Internet DRAFT - draft-elkins-v6ops-ipv6-ipid-needed
draft-elkins-v6ops-ipv6-ipid-needed
v6ops Working Group N. Elkins
Internet Draft Inside Products
Intended status: Standards track L. Kratzke
Expires: September, 2013 IBM
M. Ackermann
BCBS of Michigan
K. Haining
US Bank
April 2013
IPv6 IPID Needed
draft-elkins-v6ops-ipv6-ipid-needed-01.txt
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Abstract
The IPv4 main header contained a 16-bit IP Identification (IPID) field
used for fragmentation and reassembly. In practice, this field
was commonly used by network diagnosticians for tracking packets. In
IPv6, the IPID has been moved to the Fragment header, and would only
be used when fragmentation is required. Thus, the IPID field in IPv6,
is no longer able to be utilized in the valuable role it played in
IPv4, relative to diagnostics and problem resolution. This causes
great concern in particular for end users and large enterprises, for
whom Network/Application availability and performance can directly and
profoundly affect bottom line financials. Several viable solutions to
this situation exist.
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Table of Contents
1. Introduction ..................................................... 4
2. Conventions used in this document ................................ 5
3. Applicability ................................................... 6
6. Security Considerations .......................................... 7
7. IANA Considerations .............................................. 7
10.References ....................................................... 7
10.1. Normative References ...................................... 8
11. Acknowledgments ................................................. 8
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1. Introduction
In IPv4, the 16 bit IP Identification (IPID) field is located at an
offset of 4 bytes into the IPv4 header and is described in RFC791
[RFC791]. In IPv6, the IPID field is a 32 bit field contained in the
Fragment Header defined by section 4.5 of RFC2460 [RFC2460].
Unfortunately, unless fragmentation is being done by the source node,
the packet will not contain this Fragment Header, and therefore will
have no Identification field.
The intended purpose of the IPID field is to enable fragmentation and
reassembly, and as currently specified is required to be unique within
the maximum segment lifetime (MSL) on all datagrams. The MSL is often
2 minutes.
In Large Enterprise Networks, the IPID field is used for more than
fragmentation. During network diagnostics, packet traces may be taken
at multiple places along the path, or at the source and destination.
Then, packets can be matched by looking at the IPID.
Obviously, the time at each device will differ according to the clock
on that device; so another metric is required. This method of taking
multiple traces along the path is of special use on large multi-tier
networks to see where the packet loss or packet corruption is
happening. Multi-tier networks are those which have multiple routers
or switches on the path between the sender and the receiver.
The inclusion of the IPID makes it easier for a device(s) in the
middle of the network, or on the receiving end of the network, to
identify flows belonging to a single node, even if that node might
have a different IP address. For example, if the sending node is a
mobile laptop with a wireless connection to the Internet.
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For its de-facto diagnostic mode usage, the IPID field needs to be
available whether or not fragmentation occurs. It also needs to be
unique in the context of the entire session, and across all the
connections controlled by the stack.
This document will present information that demonstrates how valuable
and useful the IPID field has been (in IPv4) for diagnostics and
problem resolution, and how not having it available (in IPv6), could
be a major detriment to new IPv6 deployments and contribute to
protracted downtimes in existing IPv6 operations.
As network technology has evolved, the uses to which fields are put can
change as well. De-facto use is powerful, and should not be lightly
ignored. In fact, it is a testiment to the power and pervasiveness of
the protocol that users create new uses for the original technology.
For example, the use of the IPID goes beyond the vision of the original
authors. This sort of thing has happened with numerous other
technologies. It is similar to the ways in which cell phones have
evolved to be more than just a means of vocal communication, including
Internet communications, photo-sharing, stock exchange transactions,
etc. Or the way that the bicycle, originally intended merely as a
means of fashionable transportation for a single individual, developed
into a replacement for the horse in hauling materials. Or the way
that the automobile went from being a means of transport for people
to a truck, for transport of materials on a large scale. Indeed,
the Internet itself has evolved, from a small network for researchers
and the military to share files into the pervasive global information
superhighway that it is today.
2. Conventions used in this document
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 [RFC2119].
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3. Applicability
The ability to utilize the IPID has enhanced problem diagnosis
efforts and significantly reduced problem resolution time.
Several actual use case examples are shown below. These
demonstrate how use of the IPID has reduced problem resolution time in
very valuable production networks of Large Enterprises/End Users. In
general, if a problem or performance issue with an application or
network component can be fixed in minutes, as opposed to hours, this
can mean significant dollar savings to large enterprises. The IPID
can be used extensively when debugging involves traces or packet
captures. Its absence in IPv6 may lead to protracted problem
diagnosis and extended problem resolution time.
This value/perspective may be unique to tech support organizations
of large enterprises. Other functional areas may not share this
concern/perspective, as packets could continue to flow, but service
levels may not be acceptable to end users during the extended problem
resolution time.
Although very situation dependent, the use cases below clearly
illustrate the value of network availability, and the need to keep
problem resolution time to an absolute minimum.
Another benefit of using the IPID to expedite problem resolution
is reducing the cost of associated resources being consumed during
extended problem resolution, such as storage, CPU and staff time.
Will IPID be critical in most problem resolutions? NO! But if
it even helps in a few per year, significant money and/or lost
business could be saved.
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A facility such as IPID, that has proven field value, should not
be eliminated as an effective diagnosis tool!
USE CASE EXAMPLEs:
USE CASE #1 --- Large Insurance Company
- (estimated time saved by use of IPID: 7 hours)
PERFORMANCE TOOL PRODUCES EXTRANEOUS PACKETS?
- Issue was whether a performance tool was accurately replicating
session flow during performance testing?
- Trace IPIDs showed more unique packets within same flow from
performance tool compared to IE Browser.
- Having the clear IPID sequence numbers also showed where and why
the extra packets were being generated.
- Solution: Problem rectified in subsequent version of performance
tool.
- Without IPID, it was not clear if there was an issue at all.
USE CASE #2 --- Large Bank
- (estimated time saved by use of IPID: 4 hours)
BATCH TRANSFER DURATION INCREASES 12X
- A 30 minute data transfer started taking 6-8 hours to complete.
- Possible packet loss? All vendors said no.
- Other Apps were working OK.
- 4 trace points used, and then IPIDs compared.
- Showed 7% packet loss.
- Solution: WAN hardware was replaced and problem fixed.
- Without IPID, no one would agree a problem existed
USE CASE #3 --- Large Bank
- (estimated time saved by use of IPID: 6 hours)
VERY SLOW INTERACTIVE PERFORMANCE.
- All network links looked good.
- Traces showed duplicated small packets (which can be OK).
- Saw that IPID was equal but TTL was always + 1.
- Network device was "Splitting" small packets only.(2 interfaces).
- The small packets were control info, telling other side to slow
down.
- Erroneously looked like network congestion.
- Solution: Network Device replaced and good interactive
performance restored.
- Without IPID, flows would have appeared OK.
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USE CASE #4 --- Large Government Agency
- (estimated time saved by use of IPID: 9 hours)
VPN DROPS
- Cell phone connections to law enforcement were being dropped.
Going through a VPN.
- All parties (both sides of VPN connection, application, etc.) said
it was not their problem. Problem went on for weeks.
- Finally, when we were called in as consultants, we took a trace
which showed packet with IPID and TTL that did not match others in
the flow AT ALL was coming from router nearest application server
end of VPN.
- Solution: Provider for VPN for application server changed. Problem
resolved.
- Without IPID, much harder to diagnose problem.
- (Same case also happened with large corporation. Again, all
parties saying not their fault until proven via packet trace.)
The IPID is very valuable to large enterprises and Data Center
Operators (EDCO) in trace analysis, specifically in reducing problem
diagnosis and resolution time. As such, IPID or something equivalent,
should be part of IPv6 for all situations where it can provide value.
(As it is IPv4.) Not just where fragmentation is required.
6. Security Considerations
There are no security considerations.
7. IANA Considerations
There are no IANA considerations.
10. References
10.1. Normative References
[RFC791] Postel, J., "Internet Protocol", RFC 791 / STD 5, September
1981.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
11. Acknowledgments
The authors would like to thank Fred Baker, Bill Jouris, Jose Isidro,
R. J. Atkinson, James Ashton, Sigfrido Perdomo and Neil Wasserman for
their reviews and suggestions that made this document better.
This document was prepared using 2-Word-v2.0.template.dot.
Authors' Addresses
Nalini Elkins
Inside Products, Inc.
36A Upper Circle
Carmel Valley, CA 93924
United States
Phone: +1 831 659 8360
Email: nalini.elkins@insidethestack.com
Lawrence Kratzke
IBM
8121 Glenbrittle Way
Raleigh, NC 27615
United States
Phone: +1 800-876-8801
Email: kratzke@us.ibm.com
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Michael Ackermann
Blue Cross Blue Shield of Michigan
P.O. Box 2888
Detroit, Michigan 48231
United States
Phone: +1 310 460 4080
Email: mackermann@bcbsmi.com
Keven Haining
US Bank
16900 W Capitol Drive
Brookfield, WI 53005
Phone: +1 262-790-3551
Email: keven.haining@usbank.com
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