TRILL Working Group Yizhou Li
INTERNET-DRAFT Donald Eastlake
Intended Status: Standard Track Linda Dunbar
Huawei Technologies
Radia Perlman
EMC
Igor Gashinsky
Yahoo
Expires: August 19, 2015 February 15, 2015
TRILL: ARP/ND Optimization
draft-yizhou-trill-arp-optimization-01
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
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Copyright and License Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
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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 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 . . . . . . . . 6
4 Handling RARP (Reverse Address Resolution Protocol) Messages . . 7
5 Security Considerations . . . . . . . . . . . . . . . . . . . . 7
6 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1 Normative References . . . . . . . . . . . . . . . . . . . . 8
7.2 Informative References . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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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] is 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".
Data Label - VLAN or FGL.
ARP - Address Resolution Protocol [RFC826].
ESADI - End Station Address Distribution Information [RFC7357].
FGL - Fine-Grained Label [RFC7172].
IA - Interface Addresses, a TRILL APPsub-TLV [IA].
ND - Neighbor Discoery [RFC4861].
RBridge - Routing Bridge, an alternative term for a TRILL switch.
TRILL - Transparent Interconnection of Lots of Links or 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 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
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Addresses (IA) APPsub-TLV [IA] 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 be
possibly 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. 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
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.
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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 MAC 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 MAC has been saved before but with a different
IP address mapped, the RBridge should verify if a duplicate IP
address has already been in use. 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 a duplicate address is in use.
The ingress RBridge may use the 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 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
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
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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] 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
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
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)
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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 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] 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, 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].) 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.
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
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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., et.al. "RBridge: Base Protocol
Specification", RFC 6325, July 2011.
[RFC6439] Eastlake, D. et.al., "RBridge: Appointed Forwarder", RFC
6439, November 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,
<http://www.rfc-editor.org/info/rfc7172>.
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.
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[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
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
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Email: Radia@alum.mit.edu
Igor Gashinsky
Yahoo
45 West 18th Street 6th floor
New York, NY 10011 USA
EMail: igor@yahoo-inc.com
Yizhou, et al [Page 10]
