TRILL Working Group Yizhou Li
INTERNET-DRAFT Donald Eastlake
Intended Status: Standard Track Linda Dunbar
Huawei Technologies
Radia Perlman
EMC
Igor Gashinsky
Yahoo
Expires: April 30, 2015 October 27, 2014
TRILL: ARP/ND Optimization
draft-yizhou-trill-arp-optimization-00
Abstract
This document describes mechanisms to optimize the ARP (Address
Resolution Protocol) and ND (Neighbor Discovery) traffic in TRILL
campus. Such optimization reduces the flooding over campus.
Status of this Memo
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Copyright and License Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2 IP/MAC address mappings . . . . . . . . . . . . . . . . . . . . 3
3. Handling ARP/ND messages . . . . . . . . . . . . . . . . . . . 4
3.1 Get the mapping information of the sender's IP and MAC for
non-zero IP. . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2 Determine how to reply the ARP/ND request. . . . . . . . . . 5
3.3 Determine how to handle the ARP/ND response. . . . . . . . . 6
4. Handling RARP (Reverse Address Resolution Protocol) messages . 6
5 Security Considerations . . . . . . . . . . . . . . . . . . . . 6
6 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
6 References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1 Normative References . . . . . . . . . . . . . . . . . . . 7
5.2 Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1 Introduction
IEEE 802.1 bridges forward an ARP/ND query as an ordinary
broadcast/multicast frame to all links belonging to the same VLAN.
RBridges May implement an "optimized ARP/ND response" when the
target's location is assumed to be known by the ingress RBridge.
ARP/ND query flooding can be avoided.
1.1 Terminology
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 RFC 2119 [RFC2119].
The acronyms and terminology in [RFC6325] is used herein with the
following additions:
TRILL switch - an alternative term for an RBridge.
2 IP/MAC address mappings
Traditionally an RBridge learns the MAC and nickname correspondence
of a remote host as per [RFC6325] from TRILL data frame received. No
IP address information is learned directly from the TRILL data frame.
Interface Addresses (IA) APPsub-TLV [IA] enhanced TRILL base protocol
by allowing IP and MAC address mappings to be distributed at the
control plane by any RBridge. This APPsub-TLV appears inside the
TRILL GENINFO TLV specified in ESADI [RFC7357] but may also occur in
other application contexts. Edge Directory Assist Mechanisms
[DirMech] makes use of this APPsub-TLV too for its push model.
An RBridge can easily know the IP/MAC address mappings of the hosts
in the local network that is attached to it via the access ports by
receiving the ARP [RFC826] or ND [RFC4861] messages. If the RBridge
has not saved sender's IP/MAC address pair in the received data
packet, it may save the information and use Interface Addresses
APPsub-TLV distribute them to other RBridges. Then the relevant
remote RBridges (normally those attached by hosts from the same Data
Label as the original ARP/ND messages) receives and saves such
mapping information too. There are others ways that RBridges saves
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 may have saved a host's
triplet of {IP address, MAC address, ingress nickname} for a given
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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. Information are possibly
from different sources. RBridges can use Flags Field in APPsub-TLV to
identify if the source is directory server or local observation by
the sender. Different confidence level may also be used to indicate
the reliability of the mapping information.
3. Handling ARP/ND messages
ARP [RFC826] message is detected by its Ethertype of 0x0806. ND
[RFC4861] defines five different ICMPv6 packet types. ARP/ND is
commonly used on a link to (1) query for the MAC address
corresponding to an IPv4 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.
IP address - indicated protocol address which is normally IPv4
address in ARP, IPv6 address in ND sender's IP/MAC address - sender
protocol/hardware address in ARP, source IP address and source link-
layer address in ND 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 following steps described in sub-sections.
3.1 Get the mapping information of the sender's IP and MAC for non-zero
IP.
If the information of the sender's MAC has not been saved by the
ingress RBridge before, populate the information of sender's IP/MAC
to its ARP table;
else if the sender's MAC has been saved before however with a
different IP address mapped, the RBridge should verify if a duplicate
IP address has already been in use. The RBridge may take different
strategies to do so, for example, ask the authoritative entity like
directory servers or encapsulate and unicast the ARP/ND message to
the location where it believes a duplicate address is in use.
The ingress RBridge may use IA APPsub-TLV [IA] with the Local flag
set in ESADI [RFC7357] to distribute any new or updated IP/MAC
information obtained in this step. If push directory server is used,
such information can be distributed as per [DirMech].
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3.2 Determine how to reply the ARP/ND request.
a) If the message is a generic ARP/ND request and the ingress RBridge
knows target's IP address, the ingress RBridge may decide to take one
or combination of the following actions:
1. send an ARP/ND response directly to the querier, with the target's
MAC address, as believed by the ingress RBridge
2. encapsulate the ARP/ND request to the target's Designated RBridge,
and have the Designated RBridge at 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
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
4. pull the most up-to-date records if pull directory server is in
use [DirMech] and reply to the querier
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.
1. flood the message as per RFC6325
2. use directory server to pull the information [DirMech] and reply
to the querier
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 IA APPsub-TLV [IA] with the Local flag set to
distribute the sender's MAC and IP mapping information. When
directory server is deployed and complete Push Directory information
is used by all the TRILL switches in the Data Label, 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.
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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 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
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 Designated RBridge R2 as shown in subsection 3.2 item a
or to flood the request as per RFC6325, then R2 decapsulates the
query, and initiate an ARP/ND query on the target's link. When/if the
target responds, R2 encapsulates and unicast the response to R1,
which decapsulates the response and send 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 IA APPsub-TLV [IA] 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"
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, 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 received IA APPsub-TLV to
determine the reliability of MAC/IP address mapping. It is up to the
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implementation to decide if an RBridge should distribute the IP and
MAC address mappings received from ARP/ND to other RBridges in the
same VLAN/FGL.
The ingress RBridge should also rate limit the ARP/ND queries for the
same target to be injected to the TRILL campus prevent the possible
attack.
6 IANA Considerations
No IANA action is required. RFC Editor: please delete this section
before publication.
6 References
5.1 Normative References
[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.
[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
[RFC6165] Banerjee, A. and D. Ward, "Extensions to IS-IS for Layer-2
Systems", RFC 6165, April 2011.
[RFC6325] Perlman, R., et.al. "RBridge: Base Protocol Specification",
RFC 6325, July 2011.
[RFC6326bis] Eastlake, D., Banerjee, A., Dutt, D., Perlman, R., and
A. Ghanwani, "TRILL Use of IS-IS", draft-eastlake-isis-
rfc6326bis, work in progress.
[RFC6327bis] Eastlake 3rd, D., R. Perlman, A. Ghanwani, H. Yang, and
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V. Manral, "TRILL: Adjacency", draft-ietf-trill-
rfc6327bis, work in progress.
[RFC6439] Eastlake, D. et.al., "RBridge: Appointed Forwarder", RFC
6439, November 2011.
5.2 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] 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
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
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Linda Dunbar
Huawei Technologies
5430 Legacy Drive, Suite #175
Plano, TX 75024, USA
Phone: +1-469-277-5840
EMail: ldunbar@huawei.com
Radia Perlman
EMC
2010 256th Avenue NE, #200
Bellevue, WA 98007
USA
Email: Radia@alum.mit.edu
Igor Gashinsky
Yahoo
45 West 18th Street 6th floor
New York, NY 10011 USA
EMail: igor@yahoo-inc.com
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