Computing-Aware Traffic Steering (cats) Many service architectures create multiple service instances. These instances are often geographically distributed to multiple sites, and a single site may support multiple instances of a service. The services are provided on computing platforms and are generically referred to as "compute services". The CATS (Computing-Aware Traffic Steering) working group (WG) is chartered to consider the problem of how the network edge can steer traffic between clients of a service and sites offering the service. Since, for some services (for example, the evolution of networked AR/VR, and deployment of autonomous and networked vehicles), the performance experienced by clients will depend on both network metrics such as bandwidth and latency, and compute metrics such as processing, storage capabilities, and capacity, there is a need for a solution that can optimize how a network edge node steers traffic based on these metrics, as appropriate to the service. Although the specific optimization function will likely differ between services, implementations, and deployments, there is a need for a general framework for the distribution of compute and network metrics and transport of traffic from network edge to service instance. It also is likely that some set of common metrics can be identified. The CATS WG will concern itself with these issues. The IETF is working on exposing network conditions to endpoints (notably ALTO) and load balancing/service selection at layers 4 and 7 (for example, related to the selection of SIP servers). Specific characteristics that may distinguish CATS from other work include the desire to integrate both network and compute conditions in the optimization function that informs the steering applied by the network edge nodes, and the desire to operate that function on nodes within the service provider's network, logically separated from service operation. Exposure of network and compute conditions to applications is not in the scope of CATS. Because of their experience and prior work in collecting and exposing network conditions for use in selecting paths and servers, the CATS WG will seek advice and expertise from the ART and TSV areas. The assumed model for the CATS WG is an overlay network, where a network edge node makes a decision based on the metrics of interest, and then steers the traffic to a node that serves a service instance, for example using a tunnel. The CATS WG will focus on single domain models. Architectures that require the underlay network to be service-aware are out of scope. The CATS WG will analyze the problem in further detail and produce an architecture for a solution. Ideally, that architecture will be one that can be instantiated using existing technologies. The CATS WG is chartered to work on the following items: o Groundwork may be documented via a set of informational Internet- Drafts, not necessarily for publication as RFCs: * Problem statement for the need to consider both network and computing resource status. * Use cases for steering traffic from applications that have critical SLAs that would benefit from the integrated consideration of network and computing resource status. * Requirements for commonly agreed computing metrics and their distribution across the overlay network, as well as the appropriate frequency and scope of distribution. o Overall CATS framework & architecture: * This work encompasses the various building blocks and their interactions, realizing a CATS control and data plane that addresses the identified problems and requirements in the groundwork, including methods for distributing necessary information to utilize the identified metrics in CATS use cases. This will also cover OAM, scalability, and security aspects. o Additional groundwork to include: * Analyze the suitability and usefulness of computing and networking metrics for traffic steering decisions in CATS with a CATS metrics ontology as a possible outcome. * Analyze methods for distributing the necessary information to utilize the identified metrics in CATS use cases. o Applicability of existing tools and mechanisms: * Analysis of implementing the CATS control and data plane using existing mechanisms, including identifying the limitations of existing tools in fulfilling requirements. * Study potential new approaches for the CATS control and data plane solution that can fill the identified gaps in existing tools and solutions. * Study FCAPS (fault, configuration, accounting, performance, security) requirements, mechanisms, and suitability of existing messaging protocols (NETCONF) and data models (YANG).