draft-ietf-tcpm-2140bis-03.txt   draft-ietf-tcpm-2140bis-04.txt 
TCPM WG J. Touch TCPM WG J. Touch
Internet Draft Independent Internet Draft Independent
Intended status: Informational M. Welzl Intended status: Informational M. Welzl
Obsoletes: 2140 S. Islam Obsoletes: 2140 S. Islam
Expires: October 2020 University of Oslo Expires: October 2020 University of Oslo
April 24, 2020 April 29, 2020
TCP Control Block Interdependence TCP Control Block Interdependence
draft-ietf-tcpm-2140bis-03.txt draft-ietf-tcpm-2140bis-04.txt
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.
This document may contain material from IETF Documents or IETF This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this 10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow material may not have granted the IETF Trust the right to allow
skipping to change at page 1, line 45 skipping to change at page 1, line 45
months and may be updated, replaced, or obsoleted by other documents months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress." reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html http://www.ietf.org/shadow.html
This Internet-Draft will expire on October 24, 2020. This Internet-Draft will expire on October 29, 2020.
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 49 skipping to change at page 2, line 49
Table of Contents Table of Contents
1. Introduction...................................................3 1. Introduction...................................................3
2. Conventions Used in This Document..............................4 2. Conventions Used in This Document..............................4
3. Terminology....................................................4 3. Terminology....................................................4
4. The TCP Control Block (TCB)....................................4 4. The TCP Control Block (TCB)....................................4
5. TCB Interdependence............................................5 5. TCB Interdependence............................................5
6. Temporal Sharing...............................................6 6. Temporal Sharing...............................................6
6.1. Initialization of the new TCB................................6 6.1. Initialization of the new TCB................................6
6.2. Updates to the new TCB.......................................7 6.2. Updates to the new TCB.......................................7
6.3. Discussion...................................................8 6.3. Discussion...................................................7
7. Ensemble Sharing...............................................9 7. Ensemble Sharing...............................................9
7.1. Initialization of a new TCB..................................9 7.1. Initialization of a new TCB..................................9
7.2. Updates to the new TCB......................................10 7.2. Updates to the new TCB......................................10
7.3. Discussion..................................................11 7.3. Discussion..................................................11
8. Compatibility Issues..........................................12 8. Compatibility Issues..........................................12
8.1. Traversing the same network path............................13 8.1. Traversing the same network path............................12
8.2. State dependence............................................13 8.2. State dependence............................................13
8.3. Problems with IP sharing....................................14 8.3. Problems with IP sharing....................................13
9. Implications..................................................14 9. Implications..................................................13
9.1. Layering....................................................14 9.1. Layering....................................................14
9.2. Other possibilities.........................................15 9.2. Other possibilities.........................................14
10. Implementation Observations..................................15 10. Implementation Observations..................................15
11. Updates to RFC 2140..........................................16 11. Updates to RFC 2140..........................................16
12. Security Considerations......................................17 12. Security Considerations......................................16
13. IANA Considerations..........................................17 13. IANA Considerations..........................................17
14. References...................................................18 14. References...................................................17
14.1. Normative References....................................18 14.1. Normative References....................................17
14.2. Informative References..................................18 14.2. Informative References..................................18
15. Acknowledgments..............................................21 15. Acknowledgments..............................................20
16. Change log...................................................21 16. Change log...................................................20
Appendix A : TCB Sharing History.................................24 Appendix A : TCB Sharing History.................................23
Appendix B : TCP Option Sharing and Caching......................25 Appendix B : TCP Option Sharing and Caching......................24
Appendix C : Automating the Initial Window in TCP over Long Appendix C : Automating the Initial Window in TCP over Long
Timescales.......................................................27 Timescales.......................................................26
C.1. Introduction.............................................27 C.1. Introduction.............................................26
C.2. Design Considerations....................................27 C.2. Design Considerations....................................26
C.3. Proposed IW Algorithm....................................28 C.3. Proposed IW Algorithm....................................27
C.4. Discussion...............................................31 C.4. Discussion...............................................30
C.5. Observations.............................................32 C.5. Observations.............................................31
1. Introduction 1. Introduction
TCP is a connection-oriented reliable transport protocol layered TCP is a connection-oriented reliable transport protocol layered
over IP [RFC793]. Each TCP connection maintains state, usually in a over IP [RFC793]. Each TCP connection maintains state, usually in a
data structure called the TCP Control Block (TCB). The TCB contains data structure called the TCP Control Block (TCB). The TCB contains
information about the connection state, its associated local information about the connection state, its associated local
process, and feedback parameters about the connection's transmission process, and feedback parameters about the connection's transmission
properties. As originally specified and usually implemented, most properties. As originally specified and usually implemented, most
TCB information is maintained on a per-connection basis. Some TCB information is maintained on a per-connection basis. Some
skipping to change at page 6, line 15 skipping to change at page 6, line 15
6. Temporal Sharing 6. Temporal Sharing
The TCB data cache is accessed in two ways: it is read to initialize The TCB data cache is accessed in two ways: it is read to initialize
new TCBs and written when more current per-host state is available. new TCBs and written when more current per-host state is available.
6.1. Initialization of the new TCB 6.1. Initialization of the new TCB
TCBs for new connections can be initialized using context from past TCBs for new connections can be initialized using context from past
connections as follows: connections as follows:
TEMPORAL SHARING - TCB Initialization TEMPORAL SHARING - TCB Initialization
Cached TCB New TCB Cached TCB New TCB
-------------------------------------- --------------------------------------
old_MMS_S old_MMS_S or not cached old_MMS_S old_MMS_S or not cached
old_MMS_R old_MMS_R or not cached old_MMS_R old_MMS_R or not cached
old_sendMSS old_sendMSS old_sendMSS old_sendMSS
old_PMTU old_PMTU old_PMTU old_PMTU
old_RTT old_RTT old_RTT old_RTT
old_RTTvar old_RTTvar old_RTTvar old_RTTvar
old_option (option specific) old_option (option specific)
old_ssthresh old_ssthresh old_ssthresh old_ssthresh
old_snd_cwnd old_snd_cwnd old_snd_cwnd old_snd_cwnd
The table below gives an overview of option-specific information The table below gives an overview of option-specific information
that can be shared. Additional information on some specific TCP that can be shared. Additional information on some specific TCP
options and sharing is provided in 0. options and sharing is provided in Appendix B.
TEMPORAL SHARING - Option Info Initialization TEMPORAL SHARING - Option Info Initialization
Cached New Cached New
---------------------------------------- ------------------------------------
old_TFO_Cookie old_TFO_Cookie old_TFO_Cookie old_TFO_Cookie
old_TFO_Failure old_TFO_Failure old_TFO_Failure old_TFO_Failure
6.2. Updates to the new TCB 6.2. Updates to the new TCB
During the connection, the associated TCB can be updated based on During the connection, the associated TCB can be updated based on
particular events, as shown below: particular events, as shown below:
TEMPORAL SHARING - Cache Updates TEMPORAL SHARING - Cache Updates
Cached TCB Current TCB when? New Cached TCB Cached TCB Current TCB when? New Cached TCB
------------------------------------------------------ ----------------------------------------------------------
old_MMS_S curr_ MMS_S OPEN curr MMS_S old_MMS_S curr_MMS_S OPEN curr_MMS_S
old_MMS_R curr_ MMS_R OPEN curr_MMS_R old_MMS_R curr_MMS_R OPEN curr_MMS_R
old_sendMSS curr_sendMSS MSSopt curr_sendMSS old_sendMSS curr_sendMSS MSSopt curr_sendMSS
old_PMTU curr_PMTU PMTUD curr_PMTU old_PMTU curr_PMTU PMTUD curr_PMTU
old_RTT curr_RTT CLOSE merge(curr,old) old_RTT curr_RTT CLOSE merge(curr,old)
old_RTTvar curr_RTTvar CLOSE merge(curr,old) old_RTTvar curr_RTTvar CLOSE merge(curr,old)
old_option curr option ESTAB (depends on option) old_option curr_option ESTAB (depends on option)
old_ssthresh curr_ssthresh CLOSE merge(curr,old) old_ssthresh curr_ssthresh CLOSE merge(curr,old)
old_snd_cwnd curr_snd_cwnd CLOSE merge(curr,old) old_snd_cwnd curr_snd_cwnd CLOSE merge(curr,old)
The table below gives an overview of option-specific information The table below gives an overview of option-specific information
that can be similarly shared. that can be similarly shared.
TEMPORAL SHARING - Option Info Updates TEMPORAL SHARING - Option Info Updates
Cached Current when? New Cached Cached Current when? New Cached
---------------------------------------------------------------- ---------------------------------------------------------
old_TFO_Cookie old_TFO_Cookie ESTAB old_TFO_Cookie old_TFO_Cookie old_TFO_Cookie ESTAB old_TFO_Cookie
old_TFO_Failure old_TFO_Failure ESTAB old_TFO_Failure old_TFO_Failure old_TFO_Failure ESTAB old_TFO_Failure
6.3. Discussion 6.3. Discussion
There is no particular benefit to caching MMS_S and MMS R as these There is no particular benefit to caching MMS_S and MMS_R as these
are reported by the local IP stack. Caching sendMSS and PMTU is are reported by the local IP stack. Caching sendMSS and PMTU is
trivial; reported values are cached, and the most recent values are trivial; reported values are cached, and the most recent values are
used. The cache is updated when the MSS option is received in a SYN used. The cache is updated when the MSS option is received in a SYN
or after PMTUD (i.e., when an ICMPv4 Fraqmentation Needed [RFC1191] or after PMTUD (i.e., when an ICMPv4 Fraqmentation Needed [RFC1191]
or ICMPv6 Packet Too Big message is received [RFC8201] or the or ICMPv6 Packet Too Big message is received [RFC8201] or the
equivalent is inferred, e.g. as from PLPMTUD [RFC4821]), equivalent is inferred, e.g. as from PLPMTUD [RFC4821]),
respectively, so the cache always has the most recent values from respectively, so the cache always has the most recent values from
any connection. For sendMSS, the cache is consulted only at any connection. For sendMSS, the cache is consulted only at
connection establishment and not otherwise updated, which means that connection establishment and not otherwise updated, which means that
MSS options do not affect current connections. The default sendMSS MSS options do not affect current connections. The default sendMSS
skipping to change at page 10, line 5 skipping to change at page 9, line 30
example, although MSS and RTT values can be shared by copying, it example, although MSS and RTT values can be shared by copying, it
may not be appropriate to simply copy congestion window or ssthresh may not be appropriate to simply copy congestion window or ssthresh
information; instead, the new values can be a function (f) of the information; instead, the new values can be a function (f) of the
cumulative values and the number of connections (N). cumulative values and the number of connections (N).
7.1. Initialization of a new TCB 7.1. Initialization of a new TCB
TCBs for new connections can be initialized using context from TCBs for new connections can be initialized using context from
concurrent connections as follows: concurrent connections as follows:
ENSEMBLE SHARING - TCB Initialization ENSEMBLE SHARING - TCB Initialization
Cached TCB New TCB
--------------------------------
old_MMS_S old_MMS_S
old_MMS_R old_MMS_R Cached TCB New TCB
------------------------------------------
old_MMS_S old_MMS_S
old_sendMSS old_sendMSS old_MMS_R old_MMS_R
old_PMTU old_PMTU old_sendMSS old_sendMSS
old_RTT old_RTT old_PMTU old_PMTU
old_RTTvar old_RTTvar old_RTT old_RTT
old ssthresh sum f(old ssthresh sum, N) old_RTTvar old_RTTvar
old snd_cwnd sum f(old snd cwnd sum, N) sum(old_ssthresh) f(sum(old_ssthresh), N)
old_option (option-specific) sum(old_snd_cwnd) f(sum(old_snd_cwnd), N)
_
old_option (option specific)
The table below gives an overview of option-specific information The table below gives an overview of option-specific information
that can be similarly shared. that can be similarly shared.
ENSEMBLE SHARING - Option Info Initialization ENSEMBLE SHARING - Option Info Initialization
Cached New Cached New
---------------------------------------- ------------------------------------
old_TFO_Cookie old_TFO_Cookie old_TFO_Cookie old_TFO_Cookie
old_TFO_Failure old_TFO_Failure old_TFO_Failure old_TFO_Failure
7.2. Updates to the new TCB 7.2. Updates to the new TCB
During the connection, the associated TCB can be updated based on During the connection, the associated TCB can be updated based on
changes to concurrent connections, as shown below: changes to concurrent connections, as shown below:
ENSEMBLE SHARING - Cache Updates ENSEMBLE SHARING - Cache Updates
Cached TCB Current TCB when? New Cached TCB Cached TCB Current TCB when? New Cached TCB
----------------------------------------------------- ---------------------------------------------------------------
old_MMS_S curr_MMS_S OPEN curr_MMS_S old_MMS_S curr_MMS_S OPEN curr_MMS_S
old_MMS_R curr_MMS_R OPEN curr_MMS_R old_MMS_R curr_MMS_R OPEN curr_MMS_R
old_sendMSS curr_sendMSS MSSopt curr_sendMSS old_sendMSS curr_sendMSS MSSopt curr_sendMSS
old_PMTU curr_PMTU PMTUD curr_PMTU old_PMTU curr_PMTU PMTUD curr_PMTU / PLPMTUD
/PLPMTUD
old_RTT curr_RTT update rtt_update(old,curr) old_RTT curr_RTT update rtt_update(old,curr)
old_RTTvar curr_RTTvar update rtt_update(old,curr) old_RTTvar curr_RTTvar update rtt_update(old,curr)
old ssthresh curr ssthresh update adjust sum as appopriate old_ssthresh curr_ssthresh update adjust sum as appropriate
old snd_cwnd curr snd_cwnd update adjust sum as appopriate old_snd_cwnd curr_snd_cwnd update adjust sum as appropriate
old_option curr option (depends) (option specific) old_option curr_option (depends) (option specific)
The table below gives an overview of option-specific information The table below gives an overview of option-specific information
that can be similarly shared. that can be similarly shared.
ENSEMBLE SHARING - Option Info Updates ENSEMBLE SHARING - Option Info Updates
Cached Current when? New Cached Cached Current when? New Cached
---------------------------------------------------------------- ----------------------------------------------------------
old_TFO_Cookie old_TFO_Cookie ESTAB old_TFO_Cookie old_TFO_Cookie old_TFO_Cookie ESTAB old_TFO_Cookie
old_TFO_Failure old_TFO_Failure ESTAB old_TFO_Failure old_TFO_Failure old_TFO_Failure ESTAB old_TFO_Failure
7.3. Discussion 7.3. Discussion
For ensemble sharing, TCB information should be cached as early as For ensemble sharing, TCB information should be cached as early as
possible, sometimes before a connection is closed. Otherwise, possible, sometimes before a connection is closed. Otherwise,
opening multiple concurrent connections may not result in TCB data opening multiple concurrent connections may not result in TCB data
sharing if no connection closes before others open. The amount of sharing if no connection closes before others open. The amount of
work involved in updating the aggregate average should be minimized, work involved in updating the aggregate average should be minimized,
but the resulting value should be equivalent to having all values but the resulting value should be equivalent to having all values
measured within a single connection. The function "rtt_update" in measured within a single connection. The function "rtt_update" in
skipping to change at page 15, line 48 skipping to change at page 15, line 23
optimization is to make that implicit feedback explicit, via optimization is to make that implicit feedback explicit, via
extended information associated with the endpoint IP address and its extended information associated with the endpoint IP address and its
TCP implementation, rather than per-connection state in the TCB. TCP implementation, rather than per-connection state in the TCB.
10. Implementation Observations 10. Implementation Observations
The observation that some TCB state is host-pair specific rather The observation that some TCB state is host-pair specific rather
than application-pair dependent is not new and is a common than application-pair dependent is not new and is a common
engineering decision in layered protocol implementations. Although engineering decision in layered protocol implementations. Although
now deprecated, T/TCP [RFC1644] was the first to propose using now deprecated, T/TCP [RFC1644] was the first to propose using
caches in order to maintain TCB states (see Appendix A for more caches in order to maintain TCB states (see Appendix A).
information).
The table below describes the current implementation status for some The table below describes the current implementation status for some
TCB information in Linux kernel version 4.6, FreeBSD 10 and Windows TCB temporal sharing in Linux kernel version 4.6, FreeBSD 10 and
(as of October 2016). In the table, "shared" only refers to temporal Windows as of October 2016. Ensemble sharing is not yet implemented.
sharing.
CURRENT IMPLEMENTATION STATUS (as of 2016) CURRENT IMPLEMENTATION STATUS (as of 2016)
TCB data Status TCB data Status
----------------------------------------------------------- ------------------------------------------------------------
old MMS_S Not shared old_MMS_S Not shared
old MMS_R Not shared old_MMS_R Not shared
old_sendMSS Cached and shared in Linux (MSS) old_sendMSS Cached and shared in Linux (MSS)
old PMTU Cached and shared in FreeBSD and Windows (PMTU) old_PMTU Cached and shared in FreeBSD and Windows (PMTU)
old_RTT Cached and shared in FreeBSD and Linux old_RTT Cached and shared in FreeBSD and Linux
old_RTTvar Cached and shared in FreeBSD old_RTTvar Cached and shared in FreeBSD
old TFOinfo Cached and shared in Linux and Windows old_TFOinfo Cached and shared in Linux and Windows
old_snd_cwnd Not shared old_snd_cwnd Not shared
old_ssthresh Cached and shared in FreeBSD and Linux: old_ssthresh Cached and shared in FreeBSD and Linux*
FreeBSD: arithmetic
mean of ssthresh and previous value if *Note: In FreeBSD, new ssthresh is the mean of curr_ssthresh and
a previous value exists; previous value if a previous value exists; in Linux, the calculation
Linux: depending on state, depends on state and is max(curr_cwnd/2, old_ssthresh) in most
max(cwnd/2, ssthresh) in most cases cases.
11. Updates to RFC 2140 11. Updates to RFC 2140
This document updates the description of TCB sharing in RFC 2140 and This document updates the description of TCB sharing in RFC 2140 and
its associated impact on existing and new connection state, its associated impact on existing and new connection state,
providing a complete replacement for that document [RFC2140]. It providing a complete replacement for that document [RFC2140]. It
clarifies the previous description and terminology and extends the clarifies the previous description and terminology and extends the
mechanism to its impact on new protocols and mechanisms, including mechanism to its impact on new protocols and mechanisms, including
multipath TCP, fast open, PLPMTUD, NAT, and the TCP Authentication multipath TCP, fast open, PLPMTUD, NAT, and the TCP Authentication
Option. Option.
skipping to change at page 21, line 21 skipping to change at page 20, line 39
received funding from a collaborative research project between the received funding from a collaborative research project between the
University of Oslo and Huawei Technologies Co., Ltd. and were partly University of Oslo and Huawei Technologies Co., Ltd. and were partly
supported by USC/ISI's Postel Center. supported by USC/ISI's Postel Center.
This document was prepared using 2-Word-v2.0.template.dot. This document was prepared using 2-Word-v2.0.template.dot.
16. Change log 16. Change log
This section should be removed upon final publication as an RFC. This section should be removed upon final publication as an RFC.
ietf-04:
- Fix internal cross-reference errors that appeared in ietf-02
- Updated tables to re-center; clarified text
ietf-03:
- Correction of typographic errors, minor rewording in appendices
ietf-02: ietf-02:
- Minor reorganization and correction of typographic errors - Minor reorganization and correction of typographic errors
- Added text to address fingerprinting in Security section - Added text to address fingerprinting in Security section
- Now retains Appendix B and body option tables upon publication - Now retains Appendix B and body option tables upon publication
ietf-01: ietf-01:
- Added Appendix C to address long-timescale temporal adaptation. - Added Appendix C to address long-timescale temporal adaptation
ietf-00: ietf-00:
- Re-issued as draft-ietf-tcpm-2140bis due to WG adoption. - Re-issued as draft-ietf-tcpm-2140bis due to WG adoption.
- Cleaned orphan references to T/TCP, removed incomplete refs - Cleaned orphan references to T/TCP, removed incomplete refs
- Moved references to informative section and updated Sec 2 - Moved references to informative section and updated Sec 2
- Updated to clarify no impact to interoperability - Updated to clarify no impact to interoperability
- Updated appendix B to avoid 2119 language - Updated appendix B to avoid 2119 language
06: 06:
skipping to change at page 22, line 25 skipping to change at page 22, line 4
implementation overview table. implementation overview table.
- Marked entries that are considered safe to share with an - Marked entries that are considered safe to share with an
asterisk (suggestion was to split the table) asterisk (suggestion was to split the table)
- Discussed correct host identification: NATs may make IP - Discussed correct host identification: NATs may make IP
addresses the wrong input, could e.g. use HTTP cookie. addresses the wrong input, could e.g. use HTTP cookie.
- Included MMS_S and MMS_R from RFC1122; fixed the use of MSS and - Included MMS_S and MMS_R from RFC1122; fixed the use of MSS and
MTU MTU
- Added information about option sharing, listed options in
- Added information about option sharing, listed options in 0 Appendix B
Authors' Addresses Authors' Addresses
Joe Touch Joe Touch
Manhattan Beach, CA 90266 Manhattan Beach, CA 90266
USA USA
Phone: +1 (310) 560-0334 Phone: +1 (310) 560-0334
Email: touch@strayalpha.com Email: touch@strayalpha.com
skipping to change at page 27, line 7 skipping to change at page 26, line 7
MSS MSS
TFO negotiation failure (to avoid negotiation retries) TFO negotiation failure (to avoid negotiation retries)
Safe and necessary to keep state: Safe and necessary to keep state:
TFP cookie (if TFO succeeded in the past) TFP cookie (if TFO succeeded in the past)
Appendix C: Automating the Initial Window in TCP over Long Timescales Appendix C: Automating the Initial Window in TCP over Long Timescales
Note: this section is taken verbatim from [To12], updated to refer Note: this section is imported from [To12], updated only to refer to
to itself as an appendix. itself as an appendix.
C.1. Introduction C.1. Introduction
TCP's congestion control algorithm uses an initial window value TCP's congestion control algorithm uses an initial window value
(IW), both as a starting point for new connections and after one RTO (IW), both as a starting point for new connections and after one RTO
or more [RFC2581][RFC2861]. This value has evolved over time, or more [RFC2581][RFC2861]. This value has evolved over time,
originally one maximum segment size (MSS), and increased to the originally one maximum segment size (MSS), and increased to the
lesser of four MSS or 4,380 bytes [RFC3390][RFC5681]. For typical lesser of four MSS or 4,380 bytes [RFC3390][RFC5681]. For typical
Internet connections with an maximum transmission units (MTUs) of Internet connections with an maximum transmission units (MTUs) of
1500 bytes, this permits three segments of 1,460 bytes each. 1500 bytes, this permits three segments of 1,460 bytes each.
 End of changes. 78 change blocks. 
118 lines changed or deleted 124 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/