VXLAN DCI Using EVPN
Author(s): Samer Salam, John Drake, Samir Thoria, Dennis Cai, Sami Boutros, Ali Sajassi
This document describes how Ethernet VPN (EVPN) technology can be used to interconnect VXLAN or NVGRE networks over an MPLS/IP network. This is to provide intra-subnet connectivity at Layer 2 and control- plane separation among the interconnected VXLAN...
Network Working Group Sami Boutros INTERNET-DRAFT Ali Sajassi Category: Standards Track Samer Salam Dennis Cai Samir Thoria Cisco John Drake Juniper Expires: January 16, 2014 July 16, 2013 VXLAN DCI Using EVPN draft-boutros-l2vpn-vxlan-evpn-02.txt Abstract This document describes how Ethernet VPN (EVPN) technology can be used to interconnect VXLAN or NVGRE networks over an MPLS/IP network. This is to provide intra-subnet connectivity at Layer 2 and control- plane separation among the interconnected VXLAN or NVGRE networks. The scope of the learning of host MAC addresses in VXLAN or NVGRE network is limited to data plane learning in this document. 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. 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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Boutros Expires January 16, 2014 [Page 1] INTERNET DRAFT VXLAN-EVPN July 16, 2013 Copyright and License 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 (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 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Control Plane Separation among VXLAN/NVGRE Networks . . . . 3 2.2 All-Active Multi-homing . . . . . . . . . . . . . . . . . . 4 2.3 Layer 2 Extension of VNIs/VSIDs over the MPLS/IP Network . . 4 2.4 Support for Integrated Routing and Bridging (IRB) . . . . . 4 3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Redundancy and All-Active Multi-homing . . . . . . . . . . 5 4. EVPN Routes . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1. BGP MAC Advertisement Route . . . . . . . . . . . . . . . 6 4.2. Ethernet Auto-Discovery Route . . . . . . . . . . . . . . 7 4.3. Per VPN Route Targets . . . . . . . . . . . . . . . . . . 7 4.4 Inclusive Multicast Route . . . . . . . . . . . . . . . . . 7 4.5. Unicast Forwarding . . . . . . . . . . . . . . . . . . . . 7 4.6. Handling Multicast . . . . . . . . . . . . . . . . . . . . 8 4.6.2. Multicast Stitching with Per-VNI Load Balancing . . . . 9 5. NVGRE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 9.1 Normative References . . . . . . . . . . . . . . . . . . . 10 9.2 Informative References . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Boutros Expires January 16, 2014 [Page 2] INTERNET DRAFT VXLAN-EVPN July 16, 2013 1 Introduction [EVPN] introduces a solution for multipoint L2VPN services, with advanced multi-homing capabilities, using BGP control plane over the core MPLS/IP network. [VXLAN] defines a tunneling scheme to overlay Layer 2 networks on top of Layer 3 networks. [VXLAN] allows for optimal forwarding of Ethernet frames with support for multipathing of unicast and multicast traffic. VXLAN uses UDP/IP encapsulation for tunneling. In this document, we discuss how Ethernet VPN (EVPN) technology can be used to interconnect VXLAN or NVGRE networks over an MPLS/IP network. This is achieved by terminating the VxLAN tunnel at the the hand-off points, performing data plane MAC learning of customer traffic and providing intra-subnet connectivity for the customers at Layer 2 across the MPLS/IP core. The solution maintains control-plane separation among the interconnected VXLAN or NVGRE networks. The scope of the learning of host MAC addresses in VXLAN or NVGRE network is limited to data plane learning in this document. The distribution of MAC addresses in control plane using BGP in VXLAN or NVGRE network is outside of the scope of this document and it is covered in [EVPN- OVERLY]. 1.1 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 RFC 2119 [RFC 2119]. LDP: Label Distribution Protocol MAC: Media Access Control MPLS: Multi Protocol Label Switching NVO: Network Virtualization Overlay NVE: NVO Endpoint OAM: Operations, Administration and Maintenance PE: Provide Edge Node PW: PseudoWire TLV: Type, Length, and Value VPLS: Virtual Private LAN Services VXLAN: Virtual eXtensible Local Area Network VTEP: VXLAN Tunnel End Point VNI: VXLAN Network Identifier (or VXLAN Segment ID) ToR: Top of Rack switch 2. Requirements 2.1. Control Plane Separation among VXLAN/NVGRE Networks Boutros Expires January 16, 2014 [Page 3] INTERNET DRAFT VXLAN-EVPN July 16, 2013 It is required to maintain control-plane separation for the underlay networks (e.g., among the various VXLAN/NVGRE networks) being interconnected over the MPLS/IP network. This ensures the following characteristics: - scalability of the IGP control plane in large deployments and fault domain localization, where link or node failures in one site do not trigger re-convergence in remote sites. - scalability of multicast trees as the number of interconnected networks scales. 2.2 All-Active Multi-homing It is important to allow for all-active multi-homing of the VXLAN/NVGRE network to MPLS/IP network where traffic from a VTEP can arrive at any of the PEs and can be forwarded accordingly over the MPLS/IP network. Furthermore, traffic destined to a VTEP can be received over the MPLS/IP network at any of the PEs connected to the VXLAN/NVGRE network and be forwarded accordingly. The solution MUST support all-active multi-homing to an VXLAN/NVGRE network. 2.3 Layer 2 Extension of VNIs/VSIDs over the MPLS/IP Network It is required to extend the VXLAN VNIs or NVGRE VSIDs over the MPLS/IP network to provide intra-subnet connectivity between the hosts (e.g. VMs) at Layer 2. 2.4 Support for Integrated Routing and Bridging (IRB) The data center WAN edge node is required to support integrated routing and bridging in order to accommodate both inter-subnet routing and intra-subnet bridging for a given VNI/VSID. For example, inter-subnet switching is required when a remote host connected to an enterprise IP-VPN site wants to access an application resided on a VM. 3. Solution Overview Every VXLAN/NVGRE network, which is connected to the MPLS/IP core, runs an independent instance of the IGP control-plane. Each PE participates in the IGP control plane instance of its VXLAN/NVGRE network. Each PE node terminates the VXLAN or NVGRE data-plane encapsulation where each VNI or VSID is mapped to a bridge-domain. The PE performs data plane MAC learning on the traffic received from the VXLAN/NVGRE network. Boutros Expires January 16, 2014 [Page 4] INTERNET DRAFT VXLAN-EVPN July 16, 2013 Each PE node implements EVPN or PBB-EVPN to distribute in BGP either the client MAC addresses learnt over the VXLAN tunnel in case of EVPN, or the PEs' B-MAC addresses in case of PBB-EVPN. In the PBB- EVPN case, client MAC addresses will continue to be learnt in data plane. Each PE node would encapsulate the Ethernet frames with MPLS when sending the packets over the MPLS core and with the VXLAN or NVGRE tunnel header when sending the packets over the VXLAN or NVGRE Network. +--------------+ | | +---------+ +----+ MPLS +----+ +---------+ +-----+ | |---|PE1 | |PE3 |--| | +-----+ |NVE1 |--| | +----+ +----+ | |--|NVE3 | +-----+ | VXLAN | +----+ +----+ | VXLAN | +-----+ +-----+ | |---|PE2 | |PE4 |--| | +-----+ |NVE2 |--| | +----+Backbone+----+ | |--|NVE4 | +-----+ +---------+ +--------------+ +---------+ +-----+ |<--- Underlay IGP ---->|<-Overlay BGP->|<--- Underlay IGP --->| CP |<----- VXLAN --------->|<EVPN/PBB-EVPN>|<------ VXLAN ------->| DP |<----MPLS----->| Legend: CP = Control Plane View DP = Data Plane View Figure 1: Interconnecting VXLAN Networks with VXLAN-EVPN 3.1. Redundancy and All-Active Multi-homing When a VXLAN network is multi-homed to two or more PEs, and provided that these PEs have the same IGP distance to a given NVE, the solution MUST support load-balancing of traffic between the NVE and the MPLS network, among all the multi-homed PEs. This maximizes the use of the bisectional bandwidth of the VXLAN network. One of the main capabilities of EVPN/PBB-EVPN is the support for all-active multi-homing, where the known unicast traffic to/from a multi-homed site can be forwarded by any of the PEs attached to that site. This ensures optimal usage of multiple paths and load balancing. EVPN/PBB- EVPN, through its DF election and split-horizon filtering mechanisms, ensures that no packet duplication or forwarding loops result in such scenarios. In this solution, the VXLAN network is treated as a multi-homed site for the purpose of EVPN operation. Since the context of this solution is VXLAN networks with data-plane Boutros Expires January 16, 2014 [Page 5] INTERNET DRAFT VXLAN-EVPN July 16, 2013 learning paradigm, it is important for the multi-homing mechanism to ensure stability of the MAC forwarding tables at the NVEs, while supporting all-active forwarding at the PEs. For example, in Figure 1 above, if each PE uses a distinct IP address for its VTEP tunnel, then for a given VNI, when an NVE learns a host's MAC address against the originating VTEP source address, its MAC forwarding table will keep flip-flopping among the VTEP addresses of the local PEs. This is because a flow associated with the same host MAC address can arrive at any of the PE devices. In order to ensure that there is no flip/flopping of MAC-to-VTEP address associations, an IP Anycast address MUST be used as the VTEP address on all PEs multi-homed to a given VXLAN network. The use of IP Anycast address has two advantages: a) It prevents any flip/flopping in the forwarding tables for the MAC-to-VTEP associations b) It enables load-balancing via ECMP for DCI traffic among the multi-homed PEs In the baseline [EVPN] draft, the all-active multi-homing is described for a multi-homed device (MHD) using [LACP] and the single- active multi-homing is described for a multi-homed network (MHN) using [802.1Q]. In this draft, the all-active multi-homing is described for a VXLAN MHN. This implies some changes to the filtering which will be described in details in the multicast section (Section 4.6.2). The filtering used for BUM traffic of all-active multi-homing in [EVPN] is asymmetric; where the BUM traffic from the MPLS/IP network towards the multi-homed site is filtered on non-DF PE(s) and it passes thorough the DF PE. There is no filtering of BUM traffic originating from the multi-homed site because of the use of Ethernet Link Aggregation: the MHD hashes the BUM traffic to only a single link. However, in this solution because BUM traffic can arrive at both PEs in both core-to-site and site-to-core directions, the filtering needs to be symmetric just like the filtering of BUM traffic for single-active multi-homing (on a per service instance/VLAN basis). 4. EVPN Routes This solution leverages the same BGP Routes and Attributes defined in [EVPN], adapted as follows: 4.1. BGP MAC Advertisement Route Boutros Expires January 16, 2014 [Page 6] INTERNET DRAFT VXLAN-EVPN July 16, 2013 This route and its associated modes are used to distribute the customer MAC addresses learnt in data plane over the VXLAN tunnel in case of EVPN. Or can be used to distribute the provider Backbone MAC addresses in case of PBB-EVPN. In case of EVPN, the Ethernet Tag ID of this route is set to zero for VNI-based mode, where there is one-to-one mapping between a VNI and an EVI. In such case, there is no need to carry the VNI in the MAC advertisement route because BD ID can be derived from the RT associated with this route. However, for VNI-aware bundle mode, where there is multiple VNIs can be mapped to the same EVI, the Ethernet Tag ID MUST be set to the VNI. At the receiving PE, the BD ID is derived from the combination of RT + VNI - e.g., the RT identifies the associated EVI on that PE and the VNI identifies the corresponding BD ID within that EVI. 4.2. Ethernet Auto-Discovery Route When EVPN is used, the application of this route is as specified in [EVPN]. However, when PBB-EVPN is used, there is no need for this route per [PBB-EVPN]. 4.3. Per VPN Route Targets VXLAN-EVPN uses the same set of route targets defined in [EVPN]. 4.4 Inclusive Multicast Route The EVPN Inclusive Multicast route is used for auto-discovery of PE devices participating in the same tenant virtual network identified by a VNI over the MPLS network. It also enables the stitching of the IP multicast trees, which are local to each VXLAN site, with the Label Switched Multicast (LSM) trees of the MPLS network. The Inclusive Multicast Route is encoded as follow: - Ethernet Tag ID is set to zero for VNI-based mode and to VNI for VNI-aware bundle mode. - Originating Router's IP Address is set to one of the PE's IP addresses. All other fields are set as defined in [EVPN]. Please see section 4.6 "Handling Multicast" 4.5. Unicast Forwarding Boutros Expires January 16, 2014 [Page 7] INTERNET DRAFT VXLAN-EVPN July 16, 2013 Host MAC addresses will be learnt in data plane from the VXLAN network and associated with the corresponding VTEP identified by the source IP address. Host MAC addresses will be learnt in control plane if EVPN is implemented over the MPLS/IP core, or in the data-plane if PBB-EVPN is implemented over the MPLS core. When Host MAC addressed are learned in data plane over MPLS/IP core [in case of PBB-EVPN], they are associated with their corresponding BMAC addresses. L2 Unicast traffic destined to the VXLAN network will be encapsulated with the IP/UDP header and the corresponding customer bridge VNI. L2 Unicast traffic destined to the MPLS/IP network will be encapsulated with the MPLS label. 4.6. Handling Multicast Each VXLAN network independently builds its P2MP or MP2MP shared multicast trees. A P2MP or MP2MP tree is built for one or more VNIs local to the VXLAN network. In the MPLS/IP network, multiple options are available for the delivery of multicast traffic: - Ingress replication - LSM with Inclusive trees - LSM with Aggregate Inclusive trees - LSM with Selective trees - LSM with Aggregate Selective trees When LSM is used, the trees are P2MP. The PE nodes are responsible for stitching the IP multicast trees, on the access side, to the ingress replication tunnels or LSM trees in the MPLS/IP core. The stitching must ensure that the following characteristics are maintained at all times: 1. Avoiding Packet Duplication: In the case where the VXLAN network is multi-homed to multiple PE nodes, if all of the PE nodes forward the same multicast frame, then packet duplication would arise. This applies to both multicast traffic from site to core as well as from core to site. 2. Avoiding Forwarding Loops: In the case of VXLAN network multi- homing, the solution must ensure that a multicast frame forwarded by a given PE to the MPLS core is not forwarded back by another PE (in the same VXLAN network) to the VXLAN network of origin. The same applies for traffic in the core to site direction. The following approach of per-VNI load balancing can guarantee proper Boutros Expires January 16, 2014 [Page 8] INTERNET DRAFT VXLAN-EVPN July 16, 2013 stitching that meets the above requirements. 4.6.2. Multicast Stitching with Per-VNI Load Balancing To setup multicast trees in the VXLAN network for DC applications, PIM Bidir can be of special interest because it reduces the amount of multicast state in the network significantly. Furthermore, it alleviates any special processing for RPF check since PIM Bidir doesn't require any RPF check. The RP for PIM Bidir can be any of the spine nodes. Multiple trees can be built (e.g., one tree rooted per spine node) for efficient load-balancing within the network. All PEs participating in the multi-homing of the VXLAN network join all the trees. Therefore, for a given tree, all PEs receive BUM traffic. DF election procedures of [EVPN] are used to ensure that only traffic to/from a single PE is forwarded, thus avoiding packet duplications and forwarding loops. For load-balancing of BUM traffic, when a PE or an NVE wants to send BUM traffic over the VXLAN network, it selects one of the trees based on its VNI and forwards all the traffic for that VNI on that tree. PIM SM will be described in future revision of this draft. Multicast traffic from VXLAN/NVGRE is first subjected to filtering based on DF election procedures of [EVPN] using the VNI as the Ethernet Tag. This is similar to filtering in [EVPN] in principal; however, instead of VLAN ID, VNI is used for filtering, and instead of being 802.1Q frame, it is a VXLAN encapsulated packet. On the DF PE, where the multicast traffic is allowed to be forwarded, the VNI is used to select a bridge domain,. After the packet is de- capsulated, an L2 lookup is performed based on host MAC DA. It should be noted that the MAC learning is performed in data-plane for the traffic received from the VXLAN/NVGRE network and the host MAC SA is learnt against the source VTEP address. The PE nodes, connected to a multi-homed VXLAN network, perform BGP DF election to decide which PE node is responsible for forwarding multicast traffic associated with a given VNI. A PE would forward multicast traffic for a given VNI only when it is the DF for this VNI. This forwarding rule applies in both the site-to-core as well as core-to-site directions. 5. NVGRE Just like VXLAN, all the above specification would apply for NVGRE, replacing the VNI with Virtual Subnet Identifier (VSID) and the VTEP with NVGRE Endpoint. Boutros Expires January 16, 2014 [Page 9] INTERNET DRAFT VXLAN-EVPN July 16, 2013 6. Acknowledgements TBD. 7. Security Considerations There are no additional security aspects that need to be discussed here. 8. IANA Considerations TBD. 9. References 9.1 Normative References [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 9.2 Informative References [EVPN] Sajassi et al., "BGP MPLS Based Ethernet VPN", draft-ietf- l2vpn-evpn-00.txt, work in progress, February, 2012. [TRILL] Sajassi et al., TRILL-EVPN draft-ietf-l2vpn-trill-evpn-00, work in progress, June 2012. [VXLAN] Mahalingam, Dutt et al., A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks draft-mahalingam- dutt-dcops-vxlan-02.txt, work in progress, August, 2012. [NVGRE] Sridharan et al., Network Virtualization using Generic Routing Encapsulation draft-sridharan-virtualization-nvgre-01.txt, work in progress, July, 2012. Authors' Addresses Sami Boutros Cisco EMail: email@example.com Ali Sajassi Cisco EMail: firstname.lastname@example.org Samer Salam Boutros Expires January 16, 2014 [Page 10] INTERNET DRAFT VXLAN-EVPN July 16, 2013 Cisco EMail: email@example.com Dennis Cai Cisco EMail: firstname.lastname@example.org John Drake Juniper Networks Email: email@example.com Samir Thoria Cisco EMail: firstname.lastname@example.org Boutros Expires January 16, 2014 [Page 11]