One document matched: draft-morton-ippm-twamp-session-cntrl-00.xml
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<rfc category="std" docName="draft-morton-ippm-twamp-session-cntrl-00"
ipr="full3978">
<front>
<title abbrev="TWAMP Session Control">Independent Session Control Feature
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>
<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 a proposed feature for TWAMP,
intended for discussion in the IP Performance Metrics WG. The feature
gives the sender the ability to start and stop one or more test sessions
using the Session Identifiers.</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>.</t>
<t>This memo describes a new proposed feature for TWAMP, so it can be
discussed and interest to take-up the feature assessed. TWAMP (and
OWAMP) start all previously requested and accepted test sessions at
once. This feature allows the Control-Client to control the test
sessions on the basis of their Session Identifier (SID). The feature
permits a short duration TWAMP test to start (and stop) during a longer
test. For example, this feature permits a specific diagnostic test to
begin if intermediate results indicate that the test is warranted.</t>
<t>This feature requires a Mode bit position assignment and the
assignment of two new TWAMP command numbers (for the augmented Start and
Stop commands).</t>
<t>The relationship between this memo and 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 describe an additional function and
feature for TWAMP <xref target="I-D.ietf-ippm-twamp"></xref>. The
feature needs a clear description so it can be discussed and (hopefully)
adopted in the IP Performance Metrics Charter.</t>
<t>The scope of the memo is currently limited to specifications of the
following features:</t>
<t><list style="numbers">
<t>Extension of the modes of operation through assignment of a new
value in the Mode field to communicate feature capability and use,
the definition of augmented Start Session and Stop Session commands,
and the definition of related procedures for TWAMP entities. The
motivation for this added feature is the ability to start and stop
individual test sessions at will, using a single TWAMP-control
connection.</t>
</list>When new features are discussed and reach consensus, they may
become chartered work items in IETF IPPM (and may appear in a different
memo).</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. TWAMP <xref
target="I-D.ietf-ippm-twamp"></xref> uses the Mode field to identify and
select specific communication capabilities, and this field is a
recognized extension mechanism. The following sections describe one such
extension.</t>
<section title="Connection Setup with Individual Session Control">
<t>TWAMP connection establishment follows the procedure defined in
section 3.1 of <xref target="RFC4656"></xref>. The Individual Session
Control mode requires one new bit position (and value) to identify the
ability of the Server/Session-Reflector to start and stop specific
sessions (according to their Session Identifier, or SID). This new
feature requires an additional TWAMP mode bit assignment 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, draft-...-more-twamp (3)
Auth. CONTROL
16 Unauth. TEST protocol, draft-...-more-twamp (4)
Encrypted CONTROL
32 Auth. TEST protocol, draft-...-more-twamp (5)
Encrypted CONTROL
--------------------------------------------------------
zzz Individual Session this memo, bit position (Z)
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 the <xref
target="I-D.morton-ippm-more-twamp"></xref> proposal, bit positions
(3, 4 or 5) discontinue the inheritance of the security mode in the
Test protocol.</t>
<t>The Server sets the new bit position (possibly bit 8) in the Server
Greeting message to indicate its capabilities and willingness to
control sessions on an individual basis if desired.</t>
<t>If the Control-Client intends to control sessions on an individual
basis, it MUST set the mode bit corresponding to that mode in the
Setup Response message.</t>
</section>
<section title="Start-Sessions Command with Session Control">
<t>Having requested one or more test sessions and received affirmative
Accept-Session responses, an OWAMP client MAY start the execution of
the requested test sessions by sending a Start-Sessions message to the
server.</t>
<t>The format of this message is as follows:</t>
<t><figure>
<preamble></preamble>
<artwork><![CDATA[ 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 7 | |
+-+-+-+-+-+-+-+-+ +
| MBZ (7 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Sessions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| First SID (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| remaining SIDs (16 octets each) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+]]></artwork>
<postamble></postamble>
</figure></t>
<t>The Number of sessions field indicates the count of sessions that
this Start command applies to. The SID is as defined in OWAMP (and
TWAMP) section 3.5 <xref target="RFC4656"></xref>.</t>
<t>The Server MUST respond with a Start-Ack message (which SHOULD be
sent as quickly as possible). Start-Ack messages have the format
defined in section 3.7 of <xref target="RFC4656"></xref>.</t>
<t>The Control Client MUST NOT send a subsequent Start Sessions
command until an outstanding message is acknowledged with a Start-Ack
message.</t>
</section>
<section title="Stop-Sessions Command with Session Control">
<t>The Stop-Sessions command can only be issued by the Control-Client.
The message MUST contain at least one SID. The message is terminated
with a single block HMAC, to complete the Stop-Sessions Command.</t>
<t>Thus, the TWAMP Stop-Sessions command for individual session
control is constructed as follows:</t>
<t><figure>
<preamble></preamble>
<artwork><![CDATA[ 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 8 | Accept | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Sessions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| First SID (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| remaining SIDs (16 octets each) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
<postamble></postamble>
</figure></t>
<t>The Number of sessions field indicates the count of sessions that
this Stop command applies to. The SID is as defined in OWAMP (and
TWAMP) section 3.5 <xref target="RFC4656"></xref>.</t>
</section>
<section title="SERVWAIT Timer Operation">
<t>Section 3.1 of <xref target="I-D.ietf-ippm-twamp"></xref> describes
the operation of the optional SERVWAIT timer. In normal TWAMP
operation, the Server suspends monitoring the SERVWAIT timer while
test sessions are in progress. When the Individual Session Control
feature is utilized, this suspension is extended to cover the time
when ANY test session is in progress. </t>
<t>Thus, the Server SHALL suspend monitoring control connection
activity after receiving any Start-Sessions command, and SHALL resume
after receiving a Stop-Sessions command for all corresponding SIDs
(and no test sessions are in-progress).</t>
</section>
<section title="Additional considerations">
<t>The value of the Modes field sent by the Server (in the Server
Greeting message) is the bit-wise OR of the mode values that it is
willing to support during this session.</t>
<t>If this feature is adopted, the last seven bits of the Modes 32-bit
field are used. The first 25 bits MUST be zero. A client conforming to
this version of the specification MUST ignore the values in the first
25 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="TWAMP Test with Individual Session Control">
<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. Unauthenticated mode has one test packet format, while
authenticated and encrypted modes use another (common) format.</t>
<section title="Sender Behavior">
<t>The individual session control feature requires that the sender
MUST manage test sessions according to their SID. Otherwise, the
sender behavior is as describe in section 4.1 of <xref
target="I-D.ietf-ippm-twamp"></xref>.</t>
</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 additional functions required by this feature:</t>
<t><list style="symbols">
<t>The session reflector MUST manage test sessions according to
their SID.</t>
<t>Packets for a specific session/SID not received within the
Timeout (following the Stop-Session command) MUST be ignored by
the Reflector. The Session-Reflector MUST NOT generate a test
packet to the Session-Sender for packets that are ignored.</t>
<t>If the optional REFWAIT timer is implemented, it SHOULD be
enforced when any test session is in-progress (started and not
stopped).</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 the security considerations
in<xref target="RFC4656"></xref> and <xref
target="I-D.ietf-ippm-twamp"></xref>.</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>This memo requests assignment of one mode bit position/value to the
IANA registry for the TWAMP Mode field, and describes behavior when the
new mode is used. This field is a recognized extension mechanism for
TWAMP.</t>
<t>This memo also requests assignment of two command numbers in the
TWAMP-Control Command Number registry, and describes the use of the new
commands. The command number field is a recognized extension mechanism
for TWAMP.</t>
<section title="Registry Specification">
<t>IANA has created a TWAMP-Modes registry (as requested in <xref
target="I-D.morton-ippm-more-twamp"></xref>). TWAMP-Modes are
specified in TWAMP Server Greeting messages and Set-up Response
messages, as described in section 3.1 of <xref
target="I-D.ietf-ippm-twamp"></xref>, 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>
<t>IANA has also created a TWAMP-Control Command Number registry.
TWAMP-Control commands are specified by the first octet in
TWAMP-Control messages as specified in section 3.5 of <xref
target="I-D.ietf-ippm-twamp"></xref>, and augmented by this memo. This
registry may contain sixteen possible values.</t>
</section>
<section title="Registry Management">
<t>Because the TWAMP-Control Command Number registry can contain only
sixteen values, TWAMP-Modes can only contain thirty-two values, and
because TWAMP is an IETF protocol, these registries 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). Management of these registries is described in
section 8.2 of <xref target="I-D.ietf-ippm-twamp"></xref> and <xref
target="I-D.morton-ippm-more-twamp"></xref>.</t>
<t>This memo proposes assignment of values 7 and 8.</t>
</section>
<section title="Experimental Numbers">
<t>One experimental value has been assigned in the TWAMP-Control
Command Number registry.</t>
<t>No additional experimental values are assigned in the TWAMP-Modes
registry.</t>
</section>
<section title="Registry Contents">
<t>TWAMP-Control Command Number Registry<figure>
<preamble></preamble>
<artwork><![CDATA[Value Description Semantics Definition
0 Reserved
1 Forbidden
2 Start-Sessions RFC4656, Section 3.7
3 Stop-Sessions RFC4656, Section 3.8
4 Reserved
5 Request-TW-Session draft-ietf-ippm-twamp, Section 3.5
6 Experimentation draft-ietf-ippm-twamp, Section 8.3
------------------------------------------------------------------
7 Start-Sessions with this memo, Section 3.2
Individ. Session Cntrl.
8 Stop-Sessions with this memo, Section 3.3
Individ. Session Cntrl.
]]></artwork>
<postamble></postamble>
</figure></t>
<t>TWAMP-Modes Registry<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, draft-...-more-twamp (3)
Auth. CONTROL
16 Unauth. TEST protocol, draft-...-more-twamp (4)
Encrypted CONTROL
32 Auth. TEST protocol, draft-...-more-twamp (5)
Encrypted CONTROL
--------------------------------------------------------
zzz Individual Session this memo, Section 3.1
Control bit position (Z)]]></artwork>
<postamble></postamble>
</figure></t>
</section>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The author would like to thank Murtaza Chiba for suggesting this
feature.</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 include='reference.I-D.morton-ippm-more-twamp'?>
<?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>
</references>
</back>
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