Internet DRAFT - draft-aldrin-trill-data-center-interconnect



TRILL Working Group                                           Sam Aldrin
INTERNET-DRAFT                                           Donald Eastlake
Intended Status: Proposed Standard                   Huawei Technologies
                                                      Tissa Senevirathne
                                                           Ayan Banerjee
                                                        Santiago Alvarez
Expires: September 3, 2012                                 March 2, 2012

                    TRILL Data Center Interconnect 


   This document presents a solution suite for TRILL data center sites
   to be connected over WAN networks. TRILL protocol is primarily
   designed to work within intra-data centers. Connecting different
   sites over WAN using overlay tunnel protocols is the primary method
   employed at present. Though this presents a simple mechanism to
   extend the LAN sites to be interconnected, it also brings in the
   problem of scalability for TRILL nicknames exchanged between sites,
   latency, duplication of traffic etc. This draft proposes a way to
   extend the TRILL sites without having to reveal the data of the LAN
   like customer MAC's or provide MAC's over the WAN, but to establish
   connections between various sites by extending routing protocol to
   exchange minimal information, thus reducing the information flow to
   the required sites only. Document also proposes BGP routing protocol
   extensions as an example to establish paths and information about the
   essential RBridges nicknames, over WAN networks like MPLS. 

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 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."


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   described in the Simplified BSD License.

Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Solution overview  . . . . . . . . . . . . . . . . . . . . . .  5
     2.1  Site inter-connection . . . . . . . . . . . . . . . . . . .  5
     2.2 Requirements overview  . . . . . . . . . . . . . . . . . . .  6
     2.2  TRILL campus extension  . . . . . . . . . . . . . . . . . .  6
     2.3  TRILL nickname exhaustion . . . . . . . . . . . . . . . . .  6
   3. Solution comparison analysis  . . . . . . . . . . . . . . . . .  7
     3.1  TRILL campus extension  . . . . . . . . . . . . . . . . . .  7
     3.2  TRILL campus interconnection with E-VPN and PBB-EVPN  . . .  8
     3.3  TRILL campus interconnection over VPN's . . . . . . . . . .  8
   4. Operational Overview  . . . . . . . . . . . . . . . . . . . . .  9
     4.1 Campus and Backbone Areas  . . . . . . . . . . . . . . . . .  9
     4.2 Unicast forwarding . . . . . . . . . . . . . . . . . . . . . 10
     4.3 Multicast Forwarding . . . . . . . . . . . . . . . . . . . . 10
     4.4 MAC learning . . . . . . . . . . . . . . . . . . . . . . . . 12
     4.5 TRILL nickname aggregation . . . . . . . . . . . . . . . . . 12
     4.6 Route advertisement with BGP . . . . . . . . . . . . . . . . 12
   5. TRILL campus inter-connectivity . . . . . . . . . . . . . . . . 13
     5.1 Route advertisement  . . . . . . . . . . . . . . . . . . . . 13
     5.2 Inter-site nickname exchange . . . . . . . . . . . . . . . . 14
     5.3 Border RBridge capability exchange . . . . . . . . . . . . . 14

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     5.4 TRILL adjacency resolution . . . . . . . . . . . . . . . . . 14
     5.5 Forwarding of data frames  . . . . . . . . . . . . . . . . . 15
   6. Proposed additions and extensions . . . . . . . . . . . . . . . 15
     6.1 BGP extension  . . . . . . . . . . . . . . . . . . . . . . . 15
     6.2 Border RBridge capability TLV  . . . . . . . . . . . . . . . 16
     6.3 TRILL nickname aggregation sub-TLV . . . . . . . . . . . . . 16
   7  Security Considerations . . . . . . . . . . . . . . . . . . . . 17
   8  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 17
   9  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     9.1  Normative References  . . . . . . . . . . . . . . . . . . . 17
     9.2  Informative References  . . . . . . . . . . . . . . . . . . 17
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17


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1  Introduction

   TRILL protocol is primarily designed as an intra-datacenter protocol
   by leveraging the routing functionality to interconnect bridges.
   Traditional Ethernet networks provided a single path for forwarding
   the traffic, which is usually derived using protocols like Spanning
   Tree. TRILL provided a way to utilize multiple links for forwarding,
   thus utilizing the resources effectively. Even though TRILL is new
   protocol, it seamlessly integrates with legacy bridging networks
   without having to forklift upgrade of all the bridges to support
   TRILL. By not having to learn the MAC addresses of end stations by
   intermediate devices, provided a powerful way to interconnect bridges
   within a datacenter and maximizing the resource usage and providing
   multipath usage option.

   TRILL enabled network creates efficiency by having reduced forwarding
   table size. By doing TRILL nickname based forwarding created a layer
   of abstraction and much easier to implement the protocol. This
   enabled to address the scalability of a L2 domain, where thousands of
   RBridges could exist to meet the needs of a datacenter. By leveraging
   IS-IS protocol, the information exchange and leveraging the path
   computation technology brought forth a new paradigm into bridging
   technology. TRILL Base Protocol Specification [RFC6325] specifies a
   tree based paradigm to forward broadcast and multicast traffic as
   well as unknown unicast traffic.

   Even though the TRILL is enabled within a datacenter and is not
   primarily designed to work over WAN, there is a need to interconnect
   various TRILL data sites. The same datacenter provider could be
   having multiple TRILL sites and these TRILL enabled datacenter sites
   could run independently or could share resources in order to cater to
   the needs of customers. As such, there exist few proposals based on
   overlay technologies which interconnect these sites but those
   solutions require MAC learning at the edge RBridges and stripping of
   TRILL nickname on the frame. Another option is to interconnect these
   TRILL sites using Pseudowires and making a huge TRILL site. This is
   useful option but the downside of this is when provider would like to
   maintain independent sites and exchange only the required data to be
   shared across sites, it becomes complicated to maintain the networks.

   This draft solves these core problems of interconnection, site
   independence, dynamic information exchange and setting up of
   connections over WAN, leveraging existing WAN technologies like MPLS,
   etc. Though the primary goal is effective interconnection, there are
   various efficient schemes, which could enable seamless TRILL network
   deployments, are also be presented. Solution covers both unicast and
   multicast data traffic.


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1.1  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Solution overview

   This section provides the high-level overview of the solution to the
   problems in various scenarios. More detailed representation of the
   solution is covered in the later sections of the draft.

   TRILL site or TRILL campus uses IS-IS to setup the RBridge
   interconnection. A RBridge knows how to reach another RBridge within
   the campus. When two TRILL campuses are interconnected, one could
   visualize it in two different perspectives. First one is a merger of
   two TRILL campuses into one. This requires each RBridge to know about
   the other and the IS-IS should be able to compute the shortest paths
   from one to another. The downside of this model is that information
   exchange explosion and the size of IS-IS db and number of PDU's being
   exchanged could increase exponentially.

   The second perspective is to have these two TRILL campuses being
   interconnected over a WAN, but their functioning nature is
   independent to each other. The two campuses exchanges only the
   required information between border RBridges of the campuses. This
   will be more optimal and leads to interconnecting multiple campuses
   without having to redesign the whole network to ensure uniqueness and
   identity of RBridges.

   Solution being proposed is an option of maintaining site independency
   with a simplified solution and modeled around the existing and proven
   technologies. Some of the enhancements were already proposed in other
   drafts like multilevel TRILL [TISSA-MLEVEL] and the solution
   leverages by extending those definitions as necessary. The solution
   addresses the following areas described in the following sections

2.1  Site inter-connection

   Each TRILL campus is considered as an independent site or an L1 IS-IS
   domain. These TRILL campus sites are interconnected over WAN. Each
   area will have an appointed border RBridges. These RBridges exchange
   the information of other border RBridges of different TRILL campus
   sites to establish connection with each other. In order to exchange
   the information, the route has to be established. Extension of BGP
   protocol is done to exchange the border RBridges information and
   establish a route or vpn/mvpn connection between each of the border

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   RBridges. More details of the extension are detailed in the below
   section. These sites are interconnected either over IP or MPLS. As
   MPLS is a mature WAN technology, this draft references the solution
   based on MPLS. This does not preclude that other technologies could
   not be used.

2.2 Requirements overview

   There are various requirements necessary to be met in order to
   provide a seamless TRILL inter-connectivity across campuses and
   datacenter. Some of the important requirements are as follows

   o Extend TRILL technology over interconnect

   o Ability to provide the same fast convergence for mobility as it
   does in intra-TRILL campus

   o Ability to work with various WAN technologies

   o Option for dynamic establishment of connectivity across sites

   o Minimal changes to protocols and definitions

   o Backward compatible to existing networks and their functions.

2.2  TRILL campus extension

   By interconnecting TRILL campus sites over WAN, one could extend the
   L1 area, but that would cause other issues as detailed in the earlier
   section. With this solution, all of the TRILL nicknames of one campus
   are not exchanged with other campuses. Instead, there will be
   RBridges which gets appointed, so only those specific nicknames are
   exchanged with others. Also one could create another hierarchical
   model like VPN, where participating appointed RBridges for that VPN
   could be exchanged with other campuses belonging to that VPN.
   Appointed or designated RBridges information will be exchanged with
   other campus site using the Affinity TLV extension. Detailed
   description on how to create and the usage are detailed in multileve
   draft [TISSA-MLEVEL]. When each campus site creates this information
   and exchanged with other campus sites of the network or VPN, this
   could be used for two purposes, 1. A VPN specific WAN paths could be
   created between campus sites. 2. The data distribution could be
   optimized without having the need to be broadcast the data frames
   from one campus into every campus site.

2.3  TRILL nickname exhaustion


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   Though this draft is not meant to provide solution for TRILL nickname
   exhaustion, it enables provider to deal with the problem effectively
   and not having to re-design the network, every time a new campus is
   interconnected. The proposed solution has RBridges which are not
   required to be exposed outside of the campus and there are other
   RBridges which are also known as border RBridges. These border
   RBridges nicknames are unique globally. Rest of the RBridges
   nicknames are significant locally, that includes the appointed
   RBridges nicknames for a VPN. When a frame has to be forwarded to an
   RBridge which resides in another campus, the originating RBridge only
   knows how to get to the borderRBridge. This border RBridge should
   have the list of RBridges of other campus sites and thus could select
   the appropriate MPLS LSP or MVPN or PW and encapsulate the TRILL
   frame with the label header and forward over that. More details are
   covered in the unicast and multicast sections of the detailed

3. Solution comparison analysis

   As eluded to in the earlier sections, there are various methods on
   interconnecting different TRILL campus sites. Before going into the
   details of proposed solution a close examination of some of the
   proposed solutions, provides better perspective of this solution.

3.1  TRILL campus extension

   In this model TRILL campuses are connected over WAN using
   technologies like PW. This is the most simplest way of
   interconnecting the sites. When campuses are interconnected, the
   TRILL campus will get expanded and each RBridge could reach each
   other. The main criteria for this will be to maintain unique nickname
   for RBridges.

           --------------       ------------       --------------       
          |              |     |            |     |              |      
          |TRILL Campus  |     |  WAN       |     | TRILL Campus |      
          |              |     |            |     |              |      
          |             BRB1===|            |====BRB2            |      
          RB1            |     |            |     |              RB2    
          |              |     |            |     |              |      
          |              |     |            |     |              |      
          --------------       ------------       --------------

   As shown in the figure above, two TRILL campuses are interconnected
   over WAN. Border RBridges establish connection over WAN using PW or
   other WAN technologies. All the nicknames within each campus sites
   have to be unique. The WAN in this case is transparent to the TRILL

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   campuses and the path computation doesn't involve WAN component,
   instead it will be like one TRILL campus. When RB1 originates a TRILL
   frame destined to RB2, it traverses over BRB1 and BRB2 and reaches

   This solution is workable when the campuses are small and do NOT need
   to change or requires interconnecting more TRILL campuses. The other
   downside for this model is, when two campuses are interconnected and
   there is overlap of nicknames, the network has to be re-designed to
   eliminate the duplicate nicknames and make each RBrige to have a
   unique nickname.

3.2  TRILL campus interconnection with E-VPN and PBB-EVPN

   TRILL campuses could be extended over WAN using E-VPN and PBB-EVPN. 

                      BEB   +--------------+  BEB                       
                      ||    |              |  ||                        
                      \/    |              |  \/                        
          +----+ AC1 +----+ |              | +----+   +----+            
          | CE1|-----|    | |              | |    |---| CE2|            
          +----+\    |MES1| |   IP/MPLS    | |MES3|   +----+            
                 \   +----+ |   Network    | +----+                     
                  \         |              |                            
                AC2\ +----+ |              |                            
                    \|    | |              |                            
                     |MES2| |              |                            
                     +----+ |              |                            
                       /\   +--------------+                            

   The [PBB-EVPN] draft proposes interconnection details on how two
   TRILL campuses could be interconnected using the E-VPN technology. In
   this a new BGP route is advertised for reachability of TRILL
   RBridges. This technique leverages the PBB technology and also
   enables to retain TRILL header but is recommended to avoid
   transmitting TRILL encapsulated frames over the WAN links. The
   primary downside of this method is the requirement for edge RBridges
   to learn MAC Addresses in order to resolve the adjacency.

3.3  TRILL campus interconnection over VPN's

   In this method, TRILL campus sites could be interconnected over


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           --------------       ------------       --------------       
          |              |     |            |     |              |      
          |TRILL Campus  |     |  WAN       |     | TRILL Campus |      
          |              |     |            |     |              |      
          |             BRB1===|            |====BRB2            |      
          RB1            |     |            |     |              RB2    
          |              |     |            |     |              |      
          |              |     |            |     |              |      
           --------------       ------------       --------------       
                              |            |                            
                              |TRILL Campus|                            
                              |            |                            
                              |            |                            
                              |            |                            
                              |            |                            
                              |            |                            

   These VPN's could be established statically or dynamically. In order
   to establish dynamically, the border RBridges needs to exchange
   information of the nicknames and connect different sites. The
   hierarchical model like H-VPLS could be established as well. [PBB-
   EVPN] draft provides some details on how to achieve this, but still
   requires border RBridges to exchange MAC information and resolution
   for L2 adjacency. One other option is much similar to the first model
   where campuses exchange TRILL nicknames between campuses over VPN's.
   Though this model groups different sites according to the way VPN's
   are configured, avoiding flooding of TRILL nicknames or site
   independency cannot be achieved.

4. Operational Overview

4.1 Campus and Backbone Areas

   Each TRILL campus will be assigned a border RBridge. This is
   identified using the 'Attached' bit in the IS-IS PDU. The border
   RBridge has list of the RBridges of each campus site. These list of
   bridges are exchanged using the TRILL nickname aggregation sub-TLV.
   Details of the sub-TLV are detailed in the below section.

   Every TRILL campus campus need not exchange all the RBridge nicknames
   with other campuses. Let us take the scenario of campus A to be
   interconnected with campus B. In campus A, there are RBridges

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   RB1...RB10, which are interconnected in L1. These nicknames are not
   tunneled or exchanged with other L1 campus sites. Similarly campus B
   has RB11...RB20 and need not be distinct from campus A RBridge
   nicknames.  So, if a new campus is connected to the domain, there is
   no need for the network to redesigned or restructured.

   The RBridges at each campus advertise the information to other campus
   to establish a route/MPLS LSP between campus sites. A new BGP
   extension as defined below is sent out. This reachability TLV is
   received by other border RBridges and establish the MPLS LSP between

   The border RBridges will have the complete information of its campus
   RBridges. Not all of the RBridges nicknames need not be advertised
   globally. So, the globally exchanged nicknames of RBridges should be
   unique across campuses. Depending on the policy established, these
   Border RBridges will exchange the TRILL information with other campus
   border Bridges, over the routes/MPLS LSP established between
   different campuses. In IS-IS domain the equivalent of this is the L2
   backbone area, which in this case, is established over WAN.

4.2 Unicast forwarding

   If the destination TRILL nickname is not known, the originating or
   transit RBridges forwards it to border RBridge. As the border RBridge
   has all the nicknames of each campus, it forwards the frame to the
   right campus border RBridge, which in turn could forward within its
   campus as per base protocol specification [RFC6325]. In the case
   where the destination is unknown, the frame is flooded to each
   campus. Using the MAC learning procedures, the associated RBridge
   will be learnt for the subsequent frames to be forwarded as unicast,
   instead of flooding. Flooding into various campuses or TRILL data
   sites happen only if the the frame is of global ID based on VLAN

4.3 Multicast Forwarding

   Whether the traffic scope is local or global across campuses is
   identified by VLAN or port or fine-grain label. If the traffic is to
   be forwarded within campus, it is done using the local tree. But if
   the forwarding has to be done globally, it needs to use the global
   tree. When the frame has global context, it will be flooded into
   other TRILL sites as well. 

   In MPLS the multicast networks are established within the core
   networks. In the case of RBridges, which are part of the customer
   networks and do not participate in the service provider networks and
   their topologies, the multicast tree could be built using IP

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   multicast or leverage MVPN services offered by the service provider.
   The global trees are established between border RBridges with the
   help of information exchanges between border RBridges. As the IS-IS
   is limited to individual campus sites, the information for the
   backbone tree over WAN has to be exchanged between border RBridges
   either as a IP multicast PIM message or specific TLV indented for
   other campus border RBridges. More details on this will be added in
   the later versions of the draft.

           --------------       ------------       --------------       
          |              |     |            |     |              |      
          |TRILL Campus1 |     |  WAN       |     | TRILL Campus2|      
          |              |     |            |     |              |      
          |             BRB1===|            |====BRB2            |      
          RB1            |     |            |     |              RB2    
          |              |     |            |     |              |      
          |              |     |            |     |              |      
           --------------       ------------       --------------       
                              |            |                            
                              |TRILL Campus|                            
                              |    3       |                            
                              |            |                            
                              |            |                            
                              |            |                            
                              |            |                            

   In the above figure when the multicast frame has to be sent from
   campus 1 to campus 2 and 3, the frame arrives at border RBridge BRB1.
   With the default global tree between border RBridges of different
   campuses, the forwarding is setup to egress the frame or replicated
   over MPLS LSP's to all other campus sites. If the frame is destined
   for non-default global tree, the appropriate MPLS LSP(s) are
   identified and the frame is forwarded accordingly.

   Once the frame is reached on the border router of the campuses, the
   frame is locally multicast forwarded. The same technique as employed
   in the multilevel draft [TISSA-MLEVEL] is used here as well.

   If mVPN services are deployed interconnecting campus sites, the
   multicast tree is built over these services based on the customer


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4.4 MAC learning

   When a frame is to be forwarded from customer MAC A to customer MAC
   B, the frame is set as unknown unicast frame over TRILL networks. If
   the MAC A and MAC B are connected over WAN, the frame is transmitted
   over WAN to the other campus. When the frame is reached at the
   RBridge connecting to MAC B, it will learn about the originator
   RBridge for MAC A. While responding, the egress RBridge know the
   originating RBridge, it will unicast the frame to the originator.

4.5 TRILL nickname aggregation

   Nicknames are allocated or assigned to RBridges in a given campuses
   using various methods. It could be OSS, CLI or could be a dynamic
   control protocol which configures the nicknames. As the nicknames are
   confined to each L1 area, the nickname management, when sites are
   connected over WAN, it is essential to optimize the name allocation
   in order to use the name space effectively. Name allocation is not in
   the scope of this draft. If there is a necessity, the topic could be
   considered in the later revisions of the draft. For this version we
   do recommend some of the optimization techniques for nickname
   allocation defined in the multilevel draft [TISSA-MLEVEL].

   Each border RBridges needs to exchange the nicknames of each campuses
   with other border RBridges. As the border RBridges are connected over
   various types of WAN networks, mandating enhancement to a specific
   protocol is deemed not the right approach. As the information
   exchange has to be done, certain characteristics for the data
   exchange have to be met.

   o The amount of data exchange has to be minimal and optimized.

   o the information exchange has to be quick.

   o Conflicts and duplicate information flow has to be avoided

   This draft proposes a generic TLV, which is to be exchanged between
   border RBridges. If the nickname allocation is done in terms of
   ranges, the same could be exchanged between border RBridges,
   seamlessly. As the TLV has to be terminated at the border RBridges,
   it is better suited to be sent as a unicast message to the
   neighboring border RBridge. This could be sent as an IP message with
   TRILL header containing the target border RBridge. More details on
   how to encapsulate and process the frame should be in the later
   versions of the draft.

4.6 Route advertisement with BGP


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   BGP route advertisement is to connect border RBridges. As described
   in earlier sections, each campus site exchanges the TRILL nicknames
   with other campuses. These nicknames are not leaked in to the campus
   but will be maintained at the border RBridges. The connectivity
   between these border RBridges is similar to L2 backbone of IS-IS but
   in this case it is over WAN and IS-IS is absent.

   This draft, unlike some other drafts, do not propose to de-capsulate
   the TRILL frame to learn the MAC addresses. Instead, it propose to
   use nicknames themselves to be exchanged between sites. 

   A new BGP route advertisement is defined to advertise the border
   RBridge nickname with the other border RBridges in different
   campuses. This advertisement will let other campuses know its MPLS
   label, its nickname, IP address etc. Once the route is established,
   further information of campus nicknames etc could be exchanges to
   establish the inter-connectivity of the TRILL campuses

5. TRILL campus inter-connectivity

   The primary reason to interconnect TRILL campuses is to maintain
   geographically distant, segmented sites and customer specific
   segregation possible by interconnecting and not having to redo the
   network and campus redesign for every change and need. With customers
   being mobile or services offered by service providers could be re-
   located depending on the time-zones and resource availability,
   restricting to a specific site is a thing of the past. 

   These constraints brought forth the need to have different sites
   interconnected over the WAN, be it MPLS or VPLS or IP and to provide
   the services on demand to meet the needs of customers and their data
   center needs. As TRILL has proven to be an effective protocol by
   bringing routing technologies into bridges or L2 forwarding, the
   short coming of TRILL interconnect is the immediate need. As eluded
   to in the earlier sections on different kinds of solutions, meeting
   all the needs of the TRILL DCI as laid out in the requirements
   section, is the primary goal of this draft.

5.1 Route advertisement

   Border RBridges only participate in interconnecting various TRILL
   campuses. These border RBridges are elected or identified as
   described in the earlier section i.e. using IS-IS protocol
   advertisement. These border RBridges, when required to interconnect
   with other campuses, advertise the route to other site border
   RBridges using the BGP enhancement. Upon receipt of the route
   advertisement, the MPLS LSP or IP path or Pseudowire is established
   between RBridges and they could communicate with each other and

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   exchange other information.

   If L2 connectivity is to be used with protocols like VPLS, a similar
   method could be employed, where the PWE3 could be established between
   border RBridges. More details to be added in the later versions of
   the draft.

5.2 Inter-site nickname exchange

   There are three types of nicknames which are exchanged between border

   o Nickname of border RBridges

   o Nicknames of RBridges for each campus

   o Nicknames of RBridges which are part of a specific customer VLAN or

   The nickname aggregation TLV is used as payload to be exchanged
   between border RBridges. This information is used to establish inter-
   connectivity between TRILL sites per customer VLAN or default global

5.3 Border RBridge capability exchange

   An additional capability TLV is defined to exchange info on what each
   of the border RBridge is capable of. This is very essential for
   forward and backward capability . Capability information not only
   indicates the capability version but could also force the
   interconnection to be restricted as per the policy set by the
   customer. Some of the capability advertisements are as follows.

   o Version.

   o default nick name resolution

   o connect more campuses

   o active-active link support

   o Ability to support multicast forwarding

5.4 TRILL adjacency resolution

   When a frame is to be forwarded from one campus to another, the
   adjacency resolution has to be done on the border RBridge. When TRILL
   nicknames are advertised from one border RBridge to another, the

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   border RBridge keeps the database of all the nicknames. The MPLS
   LSP's between each RBridges are established by the route
   advertisements. VPN specific services could be established based on
   the customer VLAN ID's and also the exchange of nicknames per VPN
   between border RBridges. 

   Once the frame is received on the border RBridge, it will look in the
   forwarding table to identify the next hop. The adjacency information
   could indicate an MPLS LSP with a specific label encapsulation. For
   VPN, there will be additional VPN label in the label stack. The TRILL
   frame is encapsulated, without removing the TRILL header and is
   forwarded over the MPLS LSP.

5.5 Forwarding of data frames

   The TRILL frames are forwarded as per the base protocol [RFC6325]
   within a campus site. The forwarding of the frames from TRILL campus
   to campus will be over MPLS LSP's or IP or whichever WAN connection
   is established between border RBridges. The encapsulation of the
   Frame with WAN header is based on the adjacency resolution made in
   the forwarding on the border RBridge.

6. Proposed additions and extensions

   There are certain extensions being proposed in this draft to
   interconnect TRILL campuses or datacenters. These include new
   additions to routing and also new TLV's to exchange information
   between border RBridges. There are few references to the extensions
   proposed in other drafts which are used in this draft as well.

6.1 BGP extension

   A new BGP route advertisement is done to exchange and establish
   route/MPLS lsp between border RBridges.

      |RD (8 octets)                          |                         
      |Originating RBridge MAC address        |                         
      |Originating RBridge IP address(v4/v6)  |                         
      | Nickname Length (1 octet)             |                         
      | RBridge Nickname (2 octets)           |                         
      | MPLS Label (n * 3 octets)             |                         

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6.2 Border RBridge capability TLV

   This TLV as defined in earlier section, defines the capability of a
   border RBridge, to be exchanged with other border RBridges for
   seamless inter-working across campus sites.

       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1  
      |      Type = <TBD>             |          Length = 8           | 
      |     Version                   |  Flags                        | 
      |                          Flags                                | 

   Definition of flag bits will be identified and defined later.

6.3 TRILL nickname aggregation sub-TLV

   The nickname aggregation TLV defined in multilevel draft [TISSA-
   MLEVEL] is used in advertising the nicknames into other border
   Routers. Some new additions or changes will be proposed in later
   versions of the draft.


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7  Security Considerations

   <Security considerations text>

8  IANA Considerations

   <IANA considerations text>

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.

   [RFC2234]  Crocker, D., Ed., and P. Overell, "Augmented BNF for
              Syntax Specifications: ABNF", RFC 2234, November 1997.

   [RFC4971]  Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,
              "Intermediate System to Intermediate System (IS-IS)
              Extensions for Advertising Router Information", RFC 4971,
              July 2007.

   [RFC6325] Perlman, R.,, "Routing Bridges (RBridges): Base
              Protocol Specification", RFC 6325, July 2011.

   [trillcmt]Senevirathne, T.,, "Coordinated Multicast Trees
              (CMT)for TRILL", Work in Progress, January 2012.

9.2  Informative References

   [RFC6326] Eastlake, D,, "Transparent Interconnection of Lots of
              Links (TRILL) Use of IS-IS", RFC 6326, July 2011.

   [rfc6326bis] Eastlake, D,, "Transparent Interconnection of Lots
              of Links (TRILL) Use of IS-IS", Work in Progress, draft-
              eastlake-isis-rfc6326bis-04.txt, January 2012.

   [TISSA-MLEVEL] Senevirathne, "RBridges: Multilevel TRILL", Work in
              Progress, draft-tissa-trill-multilevel-00.txt, February

Authors' Addresses


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      Sam Aldrin
      Huawei Technologies
      2330 Central Express Way
      Santa Clara, CA 95951


      Tissa Senevirathne
      CISCO Systems
      375 East Tasman Drive
      San Jose CA 95134

      Phone: 408-853-2291

      Ayan Banerjee
      CISCO Systems
      425 East Tasman Drive
      San Jose CA 95134

      Phone: 408-527-0539

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

      Phone: +1-508-333-2270

      Santiago Alvarez
      CISCO systems


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