< draft-amend-tsvwg-multipath-dccp-01.txt   draft-amend-tsvwg-multipath-dccp-02.txt >
Transport Area Working Group M. Amend Transport Area Working Group M. Amend
Internet-Draft Deutsche Telekom Internet-Draft E. Bogenfeld
Intended status: Experimental A. Brunstrom Intended status: Experimental Deutsche Telekom
Expires: September 12, 2019 A. Kassler Expires: January 9, 2020 A. Brunstrom
A. Kassler
Karlstad University Karlstad University
V. Rakocevic V. Rakocevic
City University of London City University of London
March 11, 2019 July 08, 2019
DCCP Extensions for Multipath Operation with Multiple Addresses DCCP Extensions for Multipath Operation with Multiple Addresses
draft-amend-tsvwg-multipath-dccp-01 draft-amend-tsvwg-multipath-dccp-02
Abstract Abstract
DCCP communication is currently restricted to a single path per DCCP communication is currently restricted to a single path per
connection, yet multiple paths often exist between peers. The connection, yet multiple paths often exist between peers. The
simultaneous use of these multiple paths for a DCCP session could simultaneous use of these multiple paths for a DCCP session could
improve resource usage within the network and, thus, improve user improve resource usage within the network and, thus, improve user
experience through higher throughput and improved resilience to experience through higher throughput and improved resilience to
network failure. network failure.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on September 12, 2019. This Internet-Draft will expire on January 9, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Multipath DCCP in the Networking Stack . . . . . . . . . 3 1.1. Multipath DCCP in the Networking Stack . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.3. MP-DCCP Concept . . . . . . . . . . . . . . . . . . . . . 3 1.3. MP-DCCP Concept . . . . . . . . . . . . . . . . . . . . . 3
1.4. Differences from Multipath TCP . . . . . . . . . . . . . 4 1.4. Differences from Multipath TCP . . . . . . . . . . . . . 4
1.5. Requirements Language . . . . . . . . . . . . . . . . . . 6 1.5. Requirements Language . . . . . . . . . . . . . . . . . . 7
2. Operation Overview . . . . . . . . . . . . . . . . . . . . . 6 2. Operation Overview . . . . . . . . . . . . . . . . . . . . . 7
3. MP-DCCP Protocol . . . . . . . . . . . . . . . . . . . . . . 6 3. MP-DCCP Protocol . . . . . . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5. Interactions with Middleboxes . . . . . . . . . . . . . . . . 7 5. Interactions with Middleboxes . . . . . . . . . . . . . . . . 7
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
8. Informative References . . . . . . . . . . . . . . . . . . . 8 8. Informative References . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
Multipath DCCP (MP-DCCP) is a set of extensions to regular DCCP Multipath DCCP (MP-DCCP) is a set of extensions to regular DCCP
[RFC4340], which enables a transport connection to operate across [RFC4340], which enables a transport connection to operate across
multiple paths simultaneously. DCCP multipath operations is multiple paths simultaneously. DCCP multipath operations is
suggested in the context of ongoing 3GPP work on 5G multi-access suggested in the context of ongoing 3GPP work on 5G multi-access
solutions [draft-amend-tsvwg-multipath-framework-mpdccp] and for solutions [I-D.amend-tsvwg-multipath-framework-mpdccp] and for hybrid
hybrid access networks [draft-lhwxz-hybrid-access-network- access networks [I-D.lhwxz-hybrid-access-network-architecture][I-D.mu
architecture, draft-muley-network-based-bonding-hybrid-access]. It ley-network-based-bonding-hybrid-access]. It can be applied for
can be applied for load-balancing, seamless session handover and load-balancing, seamless session handover and aggregation purposes
aggregation purposes (referred to as steering, switching and (referred to as steering, switching and splitting in 3GPP terminology
splitting in 3GPP terminology [3GPP, TR 23.793]). [TR23.793]).
This document presents the protocol changes required to add multipath This document presents the protocol changes required to add multipath
capability to DCCP; specifically, those for signaling and setting up capability to DCCP; specifically, those for signaling and setting up
multiple paths ("subflows"), managing these subflows, reassembly of multiple paths ("subflows"), managing these subflows, reassembly of
data, and termination of sessions. data, and termination of sessions.
1.1. Multipath DCCP in the Networking Stack 1.1. Multipath DCCP in the Networking Stack
MP-DCCP operates at the transport layer and aims to be transparent to MP-DCCP operates at the transport layer and aims to be transparent to
both higher and lower layers. It is a set of additional features on both higher and lower layers. It is a set of additional features on
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+-------------------------------+ +-------------------------------+
| Application | | Application |
+---------------+ +-------------------------------+ +---------------+ +-------------------------------+
| Application | | MP-DCCP | | Application | | MP-DCCP |
+---------------+ + - - - - - - - + - - - - - - - + +---------------+ + - - - - - - - + - - - - - - - +
| DCCP | |Subflow (DCCP) |Subflow (DCCP) | | DCCP | |Subflow (DCCP) |Subflow (DCCP) |
+---------------+ +-------------------------------+ +---------------+ +-------------------------------+
| IP | | IP | IP | | IP | | IP | IP |
+---------------+ +-------------------------------+ +---------------+ +-------------------------------+
Figure 1: Comparison of Standard DCCP and MP-DCCP Protocol Stacks Figure 1: Comparison of Standard DCCP and MP-DCCP Protocol Stacks
1.2. Terminology 1.2. Terminology
[Tbd], could be similar to [RFC6824] [Tbd], could be similar to [RFC6824]
1.3. MP-DCCP Concept 1.3. MP-DCCP Concept
Host A Host B Host A Host B
------------------------ ------------------------ ------------------------ ------------------------
Address A1 Address A2 Address B1 Address B2 Address A1 Address A2 Address B1 Address B2
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| merge individual DCCP flows to one multipath connection | merge individual DCCP flows to one multipath connection
| | | | | | | |
Figure 2: Example MP-DCCP Usage Scenario Figure 2: Example MP-DCCP Usage Scenario
1.4. Differences from Multipath TCP 1.4. Differences from Multipath TCP
Multipath DCCP is similar to Multipath TCP [RFC6824], in that it Multipath DCCP is similar to Multipath TCP [RFC6824], in that it
extends the related basic DCCP transport protocol [RFC4340] with extends the related basic DCCP transport protocol [RFC4340] with
multipath capabilities in the same way as Multipath TCP extends TCP multipath capabilities in the same way as Multipath TCP extends TCP
[RFC793]. However, mainly dominated by the basic protocols TCP and [RFC0793]. However, mainly dominated by the basic protocols TCP and
DCPP, the transport characteristics are different. DCPP, the transport characteristics are different.
Table 1 compares the protocol characteristics of TCP and DCCP, which Table 1 compares the protocol characteristics of TCP and DCCP, which
are by nature inherited by their respective multipath extensions. A are by nature inherited by their respective multipath extensions. A
major difference lies in the delivery of payload, which is for TCP an major difference lies in the delivery of payload, which is for TCP an
exact copy of the generated byte-stream. DCCP behaves contrary and exact copy of the generated byte-stream. DCCP behaves contrary and
does not guarantee to transmit any payload nor the order of delivery. does not guarantee to transmit any payload nor the order of delivery.
Since this is mainly affecting the receiving endpoint of a TCP or Since this is mainly affecting the receiving endpoint of a TCP or
DCCP communication, many similarities on sender side can be stated. DCCP communication, many similarities on sender side can be stated.
Both transport protocols share the 3-way initiation of a Both transport protocols share the 3-way initiation of a
communication and both exploit a congestion control to adapt to path communication and both exploit a congestion control to adapt to path
characteristics. characteristics.
+----------------+--------------+--------------+ +----------------------+-----------------+--------------------------+
| Feature | TCP | DCCP | | Feature | TCP | DCCP |
+----------------+--------------+--------------+ +----------------------+-----------------+--------------------------+
| Full-Duplex | yes | yes | | Full-Duplex | yes | yes |
+----------------+--------------+--------------+ +----------------------+-----------------+--------------------------+
| Connection- | yes | yes | | Connection- Oriented | yes | yes |
| Oriented | | | +----------------------+-----------------+--------------------------+
+----------------+--------------+--------------+ | Header option space | 40 bytes | < 1008 bytes or PMTU |
| Header option | 40 | < 1008 bytes | +----------------------+-----------------+--------------------------+
| space | bytes | or PMTU | | Data transfer | reliable | unreliable |
+----------------+--------------+--------------+ +----------------------+-----------------+--------------------------+
| Data transfer | reliable | unreliable | | Packet-loss handling | re- | report only |
+----------------+--------------+--------------+ | | transmission | |
| Packet-loss | re- | report | +----------------------+-----------------+--------------------------+
| handling | transmission | only | | Ordered data | yes | no |
+----------------+--------------+--------------+ | delivery | | |
| Ordered data | yes | no | +----------------------+-----------------+--------------------------+
| delivery | | | | Sequence numbers | one per byte | one per PDU |
+----------------+--------------+--------------+ +----------------------+-----------------+--------------------------+
| Sequence | one per | one per | | Flow control | yes | no |
| numbers | byte | PDU | +----------------------+-----------------+--------------------------+
+----------------+--------------+--------------+ | Congestion control | yes | yes |
| Flow control | yes | no | +----------------------+-----------------+--------------------------+
+----------------+--------------+--------------+ | ECN support | yes | yes |
| Congestion | yes | yes | +----------------------+-----------------+--------------------------+
| control | | | | Selective ACK | yes | depends on congestion |
+----------------+--------------+--------------+ | | | control |
| ECN support | yes | yes | +----------------------+-----------------+--------------------------+
+----------------+--------------+--------------+ | Fix message | no | yes |
| | | depends on | | boundaries | | |
| Selective ACK | yes | congestion | +----------------------+-----------------+--------------------------+
| | | control | | Path MTU discovery | yes | yes |
+----------------+--------------+--------------+ +----------------------+-----------------+--------------------------+
| Fix message | no | yes | | Fragmentation | yes | no |
| boundaries | | | +----------------------+-----------------+--------------------------+
+----------------+--------------+--------------+ | SYN flood protection | yes | no |
| Path MTU | yes | yes | +----------------------+-----------------+--------------------------+
| discovery | | | | Half-open | yes | no |
+----------------+--------------+--------------+ | connections | | |
| Fragmentation | yes | no | +----------------------+-----------------+--------------------------+
+----------------+--------------+--------------+
| SYN flood | yes | no |
| protection | | |
+----------------+--------------+--------------+
| Half-open | yes | no |
| connections | | |
+----------------+--------------+--------------+
Table 1: TCP and DCCP protocol comparison
Consequently, the multipath features, shown in Table 2, are the same Table 1: TCP and DCCP protocol comparison
for support of volatile paths, session handover and path aggregation
Consequently, the multipath features, shown in Table 2, are the same,
supporting volatile paths, session handover and path aggregation
capabilities. All of them profit by the existence of congestion capabilities. All of them profit by the existence of congestion
control. control.
+----------------------------------------------+ +--------------------------+---------------------+------------------+
| Feature | MP-TCP | MP-DCCP | | Feature | MP-TCP | MP-DCCP |
+----------------+--------------+--------------+ +--------------------------+---------------------+------------------+
| Volatile paths | yes | yes | | Volatile paths | yes | yes |
+----------------+--------------+--------------+ +--------------------------+---------------------+------------------+
| Robust session | no | yes | | Robust session | no | yes |
| establishment | | | | establishment | | |
+----------------+--------------+--------------+ +--------------------------+---------------------+------------------+
| Data | yes | optional | | Data reassembly | yes | optional / |
| reassembly | | | | | | modular |
+----------------+--------------+--------------+ +--------------------------+---------------------+------------------+
| Expandability | limited by | flexible | | Expandability | limited by TCP | flexible |
| | TCP header | | | | header | |
+----------------+--------------+--------------+ +--------------------------+---------------------+------------------+
| Session | yes | yes | | Session handover | yes | yes |
| handover | | | +--------------------------+---------------------+------------------+
+----------------+--------------+--------------+ | Path aggregation | yes | yes |
| Path | yes | yes | +--------------------------+---------------------+------------------+
| aggregation | | |
+----------------+--------------+--------------+ Table 2: MPTCP and MP-DCCP protocol comparison
Table 2: MPTCP and MP-DCCP protocol comparison
Therefore the sender logic is not much different between MP-DCCP and Therefore the sender logic is not much different between MP-DCCP and
MPTCP, even if the multipath session initiation differs. MP-DCCP MPTCP, even if the multipath session initiation differs. MP-DCCP
inherits a robust session establishment feature, which guarantees inherits a robust session establishment feature, which guarantees
communication establishment if at least one functional path is communication establishment if at least one functional path is
available. MP-TCP relies on an initial path, which has to work; available. MP-TCP relies on an initial path, which has to work;
otherwise no communication can be established. otherwise no communication can be established.
The receiver side for MP-DCCP has to deal with the unreliable The receiver side for MP-DCCP has to deal with the unreliable
transport character of DCCP and a possible re-assembly of the data transport character of DCCP and a possible re-assembly of the data
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o Robust MP-DCCP session establishment (no dependency on an initial o Robust MP-DCCP session establishment (no dependency on an initial
path setup) path setup)
4. Security Considerations 4. Security Considerations
[Tbd] [Tbd]
5. Interactions with Middleboxes 5. Interactions with Middleboxes
[Tbd], should mention standardized technologies like [RFC5597] or [Tbd], should mention standardized technologies like [RFC5597] or
[RFC6773] and U-DCCP [draft-amend-tsvwg-dccp-udp-header-conversion] [RFC6773] and U-DCCP [I-D.amend-tsvwg-dccp-udp-header-conversion]
6. Acknowledgments 6. Acknowledgments
1. Notes 1. Notes
This document is inspired by Multipath TCP [RFC6824] and some text This document is inspired by Multipath TCP [RFC6824] and some text
passages for the -00 version of the draft are copied almost passages for the -00 version of the draft are copied almost
unmodified. unmodified.
7. IANA Considerations 7. IANA Considerations
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o overall sequence number for restoring purposes o overall sequence number for restoring purposes
o sender time measurements for restoring purposes o sender time measurements for restoring purposes
o scheduler preferences o scheduler preferences
o reordering preferences o reordering preferences
8. Informative References 8. Informative References
[I-D.amend-tsvwg-multipath-framework-mpdccp] [I-D.amend-tsvwg-dccp-udp-header-conversion]
Amend, M., Brunstrom, A., Kassler, A., and V. Rakocevic, Amend, M., Brunstrom, A., Kassler, A., and V. Rakocevic,
"IP compatible multipath framework for heterogeneous "Lossless and overhead free DCCP - UDP header conversion
access networks", draft-amend-tsvwg-multipath-framework- (U-DCCP)", draft-amend-tsvwg-dccp-udp-header-conversion-01
mpdccp-00 (work in progress), March 2019. (work in progress), July 2019.
[I-D.amend-tsvwg-multipath-framework-mpdccp]
Amend, M., Bogenfeld, E., Brunstrom, A., Kassler, A., and
V. Rakocevic, "A multipath framework for UDP traffic over
heterogeneous access networks", draft-amend-tsvwg-
multipath-framework-mpdccp-01 (work in progress), July
2019.
[I-D.lhwxz-hybrid-access-network-architecture] [I-D.lhwxz-hybrid-access-network-architecture]
Leymann, N., Heidemann, C., Wasserman, M., Xue, L., and M. Leymann, N., Heidemann, C., Wasserman, M., Xue, L., and M.
Zhang, "Hybrid Access Network Architecture", draft-lhwxz- Zhang, "Hybrid Access Network Architecture", draft-lhwxz-
hybrid-access-network-architecture-02 (work in progress), hybrid-access-network-architecture-02 (work in progress),
January 2015. January 2015.
[I-D.muley-network-based-bonding-hybrid-access] [I-D.muley-network-based-bonding-hybrid-access]
Muley, P., Henderickx, W., Geng, L., Liu, H., Cardullo, Muley, P., Henderickx, W., Geng, L., Liu, H., Cardullo,
L., Newton, J., Seo, S., Draznin, S., and B. Patil, L., Newton, J., Seo, S., Draznin, S., and B. Patil,
skipping to change at page 9, line 10 skipping to change at page 9, line 42
[RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A [RFC6773] Phelan, T., Fairhurst, G., and C. Perkins, "DCCP-UDP: A
Datagram Congestion Control Protocol UDP Encapsulation for Datagram Congestion Control Protocol UDP Encapsulation for
NAT Traversal", RFC 6773, DOI 10.17487/RFC6773, November NAT Traversal", RFC 6773, DOI 10.17487/RFC6773, November
2012, <https://www.rfc-editor.org/info/rfc6773>. 2012, <https://www.rfc-editor.org/info/rfc6773>.
[RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure, [RFC6824] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
"TCP Extensions for Multipath Operation with Multiple "TCP Extensions for Multipath Operation with Multiple
Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013, Addresses", RFC 6824, DOI 10.17487/RFC6824, January 2013,
<https://www.rfc-editor.org/info/rfc6824>. <https://www.rfc-editor.org/info/rfc6824>.
Authors' Addresses [TR23.793]
3GPP, "Study on access traffic steering, switch and
splitting support in the 5G System (5GS) architecture",
December 2018.
Authors' Addresses
Markus Amend Markus Amend
Deutsche Telekom Deutsche Telekom
T-Online-Allee 1 Deutsche-Telekom-Allee 7
Darmstadt 64295 Darmstadt
Germany Germany
Email: Markus.Amend@telekom.de Email: Markus.Amend@telekom.de
Eckard Bogenfeld
Deutsche Telekom
Deutsche-Telekom-Allee 7
64295 Darmstadt
Germany
Email: Eckard.Bogenfeld@telekom.de
Anna Brunstrom Anna Brunstrom
Karlstad University Karlstad University
Universitetsgatan 2 Universitetsgatan 2
651 88 Karlstad 651 88 Karlstad
Sweden Sweden
Email: anna.brunstrom@kau.se Email: anna.brunstrom@kau.se
Andreas Kassler Andreas Kassler
Karlstad University Karlstad University
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