One document matched: draft-morton-ippm-more-twamp-01.xml
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<rfc category="std" docName="draft-morton-ippm-more-twamp-01" ipr="full3978">
<front>
<title abbrev="TWAMP Extensions">More Features for TWAMP</title>
<author fullname="Al Morton" initials="A." surname="Morton">
<organization>AT&T Labs</organization>
<address>
<postal>
<street>200 Laurel Avenue South</street>
<city>Middletown,</city>
<region>NJ</region>
<code>07748</code>
<country>USA</country>
</postal>
<phone>+1 732 420 1571</phone>
<facsimile>+1 732 368 1192</facsimile>
<email>acmorton@att.com</email>
<uri>http://home.comcast.net/~acmacm/</uri>
</address>
</author>
<author fullname="Kaynam Hedayat" initials="K." surname="Hedayat">
<organization>Brix Networks</organization>
<address>
<postal>
<street>285 Mill Road</street>
<city>Chelmsford</city>
<region>MA</region>
<code>01824</code>
<country>USA</country>
</postal>
<phone>+1</phone>
<facsimile>+1</facsimile>
<email>khedayat@brixnet.com</email>
<uri>http://www.brixnet.com/</uri>
</address>
</author>
<date day="6" month="July" year="2008" />
<abstract>
<t>The IETF is completing its work on TWAMP - the Two-Way Active
Measurement Protocol. This memo describes additional features for TWAMP,
essentially the ability to use different security modes in the
TWAMP-Control and TWAMP-Test protocols.</t>
</abstract>
<note title="Requirements Language">
<t>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 <xref
target="RFC2119">RFC 2119</xref>.</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>The IETF is completing its work on TWAMP - the Two-Way Active
Measurement Protocol <xref target="I-D.ietf-ippm-twamp"></xref>, which
is an extension to the One-way Active Measurement Protocol, OWAMP <xref
target="RFC4656"></xref>. The TWAMP specification gathered wide review
as it approached completion, and the by-products were several
recommendations for new features in TWAMP. There are a growing number
TWAMP implementations at present, and wide-spread usage is expected.
There are even devices emerging that test implementations for protocol
compliance.</t>
<t>This memo describes additional features for TWAMP, such as the
ability to use different security modes in the TWAMP-Control and
TWAMP-Test protocols.</t>
<t>The relationship between this memo and the TWAMP is intended to be an
update to the TWAMP RFC when published.</t>
</section>
<section title="Purpose and Scope">
<t>The purpose of this memo is to specify additional functions and
features for TWAMP <xref target="I-D.ietf-ippm-twamp"></xref>. The
features and extensions were vetted before adoption in this memo.</t>
<t>The scope of the memo is limited to specifications of the following
features:</t>
<t><list style="numbers">
<t>Extension of the modes of operation through assignment of new
values in the Mode field (see section 3.1 of <xref
target="RFC4656"></xref>), while retaining backward compatibility
with TWAMP <xref target="I-D.ietf-ippm-twamp"></xref>
implementations. These values add the ability to use different
security modes in the TWAMP-Control and TWAMP-Test protocols. The
motivation for this extension is to permit the low packet rate
TWAMP-Control protocol to utilize a stronger mode of integrity
protection than that used in the TWAMP-Test protocol.</t>
</list>(other items may be added)</t>
</section>
<section title="TWAMP Control Extensions">
<t>TWAMP-Control protocol is a derivative of the OWAMP-Control protocol,
and provides two-way measurement capability. All TWAMP Control messages
are similar in format and follow similar guidelines to those defined in
section 3 of <xref target="RFC4656"></xref> with the exceptions
described in TWAMP <xref target="I-D.ietf-ippm-twamp"></xref>, and in
the following sections.</t>
<t>All OWAMP-Control messages apply to TWAMP-Control, except for the
Fetch Session command.</t>
<section title="Extended Connection Setup">
<t>TWAMP connection establishment follows the same procedure defined
in section 3.1 of <xref target="RFC4656"></xref>. The extended modes
assign three new bit positions (and values) to allow the Test protocol
security mode to differ from the Control protocol mode. With this
extension, the complete set of TWAMP values are as follows:</t>
<t><figure>
<preamble></preamble>
<artwork><![CDATA[Value Description Reference/Explanation
0 Reserved
1 Unauthenticated RFC4656, Section 3.1
2 Authenticated RFC4656, Section 3.1
4 Encrypted RFC4656, Section 3.1
8 Unauth. TEST protocol, new bit position (3)
Auth. CONTROL
16 Unauth. TEST protocol, new bit position (4)
Encrypted CONTROL
32 Auth. TEST protocol, new bit position (5)
Encrypted CONTROL ]]></artwork>
<postamble></postamble>
</figure></t>
<t>In the original OWAMP mode field, setting bit positions 0, 1 or 2
indicated the security mode of the Control protocol, and the Test
protocol inherited the same mode (see section 4 of <xref
target="RFC4656"></xref>). In this extension to TWAMP, setting a
higher mode field bit position (3, 4 or 5) SHALL discontinue the
inheritance of the security mode in the Test protocol, and each
protocol’s mode SHALL be specified explicitly. When the desired
TWAMP Test protocol mode is identical to the Control Session mode, the
corresponding mode bit (position 0, 1 or 2) SHALL be set. The table
below gives the various combinations that are now permissible in
TWAMP, where the Test protocol may use one of the modes in each column
corresponding to a Control mode.</t>
<t><figure>
<preamble></preamble>
<artwork><![CDATA[----------------------------------------------------
Protocol | Permissible Mode Combinations
----------------------------------------------------
Control | Unauth. | Auth. | Encrypted
----------------------------------------------------
| Unauth. | Unauth. | Unauth.
-------------------------------------------
Test | | Auth. | Auth.
-------------------------------------------
| | | Encrypted
----------------------------------------------------]]></artwork>
<postamble></postamble>
</figure></t>
<t>The value of the Modes field sent by the Server is the bit-wise OR
of the mode values that it is willing to support during this session.
Thus, the last six bits of the Modes 32-bit field are used. The first
26 bits MUST be zero. A client conforming to this version of the
specification MUST ignore the values in the first 26 bits of the Modes
value. (This way, the bits are available for future protocol
extensions.)</t>
<t>Other ways in which TWAMP extends OWAMP are described in <xref
target="I-D.ietf-ippm-twamp"></xref>.</t>
</section>
</section>
<section title="Extended TWAMP Test ">
<t>The TWAMP test protocol is similar to the OWAMP <xref
target="RFC4656"></xref> test protocol with the exception that the
Session-Reflector transmits test packets to the Session-Sender in
response to each test packet it receives. TWAMP <xref
target="I-D.ietf-ippm-twamp"></xref> defines two different test packet
formats, one for packets transmitted by the Session-Sender and one for
packets transmitted by the Session-Reflector. As with OWAMP-Test
protocol there are three security modes: unauthenticated, authenticated,
and encrypted. The extension to TWAMP makes it possible to specify these
modes independently from the mode used in the TWAMP-Control
protocol.</t>
<section title="Sender Behavior">
<t>This section describes extensions to the behavior of the TWAMP
Sender.</t>
<section title="Packet Timings">
<t>The Send Schedule is not utilized in TWAMP, and there are no
extensions defined in this memo.</t>
</section>
<section title="Packet Format and Content">
<t>The Session Sender packet format and content follow the same
procedure and guidelines as defined in section 4.1.2 of <xref
target="RFC4656"></xref>, with the following exceptions: <list
style="symbols">
<t>the Send Schedule is not used, and</t>
<t>the support of additional security mode combinations defined
in section 3.1 of this memo.</t>
</list></t>
</section>
</section>
<section title="Reflector Behavior">
<t>The TWAMP Reflector follows the procedures and guidelines in
section 4.2 of <xref target="I-D.ietf-ippm-twamp"></xref>, with the
following extensions:</t>
<t><list style="symbols">
<t>the support of additional security mode combinations defined in
section 3.1 of this memo.</t>
</list></t>
</section>
</section>
<section anchor="Security" title="Security Considerations">
<t>These extended modes of operation permit stronger integrity
protection on the TWAMP-Control protocol while simultaneously
emphasizing accuracy or efficiency on the TWAMP-Test protocol, thus
enhancing overall security when compared to the previous options.</t>
<t>The security considerations that apply to any active measurement of
live networks are relevant here as well. See <xref
target="RFC4656"></xref> and <xref
target="I-D.ietf-ippm-twamp"></xref>.</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>This memo adds three security mode combinations to the OWAMP-Control
specification<xref target="RFC4656"> </xref>, and describes behavior
when the new modes are used. This memo requests creation an IANA
registry for the TWAMP Mode field. This field is a recognized extension
mechanism for TWAMP.</t>
<section title="Registry Specification">
<t>IANA is requested to create a TWAMP-Modes registry. TWAMP-Modes are
specified in TWAMP Server Greeting messages and Set-up Response
messages consistent with section 3.1 of <xref
target="RFC4656"></xref>, and extended by this memo. Modes are
indicated by setting bits in the 32-bit Modes field. Thus, this
registry can contain a total of 32 possible values.</t>
</section>
<section title="Registry Management">
<t>Because the Modes registry can contain only thirty-two values, and
because TWAMP is an IETF protocol, this registry must be updated only
by "IETF Consensus" as specified in <xref target="RFC2434"></xref>(an
RFC documenting registry use that is approved by the IESG). For the
Modes registry, we expect that new features will be assigned using
monotonically increasing bit positions and in the range [0-31] and the
corresponding values, unless there is a good reason to do
otherwise.</t>
</section>
<section title="Experimental Numbers">
<t>No experimental values are currently assigned for the Modes
Registry.</t>
</section>
<section title="Initial Registry Contents">
<t>TWAMP Modes Registry<figure>
<preamble></preamble>
<artwork><![CDATA[Value Description Semantics Definition
0 Reserved
1 Unauthenticated RFC4656, Section 3.1
2 Authenticated RFC4656, Section 3.1
4 Encrypted RFC4656, Section 3.1
8 Unauth. TEST protocol, this document, Section 3.1
Auth. CONTROL
16 Unauth. TEST protocol, this document, Section 3.1
Encrypted CONTROL
32 Auth. TEST protocol, this document, Section 3.1
Encrypted CONTROL ]]></artwork>
<postamble></postamble>
</figure></t>
</section>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The authors would like to thank Len Ciavattone for helpful review and
comments.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
<?rfc include='reference.RFC.4656'?>
<?rfc include='reference.I-D.ietf-ippm-twamp'?>
<?rfc include='reference.RFC.2434'?>
<?rfc ?>
<?rfc ?>
<?rfc ?>
</references>
<references title="Informative References">
<?rfc ?>
<reference anchor="x">
<front>
<title></title>
<author fullname="" surname="">
<organization></organization>
</author>
<date month="" year="" />
</front>
</reference>
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</back>
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