Internet DRAFT - draft-daniel-dna-fastraopt
draft-daniel-dna-fastraopt
Network Working Group S. Daniel Park
Internet-Draft SAMSUNG Electronics
Expires: December 7, 2005 June 8, 2005
IPv6 Fast Neighbor Discovery Option
draft-daniel-dna-fastraopt-00.txt
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Copyright (C) The Internet Society (2005).
Abstract
To minimize router delay in response to Router Solicitation message,
several scheme are being discussed in IETF. This document suggests a
new Neighbor Discovery option which is included in Router
Solicitation and/or Router Advertisement messages to achieve fast
network attachment.
1. Introduction
All router must delay a response to a Router Solicitation message by
a random delay between 0 and 500 miliseconds which is defined in
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[RFC2461]. It is because if there is more than one router on the
link, simultaneously transmitted responses will collide if the
routers try to answer the Router Solicitation immediately, and,
additionally, to avoid congestion when a link comes up and all hosts
on the link solicit. It's not problem in wired networks, however,
seems not appropriate in mobile environment since above ramdan delay
cause a critical problem to achieve fast and seamless handover.
In general, one proposel is being used to fast Router Solicitation /
Router Advertisement messages exchange called Fast Router
Advertisement [I-D.mkhalil-ipv6-fastra]. It newly defines a router
variable to allow for faster response times in the process of Router
Solicitations. Thus, network administrator must configure this
variable on its router manually. In addition, routers enabling Fast
RA will send Router Advertisement in response to all host request on
the link although fixed hosts do not need fast response in the
process of Router Solicitation.
Along with this scheme, DNA Working Group defines new options and
flags into Router Advertisement messages to eliminate the delays
introduced by [RFC2461] in discovering the configuration.
This document suggests a new Neighbor Discovery option which is
included in Router Solicitation and/or Router Advertisement messages
to allow the routers to answer the Router Solicitation immediately.
It does not require any network administrator configuration at all.
Network entities which can not recognize this option will silently
discard this option.
2. Requirements notation
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].
3. Fast Neighbor Discovery Option
The new option is defined in this section.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Option Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
<Fig. 1, Fast Neighbor Discovery Option Format>
o Option Type: To be defined by IANA
o Option Length: 8-bit unsigned integer. The length of the option
(including the type and length fields) in units of 8 octets. The
value 0 is invalid. Nodes MUST silently discard an Neighbor
Discovery packet that contains an option with length zero.
o Reserved: Reserved fields for further extensions.
This option does not have any alignment requirements.
4. Procedure of Fast Neighbor Discovery
The processing of Fast ND option is handled like any other ND option
and no new procedure is needed. It is so hard to encode a new option
into current ND stack which is already widely implemented in IPv6
equipment, so author recommends this option to be accomplished by DNA
WG when defining its new ND options.
The Router Solicitation sent by hosts which do not need fast ND
message exchange in its link will not contain the new Fast ND option
defined by this document. Routers which can not recognize the option
will silently discard this option.
Mobile entities (routers connected to wireless interface and mobile
hosts) are able to be configured selectively by network
administrator. Thus, mobile nodes will only receive fast Router
Advertisement in response to Router Solicitation with Fast ND option.
Once a node has IP-level connectivity with neighboring nodes, the
node sends a Router Solicitation to obtain an advertisement quickly,
rather than waits for an unsolicited advertisement from router. A
host sends one or more Router Solicitations to the all-routers
multicast group. To reduce packet flooding caused by Fast ND on its
link, the host enabling Fast ND will send Router Solicitations as few
as it can when generating its golbal scope addresses (I.e., defining
a new host parameter). Also, the router enabling Fast ND will only
answer Router Advertisements in response to link-local source address
assigned to the sending host.
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+--------+
| Router |
+----+---+
Fast RA (w/o delay)|/ | |RA (after random delay (0-500ms)
v | v
/-----------/ +----------------+
^ | ^
|RS w/Fast ND | |RS
/ | | |
+----+ +------+-----+
| MN | | Fixed Node |
+----+ +------------+
<Fig. 2, Network Model with Fast ND Option>
5. Security Considerations
The security of Fast ND option is the same as ND protocol security
concern. This option does not add any new vulnerability.
Security issues regarding the ND protocol have been discussed at IETF
SEND (Securing Neighbor Discovery) Working Group.
6 References
[I-D.mkhalil-ipv6-fastra]
Kempf, J., Khalil, M. and B. Pentland, "IPv6 Fast Router
Advertisement", draft-mkhalil-ipv6-fastra-05 (work in
progress), July 2004.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2461] Narten, T., Nordmark, E. and W. Simpson, "Neighbor
Discovery for IP Version 6 (IPv6)", RFC 2461, December
1998.
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Author's Address
Soohong Daniel Park
SAMSUNG Electronics
416 Maetan-3dong, Yeongtong-gu
Suwon-si, Gyeonggi-do 442-742
KOREA
Phone: +82 31 200 4508
EMail: soohong.park@samsung.com
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