. (Bell Canada) and Microsoft, as well as Juniper. A companion Heavy Reading white paper on the topic will be distributed to all who register for the event.
— Sterling Perrin, Principal Analyst, Heavy Reading