One document matched: draft-ietf-ippm-twamp-session-cntrl-00.xml
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<rfc category="std" docName="draft-ietf-ippm-twamp-session-cntrl-00"
ipr="full3978">
<front>
<title abbrev="TWAMP Session Control">Individual 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>
<author fullname="Murtaza Chiba" initials="M." surname="Chiba">
<organization>Cisco Systems</organization>
<address>
<postal>
<street></street>
<city></city>
<region></region>
<code></code>
<country>USA</country>
</postal>
<phone>+1</phone>
<facsimile>+1</facsimile>
<email>mchiba@cisco.com</email>
<uri></uri>
</address>
</author>
<date day="26" month="October" year="2008" />
<abstract>
<t>The IETF has completed its work on the core specification of TWAMP -
the Two-Way Active Measurement Protocol. This memo describes a new
feature for TWAMP, that gives the controlling host the ability to start
and stop one or more individual test sessions using their Session
Identifiers. The base capability of the TWAMP protocol requires all test
sessions previously requested and accepted to start and stop at the same
time.</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 has completed its work on the core specification of TWAMP -
the Two-Way Active Measurement Protocol <xref target="RFC5357"></xref>.
TWAMP is an extension of 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 that are designed to test implementations for
protocol compliance.</t>
<t>This memo describes a new feature for TWAMP. TWAMP (and OWAMP) start
all previously requested and accepted test sessions at once. This
feature allows the Control-Client to control individual test sessions on
the basis of their Session Identifier (SID). The feature permits a short
duration TWAMP test to start (and/or stop) during a longer test. This
feature permits a specific diagnostic test to begin if intermediate
results indicate that the test is warranted, for example.</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). This feature also specifies a new Stop-ACK Server
response, to complete the symmetry of the session stopping process in
the same way as the Start-ACK response.</t>
<t>Implementers of this feature may also wish to implement the "Reflect
Octets" feature, described in [draft-ietf-ippm-twamp-reflect-octets,
work in progress]. This feature allows a Control-Client to insert a
locally-specified request number into the Request-TW-Session command (in
octets originally designated MBZ=Must Be Zero), and a compliant Server
will return the request number in its reply (Accept message).</t>
<t>This memo is intended to be an update to the TWAMP RFC.</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="RFC5357"></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,
</t>
<t>the definition of augmented Start Session and Stop Session
commands, and </t>
<t>the definition of related procedures for TWAMP entities. </t>
</list>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>
</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="RFC5357"></xref> uses the Modes 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-Control connection establishment follows the procedure
defined in section 3.1 of <xref target="RFC4656"></xref> OWAMP. 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
--------------------------------------------------------
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.ietf-ippm-more-twamp"></xref> memo, bit position (3)
allows a different security mode in the Test protocol and uses the
unauthenticated test packet format.</t>
<t>If the Server sets the new bit position (bit position Z) in the
Server Greeting message to indicate its capabilities, then the Server
and Session-Reflector MUST comply with the requirements of this memo
to control sessions on an individual basis if desired.</t>
<t>If the Control-Client intends to control sessions on an individual
basis (according to the requirements in this memo), it MUST set the
mode bit (Z, corresponding to the new mode) in the Setup Response
message.</t>
<t>IF the Control-Client has selected the Reflect Octets feature
[draft-ietf-ippm-twamp-reflect-octets, work in progress] in
combination with the Individual Session Control feature (after the
Server identified its capability), AND utilizes the feature to insert
a locally-specified request number in the Request-TW-Session command,
THEN the Control Client MAY send more than one Request-TW-Session
command to a given Server without waiting for the corresponding
Accept-Session 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, a TWAMP 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+B
| 7 | |
+-+-+-+-+-+-+-+-+ +
| MBZ (11 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Sessions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+B
| |
| First SID (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+B
| |
. remaining SIDs (16 octets each) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+B
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+B]]></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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+B
| 8 | Accept | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Sessions |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+B
| |
| First SID (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+B
| |
. remaining SIDs (16 octets each) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+B
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+B
]]></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 Timeout Operation">
<t>Section 3.1 of <xref target="RFC5357"></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 after
receiving a Stop-Sessions command for all corresponding SIDs (and no
test sessions are in-progress), OR when REFWAIT expires on ALL test
sessions initiated by a TWAMP-Control connection, then the SERVWAIT
monitoring SHALL resume (as though a Stop-Sessions command had been
received). An implementation which supports the SERVWAIT timeout
option SHOULD also implement the REFWAIT timeout option.</t>
<t>The diagram below illustrates the operation of timers SERVWAIT and
REFWAIT.</t>
<t><figure>
<preamble></preamble>
<artwork><![CDATA[ SERVWAIT REFWAIT SERVWAIT
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+
(no sessions
in-progress)
+-+-+-+-+-+-+-+-+-+-+-+
SID="1"
+-+-+-+-+
SID="2"
+-+-+-+-+-+-+-+-+
SID="3"
>>>>>>>>>> Time >>>>>>>>>>>>>>>>>>> Time >>>>>>>>>>>>>>>> Time >>>>>
]]></artwork>
<postamble></postamble>
</figure></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 ???? bits of the Modes 32-bit
field are used. A Control-Client MAY ignore other bit positions
greater than 2 in the Modes Field, or it MAY support other features
that are communicated in these bit positions. (The unassigned bits are
available for future protocol extensions.)</t>
<t>Other ways in which TWAMP extends OWAMP are described in <xref
target="RFC5357"></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="RFC5357"></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="RFC5357"></xref>.</t>
</section>
<section title="Reflector Behavior">
<t>The TWAMP Reflector follows the procedures and guidelines in
section 4.2 of <xref target="RFC5357"></xref>, with the following
additional functions required by this feature:</t>
<t><list style="symbols">
<t>The Session-Reflector MUST manage all test sessions accepted
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 Session-Reflector. The Session-Reflector MUST NOT generate a
test packet to the Session-Sender for packets that are
ignored.</t>
<t>If the RECOMMENDED 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>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="RFC5357"></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.ietf-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="RFC5357"></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="RFC5357"></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="RFC5357"></xref> and <xref
target="I-D.ietf-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
--------------------------------------------------------
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 anyone who provides valuable comments
on this feature.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
<?rfc include='reference.RFC.4656'?>
<?rfc include='reference.RFC.5357'?>
<?rfc include='reference.RFC.2434'?>
<?rfc include='reference.I-D.ietf-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>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 12:24:06 |