ALTO WG H. Wang Internet-Draft Tongji University Intended status: Informational July 8, 2016 Expires: January 9, 2017 Synchronization of Distributed ALTO Servers draft-wang-alto-dist-sync-00 Abstract This document imposes the challenges and initial solutions that can be expected for the composing problem of cross-domain ALTO servers. The basic idea and problem space for composing is to solve the problem of synchronization. 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 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. Wang Expires January 9, 2017 [Page 1] Internet-Draft Synchronization of Distributed ALTO Servers July 2016 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Problem Statement . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Challenges . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Challenges about Network Map Synchronization . . . . . . 4 2.2. Challenges about Cost Map Synchronization . . . . . . . . 4 2.3. Challenges about Endpoint Cost Synchronization . . . . . 4 3. Solution Proposal . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Step1: Distributed ALTO Servers Discovery . . . . . . . . 4 3.2. Step2: Real-time incremental update using SSE . . . . . . 4 3.3. Step3: Network trackers between neighbour partitions. . . 5 4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. Considerations for Consistency . . . . . . . . . . . . . 5 4.2. Considerations for Update Frequency . . . . . . . . . . . 5 4.3. Considerations for ALTO Topology Extension . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Informative References . . . . . . . . . . . . . . . . . 6 8.2. Normative References . . . . . . . . . . . . . . . . . . 6 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction In some sceneries that one individual ALTO servers can hardly handle, such as in large-scale distributed network, or in the network combined with different ISPs, the conceptions of network partition and cross-domain ALTO servers should be introduced. In each network partition, we assume that there is an ALTO server to provide network information. Hence one possibility is to using small glimpse of each network partition to compose the information of whole complete network. The basic idea and problem space for composing is to solve the problem of synchronization. This document imposes the challenges and initial solutions that can be expected for the composing problem of cross-domain ALTO servers. In the discussion session, the problems of synchronization of distributed ALTO servers that we found but haven't given a solution are listed, such as the consistency and the update frequency. Wang Expires January 9, 2017 [Page 2] Internet-Draft Synchronization of Distributed ALTO Servers July 2016 1.1. Problem Statement Before touching the real problem of synchronization, we assume the network settings as below: +----------------------------------------------------------+ | .----------. ___ Network | | | ISP1 | .-----------. / Partition | | | ALTO +--------+-------| ISP 2 |/ | | | Server| | | ALTO | | | `----------' | | Server| | | .----------. | `-----------' | | | ISP3 | |---- | | | ALTO +-------/ \ ... ... | | | Server| | | `----------' | | Complete Network | +----------------------------------------------------------+ Figure 1: Network Partitions. In each network partition, there is an individual ALTO server. Each ALTO server will track and can only track the information of its own network. Theoretically, by tracking the information provided by each ALTO servers, a whole picture of the complete network information will emerge. However, to synchronize the existing and coming information from different network partitions can be a big challenge. 1.2. Terminology o Network Partition: infrastructures in partial network with connectivity. o ECS: Endpoint Cost Service o SSE: Server Sent Event 2. Challenges Implementing distributed ALTO servers architecture is not easy because of the synchronization problem. There are several challenges about distributed ALTO servers synchronization. This document will focus on discussing about the challenges in three major services of ALTO: network map service, cost map service and endpoint cost service. Wang Expires January 9, 2017 [Page 3] Internet-Draft Synchronization of Distributed ALTO Servers July 2016 2.1. Challenges about Network Map Synchronization In the previous design, different servers can have identical names. When it comes to compose the whole network, it will introduce collisions. 2.2. Challenges about Cost Map Synchronization How to unify the network map dependency of cost map? How to compute or indicate the cost between the PIDs in the different network partitions? 2.3. Challenges about Endpoint Cost Synchronization How to compute the cost between the endpoints in the different network partitions? 3. Solution Proposal This document proposed a basic workflow to make distributed ALTO servers be able to synchronize with each others. 1. Distributed ALTO servers discovery; 2. Real-time incremental update using SSE between ALTO server; 3. Network trackers between neighbour partitions. Following will talk more details about these three steps. 3.1. Step1: Distributed ALTO Servers Discovery The ALTO servers need to find each others before make any information aggregation. So there need to be some server discovery protocols deployed in the network. The draft [ALTO-XDOM-DISC] proposed a cross-domain server discovery protocol and we can borrow it as well. 3.2. Step2: Real-time incremental update using SSE Each ALTO server can subscribe the incremental update of the network map, cost map and endpoint cost service resources in the other ALTO servers. When the network information update, all of ALTO servers will receive the update incrementally. Wang Expires January 9, 2017 [Page 4] Internet-Draft Synchronization of Distributed ALTO Servers July 2016 The draft [ALTO-SSE] gave a solution to implement real-time incremental update by using SSE. 3.3. Step3: Network trackers between neighbour partitions. In the current network settings, the network trackers will only provide the network information inside their own network partitions. It is impossible to get the network information between network partitions because there is no components in the architecture tracking these information. This document proposed a basic solution to solve this problem. The solution is to add some new network trackers between neighbour partitions in the network. 4. Discussion 4.1. Considerations for Consistency Till now there is no solution to promise the consistency between different network partitions. 4.2. Considerations for Update Frequency TBD 4.3. Considerations for ALTO Topology Extension Suppose ALTO will provide topology information in future, how do we specially compose the topology information from different network partition? Most importantly, at which specific frequency should we update the topology information? 5. IANA Considerations This document does not define any new media type or introduce any new IANA consideration. 6. Security Considerations This document does not introduce any privacy or security issue not already present in the ALTO protocol. 7. Acknowledgement Wang Expires January 9, 2017 [Page 5] Internet-Draft Synchronization of Distributed ALTO Servers July 2016 8. References 8.1. Informative References [DRAFT-DEPLOYMENT] Stiemerling, M., Kiesel, S., Scharf, M., Seidel, H., and S. Previdi, "ALTO Deployment Considerations", 2016, . [DRAFT-SSE] Roome, W. and Y. Yang, "ALTO Incremental Updates Using Server-Sent Events (SSE)", 2015, . [DRAFT-XDOM-DISC] Kiesel, S. and M. Stiemerling, "Application Layer Traffic Optimization (ALTO) Cross-Domain Server Discovery", 2016, . 8.2. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", March 1997, . [RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", Oct 2010, . [RFC7285] Alimi, R., Penno, R., Yang, Y., Kiesel, S., Previdi, S., Roome, W., Shalunov, S., and R. Woundy, "Application-Layer Traffic Optimization (ALTO) Protocol", 2014, . Author's Address Haoran (May) Wang Tongji University 4800 Cao'an Road Shanghai 201804 China Email: whr_hr_r@163.com Wang Expires January 9, 2017 [Page 6]