]> Huawei Technologies

China shihang9@huawei.com

China Broadcast Mobile Network Company

China yangtianle@10099.com.cn

Routing Computing-Aware Traffic Steering This document analyses different methods for distributing the computing metrics from service instances to the ingress router. Discussion Venues Discussion of this document takes place on the Computing-Aware Traffic Steering Working Group mailing list (cats@ietf.org), which is archived at . Source for this draft and an issue tracker can be found at .

Introduction Many modern computing services are deployed in a distributed way. Multiple service instances deployed in multiple sites provide equivalent function to the end user. As described in , traffic steering that takes computing resource metrics into account would improve the quality of service. Such computing metrics are defined in . This document analysis different methods for distributing these metrics.

Conventions and Definitions The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here. This document uses terms defined in . We list them below for clarification.

• Computing-Aware Traffic Steering (CATS): An architecture that takes into account the dynamic nature of computing resources and network state to steer service traffic to a service instance. This dynamicity is expressed by means of relevant metrics.
• CATS Service Metric Agent (C-SMA):Responsible for collecting service capabilities and status, and reporting them to a CATS Path Selector (C-PS).
• CATS Path Selector (C-PS): An entity that determines the path toward the appropriate service location and service instances to meet a service demand given the service status and network status information.

Requirement of distributing computing metric The CATS functional components are defined in (see , the figure is replicated here for better understanding). C-SMA is responsible for collecting the computing metrics of the service instance and distributing the metrics to the C-PSes. A C-PS then selects a path based on the computing metrics and network metrics.

CATS Functional Components

Option 1: Centralized C-SMA + Centralized C-PS The computing metrics can be collected internally with a hosting infrastructure by a centralized monitor of the hosting infrastructure. Various tools such as Prometheus for this purpose. The monitor can pass the metrics to a network controller, which behaves as a C-PS. Then, the network controller calculates the optimal path and distribute the paths to CATS ingress routers. When a service request arrives at the CATS ingress router, it just steers the request to the path. The network controller distributed the metric update to the C-PS using south-bound protocol.

Option 2: Centralized C-SMA + Distributed C-PS Similar to option 1, the network controller does not calculate the path. It just passes the computing metrics received from the cloud monitor to the C-PS embedded in a CATS ingress router. The C-PS at each CATS ingress router will proceed with path computation locally.

Option 3: Distributed C-SMA + Centralized C-PS The C-SMA can be deployed in a distributed way. For example, C-SMA running at each site collects the computing metrics of the service instances running in a site. Then, it reports the metrics to a network controller, which behaved as a C-PS. The network controller calculates the best path for a service and distribute the path to a CATS ingress router.

Option 4: Distributed C-SMA + Distributed C-PS Similar to option 3, each C-SMA collects the computing metrics of each site. Then it needs to distribute the metric to C-PS at each ingress router. It can do so directly or through a network controller.

Comparaison Comparison between different option

	Option 1	Option 2	Option 3	Option 4
Protocol	None	Southbound	Southbound	Southbound or Eastbound
CATS router requirement	Low	High	Low	High
Network controller requirement	High	Low	High	Low

Security Considerations TBD

IANA Considerations This document has no IANA actions.

References Normative References In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References China Mobile Huawei Technologies Orange Telefonica Huawei Technologies Huawei Technologies China Unicom Distributed computing is a tool that service providers can use to achieve better service response time and optimized energy consumption. In such a distributed computing environment, providing services by utilizing computing resources hosted in various computing facilities aids support of services such as computationally intensive and delay sensitive services. Ideally, compute services are balanced across servers and network resources to enable higher throughput and lower response times. To achieve this, the choice of server and network resources should consider metrics that are oriented towards compute capabilities and resources instead of simply dispatching the service requests in a static way or optimizing solely on connectivity metrics. The process of selecting servers or service instance locations, and of directing traffic to them on chosen network resources is called "Computing-Aware Traffic Steering" (CATS). This document provides the problem statement and the typical scenarios for CATS, which shows the necessity of considering more factors when steering traffic to the appropriate computing resource to best meet the customer's expectations and deliver the requested service. China Mobile China Mobile Huawei Technologies ZTE New H3C Technologies This document describes the considerations and the potential architecture of the computing information that needs to be notified in the network in Computing-Aware Traffic Steering (CATS). Huawei Technologies China Mobile Orange Telefonica Juniper Networks, Inc. ZTE Verizon Inc. This document describes a framework for Computing-Aware Traffic Steering (CATS). Particularly, the document identifies a set of CATS components, describes their interactions, and exemplifies the workflow of the control and data planes.

Acknowledgments The author would like to thank Xia Chen, Guofeng Qian, Haibo Wang for their help.