Internet Engineering Task Force Carmine Daloia Internet-Draft Lucent Technologies Expiration Date: May 2001 November, 2000 Data Communications Network (DCN) Reliability Requirements draft-daloia-dcn-reliability-00.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. 1. Abstract This contribution provides high-level reliability requirements for the Data Communications Network (DCN). Thi draft is intended to initiate work on reliability aspects of the DCN. 2. Conventions used in this document 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. 3. Introduction A Data Communications Network (DCN) is necessary to serve as the transport network for communications related to the signaling components as well as the routing components within the ASON control plane. If the ASON control plane includes other components such as auto discovery, link management, connection admission control, survivability, the DCN would also provide transport for communications related to these components as well. Figure 1 illustrates the logical representation of ASON. As shown in Figure 1, the ASON consists of the following logical interfaces/links: (i) S-UNI - User to Network Interface for signaling The S-UNI as shown in Figure 1 is the protocol between the client controller component (Client-C) and the server controller component (Server-C). (ii) S-NNI - Network to Network Interface for signaling The S-NNI as shown in Figure 1 is the protocol between two server controller components (Server-C). (iii) U-CCI - User Connection Control Interface The U-CCI as shown in Figure 1 is the protocol between the client network transport component (Client) and the client controller component (Client-C). (iv) N-CCI - Network Connection Control Interface The N-CCI as shown in Figure 1 is the protocol between the server network transport component (Server) and the server controller component (Server-C). Figure 1 The task addressed in this document is to evaluate the reliability requirements for the DCN. The reliability requirements of the DCN depend heavily on the type of communications transported over the DCN. For example if the DCN supports transport of communications related to the survivability mechanism than the reliability requirements of the DCN may be very stringent compared to if the DCN transported less time-critical messages (e.g., software download). The following assumptions are made with regard to this draft document. - The DCN topology is independent of the transport network topology (e.g., OTN topology). The logical links (i.e., S-UNI, S-NNI, U-CCI, and N-CCI) may share some common physical routes with the transport network logical links (i.e.,. O-UNI, O-NNI) but we do not require or exclude it. - The DCN can be built on top of any transport technology such as optical, SONET, or Ethernet. 4. Analysis of Failure Scenarios There are two types of failure scenarios that need to be discussed. (A) Failures that effect only the DCN (B) Failures that effect both the DCN and the underlying transport network The following sub-sections provide some discussion on the impact to overall ASON reliability under each scenario. 4.1 Failure Scenario A Failure scenario A assumes an independent failure to the DCN that does not effect the transport network. Such a failure may impact new connection setup as well as connection teardown requests from being completed due to an interruption of paths within the DCN. Figure 2 illustrates such an example. A failure occurs between the server controllers such that there is no communication path between them to exchange routing or signaling messages. Figure 2 4.2 Failure Scenario B Failure scenario B assumes a failure that effects both the DCN and the Transport Network. Figure 3 illustrates such an example. Such a scenario would again impact new connection setup as well as teardown in the transport network since communications paths within the DCN may not be available. Since the transport network is also effected by the failure there could be many new connection requests associated with the connections that were interrupted due to the failure. Also if the DCN supported communications related to survivability, the DCN may not be able to provide the necessary communications required to restore the interrupted connections. Figure 3 5. Reliability Requirements for the DCN Section 4 illustrated failure scenarios that could interrupt the communications in the DCN and its impact to the ASON network. In addition, some components (e.g., survivability) of the ASON control plane may require a highly reliable DCN for transport while others (e.g., software download) which are not as time-critical may not require reliable transport. The following lists three reliability requirements for the DCN. Requirement #1: The DCN shall support resilience between those communicating components in the ASON control plane in case of DCN failures. Requirement #2: The DCN shall support various levels of restoration depending on the reliability requirements of the communicating components (i.e., restoration can be supported between those components requiring highly reliable communications without requiring restoration to be supported between all communicating components). Requirement #3: The DCN shall provide restoration speeds which allow proper operation of the connections for which it controls (e.g., restoration speeds for communications between control plane components related to survivability must be faster than the restoration speed of the transport connections for which the components are controlling). 6. References [1] Carmine Daloia, "DCN Reliability Requirements", T1X1.5/2000-204 7. Authors' Contact Information Carmine Daloia Lucent Technologies daloia@lucent.com Expiration Date: May 2001