One document matched: draft-ietf-ippm-twamp-reflect-octets-00.xml
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<rfc category="std" docName="draft-ietf-ippm-twamp-reflect-octets-00"
ipr="full3978">
<front>
<title abbrev="TWAMP Reflect Octets">TWAMP Reflect Octets Feature</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="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: an optional capability where the responder host
returns some of the command octets or padding octets to the controller,
and/or ensures that the same 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 a new feature for TWAMP. This feature adds 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. The
feature also adds the Session-Reflector capability to assure that
reflected test packets SHALL have their padding octets truncated, so
that TWAMP-Test protocol uses the same packet size in both directions of
transmission.</t>
<t>The relationship between this memo and TWAMP is intended to be an
update to <xref target="RFC5357"></xref> when published.</t>
</section>
<section title="Purpose and Scope">
<t>The purpose of this memo is to describe a new feature for TWAMP <xref
target="RFC5357"></xref>. The feature enhances the TWAMP responder's
capabilities to perform simple operations on control and test packets:
the reflection of octets or padding and the guaranteed truncation of
padding to compensate for the different sizes of TWAMP fields in the
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 MUST be used in each direction.</t>
<t>The scope of the memo is currently limited to specifications of the
following feature:</t>
<t><list style="symbols">
<t>Extension of the modes of operation through assignment of new
values in the Mode Field (see section 3.1 <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. These two values
identify the ability of the Server/Session-Reflector to reflect
specific octets back to the Client/Session-Sender, and/or to
truncate padding octets and ensure that TWAMP-Test protocol uses the
same packet size in both directions.</t>
</list></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 one such extension.</t>
<section title="Connection Setup with Reflect Padding Feature">
<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 feature requires 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 truncate padding octets when
required. 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, draft-ietf-more-twamp (3)
Encrypted CONTROL
--------------------------------------------------------
xxx Reflect Octets new bit position (X)
Capability
yyy Truncate Padding new bit position (Y)
Capability
]]></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 the memo <xref
target="I-D.ietf-ippm-more-twamp"></xref>, bit position 3 allows
unauthenticated TWAMP Test protocol to be used with encryption on the
TWAMP-Control protocol.</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 these modes if desired.
>>>IANA: change X and Y 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 Modes Field bit corresponding to that function in the
Setup Response message.</t>
</section>
<section title="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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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, especially
when complying with the options described in this memo, 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 OPTIONAL
Truncate Padding mode, or 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>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 OPTIONAL Truncate Padding mode with the
Unauthenticated TWAMP-Test mode.</t>
<t>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 OPTIONAL Truncate Padding mode with the
Authenticated or Encrypted TWAMP-Test modes.</t>
</section>
<section title="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 | MBZ (2 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>In Truncate Padding mode, 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>Thus, the last six bits of the Modes 32-bit Field are used. A
client conforming to this extension of <xref target="RFC5357"></xref>
MAY ignore the values in the first 24 bits of the Modes Field, or it
MAY support other features that are communicated in these bit
positions. (The first 24 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="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="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 | MBZ (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Packet Padding (to be reflected) |
. (length in octets specified elsewhere) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. 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>
</section>
<section title="Padding Truncation">
<t>When the Truncate Padding mode is selected and communicated in
the Setup Response message, the Session-Sender MUST anticipate a
minimum padding required to achieve equal size test packets in both
directions. The amount of padding needed depends on BOTH the
security mode (Unauthenticated/Authenticated/Encrypted) and whether
the Reflect Octets mode is selected simultaneously.</t>
<t>When using the Truncate Padding mode, 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.</t>
<t>When using the Reflect Octets mode simultaneously with the
Truncate Padding mode, 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>
<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>Truncate Padding mode: Octets in the packet padding field of
the Session-Sender's test packet MUST be truncated so that the
length of the Session-Reflector's test packet equals the length of
the Session-Sender's test packet.</t>
</list></t>
<section title="Packet Format and Contents">
<t>The Reflect Padding feature re-designates the packet padding
field, 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 | 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>IF the test packet length is truncated within the padding fields
in conformance with the RECOMMENDED truncation process in TWAMP
section 4.2.1 <xref target="RFC5357"></xref>, THEN ALL padding
designated to be reflected MUST be reflected by Session-Reflectors
using this feature.</t>
</section>
<section title="Padding Truncation">
<t>Note that the Session-Reflector Test Packet Formats are larger
than the Sender’s formats. When the Truncate Padding mode is
selected and communicated in the Setup Response message, the
Session-Reflector must truncate a specific number of padding octets
to achieve equal size test packets in both directions. The number of
octets truncated depends on BOTH the security mode
(Unauthenticated/Authenticated/Encrypted) and whether the Reflect
octets mode is selected simultaneously.</t>
<t>When using the Truncate Padding mode, the Session-Reflector MUST
truncate exactly 27 octets of padding in Unauthenticated mode, and
exactly 56 octets in Authenticated and Encrypted modes. The
Session-Reflector MAY re-use the Sender’s Packet Padding
(since the requirements for padding generation are the same for
each), and in this case the Session-Reflector MUST truncate the
padding such that the highest number octets are discarded.</t>
<t>When simultaneously using the Truncate Padding mode 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.</t>
</section>
<t></t>
</section>
</section>
<section title="Possible Alternative">
<t>If new TWAMP-Test packet formats are defined, the Reflect Octets and
Truncate Padding modes could be folded into one new mode.</t>
<t>This Alternative is illustrated for discussion purposes.</t>
<t>New Session-Sender Test Packet Format:</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 (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| |
| |
| Discard Fill |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Packet Padding (to be reflected) |
. (length in octets specified elsewhere) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Additional Packet Padding .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+]]></artwork>
<postamble></postamble>
</figure>The "Discard Fill" octets are discarded at the
Session-Reflector.</t>
<t>New Session-Reflector Test Packet format:</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 | MBZ (3 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Packet Padding (from Session-Sender) .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Additional Packet Padding .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ]]></artwork>
</figure></t>
<t></t>
</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 mode combinations 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="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>
</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="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, draft-ietf-more-twamp (3)
Auth. CONTROL
--------------------------------------------------------
xxx Reflect Octets this memo, section 3.1
Capability new bit position (X)
yyy Truncate Padding this memo, section 3.1
Capability new bit position (Y)]]></artwork>
<postamble></postamble>
</figure>The suggested values are</t>
<t>X=4, xxx=16</t>
<t>Y=5, yyy=32</t>
</section>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The authors would like to thank Walt Steverson 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.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 12:24:28 |