< draft-ietf-ipsecme-iptfs-02.txt   draft-ietf-ipsecme-iptfs-03.txt >
Network Working Group C. Hopps Network Working Group C. Hopps
Internet-Draft LabN Consulting, L.L.C. Internet-Draft LabN Consulting, L.L.C.
Intended status: Standards Track September 30, 2020 Intended status: Standards Track November 15, 2020
Expires: April 3, 2021 Expires: May 19, 2021
IP Traffic Flow Security IP Traffic Flow Security
draft-ietf-ipsecme-iptfs-02 draft-ietf-ipsecme-iptfs-03
Abstract Abstract
This document describes a mechanism to enhance IPsec traffic flow This document describes a mechanism to enhance IPsec traffic flow
security by adding traffic flow confidentiality to encrypted IP security by adding traffic flow confidentiality to encrypted IP
encapsulated traffic. Traffic flow confidentiality is provided by encapsulated traffic. Traffic flow confidentiality is provided by
obscuring the size and frequency of IP traffic using a fixed-sized, obscuring the size and frequency of IP traffic using a fixed-sized,
constant-send-rate IPsec tunnel. The solution allows for congestion constant-send-rate IPsec tunnel. The solution allows for congestion
control as well. control as well as non-constant send-rate usage.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 3, 2021. This Internet-Draft will expire on May 19, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 20 skipping to change at page 2, line 20
1.1. Terminology & Concepts . . . . . . . . . . . . . . . . . 3 1.1. Terminology & Concepts . . . . . . . . . . . . . . . . . 3
2. The IP-TFS Tunnel . . . . . . . . . . . . . . . . . . . . . . 4 2. The IP-TFS Tunnel . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Tunnel Content . . . . . . . . . . . . . . . . . . . . . 4 2.1. Tunnel Content . . . . . . . . . . . . . . . . . . . . . 4
2.2. IPTFS_PROTOCOL Payload Content . . . . . . . . . . . . . 4 2.2. IPTFS_PROTOCOL Payload Content . . . . . . . . . . . . . 4
2.2.1. Data Blocks . . . . . . . . . . . . . . . . . . . . . 5 2.2.1. Data Blocks . . . . . . . . . . . . . . . . . . . . . 5
2.2.2. No Implicit End Padding Required . . . . . . . . . . 6 2.2.2. No Implicit End Padding Required . . . . . . . . . . 6
2.2.3. Fragmentation, Sequence Numbers and All-Pad Payloads 6 2.2.3. Fragmentation, Sequence Numbers and All-Pad Payloads 6
2.2.4. Empty Payload . . . . . . . . . . . . . . . . . . . . 6 2.2.4. Empty Payload . . . . . . . . . . . . . . . . . . . . 6
2.2.5. IP Header Value Mapping . . . . . . . . . . . . . . . 7 2.2.5. IP Header Value Mapping . . . . . . . . . . . . . . . 7
2.3. Exclusive SA Use . . . . . . . . . . . . . . . . . . . . 7 2.3. Exclusive SA Use . . . . . . . . . . . . . . . . . . . . 7
2.4. Zero-Conf Receive-Side Operation On The SA. . . . . . . . 7 2.4. Modes of Operation . . . . . . . . . . . . . . . . . . . 7
2.5. Modes of Operation . . . . . . . . . . . . . . . . . . . 7 2.4.1. Non-Congestion Controlled Mode . . . . . . . . . . . 7
2.5.1. Non-Congestion Controlled Mode . . . . . . . . . . . 8 2.4.2. Congestion Controlled Mode . . . . . . . . . . . . . 8
2.5.2. Congestion Controlled Mode . . . . . . . . . . . . . 8
3. Congestion Information . . . . . . . . . . . . . . . . . . . 9 3. Congestion Information . . . . . . . . . . . . . . . . . . . 9
3.1. ECN Support . . . . . . . . . . . . . . . . . . . . . . . 10 3.1. ECN Support . . . . . . . . . . . . . . . . . . . . . . . 10
4. Configuration . . . . . . . . . . . . . . . . . . . . . . . . 10 4. Configuration . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . 10 4.1. Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . 11
4.2. Fixed Packet Size . . . . . . . . . . . . . . . . . . . . 11 4.2. Fixed Packet Size . . . . . . . . . . . . . . . . . . . . 11
4.3. Congestion Control . . . . . . . . . . . . . . . . . . . 11 4.3. Congestion Control . . . . . . . . . . . . . . . . . . . 11
5. IKEv2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5. IKEv2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. USE_TFS Notification Message . . . . . . . . . . . . . . 11 5.1. USE_TFS Notification Message . . . . . . . . . . . . . . 11
6. Packet and Data Formats . . . . . . . . . . . . . . . . . . . 12 6. Packet and Data Formats . . . . . . . . . . . . . . . . . . . 12
6.1. IP-TFS Payload . . . . . . . . . . . . . . . . . . . . . 12 6.1. IP-TFS Payload . . . . . . . . . . . . . . . . . . . . . 12
6.1.1. Non-Congestion Control IPTFS_PROTOCOL Payload Format 12 6.1.1. Non-Congestion Control IPTFS_PROTOCOL Payload Format 12
6.1.2. Congestion Control IPTFS_PROTOCOL Payload Format . . 13 6.1.2. Congestion Control IPTFS_PROTOCOL Payload Format . . 13
6.1.3. Data Blocks . . . . . . . . . . . . . . . . . . . . . 14 6.1.3. Data Blocks . . . . . . . . . . . . . . . . . . . . . 15
6.1.4. IKEv2 USE_IPTFS Notification Message . . . . . . . . 16 6.1.4. IKEv2 USE_IPTFS Notification Message . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
7.1. IPTFS_PROTOCOL Type . . . . . . . . . . . . . . . . . . . 17 7.1. IPTFS_PROTOCOL Type . . . . . . . . . . . . . . . . . . . 18
7.2. IPTFS_PROTOCOL Sub-Type Registry . . . . . . . . . . . . 17 7.2. IPTFS_PROTOCOL Sub-Type Registry . . . . . . . . . . . . 18
7.3. USE_IPTFS Notify Message Status Type . . . . . . . . . . 17 7.3. USE_IPTFS Notify Message Status Type . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 18 8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . 18 9.1. Normative References . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . 18 9.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Example Of An Encapsulated IP Packet Flow . . . . . 20 Appendix A. Example Of An Encapsulated IP Packet Flow . . . . . 21
Appendix B. A Send and Loss Event Rate Calculation . . . . . . . 21 Appendix B. A Send and Loss Event Rate Calculation . . . . . . . 22
Appendix C. Comparisons of IP-TFS . . . . . . . . . . . . . . . 21 Appendix C. Comparisons of IP-TFS . . . . . . . . . . . . . . . 22
C.1. Comparing Overhead . . . . . . . . . . . . . . . . . . . 21 C.1. Comparing Overhead . . . . . . . . . . . . . . . . . . . 22
C.1.1. IP-TFS Overhead . . . . . . . . . . . . . . . . . . . 21 C.1.1. IP-TFS Overhead . . . . . . . . . . . . . . . . . . . 22
C.1.2. ESP with Padding Overhead . . . . . . . . . . . . . . 22 C.1.2. ESP with Padding Overhead . . . . . . . . . . . . . . 23
C.2. Overhead Comparison . . . . . . . . . . . . . . . . . . . 24
C.2. Overhead Comparison . . . . . . . . . . . . . . . . . . . 23 C.3. Comparing Available Bandwidth . . . . . . . . . . . . . . 25
C.3. Comparing Available Bandwidth . . . . . . . . . . . . . . 23 C.3.1. Ethernet . . . . . . . . . . . . . . . . . . . . . . 25
C.3.1. Ethernet . . . . . . . . . . . . . . . . . . . . . . 24 Appendix D. Acknowledgements . . . . . . . . . . . . . . . . . . 27
Appendix D. Acknowledgements . . . . . . . . . . . . . . . . . . 26 Appendix E. Contributors . . . . . . . . . . . . . . . . . . . . 27
Appendix E. Contributors . . . . . . . . . . . . . . . . . . . . 26 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 27
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction 1. Introduction
Traffic Analysis ([RFC4301], [AppCrypt]) is the act of extracting Traffic Analysis ([RFC4301], [AppCrypt]) is the act of extracting
information about data being sent through a network. While one may information about data being sent through a network. While one may
directly obscure the data through the use of encryption [RFC4303], directly obscure the data through the use of encryption [RFC4303],
the traffic pattern itself exposes information due to variations in the traffic pattern itself exposes information due to variations in
it's shape and timing ([I-D.iab-wire-image], [AppCrypt]). Hiding the it's shape and timing ([I-D.iab-wire-image], [AppCrypt]). Hiding the
size and frequency of traffic is referred to as Traffic Flow size and frequency of traffic is referred to as Traffic Flow
Confidentiality (TFC) per [RFC4303]. Confidentiality (TFC) per [RFC4303].
[RFC4303] provides for TFC by allowing padding to be added to [RFC4303] provides for TFC by allowing padding to be added to
encrypted IP packets and allowing for transmission of all-pad packets encrypted IP packets and allowing for transmission of all-pad packets
(indicated using protocol 59). This method has the major limitation (indicated using protocol 59). This method has the major limitation
that it can significantly under-utilize the available bandwidth. that it can significantly under-utilize the available bandwidth.
The IP-TFS solution provides for full TFC without the aforementioned The IP-TFS solution provides for full TFC without the aforementioned
bandwidth limitation. This is accomplished by using a constant-send- bandwidth limitation. This is accomplished by using a constant-send-
rate IPsec [RFC4303] tunnel with fixed-sized encapsulating packets; rate IPsec [RFC4303] tunnel with fixed-sized encapsulating packets;
however, these fixed-sized packets can contain partial, whole or however, these fixed-sized packets can contain partial, whole or
multiple IP packets to maximize the bandwidth of the tunnel. multiple IP packets to maximize the bandwidth of the tunnel. A non-
constant send-rate is allowed, but the confidentiality properties of
its use are outside the scope of this document.
For a comparison of the overhead of IP-TFS with the RFC4303 For a comparison of the overhead of IP-TFS with the RFC4303
prescribed TFC solution see Appendix C. prescribed TFC solution see Appendix C.
Additionally, IP-TFS provides for dealing with network congestion Additionally, IP-TFS provides for dealing with network congestion
[RFC2914]. This is important for when the IP-TFS user is not in full [RFC2914]. This is important for when the IP-TFS user is not in full
control of the domain through which the IP-TFS tunnel path flows. control of the domain through which the IP-TFS tunnel path flows.
1.1. Terminology & Concepts 1.1. Terminology & Concepts
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packet can be sent per encapsulating packet. In order to maximize packet can be sent per encapsulating packet. In order to maximize
bandwidth IP-TFS breaks this one-to-one association. bandwidth IP-TFS breaks this one-to-one association.
IP-TFS aggregates as well as fragments the inner IP traffic flow into IP-TFS aggregates as well as fragments the inner IP traffic flow into
fixed-sized encapsulating IPsec tunnel packets. Padding is only fixed-sized encapsulating IPsec tunnel packets. Padding is only
added to the the tunnel packets if there is no data available to be added to the the tunnel packets if there is no data available to be
sent at the time of tunnel packet transmission, or if fragmentation sent at the time of tunnel packet transmission, or if fragmentation
has been disabled by the receiver. has been disabled by the receiver.
This is accomplished using a new Encapsulating Security Payload (ESP, This is accomplished using a new Encapsulating Security Payload (ESP,
[RFC4303]) type which is identified by the IP protocol number [RFC4303]) type which is identified by the number IPTFS_PROTOCOL
IPTFS_PROTOCOL (TBD1). (Section 6.1).
2.2. IPTFS_PROTOCOL Payload Content 2.2. IPTFS_PROTOCOL Payload Content
The IPTFS_PROTOCOL payload content defined in this document is The IPTFS_PROTOCOL payload content defined in this document is
comprised of a 4 or 16 octet header followed by either a partial, a comprised of a 4 or 24 octet header followed by either a partial, a
full or multiple partial or full data blocks. The following diagram full or multiple partial or full data blocks. The following diagram
illustrates this IPTFS_PROTOCOL payload within the ESP packet. See illustrates this IPTFS_PROTOCOL payload within the ESP packet. See
Section 6.1 for the exact formats of the IPTFS_PROTOCOL payload. Section 6.1 for the exact formats of the IPTFS_PROTOCOL payload.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. Outer Encapsulating Header ... . . Outer Encapsulating Header ... .
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
. ESP Header... . . ESP Header... .
+---------------------------------------------------------------+ +---------------------------------------------------------------+
| ... : BlockOffset | | ... : BlockOffset |
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It is not the intention of this specification to allow for mixed use It is not the intention of this specification to allow for mixed use
of an IP-TFS enabled SA. In other words, an SA that has IP-TFS of an IP-TFS enabled SA. In other words, an SA that has IP-TFS
enabled is exclusively for IP-TFS use and MUST NOT have non-IP-TFS enabled is exclusively for IP-TFS use and MUST NOT have non-IP-TFS
payloads such as IP (IP protocol 4), TCP transport (IP protocol 6), payloads such as IP (IP protocol 4), TCP transport (IP protocol 6),
or ESP pad packets (protocol 59) intermixed with non-empty IP-TFS (IP or ESP pad packets (protocol 59) intermixed with non-empty IP-TFS (IP
protocol TBD1) payloads. While it's possible to envision making the protocol TBD1) payloads. While it's possible to envision making the
algorithm work in the presence of sequence number skips in the IP-TFS algorithm work in the presence of sequence number skips in the IP-TFS
payload stream, the added complexity is not deemed worthwhile. Other payload stream, the added complexity is not deemed worthwhile. Other
IPsec uses can configure and use their own SAs. IPsec uses can configure and use their own SAs.
2.4. Zero-Conf Receive-Side Operation On The SA. 2.4. Modes of Operation
Receive-side operation of IP-TFS does not require any per-SA
configuration on the receiver; as such, an IP-TFS implementation
SHOULD support the option of switching to IP-TFS receive-side
operation on receipt of the first IP-TFS payload.
2.5. Modes of Operation
Just as with normal IPsec/ESP tunnels, IP-TFS tunnels are Just as with normal IPsec/ESP tunnels, IP-TFS tunnels are
unidirectional. Bidirectional IP-TFS functionality is achieved by unidirectional. Bidirectional IP-TFS functionality is achieved by
setting up 2 IP-TFS tunnels, one in either direction. setting up 2 IP-TFS tunnels, one in either direction.
An IP-TFS tunnel can operate in 2 modes, a non-congestion controlled An IP-TFS tunnel can operate in 2 modes, a non-congestion controlled
mode and congestion controlled mode. mode and congestion controlled mode.
2.5.1. Non-Congestion Controlled Mode 2.4.1. Non-Congestion Controlled Mode
In the non-congestion controlled mode IP-TFS sends fixed-sized In the non-congestion controlled mode IP-TFS sends fixed-sized
packets at a constant rate. The packet send rate is constant and is packets at a constant rate. The packet send rate is constant and is
not automatically adjusted regardless of any network congestion not automatically adjusted regardless of any network congestion
(e.g., packet loss). (e.g., packet loss).
For similar reasons as given in [RFC7510] the non-congestion For similar reasons as given in [RFC7510] the non-congestion
controlled mode should only be used where the user has full controlled mode should only be used where the user has full
administrative control over the path the tunnel will take. This is administrative control over the path the tunnel will take. This is
required so the user can guarantee the bandwidth and also be sure as required so the user can guarantee the bandwidth and also be sure as
to not be negatively affecting network congestion [RFC2914]. In this to not be negatively affecting network congestion [RFC2914]. In this
case packet loss should be reported to the administrator (e.g., via case packet loss should be reported to the administrator (e.g., via
syslog, YANG notification, SNMP traps, etc) so that any failures due syslog, YANG notification, SNMP traps, etc) so that any failures due
to a lack of bandwidth can be corrected. to a lack of bandwidth can be corrected.
2.5.2. Congestion Controlled Mode 2.4.2. Congestion Controlled Mode
With the congestion controlled mode, IP-TFS adapts to network With the congestion controlled mode, IP-TFS adapts to network
congestion by lowering the packet send rate to accommodate the congestion by lowering the packet send rate to accommodate the
congestion, as well as raising the rate when congestion subsides. congestion, as well as raising the rate when congestion subsides.
Since overhead is per packet, by allowing for maximal fixed-size Since overhead is per packet, by allowing for maximal fixed-size
packets and varying the send rate transport overhead is minimized. packets and varying the send rate transport overhead is minimized.
The output of the congestion control algorithm will adjust the rate The output of the congestion control algorithm will adjust the rate
at which the ingress sends packets. While this document does not at which the ingress sends packets. While this document does not
require a specific congestion control algorithm, best current require a specific congestion control algorithm, best current
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receiver and from the sender, at least once per RTT. Prior to receiver and from the sender, at least once per RTT. Prior to
establishing an RTT the information SHOULD be sent constantly from establishing an RTT the information SHOULD be sent constantly from
the sender and the receiver so that an RTT estimate can be the sender and the receiver so that an RTT estimate can be
established. The lack of receiving this information over multiple established. The lack of receiving this information over multiple
consecutive RTT intervals should be considered a congestion event consecutive RTT intervals should be considered a congestion event
that causes the sender to adjust it's sending rate lower. For that causes the sender to adjust it's sending rate lower. For
example, [RFC4342] calls this the "no feedback timeout" and it is example, [RFC4342] calls this the "no feedback timeout" and it is
equal to 4 RTT intervals. When a "no feedback timeout" has occurred equal to 4 RTT intervals. When a "no feedback timeout" has occurred
[RFC4342] halves the sending rate. [RFC4342] halves the sending rate.
An implementation could choose to always include the congestion An implementation MAY choose to always include the congestion
information in it's IP-TFS payload header if sending on an IP-TFS information in it's IP-TFS payload header if sending on an IP-TFS
enabled SA. Since IP-TFS normally will operate with a large packet enabled SA. Since IP-TFS normally will operate with a large packet
size, the congestion information should represent a small portion of size, the congestion information should represent a small portion of
the available tunnel bandwidth. the available tunnel bandwidth. An implementation choosing to always
send the data MAY also choose to only update the "LossEventRate" and
"RTT" header field values it sends every "RTT" though.
When an implementation is choosing a congestion control algorithm (or When an implementation is choosing a congestion control algorithm (or
a selection of algorithms) one should remember that IP-TFS is not a selection of algorithms) one should remember that IP-TFS is not
providing for reliable delivery of IP traffic, and so per packet ACKs providing for reliable delivery of IP traffic, and so per packet ACKs
are not required and are not provided. are not required and are not provided.
It's worth noting that the variable send-rate of a congestion It's worth noting that the variable send-rate of a congestion
controlled IP-TFS tunnel, is not private; however, this send-rate is controlled IP-TFS tunnel, is not private; however, this send-rate is
being driven by network congestion, and as long as the encapsulated being driven by network congestion, and as long as the encapsulated
(inner) traffic flow shape and timing are not directly affecting the (inner) traffic flow shape and timing are not directly affecting the
(outer) network congestion, the variations in the tunnel rate will (outer) network congestion, the variations in the tunnel rate will
not weaken the provided inner traffic flow confidentiality. not weaken the provided inner traffic flow confidentiality.
2.5.2.1. Circuit Breakers 2.4.2.1. Circuit Breakers
In additional to congestion control, implementations MAY choose to In additional to congestion control, implementations MAY choose to
define and implement circuit breakers [RFC8084] as a recovery method define and implement circuit breakers [RFC8084] as a recovery method
of last resort. Enabling circuit breakers is also a reason a user of last resort. Enabling circuit breakers is also a reason a user
may wish to enable congestion information reports even when using the may wish to enable congestion information reports even when using the
non-congestion controlled mode of operation. The definition of non-congestion controlled mode of operation. The definition of
circuit breakers are outside the scope of this document. circuit breakers are outside the scope of this document.
3. Congestion Information 3. Congestion Information
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paired SA back to the sender (this is always the case when the tunnel paired SA back to the sender (this is always the case when the tunnel
was created using IKEv2). If the SA back to the sender is a non-IP- was created using IKEv2). If the SA back to the sender is a non-IP-
TFS enabled SA then an IPTFS_PROTOCOL empty payload (i.e., header TFS enabled SA then an IPTFS_PROTOCOL empty payload (i.e., header
only) is used to convey the information. only) is used to convey the information.
In order to calculate a loss event rate compatible with [RFC5348], In order to calculate a loss event rate compatible with [RFC5348],
the receiver needs to have a round-trip time estimate. Thus the the receiver needs to have a round-trip time estimate. Thus the
sender communicates this estimate in the "RTT" header field. On sender communicates this estimate in the "RTT" header field. On
startup this value will be zero as no RTT estimate is yet known. startup this value will be zero as no RTT estimate is yet known.
In order to allow the sender to calculate the "RTT" value, the In order for the sender to estimate it's "RTT" value, the sender
receiver communicates the last sequence number it has seen to the places a timestamp value in the "TVal" header field. On first
sender in the "LastSeqNum" header field. In addition to the receipt of this "TVal", the receiver records the new "TVal" value
"LastSeqNum" value, the receiver sends an estimate of the amount of along with the time it arrived locally, subsequent receipt of the
time between receiving the "LastSeqNum" packet and transmitting the same "TVal" MUST not update the recorded time. When the receiver
"LastSeqNum" value back to the sender in the congestion information. sends it's CC header it places this latest recorded value in the
It places this time estimate in the "Delay" header field along with "TEcho" header field, along with 2 delay values, "Echo Delay" and
the "LastSeqNum". "Transmit Delay". The "Echo Delay" value is the time delta from the
recorded arrival time of "TVal" and the current clock in
microseconds. The second value, "Transmit Delay", is the receiver's
current transmission delay on the tunnel (i.e., the average time
between sending packets on it's half of the IP-TFS tunnel). When the
sender receives back it's "TVal" in the "TEcho" header field it
calculates 2 RTT estimates. The first is the actual delay found by
subtracting the "TEcho" value from it's current clock and then
subtracting "Echo Delay" as well. The second RTT estimate is found
by adding the received "Transmit Delay" header value to the senders
own transmission delay (i.e., the average time between sending
packets on it's half of the IP-TFS tunnel). The larger of these 2
RTT estimates SHOULD be used as the "RTT" value. The two estimates
are required to handle different combinations of faster or slow
tunnel packet paths with fast or slow fixed tunnel rates. Choosing
the larger of the two values guarantees that the "RTT" is never
considered faster than the aggregate transmission delay based on the
IP-TFS tunnel rate (the second estimate), as well as never being
considered faster than the actual RTT along the tunnel packet path
(the first estimate).
The receiver also calculates, and communicates in the "LossEventRate" The receiver also calculates, and communicates in the "LossEventRate"
header field, the loss event rate for use by the sender. This is header field, the loss event rate for use by the sender. This is
slightly different from [RFC4342] which periodically sends all the slightly different from [RFC4342] which periodically sends all the
loss interval data back to the sender so that it can do the loss interval data back to the sender so that it can do the
calculation. See Appendix B for a suggested way to calculate the calculation. See Appendix B for a suggested way to calculate the
loss event rate value. Initially this value will be zero (indicating loss event rate value. Initially this value will be zero (indicating
no loss) until enough data has been collected by the receiver to no loss) until enough data has been collected by the receiver to
update it. update it.
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initiator, by deleting the child SA if the now established non-IP-TFS initiator, by deleting the child SA if the now established non-IP-TFS
operation is unacceptable). operation is unacceptable).
The notification type and payload flag values are defined in The notification type and payload flag values are defined in
Section 6.1.4. Section 6.1.4.
6. Packet and Data Formats 6. Packet and Data Formats
6.1. IP-TFS Payload 6.1. IP-TFS Payload
An IP-TFS payload is identified by the IP protocol number ESP Payload Type: 0x5
IPTFS_PROTOCOL (TBD1). The first octet of this payload indicates the
format of the remaining payload data. An IP-TFS payload is identified by the ESP payload type
IPTFS_PROTOCOL which has the value 0x5. The first octet of this
payload indicates the format of the remaining payload data.
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-
| Sub-type | ... | Sub-type | ...
+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-
Sub-type: Sub-type:
An 8 bit value indicating the payload format. An 8 bit value indicating the payload format.
This specification defines 2 payload sub-types. These payload This specification defines 2 payload sub-types. These payload
skipping to change at page 13, line 14 skipping to change at page 13, line 37
"DataBlocks" data (i.e., it does not count subsequent packets "DataBlocks" data (i.e., it does not count subsequent packets
non-"DataBlocks" octets). non-"DataBlocks" octets).
DataBlocks: DataBlocks:
Variable number of octets that begins with the start of a data Variable number of octets that begins with the start of a data
block, or the continuation of a previous data block, followed by block, or the continuation of a previous data block, followed by
zero or more additional data blocks. zero or more additional data blocks.
6.1.2. Congestion Control IPTFS_PROTOCOL Payload Format 6.1.2. Congestion Control IPTFS_PROTOCOL Payload Format
The congestion control IPTFS_PROTOCOL payload is comprised of a 16 The congestion control IPTFS_PROTOCOL payload is comprised of a 24
octet header followed by a variable amount of "DataBlocks" data as octet header followed by a variable amount of "DataBlocks" data as
shown below. shown below.
1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-type (1) | Reserved |E| BlockOffset | | Sub-type (1) | Reserved |E| BlockOffset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RTT | Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LossEventRate | | LossEventRate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LastSeqNum | | RTT | Echo Delay ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Echo Delay | Transmit Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TVal |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TEcho |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DataBlocks ... | DataBlocks ...
+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+-+-+-+-
Sub-type: Sub-type:
An octet indicating the payload format. For this congestion An octet indicating the payload format. For this congestion
control format, the value is 1. control format, the value is 1.
Reserved: Reserved:
A 7 bit field set to 0 on generation, and ignored on receipt. A 7 bit field set to 0 on generation, and ignored on receipt.
E: E:
A 1 bit value if set indicates that Congestion Experienced (CE) A 1 bit value if set indicates that Congestion Experienced (CE)
ECN bits were received and used in deriving the reported ECN bits were received and used in deriving the reported
"LossEventRate". "LossEventRate".
BlockOffset: BlockOffset:
The same value as the non-congestion controlled payload format The same value as the non-congestion controlled payload format
value. value.
RTT:
A 16 bit value specifying the sender's current round-trip time
estimate in milliseconds. The value MAY be zero prior to the
sender having calculated a round-trip time estimate. The value
SHOULD be set to zero on non-IP-TFS enabled SAs.
Delay:
A 16 bit value specifying the delay in milliseconds incurred
between the receiver receiving the "LastSeqNum" packet and the
sending of this acknowledgement of it.
LossEventRate: LossEventRate:
A 32 bit value specifying the inverse of the current loss event A 32 bit value specifying the inverse of the current loss event
rate as calculated by the receiver. A value of zero indicates no rate as calculated by the receiver. A value of zero indicates no
loss. Otherwise the loss event rate is "1/LossEventRate". loss. Otherwise the loss event rate is "1/LossEventRate".
LastSeqNum: RTT:
A 32 bit value containing the lower 32 bits of the largest A 22 bit value specifying the sender's current round-trip time
sequence number last received. This is the latest in the sequence estimate in microseconds. The value MAY be zero prior to the
not necessarily the most recent (in the case of re-ordering of sender having calculated a round-trip time estimate. The value
packets it may be less recent). When determining largest and 64 SHOULD be set to zero on non-IP-TFS enabled SAs. If the value is
bit extended sequence numbers are in use, the upper 32 bits should equal to or larger than "0x3FFFFF" it MUST be set to "0x3FFFFF".
be used during the comparison.
Echo Delay:
A 21 bit value specifying the delay in microseconds incurred
between the receiver first receiving the "TVal" value which it is
sending back in "TEcho". If the value is equal to or larger than
"0x1FFFFF" it MUST be set to "0x1FFFFF".
Transmit Delay:
A 21 bit value specifying the transmission delay in microseconds.
This is the fixed (or average) delay on the receiver between it
sending packets on the IPTFS tunnel. If the value is equal to or
larger than "0x1FFFFF" it MUST be set to "0x1FFFFF".
TVal:
An opaque 32 bit value that will be echoed back by the receiver in
later packets in the "TEcho" field, along with a "Delay" value of
how long that echo took.
TEcho:
The opaque 32 bit value from a received packet's "TVal" field.
The received "TVal" is placed in "TEcho" along with a "Delay"
value indicating how long it has been since receiving the "TVal"
value.
DataBlocks: DataBlocks:
Variable number of octets that begins with the start of a data Variable number of octets that begins with the start of a data
block, or the continuation of a previous data block, followed by block, or the continuation of a previous data block, followed by
zero or more additional data blocks. For the special case of zero or more additional data blocks. For the special case of
sending congestion control information on an non-IP-TFS enabled SA sending congestion control information on an non-IP-TFS enabled SA
this value MUST be empty (i.e., be zero octets long). this value MUST be empty (i.e., be zero octets long).
6.1.3. Data Blocks 6.1.3. Data Blocks
skipping to change at page 18, line 20 skipping to change at page 19, line 20
8. Security Considerations 8. Security Considerations
This document describes a mechanism to add Traffic Flow This document describes a mechanism to add Traffic Flow
Confidentiality to IP traffic. Use of this mechanism is expected to Confidentiality to IP traffic. Use of this mechanism is expected to
increase the security of the traffic being transported. Other than increase the security of the traffic being transported. Other than
the additional security afforded by using this mechanism, IP-TFS the additional security afforded by using this mechanism, IP-TFS
utilizes the security protocols [RFC4303] and [RFC7296] and so their utilizes the security protocols [RFC4303] and [RFC7296] and so their
security considerations apply to IP-TFS as well. security considerations apply to IP-TFS as well.
As noted previously in Section 2.5.2, for TFC to be fully maintained As noted previously in Section 2.4.2, for TFC to be fully maintained
the encapsulated traffic flow should not be affecting network the encapsulated traffic flow should not be affecting network
congestion in a predictable way, and if it would be then non- congestion in a predictable way, and if it would be then non-
congestion controlled mode use should be considered instead. congestion controlled mode use should be considered instead.
9. References 9. References
9.1. Normative References 9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
skipping to change at page 21, line 10 skipping to change at page 22, line 10
at the IP data block immediately following the IP-TFS header. The at the IP data block immediately following the IP-TFS header. The
following packet ESP2s "BlockOffset" points inward 100 octets to the following packet ESP2s "BlockOffset" points inward 100 octets to the
start of the 60 octet data block. The third encapsulating packet start of the 60 octet data block. The third encapsulating packet
ESP3 contains the middle portion of the 4000 octet data block so the ESP3 contains the middle portion of the 4000 octet data block so the
offset points past its end and into the forth encapsulating packet. offset points past its end and into the forth encapsulating packet.
The fourth packet ESP4s offset is 1400 pointing at the padding which The fourth packet ESP4s offset is 1400 pointing at the padding which
follows the completion of the continued 4000 octet packet. follows the completion of the continued 4000 octet packet.
Appendix B. A Send and Loss Event Rate Calculation Appendix B. A Send and Loss Event Rate Calculation
The current best practice indicates that congestion control should be The current best practice indicates that congestion control SHOULD be
done in a TCP friendly way. A TCP friendly congestion control done in a TCP friendly way. A TCP friendly congestion control
algorithm is described in [RFC5348]. For this IP-TFS use case (as algorithm is described in [RFC5348]. For this IP-TFS use case (as
with [RFC4342]) the (fixed) packet size is used as the segment size with [RFC4342]) the (fixed) packet size is used as the segment size
for the algorithm. The formula for the send rate is then as follows: for the algorithm. The main formula in the algorithm for the send
rate is then as follows:
1 1
X_Pps = ----------------------------------------------- X = -----------------------------------------------
R * (sqrt(2*p/3) + 12*sqrt(3*p/8)*p*(1+32*p^2)) R * (sqrt(2*p/3) + 12*sqrt(3*p/8)*p*(1+32*p^2))
Where "X_Pps" is the send rate in packets per second, "R" is the Where "X" is the send rate in packets per second, "R" is the round
round trip time estimate and "p" is the loss event rate (the inverse trip time estimate and "p" is the loss event rate (the inverse of
of which is provided by the receiver). which is provided by the receiver).
The IP-TFS receiver, having the RTT estimate from the sender MAY use In addition the algorithm in [RFC5348] also uses an "X_recv" value
the same method as described in [RFC4342] to collect the loss (the receiver's receive rate). For IP-TFS one MAY set this value
intervals and calculate the loss event rate value using the weighted according to the sender's current tunnel send-rate ("X").
average as indicated. The receiver communicates the inverse of this
value back to the sender in the IPTFS_PROTOCOL payload header field The IP-TFS receiver, having the RTT estimate from the sender can use
"LossEventRate". the same method as described in [RFC5348] and [RFC4342] to collect
the loss intervals and calculate the loss event rate value using the
weighted average as indicated. The receiver communicates the inverse
of this value back to the sender in the IPTFS_PROTOCOL payload header
field "LossEventRate".
The IP-TFS sender now has both the "R" and "p" values and can The IP-TFS sender now has both the "R" and "p" values and can
calculate the correct sending rate ("X_Pps"). If following [RFC5348] calculate the correct sending rate. If following [RFC5348] the
the sender SHOULD also use the slow start mechanism described therein sender SHOULD also use the slow start mechanism described therein
when the IP-TFS SA is first established. when the IP-TFS SA is first established.
Appendix C. Comparisons of IP-TFS Appendix C. Comparisons of IP-TFS
C.1. Comparing Overhead C.1. Comparing Overhead
C.1.1. IP-TFS Overhead C.1.1. IP-TFS Overhead
The overhead of IP-TFS is 40 bytes per outer packet. Therefore the The overhead of IP-TFS is 40 bytes per outer packet. Therefore the
octet overhead per inner packet is 40 divided by the number of outer octet overhead per inner packet is 40 divided by the number of outer
 End of changes. 30 change blocks. 
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