ALTO WG G. Bernstein Internet-Draft Grotto Networking Intended status: Standards Track K. Gao Expires: January 9, 2017 Tsinghua University Y. Lee Huawei W. Roome M. Scharf Nokia Y. Yang Yale University July 8, 2016 ALTO Extension: Path Vector Cost Mode draft-yang-alto-path-vector-03.txt Abstract The Application-Layer Traffic Optimization (ALTO) Service has defined network and cost maps to provide basic network information, where the cost maps allow only scalar (numerical or ordinal) cost mode values. This document introduces a new cost mode called path-vector to allow ALTO clients to support use cases such as capacity regions for applications. This document starts with a non-normative example called multi-flow scheduling (or capacity region) to illustrate that ALTO cost maps without path vectors cannot provide sufficient information. This document then defines path-vector as a new cost mode. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any Bernstein, et al. Expires January 9, 2017 [Page 1] Internet-Draft ALTO Extension: Path Vector July 2016 time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on January 9, 2017. Copyright Notice Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Example: Capacity Region for Multi-Flow Scheduling . . . . . 3 3. Path-Vector Query . . . . . . . . . . . . . . . . . . . . . . 5 4. Path-Vector Response . . . . . . . . . . . . . . . . . . . . 5 5. Path-Vector in IRD . . . . . . . . . . . . . . . . . . . . . 7 6. Path-Vector in Incremental Updates . . . . . . . . . . . . . 8 7. Security Considerations . . . . . . . . . . . . . . . . . . . 8 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction The ALTO base protocol [RFC7285] is designed for a setting of exposing network topology using the extreme "my-Internet-view" representation, which abstracts a whole network as a single node that has a set of access ports, with each port connects to a set of endhosts. This "single-node" abstraction is simple and can support a wide range of applications already. A problem of this abstraction, however, is that it does not provide sufficient information for use cases that require exposure of topology information beyond the single-node abstraction, for example, Bernstein, et al. Expires January 9, 2017 [Page 2] Internet-Draft ALTO Extension: Path Vector July 2016 when there is a need to detect sharing of resources in the underlying topology (see an example in Section 3). This document goes beyond the single-node topology by introducing path vector as a new ALTO cost mode, where each path vector specifies abstracted network elements on the routing paths of a set of flows. Since the network elements on a path vector are abstract network elements defined by ALTO servers, the new path-vector cost mode provides a mechanism to allow a network to control the level of topology exposure, and at the same time better support application traffic optimization. The design of path vector is based on the ALTO WG discussions at IETF 89, with summary slides at http://tools.ietf.org/agenda/89/slides/slides-89-alto-2.pdf. The organization of this document is organized as follows. Section 2 gives a non-normative example called multi-flow scheduling to illustrate the need to introduce path vectors. Sections 3-6 specify the path vector cost mode for query, response, announcements, and incremental udpates, respectively. Sections 7 and 8 discuss security and IANA considerations. 2. Example: Capacity Region for Multi-Flow Scheduling Consider the case that routing is given. Then what application-layer traffic optimization will focus on is traffic scheduling among application-layer paths. Specifically, assume that an application has control over a set of flows F = {f1, f2, ..., f_|F|}. If routing is given, what the application can control is x1, x2, ..., x_|F|, where xi is the amount of traffic for flow i. Let x = [x1, ..., x_|F|] be the vector of the flow traffic amounts. Due to shared links, feasible values of x where link capacities are not exceeded can be a complex polytope. Specifically, consider a network as shown in Figure 1. The network has 7 switches (sw1 to sw7) forming a dumb-bell topology. Switches sw1/sw3 provide access on one side, s2/s4 provide access on the other side, and sw5-sw7 form the backbone. Endhosts eh1 to eh4 are connected to access switches sw1 to sw4 respectively. Assume that the bandwidth of each link is 100 Mbps. Bernstein, et al. Expires January 9, 2017 [Page 3] Internet-Draft ALTO Extension: Path Vector July 2016 +------+ | | --+ sw6 +-- / | | \ PID1 +-----+ / +------+ \ +-----+ PID2 eh1__| |_ / \ ____| |__eh2 | sw1 | \ +--+---+ +---+--+ / | sw2 | +-----+ \ | | | |/ +-----+ \_| sw5 +---------+ sw7 | PID3 +-----+ / | | | |\ +-----+ PID4 eh3__| |__/ +------+ +------+ \____| |__eh4 | sw3 | | sw4 | +-----+ +-----+ Figure 1: Raw Network Topology. The single-node ALTO topology abstraction of the network is shown in Figure 2. +----------------------+ {eh1} | | {eh2} PID1 | | PID2 +------+ +------+ | | | | {eh3} | | {eh4} PID3 | | PID4 +------+ +------+ | | +----------------------+ Figure 2: Base Single-Node Topology Abstraction. Consider an application overlay (e.g., a large data analysis system) which needs to schedule the traffic among a set of endhost source- destination pairs, say eh1 -> eh2, and eh3 -> eh4. The application can request a cost map providing end-to-end available bandwidth, using 'available bw' as cost-metric and 'numerical' as cost-mode. Assume that the application receives from the cost map that both eh1 -> eh2 and eh3 -> eh4 have bandwidth 100 Mbps. It cannot determine that if it schedules the two flows together, whether it will obtain a total of 100 Mbps or 200 Mbps. This depends on whether the routing paths of the two flows share a bottleneck in the underlying topology: o Case 1: If eh1 -> eh2 and eh3 -> eh4 use different paths, for example, when the first uses sw1 -> sw5 -> sw7 -> sw2, and the Bernstein, et al. Expires January 9, 2017 [Page 4] Internet-Draft ALTO Extension: Path Vector July 2016 second uses sw3 -> sw5 -> sw6 -> sw7 -> sw4. Then the application will obtain 200 Mbps. o Case 2: If eh1 -> eh2 and eh3 -> eh4 share a bottleneck, for example, when both use the direct link sw5 -> sw7, then the application will obtain only 100 Mbps. To allow applications to distinguish the two aforementioned cases, the network needs to provide more details. The path vector extension defined in this document resolves this issue. See [I-D.bernstein-alto-topo] for a survey of use-cases where extended network topology information is needed. 3. Path-Vector Query Since the key motivation of providing path vectors is for concurrent- flow settings, due to sharing of network resources, the specification is for a multi-flow setting. Also, instead of defining such queries separately for grouping of endhosts (PIDs) and individual endpoints, we define for generic sources, destinations. POST /capacityregion/lookup HTTP/1.1 Host: alto.example.com Content-Length: TBD Content-Type: application/alto-flowparams+json Accept: application/alto-costmap+json,application/alto-error+json { "cost-type" : {"cost-mode": "path-vector", "cost-metric": "bw"} }, "flows" : [ {"src": "ipv4:192.0.1.1", "dst": "ipv4:192.0.1.2"}, {"src": "ipv4:192.0.1.3", "dst": "ipv4:192.0.1.4"}, {"src": "ipv4:192.0.1.1", "dst": "ipv4:192.0.1.4"} ] } 4. Path-Vector Response An extension supporting the path-vector cost-mode MUST support the following extension of Section 11.2.3.6 of [RFC7285]: Bernstein, et al. Expires January 9, 2017 [Page 5] Internet-Draft ALTO Extension: Path Vector July 2016 object { cost-map.DstCosts.JSONValue -> JSONString<0,*>; meta.cost-mode = "path-vector"; } InfoResourcePVCostMap : InfoResourceCostMap; Specifically, the preceding specifies that InfoResourcePVCostMap extends InfoResourceCostMap. The body specifies that the first extension is achieved by changing the type of JSONValue defined in DstCosts of cost-map to be an array of JSONString; the second extension is that the cost-mode of meta MUST be "path-vector". An example cost map using path-vector is the following: Bernstein, et al. Expires January 9, 2017 [Page 6] Internet-Draft ALTO Extension: Path Vector July 2016 HTTP/1.1 200 OK Content-Length: TBA Content-Type: application/alto-costmap+json { "meta" : { "vtag" : { "resource-id": "my-costmap", "tag": "c0ce023b8678a7b9ec00324673b98e54656d1f6d" } "cost-type" : {"cost-mode": "path-vector", "cost-metric": "bw" } } }, "cost-map" : { "ipv4:192.0.1.1": { "ipv4:192.0.1.2": ["ne57"], "ipv4:192.0.1.4": ["ne57", "ne74"] }, "ipv4:192.0.1.3": { "ipv4:192.0.1.4": ["ne56", "ne67"] } } "nep-map" : { "ne57" : {"bw" : 100}, "ne74" : {"bw" : 100}, "ne56" : {"bw" : 100}, "ne67" : {"bw" : 100} } } To interpret the path vectors in a cost map, an ALTO client will need access to the properties of the abstract network elements named in the path vectors. One approach is to use a network element property service (e.g., the unified properties draft [I-D.roome-alto-unified-props]). In this design, they are included as a second map in the same message, for consistency and saving of round-trips. 5. Path-Vector in IRD Announcing the support of path vector in IRD is relatively straightforard: the mode is included as the IRD. Bernstein, et al. Expires January 9, 2017 [Page 7] Internet-Draft ALTO Extension: Path Vector July 2016 6. Path-Vector in Incremental Updates A concern is whether the design allows efficient incremental updates, on either the path vectors of the element properties. For this design, the keys along the data path allow such easy encoding. 7. Security Considerations This document has not conducted its security analysis. 8. IANA Considerations This document requires the definition of a new cost-mode named path- vector. 9. Acknowledgments The author thanks discussions with Xiao Shi, Xin Wang, Erran Li, Tianyuan Liu, Andreas Voellmy, Haibin Song, and Yan Luo. 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . 10.2. Informative References [I-D.amante-i2rs-topology-use-cases] Medved, J., Previdi, S., Lopez, V., and S. Amante, "Topology API Use Cases", draft-amante-i2rs-topology-use- cases-01 (work in progress), October 2013. [I-D.clemm-i2rs-yang-network-topo] Clemm, A., Medved, J., Tkacik, T., Varga, R., Bahadur, N., and H. Ananthakrishnan, "A YANG Data Model for Network Topologies", draft-clemm-i2rs-yang-network-topo-01 (work in progress), October 2014. [I-D.lee-alto-app-net-info-exchange] Lee, Y., Bernstein, G., Choi, T., and D. Dhody, "ALTO Extensions to Support Application and Network Resource Information Exchange for High Bandwidth Applications", draft-lee-alto-app-net-info-exchange-02 (work in progress), July 2013. Bernstein, et al. Expires January 9, 2017 [Page 8] Internet-Draft ALTO Extension: Path Vector July 2016 [I-D.roome-alto-unified-props] Roome, W., "Extensible Property Maps for the ALTO Protocol", draft-roome-alto-unified-props-00 (work in progress), July 2015. [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., Previdi, S., Roome, W., Shalunov, S., and R. Woundy, "Application-Layer Traffic Optimization (ALTO) Protocol", RFC 7285, DOI 10.17487/RFC7285, September 2014, . Authors' Addresses Greg Bernstein Grotto Networking Fremont, CA USA Email: gregb@grotto-networking.com Kai Gao Tsinghua University Beijing Beijing China Email: gaok12@mails.tsinghua.edu.cn Young Lee Huawei TX USA Email: leeyoung@huawei.com Wendy Roome Nokia/Bell Labs 600 Mountain Ave, Rm 3B-324 Murray Hill, NJ 07974 USA Phone: +1-908-582-7974 Email: wendy.roome@nokia.com Bernstein, et al. Expires January 9, 2017 [Page 9] Internet-Draft ALTO Extension: Path Vector July 2016 Michael Scharf Nokia Germany Email: michael.scharf@nokia.com Y. Richard Yang Yale University 51 Prospect St New Haven CT USA Email: yry@cs.yale.edu Bernstein, et al. Expires January 9, 2017 [Page 10]