Network Working Group Eiji Oki Internet Draft NTT Expiration Date: August 2002 Nobuaki Matsuura NTT Wataru Imajuku NTT Kohei Shiomoto NTT Naoaki Yamanaka NTT February 2002 Requirements of optical link-state information for traffic engineering draft-oki-ipo-optlink-req-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. Copyright Notice Copyright (C) The Internet Society (2002). All Rights Reserved. Abstract In a limited/non-wavelength-convertible (LNWC) optical network, a wavelength is restricted to be converted into another wavelength on an optical path due to the limitation of wavelength converters at an optical cross-connect. This document describes requirements of optical link-state information for traffic engineering to solve the routing and wavelength assignment (RWA) problem in LNWC network. Additional link-information extensions for LNWC network are Oki [Page 1] draft-oki-ipo-optlink-req-00.txt February 2002 presented. By using the information, extensions of OSPF and RSVP-TE are proposed. 1. Introduction Traffic engineering (TE) in optical networks is useful to efficiently utilize network resources, which are fibers, wavelengths, and node capacities, etc. In GMPLS networks, a source node finds an appropriate route and wavelength based on collected optical link- state information with a routing protocol as such as Open Shortest Path Finding (OSPF) [GMPLS-OSPF], and set up an optical path by using a signaling protocol such as RSVP-TE [GMPLS-SIG][GMPLS-RSVP]. A wavelength-division multiplexing (WDM) optical network are mainly categorized into two types in terms of wavelength conversion capability. One is a limited/non-wavelength-convertible (LNWC) optical network. The other is a wavelength-convertible (WC) optical network. In LNWC network, a wavelength is limitedly or not converted into another wavelength on an optical path. Because of the limitation of wavelength converters at optical cross-connects (OXCs), an optical path must use the same or limited wavelength(s) through an optical path. When an optical path is set up, the routing and wavelength assignment (RWA) problem has to be solved. On the other hand, in WC network, any wavelength can be converted into any wavelength at OXC on an optical path. This draft describe requirements of optical link-state information for traffic engineering to solve the RWA problem. Additional link- information extensions for LNWC network are presented. By using the information, extensions of OSPF and RSVP-TE are proposed. In this draft, an optical link is used as a TE-link between neighbor OXCs or between neighbor OXC and a label switch router (LSR). We refer OXC or LSR to a node. Component links (or ports), each of which may corresponding to a wavelength, in one or multiple fiber(s) are bundled into a TE-link [LINK-BUNDLE], where every wavelength information is aggregated. Figure 1 shows an example of an optical network model. OXC is used to refer to all categories of optical cross-connects, irrespective of the internal switching fabric. The left side of OXC 1 has a 3R. The right side of OXC 1, both sides of OXC2, and LSR 2 have WDM functions. o-link 1 and o-link 2 are defined as a single TE-link that budles multiple componet links. LSR 1 ----- OXC 1 ====== OXC 2 ====== LSR 2 o-link 1 o-link 2 Oki [Page 2] draft-oki-ipo-optlink-req-00.txt February 2002 Figure 1: Example of optical network model 2. Requirements of optical link-state information in LNWC network Since wavelength is limitedly or not converted into another wavelength in LNWC network, information which wavelength is reserved in a TE-link is necessary for traffic engineering. Note that wavelengths in more than one fiber are not considered to be bundled into a TE-link in LNWC network, because the same wavelengths in more than one fiber should be differently handled for a purpose of traffic engineering. Wavelength status to indicate which wavelength is reserved/unreserved in a TE-link. The wavelength status is used to solve the RWA problem. However, opaque LSA sub-TLVs, which is defined in [OSPF-TE][GMPLS- OSPF], for a bundled TE-link between neighbor nodes do not express the wavelength status and not advertise it. Therefore, link- information extensions need to be added to achieve traffic engineering in LNWC network. 3. Label Definition for Corresponding Wavelength Value Wavelength value (e.g., 1550 nm) should be globally considered in LNWC network. For a purpose of the advertisement of wavelength status in a TE-link and signalling to set up an optical path, each wavelength value should be globally defined as a label in the LNWC network. There are several possible ways to assign a label to the corresponding wavelength value. One way to assign a label is to express the wavelength value itself (unit: nm) with 4 octets field in the IEEE floating point format. Another way is to use three types of integer parameters, which are wavebands (C, L, S), ITU grid spacing (e.g., 25, 50, and 100 GHz), and deviation from the reference center frequency of the corresponding waveband. 4. OSPF extensions To indicate the wavelength status in a TE-link between neighbor nodes, there are two possible ways as follows. 4. 1 Explicit label scheme Labels corresponding wavelengths with indication bits to express the wavelength status in a TE-link between neighbor nodes are explicitly advertised. If the status of a wavelength is changed, the corresponding label with the indication bit are updated and advertised. In the explicit label scheme, the information amount to Oki [Page 3] draft-oki-ipo-optlink-req-00.txt February 2002 advertise the wavelength status may be increased when the number of used labels are large. 4. 2 Bitmap scheme A set of labels that are used in LNWC network is advertised. Indication bits to express the wavelength status as a label set are advertised by using a bitmap format. In the bitmap format, the indication bits appear in an increasing order with label values. If a value of the indication bit is 1, the label is reserved. If a value of the indication bit is 0, the label is reserved. Every time the status for each wavelength is changed, label values themselves do not need to be advertised. Instead of that, only the indication bits with the bitmap format are advertised. When a set of the labels that are used in the LNWC network is updated, the updated set of the labels is advertised. 5. RSVP-TE extensions 5. 1 AND scheme When a path message attempts to set up an optical path at each source/transit OXC, it carries a set of unreserved labels that are unreserved through all the TE-links from the source OXC to the transit OXC. The label set is called an AND label set. If there is at least a reserved label in a TE-link from the source OXC to the transit OXC, the label is excluded in the transit node from the AND set. If there is no label in the AND set, the transit OXC should perform a wavelength conversion. Otherwise, the request of the optical path set-up is rejected. There are two possible ways to carry an AND label set of unreserved labels, the explicit label scheme and the bitmap scheme as described in Section 4. The explicit label scheme is considered in [GMPLS- RSVP] as 'label set'. 5. 2 ALL scheme When a path message attempts to set up an optical path at each source/transit node, it carries a set of unreserved labels for all TE-links on an optical path. The label set is called an ALL label set. A destination node receives the ALL label set and decides which labels should be used on the optical path. In the ALL scheme, the destination node has several options on which node should use a wavelength-conversion function if it is needed. There are two possible ways to carry a set of unreserved label, the explicit label scheme and the bitmap scheme in the same way as the Oki [Page 4] draft-oki-ipo-optlink-req-00.txt February 2002 AND scheme. Note that the ALL scheme carries each label set for all the TE-links on the optical path, while the AND scheme carries a label set for each optical path. 6. Requirements of optical link-state information in WC Network Since any wavelength can be converted into any wavelength at OXC, information which wavelength is reserved in a TE-link is not necessary. The number of wavelengths (NW) and the number of unreserved wavelengths (NUW) in a TE-link are used for traffic engineering. For example, a least-loaded path finding algorithm is employed to find an appropriate optical path. The optical-link information in a TE-link between two neighbor nodes is advertised. Therefore, multiple ports of OXC, each of which is corresponding to each wavelength may be combined into a TE-link. In OSPF extensions, opaque LSA sub-TLVs includes maximum reservable bandwidth and unreserved bandwidth, which sub-TLV types are 7 and 8, respectively. NW and NUW are expressed by using maximum reservable bandwidth and unreserved bandwidth for a bundled TE-link between neighbor nodes in the following. .nf NW = maximum reservable bandwidth for a bundled TE-link = sum of maximum reservable bandwidth of all component links and NUW = unreservable bandwidth for a bundled TE-link = sum of unreservable bandwidth of all component links. Note that NW is not the number of wavelength in a fiber, but is the number of ports, in other words, wavelengths, of OXC in a TE-link. However, the units of the maximum reservable bandwidth and unreservable bandwidth are defined as byte per second [GMPLS-OSPF]. Since the values of NUW and NW are independent of byte per second, the modification of the units or a sub-TLV definition is needed. 7. References [OSPF-TE] Katz, D., Yeung, D., "Traffic Engineering Extensions to OSPF", draft-katz-yeung-ospf-traffic-06.txt (work in progress) [GMPLS-OSPF] Kompella, K., Rekhter, Y., Banerjee, A. et al, "OSPF Extensions in Support of Generalized MPLS", draft-ietf-ccamp-ospf- gmpls-extensions-00.txt (work in progress) [GMPLS-SIG] "Generalized MPLS - Signaling Functional Description", draft-ietf-mpls-generalized-signaling-04.txt (work in progress) [GMPLS-RSVP] "Generalized MPLS Signaling - RSVP-TE Extensions", draft-ietf-mpls-generalized-rsvp-te-07.txt (work in progress) Oki [Page 5] draft-oki-ipo-optlink-req-00.txt February 2002 [GMPLS-ROUTING] "Routing Extensions in Support of Generalized MPLS", draft-ietf-ccamp-gmpls-routing-02.txt (work in progress) [LINK-BUNDLE] Kompella, K., Rekhter, Y., Berger, L., "Link Bundling in MPLS Traffic Engineering", draft-ietf-mpls-bundle-01.txt (work in progress) 8. Authors' Addresses Eiji Oki NTT Corporation 3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan Email: oki.eiji@lab.ntt.co.jp Nobuaki Matsuura NTT Corporation 3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan Email: matsuura.nobuaki@lab.ntt.co.jp Wataru Imajuku NTT Corporation 1-1 Hikari-no-oka, Yokosuka, Kanagawa, 239-0847 Japan Email: imajyuku@exa.onlab.ntt.co.jp Kohei Shiomoto NTT Corporation 3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan Email: shiomoto.kohei@lab.ntt.co.jp Naoaki Yamanaka NTT Corporation 3-9-11 Midori-cho, Musashino-shi, Tokyo 180-8585, Japan Email: yamanaka.naoaki@lab.ntt.co.jp Oki [Page 6]