Network Working Group J.P.Wang INTERNET-DRAFT Y.P.Zhu Intended status: Informational U.S.T.B Expires: June 21, 2011 December 21, 2010 EA-HD: A Novel Link State Update Mechanism for ASON draft-jpwang-rtgwg-update-mech-00.txt Abstract When a connection request comes in a mesh optical network, the routers automatically choose the suitable routing paths and wavelength to it according to the network topology and link state information saved in its global link state database. Because some of these wavelengths may be released or occupied at any time, the global state database is always out of date and needed by update by some an update policy. A suitable link state update policy is critical, since that a high frequency update polity imposes heavy burden on network, while a low frequency one would increase the inaccurate of the global link state database. In this paper, we propose a link state update policy, named EA-HD policy, which considers two index of a link, one is the Hamming distance between the local link state database and the global link state database, and another is the used ratio of its wavelengths. The proposed update policy gets a trade-off between the accurate of link state information and its update cost. Simulation proves that our scheme achieve a good performance in traffic blocking probability while maintaining moderate volume of update traffic. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. 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. 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Wang&Zhu Expires - June 21, 2011 [Page 2] Internet-Draft Link State Update Mechanism December 2010 Table of Contents 1. Terminology....................................................4 2. Introduction...................................................4 3. THE ea-hd link state update mechanism..........................4 3.1 Trigger condition..........................................5 3.2 The update Algorithm ......................................5 4. The EA-HD update algorithm.....................................6 5. Analysis and conclusion........................................6 6. Security Considerations........................................7 7. IANA Considerations............................................7 8.References......................................................7 Author's Addresses................................................8 Wang&Zhu Expires - June 21, 2011 [Page 3] Internet-Draft Link State Update Mechanism December 2010 1. Terminology 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 [RFC2119]. This document uses terms from [RFC3261][1]. 2. Introduction In recent years, optical networks have great potential for better utilizing the large bandwidth provide by wavelength division multiplexing (WDM) technology. The introduction of control plane enables the optical networks into intellective. And, as the most important representative of intelligent optical networks. Automatically Switched Optical Network (ASON) becomes one of the important and hot studies in communication. The node of ASON is composed by several modules, such the protocol module, link resource manager, routing controller, connect controller, etc. In the link resource manager of each node, there is a database storing the state information of links adjacent to the node. We call the database local link state database (L-LSD) in this paper. In the routing controller of each node (or only each speaker node), there is another database where saves the state information of all the links in the network. It is named as global link state database(G-LSD). We assume that each node of the network possesses the G-LSD in our paper.To realize a light-path establishment in ASON, link state based routing and wavelength assignment(RWA) algorithms are introduced. When a connecting request comes, the RWA algorithm chooses a path from source node to destination node firstly. The path is composed by several links. Next, the algorithm chooses a set of free wavelengths for each link according to the G-LSD. At last, the link resource managers of the nodes on the path commonly select an actual free and continuous wavelength to build the connection on this wavelength. 3. THE ea-hd link state update mechanism In the G-LSD and L-LSD, we use 1 to represent that a wavelength is occupied by some a connection, and 0 to express that a wavelength is free. Thus, the state of a link with N wavelength channels can be denoted as an N-dimension array whose components are 0 or 1. For example, if a link has four wavelength channels and the first and the last wavelengths are occupied by traffic, then its state information in L-LSD is 1001. If a new coming connection request occupies the third wavelength of it, its state information in L-LSD is changed into 1011 immediately. Wang&Zhu Expires - June 21, 2011 [Page 4] Internet-Draft Link State Update Mechanism December 2010 The LSI in G-LSD is similar to that in L-LSD, except that it is a little outdated. There are two kinds of possible outdated states for a wavelength, pseudo surplus and pseudo deficient, which lead to the inaccurate of G-LSD. If a wavelength of a link is shown free in G-LDB but actually has been used by some a connection request in L-LDB, it is said to be pseudo-surplus. On the contrary, if a wavelength of a link is occupied in G-LDB but actually has been released in L-LDB, it is said to be pseudo-deficient. Still seeing the last example, if the occupied information of the third wavelength is not been updated in the G-LSD, there would generate a pseudo-surplus of the LSI in the G-LSD. The Hamming distance between the G-LSD and the L-LSD can better reflect the change of link state than the variance of available wavelengths in these two LSDs. The latter is extensive used in the previous link state update policies. We show the distinct of them by an example next. Assume that a link has four wavelength channels, and two update policies have different triggers. The first policy touches off an update when the variance of available wavelengths is greater than or equal to two, and the second one choose a trigger that the Hamming distance is larger than or equal to two. At first, the state information of this link in the L-LDB and the G-LDB are all 1100. The number of available wavelengths is an important index in update policy either, because it can reflect the degree of demand of RWA algorithms to the accurate of LSI. When the number of available wavelengths is great, the update would not be urgent, for there are many free wavelengths for RWA algorithms to choose a continuous one for all the links in the path. However, when the number of available wavelengths is little, the chance to find a same free wavelength for all the links will be small, and the update would be very urgent. Next, we expatiate upon the EA-HD update mechanism by two phases. We firstly introduce the condition to trigger an update, and then describe the EA-HD mechanism in detail. 3.1 Trigger condition Suppose that each link has N wavelength channels in total. Let A be the number of available wavelengths of a link, and d be the Hamming distance between its state information in L-LSD and in G-LSD. We define a function, named the state-variance metric function of a link, as F(d,A)=(d/N)* a^(-A/N)>=b(a>1).Assume the threshold to touch off an update is b, and a is constant to adjust the effect of d and A to F(d,A), respectively. 3.2 The update Algorithm In ASON, routing controllers of nodes possess the G-LSD and they ask Wang&Zhu Expires - June 21, 2011 [Page 5] Internet-Draft Link State Update Mechanism December 2010 the link resource manager for the L-LSD. Hence, the update of the LSI is launched by these routing controllers. In our update policy, routing controllers record the variance of free wavelengths and the Hamming distance of all its adjacent nodes. When light path for a new coming connect is established, the routing controllers of the nodes on the path update the value of these two indexes. If the trigger condition is satisfied, the corresponding routing controller will launch an update. The detailed steps of the EA-HD update policy (in a node) are described as follows. Since every request is allowed to enter the domain to search for free wavelength but does not reserve any wavelength during the Path process, BRP has longer connection setup time and lower blocking probability compared with FRP. 4. The EA-HD update algorithm Step1: When the state of some an adjacent link changes (caused by the establishment or remove of a light-path), the link resource manager (LRM) of this node updates the LSI. Step2. LRM sends the change to the routing controller (RC). Step3. RC calculates the value of d and A, furthermore, the value of F(d,A). Step4. If the formula F(d,A)>=b is satisfied, RC updates the corresponding LSI in G-LSD of itself and notifies the protocol module to send LSA to all other nodes. Else, go to step1. Step5. When a node receives LSA of other nodes, its RC updates the corresponding LSI in the G-LSD. 5. Analysis and conclusion In this draft, we propose a novel link state update mechanism for ASON which considers two indexes of a link, one is the Hamming distance of LSI between G-LSD and the L-LSD, and another is the number of available wavelengths in the link. Exponential function is quoted which can be more flexible to reflect state changes in link. The proposal update policy is compared with three existing mechanism. Simulations show that there are a lot of advantages of our mechanism. At first, Update is effective and timely when the network state changed frequent or small number of available wavelengths. Secondly, our mechanism reaches trade-off between network traffic loads and accuracy of LSI. Thirdly, it achieves good performance in traffic block probability while maintaining moderate volume of update traffic. Wang&Zhu Expires - June 21, 2011 [Page 6] Internet-Draft Link State Update Mechanism December 2010 6. Security Considerations The presence of the Reason header in a response does not affect the treatment of the response. Including such a header by an untrusted entity could adulterate the reactions of the originating entities. E.G. sending back a cause value "87" can cause an announcement within the PSTN/ISDN saying that the call was rejected due to the Closed User Group service. Therefore it is RECOMMENDED to include the Reason header information in Responses only by trusted entities as it is described within [RFC3325][7]. 7. IANA Considerations This document does not have any implications for IANA. 8.References [1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [2] BERGER L. RFC3473, Generalized multi-protocol label switching signaling resource reservation protocol-traffic engineering (RSVP- TE) Extensions[S]. 2003. [3] Jennings, C., Peterson, J., and M. Watson, "Private Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks", RFC 3325, November 2002. Wang&Zhu Expires -June 21, 2011 [Page 7] Internet-Draft Link State Update Mechanism December 2010 Authors' Addresses Jianping Wang University of Science and Technology Beijing NO.30 XueYuan Road, HaiDian, Beijing 100083 P.R China Email: zhuyanping_06@163.com Wang&Zhu Expires - June 21, 2011 [Page 8] Internet-Draft Link State Update Mechanism December 2010