TRILL Working Group Y. Li INTERNET-DRAFT D. Eastlake Intended Status: Standard Track L. Dunbar Huawei Technologies R. Perlman EMC Expires: September 12, 2016 March 11, 2016 TRILL: ARP/ND Optimization draft-ietf-trill-arp-optimization-04 Abstract 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 campus. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. 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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 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 8 8 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.1 Normative References . . . . . . . . . . . . . . . . . . . . 8 8.2 Informative References . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 Yizhou, et al [Page 2] INTERNET DRAFT TRILL ARP/ND Optimization March 2016 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 key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. The acronyms and terminology in [RFC6325] are used herein. Some of these are listed below for convenience along with some additions: APPsub-TLV Application sub-Type-Length-Values ARP Address Resolution Protocol [RFC826] Campus A TRILL network consisting of RBridges, links, and possibly bridges bounded by end stations and IP routers. 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 ND Neighbor Discovery [RFC4861] RBridge A contraction of "Routing Bridge". A device implementing the TRILL protocol. SEND secure neighbor discovery [RFC3971] Yizhou, et al [Page 3] INTERNET DRAFT TRILL ARP/ND Optimization March 2016 TRILL Transparent Interconnection of Lots of Links or Tunneled Routing in the Link Layer. 2 IP/MAC Address Mappings By default, an RBridge [RFC6325] [RFC7172] learns MAC Address and Data Label (VLAN or FGL) to egress nickname mapping information from TRILL data frames it receives. 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 end stations 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 (either ARP or ND), 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 show that RBridges might have saved an end station's triplet of {IP address, MAC address, ingress nickname} for a given Data Label (VLAN or FGL) before that end station sends or receives any real data packet. Note such information might or might not be a complete list and might or might not exist on all RBridges. The information could 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 information. 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 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 Yizhou, et al [Page 4] INTERNET DRAFT TRILL ARP/ND Optimization March 2016 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 IP/MAC address in ARP, source IP address and source link-layer address in ND 3) target's IP/MAC address - target IP/MAC 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 o 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; o 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 an end station has changed its attaching RBridge. The RBridge MAY use different strategies to do so. For example, the RBridge might ask an authoritative entity like directory servers or it might 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 verification. 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 take one or a combination of the following actions: Yizhou, et al [Page 5] INTERNET DRAFT TRILL ARP/ND Optimization March 2016 a.1. Send an ARP/ND response directly to the querier, with the target's MAC address, as known 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 RBridges 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 tested or a Neighbor Solicitation for DAD (Duplicate Address Detection) which has the unspecified source address [RFC4862]: it Yizhou, et al [Page 6] INTERNET DRAFT TRILL ARP/ND Optimization March 2016 SHOULD be handled as the generic ARP message as in a) and b). Note that in the case of secure neighbor discovery (SEND) [RFC3971], cryptography would 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 implementation. 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 initiate 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 use. 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" (IP) address corresponding to the target "hardware" (MAC) 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 secured as provide in [RFC7357] and pull directory information can be secured as provide in [DirMech]. The implementation decides if an Yizhou, et al [Page 7] INTERNET DRAFT TRILL ARP/ND Optimization March 2016 RBridge will 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 Acknowledgments The authors would like to thank Igor Gashinsky for his contributions. 8 References 8.1 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. [RFC6325] Perlman, R., et.al. "RBridge: Base Protocol Specification", RFC 6325, July 2011. [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, Yizhou, et al [Page 8] INTERNET DRAFT TRILL ARP/ND Optimization March 2016 . 8.2 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. [IA-draft] Eastlake, D., Li Y., R. Perlman, "TRILL: Interface Addresses APPsub-TLV", draft-ietf-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 progress. Authors' Addresses Yizhou Li Huawei Technologies 101 Software Avenue, Nanjing 210012 China Phone: +86-25-56625375 EMail: liyizhou@huawei.com Donald Eastlake Huawei R&D USA 155 Beaver Street Milford, MA 01757 USA Phone: +1-508-333-2270 EMail: d3e3e3@gmail.com Linda Dunbar Huawei Technologies 5430 Legacy Drive, Suite #175 Plano, TX 75024, USA Phone: +1-469-277-5840 EMail: ldunbar@huawei.com Yizhou, et al [Page 9] INTERNET DRAFT TRILL ARP/ND Optimization March 2016 Radia Perlman EMC 2010 256th Avenue NE, #200 Bellevue, WA 98007 USA EMail: Radia@alum.mit.edu Yizhou, et al [Page 10]