One document matched: draft-ietf-ippm-twamp-reflect-octets-05.xml
<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "rfc2629.dtd">
<?rfc toc="yes"?>
<?rfc tocompact="yes"?>
<?rfc tocdepth="3"?>
<?rfc tocindent="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes"?>
<?rfc comments="yes"?>
<?rfc inline="yes"?>
<?rfc compact="yes"?>
<?rfc subcompact="no"?>
<rfc category="std" docName="draft-ietf-ippm-twamp-reflect-octets-05"
ipr="pre5378Trust200902" updates="5357">
<front>
<title abbrev="Reflect Octets & Symmetric Size">TWAMP Reflect Octets
and Symmetrical Size Features</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="Len Ciavattone" initials="L." surname="Ciavattone">
<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 1239</phone>
<facsimile></facsimile>
<email>lencia@att.com</email>
<uri></uri>
</address>
</author>
<date day="19" month="April" year="2010" />
<abstract>
<t>The IETF has completed its work on the core specification of TWAMP -
the Two-Way Active Measurement Protocol. This memo describes two
closely-related features for TWAMP: an optional capability where the
responder host returns some of the command octets or padding octets to
the controller, and an optional sender packet format that ensures equal
test packet sizes are used in both directions.</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 two closely-related features for TWAMP.</t>
<t>One is the OPTIONAL capability for the responder host to return a
limited number of unassigned (padding) octets to the Control-Client or
Session-Sender entities. With this capability, the Control-Client or
Session-Sender can embed octets of information it deems useful and have
the assurance that the corresponding reply/test packet will contain that
information when it is reflected and returned (by the Server or
Session-Reflector.</t>
<t>The memo also adds an OPTIONAL capability to assure that reflected
test packets are the same size in both directions of transmission. This
is accomplished by specifying a new TWAMP-Test Session-Sender packet
format.</t>
<t>This memo is an update to the TWAMP core protocol specified in <xref
target="RFC5357"></xref>. Measurement systems are not required to
implement the features described in this memo to claim compliance with
<xref target="RFC5357"></xref>.</t>
<t>Throughout this memo, the bits marked MBZ (Must Be Zero) MUST be set
to zero by senders and MUST be ignored by receivers. Also, the HMAC
(Hashed Message Authentication Code) MUST be calculated as defined in
Section 3.2 of <xref target="RFC4656"></xref>.</t>
</section>
<section title="Purpose and Scope">
<t>The purpose of this memo is to define two OPTIONAL closely-related
features for TWAMP <xref target="RFC5357"></xref>. The features enhance
the TWAMP responder's capabilities to perform simple operations on
control and test packets: the reflection of octets or padding and
symmetrical sizes of fields in the TWAMP-Test packets. Motivations
include permitting the controller host to tag packets with an index for
simplified identification, and/or assert that the same size test packets
will be used in each direction.</t>
<t>The scope of the memo is limited to specifications of the following
features:</t>
<t><list style="symbols">
<t>Reflect Octets: the capability of the Server/Session-Reflector to
reflect specific octets back to the Client/Session-Sender.</t>
<t>Symmetrical Size: the capability to ensure that TWAMP-Test
protocol uses the same packet size in both directions through
support of a new TWAMP-Test Session-Sender test packet format in
both the Session-Sender and the Session-Reflector. Only the
Session-Sender test packet format is new.</t>
</list>This memo extends the modes of operation through assignment of
two new values in the Modes Field (see section 3.1 of<xref
target="RFC4656"></xref> for the format of the Server Greeting message),
while retaining backward compatibility with the core TWAMP <xref
target="RFC5357"></xref> implementations. The two new values correspond
to the two features defined in this memo.</t>
<t>When the Server and Control-Client have agreed to use the Reflect
Octets mode during control connection setup, then the Control-Client,
the Server, the Session-Sender, and the Session-Reflector MUST all
conform to the requirements of that mode, as identified below.</t>
<t>When the Server and Control-Client have agreed to use the Symmetrical
Size mode during control connection setup, then the Control-Client, the
Server, the Session-Sender, and the Session-Reflector MUST all conform
to the requirements of that mode, as identified below.</t>
</section>
<section title="TWAMP Control Extensions">
<t>TWAMP-Control protocol <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 two such extensions.</t>
<section title="Connection Setup with New Features">
<t>TWAMP connection establishment follows the procedure defined in
section 3.1 of <xref target="RFC4656"></xref> and section 3.1 of <xref
target="RFC5357"></xref>. The new features require two new bit
positions (and values) to identify the ability of the
Server/Session-Reflector to reflect specific octets back to the
Control-Client/Session-Sender, and to support the new Session-Sender
packet format in TWAMP-Test Protocol. With this added feature, the
complete set of TWAMP Modes Field bit positions and values would be 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, RFC5681, Section 3.1
Encrypted CONTROL
16 Individual Session RFC????, Section 3.1
Control
--------------------------------------------------------
xxx Reflect Octets new bit position (X)
Capability
yyy Symmetrical Size new bit position (Y)
Sender Test Packet Format
]]></artwork>
<postamble></postamble>
</figure></t>
<t>In the original OWAMP Modes 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 <xref target="RFC5618"></xref>, bit
position 3 allows unauthenticated TWAMP Test protocol to be used with
encryption on the TWAMP-Control protocol in a mixed mode of
operation.</t>
<t>The Server sets one or both of the new bit positions (X and Y) in
the Modes Field of the Server Greeting message to indicate its
capabilities and willingness to operate in either of these modes (or
both) if desired.</t>
<t>>>>IANA: change xxx, yyy, X, Y, and RFC???? to the
assigned values <<<</t>
<t>If the Control-Client intends to operate all test sessions invoked
with this control connection using one or both of the new modes, it
MUST set the Mode Field bit corresponding to each function in the
Setup Response message. With this and other extensions, the
Control-Client MAY set multiple Mode Field bits in the Setup Response
message.</t>
</section>
<section title="Reflect Octets: Request-TW-Session Packet Format">
<t>The bits designated for the Reflect Octets feature in the
Request-TW-Session command are as shown in the packet format
below.</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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 | MBZ | IPVN | Conf-Sender | Conf-Receiver |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Schedule Slots |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. ... Many fields (66 octets) not shown ... .
. .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Padding Length (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Start Time, (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timeout, (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type-P Descriptor |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Octets to be reflected | Length of padding to reflect |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
<postamble></postamble>
</figure></t>
<t>The "Padding Length" Field *continues* to specify the number of
padding octets that the Session-Sender will append to ALL TWAMP-Test
packets associated with this test session. See below for
considerations on the minimum length of the padding octets, following
the definitions of the two new fields that follow the Type-P
Descriptor.</t>
<t>Note that the number of padding octets appended to the
Session-Reflector's test packet depends on support for the RECOMMENDED
truncation process in TWAMP section 4.2.1 <xref
target="RFC5357"></xref>.</t>
<t>The "Octets to be reflected" Field SHALL be 2 octets long, as shown
and contains the octets that the Server MUST reflect in the Accept
Session message as specified below.</t>
<t>The "Length of padding to reflect" Field SHALL be 2 octets long,
and contain an unsigned binary value in units of octets. This field
communicates the length of the padding in the TWAMP-Test Packet that
the Session-Sender expects to be reflected, and the length of octets
that the Session-Reflector SHALL return in include in its TWAMP-Test
packet format (see section 4.2). By including this length field in the
Request-TW-Session message, a Server is able to determine if it can
comply with a specific request to reflect padding in the TWAMP-Test
packets, and to arrange for the Session-Reflector processing in
advance.</t>
<t>The "Padding Length" SHOULD be >= 27 octets when specifying a
test session using the Unauthenticated TWAMP-Test mode, to allow for
the RECOMMENDED truncation process in TWAMP section 4.2.1 <xref
target="RFC5357"></xref>.</t>
<t>The "Padding Length" SHOULD be >= 56 octets when specifying a
test session using the Authenticated or Encrypted TWAMP-Test modes, to
allow for the RECOMMENDED truncation process in TWAMP section 4.2.1
<xref target="RFC5357"></xref>.</t>
<t>The "Padding Length" SHALL be > the "Length of padding to
reflect" when specifying a test session using the OPTIONAL Reflect
Octets mode.</t>
<t>In Unauthenticated TWAMP-Test mode, the "Padding Length" SHALL be
>= 27 + "Length of padding to reflect" octets when specifying a
test session using BOTH the OPTIONAL Reflect Octets mode and the
RECOMMENDED truncation process in TWAMP section 4.2.1 <xref
target="RFC5357"></xref>.</t>
<t>In Authenticated or Encrypted TWAMP-Test modes, the "Padding
Length" SHALL be >= 56 + "Length of padding to reflect" octets when
specifying a test session using BOTH the OPTIONAL Reflect Octets mode
and the RECOMMENDED truncation process in TWAMP section 4.2.1 <xref
target="RFC5357"></xref>.</t>
</section>
<section title="Reflect Octets: Accept Session Packet Format">
<t>The bits designated for the Reflect Padding feature in the Accept
Session command are as shown in the packet format below.</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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Accept | MBZ | Port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
| |
| SID (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reflected octets | Server octets |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MBZ (8 octets) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| HMAC (16 octets) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
<postamble></postamble>
</figure></t>
<t>The "Reflected octets" field SHALL contain the octets from the
Request-TW-Session "Octets to be reflected" Field, and be 2 octets
long, as shown.</t>
<t>The "Server octets" field SHALL contain information that the Server
intends to be returned in the TWAMP-Test packet padding
to-be-reflected Field, OR SHALL be zero, and be 2 octets long, as
shown. Although the Server determines the SID, this field is very long
(16 octets) and does not normally appear in TWAMP-Test packets.</t>
<t>When supporting the RECOMMENDED truncation process in TWAMP section
4.2.1 <xref target="RFC5357"></xref>, IF calculations on the Padding
lengths reveal that there are insufficient octets supplied to produce
equal-length Session-Sender and Session-Reflector test packets, then
the Accept Field MUST be set to 3 = some aspect of the request is not
supported.</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>With the publication of this memo as an RFC, the last 7 bit
positions of the Modes 32-bit Field are used. A Control-Client
conforming to this extension of <xref target="RFC5357"></xref> MAY
ignore the values in the higher bits of the Modes Field, or it MAY
support other features that are communicated in those bit positions.
The other bits are available for future protocol extensions.</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 section 4<xref
target="RFC5357"> </xref> defines two additional test packet formats for
packets transmitted by the Session-Reflector. The appropriate format
depends on the security mode chosen. The new modes specified here
utilize some of the padding octets within each test packet format, or
require truncation of those octets depending on the security mode in
use.</t>
<section title="Sender Behavior">
<t>This section describes extensions to the behavior of the TWAMP
Session-Sender.</t>
<section title="Packet Timings">
<t>The Send Schedule is not utilized in TWAMP, and this is unchanged
in this memo.</t>
</section>
<section title="Reflect Octets: Packet Formats and Contents">
<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> (as indicated in section 4.1.2 of TWAMP
<xref target="RFC5357"></xref>).</t>
<t>The Reflect octets mode re-designates the original TWAMP-Test
(and OWAMP-Test) Packet Padding Field (see section 4.1.2 of <xref
target="RFC4656"></xref>), as shown below for unauthenticated
mode:</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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| Packet Padding (to be reflected) |
. (length in octets specified in command) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Additional Packet Padding .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>
<postamble></postamble>
</figure></t>
<t>The "Packet Padding (to be reflected)" Field SHALL correspond to
the length of octets specified in the Request-TW-Session "Length of
padding to reflect" Field to this test session. These are the octets
that the Session-Sender expects will be returned by the
Session-Reflector.</t>
<t>The length of the "Additional Packet Padding" Field is the
difference between two fields in the Request-TW-Session command, as
follows:</t>
<t>"Additional Packet Padding", in octets =</t>
<t>"Padding Length" - "Length of padding to reflect"</t>
<t>One possible use of the first 4 octets of the "Packet Padding (to
be reflected)" Field is shown below:</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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Server octets |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Client octets | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| Packet Padding (to be reflected) |
. (length in octets specified elsewhere) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>
<postamble></postamble>
</figure>In this example, the "Client octets" and the "Server
octets" fields contain the same information that the Client and
Server exchanged in the Request-TW-Session and Accept-Session
messages corresponding to this specific test session. These octets
would be reflected the same as the rest of the "Packet Padding (to
be reflected)" Field.</t>
</section>
<section title="Reflect Octets: Interaction with Padding Truncation">
<t>When the Reflect Octets mode is selected, and the RECOMMENDED
truncation process in TWAMP section 4.2.1 <xref
target="RFC5357"></xref> is supported, the Session-Sender MUST
anticipate a minimum padding required to achieve equal size test
packets in both directions. The amount of padding needed to achieve
symmetrical packet size depends on BOTH the security mode
(Unauthenticated/Authenticated/Encrypted) and whether the Reflect
Octets mode is selected simultaneously.</t>
<t>When using the RECOMMENDED truncation process in TWAMP section
4.2.1 <xref target="RFC5357"></xref> alone, the Session-Sender MUST
append sufficient Packet Padding octets to allow the same IP packet
payload lengths to be used in each direction of transmission (this
is usually desirable). To compensate for the
Session-Reflector’s larger test packet format, the
Session-Sender MUST append at least 27 octets of padding in
Unauthenticated mode, and at least 56 octets in Authenticated and
Encrypted modes. The sizes of TWAMP Test protocol packets and the
resulting truncated padding to achieve equal packet sizes in both
directions are shown in the table below:</t>
<texttable title="TWAMP-Test Padding Trucation">
<preamble></preamble>
<ttcol>Octets in:</ttcol>
<ttcol>Unauthenticated Mode</ttcol>
<ttcol>Auth/Encrypted Mode</ttcol>
<c>Reflector Header</c>
<c>41</c>
<c>104</c>
<c>Sender Header</c>
<c>14</c>
<c>48</c>
<c>Truncated Padding</c>
<c>27</c>
<c>56</c>
<postamble></postamble>
</texttable>
<t>When using the Reflect Octets mode simultaneously with the
RECOMMENDED truncation process in TWAMP section 4.2.1 <xref
target="RFC5357"></xref>, the Session-Sender MUST append at least 27
octets of padding plus the "Length of the padding to reflect" octets
when operating in Unauthenticated mode. The Session-Sender MUST
append at least 56 octets of padding plus the "Length of the padding
to reflect" octets when operating in Authenticated and Encrypted
modes.</t>
</section>
<section title="Symmetrical Size: Session-Sender Packet Format">
<t>When the Symmetrical Size mode is selected, the Session-Sender
SHALL use the following TWAMP-Test Packet Format in Unauthenticated
mode:</t>
<figure>
<preamble>Unauthenticated Mode</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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| |
| MBZ (27 octets) |
| |
| |
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+ +
. .
. Packet Padding .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>
<postamble></postamble>
</figure>
<t>This feature REQUIRES only a new Session-Sender test packet
format, the Session-Reflector test packet format is unchanged.</t>
</section>
<section title="Symmetrical Size AND Reflect Octets: Session-Sender Packet Format">
<t>When BOTH the Symmetrical Size mode and the Reflect Octets mode
are selected, the Session-Sender SHALL use the following TWAMP-Test
Packet Format in Unauthenticated mode:</t>
<figure>
<preamble>Unauthenticated Mode</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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| |
| MBZ (27 octets) |
| |
| |
| |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+ +
| Packet Padding (to be reflected) |
. (length in octets specified in command) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Additional Packet Padding .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>
<postamble></postamble>
</figure>
<t>In this combined mode, the Packet Padding to be reflected follows
the 27 MBZ octets. In Authenticated or Encrypted modes, the Packet
Padding to be reflected follows the 56 MBZ octets.</t>
</section>
</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:</t>
<t><list style="symbols">
<t>Reflect Octets mode: Designated octets in the "Packet Padding
(to be reflected)" field of the Session-Sender's test packet MUST
be included in the Session-Reflector's test packet.</t>
<t>Symmetrical Size mode: The Session-Reflector MUST operate using
the Session_Reflector Packet Format defined in section 4.1.4,
where the Padding Octets are separated from the information
fields.</t>
</list></t>
<section title="Reflect Octets: Session-Reflector Packet Format and Contents">
<t>The Reflect Padding feature re-designates the packet padding
field, as shown below. When the Reflect Octets mode is selected, the
Session-Sender SHALL use the following TWAMP-Test Packet Format in
Unauthenticated mode:</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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Receive Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Timestamp |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender Error Estimate | MBZ |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender TTL | Packet Padding (from Session-Sender) |
+-+-+-+-+-+-+-+-+ +
. .
+ +-+-+-+-+-+-+-+-+
| Packet Padding (from Session-Sender) | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
| |
. Additional Packet Padding .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>
<postamble></postamble>
</figure>The "Packet Padding (from Session-Sender)" field MUST be
the same octets as the "Packet Padding (to be reflected)" field in
the Session-Sender's test packet, and therefore MUST conform to the
length specified in the Request-TW-Session message.</t>
<t>When simultaneously using the RECOMMENDED truncation process in
TWAMP section 4.2.1 <xref target="RFC5357"></xref> AND Reflect
octets mode, the Session-Reflector MUST reflect the designated
octets from the Session-Sender's test packet in the "Packet Padding
(from Session-Sender)" Field, and MAY re-use additional Packet
Padding from the Session-Sender. The Session-Reflector MUST truncate
the padding such that the highest number octets are discarded, and
the test packet length equals the Session-Sender's packet length.
When using the RECOMMENDED truncation process, the Session-Reflector
MUST truncate exactly 27 octets of padding in Unauthenticated mode,
and exactly 56 octets in Authenticated and Encrypted modes.</t>
<t>The Session-Reflector MAY re-use the Sender’s Packet
Padding (since the requirements for padding generation are the same
for each).</t>
</section>
<section title="Symmetrical Size: Session-Reflector Packet Format">
<t>When Symmetrical Size mode is selected, the Session-Sender packet
formats for unauthenticated and authenticated/encrypted modes are
identical to the core TWAMP specification, section 4.2.1 of <xref
target="RFC5357"></xref>. Thus, the Session-Reflector test packet
format is unchanged.</t>
<t>The Session-Reflector MUST construct its test packet using the
information in the Session-Sender's test packet. The length of the
Session-Reflector's test packet SHALL equal the length of the
Session-Sender's test packet.</t>
</section>
<section title="Symmetrical Size AND Reflect Octets: Session-Sender Packet Format">
<t>When BOTH the Symmetrical Size mode and the Reflect Octets mode
are selected, the Session-Reflector MUST operate using the
Session_Reflector Packet Format defined in section 4.1.5, where the
Padding Octets are separated from the information fields, and the
Padding to be Reflected field precedes the Additional Padding.</t>
<t>The Session-Reflector SHALL use the same TWAMP-Test Packet Format
as specified in section 4.2.1 above.</t>
</section>
<t></t>
</section>
</section>
<section anchor="Security" title="Security Considerations">
<t>These extended modes of operation do not appear to permit any new
attacks on hosts communicating with core TWAMP <xref
target="RFC5357"></xref>.</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="RFC5357"></xref>.</t>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>This memo adds two modes to the IANA registry for the TWAMP Modes
Field, and describes behavior when the new modes are used. This 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="RFC5618"></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 that
correspond to values in the Modes registry. For the TWAMP-Modes
registry, we expect that new features will be assigned increasing
registry values that correspond to single bit positions, unless there
is a good reason to do otherwise (more complex encoding than single
bit positions may be used in the future, to access the 2^32 value
space).</t>
</section>
<section title="Registry Management">
<t>This registry must be updated only by "IETF Consensus" as specified
in <xref target="RFC5226"></xref>(an RFC documenting registry use that
is approved by the IESG).</t>
</section>
<section title="Experimental Numbers">
<t>No experimental values are currently assigned for the Modes
Registry.</t>
</section>
<section title="Registry Contents">
<t>TWAMP Modes Registry is recommended to be augmented as
follows:<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, RFC5618, Section 3.1 (3)
Auth. CONTROL
16 Individual Session RFC????, Section 3.1
Control bit position (4)
--------------------------------------------------------
xxx Reflect Octets this memo, section 3.1
Capability new bit position (X)
yyy Symmetrical Size this memo, section 3.1
Sender Test Packet Format new bit position (Y)
]]></artwork>
<postamble></postamble>
</figure>The suggested values are</t>
<t>X=5, xxx=32</t>
<t>Y=6, yyy=64</t>
</section>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The authors thank Steve Baillargeon, Walt Steverson, and Stina Ross
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.RFC.5357'?>
<?rfc include='reference.RFC.5226'?>
<?rfc include='reference.RFC.5618'?>
<?rfc ?>
<?rfc ?>
</references>
<references title="Informative References">
<?rfc ?>
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 12:24:08 |