IDR Working Group W,. Hao
Internet-Draft D. Eastlake
Intended status: Standards Track S. Hares
Expires: September 21, 2016 Huawei Technologies
B. Pithawala
IP Infusion
M. Durrani
Cisco Systems
Y. Li
Huawei Technologies
March 20, 2016

Distribution of TRILL Link-State using BGP


This draft describes a TRILL link state and MAC address reachability information distribution mechanism using a BGP LS extension. External components such as an SDN Controller can use the information for topology visibility, troubleshooting, network automation, etc.

Status of This Memo

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This Internet-Draft will expire on September 21, 2016.

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Table of Contents

1. Introduction

BGP has been extended to distribute IGP link-state and traffic engineering information to some external components [RFC7752] such as the PCE and ALTO servers. The information can be used by these external components to compute a MPLS-TE path across IGP areas, visualize and abstract network topology, and the like.

TRILL (Transparent Interconnection of Lots of Links) protocol [RFC6325] 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).

The TRILL protocol has been deployed in many data center networks. Data center automation is a vital step to increase the speed and agility of business. An SDN controller as an external component normally can be used to provide centralized control and automation for the data center network. Making a holistic view of whole network topology available to the SDN controller is an important part for data center network automation and troubleshooting.

                           |     SDN     |
                   --------|  Controller |--------
                   |       +-------------+       |
                   |                             |
                  + +                           + +
                   +        +-----------+        +
                            |           |
               +--------+   |IP Network |   +--------+
               |        | +----+     +----+ |        |
   +---+ +---+ |        | |    |     |    | |        | +---+ +---+
   |ES1|-|RB1|-| Area 1 |-|BRB1|     |BRB2|-| Area 2 |-|RB2|-|ES2|
   +---+ +---+ |        | +----+     +----+ |        | +---+ +---+
               |        |   |           |   |        |
               +--------+   +-----------+   +--------+

         |<----TRILL ------>|<IP tunnel>|<-----TRILL ----->|

                       Figure 1: TRILL interconnection

In Data Center interconnection scenario illustrated in figure 1, a single SDN Controller or network management system (NMS) can be used for end-to-end network management. End-to-end topology visibility on the SDN controller or NMS is very useful for whole network automation and troubleshooting. BGP LS can be used by the external SDN controller to collect multiple TRILL domain's link-state.

If ESADI (End Station Address Distribution Information) protocol [RFC7357] is used for control plane MAC learning in each data center, BGP LS also can be used for MAC address reachability information synchronization across multiple TRILL domains. End-to-end unicast forwarding paths can be calculated based on the synchronized information.

This document describes the detailed BGP LS extension mechanisms for TRILL link state and MAC address reachability information distribution.

2. Conventions used in this document

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]

BGP - Border Gateway Protocol

BGP-LS - BGP Link-State

Data label - VLAN or FGL (Fine Grained Label) [RFC7172]

IS - Intermediate System (for this document, all relevant intermediate systems are RBridges).

NLRI - Network Layer Reachability Information

SDN - Software Defined Networking

RBridge - A device implementing the TRILL protocol

TRILL - Transparent Interconnection of Lots of Links

3. Carrying Trill Link-State Information in BGP

In [RFC7752], four NLRI types are defined as follows: Node NLRI, Link NLRI, IPv4 Topology Prefix NLRI and IPv6 Topology Prefix NLRI. For TRILL link-state distribution, the Node NLRI and Link NLRI are extended to carry layer 3 gateway role and link MTU information. TRILL specific attributes are carried using opaque Node Attribute TLVs, such as nickname, distribution tree number and identifiers, interested VLANs/Fine Grained Label, and multicast group address, and etc.

To differentiate TRILL protocol from layer 3 IGP protocol, a new TRILL Protocol-ID is defined.

   | Protocol-ID | NLRI information source protocol |
   | 1           | IS-IS Level 1                    |
   | 2           | IS-IS Level 2                    |
   | 3           | OSPFv2                           |
   | 4           | Direct                           |
   | 5           | Static configuration             |
   | 6           | OSPFv3                           |
   | TBD         | TRILL                            |
           Table 1: Protocol Identifiers

ESADI (End Station Address Distribution Information) protocol [RFC7357] is a per data label control plane MAC learning solution. MAC address reachability information is carried in ESADI packets. Compared with data plane MAC learning solution, ESADI protocol has security and fast update advantage that are pointed out in [RFC7357].

For an RBridge that is announcing participation in ESADI, the RBridge can distribute MAC address reachability information to external components using BGP. A new NLRI type of ''MAC Reachability NLRI'' is requested for the MAC address reachability distribution.

   | Type | NLRI Type                 |
   | 1    | Node NLRI                 |
   | 2    | Link NLRI                 |
   | 3    | IPv4 Topology Prefix NLRI |
   | 4    | IPv6 Topology Prefix NLRI |
   | TBD  | MAC Reachability NLRI     |
           Table 2: NLRI Types

The MAC Reachability NLRI uses the format as shown in the following figure.

      0                   1                   2                   3
   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
   |  Protocol-ID  |
   |  Identifier                                                   |
   |  (64 bits)                                                    |
   // Local Node Descriptor (variable) //
   // MAC Address Descriptors (variable) //
              Figure 2: The MAC Reachability NLRI format

3.1. Node Descriptors

The Node Descriptor Sub-TLV types include Autonomous System and BGP- LS Identifier, iS-IS Area-ID and IGP Router-ID. TRILL uses a fixed zero Area Address as specified in [RFC6325], Section 4.2.3. This is encoded in a 4-byte Area Address TLV (TLV #1) as follows:

      |   0x01, Area Address Type     |   (1 byte)
      |   0x02, Length of Value       |   (1 byte)
      |   0x01, Length of Address     |   (1 byte)
      |   0x00, zero Area Address     |   (1 byte)
         Figure 3: Area Address TLV

3.1.1. IGP Router-ID

Similar to layer 3 IS-IS, TRILL protocol uses 7-octet "IS-IS ID" as the identity of an RBridge or a pseudonode, IGP Router ID sub-TLV in Node Descriptor TLVs contains the 7-octet "IS-IS ID". In TRILL network, each RBridge has a unique 48-bit (6-octet) IS-IS System ID. This ID may be derived from any of the RBridge's unique MAC addresses or configured. A pseudonode is assigned a 7-octet ID by the DRB (Designated RBridge) that created it, the DRB is similar to the "Designated Intermediate System" (DIS) corresponding to a LAN.

3.2. MAC Address Descriptors

The ''MAC Address Descriptor'' field is a set of Type/Length/Value (TLV) triplets. ''MAC Address Descriptor'' TLVs uniquely identify an MAC address reachable by a Node. The following attributes TLVs are defined:

   | TLV Code     | Description           | Length   | Value defined   |
   | Point        |                       |          | in:             |
   |   1          | MAC-Reachability      | variable | section 3.2.1   |
                Table 3: MAC Address Descriptor TLVs

3.2.1. MAC-Reachability TLV

      | Type= MAC-RI  |                  (1 byte)
      |   Length      |                  (1 byte)
      |V|F|   RESV    |              Data Label            |  (4 bytes)
      |                          MAC (1)       (6 bytes)                 |
      |                      .................                           |
      |                          MAC (N)       (6 bytes)                 |
              Figure 4: MAC-Reachability TLV format

Length is 4 plus a multiple of 6.

The bits of 'V' and 'F' are used to identify Data Label type and are defined as follows:

   | Bit      | Description             |
   | 'V'      | VLAN                    |
   | 'F'      | Fine Grained Label      |
   Table 4: Data Label Type Bits Definitions

Notes: If BGP LS is used for NVO3 network MAC address distribution between external SDN Controller and NVE, Data Label can be used to represent 24 bits VN ID.

3.3. BGP-LS attribute

3.3.1. Node Attribute TLVs Node Flag Bits TLV

      0                   1                   2                   3
      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              |           Length              |
      |O|T|E|B|G| Reserved  |
              Figure 5: Node Flag Bits TLV format

A new Node Flag bit is added as follows:

   | Bit      |          Description       | Reference |
   | 'G'      | Layer 3 Gateway Bit        | [RFC7176] |
   | Reserved | Reserved for future use    |           |
     Table 5: Node Flag Bits Definitions   

The new bit and remaining reserved bits are defined as follows: Opaque Node Attribute TLV

The Opaque Node Attribute TLV is used as the envelope to transparently carry TRILL specific information. In [RFC7176], there are the following Sub-TLVs in the Router Capability and MT- Capability TLVs and the Group Address (GADDR) TLV that need to be carried. Future possible TRILL TLVs/Sub-TLVs extension also can be carried using the Opaque Node Attribute TLV.

   Descriptions       IS-IS TLV/Sub-TLV
   TRILL-VER             22/13
   NICKNAME              22/6
   TREES                 22/7
   TREE-RT-IDs           22/8
   TREE-USE-IDs          22/9
   INT-VLAN              22/10
   VLAN-GROUP            22/14
   INT-LABEL             22/15
   RBCHANNELS            22/16
   AFFINITY              22/17
   LABEL-GROUP           22/18
   GMAC-ADDR             142/1
   GIP-ADDR              142/2
   GIPV6-ADDR            142/3
   GLMAC-ADDR            142/4
   GLIP-ADDR             142/5
   GLIPV6-ADDR           142/6

   Table 6: TRILL TLVs/Sub-TLVs

3.3.2. Link Attribute TLVs

Link attribute TLVs are TLVs that may be encoded in the BGP-LS attribute with a link NLRI. Besides the TLVs that has been defined in [RFC7752] section 3.3.2 table 9, the following 'Link Attribute' TLV is provided for TRILL.

   | TLV Code  | Description    | IS-IS TLV    | Defined in:      |
   | Point     |                | /Sub-TLV     |                  |
   | TBD       | Link MTU       |   22/28      | [RFC7176]/2.4    |
                       Table 7: Link Attribute TLVs

4. Operational Considerations

This document does not require any MIB or Yang model to configure operational parameters.

An implementation of this specification[idr-ls-trill], MUST do the malformed attribute checks below, and if it detects a malformed attribute, it should use the 'Attribute Discard' action per [RFC7606] section 2.

An implementation MUST perform the following expanded [BGP-LS] syntactic check for determining if the message is malformed:

In addition, the following checks need to be made for the fields specific to the BGP LS for TRILL:

5. Security Considerations

Procedures and protocol extensions defined in this document do not affect the BGP security model. See [RFC6952] for details.

6. IANA Considerations

This section complies with [RFC7153]. For all of the following assignments, [this document] is the reference.

IANA is requested to requested to assign one Protocol-ID for "TRILL" from the BGP-LS registry of Protocol-IDs

IANA is requested to assign one NLRI Type for "MAC Reachability" from the BGP-LS registry of NLRI Types.

IANA is requested to assign one Node Flag bit for "Layer 3 Gateway" from the BGP-LS registry of BGP-LS Attribute TLVs.

IANA is requested to assign one new TLV type for "Link MTU" from the BGP-LS registry of BGP-LS Attribute TLVs.

7. Acknowledgements

Authors like to thank Andrew Qu, Jie Dong, Mingui Zhang, Qin Wu, Shunwan Zhuang, Zitao Wang, Lili Wang for their valuable inputs.

8. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[RFC4271] Rekhter, Y., Li, T. and S. Hares, "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006.
[RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S. and A. Ghanwani, "Routing Bridges (RBridges): Base Protocol Specification", RFC 6325, DOI 10.17487/RFC6325, July 2011.
[RFC6952] Jethanandani, M., Patel, K. and L. Zheng, "Analysis of BGP, LDP, PCEP, and MSDP Issues According to the Keying and Authentication for Routing Protocols (KARP) Design Guide", RFC 6952, DOI 10.17487/RFC6952, May 2013.
[RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP Extended Communities", RFC 7153, DOI 10.17487/RFC7153, March 2014.
[RFC7172] Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R. and D. Dutt, "Transparent Interconnection of Lots of Links (TRILL): Fine-Grained Labeling", RFC 7172, DOI 10.17487/RFC7172, May 2014.
[RFC7176] Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt, D. and A. Banerjee, "Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS", RFC 7176, DOI 10.17487/RFC7176, May 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, DOI 10.17487/RFC7357, September 2014.
[RFC7606] Chen, E., Scudder, J., Mohapatra, P. and K. Patel, "Revised Error Handling for BGP UPDATE Messages", RFC 7606, DOI 10.17487/RFC7606, August 2015.
[RFC7752] Gredler, H., Medved, J., Previdi, S., Farrel, A. and S. Ray, "North-Bound Distribution of Link-State and Traffic Engineering (TE) Information Using BGP", RFC 7752, DOI 10.17487/RFC7752, March 2016.

Authors' Addresses

Weiquo Hao Huawei Technologies 101 Software Avenue, Nanjing, 210012 China Phone: +86-25-56623144 EMail:
Donald E. Eastlake Huawei Technologies 155 Beaver Street Milford , MA 01757 USA Phone: +1-508-333-2270 EMail:
Susan Hares Huawei Technologies 7453 Hickory Saline , MI 48176 USA Phone: +1-734-604-0332 EMail:
Sujay Gupta IP Infusion EMail:
Muhammad Durrani Cisco Systems Phone: +1-408-527-6921 EMail:
Yizhou Li Huawei Technologies 101 Software Avenue, Nanjing, 210012 China EMail: