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TRILL                                                        Weiguo Hao
                                                              Yizhou Li
                                                        Donald Eastlake
                                                              Liang Xia
Internet Draft                                                   Huawei
                                                              Andrew Qu
                                                               MediaTec
                                                       Muhammad Durrani
                                                                Brocade
                                                         Ponkarthick S.
                                                            IP Infusion
Intended status: Standards Track                       October 15, 2014
Expires: March 2015



                       TRILL Distributed Layer 3 Gateway
                          draft-hao-trill-irb-05.txt


Abstract

   Currently TRILL protocol provides optimal pair-wise data frame forwarding for
   layer 2 intra-subnet traffic but not for layer 3 inter-subnet traffic. A
   centralized gateway solution is typically used for layer 3 inter-subnet traffic
   forwarding but has following issues:

      1. Sub-optimum forwarding path for inter-subnet traffic.

      2. Huge number of gateway interfaces, 16 million in extreme case, need to be
   supported on the centralized gateway.

      3. Traffic bottleneck at the gateway.

   An optional TRILL distributed gateway solution that resolves these centralized
   gateway issues is specified in this document.


Status of this Memo

   This Internet-Draft is submitted in full conformance with the provisions of BCP 78
   and BCP 79.

   This Internet-Draft is submitted in full conformance with the provisions of BCP 78
   and BCP 79. This document may not be modified, and derivative works of it may not
   be created, and it may not be published except as an Internet-Draft.

   This Internet-Draft is submitted in full conformance with the provisions of BCP 78
   and BCP 79. This document may not be modified, and derivative works of it may not



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   be created, except to publish it as an RFC and to translate it into languages
   other than English.

   Internet-Drafts are working documents of the Internet Engineering Task Force
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   This Internet-Draft will expire on March 15, 2015.

Copyright Notice

   Copyright (c) 2014 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
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   warranty as described in the Simplified BSD License.

Table of Contents

   1. Introduction ................................................ 3
   2. Conventions Used in This Document............................ 3
   3. Problem Statement ........................................... 4
   4. Layer 3 Traffic Forwarding Model............................. 6
   5. Distributed Gateway Solution Overview........................ 6
      5.1. Local routing information............................... 7
      5.2. Local routing information synchronization............... 8
      5.3. Data traffic forwarding process......................... 8
   6. Distributed Layer 3 Gateway Process Example.................. 9
      6.1. Control plane process.................................. 10
      6.2. Data plane process..................................... 11
   7. TRILL Protocol Extensions................................... 12


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      7.1. The tenant gateway MAC APPsub-TLV...................... 12
      7.2. The tenant Label APPsub-TLV............................ 13
      7.3. The IPv4 Prefix APPsub-TLV............................. 14
      7.4. The IPv6 Prefix APPsub-TLV............................. 15
   8. Security Considerations..................................... 15
   9. IANA Considerations ........................................ 16
   10. Normative References....................................... 16
   11. Informative References..................................... 16
   12. Acknowledgments ........................................... 17

1. Introduction

   The IETF has standardized the TRILL (Transparent Interconnection of Lots of Links)
   protocol [RFC6325] that provides a solution for least cost transparent routing in
   multi-hop networks with arbitrary topologies and link technologies, using [IS-IS]
   [RFC7176] link-state routing and a hop count. TRILL switches are sometimes called
   RBridges (Routing Bridges).

   Currently, TRILL provides optimal unicast forwarding for Layer 2 intra-subnet
   traffic but not for Layer 3 inter-subnet traffic. In this document, an optional
   TRILL-based distributed Layer 3 gateway solution is specified to provide optimal
   unicast forwarding for Layer 3 inter-subnet traffic. With distributed gateway
   support an edge RBridge provides both routing based on Layer 2 identity (address
   and virtual network (VN)) among end stations (ESs) that belong to same subnet and
   routing based on Layer 3 identity among ESs that belong to different subnets of
   the same routing domain. An edge RBridge needs to provide routing instances and
   Layer 3 gateway interfaces for local connected ESs. The routing instances are for
   IP address isolation between tenants. In the TRILL distributed Layer 3 gateway
   solution, inter-subnet traffic can be fully dispersed among edge RBridges, so
   there is no single bottleneck.

   This document is organized as follows: Section 3 describes why a distributed
   gateway solution is beneficial. Section 4 gives the Layer 3 traffic forwarding
   model. Section 5 provides a distributed gateway solution overview. Section 6 gives
   a distributed gateway example. And Section 7 describes the TRILL protocol
   extensions needed to support this distributed gateway solution.

2. Conventions Used in This Document

   The terms and acronyms in [RFC6325] are used with the following additions:

      Data Label: VLAN or FGL [RFC7172].

      DCN:   Data Center Network.

      ES:    End Station. VM (Virtual Machine) or physical server, whose address is
   either the destination or source of a data frame.


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      GW:    Gateway.

      Gateway interface:    Layer 3 virtual interface on gateway  aka gateway
   interface) terminates layer 2 forwarding and forwards IP traffic to the
   destination as per IP forwarding rules. Incoming traffic from a physical port on a
   gateway will be distributed to its virtual gateway interface based on Data Label
   (VLAN or FGL).

      L2:    Layer 2.

      L3:    IP Layer 3.

      ND:    IPv6's Neighbor Discovery [RFC4861].

      RD:    Routing Domain.

      ToR:   Top of Rack.

      VN:    Virtual Network. In a TRILL campus, each virtual network is identified
   by a unique 12-bit VLAN ID or 24-bit Fine Grained Label [RFC7172].

      VRF:   Virtual Routing and Forwarding. In IP-based computer networks, Virtual
   Routing and Forwarding (VRF) is a technology that allows multiple instances of a
   routing table to co-exist within the same router at the same time.

3. Problem Statement

         -------                -------
         | GW1 |                | GW2 |
         -------                -------
            |                      |
         -------                -------
         |AGG1 |                |AGG2 |
         -------                -------
            |                      |
      -----------------------------------------------------
      |  -------------|------------------|----------------|
      |  |            |  |               |  |          |  |
    -------          -------           -------        -------
    |TOR1 |          |TOR2 |           |TOR3 |        |TOR4 |
    -------          -------           -------        -------
     |    |           |    |            |    |         |    |
   ----  ----       ----  ----        ----  ----     ----  ----
   |E |  |E |       |E |  |E |        |E |  |E |     |E |  |E |
   |S1|  |S2|       |S3|  |S4|        |S5|  |S6|     |S7|  |S8|
   ----  ----       ----  ----        ----  ----     ----  ----
                        Figure 1 A typical DC network


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   Figure 1 depicts a Data Center Network (DCN) using TRILL where edge RBridges are
   Top of Rack (ToR) switches. Centralized gateway GW1 and GW2 in figure 1 provide
   the layer 3 packet forwarding for both north-south traffic and east-west inter-
   subnet traffic between ESs.

   End stations in one IP subnet expect to send IP traffic for a different subnet to
   an IP router. In addition, there is normally a Data Label (VLAN or FGL) associated
   with each IP subnet but there is no facility in TRILL to change the Data Label for
   traffic between subnets. If two end stations of the same tenant are on two
   different subnets and need to communicate with each other, their packets are
   typically forwarded all the way to a centralized IP Layer 3 gateway to perform L3
   forwarding and, if necessary, change the Data Label. This is generally sub-optimal
   because the two end stations may be connected to the same ToR where L3 switching
   could have been performed locally. For example, in above Figure 1, assuming ES1
   (10.1.1.2 ) and ES2 (20.1.1.2) belong to different subnets of same tenant, the
   unicast IP traffic between them has to go through a centralized gateway. It can't
   be locally forwarded on TOR1. If an edge RBridge has distributed gateway
   capabilities, then it can perform optimum L2 forwarding for intra-subnet traffic
   and optimum L3 forwarding for inter-subnet traffic, delivering optimum forwarding
   for unicast packets in all important cases.

   When Fine Grained Label [RFC7172] is introduced, up to 16 million Layer 2 VN can
   be supported in a TRILL campus. To support inter-subnet traffic, up to 16 million
   Layer 3 gateway interfaces should be created on a centralized gateway if each VN
   corresponds to a subnet. It is a huge burden for the centralized gateway to
   support so many interfaces. In addition all inter-subnet traffic will go through
   the centralized gateway that may become the traffic bottleneck.

   In summary, the centralized gateway has the following issues:

      1. Sub-optimum forwarding paths for inter-subnet traffic due to the
   requirements to perform IP routing and possibly change Data Labels.

      2. Huge number of gateway interfaces, 16 million in the extreme case, need to
   be supported on the centralized gateway.

      3. Traffic bottleneck at the gateway.

   A distributed gateway on edge RBridges addresses these issues.









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4. Layer 3 Traffic Forwarding Model

                  +---------------------------------------------+
                  |                                             |
                  |      +-----------+         +-----------+    |
                  |      | Tenant n  |---------|  VRF n    |    |
                  |   +------------+ |     +------------+  |    |
                  |   |  +-----+   | |     |            |  |    |
                  |   |  | VN1 |   | |     |            |  |    |
                  |   |  +-----+   | |     |    VRF 1   |  |    |
                  |   |     ..     +-------+            |  |    |
                  |   |  +-----+   | |     |            |  |    |
                  |   |  | VNm |   | |     |            |  |    |
                  |   |  +-----+   | |     |            |  |    |
                  |   |  Tenant 1  |-+     |            |  |    |
                  |   +------------+       |            |  |    |
                  |   +------------+       +------------+       |
                  |                                             |
                  |               Edge RBridge                  |
                  +---------------------------------------------+
                  Figure 2 Edge RBridge Model as distributed GW

   In a data center network (DCN), each tenant may include one or more Layer 2
   virtual networks and, in normal cases, each tenant corresponds to one routing
   domain (RD). Normally each Layer 2 virtual network uses a different Data Label and
   corresponds to one or more subnets.

   Each Layer 2 virtual network in a TRILL campus is identified by a unique 12-bit
   VLAN ID or 24-bit Fine Grained Label [RFC7172]. Different routing domains may have
   overlapping address space but need distinct and separate routes. The end stations
   that belong to the same subnet communicate through L2 forwarding, end systems of
   the same tenant that belong to different subnets communicate through L3 forwarding.

   The above figure 2 depicts the model where there are N VRFs corresponding to N
   tenants with each tenant having up to M segments/subnets (virtual network).

5. Distributed Gateway Solution Overview

   In the TRILL distributed gateway scenario, an edge RBridge must perform Layer 2
   routing for the ESs that are on the same subnet and IP routing for the ESs that
   are on the different subnets of the same tenant.

   As the IP address space in different routing domains can overlap, VRF instances
   need to be created on each edge RBridge to isolate the IP forwarding process among
   different routing domains present on the edge RBridge. A globally unique tenant ID
   identifies each routing domain. The network operator should ensure the consistency
   of the tenant ID on each edge RBridge for each routing domain. If a routing domain


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   spreads over multiple edge RBridges, routing information for the routing domain
   should be synchronized among these edge RBridges to ensure the reachability to all
   ESs in that routing domain. The Tenant ID should be carried with the routing
   information to differentiate the routing domains.

   From the data plane perspective, all edge RBridges are connected to each other via
   one or multiple TRILL hops, however they are always a single IP hop away. When an
   ingress RBridge receives inter-subnet traffic from a local ES whose destination
   MAC is the edge RBridge's gateway MAC, that RBridge will perform Ethernet header
   termination and look up in its IP forwarding table to forward the traffic to the
   IP next hop. If the destination ES is connected to a remote edge RBridge, the
   remote RBridge will be the IP next hop for traffic forwarding. The ingress RBridge
   will perform TRILL encapsulation for such inter-subnet traffic and route it to the
   remote RBridge through the TRILL campus.

   When that remote RBridge receives the traffic, it will decapsulate the packet and
   then lookup in the RBridge's IP forwarding table to route it to the destination ES.
   Through this method, TRILL with distributed gateways provides pair-wise data
   routing for inter-subnet traffic.

5.1. Local routing information

   An ES can be locally connected to an edge RBridges through a layer 2 network or
   externally connected through a layer 3 IP network.

   If the ES is connected to an edge RBridge through a Layer 2 network, then the edge
   RBridge must act as a Layer 3 GW for the ES. The gateway interface should be
   established on the edge RBridge for the connecting ES. Because the ESs in the same
   subnet may be spread over multiple edge RBridges, each of these edge RBridges
   should establish its gateway interface for the subnet and these gateway interfaces
   on different edge RBridges share the same gateway MAC and gateway IP address.

   Before an ES starts to send inter-subnet traffic, it should acquire its gateway's
   MAC through the ARP/ND process. Local connecting edge RBridges that are supporting
   this distributed gateway feature always respond with the gateway MAC address when
   receiving ARP/ND requests for the gateway IP. Through the ARP/ND process, the edge
   RBridge can learn the IP and MAC correspondence of local ES connected to the edge
   RBridge by Layer 2 and then generate local IP routing entries for the ES in the
   corresponding routing domain.

   If an ES is located in an external IP network, the ES also can be connected to the
   TRILL campus through a TRILL edge RBridge. The TRILL edge RBridge runs a unified
   routing protocol with the external IP network for each routing domain. The edge
   RBridge learns the IP prefix corresponding to the ES through the IP routing
   protocol, then the RBridge generates local IP routing entries in the corresponding
   routing domain.



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5.2. Local routing information synchronization

   Each edge RBridge should announce its own tenant gateway MAC to the TRILL campus.
   The tenant gateway MAC is to differentiate inter-subnet Layer 3 traffic or intra-
   subnet Layer 2 traffic on an egress RBridge; the ingress RBridge will use the
   tenant gateway MAC announced by the egress RBridge as the Inner.MacDA for inter-
   subnet traffic TRILL encapsulation. All tenants on a RBridge can share the same
   tenant gateway MAC for inter-subnet traffic purposes.

   When a routing instance is created on an edge RBridge, the tenant ID, tenant Label
   (VLAN or FGL), and their correspondence should be set and globally advertised. The
   ingress RBridge uses the Label advertised by the egress RBridge as the inner VLAN
   or FGL when it performs inter-subnet traffic TRILL encapsulation. The egress
   RBridge relies on tenant Label to find the local VRF instance for the IP
   forwarding process when receiving inter-subnet traffic from the TRILL campus. (The
   role of tenant Label is akin to an MPLS VPN Label in an MPLS IP/MPLS VPN network.)
   Tenant Labels are independently allocated on each edge RBridge for each routing
   domain, an edge RBridge can pick up an access Label in a routing domain to act as
   inter-subnet Label, or the edge RBridge can use a different Label from any access
   Labels to act as tenant Label. It's implementation dependant and there is no
   restriction on this.

   When a local IP prefix is learned in a routing instance on an edge RBridge, the
   edge RBridge should advertise the IP prefix information for the routing instance
   to other edge RBridges to generate IP routing entries. A globally unique tenant ID
   also should be carried to differentiate IP prefixes between different tenants,
   because the IP address space of different tenants can overlap.

   TRILL FS-LSP [rfc7180bis] extensions can be used for IP routing information
   synchronization in each routing domain among edge RBridges. Based on the
   synchronized information from other edge RBridges, each edge RBridge generates
   remote IP routing entries in each routing domain.

   Through this solution, intra-subnet forwarding function and inter-subnet IP
   routing functions are integrated and network management and deployment will be
   simplified.

5.3. Data traffic forwarding process

   After a Layer 2 connected ES1 in VLAN-x acquires its gateway's MAC, it can start
   inter-subnet data traffic process to ES2 in VLAN-y. When the local connecting edge
   RBridge receives inter-subnet traffic from ES1, the RBridge performs Layer 2
   header termination, then, using the local VRF corresponding to VLAN-x, it performs
   the IP forwarding process in that VRF.





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   If destination ES2 is also attached to the ingress RBridge, the traffic will be
   locally forwarded to ES2 on the ingress RBridge. Compared to the centralized
   gateway solution, the forwarding path is optimal and a traffic detour is avoided.

   If ES2 is attached to a remote edge RBridge, the remote edge RBridge is IP next
   hop and the inter-subnet traffic is forwarded to the IP next hop through TRILL
   encapsulation. If there are multiple equal cost shortest path between ingress
   RBridge and egress RBridge, all these path can be used for inter-subnet traffic
   forwarding, so pair-wise load spreading can be achieved for inter-subnet traffic.

   When the remote RBridge receives the inter-subnet TRILL encapsulated traffic, the
   RBridge decapsulates the TRILL encapsulation and checks the Inner.MacDA, if that
   MAC address is the local gateway MAC corresponding to the inner Label (VLAN or
   FGL), the inner Label will be used to find the corresponding local VRF, then the
   IP forwarding process in that VRF will be performed, and the traffic will be
   locally forwarded to the destination ES2.

   In summary, through this solution, traffic detours to a central gateway are
   avoided, both inter-subnet and intra-subnet traffic can be forwarded along pair-
   wise shortest paths, and network bandwidth is conserved.

6. Distributed Layer 3 Gateway Process Example

                        ---------             ---------
                        |  RB3  |             |  RB4  |
                        ---------             ---------
                         #   *                        *
                         #   **************************
                         ###########################  *
                         #   *                     #  *
                         #   *                     #  *
                         #   *                     #  *
                        ---------              ---------
                        |  RB1  |              |  RB2  |
                        ---------              ---------
                           |                      |
                          ----                   ----
                           |E |                   |E |
                           |S1|                   |S2|
                          ----                   ----
                     Figure 3 Distributed gateway scenario

   In figure 3 above, RB1 and RB2 support the distribution gateway function, ES1
   connects to RB1, ES2 connects to RB2. ES1 and ES2 belong to Tenant1, but are in
   different subnets.

   The IP address, VLAN, and subnet information of ES1 and ES2 are as follows:


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   +----+---------+----------------+---------------+----------+
   | ES | Tenant  |   IP Address   |    Subnet     |  VLAN    |
   +----+---------+----------------+---------------+----------+
   | ES1| Tenant1 |    10.1.1.2    |  10.1.1.1/32  |   10     |
   +----+---------+----------------+---------------+----------+
   | ES2| Tenant1 |    20.1.1.2    |  20.1.1.1/32  |   20     |
   +----+---------+----------------+---------------+----------+
                           Figure 4 ES information


   The nickname, VRF, tenant VLAN, tenant gateway MAC for Tenant1 on RB1 and RB2 are
   as follows:

   +----+---------+----------+-------+--------------+--------------+
   | RB | Nickname|  Tenant  | VRF   | Tenant VLAN  |  Gateway MAC |
   +----+---------+----------+-------+--------------+--------------+
   | RB1|  nick1  |  Tenant1 | VRF1  |    100       |    MAC1      |
   +----+---------+----------+-------+--------------+--------------+
   | RB2|  nick2  |  Tenant1 | VRF2  |    100       |    MAC2      |
   +----+---------+----------+-------+--------------+--------------+
                         Figure 5 RBridge information

6.1. Control plane process

   RB1 announces the following local routing information to the TRILL campus:

      Tenant ID: 1

      Tenant gateway MAC: MAC1.

      Tenant VLAN for Tenant1: VLAN 100.

      IP prefix in Tenant1: 10.1.1.2/32.

   RB2 announces the following local routing information to TRILL campus:

      Tenant ID: 1

      Tenant gateway MAC: MAC2.

      Tenant VLAN for Tenant1: VLAN 100.

      IP prefix in Tenant1: 20.1.1.2/32.





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   Relying on the routing information from RB2, remote routing entries on RB1 are
   generated as follows:


   +--------------+-------------+--------------+----------------+
   |  Prefix/Mask | Inner.MacDA | inner VLAN   | egress nickname|
   +--------------+-------------+--------------+----------------+
   |  20.1.1.2/32 |    MAC2     |    100       |     nick2      |
   +--------------+-------------+--------------+----------------+
                  Figure 6 Tenant 1 remote routing table on RB1


   Similarly, relying on the routing information from RB1, remote routing entries on
   RB2 are generated as follows:

   +-----------+-------------+-----------+---------------+
   |Prefix/Mask| Inner.MacDA |inner VLAN |egress nickname|
   +-----------+-------------+-----------+---------------+
   |10.1.1.2/32|     MAC1    |   100     |    nick1      |
   +-----------+-------------+-----------+---------------+
                  Figure 7 Tenant 1 remote routing table on RB1



6.2. Data plane process

   Assuming ES1 sends unicast inter-subnet traffic to ES2, the traffic forwarding
   process is as follows:

   1. ES1 sends unicast inter-subnet traffic to RB1 with RB1's gateway's MAC as the
      destination MAC.

   2. Ingress RBridge (RB1) forwarding process:

   RB1 checks the destination MAC, if the destination MAC equals the local gateway
   MAC, the gateway function will terminate the Layer 2 header and perform L3
   forwarding process.

   RB1 looks up IP routing table information by destination IP and Tenant ID to get
   IP next hop information, which includes the egress RBridge's gateway MAC (MAC2),
   tenant VLAN (VLAN 100) and egress nickname (nick2). Using this information, RB1
   will perform inner Ethernet header encapsulation and TRILL encapsulation. RB1 will
   use MAC2 as the Inner.MacDA, MAC1 (RB1's own gateway MAC) as the Inner.MacSA, VLAN
   100 as the Inner.VLAN, nick2 as the egress nickname and nick1 as the ingress
   nickname.




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   RB1 looks up TRILL forwarding table by egress nickname and sends the traffic to
   the TRILL next hop as per [RFC6325]. The traffic will be sent to RB3 or RB4 as
   result of load balancing.

   Assuming the traffic is forwarded to RB3, the following occurs:

   3. Transit RBridge (RB3) forwarding process:

   RB3 looks up TRILL forwarding information by egress nickname and forwards the
   traffic to RB2 as per [RFC6325].

   4. Egress RBridge forwarding process:

   As the egress nickname is RB2's own nickname, RB2 performs TRILL decapsulation.
   Then it checks the Inner.MacDA and, because that MAC is equal to the local gateway
   MAC, performs inner Ethernet header termination. Relying on inner VLAN, RB2 finds
   the local corresponding VRF and looks up the packets destination IP address in the
   VRF's IP routing table. The traffic is then be locally forwarded to ES2.

7. TRILL Protocol Extensions

   If an edge RBridge RB1 participates in the distributed gateway function, it should
   announce its tenant gateway MAC, tenant Label and IPv4/IPv6 prefix to the TRILL
   campus through the tenant gateway MAC APPsub-TLV, tenant Label APPsub-TLV and
   IPv4/IPv6 prefix APPsub-TLV. Other edge RBridges belonging to the same routing
   domain use this information to generate IP routing entries in that routing domain.
   The ingress RBridge uses the tenant gateway MAC and tenant Label of the egress
   RBridge to perform inter-subnet traffic TRILL encapsulation when it receives
   inter-subnet traffic from a local ES. The tenant gateway MAC is used as the
   Inner.MacDA and the tenant Label is used as the Inner.Label.

   The following APPsub-TLVs MUST be included in a TRILL GENINFO TLV in FS-LSPs
   [rfc7180bis].

7.1. The tenant gateway MAC APPsub-TLV


                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |   Type                      | (2 bytes)
                   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                   |   Length                    | (2 bytes)
                   +-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+
                   |   Tenant gateway MAC        | (6 bytes)
                   +-+-+-+-+-+-+-+-+-+-+-+-+...+-+-+





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          o Type: Set to TENANT-GWMAC sub-TLV (TBD1). Two bytes, because this APPsub-
   TLV appears in an extended TLV [RFC7356].

          o Length: 6.

          o Tenant gateway MAC: The local tenant gateway MAC for inter-subnet traffic
   forwarding.



7.2. The tenant Label APPsub-TLV

              +-+-+-+-+-+-+-+-+-+-+-+-+-+
              |   Type                  | (2 bytes)
              +-+-+-+-+-+-+-+-+-+-+-+-+-+
              |   Length                | (2 bytes)
              +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              |                     Tenant ID (4 bytes)       |
              +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
              |L|Resv|     Label1     | (2 bytes)
              +-+-+-+-+-+-+-+-+-+-+-+-+
              | Resv2|     Label2     | (2 bytes)
              +-+-+-+-+-+-+-+-+-+-+-+-+


        o Type: Set to TENANT-LABEL sub-TLV (TBD2). Two bytes, because this APPsub-
   TLV appears in an extended TLV [RFC7356].

       o Length: If Label1 field is used to represent a VLAN, the value of the
   length field is 12. If Label1 and Label2 field are used to represent an FGL, the
   value of the length field is 14.

        o Tenant ID: This identifies a global tenant ID.

        o L: 1 bit. When Label1 and Label2 field are used to identify an FGL, this
   bit is set to 1. When Label1 field is used to identify a VLAN, it is set to 0.

        o Resv: 3 bits that MUST be sent as zero and ignored on receipt.

        o Label1: If the value of length field is 12, the field is to identify tenant
   VLAN ID. If the value of length field is 14, the field is to identify higher 12
   bits of tenant FGL.

        o Resv2: 4 bits that MUST be sent as zero and ignored on receipt. Only
   present if the length field is 14.




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        o Label2: This field has the lower 12 bits of tenant FGL. Only present if the
   length field is 14.



7.3. The IPv4 Prefix APPsub-TLV

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type                        | (2 bytes)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Total Length                | (2 bytes)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   |                     Tenant ID                    |(4 bytes)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   | Prefix Length(1)|(1 byte)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   |                     Prefix (1)                   |(variable)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   |     .....       |(1 byte)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   |                    .....                         |(variable)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   | Prefix Length(N)|(1 byte)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   |                     Prefix (N)                   |(variable)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+


          o Type: Set to IPV4-PREFIX sub-TLV (TBD3). Two bytes, because this APPsub-
   TLV appears in an extended TLV [RFC7356].

          o Total Length: This 2-byte unsigned integer indicates the total length of
   Tenant ID, Prefix Length and Prefix fields in octets. A value of 0 indicates that
   no IPv4 prefix is being advertised.

          o Tenant ID: This identifies a global tenant ID.

          o Prefix Length: The Prefix Length field indicates the length in bits of
   the IPv4 address prefix.  A length of zero indicates a prefix that

   matches all IPv4 addresses (with prefix, itself, of zero octets).

          o Prefix: The Prefix field contains an IPv4 address prefix, followed by
   enough trailing bits to make the end of the field fall on an octet boundary. Note
   that the value of the trailing bits is irrelevant.




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7.4. The IPv6 Prefix APPsub-TLV

   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Type                        | (2 bytes)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   Total Length                | (2 bytes)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   |                     Tenant ID                    |(4 bytes)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   | Prefix Length(1)|(1 byte)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   |                     Prefix (1)                   |(variable)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   |     .....       |(1 byte)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   |                    .....                         |(variable)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   | Prefix Length(N)|(1 byte)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+
   |                     Prefix (N)                   |(variable)
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+...-+-+-+-+-+-+-+-+


          o Type: Set to IPV6-PREFIX sub-TLV (TBD4). Two bytes, because this APPsub-
   TLV appears in an extended TLV [RFC7356].

          o Total Length: This 2-byte unsigned integer indicates the total length of
   Tenant ID, Prefix Length and Prefix fields in octets. A value of 0 indicates that
   no IPv6 prefix is being advertised.

          o Tenant ID: This identifies a global tenant ID.

          o Prefix Length: The Prefix Length field indicates the length in bits of
   the IPv6 address prefix.  A length of zero indicates a prefix that matches all
   IPv6 addresses (with prefix, itself, of zero octets).

          o Prefix: The Prefix field contains an IPv6 address prefix, followed by
   enough trailing bits to make the end of the field fall on an octet boundary. Note
   that the value of the trailing bits is irrelevant.


8. Security Considerations

   Correct configuration of the edge RBridges participating is important to assure
   that data is not delivered to the wrong tenant, which would violate security
   constrains. IS-IS security [RFC5310] can be used to secure the information
   advertised by the edge RBridges.


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   Particularly sensitive data should be encrypted end-to-end, that is, from the
   source end station to the destination end station.

   For general TRILL Security Considerations, see [RFC6325].

9. IANA Considerations

   IANA is requested to assign four APPsub-TLV type numbers less than 255 under the
   TRILL GENINFO TLV [RFC7357] as follows:

   Type    Name               References
   ----   ----------------   ------------

   TBD1   TENANT-GWMAC       [this document]
   TBD2   TENANT-LABEL       [this document]
   TBD3   IPV4-PREFIX        [this document]
   TBD4   IPV6-PREFIX        [this document]

10. Normative References

   [1]   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997.

   [2]   [RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S.,and A. Ghanwani,
         "Routing Bridges (RBridges): Base Protocol Specification", RFC 6325, July
         2011.

   [3]   [RFC7172] Eastlake, D., M. Zhang, P. Agarwal, R. Perlman, D. Dutt, "TRILL
         (Transparent Interconnection of Lots of Links): Fine-Grained Labeling",
         RFC7172, May 2014.

   [4]   [RFC7176] - Eastlake, D., T. Senevirathne, A. Ghanwani, D. Dutt and A.
         Banerjee" Transparent Interconnection of Lots of Links (TRILL) Use of IS-
         IS", RFC7176, May 2014.

   [5]   [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.



11. Informative References

   [1]   [RFC5310] - Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., and M.
         Fanto, "IS-IS Generic Cryptographic Authentication", RFC 5310, February
         2009.


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12. Acknowledgments

   The authors wish to acknowledge the important contributions of

   Guangrui Wu, Zhenbin Li, Zhibo Hu.









































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   Authors' Addresses














































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   Weiguo Hao
   Huawei Technologies
   101 Software Avenue,
   Nanjing 210012
   China
   Phone: +86-25-56623144
   Email: haoweiguo@huawei.com


   Yizhou Li
   Huawei Technologies
   101 Software Avenue,
   Nanjing 210012
   China
   Phone: +86-25-56625375
   Email: liyizhou@huawei.com


   Donald E. Eastlake
   Huawei Technologies
   155 Beaver Street
   Milford, MA 01757 USA

   Phone: +1-508-333-2270
   EMail: d3e3e3@gmail.com


   Liang Xia(Frank)
   Huawei Technologies
   101 Software Avenue,
   Nanjing 210012
   China
   Phone: +86-25-56624539
   Email: frank.xialiang@huawei.com


   Andrew Qu
   MediaTec
   Email: laodulaodu@gmail.com


   Muhammad Durrani
   Brocade
   130 Holger Way
   San Jose, CA 95134
   EMail: mdurrani@brocade.com



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   Ponkarthick Sivamurugan
   Address: IP Infusion,
   RMZ Centennial
   Mahadevapura Post
   Bangalore - 560048
   EMail: Ponkarthick.sivamurugan@ipinfusion.com









































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