Network Working Group Z. Li Internet-Draft K. Zhao Intended status: Standards Track Huawei Technologies Expires: April 24, 2014 October 21, 2013 IS-IS Extensions for MPLS Virtual Nodes and Virtual Links draft-li-isis-mpls-vnode-vlink-00 Abstract MPLS plays a key role in the process of implementing network virtualization. [I-D.li-mpls-network-virtualization-framework] proposes the framework to implement MPLS virtual network based on the architecture of central controller IGP. This document defines the corresponding IS-IS protocol extension and procedures to implement virtual nodes node and virtual link based on MPLS global label. 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 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 April 24, 2014. Copyright Notice Copyright (c) 2013 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 Li & Zhao Expires April 24, 2014 [Page 1] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 (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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Application for QoS-based Segment Routing . . . . . . . . 4 4. IS-IS Extensions . . . . . . . . . . . . . . . . . . . . . . 4 4.1. IPv4 MPLS Virtual Node Sub-TLV . . . . . . . . . . . . . 4 4.2. IPv6 MPLS Virtual Node Sub-TLV . . . . . . . . . . . . . 5 4.3. IPv4 MPLS Virtual Link Sub-TLV . . . . . . . . . . . . . 6 4.4. IPv6 MPLS Virtual Link Sub-TLV . . . . . . . . . . . . . 8 4.5. Attribute Sub-TLV . . . . . . . . . . . . . . . . . . . . 9 4.5.1. Bandwidth Attribute Sub-TLV . . . . . . . . . . . . . 9 4.6. Procedures . . . . . . . . . . . . . . . . . . . . . . . 10 4.6.1. Sending . . . . . . . . . . . . . . . . . . . . . . . 10 4.6.2. Receiving . . . . . . . . . . . . . . . . . . . . . . 10 5. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Normative References . . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction As the virtual network operators develop, it is desirable to provide better network virtualization solutions to facilitate the service provision. [I-D.li-mpls-network-virtualization-framework] proposes a new framework to implement MPLS virtual network based on the architecture of central controlled IGP. It is to allocate MPLS global label for the virtual network topologies, network nodes and links by an IGP controller to IGP clients. Thus MPLS global labels becomes the unique identifications in the underlying networks to compose the virtual networks. This document defines the corresponding IS-IS protocol extensions and procedures to implement virtual nodes and links based on MPLS global label. The other document [I-D.li-isis-mpls-multi-topology] defines the corresponding IS-IS protocol extensions and procedures to support MPLS Multi- Topology. Li & Zhao Expires April 24, 2014 [Page 2] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 2. Terminology Underlying Network: It is the network which the virtual network is built based on. The underlying network can be the physical network or the virtual network. MPLS Virtual Network: The virtual network is built based on the underlying network. It is composed by virtual nodes and virtual links which are identified by MPLS global label. In this document, the concept of virtual network is the same as that of MPLS virtual network. Underlying Link: It is the link in the underlying network which the virtual link is built based on. The underlying link can be physical link or the virtual link. MPLS Virtual Link: The virtual link is built based on the underlying link with specific attribute requirement. It can be identified by MPLS global label. In this document, the concept of virtual link is the same as that of MPLS virtual link. Underlying Node: It is the node in the underlying network which the virtual node is built based on. The underlying node can be physical node or the virtual node. MPLS Virtual Node: The virtual node is built based on the underlying node with specific attribute requirement. It can be identified by MPLS global label. In this document, the concept of virtual node is the same as that of MPLS virtual node. 3. Overview [I-D.li-rtgwg-cc-igp-arch] defines the central controlled architecture for IGP. In [I-D.li-mpls-network-virtualization-framework], a new framework is defined to implement MPLS virtual network based on central controlled IGP. In the framework, the virtual nodes can be identified by the global label allocated for the tuple {Multi-Topology ID, Underlying Node Identification, Attributes of the Virtualized Node}. Multi-topology ID is the identification of the corresponding multi-topology of the underlying network. The underlying node can be identified by the node's address (typically the loopback address) if the underlying node is the physical network node or it can be identified by another global label corresponding to the underlying virtual node. The label bindings for the virtual nodes are flooded from the IGP controller to the IGP clients. When IGP clients receives the label binding, it can Li & Zhao Expires April 24, 2014 [Page 3] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 install the MPLS forwarding entry to map the incoming label to the forwarding information related with the virtual node. In the framework, the virtual links can be identified by the global label allocated for the tuple {Multi-Topology ID, Underlying Link Identification, Attributes of the Virtualized Link}. Multi-topology ID is the identification of the corresponding multi-topology of the underlying network. The underlying link can be identified by the link ID or the link's address (typically the pair of the addresses of two end-points of the link) if the underlying link is the physical network link or it can be identified by another global label corresponding to the underlying virtual link. The label bindings for the virtual links are flooded from the IGP controller to the IGP clients. When IGP clients receives the label binding, it can install the MPLS forwarding entry to map the incoming label to the forwarding information related with the virtual link. 3.1. Application for QoS-based Segment Routing MPLS virtual links and nodes can be used for the segment routing defined in [I-D.filsfils-rtgwg-segment-routing]. The MPLS virtual node is just like the Node Segment in the Segment Routing. The MPLS virtual link is just like the Adjacency Segment in the Segment Routing. When the bandwidth attribute is applied to the MPLS virtual node or the MPLS virtual link, network nodes should reserve the bandwidth to provide QoS service of bandwidth guarantee for the virtual link or the virtual node. When this type of virtual links and the virtual nodes are grouped together to implement segment routing, the end-to-end QoS service are guaranteed in the underlying network. 4. IS-IS Extensions The IS-IS Label Mapping TLV is defined in [I-D.li-isis-mpls-multi-topology] which consists of pairs of Label sub-TLVs and FEC sub-TLVs. The Label Mapping TLV needs to be used to send label mapping for MPLS virtual nodes and links. In these TLV, the Label sub-TLV defined in [I-D.li-isis-mpls-multi-topology] contains the global label value for the virtual node or the virtual link. In this document new types of sub-TLVs are defined as the FEC for the MPLS virual node and the MPLS virtual link. 4.1. IPv4 MPLS Virtual Node Sub-TLV When implement virtual node, the global label is allocated for the tuple {Multi-Topology ID, Underlying Node Identification, Attributes of the Virtualized Node}. The IPv4 MPLS Virtual Node sub-TLV has following format: Li & Zhao Expires April 24, 2014 [Page 4] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Multi-Topology ID (32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Node Address (32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Attributes of Virtual Node (Variable) | . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: IPv4 MPLS Virtual Node Sub-TLV Format o Type: 1 octet of sub-TLV type. It is to be allocated by IANA. o Length: 1 octet of length of the value field of the sub-TLV. It is up to 252 octets. o Multi-Topology ID: 4 octets. It contains the ID of the underlying MPLS Multi-Topology based on which the virtual nodes are created. o Node Address: it is the 32-bit IPv4 address of the underlying node based on which the virtual nodes are created. o Attributes of Virtual Node: It contains attributes of the virtual node which length can be variable. In this type of Virtual Node Sub-TLV, the underlying node is identified by the node's IPv4 address (typically the loopback address) . For the virtual node which is built based on the underlying MPLS virtual node identified by a MPLS global label, the sub-TLV will be defined in a future version. 4.2. IPv6 MPLS Virtual Node Sub-TLV When implement virtual node, the global label is allocated for the tuple {Multi-Topology ID, Underlying Node Identification, Attributes of the Virtualized Node}. The IPv6 MPLS Virtual Node sub-TLV has following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Li & Zhao Expires April 24, 2014 [Page 5] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Multi-Topology ID (32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | IPv6 Node Address (128 bits) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Attributes of Virtual Node (Variable) | . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: IPv6 MPLS Virtual Node Sub-TLV Format o Type: 1 octet of sub-TLV type. It is to be allocated by IANA. o Length: 1 octet of length of the value field of the sub-TLV. It is up to 252 octets. o Multi-Topology ID: 4 octets. It contains the ID of the underlying MPLS Multi-Topology based on which the virtual nodes are created. o Node Address: it is the 128-bit IPv6 address of the underlying node based on which the virtual nodes are created. o Attributes of Virtual Node: It contains attributes of the virtual node which length can be variable. In this type of Virtual Node Sub-TLV, the underlying node is identified by the node's IPv6 address (typically the loopback address) . For the virtual node which is built based on the underlying MPLS virtual node identified by a MPLS global label, the sub-TLV will be defined in a future version. 4.3. IPv4 MPLS Virtual Link Sub-TLV When implement virtual link, the global label is allocated for the tuple {Multi-Topology ID, Underlying Link Identification, Attributes of the Virtualized Link}. The IPv4 Virtual Link sub-TLV has following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Li & Zhao Expires April 24, 2014 [Page 6] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 | Type | Length | Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Multi-Topology ID (32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Source End-Point Address (32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Destination End-Point Address (32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Attributes of Virtual Node (Variable) | . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: IPv4 MPLS Virtual Link Sub-TLV Format o Type: 1 octet of sub-TLV type. It is to be allocated by IANA. o Length: 1 octet of length of the value field of the sub-TLV. It is up to 252 octets. o Flags: 1 octet of flags of the virtual link. Now 1 bit is defined as "Bi-directional Bit". If the bit is set, it means the virtual link is bi-directional. If the bit is 0, it means the virtual link is uni-directional. o Multi-Topology ID: 4 octets. It contains the ID of the underlying MPLS Multi-Topology based on which the virtual links are created. o Source End-Point Address: it is the 32-bit IPv4 address of the source end-point of the underlying link based on which the virtual links are created. o Destination End-Point Address: it is the 32-bit IPv4 address of the destination end-point of the underlying link based on which the virtual links are created. o Attributes of Virtual Node: It contains attributes of the virtual node which length can be variable. In this type of Virtual Link Sub-TLV, the underlying link is identified by the link's IPv4 address (typically the pair of the IPv4 addresses of two end-points of the link) . For the virtual link which is built based on the underlying MPLS virtual node identified by a MPLS global label or the virtual link which is built based on the underlying link identified by Link ID, the sub-TLV will be defined in a future version. Li & Zhao Expires April 24, 2014 [Page 7] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 4.4. IPv6 MPLS Virtual Link Sub-TLV When implement virtual link, the global label is allocated for the tuple {Multi-Topology ID, Underlying Link Identification, Attributes of the Virtualized Link}. The IPv6 Virtual Link sub-TLV has following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Multi-Topology ID (32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | IPv6 Source End-Point Address (32 bits) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | IPv6 Destination End-Point Address (32 bits) | | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Attributes of Virtual Node (Variable) | . . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: IPv6 MPLS Virtual Link Sub-TLV Format o Type: 1 octet of sub-TLV type. It is to be allocated by IANA. o Length: 1 octet of length of the value field of the sub-TLV. It is up to 252 octets. o Flags: 1 octet of flags of the virtual link. Now 1 bit is defined as "Bi-directional Bit". If the bit is set, it means the virtual link is bi-directional. If the bit is 0, it means the virtual link is uni-directional. o Multi-Topology ID: 4 octets. It contains the ID of the underlying MPLS Multi-Topology based on which the virtual links are created. Li & Zhao Expires April 24, 2014 [Page 8] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 o Source End-Point Address: it is the 128-bit IPv6 address of the source end-point of the underlying link based on which the virtual links are created. o Destination End-Point Address: it is the 128-bit IPv6 address of the destination end-point of the underlying link based on which the virtual links are created. o Attributes of Virtual Node: It contains attributes of the virtual node which length can be variable. In this type of Virtual Link Sub-TLV, the underlying link is identified by the link's IPv6 address (typically the pair of the IPv6 addresses of two end-points of the link) . For the virtual link which is built based on the underlying MPLS virtual node identified by a MPLS global label or the virtual link which is built based on the underlying link identified by Link ID, the sub-TLV will be defined in a future version. 4.5. Attribute Sub-TLV When build MPLS virtual node or virtual link, attributes are necessary. The attribute sub-TLV has following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | . Attribute Value . . . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Attribute Sub-TLV Format 4.5.1. Bandwidth Attribute Sub-TLV The Bandwidth Attribute Sub-TLV has following format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Class-Type | Li & Zhao Expires April 24, 2014 [Page 9] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bandwidth (32-bit IEEE floating point number) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Bandwidth Attribute Sub-TLV Format o Type: 1 octet of sub-TLV type. It is to be allocated by IANA. o Length: 1 octet of length of the value field of the sub-TLV. It is 5. o Class-Type: 1 octet. Indicates the Class-Type of the bandwidth. Values currently allowed are 0, 1, 2, ... , 7. o Bandwidth: 32 bits IEEE floating point number. Indicates the number of bytes (not bits) per second that need to be reserved for the MPLS virtual link. 4.6. Procedures 4.6.1. Sending When the IGP controller needs to implement the MPLS virtual node, the IGP controller MUST originate a new LSP comprising the Label Mapping TLV for the MPLS virtual node. The Label Mapping TLV MUST contains one or more pairs of the Global Label sub-TLV and the Virtual Node sub-TLV. If the length of these sub-TLVs can exceeds 252 octets, there SHOULD be Multiple Label Mapping TLV in IS-IS LSP. When the IGP controller needs to implement the MPLS virtual link, the IGP controller MUST originate a new LSP comprising the Label Mapping TLV for the MPLS virtual link. The Label Mapping TLV MUST contains one or more pairs of the Global Label sub-TLV and the Virtual Link sub-TLV. If the length of these sub-TLVs can exceeds 252 octets, there SHOULD be Multiple Label Mapping TLV in IS-IS LSP. If the bandwidth needs to be reserved on the underlying link for the virtual link, the Bandwidth Attribute sub-TLV MUST be included in the MPLS Virtual Link sub-TLV to indicate the class-type and the bandwidth to be reserved. 4.6.2. Receiving When receiving the Label Mapping to implement the MPLS virtual node, the IGP clients SHOULD install MPLS forwarding entry to map the incoming label to the forwarding information related with the virtual node. Li & Zhao Expires April 24, 2014 [Page 10] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 When receiving the Label Mapping to implement the MPLS virtual link, the IGP clients SHOULD install MPLS forwarding entry to map the incoming label to the forwarding information related with the virtual link. If Bandwidth Attribute sub-TLV is included in the MPLS Virtual Link sub-TLV, the bandwidth of the class-type specified in the sub- TLV MUST be reserved accordingly. 5. Compatibility Routers that do not support these MPLS Virtualization extensions SHOULD silently ignore the TLV and the sub-TLVs defined in this document. 6. IANA Considerations This document request to allocate a type value for the IPv4 MPLS Virtual Node sub-TLV, a type value for the IPv6 MPLS Virtual Node sub-TLV, a type value for the IPv4 MPLS Virtual Link sub-TLV, a type value for the IPv6 MPLS Virtual Link sub-TLV and a type value for the Bandwidth Attribute sub-TLV. 7. Security Considerations TBD. 8. References 8.1. Normative References [I-D.li-mpls-global-label-framework] Li, Z., Zhao, Q., and T. Yang, "A Framework of MPLS Global Label", draft-li-mpls-global-label-framework-00 (work in progress), July 2013. [I-D.li-mpls-network-virtualization-framework] Li, Z. and M. Li, "Framework of Network Virtualization Based on MPLS Global Label", draft-li-mpls-network- virtualization-framework-00 (work in progress), October 2013. [I-D.li-rtgwg-cc-igp-arch] Li, Z., Chen, H., and G. Yan, "An Architecture of Central Controlled Interior Gateway Protocol (IGP)", draft-li- rtgwg-cc-igp-arch-00 (work in progress), October 2013. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. Li & Zhao Expires April 24, 2014 [Page 11] Internet-Draft IS-IS Extensions for MPLS VLink and VNode October 2013 8.2. Informative References [I-D.filsfils-rtgwg-segment-routing] Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, "Segment Routing Architecture", draft-filsfils-rtgwg- segment-routing-00 (work in progress), June 2013. [I-D.gredler-isis-label-advertisement] Gredler, H., Amante, S., Scholl, T., and L. Jalil, "Advertising MPLS labels in IS-IS", draft-gredler-isis- label-advertisement-03 (work in progress), May 2013. [I-D.li-isis-mpls-multi-topology] Li, Z. and Q. Zhao, "IS-IS Extensions for MPLS Multi- Topology", draft-li-isis-mpls-multi-topology-00 (work in progress), October 2013. [I-D.previdi-isis-segment-routing-extensions] Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., and S. Litkowski, "IS-IS Extensions for Segment Routing", draft-previdi-isis-segment-routing-extensions-02 (work in progress), July 2013. Authors' Addresses Zhenbin Li Huawei Technologies Huawei Bld., No.156 Beiqing Rd. Beijing 100095 China Email: lizhenbin@huawei.com Katherine Zhao Huawei Technologies 2330 Central Expressway Santa Clara, CA 95050 USA Email: katherine.zhao@huawei.com Li & Zhao Expires April 24, 2014 [Page 12]