TRILL Working Group                                                Y. Li
INTERNET-DRAFT                                               D. Eastlake
Intended Status: Standard Track                                L. Dunbar
                                                     Huawei Technologies
                                                              R. Perlman
                                                            I. Gashinsky
Expires: October 4, 2015                                   April 2, 2015

                       TRILL: ARP/ND Optimization


   This document describes mechanisms to optimize the ARP (Address
   Resolution Protocol) and ND (Neighbor Discovery) traffic in TRILL
   campus. Such optimization reduces packet flooding over a TRILL

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."

   The list of current Internet-Drafts can be accessed at

   The list of Internet-Draft Shadow Directories can be accessed at

Copyright and License Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the

Yizhou, et al                                                   [Page 1]

INTERNET DRAFT         TRILL ARP/ND Optimization              April 2015

   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  3
   2 IP/MAC Address Mappings  . . . . . . . . . . . . . . . . . . . .  4
   3 Handling ARP/ND Messages . . . . . . . . . . . . . . . . . . . .  4
     3.1 Get Sender's IP/MAC Mapping Information for Non-zero IP  . .  5
     3.2 Determine How to Reply to ARP/ND . . . . . . . . . . . . . .  5
     3.3 Determine How to Handle the ARP/ND Response  . . . . . . . .  7
   4 Handling RARP (Reverse Address Resolution Protocol) Messages . .  7
   5 Security Considerations  . . . . . . . . . . . . . . . . . . . .  7
   6 IANA Considerations  . . . . . . . . . . . . . . . . . . . . . .  8
   7 References . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     7.1 Normative References . . . . . . . . . . . . . . . . . . . .  8
     7.2 Informative References . . . . . . . . . . . . . . . . . . .  9
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  9

Yizhou, et al                                                   [Page 2]

INTERNET DRAFT         TRILL ARP/ND Optimization              April 2015

1 Introduction

   ARP [RFC826] and ND [RFC4861] are normally sent by broadcast and
   multicast respectively. To reduce the burden on a TRILL campus caused
   by these multi-destination messages, RBridges MAY implement an
   "optimized ARP/ND response", as specified herein, when the target's
   location is known by the ingress RBridge or can be obtained from a
   directory. This avoids ARP/ND query flooding.

1.1  Terminology

   The acronyms and terminology in [RFC6325] are used herein. Some of
   these are listed below for convenience with the following along with
   some additions:

   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".

   APPsub-TLV     Application sub-Type-Length-Values

   ARP            Address Resolution Protocol [RFC826]

   DAD            Duplicate Address Detection

   Data Label     VLAN or FGL

   ESADI          End Station Address Distribution Information [RFC7357]

   FGL            Fine-Grained Label [RFC7172]

   IA             Interface Addresses, a TRILL APPsub-TLV [IA-draft]

   IP             Internet Protocol

   MAC            Media Access Control address

   ND             Neighbor Discoery [RFC4861]

   RBridge        Routing Bridge, an alternative term for a TRILL

   SEND           secure neighbor discovery [RFC3971]

   TRILL          Transparent Interconnection of Lots of Links or

Yizhou, et al                                                   [Page 3]

INTERNET DRAFT         TRILL ARP/ND Optimization              April 2015

   Tunneled Routing in the Link Layer.

   TRILL switch   A device implementing the TRILL protocol, an
   alternative term for an RBridge.

2 IP/MAC Address Mappings

   Traditionally an RBridge learns the MAC and Data Label (VLAN or FGL)
   to nickname correspondence of a remote host, as per [RFC6325] and
   [RFC7172], from TRILL data frames received. No IP address information
   is learned directly from the TRILL data frame. Interface Addresses
   (IA) APPsub-TLV [IA-draft] enhances the TRILL base protocol by
   allowing IP and MAC address mappings to be distributed in the control
   plane by any RBridge. This APPsub-TLV appears inside the TRILL
   GENINFO TLV in ESADI [RFC7357] but the value data structure it
   specifies may also occur in other application contexts. Edge
   Directory Assist Mechanisms [DirMech] makes use of this APPsub-TLV
   for its push model and uses the value data structure it specifies in
   its pull model.

   An RBridge can easily know the IP/MAC address mappings of the local
   hosts that it is attached to it via its access ports by receiving ARP
   [RFC826] or ND [RFC4861] messages. If the RBridge has extracted the
   sender's IP/MAC address pair from the received data packet, it may
   save the information and use the IA APPsub-TLV to distribute it to
   other RBridges through ESADI. Then the relevant remote RBridges
   (normally those interested in the same Data Label as the original
   ARP/ND messages) receive and save such mapping information also.
   There are others ways that RBridges save IP/MAC address mappings in
   advance, e.g. import from management system and distribution by
   directory servers [DirMech].

   The examples given above shows that RBridges may have saved a host's
   triplet of {IP address, MAC address, ingress nickname} for a given
   Data Label (VLAN or FGL) before that host sends or receives any real
   data packet. Note such information may or may not be a complete list
   and may or may not exist on all RBridges. The information may
   possibly be from different sources. RBridges can then use the Flags
   Field in IA APPsub-TLV to identify if the source is a directory
   server or local observation by the sender. A different confidence
   level may also be used to indicate the reliability of the mapping

3 Handling ARP/ND Messages

   A native frame that is an ARP [RFC826] message is detected by its
   Ethertype of 0x0806. A native frame that is an ND [RFC4861] is

Yizhou, et al                                                   [Page 4]

INTERNET DRAFT         TRILL ARP/ND Optimization              April 2015

   detected by being one of five different ICMPv6 packet types. ARP/ND
   is commonly used on a link to (1) query for the MAC address
   corresponding to an IPv4 or IPv6 address, (2) test if an IPv4/IPv6
   address is already in use, or (3) to announce the new or updated info
   on any of IPv4/IPv6 address, MAC address, and/or point of attachment.

   To simplify the text, we use the following terms in this section.

     1) IP address - indicated protocol address that is normally an IPv4
     address in ARP or an IPv6 address in ND.

     2) sender's IP/MAC address - sender protocol/hardware address in
     ARP, source IP address and source link-layer address in ND

     3) target's IP/MAC address - target protocol/hardware address in
     ARP, target address and target link-layer address in ND

   When an ingress RBridge receives an ARP/ND message, it can perform
   the steps described in the sub-sections below.

3.1 Get Sender's IP/MAC Mapping Information for Non-zero IP

   If the sender's IP has not been saved by the ingress RBridge before,
   populate the information of sender's IP/MAC in its ARP table;

   else if the sender's IP has been saved before but with a different
   MAC address mapped or a different ingress nickname associated with
   the same pair of IP/MAC, the RBridge should verify if a duplicate IP
   address has already been in use or a host has changed its attaching
   RBridge. The RBridge may use different strategies to do so, for
   example, ask an authoritative entity like directory servers or
   encapsulate and unicast the ARP/ND message to the location where it
   believes the address is in use. RBridge should update the saved
   triplet of {IP address, MAC address, ingress nickname} based on the

   The ingress RBridge may use the IA APPsub-TLV [IA-draft] with the
   Local flag set in ESADI [RFC7357] to distribute any new or updated
   triplet of {IP address, MAC address, ingress nickname} information
   obtained in this step. If a push directory server is used, such
   information can be distributed as per [DirMech].

3.2 Determine How to Reply to ARP/ND

   a) If the message is a generic ARP/ND request and the ingress RBridge
   knows the target's IP address, the ingress RBridge may decide to take

Yizhou, et al                                                   [Page 5]

INTERNET DRAFT         TRILL ARP/ND Optimization              April 2015

   one or a combination of the following actions:

     a.1. Send an ARP/ND response directly to the querier, with the
     target's MAC address, as believed by the ingress RBridge.

     a.2. Encapsulate the ARP/ND request to the target's Designated
     RBridge, and have the egress RBridge for the target forward the
     query to the target. This behavior has the advantage that a
     response to the request is authoritative. If the request does not
     reach the target, then the querier does not get a response.

     a.3. Block ARP/ND requests that occur for some time after a request
     to the same target has been launched, and then respond to the
     querier when the response to the recently-launched query to that
     target is received.

     a.4. Pull the most up-to-date records if a pull directory server is
     available [DirMech] and reply to the querier.

     a.5. Flood the request as per [RFC6325].

   b) If the message is a generic ARP request and the ingress RBridge
   does not know target's IP address, the ingress RBridge may take one
   of the following actions.

     b.1. Flood the message as per [RFC6325].

     b.2. Use directory server to pull the information [DirMech] and
     reply to the querier.

     b.3. Drop the message.

   c) If the message is a gratuitous ARP which can be identified by the
   same sender's and target's "protocol" address fields or an
   Unsolicited Neighbor Advertisements [RFC4861] in ND:

   The RBridge may use an IA APPsub-TLV [IA-draft] with the Local flag
   set to distribute the sender's MAC and IP mapping information. When
   one or more directory servers are deployed and complete Push
   Directory information is used by all the TRILL switches in the Data
   Label, a gratuitous ARP or unsolicited NA SHOULD be discarded rather
   than ingressed. Otherwise, they are either ingressed and flooded as
   per [RFC6325] or discarded depending on local policy.

   d) If the message is a Address Probe ARP Query [RFC5227] which can be
   identified by the sender's protocol (IPv4) address field being zero
   and the target's protocol address field being the IPv4 address to be

Yizhou, et al                                                   [Page 6]

INTERNET DRAFT         TRILL ARP/ND Optimization              April 2015

   tested or a Neighbor Solicitation for DAD (Duplicate Address
   Detection) which has the unspecified source address [RFC4862]: it
   should be handled as the generic ARP message as in a) and b).

   It should be noted in the case of secure neighbor discovery (SEND)
   [RFC3971], cryptography might prevent local reply by the ingress
   RBridge, since the RBridge would not be able to sign the response
   with the target's private key.

   It is not essential that all RBridges use the same strategy for which
   option to select for a particular ARP/ND query. It is up to the

3.3 Determine How to Handle the ARP/ND Response

   If the ingress RBridge R1 decides to unicast the ARP/ND request to
   the target's egress RBridge R2 as discussed in subsection 3.2 item a)
   or to flood the request as per [RFC6325], then R2 decapsulates the
   query, and initiates an ARP/ND query on the target's link. When/if
   the target responds, R2 encapsulates and unicasts the response to R1,
   which decapsulates the response and sends it to the querier. R2
   should initiates a link state update to inform all the other RBridges
   of the target's location, layer 3 address, and layer 2 address, in
   addition to forwarding the reply to the querier. The update message
   can be carried by an IA APPsub-TLV [IA-draft] with the Local flag set
   in ESADI [RFC7357] or as per [DirMech] if push directory server is in

4 Handling RARP (Reverse Address Resolution Protocol) Messages

   RARP [RFC903] uses the same packet format as ARP but a different
   Ethertype (0x8035) and opcode values. Its use is similar to the
   generic ARP Request/Response as described in 3.2 a) and b).  The
   difference is that it is intended to query for the target "protocol"
   address corresponding to the target "hardware" address provided.  It
   should be handled by doing a local cache or directory server lookup
   on the target "hardware" address provided to find a mapping to the
   desired "protocol" address. Normally, it is used to look up a MAC
   address to find the corresponding IP address.

5 Security Considerations

   ARP and ND messages can be easily forged. Therefore the learning of
   MAC/IP addresses from them should not be considered as reliable.
   RBridge can use the confidence level in IA APPsub-TLV information
   received via ESADI or pull directory retrievals to determine the
   reliability of MAC/IP address mapping. (ESADI information can be

Yizhou, et al                                                   [Page 7]

INTERNET DRAFT         TRILL ARP/ND Optimization              April 2015

   secured as provide in [RFC7357] and pull directory information can be
   secured as provide in [DirMech].) It is up to the implementation to
   decide if an RBridge should distribute the IP and MAC address
   mappings received from local native ARP/ND messages to other RBridges
   in the same Data Label.

   The ingress RBridge should also rate limit the ARP/ND queries for the
   same target to be injected into the TRILL campus to prevent possible
   denial of service attacks.

6 IANA Considerations

   No IANA action is required. RFC Editor: please delete this section
   before publication.

7 References

7.1 Normative References

   [RFC826]  Plummer, D., "An Ethernet Address Resolution Protocol", RFC
              826, November 1982.

   [RFC903]  Finlayson, R., Mann, T., Mogul, J., and M. Theimer, "A
              Reverse Address Resolution Protocol", STD 38, RFC 903,
              June 1984

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

   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              September 2007.

   [RFC4862]  Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
              Address Autoconfiguration", RFC 4862, September 2007.

   [RFC6165]  Banerjee, A. and D. Ward, "Extensions to IS-IS for Layer-2
              Systems", RFC 6165, April 2011.

   [RFC6325]  Perlman, R., "RBridge: Base Protocol
              Specification", RFC 6325, July 2011.

   [RFC6439] Eastlake, D., "RBridge: Appointed Forwarder", RFC
              6439, November 2011.

Yizhou, et al                                                   [Page 8]

INTERNET DRAFT         TRILL ARP/ND Optimization              April 2015

   [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, May 2014,

7.2 Informative References

   [RFC3971]  Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander,
              "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005.

   [RFC5227]  Cheshire, S., "IPv4 Address Conflict Detection", RFC 5227,
              July 2008.

   [RFC7067] Dunbar, L., Eastlake 3rd, D., Perlman, R., and I.
              Gashinsky, "Directory Assistance Problem and High-Level
              Design Proposal", RFC 7067, November 2013.

   [IA-draft] Eastlake, D., Li Y., R. Perlman, "TRILL: Interface
              Addresses APPsub-TLV", draft-eastlake-trill-ia-appsubtlv,
              work in progress.

   [DirMech] Dunbar, L., Eastlake 3rd, D., Perlman, R., I. Gashinsky.
              and Li Y., TRILL: Edge Directory Assist Mechanisms",
              draft-ietf-trill-directory-assist-mechanisms, work in

Authors' Addresses

   Yizhou Li
   Huawei Technologies
   101 Software Avenue,
   Nanjing 210012

   Phone: +86-25-56625375

   Donald Eastlake
   Huawei R&D USA
   155 Beaver Street
   Milford, MA 01757 USA

   Phone: +1-508-333-2270

   Linda Dunbar

Yizhou, et al                                                   [Page 9]

INTERNET DRAFT         TRILL ARP/ND Optimization              April 2015

   Huawei Technologies
   5430 Legacy Drive, Suite #175
   Plano, TX 75024, USA

   Phone: +1-469-277-5840

   Radia Perlman
   2010 256th Avenue NE, #200
   Bellevue, WA 98007


   Igor Gashinsky
   45 West 18th Street 6th floor
   New York, NY 10011 USA


Yizhou, et al                                                  [Page 10]