Network Working Group Thomas D. Nadeau
Expires: January 2006 George Swallow
Cisco Systems, Inc.
July 2005
Detecting MPLS Data Plane Failures in
Inter-AS and inter-provider Scenarios
draft-nadeau-mpls-interas-lspping-01.txt
Status of this Memo
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Abstract
This document describes a simple and efficient mechanism that can be
used to detect data plane failures in Multi-Protocol Label Switching
Label Switched Paths that extend beyond a single
Autonomous System and/or across multiple Service Provider network
boundaries. This document describes extensions to the existing
MPLS LSP Ping protocol to achieve these goals.
Table of Contents
1. Introduction...............................................
2. Terminology................................................
2.1 Conventions................................................
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2.2 Terminology................................................
2.3 Acronyms...................................................
3. Structure of This Document.................................
4. Motivation.................................................
5. Inter-AS Objects...........................................
6. Error Code.................................................
7. Theory of Operation........................................
7.1 Adjustments to Outgoing Labels.............................
7.2 Receiving Echo Replies 7.2.................................
8. Security Considerations...................................
9. IANA Considerations.......................................
9.1. Message Types, Reply Modes, Return Codes..................
9.2. TLVs......................................................
10. References................................................
10.1 Normative References......................................
10.2 Informative References....................................
11. Acknowledgements..........................................
12. Authors' Addresses........................................
13. Intellectual Property Statement...........................
14. Full Copyright Statement..................................
1. Introduction
This document describes a simple and efficient mechanism that can be
used to detect data plane failures in MPLS LSPs that span across
multiple Autonomous System (AS) and service provider boundaries.
At present, the existing MPLS LSP Ping protocol cannot handle
all but one of these cases. This document first explains
the scenarios where the existing protocol is inadequate, then
describes information carried in extended MPLS "echo request" and
"echo reply" messages; and finally describes enhanced mechanisms for
transporting the echo reply, as well as processing it at intermediate
points (both in an out of the originating AS).
An important consideration in this design is that MPLS echo requests
follow the same data path that normal MPLS packets would traverse.
MPLS echo requests are meant primarily to validate the data plane,
and secondarily to verify the data plane against the control plane.
Mechanisms to check the control plane are valuable, but are not cov-
ered in this document.
As is described in [LSPPING], to avoid potential Denial of Service
attacks, it is recommended to regulate the LSP ping traffic going
to the control plane. A rate limiter should be applied to the
well-known UDP port defined below. Furthermore, due to the
fact that there are data exchanges between provider networks
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which may wish to hide the details of their network, it is
recommended that the inter-AS border routers provide operators
with control over what information (i.e.: addresses) in these
messages.
2. Terminology
2.1 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 RFC 2119 [RFC2119].
2.2 Terminology
Definitions of key terms for MPLS OAM are found in [MPLS-OAM] and
the reader is assumed to be familiar with those definitions which
are not repeated here.
The following additional terms are useful to understand this
document.
2.3 Acronyms
The following list of acronyms is a repeat of common acronyms defined
in many other documents, and is provided here for convenience.
CE: Customer Edge
PE: Provider Edge
ASBR: Autonomous System Border Router
DoS: Denial of service
ECMP: Equal Cost Multipath
LDP: Label Distribution Protocol
LSP: Label Switch Path
LSR: Label Switch Router
OAM: Operations and Management
OA&M: Operations, Administration and Maintenance.
RSVP: Resource reSerVation Protocol
SP: Service Provider
3. Structure of This Document
The body of this memo contains four main parts: motivation,
extensions to the MPLS echo request/reply packet format, inter-AS
LSP ping operation, and a reliable return path. It is suggested
that first-time readers skip the actual packet formats and read
the Theory of Operation first; the document is structured the way
it is to avoid forward references.
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4. Motivation
The requirements specified in [MPLSOAM] stipulate that
data plane OAM functions must be provided as solutions
for service providers. These data plane test functions
must not only function within an autonomous system (AS),
but must also function across ASs. Furthermore, these
tests must function correctly across ASs that span multiple
Service Provider(SP) domains. At present, the data plane
liveliness tools function in these capacities only in
the narrow (and rarely used) case where the IP addresses
of LSRs involved are known to each other. For example,
when the IP addresses from one AS are exchanged through
routing with other attached ASs. Another case includes
the Layer-3 VPN inter-provider interconnection where
the PE addresses are distributed between service providers.
However, these cases are uncommon, and thus the existing
LSP Ping [LSPPING] tool is unable to respond under most
error condition configurations. For example consider the
following configuration. Imagine that PE1 and PE2 are
in two different provider domains. In this case, it is
commonly desirable for providers to NOT distribute the
IP addresses of any of the intermediate P routers
between PE1 and PE2.
{--- AS1 ---} {--- AS2 ---}
PE1--P-P--ASBR1----ASBR2--P-P--PE2
Now, imagine that the LSP that connects PE1 to PE2 contains
a fault somewhere bewteen ASBR2 and PE2 as is indicated
by 'X' between the two P routers:
{--- AS1 ---} {--- AS2 ---}
PE1--P-P--ASBR1----ASBR2--P-X-P--PE2
If an LSP Ping is initiated at PE1 with a destination
of PE2 and a source of PE1, the packet is label switched
correctly until it reaches the first P router within AS2.
Here lets imagine that MPLS forwarding is disabled on the
link between the two P routers. Upon discovering this while
attempting to process the LSP Ping Request packet, the
first P router will attempt to reply directly to PE1 with
the appropriate error code 5. However, because the
address of PE1 is actually private to AS1 by virtue of
not being distributed by ASBR1 into AS2, the P router
cannot correctly forward the reply to PE1. In this case,
PE1 may surmise that some failure has occurred, but it
cannot determine what the error is or where it exists.
This clearly does not meet the requirements stipulted
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in [OAMREQ]. This draft describes extensions to
[LSPPING] that overcome the aforementioned limitations,
and thus allow for the handling of inter-AS/provider
cases.
5. Inter-AS TLVs
5.1. Inter-AS TLV
The Inter-AS TLV Reply Object is an optional TLV that is used to
collect and report the ASBRs along the path of the LSP under
test. Only one such object may appear in a Reply message. The
purpose of this object is to allow the upstream router to relay a
Reply message from ASBR to ASBR when a failure is detected. A router
will use this TLV to look up the last ASBR as indicated as the
top-most address on the address stack, that forwarded the Request
message into its AS, and then forward the Reply to that router after
popping the address from the stack. The Reply message will ultimately
be relayed to the original soure of the request. This message has one
format that contains the true source and destination addresses of the
Request message, as well as a stack of ASBR addresses that were
visited while forwarding this message. Type 17 is defined for this
TLV (to be assigned by IANA).
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 17 (Inter-AS TLV) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Node IP Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Node AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed Node IP Address (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed Node AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed Node Contact String |
| |
| (16 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | SubLength |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Visited ASBR Address Stack |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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SubType
Sub-Type # Length Value Field
---------- ------ -------------
1 6 IPv4 Return Stack
2 6 IPv4 Trace Stack
3 6 Ipv6 Return Stack
4 6 IPv6 Trace Stack
Note that only combinations of 1+2 or 3+4 may be used.
Failed Node AS Number
This field may contain the AS number in which the node where
the failure was detected resides. If no AS number is indicated,
this field MUST contain 0s.
Failed Node IP Address
If the interface to the downstream LSR is numbered, then the Address
Type MUST be set to IPv4 or IPv6, the Downstream IP Address MUST be
set to either the downstream LSR's Router ID or the interface address
of the downstream LSR, and the Downstream Interface Address MUST be
set to the downstream LSR's interface address.
If the interface to the downstream LSR is unnumbered, the Address
Type MUST be Unnumbered, the Downstream IP Address MUST be the down-
stream LSR's Router ID (4 octets), and the Downstream Interface
Address MUST be set to the index assigned by the upstream LSR to the
interface.
Failed Node AS Number
This field may contain the AS number in which the node where
the failure was detected resides. If no AS number is indicated,
this field MUST contain 0s.
Failed Node Contact String
This field may contains a string of ASCII characters inserted by
the node where the failure was detected or by its closest ASBR.
This field MUST indicate contact information such as a provider's
international phone number and other relevant contact information
in cases where local policy dictates that a provider will not
fill in the Failed Node AS number and/or the Failed Node Address.
In all other cases, this field MUST contain 0s.
7.1.1 IPv4 Inter-AS TLV
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The value consists of four octets of an IPv4 prefix followed by one
octet of prefix length in bits; the format is given below. The IPv4
prefix is in network byte order; if the prefix is shorter than 32
bits, trailing bits SHOULD be set to zero. .
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 17 (Inter-AS TLV) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Node IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Node AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed Node IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed Node AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed Node Contact String |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7.1.1 IPv6 Inter-AS TLV
The value consists of 16 octets of an IPv6 prefix followed by one
octet of prefix length in bits; the format is given below. The IPv6
prefix is in network byte order; if the prefix is shorter than 128
bits, trailing bits SHOULD be set to zero. This FEC is used if the
protocol advertising the label is unknown, or may change during the
course of the LSP. An example is ani nter-AS LSP that may be sig-
naled by LDP in one AS, by RSVP-TE in another AS, and by BGP between
the ASs, such as is common for inter-AS VPNs.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 17 (Inter-AS TLV) | Length = 5 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Node IPv6 Address |
| (16 octets) |
| |
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| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Node AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed Node IPv6 Address |
| (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed Node AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Failed Node Contact String |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SubType | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
7.1.3 Visited ASBR Address Stack
The term Visited ASBR Address Stack applies to two stacks of IP
addresses of the ASBRs along the path of an LSP called the Trace and
Return Stacks. The two stacks have the same format; however they
have slightly different semantics. Both stack objects are stacks of
addresses that denote the list of visited ASBRs. They contain stack
of a single field containing either an IPv4 address if the TLV
SubType field is set to 1, or an IPv6 address as indicated by the
TLV SubType field being set to 3.
The Return Stack is to be used in a destructive manner as a
means of unwinding the path of ASBRs that were used to originally
forward the Request. Each subsequent ASBR along the path that
receives the reply should destructively remove itself from the
stack.
On the other hand, the Trace Stack MUST only be added to (i.e.:
ASBR addresses pushed) and items never removed from this stack.
This will allow the source to see the trace of the path of ASBRs
once the Reply message is returned. In cases where policy dictates
that ASBR addresses must be hidden, a value of all 0s MUST be
inserted into the stack, or the stack completely removed prior to
forwarding the Reply. It is prefered that a blank entry be left,
as this will at least indicate that there was one hop without
revealing its IP address.
IPv4 Trace and Visited Stack Objects
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The Length is 4*N octets, N is the number of visited ASBRs.
This object has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASBR IPv4 Address 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASBR IPv4 Address 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. ... .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASBR IPv4 Address N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ASBR IPv4 Address 1, ASBR IPv4 Address 1, ... contain a valid
IPv4 address.
IPv6 Trace and Visited Stack Objects
The Length is 16*N octets, N is the number of visited ASBRs.
This object has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASBR IPv6 Address 1 |
| ASBR IPv6 Address (Cont.) |
| ASBR IPv6 Address (Cont.) |
| ASBR IPv6 Address (Cont.) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. ... .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ASBR IPv6 Address N |
| ASBR IPv6 Address (Cont.) |
| ASBR IPv6 Address (Cont.) |
| ASBR IPv6 Address (Cont.) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ASBR IPv6 Address 1, ASBR IPv6 Address 1, ... contain a valid
IPv4 address.
IPv6
6. Error Code(s)
TBD
7. Theory of Operation
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When tracing an LSP which spans multiple AS, an Inter-AS Reply Object
is included in the Echo Request. Initially the object contains only
the address of the source PE and a Trace stack with that same address.
As the tracing progress each ASBR copies the trace stack as a reply stack,
It then pushes its address to the trace stack. It includes both stacks
in an Inter-AS Reply object and sends it in an Echo Reply message to
the top address in the reply stack. The receiver of the Reply message
then verifies that it is included in the reply stack. It then pops
its address from the reply stack and readdresses the Echo Reply
message to the (new) top element of the reply stack. This is repeated
until the source PE receives the Echo Reply.
7.1 Adjustments to Outgoing Labels
When an LSP request is sent from an originator, some adjustments may
need to be made to outgoing labels:
Inter-AS cases:
A) VRF to VRF
The LSP terminates at the ASBR. These procedures do not apply.
B) EBGP redistribution of labeled VPN-IPv4 routes from AS to
neighboring AS.
Tracing is performed by incrementing the VPN label begining at one.
If TTL hiding is in effect, then tracing of PSN label is not
necessary for these procedures.
C) Carrier's Carrier (CsC):
1) TTL Hiding
a. Will work as is.
b. Verification of the core must be done separately by core owners.
c. Traceroute can trace both stubs of the 'carried' carrier.
2) No TTL hiding
a. Set VPN TTL to 1.
b. CsC CE or Ps would return to the CsC PE who would relay messages
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back to originator.
c. For traceroute, set VPN TTL=1, and progressively increase the
IGP TTL by 1 to probe.
7.2 Receiving Echo Replies
The existing packet processing algorithm as specified in
[LSPPING] is enhanced as follows to support inter-AS/provider
LSP ping/trace.
When an Echo Reply message is received:
1) If the packet is addressed to this router
(i.e.: destination address == this router's router ID):
a. If the original sender field TLV == this router's address,
process normally. // today's functionality for a normal
reply received by the src.
b. Else this packet has been delivered to this router because it is
an ASBR and needs to proxy for a P router in its AS to return
the reply.
If the inter-AS TLV is present,
i. If the last visited AS is empty, set it to the ASBR's
primary AS#.
ii. If the stack is empty, this is an error case. The TLV should
not be present if the stack is empty.
iii. Else if the top-most address in the stack is this router's
address.
1. Pop it from the stack.
2. Replace the packet's destination address with the
next address in the stack.
3. Replace the packet's src address with this ASBR's address.
4. Optionally, the ASBR may hide (i.e.: remove) information
that its local policy has been configured for.
5. Look up the route/next-hop for this address and deliver
the packet. The ASBR should be able to resolve the address
because at this point unless there has been an error in
the return path forwarding, then the packet should be at
the border of the originating AS. If the look-up fails,
drop the packet and notify the operator of this router
that an error condition has occurred.
When an LSP ping request is received:
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1) If this router is an ASBR
a. Write the next entry in the Last Seen ASBR stack's address
as the destination address of the packet and forward it to
that address.
b. Otherwise process normally as specified in the LSP ping draft.
8. Security Considerations
In addition to the Security Considerations from [LSPPING],
here are at least two approaches to attacking LSRs using the mecha-
nisms defined here.
One is a Denial of Service attack, by sending
MPLS echo requests/replies to LSRs and thereby increasing their work-
load. The other is obfuscating the state of the MPLS data plane
liveness by spoofing, hijacking, replaying or otherwise tampering
with MPLS echo requests and replies.
Authentication will help reduce the number of seemingly valid MPLS
echo requests, and thus cut down the Denial of Service attacks;
beyond that, each LSR must protect itself.
Authentication sufficiently addresses spoofing, replay and most tam-
pering attacks; one hopes to use some mechanism devised or suggested
by the RPSec WG. It is not clear how to prevent hijacking (non-
delivery) of echo requests or replies; however, if these messages are
indeed hijacked, LSP ping will report that the data plane isn't work-
ing as it should.
It doesn't seem vital (at this point) to secure the data carried in
MPLS echo requests and replies, although knowledge of the state of
the MPLS data plane may be considered confidential by some.
9. IANA Considerations
[need to request some new Message Types, TLV Types, Return Codes]
9.1. Message Types, Reply Modes, Return Codes
It is requested that IANA maintain registries for Message Types,
Reply Modes, Return Codes and Return Subcodes. Each of these can
take values in the range 0-255. Assignments in the range 0-191 are
via Standards Action; assignments in the range 192-251 are made via
Expert Review; values in the range 252-255 are for Vendor Private
Use, and MUST NOT be allocated.
If any of these fields fall in the Vendor Private range, a top-level
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Vendor Enterprise Code TLV MUST be present in the message.
9.2. TLVs
It is requested that IANA maintain registries for the Type field of
top-level TLVs as well as for sub-TLVs. The valid range for each of
these is 0-65535. Assignments in the range 0-16383 and 32768-49161
are made via Standards Action as defined in [IANA]; assignments in
the range 16384-31743 and 49162-64511 are made via Expert Review (see
below); values in the range 31744-32746 and 64512-65535 are for Ven-
dor Private Use, and MUST NOT be allocated.
If a TLV or sub-TLV has a Type that falls in the range for Vendor
Private Use, the Length MUST be at least 4, and the first four octets
MUST be that vendor's SMI Enterprise Code, in network octet order.
The rest of the Value field is private to the vendor.
10. References
10.1 Normative References
[LSPPING] Kompella, k., Swallow, G., "Detecting MPLS Data Plane
Liveness", draft-ietf-mpls-lsp-ping-08.txt,
February 2005.
10.2 Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[MPLS-OAM] T. Nadeau, Allan D., et al. Allan D.,
"OAM Requirements for MPLS Networks",
draft-ietf-mpls-oam-requirements-05.txt,
December 2004
11. Acknowledgment
The authors wish to acknowledge and thank the following
individuals for their valuable comments to this document:
Azhar Sayeed, Vanson Lim, and Mike Piecuch.
12. Authors' Addresses
Thomas D. Nadeau
Cisco Systems, Inc.
300 Beaver Brook Road
Boxboro, MA 01719
Phone: +1-978-936-1470
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Email: tnadeau@cisco.com
George Swallow
Cisco Systems
1414 Massachusetts Ave,
Boxborough, MA 01719
Phone: +1 978 936 1398
Email: swallow@cisco.com
13. Intellectual Property Statement
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14. Full Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and
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This document and the information contained herein are provided on an
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