TRAM M. Petit-Huguenin
Internet-Draft Impedance Mismatch
Intended status: Standards Track G. Salgueiro
Expires: March 21, 2019 Cisco
September 17, 2018
Path MTU Discovery Using Session Traversal Utilities for NAT (STUN)
draft-ietf-tram-stun-pmtud-10
Abstract
This document describes a Session Traversal Utilities for NAT (STUN)
Usage for Path MTU Discovery (PMTUD) between a client and a server.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 21, 2019.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 1]
Internet-Draft STUN PMTUD September 2018
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Overview of Operations . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Probing Mechanisms . . . . . . . . . . . . . . . . . . . . . 5
4.1. Simple Probing Mechanism . . . . . . . . . . . . . . . . 6
4.1.1. Sending a Probe Request . . . . . . . . . . . . . . . 6
4.1.2. Receiving a Probe Request . . . . . . . . . . . . . . 6
4.1.3. Receiving a Probe Response . . . . . . . . . . . . . 7
4.2. Complete Probing Mechanism . . . . . . . . . . . . . . . 7
4.2.1. Sending the Probe Indications and Report Request . . 7
4.2.2. Receiving an ICMP Packet . . . . . . . . . . . . . . 8
4.2.3. Receiving a Probe Indication and Report Request . . . 8
4.2.4. Receiving a Report Response . . . . . . . . . . . . . 9
4.2.5. Using Checksums as Packet Identifiers . . . . . . . . 9
4.2.6. Using Sequence Numbers as Packet Identifiers . . . . 10
5. Probe Support Signaling Mechanisms . . . . . . . . . . . . . 10
5.1. Explicit Probe Support Signaling Mechanism . . . . . . . 11
5.2. Implicit Probe Support Signaling Mechanism . . . . . . . 11
6. STUN Attributes . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. IDENTIFIERS . . . . . . . . . . . . . . . . . . . . . . . 11
6.2. PMTUD-SUPPORTED . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
8.1. New STUN Methods . . . . . . . . . . . . . . . . . . . . 12
8.2. New STUN Attributes . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. Normative References . . . . . . . . . . . . . . . . . . 13
9.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Release Notes . . . . . . . . . . . . . . . . . . . 14
A.1. Modifications between draft-ietf-tram-stun-pmtud-10 and
draft-ietf-tram-stun-pmtud-09 . . . . . . . . . . . . . . 14
A.2. Modifications between draft-ietf-tram-stun-pmtud-09 and
draft-ietf-tram-stun-pmtud-08 . . . . . . . . . . . . . . 14
A.3. Modifications between draft-ietf-tram-stun-pmtud-08 and
draft-ietf-tram-stun-pmtud-07 . . . . . . . . . . . . . . 14
A.4. Modifications between draft-ietf-tram-stun-pmtud-07 and
draft-ietf-tram-stun-pmtud-06 . . . . . . . . . . . . . . 14
A.5. Modifications between draft-ietf-tram-stun-pmtud-06 and
draft-ietf-tram-stun-pmtud-05 . . . . . . . . . . . . . . 14
A.6. Modifications between draft-ietf-tram-stun-pmtud-05 and
draft-ietf-tram-stun-pmtud-04 . . . . . . . . . . . . . . 15
A.7. Modifications between draft-ietf-tram-stun-pmtud-04 and
draft-ietf-tram-stun-pmtud-03 . . . . . . . . . . . . . . 15
A.8. Modifications between draft-ietf-tram-stun-pmtud-03 and
draft-ietf-tram-stun-pmtud-02 . . . . . . . . . . . . . . 15
A.9. Modifications between draft-ietf-tram-stun-pmtud-02 and
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 2]
Internet-Draft STUN PMTUD September 2018
draft-ietf-tram-stun-pmtud-01 . . . . . . . . . . . . . . 16
A.10. Modifications between draft-ietf-tram-stun-pmtud-01 and
draft-ietf-tram-stun-pmtud-00 . . . . . . . . . . . . . . 16
A.11. Modifications between draft-ietf-tram-stun-pmtud-00 and
draft-petithuguenin-tram-stun-pmtud-01 . . . . . . . . . 16
A.12. Modifications between draft-petithuguenin-tram-stun-
pmtud-01 and draft-petithuguenin-tram-stun-pmtud-00 . . . 16
A.13. Modifications between draft-petithuguenin-tram-stun-
pmtud-00 and draft-petithuguenin-behave-stun-pmtud-03 . . 16
A.14. Modifications between draft-petithuguenin-behave-stun-
pmtud-03 and draft-petithuguenin-behave-stun-pmtud-02 . . 16
A.15. Modifications between draft-petithuguenin-behave-stun-
pmtud-02 and draft-petithuguenin-behave-stun-pmtud-01 . . 17
A.16. Modifications between draft-petithuguenin-behave-stun-
pmtud-01 and draft-petithuguenin-behave-stun-pmtud-00 . . 17
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
The Packetization Layer Path MTU Discovery (PMTUD) specification
[RFC4821] describes a method to discover the Path MTU but does not
describe a practical protocol to do so with UDP.
Many UDP-based protocols do not implement the Path MTU discovery
mechanism described in [RFC4821]. These protocols can make use of
the probing mechanisms described in this document instead of
designing their own adhoc extension. These probing mechanisms are
implemented with Session Traversal Utilities for NAT (STUN), but
their usage is not limited to STUN-based protocols.
The STUN usage defined in this document for Path MTU Discovery
(PMTUD) between a client and a server permits proper operations of
UDP-based applications in the network. It also simplifies
troubleshooting and has multiple other applications across a wide
variety of technologies.
Complementary techniques can be used to discover additional network
characteristics, such as the network path (using the STUN Traceroute
mechanism described in [I-D.martinsen-tram-stuntrace]) and bandwidth
availability (using the mechanism described in
[I-D.martinsen-tram-turnbandwidthprobe]).
2. Overview of Operations
This section is meant to be informative only. It is not intended as
a replacement for [RFC4821].
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 3]
Internet-Draft STUN PMTUD September 2018
A UDP endpoint that uses this specification to discover the Path MTU
over UDP and knows that the endpoint it is communicating with also
supports this specification can choose to use either the Simple
Probing mechanism (as described in Section 4.1) or the Complete
Probing mechanism (as described in Section 4.2). The selection of
which Probing Mechanism to use is dependent on performance and
security and complexity trade-offs.
If the Simple Probing mechanism is chosen, then the Client initiates
Probe transactions, as shown in Figure 1, which increase in size
until transactions timeout, indicating that the Path MTU has been
exceeded. It then uses that information to update the Path MTU.
Client Server
| |
| Probe Request |
|---------------->|
| |
| Probe Response |
|<----------------|
| |
Figure 1: Simple Probing Example
If the Complete Probing mechanism (as described in Section 4.2) is
chosen, then the Client sends Probe Indications of various sizes (as
specified in [RFC4821]) interleaved with UDP packets sent by the UDP
protocol. The Client then sends a Report Request for the ordered
list of identifiers for the UDP packets and Probe Indications
received by the Server. The Client then compares the list returned
in the Report Response with its own list of identifiers for the UDP
packets and Probe Indications it sent. The Client then uses that
comparison to find which Probe Indications were dropped by the
network as a result of their size. It then uses that information to
update the Path MTU.
Because of the possibility of amplification attack, the Complete
Probing mechanism must be authenticated. Particular care must be
taken to prevent amplification when an external mechanism is used to
trigger the Complete Probing mechanism.
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 4]
Internet-Draft STUN PMTUD September 2018
Client Server
| UDP Packet |
|------------------>|
| |
| UDP Packet |
|------------------>|
| |
| Probe Indication |
|------------------>|
| |
| UDP Packet |
|------------------>|
| |
| Probe Indication |
|------------------>|
| |
| Report Request |
|------------------>|
| Report Response |
|<------------------|
| |
Figure 2: Complete Probing Example
3. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119][RFC8174] when, and only when, they appear in all
capitals, as shown here.
4. Probing Mechanisms
The Probing mechanism is used to discover the Path MTU in one
direction only, from the client to the server.
Two Probing mechanisms are described, a Simple Probing mechanism and
a more complete mechanism that can converge quicker and find an
appropriate PMTU in the presence of congestion. Additionally, the
Simple Probing mechanism does not require authentication except where
used as an implicit signaling mechanism, whereas the complete
mechanism does.
Implementations supporting this specification MUST implement the
server side of both the Simple Probing mechanism (Section 4.1) and
the Complete Probing mechanism (Section 4.2).
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 5]
Internet-Draft STUN PMTUD September 2018
Implementations supporting this specification MUST implement the
client side of the Complete Probing mechanism. They MAY implement
the client side of the Simple Probing mechanism.
4.1. Simple Probing Mechanism
The Simple Probing mechanism is implemented by sending a Probe
Request with a PADDING [RFC5780] attribute over UDP with the DF bit
set in the IP header. A router on the path to the server can reject
this request with an ICMP message or drop it.
4.1.1. Sending a Probe Request
A client forms a Probe Request by using the Probe Method and
following the rules in Section 7.1 of [RFC5389].
The Probe transaction MUST be authenticated if the Simple Probing
mechanism is used in conjunction with the Implicit Probing Support
mechanism described in Section 5.2. If not, the Probe transaction
MAY be authenticated.
The client adds a PADDING [RFC5780] attribute with a length that,
when added to the IP and UDP headers and the other STUN components,
is equal to the Selected Probe Size, as defined in [RFC4821]
Section 7.3. The client MUST add the FINGERPRINT attribute so the
STUN messages are disambiguated from the other protocol packets.
Then the client sends the Probe Request to the server over UDP with
the DF bit set. For the purpose of this transaction, the Rc
parameter specified in Section 7.2.1 of [RFC5389] is set to 3. The
initial value for RTO stays at 500 ms.
A client MUST NOT send a probe if it does not have knowledge that the
server supports this specification. This is done either by external
signalling or by a mechanism specific to the UDP protocol to which
PMTUD capabilities are added or by one of the mechanisms specified in
Section 5.
4.1.2. Receiving a Probe Request
A server receiving a Probe Request MUST process it as specified in
[RFC5389].
The server then creates a Probe Response. The server MUST add the
FINGERPRINT attribute so the STUN messages are disambiguated from the
other protocol packets. The server then sends the response to the
client.
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 6]
Internet-Draft STUN PMTUD September 2018
4.1.3. Receiving a Probe Response
A client receiving a Probe Response MUST process it as specified in
[RFC5389]. If a response is received this is interpreted as a Probe
Success, as defined in [RFC4821] Section 7.6.1. If an ICMP packet
"Fragmentation needed" is received then this is interpreted as a
Probe Failure, as defined in [RFC4821] Section 7.6.2. If the Probe
transaction times out, then this is interpreted as a Probe
Inconclusive, as defined in [RFC4821] Section 7.6.4.
4.2. Complete Probing Mechanism
The Complete Probing mechanism is implemented by sending one or more
Probe Indications with a PADDING attribute over UDP with the DF bit
set in the IP header followed by a Report Request to the same server.
A router on the path to the server can reject this Indication with an
ICMP message or drop it. The server keeps a chronologically ordered
list of identifiers for all packets received (including retransmitted
packets) and sends this list back to the client in the Report
Response. The client analyzes this list to find which packets were
not received. Because UDP packets do not contain an identifier, the
Complete Probing mechanism needs a way to identify each packet
received.
Some application layer protocols may already have a way of
identifying each individual UDP packet, in which case these
identifiers SHOULD be used in the IDENTIFIERS attribute of the Report
Response. While there are other possible packet identification
schemes, this document describes two different ways to identify a
specific packet when no application layer protocol-specific
identification mechanism is available.
In the first packet identification mechanism, the server computes a
checksum over each packet received and sends back to the sender the
list of checksums ordered chronologically. The client compares this
list to its own list of checksums.
In the second packet identification mechanism, the client prepends
the UDP data with a header that provides a sequence number. The
server sends back the chronologically ordered list of sequence
numbers received that the client then compares with its own list.
4.2.1. Sending the Probe Indications and Report Request
A client forms a Probe Indication by using the Probe Method and
following the rules in [RFC5389] Section 7.1. The client adds to the
Probe Indication a PADDING attribute with a size that, when added to
the IP and UDP headers and the other STUN components, is equal to the
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 7]
Internet-Draft STUN PMTUD September 2018
Selected Probe Size, as defined in [RFC4821] Section 7.3. If the
authentication mechanism permits it, then the Indication MUST be
authenticated. The client MUST add the FINGERPRINT attribute so the
STUN messages are disambiguated from the other protocol packets.
Then the client sends the Probe Indication to the server over UDP
with the DF bit set.
Then the client forms a Report Request by following the rules in
[RFC5389] Section 7.1. The Report transaction MUST be authenticated
to prevent amplification attacks. The client MUST add the
FINGERPRINT attribute so the STUN messages are disambiguated from the
other protocol packets.
Then the client waits half the RTO after sending the last Probe
Indication and then sends the Report Request to the server over UDP.
4.2.2. Receiving an ICMP Packet
If an ICMP packet "Fragmentation needed" is received then this is
interpreted as a Probe Failure, as defined in [RFC4821] Section 7.5.
4.2.3. Receiving a Probe Indication and Report Request
A server supporting this specification will keep the identifiers of
all packets received in a chronologically ordered list. The packets
that are to be associated to a list are selected according to
Section 5.2 of [RFC4821]. The same identifier can appear multiple
times in the list because of retransmissions. The maximum size of
this list is calculated such that when the list is added to the
Report Response, the total size of the packet does not exceed the
unknown Path MTU, as defined in [RFC5389] Section 7.1. Older
identifiers are removed when new identifiers are added to a list that
is already full.
A server receiving a Report Request MUST process it as specified in
[RFC5389].
The server creates a Report Response and adds an IDENTIFIERS
attribute that contains the chronologically ordered list of all
identifiers received so far. The server MUST add the FINGERPRINT
attribute. The server then sends the response to the client.
The exact content of the IDENTIFIERS attribute depends on what type
of identifiers have been chosen for the protocol. Each protocol
adding PMTUD capabilities as specified by this specification MUST
describe the format of the contents of the IDENTIFIERS attribute,
unless it is using one of the formats described in this
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 8]
Internet-Draft STUN PMTUD September 2018
specification. See Section 6.1 for details about the IDENTIFIERS
attribute.
4.2.4. Receiving a Report Response
A client receiving a Report Response processes it as specified in
[RFC5389]. If the response IDENTIFIERS attribute contains the
identifier of the Probe Indication, then this is interpreted as a
Probe Success for this probe, as defined in [RFC4821] Section 7.5.
If the Probe Indication identifier cannot be found in the Report
Response, this is interpreted as a Probe Failure, as defined in
[RFC4821] Section 7.5. If the Probe Indication identifier cannot be
found in the Report Response but identifiers for other packets sent
before or after the Probe Indication can all be found, this is
interpreted as a Probe Failure as defined in [RFC4821] Section 7.5.
If the Report Transaction times out, this is interpreted as a Full-
Stop Timeout, as defined in [RFC4821] Section 3.
4.2.5. Using Checksums as Packet Identifiers
When using a checksum as a packet identifier, the client calculates
the checksum for each packet sent over UDP that is not a STUN Probe
Indication or Request and keeps this checksum in a chronologically
ordered list. The client also keeps the checksum of the STUN Probe
Indication or Request sent in that same chronologically ordered list.
The algorithm used to calculate the checksum is similar to the
algorithm used for the FINGERPRINT attribute (i.e., the CRC-32 of the
payload XOR'ed with the 32-bit value 0x5354554e [ITU.V42.2002]).
For each STUN Probe Indication or Request, the server retrieves the
STUN FINGERPRINT value. For all other packets, the server calculates
the checksum as described above. It puts these FINGERPRINT and
checksum values in a chronologically ordered list that is sent back
in the Report Response.
The contents of the IDENTIFIERS attribute is a list of 4 byte
numbers, each using the same encoding that is used for the contents
of the FINGERPRINT attribute.
It could have been possible to use the checksum generated in the UDP
checksum for this, but this value is generally not accessible to
applications. Also, sometimes the checksum is not calculated or is
off-loaded to network hardware.
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 9]
Internet-Draft STUN PMTUD September 2018
4.2.6. Using Sequence Numbers as Packet Identifiers
When using sequence numbers, a small header similar to the TURN
ChannelData header is added in front of all packets that are not a
STUN Probe Indication or Request. The sequence number is
monotonically incremented by one for each packet sent. The most
significant bit of the sequence number is always 0. The server
collects the sequence number of the packets sent, or the 4 first
bytes of the transaction ID if a STUN Probe Indication or Request is
sent. In that case, the most significant bit of the 4 first bytes is
set to 1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Channel Number | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
/ Application Data /
/ /
| |
| +-------------------------------+
| |
+-------------------------------+
The Channel Number is always 0xFFFF. The header values are encoded
using network order.
The contents of the IDENTIFIERS attribute is a chronologically
ordered list of 4 byte numbers, each containing either a sequence
number, if the packet was not a STUN Probe Indication or Request, or
the 4 first bytes of the transaction ID, with the most significant
bit forced to 1, if the packet is a STUN Probe Indication or Request.
5. Probe Support Signaling Mechanisms
The PMTUD mechanism described in this document is intended to be used
by any UDP-based protocols that do not have built-in PMTUD
capabilities, irrespective of whether those UDP-based protocols are
STUN-based or not. So the manner in which a specific protocol
discovers that it is safe to send PMTUD probes is largely dependent
on the details of that specific protocol, with the exception of the
Implicit Mechanism described below, which applies to any protocol.
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 10]
Internet-Draft STUN PMTUD September 2018
5.1. Explicit Probe Support Signaling Mechanism
Some of these mechanisms can use a separate signalling mechanism (for
instance, an SDP attribute in an Offer/Answer exchange [RFC3264]), or
an optional flag that can be set in the protocol that is augmented
with PMTUD capabilities. STUN Usages that can benefit from PMTUD
capabilities can signal in-band that they support probing by
inserting a PMTUD-SUPPORTED attribute in some STUN methods. The
decision of which methods support this attribute is left to each
specific STUN Usage.
UDP-based protocols that want to use any of these mechanisms,
including the PMTUD-SUPPORTED attribute, to signal PMTUD capabilities
MUST ensure that it cannot be used to launch an amplification attack.
An amplification attack can be prevented using techniques such as:
o Authentication, where the source of the packet and the destination
share a secret.
o 3 way handshake with some form of unpredictable cookie.
o Make sure that the total size of the traffic potentially generated
is lower than the size of the request that generated it.
5.2. Implicit Probe Support Signaling Mechanism
As a result of the fact that all endpoints implementing this
specification are both clients and servers, a Probe Request or
Indication received by an endpoint acting as a server implicitly
signals that this server can now act as a client and MAY send a Probe
Request or Indication to probe the Path MTU in the reverse direction
toward the former client, that will now be acting as a server.
The Probe Request or Indication that are used to implicitly signal
probing support in the reverse direction MUST be authenticated to
prevent amplification attacks.
6. STUN Attributes
6.1. IDENTIFIERS
The IDENTIFIERS attribute carries a chronologically ordered list of
UDP packet identifiers.
While Section 4.2.5 and Section 4.2.6 describe two possible methods
for acquiring and formatting the identifiers used for this purpose,
ultimately each protocol has to define how these identifiers are
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 11]
Internet-Draft STUN PMTUD September 2018
acquired and formatted. Therefore, the contents of the IDENTIFIERS
attribute is opaque.
6.2. PMTUD-SUPPORTED
The PMTUD-SUPPORTED attribute indicates that its sender supports this
specification. This attribute has no value part and thus the
attribute length field is 0.
7. Security Considerations
The PMTUD mechanism described in this document, when used without the
signalling mechanism described in Section 5.1, does not introduce any
specific security considerations beyond those described in [RFC4821].
The attacks described in Section 11 of [RFC4821] apply equally to the
mechanism described in this document.
The amplification attacks introduced by the signalling mechanism
described in Section 5.1 can be prevented by using one of the
techniques described in that section.
The Simple Probing mechanism may be used without authentication
because this usage by itself cannot trigger an amplification attack
as the Probe Response is smaller than the Probe Request. An
unauthenticated Simple Probing mechanism cannot be used in
conjunction with the Implicit Probing Support Signaling mechanism in
order to prevent amplification attacks.
8. IANA Considerations
This specification defines two new STUN methods and two new STUN
attributes.
8.1. New STUN Methods
IANA is requested to add the following methods to the STUN Method
Registry:
0xXXX : Probe
0xXXX : Report
See Sections Section 4.1 and Section 4.2 for the semantics of these
new methods.
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 12]
Internet-Draft STUN PMTUD September 2018
8.2. New STUN Attributes
IANA is requested to add the following attributes to the STUN Method
Registry:
Comprehension-required range (0x0000-0x7FFF):
0xXXXX: IDENTIFIERS
Comprehension-optional range (0x8000-0xFFFF)
0xXXXX: PMTUD-SUPPORTED
This IDENTIFIERS STUN attribute is defined in Section 6.1, the PMTUD-
SUPPORTED STUN attribute is defined in Section 6.2.
9. References
9.1. Normative References
[ITU.V42.2002]
International Telecommunications Union, "Error-correcting
Procedures for DCEs Using Asynchronous-to-Synchronous
Conversion", ITU-T Recommendation V.42, 2002.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
<http://www.rfc-editor.org/info/rfc4821>.
[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
DOI 10.17487/RFC5389, October 2008,
<http://www.rfc-editor.org/info/rfc5389>.
[RFC5780] MacDonald, D. and B. Lowekamp, "NAT Behavior Discovery
Using Session Traversal Utilities for NAT (STUN)",
RFC 5780, DOI 10.17487/RFC5780, May 2010,
<http://www.rfc-editor.org/info/rfc5780>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <http://www.rfc-editor.org/info/rfc8174>.
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 13]
Internet-Draft STUN PMTUD September 2018
9.2. Informative References
[I-D.martinsen-tram-stuntrace]
Martinsen, P. and D. Wing, "STUN Traceroute", draft-
martinsen-tram-stuntrace-01 (work in progress), June 2015.
[I-D.martinsen-tram-turnbandwidthprobe]
Martinsen, P., Andersen, T., Salgueiro, G., and M. Petit-
Huguenin, "Traversal Using Relays around NAT (TURN)
Bandwidth Probe", draft-martinsen-tram-
turnbandwidthprobe-00 (work in progress), May 2015.
[RFC3264] Rosenberg, J. and H. Schulzrinne, "An Offer/Answer Model
with Session Description Protocol (SDP)", RFC 3264,
DOI 10.17487/RFC3264, June 2002,
<http://www.rfc-editor.org/info/rfc3264>.
Appendix A. Release Notes
This section must be removed before publication as an RFC.
A.1. Modifications between draft-ietf-tram-stun-pmtud-10 and draft-
ietf-tram-stun-pmtud-09
o Modifications following reviews for gen-art (Roni Even) and secdir
(Carl Wallace).
A.2. Modifications between draft-ietf-tram-stun-pmtud-09 and draft-
ietf-tram-stun-pmtud-08
o Add 3 ways of preventing amplification attacks.
A.3. Modifications between draft-ietf-tram-stun-pmtud-08 and draft-
ietf-tram-stun-pmtud-07
o Updates following Spencer's review.
A.4. Modifications between draft-ietf-tram-stun-pmtud-07 and draft-
ietf-tram-stun-pmtud-06
o Updates following Shepherd review.
A.5. Modifications between draft-ietf-tram-stun-pmtud-06 and draft-
ietf-tram-stun-pmtud-05
o Nits.
o Restore missing changelog for previous version.
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 14]
Internet-Draft STUN PMTUD September 2018
A.6. Modifications between draft-ietf-tram-stun-pmtud-05 and draft-
ietf-tram-stun-pmtud-04
o Modifications following Brandon Williams review.
A.7. Modifications between draft-ietf-tram-stun-pmtud-04 and draft-
ietf-tram-stun-pmtud-03
o Modifications following Simon Perreault and Brandon Williams
reviews.
A.8. Modifications between draft-ietf-tram-stun-pmtud-03 and draft-
ietf-tram-stun-pmtud-02
o Add new Overview of Operations section with ladder diagrams.
o Authentication is mandatory for the Complete Probing mechanism,
optional for the Simple Probing mechanism.
o All the ICE specific text moves to a separate draft to be
discussed in the ICE WG.
o The TURN usage is removed because probing between a TURN server
and TURN client is not useful.
o Any usage of PMTUD-SUPPORTED or other signaling mechanisms
(formerly knows as discovery mechanisms) must now be
authenticated.
o Both probing mechanisms are MTI in the server, the complete
probing mechanism is MTI in the client.
o Make clear that stopping after 3 retransmission is done by
changing the STUN parameter.
o Define the format of the attributes.
o Make clear that the specification is for any UDP protocol that
does not already have PMTUD capabilities, not just STUN based
protocols.
o Change the default delay to send the Report Request to 250 ms
after the last Indication if the RTO is unknown.
o Each usage of this specification must the format of the
IDENTIFIERS attribute contents.
o Better define the implicit signaling mechanism.
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 15]
Internet-Draft STUN PMTUD September 2018
o Extend the Security Consideration section.
o Tons of nits.
A.9. Modifications between draft-ietf-tram-stun-pmtud-02 and draft-
ietf-tram-stun-pmtud-01
o Cleaned up references.
A.10. Modifications between draft-ietf-tram-stun-pmtud-01 and draft-
ietf-tram-stun-pmtud-00
o Added Security Considerations Section.
o Added IANA Considerations Section.
A.11. Modifications between draft-ietf-tram-stun-pmtud-00 and draft-
petithuguenin-tram-stun-pmtud-01
o Adopted by WG - Text unchanged.
A.12. Modifications between draft-petithuguenin-tram-stun-pmtud-01 and
draft-petithuguenin-tram-stun-pmtud-00
o Moved some Introduction text to the Probing Mechanism section.
o Added cross-reference to the other two STUN troubleshooting
mechanism drafts.
o Updated references.
o Added Gonzalo Salgueiro as co-author.
A.13. Modifications between draft-petithuguenin-tram-stun-pmtud-00 and
draft-petithuguenin-behave-stun-pmtud-03
o General refresh for republication.
A.14. Modifications between draft-petithuguenin-behave-stun-pmtud-03
and draft-petithuguenin-behave-stun-pmtud-02
o Changed author address.
o Changed the IPR to trust200902.
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 16]
Internet-Draft STUN PMTUD September 2018
A.15. Modifications between draft-petithuguenin-behave-stun-pmtud-02
and draft-petithuguenin-behave-stun-pmtud-01
o Defined checksum and sequential numbers as possible packet
identifiers.
o Updated the reference to RFC 5389
o The FINGERPRINT attribute is now mandatory.
o Changed the delay between Probe indication and Report request to
be RTO/2 or 50 milliseconds.
o Added ICMP packet processing.
o Added Full-Stop Timeout detection.
o Stated that Binding request with PMTUD-SUPPORTED does not start
the PMTUD process if already started.
A.16. Modifications between draft-petithuguenin-behave-stun-pmtud-01
and draft-petithuguenin-behave-stun-pmtud-00
o Removed the use of modified STUN transaction but shorten the
retransmission for the simple probing mechanism.
o Added a complete probing mechanism.
o Removed the PADDING-RECEIVED attribute.
o Added release notes.
Acknowledgements
Thanks to Eilon Yardeni, Geir Sandbakken, Paal-Erik Martinsen,
Tirumaleswar Reddy, Ram Mohan R, Simon Perreault, Brandon Williams,
Tolga Asveren, Spencer Dawkins, Carl Wallace, and Roni Even for their
review comments, suggestions and questions that helped to improve
this document.
Special thanks to Dan Wing, who supported this document since its
first publication back in 2008.
Authors' Addresses
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 17]
Internet-Draft STUN PMTUD September 2018
Marc Petit-Huguenin
Impedance Mismatch
Email: marc@petit-huguenin.org
Gonzalo Salgueiro
Cisco Systems, Inc.
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
United States
Email: gsalguei@cisco.com
Petit-Huguenin & SalgueirExpires March 21, 2019 [Page 18]