INTERNET-DRAFT Mingui Zhang Intended Status: Proposed Standard Huawei Radia Perlman EMC Hongjun Zhai JIT Muhammad Durrani Cisco Systems Sujay Gupta IP Infusion Expires: March 28, 2016 September 25, 2015 TRILL Active-Active Edge Using Multiple MAC Attachments draft-ietf-trill-aa-multi-attach-06.txt Abstract TRILL (Transparent Interconnection of Lots of Links) active-active service provides end stations with flow level load balance and resilience against link failures at the edge of TRILL campuses as described in RFC 7379. This draft specifies a method by which member RBridges in an active- active edge RBridge group use their own nicknames as ingress RBridge nicknames to encapsulate frames from attached end systems. Thus, remote edge RBridges (who are not in the group) will see one host MAC address being associated with the multiple RBridges in the group. Such remote edge RBridges are required to maintain all those associations (i.e., MAC attachments) and to not flip-flop among them which would be the behavior prior to this specification. Design goals of this specification are discussed in the 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 Mingui Zhang, et al Expires March 28, 2016 [Page 1] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html Copyright and License 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 2. Acronyms and Terminology . . . . . . . . . . . . . . . . . . . 4 2.1. Acronyms and Terms . . . . . . . . . . . . . . . . . . . . 4 2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Incremental Deployable Options . . . . . . . . . . . . . . . . 6 4.1. Details of Option B . . . . . . . . . . . . . . . . . . . . 7 4.1.1. Advertising Data Labels for Active-Active Edge . . . . 7 4.1.2. Discovery of Active-Active Edge Members . . . . . . . . 7 4.1.3. Advertising Learned MAC Addresses . . . . . . . . . . . 8 4.2. Extended RBridge Capability Flags APPsub-TLV . . . . . . . 10 5. Meeting the Design Goals . . . . . . . . . . . . . . . . . . . 11 5.1. No MAC Flip-Flopping (Normal Unicast Egress) . . . . . . . 11 5.2. Regular Unicast/Multicast Ingress . . . . . . . . . . . . . 12 5.3. Correct Multicast Egress . . . . . . . . . . . . . . . . . 12 5.3.1. No Duplication (Single Exit Point) . . . . . . . . . . 12 5.3.2. No Echo (Split Horizon) . . . . . . . . . . . . . . . . 12 5.4. No Black-hole or Triangular Forwarding . . . . . . . . . . 13 5.5. Load Balance Towards the AAE . . . . . . . . . . . . . . . 13 5.6. Scalability . . . . . . . . . . . . . . . . . . . . . . . . 14 6. E-L1FS Backwards Compatibility . . . . . . . . . . . . . . . . 14 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 14 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 15 8.1. TRILL APPsub-TLVs . . . . . . . . . . . . . . . . . . . . . 15 Mingui Zhang, et al Expires March 28, 2016 [Page 2] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 8.2. Extended RBridge Capabilities Registry . . . . . . . . . . 15 8.3. Active-Active Flags . . . . . . . . . . . . . . . . . . . . 15 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 10.1. Normative References . . . . . . . . . . . . . . . . . . . 16 10.2. Informative References . . . . . . . . . . . . . . . . . . 17 Appendix A. Scenarios for Split Horizon . . . . . . . . . . . . . 17 Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20 1. Introduction As discussed in [RFC7379], in a TRILL (Transparent Interconnection of Lots of Links) Active-Active Edge (AAE) topology, a Local Active- Active Link Protocol (LAALP), for example, a Multi-Chassis Link Aggregation Group (MC-LAG), is used to connect multiple RBridges to multi-port Customer Equipment (CE), such as a switch, vSwitch or a multi-port end station. A set of endnodes are attached in the case of switch or vSwitch. It is required that data traffic within a specific VLAN from this endnode set (including the multi-port end station case) can be ingressed and egressed by any of these RBridges simultaneously. End systems in the set can spread their traffic among these edge RBridges at the flow level. When a link fails, end systems keep using the remaining links in the LAALP without waiting for the convergence of TRILL, which provides resilience to link failures. Since a frame from each endnode can be ingressed by any RBridge in the local AAE group, a remote edge RBridge may observe multiple attachment points (i.e., egress RBridges) for this endnode. This issue is known as the "MAC flip-flopping". See [RFC7379] for a discussion of the MAC flip-flopping issue. In this document, AAE member RBridges use their own nicknames to ingress frames into the TRILL campus. Remote edge RBridges are required to keep multiple points of attachment per MAC address and Data Label (VLAN or Fine Grained Label [RFC7172]) attached to the AAE. This addresses the MAC flip-flopping issue. The use of the solution, as specified in this document, in an AAE group does not prohibit the use of other solutions in other AAE groups in the same TRILL campus. For example, the specification in this draft and the specification in [PN] could be simultaneously deployed for different AAE groups in the same campus. The main body of this document is organized as follows. Section 2 lists acronyms and terminologies. Section 3 gives the overview model. Section 4 provides options for incremental deployment. Section 5 describes how this approach meets the design goals. The Sections after Section 5 cover security, IANA, and some backwards compatibility considerations. Mingui Zhang, et al Expires March 28, 2016 [Page 3] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 2. Acronyms and Terminology 2.1. Acronyms and Terms AAE: Active-Active Edge Campus: a TRILL network consisting of TRILL switches, links, and possibly bridges bounded by end stations and IP routers. For TRILL, there is no "academic" implication in the name "campus". CE: Customer Equipment (end station or bridge). The device can be either physical or virtual equipment. Data Label: VLAN or FGL DRNI: Distributed Resilient Network Interconnect. A link aggregation specified in [802.1AX] that can provide an LAALP between from 1 to 3 CEs and 2 or 3 RBridges. Edge RBridge: An RBridge providing end station service on one or more of its ports. E-L1FS: Extended Level 1 Flooding Scope ESADI: End Station Address Distribution Information [RFC7357] FGL: Fine Grained Label [RFC7172] FS-LSP: Flooding Scoped Link State PDU IS: Intermediate System [ISIS] IS-IS: Intermediate System to Intermediate System [ISIS] LAALP: As in [RFC7379], Local Active-Active Link Protocol. Any protocol similar to MC-LAG (or DRNI) that runs in a distributed fashions on a CE, the links from that CE to a set of edge group RBridges, and on those RBridges. LSP: Link State PDU MC-LAG: Multi-Chassis LAG. Proprietary extensions of Link Aggregation [802.1AX] that can provide an LAALP between one CE and 2 or more RBridges. PDU: Protocol Data Unit RBridge: A device implementing the TRILL protocol. Mingui Zhang, et al Expires March 28, 2016 [Page 4] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 TRILL: TRansparent Interconnection of Lots of Links or Tunneled Routing in the Link Layer [RFC6325] [RFC7177]. TRILL switch: An alternative name for an RBridge. vSwitch: A virtual switch such as a hypervisor that also simulates a bridge. 2.2. 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 [RFC2119]. Familiarity with [RFC6325], [RFC6439] and [RFC7177] is assumed in this document. 3. Overview +-----+ | RB4 | +----------+-----+----------+ | | | | | Rest of campus | | | | | +-+-----+--+-----+--+-----+-+ | RB1 | | RB2 | | RB3 | +-----\ +-----+ /-----+ \ | / \ | / |||LAALP1 ||| +---+ | B | +---+ H1 H2 H3 H4: VLAN 10 Figure 3.1: An example topology for TRILL Active-Active Edge Figure 3.1 shows an example network for TRILL Active-Active Edge (See also Figure 1 in [RFC7379]). In this figure, endnodes (H1, H2, H3 and H4) are attached to a bridge B that communicates with multiple RBridges (RB1, RB2 and RB3) via the LAALP. Suppose RB4 is a 'remote' RBridge not in the AAE group in the TRILL campus. This connection model is also applicable to the virtualized environment where the physical bridge can be replaced with a vSwitch while those bare metal Mingui Zhang, et al Expires March 28, 2016 [Page 5] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 hosts are replaced with virtual machines (VM). For a frame received from its attached endnode sets, a member RBridge of the AAE group conforming to this document always encapsulates that frame using its own nickname as the ingress nickname no matter whether it's unicast or multicast. With the options specified as follows, even though the remote RBridge RB4 will see multiple attachments for each MAC from one of the end- nodes, the "MAC flip-flopping" will not cause any problem. 4. Incremental Deployable Options Two options are specified. Option A requires new hardware support. Option B can be incrementally implemented throughout a TRILL campus with common existing TRILL fast path hardware. Further details on Option B are given in Section 4.1. -- Option A A new capability announcement would appear in LSPs: "I can cope with data plane learning of multiple attachments for an endnode". This mode of operation is generally not supported by existing TRILL fast path hardware. Only if all edge RBridges, to which the group has data connectivity, and that are interested in any of the Data Labels in which the AAE is interested, announce this capability, can the AAE group safely use this approach. If all such RBridges do not announce this "Option A" capability, then a fallback would be needed such as reverting from active-active to active-standby operation or isolating the RBridges that would need to support this capability and do not support it. Further details for Options A are beyond the scope of this document except that in Section 4.2 a bit is reserved to indicate support for Option A because a remote RBridge supporting Option A is compatible with an AAE group using Option B. -- Option B As pointed out in Section 4.2.6 of [RFC6325] and Section 5.3 of [RFC7357], one MAC address may be persistently claimed to be attached to multiple RBridges within the same Data Label in the TRILL ESADI-LSPs. For Option B, AAE member RBridges make use of the TRILL ESADI (End Station Address Distribution Information) protocol to distribute multiple attachments of a MAC address. Remote RBridges SHOULD disable the data plane MAC learning for such multi-attached MAC addresses from TRILL Data packet decapsulation unless they also support Option A. The ability to configure an RBridge to disable data plane learning is provided by Mingui Zhang, et al Expires March 28, 2016 [Page 6] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 the base TRILL protocol [RFC6325]. 4.1. Details of Option B With Option B, the receiving edge RBridges MUST avoid flip-flop errors for MAC addresses learned from the TRILL Data packet decapsulation for the originating RBridge within these Data Labels. It is RECOMMENDED that the receiving edge RBridge disable the data plane MAC learning from TRILL Data packet decapsulation within those advertised Data Labels for the originating RBridge unless the receiving RBridge also supports Option A. Alternative implementations that produce the same expected behavior, i.e., the receiving edge RBridge does not flip-flop among multiple MAC attachments, are acceptable. For example, the confidence level mechanism as specified in [RFC6325] can be used. Let the receiving edge RBridge give a prevailing confidence value (e.g., 0x21) to the first MAC attachment learned from the data plane over others from the TRILL Data packet decapsulation. The receiving edge RBridge will stick to this MAC attachment until it is overridden by one learned from the ESADI protocol [RFC7357]. The MAC attachment learned from ESADI is set to have higher confidence value (e.g., 0x80) to override any alternative learning from the decapsulation of received TRILL Data packets [RFC6325]. 4.1.1. Advertising Data Labels for Active-Active Edge RBridge in an AAE group MUST participate in ESADI in Data Labels enabled for its attached LAALPs. This document further registers two data flags, which are used to advertise that the originating RBridge supports and participates in an Active-Active Edge. These two flags are allocated from the Interested VLANs Flag Bits that appear in the Interested VLANs and Spanning Tree Roots Sub-TLV and the Interested Labels Flag Bits that appear in the Interested Labels and Spanning Tree Roots Sub-TLV [RFC7176] (see Section 8.3). When these flags are set to 1, the originating RBridge is advertising Data Labels for LAALPs rather than plain LAN links. 4.1.2. Discovery of Active-Active Edge Members Remote edge RBridges need to discover RBridges in an AAE. This is achieved by listening to the following "AA LAALP Group RBridges" TRILL APPsub-TLV included in the TRILL GENINFO TLV in FS-LSPs [RFC7180bis]. Mingui Zhang, et al Expires March 28, 2016 [Page 7] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = AA-LAALP-GROUP-RBRIDGES| (2 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | (2 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sender Nickname | (2 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LAALP ID Size | (1 byte) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+ | LAALP ID (k bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+ o Type: AA LAALP Group RBridges (TRILL APPsub-TLV type tbd1) o Length: 3+k o Sender Nickname: The nickname the originating RBridge will use as the ingress nickname. This field is useful because the originating RBridge might own multiple nicknames. o LAALP ID Size: The length k of the LAALP ID in bytes. o LAALP ID: The ID of the LAALP which is k bytes long. If the LAALP is an MC-LAG or DRNI, it is the 8-byte ID specified in Clause 6.3.2 in [802.1AX]. This APPsub-TLV is expected to rarely change as it only does so in cases of the creation or elimination of an AAE group or of link failure or restoration to the CE in such a group. 4.1.3. Advertising Learned MAC Addresses Whenever MAC addresses from the LAALP of this AAE are learned through ingress or configuration, the originating RBridge MUST advertise these MAC addresses using the MAC-Reachability TLV [RFC6165] via the ESADI protocol [RFC7357]. The MAC-Reachability TLVs are composed in a way that each TLV only contains MAC addresses of end-nodes attached to a single LAALP. Each such TLV is enclosed in a TRILL APPsub-TLV defined as follows. Mingui Zhang, et al Expires March 28, 2016 [Page 8] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = AA-LAALP-GROUP-MAC | (2 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | (2 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LAALP ID Size | (1 byte) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+ | LAALP ID (k bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+ | MAC-Reachability TLV (7 + 6*n bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+ o Type: AA LAALP Group MAC (TRILL APPsub-TLV type tbd2) o Length: The MAC-Reachability TLV [RFC6165] is contained in the value field as a sub-TLV. The total number of bytes contained in the value field is given by k+8+6*n. o LAALP ID Size: The length k of the LAALP ID in bytes. o LAALP ID: The ID of the LAALP that is k bytes long. Here, it also serves as the identifier of the AAE. If the LAALP is an MC-LAG (or DRNI), it is the 8 byte ID as specified in Clause 6.3.2 in [802.1AX]. o MAC-Reachability sub-TLV: The AA-LAALP-GROUP-MAC APPsub-TLV value contains the MAC-Reachability TLV as a sub-TLV (see [RFC6165], n is the number of MAC addresses present). As specified in Section 2.2 in [RFC7356], the type and length fields of the MAC- Reachability TLV are encoded as unsigned 16 bit integers. The one octet unsigned Confidence along with these TLVs SHOULD be set to prevail over those MAC addresses learned from TRILL Data decapsulation by remote edge RBridges. This AA-LAALP-GROUP-MAC APPsub-TLV MUST be included in a TRILL GENINFO TLV [RFC7357] in the ESADI-LSP. There may be more than one occurrence of such TRILL APPsub-TLV in one ESADI-LSP fragment. For those MAC addresses contained in an AA-LAALP-GROUP-MAC APPsub- TLV, this document applies. Otherwise, [RFC7357] applies. For example, an AAE member RBridge continues to enclose MAC addresses learned from TRILL Data packet decapsulation in MAC-Reachability TLV as per [RFC6165] and advertise them using the ESADI protocol. When the remote RBridge learns MAC addresses contained in the AA- LAALP-GROUP-MAC APPsub-TLV via the ESADI protocol [RFC7357], it sends the packets destined to these MAC addresses to the closest one (the one to which the remote RBridge has the least cost forwarding path) Mingui Zhang, et al Expires March 28, 2016 [Page 9] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 of those RBridges in the AAE identified by the LAALP ID in the AA- LAALP-GROUP-MAC APPsub-TLV. If there are multiple equal least cost member RBridges, the ingress RBridge is required to select a unique one in a pseudo-random way as specified in Section 5.3 of [RFC7357]. When another RBridge in the same AAE group receives an ESADI-LSP with the AA-LAALP-GROUP-MAC APPsub-TLV, it also learns MAC addresses of those end-nodes served by the corresponding LAALP. These MAC addresses SHOULD be learned as if those end-nodes are locally attached to this RBridge itself. An AAE member RBridge MUST use the AA-LAALP-GROUP-MAC APPsub-TLV to advertise in ESADI the MAC addresses learned from a plain local link (a non LAALP link) with Data Labels that happen to be covered by the Data Labels of any attached LAALP. The reason is that MAC learning from TRILL Data packet decapsulation within these Data Labels at the remote edge RBridge has normally been disabled for this RBridge. This APPsub-TLV changes whenever the MAC reachability situation for the LAALP changes. 4.2. Extended RBridge Capability Flags APPsub-TLV The following Extended RBridge Capability Flags APPsub-TLV will be included in an E-L1FS FS-LSP fragment zero [RFC7180bis] as an APPsub- TLV of the TRILL GENINFO-TLV. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type = EXTENDED-RBRIDGE-CAP | (2 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | (2 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Topology | (2 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |E|H| Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved (continued) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ o Type: Extended RBridge Capability (TRILL APPsub-TLV type tbd3) o Length: Set to 8. o Topology: Indicates the topology to which the capabilities apply. When this field is set to zero, this implies that the capabilities apply to all topologies or topologies are not in use [TRILL-MT]. o E: Bit 0 of the capability bits. When this bit is set, it Mingui Zhang, et al Expires March 28, 2016 [Page 10] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 indicates the originating RBridge acts as specified in Option B above. o H: Bit 1 of the capability bits. When this bit is set, it indicates that the originating RBridge keeps multiple MAC attachments learned from TRILL Data packet decapsulation with fast path hardware, that is, it acts as specified in Option A above. o Reserved: Flags extending from bit 2 through bit 63 of the capability fits reserved for future use. These MUST be sent as zero and ignored on receipt. The Extended RBridge Capability Flags TRILL APPsub-TLV is used to notify other RBridges whether the originating RBridge supports the capability indicated by the E and H bits. For example, if E bit is set, it indicates the originating RBridge will act as defined in Option B. That is, it will disable the MAC learning from TRILL Data packet decapsulation within Data Labels advertised by AAE RBridges while waiting for the TRILL ESADI-LSPs to distribute the {MAC, Nickname, Data Label} association. Meanwhile, this RBridge is able to act as an AAE RBridge. It's required to advertise MAC addresses learned from local LAALPs in TRILL ESADI-LSPs using the AA-LAALP- GROUP-MAC APPsub-TLV defined in Section 4.1. If an RBridge in an AAE group, as specified herein, observe a remote RBridge interested in one or more of that AAE group's Data Labels, and the remote RBridge does not support, as indicated by its extended capabilities, either Option A or Option B, then the AAE group MUST fall back to active- standby mode. This APPsub-TLV is expected to rarely change as it only needs to be updated when RBridge capabilities change, such as due to an upgrade or reconfiguration. 5. Meeting the Design Goals This section explores how this specification meets the major design goals of AAE. 5.1. No MAC Flip-Flopping (Normal Unicast Egress) Since all RBridges talking with the AAE RBridges in the campus are able to see multiple attachments for one MAC address in ESADI [RFC7357], a MAC address learned from one AAE member will not be overwritten by the same MAC address learned from another AAE member. Although multiple entries for this MAC address will be created, for return traffic the remote RBridge is required to adhere to a unique one of the attachments for each MAC address rather than keep flip- flopping among them (see Section 4.2.6 of [RFC6325] and Section 5.3 Mingui Zhang, et al Expires March 28, 2016 [Page 11] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 of [RFC7357]). 5.2. Regular Unicast/Multicast Ingress LAALP guarantees that each frame will be sent upward to the AAE via exactly one uplink. RBridges in the AAE simply follow the process per [RFC6325] to ingress the frame. For example, each RBridge uses its own nickname as the ingress nickname to encapsulate the frame. In such a scenario, each RBridge takes for granted that it is the Appointed Forwarder for the VLANs enabled on the uplink of the LAALP. 5.3. Correct Multicast Egress A fundamental design goal of AAE is that there must be no duplication or forwarding loop. 5.3.1. No Duplication (Single Exit Point) When multi-destination TRILL Data packets for a specific Data Label are received from the campus, it's important that exactly one RBridge out of the AAE group let through each multi-destination packet so no duplication will happen. The LAALP will have defined its selection function (using hashing or election algorithm) to designated a forwarder for a multi-destination frame. Since AAE member RBridges support the LAALP, they are able to utilize that selection function to determine the single exit point. If the output of the selection function points to the port attached to the receiving RBridge itself (i.e., the packet should be egressed out of this node), the receiving RBridge MUST egress this packet for that AAE group. Otherwise, the packet MUST NOT be egressed for that AAE group. (For ports that lead to non-AAE links, the receiving RBridge determines whether to egress the packet or not according to [RFC6325] which is updated by [RFC7172].) 5.3.2. No Echo (Split Horizon) When a multi-destination frame originated from an LAALP is ingressed by an RBridge of an AAE group, distributed to the TRILL network and then received by another RBridge in the same AAE group, it is important that this receiving RBridge does not egress this frame back to this LAALP. Otherwise, it will cause a forwarding loop (echo). The well known 'split horizon' technique (as discussed in Section 2.2.1 of [RFC1058]) is used to eliminate the echo issue. RBridges in the AAE group need to split horizon based on the ingress RBridge nickname plus the VLAN of the TRILL Data packet. They need to set up per port filtering lists consisting of the tuple of . Packets with information matching with any entry of Mingui Zhang, et al Expires March 28, 2016 [Page 12] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 the filtering list MUST NOT be egressed out of that port. The information of such filters is obtained by listening to the AA-LAALP- GROUP-RBRIDGES TRILL APPsub-TLVs as defined in Section 4.1.2. Note that all enabled VLANs MUST be consistent on all ports connected to an LAALP. So the enabled VLANs need not be included in these TRILL APPsub-TLVs. They can be locally obtained from the port attached to that LAALP. Through parsing these APPsub-TLVs, the receiving RBridge discovers all other RBridges connected to the same LAALP. The Sender Nickname of the originating RBridge will be added into the filtering list of the port attached to the LAALP. For example, RB3 in Figure 3.1 will set up a filtering list that looks like {, } on its port attached to LAALP1. According to split horizon, TRILL Data packets within VLAN10 ingressed by RB1 or RB2 will not be egressed out of this port. When there are multiple LAALPs connected to the same RBridge, these LAALPs may have VLANs that overlap. Here a VLAN overlaps means this VLAN ID is enabled by multiple LAALPs. A customer may require that hosts within these overlapped VLANs communicate with each other. In Appendix A, several scenarios are given to explain how hosts communicate within the overlapped VLANs and how split horizon happens. 5.4. No Black-hole or Triangular Forwarding If a sub-link of the LAALP fails while remote RBridges continue to send packets towards the failed port, a black-hole happens. If the AAE member RBridge with that failed port starts to redirect the packets to other member RBridges for delivery, triangular forwarding occurs. The member RBridge attached to the failed sub-link makes use of the ESADI protocol to flush those failure affected MAC addresses as defined in Section 5.2 of [RFC7357]. After doing that, no packets will be sent towards the failed port, hence no black-hole will happen. Nor will the member RBridge need to redirect packets to other member RBridges, which may otherwise lead to triangular forwarding. 5.5. Load Balance Towards the AAE Since a remote RBridge can see multiple attachments of one MAC address in ESADI, this remote RBridge can choose to spread the traffic towards the AAE members on a per flow basis. Each of them is able to act as the egress point. In doing this, the forwarding paths need not be limited to the least cost path selection from the ingress RBridge to the AAE RBridges. The traffic load from the remote RBridge towards the AAE RBridges can be balanced based on a pseudo-random selection method (see Section 4.1). Mingui Zhang, et al Expires March 28, 2016 [Page 13] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 Note that the load balance method adopted at a remote ingress RBridge is not to replace the load balance mechanism of LAALP. These two load spreading mechanisms should take effect separately. 5.6. Scalability With Option A, multiple attachments need to be recorded for a MAC address learned from AAE RBridges. More entries may be consumed in the MAC learning table. However, MAC addresses attached to an LAALP are usually only a small part of all MAC addresses in the whole TRILL campus. As a result, the extra space required by the multi-attached MAC addresses can usually be accommodated by RBridges unused MAC table space. With Option B, remote RBridges will keep the multiple attachments of a MAC address in the ESADI link state databases that are usually maintained by software. While in the MAC table that is normally implemented in hardware, an RBridge still establishes only one entry for each MAC address. 6. E-L1FS Backwards Compatibility The Extended TLVs defined in Section 4 and 5 are to be used in an Extended Level 1 Flooding Scope ( E-L1FS [RFC7356] [RFC7180bis]) PDU. For those RBridges that do not support E-L1FS, the EXTENDED-RBRIDGE- CAP TRILL APPsub-TLV will not be sent out either, and MAC multi- attach active-active is not supported. 7. Security Considerations For security considerations pertaining to extensions transported by TRILL ESADI, see the Security Considerations section in [RFC7357]. For extensions not transported by TRILL ESADI, RBridges may be configured to include the IS-IS Authentication TLV (10) in the IS-IS PDUs to use the IS-IS security [RFC5304][RFC5310]. Since currently deployed LAALPs [RFC7379] are proprietary, security over membership in and internal management of active-active edge groups is proprietary. In the environment that above authentication are not adopted, a rogue RBridge that insinuates itself into an active-active edge group can disrupt end station traffic flowing into or out of that group. For example, if there are N RBridges in the group, it could typically control 1/Nth of the traffic flowing out of that group and a similar amount of unicast traffic flowing into that group. For general TRILL security considerations, see [RFC6325]. Mingui Zhang, et al Expires March 28, 2016 [Page 14] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 8. IANA Considerations 8.1. TRILL APPsub-TLVs IANA is requested to allocate three new types under the TRILL GENINFO TLV [RFC7357] for the TRILL APPsub-TLVs defined in Section 4.1 of this document. The following entries are added to the "TRILL APPsub- TLV Types under IS-IS TLV 251 Application Identifier 1" Registry on the TRILL Parameters IANA web page. Type Name Reference --------- ---- --------- tbd1(252) AA-LAALP-GROUP-RBRIDGES [This document] tbd2(253) AA-LAALP-GROUP-MAC [This document] tbd3(254) EXTENDED-RBRIDGE-CAP [This document] 8.2. Extended RBridge Capabilities Registry IANA is requested to create a registry under the TRILL Parameters registry as follows: Name: Extended RBridge Capabilities Registration Procedure: Expert Review Reference: [this document] Bit Mnemonic Description Reference ---- -------- ----------- --------- 0 E Option B Support [this document] 1 H Option A Support [this document] 2-63 - Unassigned 8.3. Active-Active Flags IANA is requested to allocate two flag bits, with mnemonic "AA", as follows: One flag bit is allocated from the Interested VLANs Flag Bits. Bit Mnemonic Description Reference --- -------- ----------- --------- tbd4(16) AA VLANs for Active-Active [This document] One flag bit is allocated from the Interested Labels Flag Bits. Mingui Zhang, et al Expires March 28, 2016 [Page 15] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 Bit Mnemonic Description Reference --- -------- ----------- --------- tbd5(4) AA FGLs for Active-Active [This document] 9. Acknowledgements Authors would like to thank the comments and suggestions from Andrew Qu, Donald Eastlake, Erik Nordmark, Fangwei Hu, Liang Xia, Weiguo Hao, Yizhou Li and Mukhtiar Shaikh. 10. References 10.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC6165] Banerjee, A. and D. Ward, "Extensions to IS-IS for Layer-2 Systems", RFC 6165, April 2011. [RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A. Ghanwani, "Routing Bridges (RBridges): Base Protocol Specification", RFC 6325, July 2011. [RFC6439] Perlman, R., Eastlake, D., Li, Y., Banerjee, A., and F. Hu, "Routing Bridges (RBridges): Appointed Forwarders", RFC 6439, November 2011. [RFC7172] D. Eastlake 3rd and M. Zhang and P. Agarwal and R. Perlman and D. Dutt, "Transparent Interconnection of Lots of Links (TRILL): Fine-Grained Labeling", RFC 7172, May 2014. [RFC7176] D. Eastlake 3rd and T. Senevirathne and A. Ghanwani and D. Dutt and A. Banerjee, "Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS", RFC7176, May 2014. [RFC7177] D. Eastlake 3rd and R. Perlman and A. Ghanwani and H. Yang and V. Manral, "Transparent Interconnection of Lots of Links (TRILL): Adjacency", RFC 7177, May 2014. [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding Scope Link State PDUs (LSPs)", RFC 7356, September 2014. [RFC7357] Zhai, H., Hu, F., Perlman, R., Eastlake 3rd, D., and O. Stokes, "Transparent Interconnection of Lots of Links (TRILL): End Station Address Distribution Information (ESADI) Protocol", RFC 7357, September 2014. Mingui Zhang, et al Expires March 28, 2016 [Page 16] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 [RFC7180bis] D. Eastlake, M. Zhang, et al, "TRILL: Clarifications, Corrections, and Updates", draft-ietf-trill-rfc7180bis, work in progress. [802.1AX] IEEE, "IEEE Standard for Local and Metropolitan Area Networks - Link Aggregation", 802.1AX-2014, 24 December 2014. 10.2. Informative References [RFC7379] Li, Y., Hao, W., Perlman, R., Hudson, J., and H. Zhai, "Problem Statement and Goals for Active-Active Connection at the Transparent Interconnection of Lots of Links (TRILL) Edge", RFC 7379, October 2014. [PN] H. Zhai, T. Senevirathne, et al, "TRILL: Pseudo-Nickname for Active-active Access", draft-ietf-trill-pseudonode- nickname, work in progress. [TRILL-MT] D. Eastlake, M. Zhang, A. Banerjee, V. Manral, "TRILL: Multi-Topology", draft-eastlake-trill-multi-topology, work in progress. [ISIS] ISO, "Intermediate system to Intermediate system routeing information exchange protocol for use in conjunction with the Protocol for providing the Connectionless-mode Network Service (ISO 8473)", ISO/IEC 10589:2002. [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC 5310, February 2009. Appendix A. Scenarios for Split Horizon +------------------+ +------------------+ +------------------+ | RB1 | | RB2 | | RB3 | +------------------+ +------------------+ +------------------+ L1 L2 L3 L1 L2 L3 L1 L2 L3 VL10~20 VL15~25 VL15 VL10~20 VL15~25 VL15 VL10~20 VL15~25 VL15 LAALP1 LAALP2 LAN LAALP1 LAALP2 LAN LAALP1 LAALP2 LAN B1 B2 B10 B1 B2 B20 B1 B2 B30 Figure A.1: An example topology to explain split horizon Suppose RB1, RB2 and RB3 are the Active-Active group connecting LAALP1 and LAALP2. LAALP1 and LAALP2 are connected to B1 and B2 at their other ends. Suppose all these RBridges use port L1 to connect LAALP1 while they use port L2 to connect LAALP2. Assume all three L1 Mingui Zhang, et al Expires March 28, 2016 [Page 17] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 enable VLAN 10~20 while all three L2 enable VLAN 15~25. So that there is an overlap of VLAN 15~20. A customer may require that hosts within these overlapped VLANs communicate with each other. That is, hosts attached to B1 in VLAN 15~20 need to communicate with hosts attached to B2 in VLAN 15~20. Assume the remote plain RBridge RB4 also has hosts attached in VLAN 15~20 which need to communicate with those hosts in these VLANs attached to B1 and B2. Two major requirements: 1. Frames ingressed from RB1-L1-VLAN 15~20 MUST NOT be egressed out of ports RB2-L1 and RB3-L1. At the same time, 2. frames coming from B1-VLAN 15~20 should reach B2-VLAN 15~20. RB3 stores the information for split horizon on its ports L1 and L2. On L1: {, } and on L2: {, }. Five clarification scenarios: a. Suppose RB2/RB3 receives a TRILL multi-destination data packet with VLAN 15 and ingress nickname RB1. RB3 is the single exit point (selected out according to the hashing function of LAALP) for this packet. On ports L1 and L2, RB3 has covered , so that RB3 will not egress this packet out of either L1 or L2. Here, _split horizon_ happens. Beforehand, RB1 obtains a native frame on port L1 from B1 in VLAN 15. RB1 judges it should be forwarded as a multi-destination packet across the TRILL campus. Also, RB1 replicates this frame without TRILL encapsulation and sends it out of port L2, so that B2 will get this frame. b. Suppose RB2/RB3 receives a TRILL multi-destination data packet with VLAN 15 and ingress nickname RB4. RB3 is the single exit point. On ports L1 and L2, since RB3 has not stored any tuple with ingress_ nickname_RB4, RB3 will decapsulate the packet and egress it out of both ports L1 and L2. So both B1 and B2 will receive the frame. c. Suppose there is a plain LAN link port L3 on RB1, RB2 and RB3, connecting to B10, B20 and B30 respectively. These L3 ports happen to be configured with VLAN 15. On port L3, RB2 and RB3 stores no information of split horizon for AAE (since this port has not been configured to be in any LAALP). They will egress the packet ingressed from RB1-L1 in VLAN 15. Mingui Zhang, et al Expires March 28, 2016 [Page 18] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 d. If a packet is ingressed from RB1-L1 or RB1-L2 with VLAN 15, port RB1-L3 will not egress packets with ingress-nickname-RB1. RB1 needs to replicate this frame without encapsulation and sends it out of port L3. This kind of 'bounce' behavior for multi- destination frames is just as specified in paragraph 2 of Section 4.6.1.2 of [RFC6325]. e. If a packet is ingressed from RB1-L3, since RB1-L1 and RB1-L2 cannot egress packets with VLAN 15 and ingress-nickname-RB1, RB1 needs to replicate this frame without encapsulation and sends it out of port L1 and L2. (Also see paragraph 2 of Section 4.6.1.2 of [RFC6325].) Mingui Zhang, et al Expires March 28, 2016 [Page 19] INTERNET-DRAFT MAC Multi-Attach for Active/Active September 25, 2015 Author's Addresses Mingui Zhang Huawei Technologies No.156 Beiqing Rd. Haidian District, Beijing 100095 P.R. China EMail: zhangmingui@huawei.com Radia Perlman EMC 2010 256th Avenue NE, #200 Bellevue, WA 98007 USA EMail: radia@alum.mit.edu Hongjun Zhai Jinling Institute of Technology 99 Hongjing Avenue, Jiangning District Nanjing, Jiangsu 211169 China EMail: honjun.zhai@tom.com Muhammad Durrani Cisco Systems 170 West Tasman Dr. San Jose, CA 95134 EMail: mdurrani@cisco.com Sujay Gupta IP Infusion, RMZ Centennial Mahadevapura Post Bangalore - 560048 India EMail: sujay.gupta@ipinfusion.com Mingui Zhang, et al Expires March 28, 2016 [Page 20]