Network Working Group L. Yong Internet-Draft D. Cheng Intended status: Standards Track W. Hao Expires: September 10, 2015 D. Eastlake Huawei Technologies Ltd. A. Qu MediaTek J. Hudson Brocade U. Chunduri Ericsson Inc. March 9, 2015 IGP Multicast Architecture draft-yong-pim-igp-multicast-arch-01 Abstract This document specifies the architecture of IP multicast routing using an Interior Gateway Protocol (IGP). 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 [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 September 10, 2015. Yong, et al. Expires September 10, 2015 [Page 1] Internet-Draft IGP Multicast Architecture March 2015 Copyright Notice Copyright (c) 2015 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3 1.3. Conventions used in this Document . . . . . . . . . . . . 4 1.4. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. An Overview of IGP . . . . . . . . . . . . . . . . . . . . . 5 3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Routing IP Multicast Packets . . . . . . . . . . . . . . . . 6 4.1. Multicast Distribution Tree . . . . . . . . . . . . . . . 7 4.1.1. Bidirectional Distribution Tree . . . . . . . . . . . 8 4.2. Advertising Multicast Group Membership . . . . . . . . . 9 4.3. Requirements of Edge Routers . . . . . . . . . . . . . . 9 4.4. Intra-Area Multicast Routing . . . . . . . . . . . . . . 10 4.5. Inter-Area Multicast Routing . . . . . . . . . . . . . . 10 4.5.1. Behavior of IS-IS Level 2 Router . . . . . . . . . . 11 4.5.2. Behavior of OSPF ABR . . . . . . . . . . . . . . . . 11 4.6. Heterogeneous Environment . . . . . . . . . . . . . . . . 11 4.7. TE (Traffic Engineering) Support . . . . . . . . . . . . 12 4.8. Applications to Overlay Model . . . . . . . . . . . . . . 12 4.9. IPv6 and IPv4 . . . . . . . . . . . . . . . . . . . . . . 12 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 6. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 13 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.1. Normative References . . . . . . . . . . . . . . . . . . 13 7.2. Informative References . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14 Yong, et al. Expires September 10, 2015 [Page 2] Internet-Draft IGP Multicast Architecture March 2015 1. Introduction 1.1. Overview In an IP network, an IGP is used to route and forward IP unicast packets. In doing so, the routers collect and maintain the network information and store it in their database. The network information includes the identity of the routers and their interconnections. In a traffic engineering enabled network, the information also includes traffic related parameters such as link bandwidth. The network information that is already maintained on routers, along with some minor IGP protocol extensions as proposed in this document, are sufficient to also route IP multicast packets. This means a single IGP can be used for routing both unicast packets and multicast packets. This document describes the architecture of routing IP multicast packets using the network information that is disseminated by an IGP. 1.2. Motivation With the explosion of IP technology based applications, the support of IP multicast delivery over the same IP network that carries IP unicast traffic becomes mandatory. In many aspects, some basic requirements for routing IP multicast packets are the same as those for routing IP unicast packets; e.g., the "plug and play" nature of bringing up the routing engine and enabling the packets forwarding. It is desirable to use an IGP that requires minimum configuration and currently only routes and forwards IP unicast packets, to also route and forward IP multicast packets. Current practice in an IP network is to use a separate protocol, such as Protocol Independent Multicast (PIM - [RFC4601]), to route and forward IP multicast packets, whereby some network information are actually retrieved from IGP. Using a single protocol, i.e., an IGP, to route both IP unicast and multicast packets is more efficient; this eliminates additional convergence time that would otherwise be introduced by the second protocol. Using one protocol also reduces operational complexity. In an advanced data center network, the decoupling of network IP space from service IP space, for example a VxLAN based network overlay [RFC7348], is required. To support all service applications, such an IP network fabric must support both unicast and multicast. Decoupling network IP space from service IP address space also provides network agility and programmability. If network IP space is decoupled from service IP space, the network itself no longer needs manual configuration; an IP network fabric can be formed automatically. Yong, et al. Expires September 10, 2015 [Page 3] Internet-Draft IGP Multicast Architecture March 2015 1.3. 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 [RFC2119]. 1.4. Terminology This document makes use of the following terms: o Edge Router: A router that has direct interfaces with one or more IP hosts. o Distribution Tree: a rooted distribution tree with one root and one or more leaves that facilitate routing multicast packets. o IGP: Interior Gateway Protocol. o Intra-Area: Refers to the communication between IGP routing nodes within a single IGP's area. o Inter-Area: Refer to the communication between IGP routing nodes across an area boundary. o IP Multicast Group o Link State Database: The database constructed and maintained by a router running link state based routing algorithm such as IS-IS and OSPF. It contains network based information including identity of routers and their interconnections, reachable IP addresses, etc. o Local Group Database: The database constructed and maintained by an edge router that stores and maintains entries of { multicast- address, host } pairs for hosts interested in traffic for a multi- cast address. o Pruned Tree: A subset of IGP's topology graph with a tree root, using which multicast packets are forwarded to one or more destination nodes with optimization of the usage of links and nodes. o Root Node: A router serving as the root of a multicast distribution tree. o TE (Traffic Engineering) Database: The database constructed and maintained by a router running a link state based routing algorithm with TE extensions such as ISIS-TE and OSPF-TE. It Yong, et al. Expires September 10, 2015 [Page 4] Internet-Draft IGP Multicast Architecture March 2015 contains TE parameters (such as bandwidth) that are associated with links and nodes. o Transit Router: A router that is capable of receiving an IP multicast packet, then replicates it and sends to one or more other routers in the same multicast distribution tree. 2. An Overview of IGP There are currently two heavily deployed IGPs, IS-IS [RFC1195]/[RFC5308] and OSPF [RFC2328]/[RFC2740]. IS-IS and OSPF are different in many aspects, but they both use a link-state algorithm and the network information they disseminate for the same IP network is the same, including routers' IP addresses, routers' interconnections, reachable IP addresses, the network topology, etc. An IGP operation can have a hierarchy of two levels. An IGP runs within an area, where each participating router originates and advertises its own information (router's identity, interface IP addresses, identity of directly connected neighbors, etc.), and this information is flooded to all participating routers the entire area but not beyond. As a result, within an IGP area, each participating router maintains the information of all routers and their interconnections. This collection of network information is the Link State Database, which is currently used as a base to calculate IP routing table for unicast packets within an IGP area. Sometimes we refer to the topology within an IGP area as a topology graph. Separate IGP areas may be interconnected and, between areas, only reachability information is advertised across area boundaries by Level-2 routers in IS-IS or Area Border Routers (ABR) in OSPF. [RFC1195] specifies an IGP for routing IPv4 unicast packets using IS- IS protocol (ISO), whereas [RFC5308] specifies the extensions to support routing IPv6 unicast packets. OSPFv2 [RFC2328] is an IGP for routing IPv4 unicast packets whereas OSPFv3 [RFC2740] is an IGP for routing IPv6 unicast packets. The link state based routing algorithm in OSPF and IS-IS calculates the shortest path from the source to the destination. A routing table for routing unicast packets is generated on every participating IGP router. For some applications, path restrictions (e.g., link bandwidth) need to be considered. As a result, extensions have been added to both IS-IS and OSPF to support traffic engineering based unicast routing as follows: Yong, et al. Expires September 10, 2015 [Page 5] Internet-Draft IGP Multicast Architecture March 2015 o [RFC3630] - Traffic Engineering (TE) Extensions to OSPF Version 2 o [RFC3784] - Intermediate System to Intermediate System (IS-IS) Extensions for Traffic Engineering (TE) o [RFC5329] - Traffic Engineering Extensions to OSPF Version 3 A TE-capable IGP router, in addition to constructing a Link State Database, also constructs and maintains a TE Database that stores the traffic parameters (e.g., bandwidth) associated with links and nodes. This information is used for constraint based consideration during normal shortest path calculation. 3. Scope To support IP multicast routing, either IS-IS or OSPF can be used and, in the architectural perspective of this document, there is no difference between them. It requires no change in IS-IS or OSPF other than extensions to advertise and store distribution tree root node address and multicast group receiver information (refer to Section 4.2). Using IGP to route IP multicast packets is within IGP's architecture and routing paradigm. IP multicast routing within an IGP area is called intra-area multicast routing, and IP multicast routing across IGP area is called inter-area multicast routing. The concept, rules and behavior regarding intra-area unicast routing and inter-area unicast routing are all similarly applicable to intra-area and inter- area multicast routing, respectively. In an IPv4 network, IPv4 multicast packets can be routed using IS-IS (based on [RFC1195]) or OSPFv2 as introduced by this document. Similarly in an IPv6 network, IPv6 multicast packets can be routed using IS-IS (based on [RFC5308]) or OSPFv3 [RFC2740]. As the networking industry is currently under transition from IPv4 to IPv6, co-existence of the two is sometimes required. Using the architecture described in this document, IPv4 multicast packets can be transported over an IPv6 network and IPv6 multicast packets can be transported over an IPv4 network. 4. Routing IP Multicast Packets As illustrated in Figure 1, a single IGP can support both IP unicast and multicast routing. This section describes routing IP multicast packets using the existing network information that IGP collects, the related functions Yong, et al. Expires September 10, 2015 [Page 6] Internet-Draft IGP Multicast Architecture March 2015 and characteristics, along with the required extensions to existing IGPs. +-------------+ +-------------+ | IP Unicast | | IP Multicast| | Routing | | Routing | +------^------+ +------^------+ | | +------o------+ +------o------+ | Unicast | | Multicast | |Routing Table| |Routing Table| +------^------+ +------^------+ | | +------o------+ +------o------+ | Shortest | | Distribution| | Path Tree | | Path Tree | +------^------+ +------^------+ | | +------o---------------o------+ | Link State Database | +--------------^--------------+ | +--------------o--------------+ | IGP | | +---------+ +---------+ | | | OSPF | | IS-IS | | | +---------+ +---------+ | +-----------------------------+ Figure 1: Using an IGP to Route both IP Unicast and Multicast Packets 4.1. Multicast Distribution Tree To route IP multicast packets, a distribution tree is used. A distribution tree consists of a tree root, one or more tree leaves, and some branch nodes. The tree root is identified by the IP address (or Router ID) of an arbitrary router. The tree root can be configured for a specific IP multicast address group, or automatically elected via an algorithm. A tree leaf is an edge router and is a multicast destination. A tree leaf is identified by an edge router's IP address and it is directly attached to one or more hosts that advertise the IP multicast group addresses (see Section 4.2 for details). A router that is not a tree root but transmits a received IP multicast packet to one or more other router is called a Transit Router, which is a branch node in the distribution tree. Yong, et al. Expires September 10, 2015 [Page 7] Internet-Draft IGP Multicast Architecture March 2015 In the most general case, there is a single multicast distribution tree for each IP multicast address group. Once a distribution tree is formed, an IP packet with the multicast destination address is forwarded according to the multicast distribution tree, that is, from the source to all tree leaves. Via configuration, additional distribution trees can be constructed for the same IP multicast address group, however with different tree roots and tree branches (paths). This option provides a redundancy for routing path protection, and it can also be used to support load balance. When a leaf node of a multicast distribution tree is in the same IGP area as the tree root, the packet flow in the tree is within a single IGP area. This behavior is called IGP intra-area multicast routing. When a leaf node of a multicast distribution tree is in a different IGP area from the tree root, the packet flow in the tree must cross IGP area boundary. This behavior is called IGP inter-area multicast routing. Unicast routing in an IGP domain requires minimum configuration. This characteristic is inherited by multicast routing, that is, it requires minimal configuration and a multicast distribution tree can generally be constructed quickly in the same manner as a unicast routing table. 4.1.1. Bidirectional Distribution Tree A multicast distribution tree is bi-directional. In such a tree, IP multicast packets destined to a given multicast address could traverse any tree branch in either direction; that means any leaf node on the tree can be a multicast receiver and sender. When a leaf node is a multicast source, it transmits the packet on the tree by which it is distributed to all other leaves of that tree. The bi- directionality of distribution tree is useful for applications such as video conference. By configuration, a multicast distribution tree can be uni- directional, i.e., all leaf nodes can only receive multicast packets destined to a given multicast address. In this scenario, the tree root may be the traffic source and if not, the source must unicast packets to the tree root, which then distributes the packets according to the distribution tree. The uni-directionality of distribution tree is useful for applications such as video broadcasting. Yong, et al. Expires September 10, 2015 [Page 8] Internet-Draft IGP Multicast Architecture March 2015 For optimization purpose, i.e., to build an efficient pruned multicast distribution tree in both cases, care must be taken in choosing the location of tree root in a given network; e.g., to consider the average path length from the root to leaf nodes, the total links (branches) used for the distribution, etc. 4.2. Advertising Multicast Group Membership In order to support multicast routing, an IGP must be extended to store and advertise IP multicast addresses in the similar manner currently for IP unicast addresses. Pairs of { multicast-group, host } can be configured on an edge router, or learned from the interaction with IGMP/MLD(see Section 4.3). In either case, the router must advertise the IP multicast group membership throughout the IGP area. The advertising, refresh, aging, and removal of IP multicast addresses are handled in the same manner as the existing database element, i.e., LSP in IS-IS and LSA in OSPF. IP multicast addresses can also be advertised across an IGP area boundary using mechanisms similar to those used for IP unicast addresses. IP multicast addresses may be summarized in a way similar to IP unicast addresses for scaling purpose. The details of storing and advertising IP multicast address using IS- IS and OSPF will be specified in a separate documents. 4.3. Requirements of Edge Routers To support routing IP multicast packets, edge routers, i.e., routers that have interfaces directly connected to IP hosts, are required to run IGMP (IGMPv2/[RFC2236] or IGMPv3/[RFC3376]) for IPv4 based hosts and MLD (MLD/[RFC2710] or MLDv2/[RFC3810]) for IPv6 based hosts. As the result of interaction with hosts, an edge router would build a Local Group Database where each entry is a { multicast-group, host } pair, which indicates that the attached host belonging to the IP multicast group. This process is on-going in order to keep track of the IP group membership addresses of attached hosts according to protocol specification of IGMP/MLD. Use of the Local Group Database is two fold. First, when an edge router receives an inbound IP multicast packet, it checks in the database to see if any entry has an IP multicast-group address matching the destination address in the received packet. If so, the packet is forwarded to the local host(s); otherwise the packet is Yong, et al. Expires September 10, 2015 [Page 9] Internet-Draft IGP Multicast Architecture March 2015 dropped. Note this behavior already exists on edge routers that support IP multicast forwarding. Second, an edge router is required to advertise/flood the IP multicast addresses learnt/withdrawn from IGMP/MLD to/from other routers in the same IGP area, in the similar manner as advertising/ flooding its own interface IP addresses. With this information, an IP multicast distribution tree can be built for each IP multicast address group. The details for advertising multicast addresses by IS-IS and OSPF will be documented separately. In some deployment, a host as a multicast destination or source may connect to more than one edge routers for the purpose of reliability or/and load balance, which is normally termed multi-homing. In this scenario, care must be taken in order to prevent forwarding loops or packets duplication. 4.4. Intra-Area Multicast Routing An IP multicast distribution tree within an IGP area is a sub-graph of the IGP's area topology graph (see Section 2). All routers that receive advertisement of IP multicast addresses in the IGP area must build the multicast distribution tree for each IP multicast address group. The construction of the distribution is based on the IGP's Link State Database, which is currently used for routing IP unicast packets. All routers in an IGP area must calculate and construct the intra-area distribution tree using IGP's Link State Database with the same algorithm, so that a pruned tree can be constructed for the distribution tree. Care must be taken to avoid forwarding loops and routing optimization is highly desirable. The algorithm for constructing an IP multicast distribution tree, and other related functions, do not require changes to existing IGP function other than the addition of extensions. The specific algorithm and related details for intra-area multicast routing will be in a separate document. 4.5. Inter-Area Multicast Routing In inter-area unicast routing, an IP packet from one IGP area forwarded to another area is sent to an area border node (ABR for OSPF) or L2 router (for IS-IS) first, which then forwards the packet to/in the neighboring area. This is also the scenario for inter-area multicast routing, and as such, an ABR/L2-Router functions as a Transit Router, or a branch node in the multicast distribution tree. Yong, et al. Expires September 10, 2015 [Page 10] Internet-Draft IGP Multicast Architecture March 2015 Note that IGP's Link State Database is per area, so the multicast distribution tree constructed on routers in the transmitting area in generally terminated at the ABR/L2-Router due to lack of routing information. The ABR/L2-Router in question would require extending the distribution in the receiving area based on the separate Link State Database. The specific procedure and related details for inter-area multicast routing will be in a separate document. 4.5.1. Behavior of IS-IS Level 2 Router For IS-IS, the area boundary is in the border router, which extends the distribution tree for that area. To support inter-area multicast routing, an IS-IS Level 2 Router is required to propagate IP multicast addresses received in one area to all Level 2 Routers in other areas it is connected. This behavior is similar to the advertisement of IS-IS Reachability Information PDU. 4.5.2. Behavior of OSPF ABR For OSPF, the area boundary is on the ABR. When an ABR attached to both transmitting area and receiving area, it extends the distribution tree in the receiving area. To support inter-area multicast routing, an OSPF ABR is required to propagate IP multicast addresses received in one area to all other areas to which it is attached. This behavior is similar to the advertisement of OSPF Summary LSAs. 4.6. Heterogeneous Environment To deploy IP multicast routing using IGP as described in this document, all routers in the IGP area are required to do the following: o Implement the extensions to IS-IS (documented separately) or to OSPF (documented separately), depending on the IGP in use, for advertising multicast addresses. o Support the new functions as described in Section 4. A heterogeneous network environment is one where not all routers in an IGP area implement the above extensions. A multicast distribution tree within such an area cannot be segregated, but tunneling mechanism can be used to support multicast routing there. When there are routers that would be on a multicast distribution tree but do not Yong, et al. Expires September 10, 2015 [Page 11] Internet-Draft IGP Multicast Architecture March 2015 supporting the required extensions, a tunnel is constructed connecting two routers capable of routing multicast across one or more intervening non-capable routers, such that the tunnel becomes a single branch on the distribution tree. An IP multicast packet sent from a tunnel end to the other is encapsulated in an IP packet with the sending router's IP address as the source address and the receiving router's IP address as the destination address. 4.7. TE (Traffic Engineering) Support The existing IP multicast routing practice (e.g., PIM) does not consider route constraints (e.g., link bandwidth). Both OSPF and IS- IS support traffic engineering based unicast routing by constructing and maintaining a TE Database. Like the Link State Database, the TE Database can also be used to support IP multicast routing when one or more path constraints are considered. To perform TE based multicast routing using IGP, routers must support TE extensions, and otherwise, there requires no other change in the IGP. 4.8. Applications to Overlay Model Using a single IGP as a uniform routing engine for both IP unicast and multicast routing enables a simple but efficient IP networking fabric that can serve various applications above it using a overlay model. These applications are viewed as at the service level, completely decoupled from the underneath IP networking fabric; however, they enjoy both IP unicast and multicast transportation infrastructure. In the multicast perspective, the applications can be IP based, but can also be layer-2 based such as Ethernet. 4.9. IPv6 and IPv4 The architecture as outlined in this document supports IPv4 multicast routing in IPv4 networks, and also IPv6 multicast routing in IPv6 networks. With mechanisms such as tunneling or address translation, the same architecture can also support IPv4 multicast routing in IPv6 networks, and IPv6 multicast routing in IPv4 networks. The details are specified in other documents. 5. IANA Considerations This document requires no IANA actions. Yong, et al. Expires September 10, 2015 [Page 12] Internet-Draft IGP Multicast Architecture March 2015 6. Acknowledgement 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 7.2. Informative References [RFC1195] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and dual environments", RFC 1195, December 1990. [RFC2236] Fenner, W., "Internet Group Management Protocol, Version 2", RFC 2236, November 1997. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener Discovery (MLD) for IPv6", RFC 2710, October 1999. [RFC2740] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", RFC 2740, December 1999. [RFC3376] Cain, B., Deering, S., Kouvelas, I., Fenner, B., and A. Thyagarajan, "Internet Group Management Protocol, Version 3", RFC 3376, October 2002. [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003. [RFC3784] Smit, H. and T. Li, "Intermediate System to Intermediate System (IS-IS) Extensions for Traffic Engineering (TE)", RFC 3784, June 2004. [RFC3810] Vida, R. and L. Costa, "Multicast Listener Discovery Version 2 (MLDv2) for IPv6", RFC 3810, June 2004. [RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", RFC 4601, August 2006. [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, October 2008. Yong, et al. Expires September 10, 2015 [Page 13] Internet-Draft IGP Multicast Architecture March 2015 [RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, "Traffic Engineering Extensions to OSPF Version 3", RFC 5329, September 2008. [RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger, L., Sridhar, T., Bursell, M., and C. Wright, "Virtual eXtensible Local Area Network (VXLAN): A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks", RFC 7348, August 2014. Authors' Addresses Lucy Yong Huawei Technologies Ltd. Austin, TX USA Email: lucy.yong@huawei.com Dean Cheng Huawei Technologies Ltd. 2330 Central Expressway Santa Clara, CA 95135 USA Email: dean.cheng@huawei.com Weiguo Hao Huawei Technologies Ltd. 101 Software Avenue Nanjing 210012 China Email: haoweiguo@huawei.com Donald Eastlake Huawei Technologies Ltd. 155 Beaver Street Milford, MA 01757 USA Email: d3e3e3@gmail.com Yong, et al. Expires September 10, 2015 [Page 14] Internet-Draft IGP Multicast Architecture March 2015 Andrew Qu MediaTek San Jose, CA 95134 USA Email: laodulaodu@gmail.com Jon Hudson Brocade 130 Holger Way San Jose, California 95134 USA Email: jon.hudson@gmail.com Uma Chunduri Ericsson Inc. 300 Holger Way San Jose, California 95134 USA Email: uma.chunduri@ericsson.com Yong, et al. Expires September 10, 2015 [Page 15]