Internet DRAFT - draft-tuexen-tsvwg-sctp-multipath
draft-tuexen-tsvwg-sctp-multipath
Network Working Group M. Becke
Internet-Draft HAW Hamburg
Intended status: Experimental T. Dreibholz
Expires: 2 September 2024 SimulaMet
N. Ekiz
University of Delaware
J. Iyengar
Franklin and Marshall College
P. Natarajan
Cisco Systems
R. R. Stewart
Netflix
M. Tüxen
Münster Univ. of Appl. Sciences
1 March 2024
Load Sharing for the Stream Control Transmission Protocol (SCTP)
draft-tuexen-tsvwg-sctp-multipath-27
Abstract
The Stream Control Transmission Protocol (SCTP) supports multi-homing
for providing network fault tolerance. However, mainly one path is
used for data transmission. Only timer-based retransmissions are
carried over other paths as well.
This document describes how multiple paths can be used simultaneously
for transmitting user messages.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 2 September 2024.
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Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Load Sharing . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Split Fast Retransmissions . . . . . . . . . . . . . . . 4
3.2. Appropriate Congestion Window Growth . . . . . . . . . . 4
3.3. Appropriate Delayed Acknowledgements . . . . . . . . . . 5
4. Non-Renegable SACK . . . . . . . . . . . . . . . . . . . . . 5
4.1. Negotiation . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. The New Chunk Type: Non-Renegable SACK (NR-SACK) . . . . 6
4.3. An Illustrative Example . . . . . . . . . . . . . . . . . 11
4.4. Procedures . . . . . . . . . . . . . . . . . . . . . . . 14
4.4.1. Sending an NR-SACK chunk . . . . . . . . . . . . . . 14
4.4.2. Receiving an NR-SACK Chunk . . . . . . . . . . . . . 16
5. Buffer Blocking Mitigation . . . . . . . . . . . . . . . . . 17
5.1. Sender Buffer Splitting . . . . . . . . . . . . . . . . . 17
5.2. Receiver Buffer Splitting . . . . . . . . . . . . . . . . 17
5.3. Chunk Rescheduling . . . . . . . . . . . . . . . . . . . 17
5.4. Problems during Path Failure . . . . . . . . . . . . . . 17
5.4.1. Problem Description . . . . . . . . . . . . . . . . . 17
5.4.2. Solution: Potentially-failed Destination State . . . 18
5.5. Non-Renegable SACK . . . . . . . . . . . . . . . . . . . 18
5.5.1. Problem Description . . . . . . . . . . . . . . . . . 18
5.5.2. Solution: Non-Renegable SACKs . . . . . . . . . . . . 19
6. Handling of Shared Bottlenecks . . . . . . . . . . . . . . . 19
6.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 19
6.2. Initial Values . . . . . . . . . . . . . . . . . . . . . 20
6.3. Congestion Window Growth . . . . . . . . . . . . . . . . 20
6.4. Congestion Window Decrease . . . . . . . . . . . . . . . 20
7. Chunk Scheduling and Rescheduling . . . . . . . . . . . . . . 20
8. Socket API Considerations . . . . . . . . . . . . . . . . . . 20
9. Testbed Platforms . . . . . . . . . . . . . . . . . . . . . . 20
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
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10.1. A New Chunk Type . . . . . . . . . . . . . . . . . . . . 21
11. Security Considerations . . . . . . . . . . . . . . . . . . . 21
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
13.1. Normative References . . . . . . . . . . . . . . . . . . 21
13.2. Informative References . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction
One of the important features of the Stream Control Transmission
Protocol (SCTP), which is currently specified in [2], is network
fault tolerance. This feature is for example required for Reliable
Server Pooling (RSerPool, [4]). Therefore, transmitting messages
over multiple paths is supported, but only for redundancy. So [2]
does not specify how to use multiple paths simultaneously.
This document overcomes this limitation by specifying how multiple
paths can be used simultaneously. This has several benefits:
* Improved bandwidth usage.
* Better availability check with real user messages compared to
HEARTBEAT-based information.
2. Conventions
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 [1].
3. Load Sharing
Basic requirement for applying SCTP load sharing is the Concurrent
Multipath Transfer (CMT) extension of SCTP, which utilises multiple
paths simultaneously. We denote CMT-enabled SCTP as CMT-SCTP
throughout this document. CMT-SCTP is introduced in [10] and in more
detail in [9], some illustrative examples of chunk handling are
provided in [14]. CMT-SCTP provides three modifications to standard
SCTP (split Fast Retransmissions, appropriate congestion window
growth and delayed SACKs), which are described in the following
subsections.
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3.1. Split Fast Retransmissions
Paths with different latencies lead to overtaking of DATA chunks.
This leads to gap reports, which are handled by Fast Retransmissions.
However, due to the fact that multiple paths are used simultaneously,
these Fast Retransmissions are usually useless and furthermore lead
to a decreased congestion window size.
To avoid unnecessary Fast Retransmissions, the sender has to keep
track of the path each DATA chunk has been sent on and consider
transmission paths before performing Fast Retransmissions. That is,
on reception of a SACK, the sender MUST identify the highest
acknowledged TSN on each path. A chunk SHOULD only be considered as
missing if its TSN is smaller than the highest acknowledged TSN on
its path. Section 3.1 of [14] contains an illustrated example.
3.2. Appropriate Congestion Window Growth
The congestion window adaptation algorithm for SCTP [2] allows
increasing the congestion window only when a new cumulative ack
(CumAck) is received by a sender. When SACKs with unchanged CumAcks
are generated (due to reordering) and later arrive at a sender, the
sender does not modify its congestion window. Since a CMT-SCTP
receiver naturally observes reordering, many SACKs are sent
containing new gap reports but not new CumAcks. When these gaps are
later acked by a new CumAck, congestion window growth occurs, but
only for the data newly acked in the most recent SACK. Data
previously acked through gap reports will not contribute to
congestion window growth, in order to prevent sudden increases in the
congestion window resulting in bursts of data being sent.
To overcome the problems described above, the congestion window
growth has to be handled as follows [10]:
* The sender SHOULD keep track of the earliest non-retransmitted
outstanding TSN per path.
* The sender SHOULD keep track of the earliest retransmitted
outstanding TSN per path.
* The in-order delivery per path SHOULD be deduced.
* The congestion window of a path SHOULD be increased when the
earliest non-retransmitted outstanding TSN of this path is
advanced ('Pseudo CumAck') OR when the earliest retransmitted
outstanding TSN of this path is advanced ('RTX Pseudo CumAck').
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Section 3.2 of [14] contains an illustrated example of appropriate
congestion window handling for CMT-SCTP.
3.3. Appropriate Delayed Acknowledgements
Standard SCTP [2] sends a SACK as soon as an out-of-sequence TSN has
been received. Delayed Acknowledgements are only allowed if the
received TSNs are in sequence. However, due to the load balancing of
CMT-SCTP, DATA chunks may overtake each other. This leads to a high
number of out-of-sequence TSNs, which have to be acknowledged
immediately. Clearly, this behaviour increases the overhead traffic
(usually nearly one SACK chunk for each received packet containing a
DATA chunk).
Delayed Acknowledgements for CMT-SCTP are handled as follows:
* In addition to [2], delaying of SACKs SHOULD *also* be applied for
out-of-sequence TSNs.
* A receiver MUST maintain a counter for the number of DATA chunks
received before sending a SACK. The value of the counter is
stored into each SACK chunk (FIXME: add details; needs reservation
of flags bits by IANA). After transmitting a SACK, the counter
MUST be reset to 0. Its initial value MUST be 0.
* The SACK handling procedure for a missing TSN M is extended as
follows:
- If all newly acknowledged TSNs have been transmitted over the
same path:
o If there are newly acknowledged TSNs L and H so that L <= M
<= H, the missing count of TSN M SHOULD be incremented by
one (like for standard SCTP according to [2]).
o Else if all newly acknowledged TSNs N satisfy the condition
M <= N, the missing count of TSN M SHOULD be incremented by
the number of TSNs reported in the SACK chunk.
- Otherwise (that is, there are newly acknowledged TSNs on
different paths), the missing count of TSN M SHOULD be
incremented by one (like for standard SCTP according to [2]).
Section 3.3 of [14] contains an illustrated example of Delayed
Acknowledgements for CMT-SCTP.
4. Non-Renegable SACK
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4.1. Negotiation
Before sending/receiving NR-SACKs (see [16]), both peer endpoints
MUST agree on using NR-SACKs. This agreement MUST be negotiated
during association establishment. NR-SACK is an extension to the
core SCTP, and SCTP extensions that an endpoint supports are reported
to the peer endpoint in Supported Extensions Parameter during
association establishment (see Section 4.2.7 of [3].) The Supported
Extensions Parameter consists of a list of non-standard Chunk Types
that are supported by the sender.
An endpoint supporting the NR-SACK extension MUST list the NR-SACK
chunk in the Supported Extensions Parameter carried in the INIT or
INIT-ACK chunk, depending on whether the endpoint initiates or
responds to the initiation of the association. If the NR-SACK chunk
type ID is listed in the Chunk Types List of the Supported Extensions
Parameter, then the receiving endpoint MUST assume that the NR-SACK
chunk is supported by the sending endpoint.
Both endpoints MUST support NR-SACKs for either endpoint to send an
NR-SACK. If an endpoint establishes an association with a remote
endpoint that does not list NR-SACK in the Supported Extensions
Parameter carried in INIT chunk, then both endpoints of the
association MUST NOT use NR-SACKs. After association establishment,
an endpoint MUST NOT renegotiate the use of NR-SACKs.
Once both endpoints indicate during association establishment that
they support the NR-SACK extension, each endpoint SHOULD acknowledge
received DATA chunks with NR-SACK chunks, and not SACK chunks. That
is, throughout an SCTP association, both endpoints SHOULD send either
SACK chunks or NR-SACK chunks, never a mixture of the two.
4.2. The New Chunk Type: Non-Renegable SACK (NR-SACK)
Table 1 illustrates a new chunk type that will be used to transfer
NR-SACK information.
Chunk Type Chunk Name
--------------------------------------------------------------
0x10 Non-Renegable Selective Acknowledgment (NR-SACK)
Table 1: NR-SACK Chunk
As the NR-SACK chunk replaces the SACK chunk, many SACK chunk fields
are preserved in the NR-SACK chunk. These preserved fields have the
same semantics with the corresponding SACK chunk fields, as defined
in [2], Section 3.3.4. The Gap Ack fields from RFC4960 have been
renamed as R Gap Ack to emphasize their renegable nature. Their
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semantics are unchanged. For completeness, we describe all fields of
the NR-SACK chunk, including those that are identical in the SACK
chunk.
Similar to the SACK chunk, the NR-SACK chunk is sent to a peer
endpoint to (1) acknowledge DATA chunks received in-order, (2)
acknowledge DATA chunks received out-of-order, and (3) identify DATA
chunks received more than once (i.e., duplicate.) In addition, the
NR-SACK chunk (4) informs the peer endpoint of non-renegable out-of-
order DATA chunks.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type = 0x10 | Chunk Flags | Chunk Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cumulative TSN Ack |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Advertised Receiver Window Credit (a_rwnd) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Number of R Gap Ack Blocks = N |Number of NR Gap Ack Blocks = M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Number of Duplicate TSNs = X | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| R Gap Ack Block #1 Start | R Gap Ack Block #1 End |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ /
\ ... \
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| R Gap Ack Block #N Start | R Gap Ack Block #N End |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NR Gap Ack Block #1 Start | NR Gap Ack Block #1 End |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ /
\ ... \
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NR Gap Ack Block #M Start | NR Gap Ack Block #M End |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Duplicate TSN 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
/ /
\ ... \
/ /
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Duplicate TSN X |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Type: 8 bits
This field holds the IANA defined chunk type for NR-SACK chunk. The
suggested value of this field for IANA is 0x10.
Chunk Flags: 8 bits
Currently not used. It is recommended a sender set all bits to zero
on transmit, and a receiver ignore this field.
Chunk Length: 16 bits (unsigned integer) [Same as SACK chunk]
This value represents the size of the chunk in bytes including the
Chunk Type, Chunk Flags, Chunk Length, and Chunk Value fields.
Cumulative TSN Ack: 32 bits (unsigned integer) [Same as SACK chunk]
The value of the Cumulative TSN Ack is the last TSN received before a
break in the sequence of received TSNs occurs. The next TSN value
following the Cumulative TSN Ack has not yet been received at the
endpoint sending the NR-SACK.
Advertised Receiver Window Credit (a_rwnd): 32 bits (unsigned
integer) [Same as SACK chunk]
Indicates the updated receive buffer space in bytes of the sender of
this NR-SACK, see Section 6.2.1 of [2] for details.
Number of (R)enegable Gap Ack Blocks (N): 16 bits (unsigned integer)
Indicates the number of Renegable Gap Ack Blocks included in this NR-
SACK.
Number of (N)on(R)enegable Gap Ack Blocks (M): 16 bits (unsigned
integer)
Indicates the number of Non-Renegable Gap Ack Blocks included in this
NR-SACK.
Number of Duplicate TSNs (X): 16 bits [Same as SACK chunk]
Contains the number of duplicate TSNs the endpoint has received.
Each duplicate TSN is listed following the NR Gap Ack Block list.
Reserved : 16 bits
Currently not used. It is recommended a sender set all bits to zero
on transmit, and a receiver ignore this field.
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(R)enegable Gap Ack Blocks:
The NR-SACK contains zero or more R Gap Ack Blocks. Each R Gap Ack
Block acknowledges a subsequence of renegable out-of-order TSNs. By
definition, all TSNs acknowledged by R Gap Ack Blocks are "greater
than" the value of the Cumulative TSN Ack.
Because of TSN numbering wraparound, comparisons and all arithmetic
operations discussed in this document are based on "Serial Number
Arithmetic" as described in Section 1.6 of [2].
R Gap Ack Blocks are repeated for each R Gap Ack Block up to 'N'
defined in the Number of R Gap Ack Blocks field. All DATA chunks
with TSNs >= (Cumulative TSN Ack + R Gap Ack Block Start) and <=
(Cumulative TSN Ack + R Gap Ack Block End) of each R Gap Ack Block
are assumed to have been received correctly, and are renegable.
R Gap Ack Block Start: 16 bits (unsigned integer)
Indicates the Start offset TSN for this R Gap Ack Block. This number
is set relative to the cumulative TSN number defined in Cumulative
TSN Ack field. To calculate the actual start TSN number, the
Cumulative TSN Ack is added to this offset number. The calculated
TSN identifies the first TSN in this R Gap Ack Block that has been
received.
R Gap Ack Block End: 16 bits (unsigned integer)
Indicates the End offset TSN for this R Gap Ack Block. This number
is set relative to the cumulative TSN number defined in the
Cumulative TSN Ack field. To calculate the actual TSN number, the
Cumulative TSN Ack is added to this offset number. The calculated
TSN identifies the TSN of the last DATA chunk received in this R Gap
Ack Block.
N(on)R(enegable) Gap Ack Blocks:
The NR-SACK contains zero or more NR Gap Ack Blocks. Each NR Gap Ack
Block acknowledges a continuous subsequence of non-renegable out-of-
order DATA chunks. If a TSN is nr-gap-acked in any NR-SACK chunk,
then all subsequently transmitted NR-SACKs with a smaller cum-ack
value than that TSN SHOULD also nr-gap-ack that TSN.
NR Gap Ack Blocks are repeated for each NR Gap Ack Block up to 'M'
defined in the Number of NR Gap Ack Blocks field. All DATA chunks
with TSNs >= (Cumulative TSN Ack + NR Gap Ack Block Start) and <=
(Cumulative TSN Ack + NR Gap Ack Block End) of each NR Gap Ack Block
are assumed to be received correctly, and are Non-Renegable.
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NR Gap Ack Block Start: 16 bits (unsigned integer)
Indicates the Start offset TSN for this NR Gap Ack Block. This
number is set relative to the cumulative TSN number defined in
Cumulative TSN Ack field. To calculate the actual TSN number, the
Cumulative TSN Ack is added to this offset number. The calculated
TSN identifies the first TSN in this NR Gap Ack Block that has been
received.
NR Gap Ack Block End: 16 bits (unsigned integer)
Indicates the End offset TSN for this NR Gap Ack Block. This number
is set relative to the cumulative TSN number defined in Cumulative
TSN Ack field. To calculate the actual TSN number, the Cumulative
TSN Ack is added to this offset number. The calculated TSN
identifies the TSN of the last DATA chunk received in this NR Gap Ack
Block.
Note:
NR Gap Ack Blocks and R Gap Ack Blocks in an NR-SACK chunk SHOULD
acknowledge disjoint sets of TSNs. That is, an out-of-order TSN
SHOULD be listed in either an R Gap Ack Block or an NR Gap Ack Block,
but not the both. R Gap Ack Blocks and NR Gap Ack Blocks together
provide the information as do the Gap Ack Block of a SACK chunk, plus
additional information about non-renegability.
If all out-of-order data acked by an NR-SACK are renegable, then the
Number of NR Gap Ack Blocks MUST be set to 0. If all out-of-order
data acked by an NR-SACK are non-renegable, then the Number of R Gap
Ack Blocks SHOULD be set to 0. TSNs listed in R Gap Ack Block will
be referred as r-gap-acked.
Duplicate TSN: 32 bits (unsigned integer) [Same as SACK chunk]
Indicates a duplicate TSN received since the last NR-SACK was sent.
Exactly 'X' duplicate TSNs SHOULD be reported where 'X' was defined
in Number of Duplicate TSNs field.
Each duplicate TSN is listed in this field as many times as the TSN
was received since the previous NR-SACK was sent. For example, if a
data receiver were to get the TSN 19 three times, the data receiver
would list 19 twice in the outbound NR-SACK. After sending the NR-
SACK if the receiver received one more TSN 19, the receiver would
list 19 as a duplicate once in the next outgoing NR-SACK.
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4.3. An Illustrative Example
Assume the following DATA chunks have arrived at the receiver.
--------------------------------
| TSN=16| SID=2 | SSN=N/A| U=1 |
--------------------------------
| TSN=15| SID=1 | SSN= 4 | U=0 |
--------------------------------
| TSN=14| SID=0 | SSN= 4 | U=0 |
--------------------------------
| TSN=13| SID=2 | SSN=N/A| U=1 |
--------------------------------
| |
--------------------------------
| TSN=11| SID=0 | SSN= 3 | U=0 |
-------------------------------
| |
--------------------------------
| |
--------------------------------
| TSN=8 | SID=2 | SSN=N/A| U=1 |
--------------------------------
| TSN=7 | SID=1 | SSN= 2 | U=0 |
--------------------------------
| TSN=6 | SID=1 | SSN= 1 | U=0 |
--------------------------------
| TSN=5 | SID=0 | SSN= 1 | U=0 |
--------------------------------
| |
--------------------------------
| TSN=3 | SID=1 | SSN= 0 | U=0 |
--------------------------------
| TSN=2 | SID=0 | SSN= 0 | U=0 |
--------------------------------
The above figure shows the list of DATA chunks at the receiver. TSN
denotes the transmission sequence number of the DATA chunk, SID
denotes the stream id to which the DATA chunk belongs, SSN denotes
the sequence number of the DATA chunk within its stream, and the U
bit denotes whether the DATA chunk requires ordered(=0) or
unordered(=1) delivery [2]. Note that TSNs 4,9,10, and 12 have not
arrived.
This data can be viewed as three separate streams as follows (assume
each stream begins with SSN=0.) Note that in this example, the
application uses stream 2 for unordered data transfer. By
definition, SSN fields of unordered DATA chunks are ignored.
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Stream-0:
SSN: 0 1 2 3 4
TSN: | 2 | 5 | | 11 | 14 |
U-Bit: | 0 | 0 | | 0 | 0 |
Stream-1:
SSN: 0 1 2 3 4
TSN: | 3 | 6 | 7 | | 15 |
U-Bit: | 0 | 0 | 0 | | 0 |
Stream-2:
SSN: N/A N/A N/A
TSN: | 8 | 13 | 16 |
U-Bit: | 1 | 1 | 1 |
The NR-SACK to acknowledge the above data SHOULD be constructed as
follows for each of the three cases described below (the a_rwnd is
arbitrarily set to 4000):
CASE-1: Minimal Data Receiver Responsibility - no out-of-order
deliverable data yet delivered
None of the deliverable out-of-order DATA chunks have been delivered,
and the receiver of the above data does not take responsibility for
any of the received out-of-order DATA chunks. The receiver reserves
the right to renege any or all of the out-of-order DATA chunks.
+-----------------------------+-----------------------------+
| Type = 0x10 | 00000000 | Chunk Length = 32 |
+-----------------------------+-----------------------------+
| Cumulative TSN Ack = 3 |
+-----------------------------+-----------------------------+
| a_rwnd = 4000 |
+-----------------------------+-----------------------------+
| Num of R Gap Ack Blocks = 3 |Num of NR Gap Ack Blocks = 0 |
+-----------------------------+-----------------------------+
| Num of Duplicates = 0 | 0x00 |
+-----------------------------+-----------------------------+
|R Gap Ack Block #1 Start = 2 | R Gap Ack Block #1 End = 5 |
+-----------------------------+-----------------------------+
|R Gap Ack Block #2 Start = 8 | R Gap Ack Block #2 End = 8 |
+-----------------------------+-----------------------------+
|R Gap Ack Block #3 Start = 10| R Gap Ack Block #3 End = 13 |
+-----------------------------+-----------------------------+
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CASE-2: Minimal Data Receiver Responsibility - all out-of-order
deliverable data delivered
In this case, the NR-SACK chunk is being sent after the data receiver
has delivered all deliverable out-of-order DATA chunks to its
receiving application(i.e., TSNs 5,6,7,8,13, and 16.) The receiver
reserves the right to renege on all undelivered out-of-order DATA
chunks(i.e., TSNs 11,14, and 15.)
+------------------------------+------------------------------+
| Type = 0x10 | 0x00 | Chunk Length = 40 |
+------------------------------+------------------------------+
| Cumulative TSN Ack = 3 |
+------------------------------+------------------------------+
| a_rwnd = 4000 |
+------------------------------+------------------------------+
| Num of R Gap Ack Blocks = 2 | Num of NR Gap Ack Blocks = 3 |
+------------------------------+------------------------------+
| Num of Duplicates = 0 | 0x00 |
+------------------------------+------------------------------+
| R Gap Ack Block #1 Start = 8 | R Gap Ack Block #1 End = 8 |
+------------------------------+------------------------------+
| R Gap Ack Block #2 Start = 11| R Gap Ack Block #2 End = 12 |
+------------------------------+------------------------------+
|NR Gap Ack Block #1 Start = 2 | NR Gap Ack Block #1 End = 5 |
+------------------------------+------------------------------+
|NR Gap Ack Block #2 Start = 10| NR Gap Ack Block #2 End = 10 |
+------------------------------+------------------------------+
|NR Gap Ack Block #3 Start = 13| NR Gap Ack Block #3 End = 13 |
+------------------------------+------------------------------+
CASE-3: Maximal Data Receiver Responsibility
In this special case, all out-of-order data blocks acknowledged are
non-renegable. This case would occur when the data receiver is
programmed never to renege, and takes responsibility to deliver all
DATA chunks that arrive out-of-order. In this case Num of R Gap Ack
Blocks is zero indicating all reported out-of-order TSNs are nr-gap-
acked.
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+--------------------------------+-------------------------------+
| Type = 0x10 | 0x00 | Chunk Length = 32 |
+--------------------------------+-------------------------------+
| Cumulative TSN Ack = 3 |
+--------------------------------+-------------------------------+
| a_rwnd = 4000 |
+--------------------------------+-------------------------------+
| Num of R Gap Ack Blocks = 0 | Num of NR Gap Ack Blocks = 3 |
+--------------------------------+-------------------------------+
| Num of Duplicates = 0 | 0x00 |
+--------------------------------+-------------------------------+
| NR Gap Ack Block #1 Start = 2 | NR Gap Ack Block #1 End = 5 |
+--------------------------------+-------------------------------+
| NR Gap Ack Block #2 Start = 8 | NR Gap Ack Block #2 End = 8 |
+--------------------------------+-------------------------------+
| NR Gap Ack Block #3 Start = 10 | NR Gap Ack Block #3 End = 13 |
+--------------------------------+-------------------------------+
4.4. Procedures
The procedures regarding "when" to send an NR-SACK chunk are
identical to the procedures regarding when to send a SACK chunk, as
outlined in Section 6.2 of [2].
4.4.1. Sending an NR-SACK chunk
All of the NR-SACK chunk fields identical to the SACK chunk MUST be
formed as described in Section 6.2 of [2].
It is up to the data receiver whether or not to take responsibility
for delivery of each out-of-order DATA chunk. An out-of-order DATA
chunk that has already been delivered, or that the receiver takes
responsibility to deliver (i.e., guarantees not to renege) is Non
Renegable(NR), and SHOULD be included in an NR Gap Ack Block field of
the outgoing NR-SACK. All other out-of-order data is (R)enegable,
and SHOULD be included in R Gap Ack Block field of the outgoing NR-
SACK.
Consider three types of data receiver:
CASE-1: Data receiver takes no responsibility for delivery of any
out-of-order DATA chunks
CASE-2: Data receiver takes responsibility for all out-of-order DATA
chunks that are "deliverable" (i.e., DATA chunks in-sequence
within the stream they belong to, or DATA chunks whose (U)nordered
bit is 1)
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CASE-3: Data receiver takes responsibility for delivery of all out-
of-order DATA chunks, whether deliverable or not deliverable
The data receiver SHOULD follow the procedures outlined below for
building the NR-SACK.
CASE-1:
1A) Identify the TSNs received out-of-order.
1B) For these out-of-order TSNs, identify the R Gap Ack Blocks.
Fill the Number of R Gap Ack Blocks (N) field, R Gap Ack Block #i
Start, and R Gap Ack Block #i End where i goes from 1 to N.
1C) Set the Number of NR Gap Ack Blocks (M) field to 0.
CASE-2:
2A) Identify the TSNs received out-of-order.
2B) For the received out-of-order TSNs, check the (U)nordered bit of
each TSN. Tag unordered TSNs as NR.
2C) For each stream, also identify the TSNs received out-of-order
but are in-sequence within that stream. Tag those in-sequence
TSNs as NR.
2D) Tag all out-of-order data that is not NR as (R)enegable.
2E) For those TSNs tagged as (R)enegable, identify the (R)enegable
Blocks. Fill the Number of R Gap Ack Blocks(N) field, R Gap Ack
Block #i Start, and R Gap Ack Block #i End where i goes from 1 to
N.
2F) For those TSNs tagged as NR, identify the NR Blocks. Fill the
Number of NR Gap Ack Blocks(M) field, NR Gap Ack Block #i Start,
and NR Gap Ack Block #i End where i goes from 1 to M.
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CASE-3:
3A) Identify the TSNs received out-of-order. All of these TSNs
SHOULD be nr-gap-acked.
3B) Set the Number of R Gap Ack Blocks (N) field to 0.
3C) For these out-of-order TSNs, identify the NR Gap Ack Blocks.
Fill the Number of NR Gap Ack Blocks (M) field, NR Gap Ack Block
#i Start, and NR Gap Ack Block #i End where i goes from 1 to M.
RFC4960 states that the SCTP endpoint MUST report as many Gap Ack
Blocks as can fit in a single SACK chunk limited by the current path
MTU. When using NR-SACKs, the SCTP endpoint SHOULD fill as many R
Gap Ack Blocks and NR Gap Ack Blocks starting from the Cumulative TSN
Ack value as can fit in a single NR-SACK chunk limited by the current
path MTU. If space remains, the SCTP endpoint SHOULD fill as many
Duplicate TSNs as possible starting from Cumulative TSN Ack value.
4.4.2. Receiving an NR-SACK Chunk
When an NR-SACK chunk is received, all of the NR-SACK fields
identical to a SACK chunk SHOULD be processed and handled as in SACK
chunk handling outlined in Section 6.2.1 of [2].
The NR Gap Ack Block Start(s) and NR Gap Ack Block End(s) are offsets
relative to the cum-ack. To calculate the actual range of nr-gap-
acked TSNs, the cum-ack MUST be added to the Start and End.
For example, assume an incoming NR-SACK chunk's cum-ack is 12 and an
NR Gap Ack Block defines the NR Gap Ack Block Start=5, and the NR Gap
Ack Block End=7. This NR Gap Ack block nr-gap-acks TSNs 17 through
19 inclusive.
Upon reception of an NR-SACK chunk, all TSNs listed in either R Gap
Ack Block(s) or NR Gap Ack Block(s) SHOULD be processed as would be
TSNs included in Gap Ack Block(s) of a SACK chunk. All TSNs in all
NR Gap Ack Blocks SHOULD be removed from the data sender's
retransmission queue as their delivery to the receiving application
has either already occurred, or is guaranteed by the data receiver.
Although R Gap Ack Blocks and NR Gap Ack Blocks SHOULD be disjoint
sets, NR-SACK processing SHOULD work if an NR-SACK chunk has a TSN
listed in both an R Gap Ack Block and an NR Gap Ack Block. In this
case, the TSN SHOULD be treated as Non-Renegable.
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Implementation Note:
Most of NR-SACK processing at the data sender can be implemented by
using the same routines as in SACK that process the cum ack and the
gap ack(s), followed by removal of nr-gap-acked DATA chunks from the
retransmission queue. However, with NR-SACKs, as out-of-order DATA
is sometimes removed from the retransmission queue, the gap ack
processing routine should recognize that the data sender's
retransmission queue has some transmitted data removed. For example,
while calculating missing reports, the gap ack processing routine
cannot assume that the highest TSN transmitted is always at the tail
(right edge) of the retransmission queue.
5. Buffer Blocking Mitigation
TBD. See [23], [19], [18].
5.1. Sender Buffer Splitting
TBD. See [23], [19], [18].
5.2. Receiver Buffer Splitting
TBD. See [23], [19], [18].
5.3. Chunk Rescheduling
This algorithm ensures quick blocking resolution for ordered data.
TBD. See [23], [18].
5.4. Problems during Path Failure
This section discusses CMT's receive buffer related problems during
path failure, and proposes a solution for the same.
5.4.1. Problem Description
Link failures arise when a router or a link connecting two routers
fails due to link disconnection, hardware malfunction, or software
error. Overloaded links caused by flash crowds and denial-of-service
(DoS) attacks also degrade end-to-end communication between peer
hosts. Ideally, the routing system detects link failures, and in
response, reconfigures the routing tables and avoids routing traffic
via the failed link. However, existing research highlights problems
with Internet backbone routing that result in long route convergence
times. The pervasiveness of path failures motivated us to study
their impact on CMT, since CMT achieves better throughput via
simultaneous data transmission over multiple end-to-end paths.
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CMT is an extension to SCTP, and therefore retains SCTP's failure
detection process. A CMT sender uses a tunable failure detection
threshold called Path.Max.Retrans (PMR). When a sender experiences
more than PMR consecutive timeouts while trying to reach an active
destination, the destination is marked as failed. With PMR=5, the
failure detection takes 6 consecutive timeouts or 63s. After every
timeout, the CMT sender continues to transmit new data on the failed
path increasing the chances of receive buffer (rbuf) blocking and
degrading CMT performance during permanent and short-term path
failures [11].
5.4.2. Solution: Potentially-failed Destination State
To mitigate the rbuf blocking, we introduce a new destination state
called 'potentially-failed' state in SCTP (and CMT's) failure
detection process [6]. This solution is based on the rationale that
loss detected by a timeout implies either severe congestion or
failure en route. After a single timeout on a path, a sender is
unsure, and marks the corresponding destination as 'potentially-
failed' (PF). A PF destination is not used for data transmission or
retransmission. CMT's retransmission policies are augmented to
include the PF state. Performance evaluations prove that the PF
state significantly reduces rbuf blocking during failure detection
[11].
5.5. Non-Renegable SACK
This section discusses problems with SCTP's SACK mechanism and how it
affects the send buffer and CMT performance.
5.5.1. Problem Description
Gap-acks acknowledge DATA chunks that arrive out-of-order to a
transport layer data receiver. A gap-ack in SCTP is advisory, in
that, while it notifies a data sender about the reception of
indicated DATA chunks, the data receiver is permitted to later
discard DATA chunks that it previously had gap-acked. Discarding a
previously gap-acked DATA chunk is known as 'reneging'. Because of
the possibility of reneging in SCTP, any gap-acked DATA chunk MUST
NOT be removed from the data sender's retransmission queue until the
DATA chunk is later CumAcked.
Situations exist when a data receiver knows that reneging on a
particular out-of-order DATA chunk will never take place, such as
(but not limited to) after an out-of-order DATA chunk is delivered to
the receiving application. With current SACKs in SCTP, it is not
possible for a data receiver to inform a data sender if or when a
particular out-of-order 'deliverable' DATA chunk has been 'delivered'
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to the receiving application. Thus the data sender MUST keep a copy
of every gap-acked out-of-order DATA chunk(s) in the data sender's
retransmission queue until the DATA chunk is CumAcked. This use of
the data sender's retransmission queue is wasteful. The wasted
buffer often degrades CMT performance; the degradation increases when
a CMT flow traverses via paths with disparate end-to-end properties
[12].
5.5.2. Solution: Non-Renegable SACKs
Non-Renegable Selective Acknowledgments (NR-SACKs) Section 4 are a
new kind of acknowledgements, extending SCTP's SACK chunk
functionalities. The NR-SACK chunk is an extension of the existing
SACK chunk. Several fields are identical, including the Cumulative
TSN Ack, the Advertised Receiver Window Credit (a_rwnd), and
Duplicate TSNs. These fields have the same semantics as described in
[2].
NR-SACKs also identify out-of-order DATA chunks that a receiver
either: (1) has delivered to its receiving application, or (2) takes
full responsibility to eventually deliver to its receiving
application. These out-of-order DATA chunks are 'non-renegable.'
Non-Renegable data are reported in the NR Gap Ack Block field of the
NR-SACK chunk as described Section 4. We refer to non-renegable
selective acknowledgements as 'nr-gap-acks.'
When an out-of-order DATA chunk is nr-gap-acked, the data sender no
longer needs to keep that particular DATA chunk in its retransmission
queue, thus allowing the data sender to free up its buffer space
sooner than if the DATA chunk were only gap-acked. NR-SACKs improve
send buffer utilization and throughput for CMT flows [12].
6. Handling of Shared Bottlenecks
6.1. Introduction
CMT-SCTP assumes all paths to be disjoint. Since each path
independently uses a TCP-like congestion control, an SCTP association
using N paths over the same bottleneck acquires N times the bandwidth
of a concurrent TCP flow. This is clearly unfair. A reliable
detection of shared bottlenecks is impossible in arbitrary networks
like the Internet. Therefore, [21] [20], [15] apply the idea of
Resource Pooling to CMT-SCTP. Resource Pooling (RP) denotes 'making
a collection of resources behave like a single pooled resource' [13].
The modifications of RP-enabled CMT-SCTP, further denoted as CMT/RP-
SCTP, are described in the following subsections. A detailed
description of CMT/RP-SCTP, including congestion control examples,
can be found in [21], [20], [15].
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6.2. Initial Values
TDB.
6.3. Congestion Window Growth
TDB. See [23], [21], [20].
6.4. Congestion Window Decrease
TDB. See [23], [21], [20].
7. Chunk Scheduling and Rescheduling
TDB. See [23], [17].
8. Socket API Considerations
See [7] and [8].
9. Testbed Platforms
A large-scale and realistic Internet testbed platform with support
for the multi-homing feature of the underlying SCTP protocol is
NorNet. Particularly, it is also a platform for multi-path transport
experiments with CMT-SCTP. A description of and introduction to
NorNet is provided in [26], [25], [28], [29]. Further information
can be found on the project website [24] at https://www.nntb.no.
An Open Source simulation model of CMT-SCTP is available for OMNeT++
within the INET Framework. See [27] for the Git repository. For
documentation on the model, together with performance evaluations,
see [23]. Some interesting performance evaluations for delay-
sensitive traffic with CMT-SCTP can be found in [22].
10. IANA Considerations
NOTE to RFC-Editor:
"RFCXXXX" is to be replaced by the RFC number you assign this
document.
NOTE to RFC-Editor:
The suggested values for the chunk type and the chunk parameter
types are tentative and to be confirmed by IANA.
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This document (RFCXXXX) is the reference for all registrations
described in this section. The suggested changes are described
below.
10.1. A New Chunk Type
A chunk type has to be assigned by IANA. It is suggested to use the
values given in Section 4. IANA should assign this value from the
pool of chunks with the upper two bits set to '00'.
This requires an additional line in the "Chunk Types" registry for
SCTP:
Chunk Types
ID Value Chunk Type Reference
----- ---------- ---------
16 Non-Renegable SACK (NR-SACK) [RFCXXXX]
The registration table as defined in [5] for the chunk flags of this
chunk type is empty.
11. Security Considerations
This document does not add any additional security considerations in
addition to the ones given in [2].
12. Acknowledgments
The authors wish to thank Paul D. Amer, Hakim Adhari, Phillip
Conrad, Jonathan Leighton, Ertugrul Yilmaz and Xing Zhou for their
invaluable comments and support.
13. References
13.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[2] Stewart, R., Ed., "Stream Control Transmission Protocol",
RFC 4960, DOI 10.17487/RFC4960, September 2007,
<https://www.rfc-editor.org/info/rfc4960>.
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[3] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061,
DOI 10.17487/RFC5061, September 2007,
<https://www.rfc-editor.org/info/rfc5061>.
[4] Lei, P., Ong, L., Tuexen, M., and T. Dreibholz, "An
Overview of Reliable Server Pooling Protocols", RFC 5351,
DOI 10.17487/RFC5351, September 2008,
<https://www.rfc-editor.org/info/rfc5351>.
[5] Tuexen, M. and R. Stewart, "Stream Control Transmission
Protocol (SCTP) Chunk Flags Registration", RFC 6096,
DOI 10.17487/RFC6096, January 2011,
<https://www.rfc-editor.org/info/rfc6096>.
[6] Nishida, Y., Natarajan, P., Caro, A., Amer, P. D., and K.
E. E. Nielsen, "SCTP-PF: A Quick Failover Algorithm for
the Stream Control Transmission Protocol", Work in
Progress, Internet-Draft, draft-ietf-tsvwg-sctp-failover-
16, 17 February 2016, <https://www.ietf.org/archive/id/
draft-ietf-tsvwg-sctp-failover-16.txt>.
[7] Dreibholz, T., Becke, M., and H. Adhari, "SCTP Socket API
Extensions for Concurrent Multipath Transfer", Work in
Progress, Internet-Draft, draft-dreibholz-tsvwg-
sctpsocket-multipath-23, 6 September 2021,
<https://www.ietf.org/archive/id/draft-dreibholz-tsvwg-
sctpsocket-multipath-23.txt>.
[8] Dreibholz, T., Seggelmann, R., and M. Becke, "Sender Queue
Info Option for the SCTP Socket API", Work in Progress,
Internet-Draft, draft-dreibholz-tsvwg-sctpsocket-sqinfo-
24, 21 March 2022, <https://www.ietf.org/archive/id/draft-
dreibholz-tsvwg-sctpsocket-sqinfo-24.txt>.
13.2. Informative References
[9] Iyengar, J., "End-to-End Concurrent Multipath Transfer
Using Transport Layer Multihoming", PhD
Dissertation Computer Science Dept., University of
Delaware, April 2006,
<https://www.eecis.udel.edu/~amer/PEL/poc/pdf/
IyengarPhDdissertation.pdf>.
[10] Iyengar, J., Amer, P. D., and R. R. Stewart, "Concurrent
Multipath Transfer Using SCTP Multihoming Over Independent
End-to-End Paths", Journal IEEE/ACM Transactions on
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Networking, October 2006,
<https://www.eecis.udel.edu/~amer/PEL/poc/pdf/ToN2006-CMT-
over-Independent-Paths-Iyengar.pdf>.
[11] Natarajan, P., Ekiz, N., Iyengar, J., Amer, P., and R.
Stewart, "Concurrent Multipath Transfer Using Transport
Layer Multihoming: Introducing the Potentially-failed
Destination State", Proceedings of the IFIP Networking,
May 2008,
<http://dl.ifip.org/db/conf/networking/networking2008/
NatarajanEAIS08.pdf>.
[12] Natarajan, P., Ekiz, N., Yilmaz, E., Amer, P., Iyengar,
J., and R. Stewart, "Non-Renegable Selective
Acknowledgments (NR-SACKs) for SCTP", Proceedings of the
16th IEEE International Conference on Network Protocols
(ICNP) , October 2008,
<http://www.ieee-icnp.org/2008/papers/Index19.pdf>.
[13] Wischik, D., Handley, M., and M. B. Braun, "The Resource
Pooling Principle", Journal ACM SIGCOMM Computer
Communication Review, October 2009,
<http://haig.cs.ucl.ac.uk/staff/M.Handley/papers/respool-
ccr.pdf>.
[14] Dreibholz, T., Becke, M., Pulinthanath, J., and E. P.
Rathgeb, "Implementation and Evaluation of Concurrent
Multipath Transfer for SCTP in the INET Framework",
Proceedings of the 3rd ACM/ICST International Workshop on
OMNeT++ ISBN 978-963-9799-87-5,
DOI 10.4108/ICST.SIMUTOOLS2010.8673, 19 March 2010,
<https://www.wiwi.uni-due.de/fileadmin/fileupload/I-
TDR/SCTP/Paper/OMNeT__Workshop2010-SCTP.pdf>.
[15] Dreibholz, T., Becke, M., Pulinthanath, J., and E. P.
Rathgeb, "Applying TCP-Friendly Congestion Control to
Concurrent Multipath Transfer", Proceedings of the 24th
IEEE International Conference on Advanced Information
Networking and Applications (AINA) Pages 312-319,
ISBN 978-0-7695-4018-4, DOI 10.1109/AINA.2010.117, 21
April 2010, <https://www.wiwi.uni-
due.de/fileadmin/fileupload/I-TDR/SCTP/Paper/
AINA2010.pdf>.
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[16] Yilmaz, E., Ekiz, N., Natarajan, P., Amer, P., Leighton,
J., Baker, F., and R. Stewart, "Throughput Analysis of
Non-Renegable Selective Acknowledgments (NR-SACKs) for
SCTP", Computer
Communications, doi:10.1016/j.comcom.2010.06.028, 2010.
[17] Dreibholz, T., Seggelmann, R., Tüxen, M., and E. P.
Rathgeb, "Transmission Scheduling Optimizations for
Concurrent Multipath Transfer", Proceedings of the 8th
International Workshop on Protocols for Future, Large-
Scale and Diverse Network Transports (PFLDNeT) Volume 8,
ISSN 2074-5168, 29 November 2010, <https://www.wiwi.uni-
due.de/fileadmin/fileupload/I-TDR/SCTP/Paper/
PFLDNeT2010.pdf>.
[18] Dreibholz, T., Becke, M., Rathgeb, E. P., and M. Tüxen,
"On the Use of Concurrent Multipath Transfer over
Asymmetric Paths", Proceedings of the IEEE Global
Communications
Conference (GLOBECOM) ISBN 978-1-4244-5637-6,
DOI 10.1109/GLOCOM.2010.5683579, 7 December 2010,
<https://www.wiwi.uni-due.de/fileadmin/fileupload/I-
TDR/SCTP/Paper/Globecom2010.pdf>.
[19] Adhari, H., Dreibholz, T., Becke, M., Rathgeb, E. P., and
M. Tüxen, "Evaluation of Concurrent Multipath Transfer
over Dissimilar Paths", Proceedings of the 1st
International Workshop on Protocols and Applications with
Multi-Homing Support (PAMS) Pages 708-714,
ISBN 978-0-7695-4338-3, DOI 10.1109/WAINA.2011.92, 22
March 2011, <https://www.wiwi.uni-
due.de/fileadmin/fileupload/I-TDR/SCTP/Paper/
PAMS2011.pdf>.
[20] Dreibholz, T., Becke, M., Adhari, H., and E. P. Rathgeb,
"On the Impact of Congestion Control for Concurrent
Multipath Transfer on the Transport Layer", Proceedings of
the 11th IEEE International Conference on
Telecommunications (ConTEL) Pages 397-404,
ISBN 978-953-184-152-8, 16 June 2011,
<https://www.wiwi.uni-due.de/fileadmin/fileupload/I-
TDR/SCTP/Paper/ConTEL2011.pdf>.
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[21] Becke, M., Dreibholz, T., Adhari, H., and E. P. Rathgeb,
"On the Fairness of Transport Protocols in a Multi-Path
Environment", Proceedings of the IEEE International
Conference on Communications (ICC) Pages 2666-2672,
ISBN 978-1-4577-2052-9, DOI 10.1109/ICC.2012.6363695, 12
June 2012, <https://www.wiwi.uni-
due.de/fileadmin/fileupload/I-TDR/SCTP/Paper/ICC2012.pdf>.
[22] Yedugundla, K. V., Ferlin, S., Dreibholz, T., Alay, Ö.,
Kuhn, N., Hurtig, P., and A. Brunström, "Is Multi-Path
Transport Suitable for Latency Sensitive Traffic?",
Computer Networks Volume 105, Pages 1-21, ISSN 1389-1286,
DOI 10.1016/j.comnet.2016.05.008, 4 August 2016,
<https://www.simula.no/file/comnets2016-
multipathsurveypdf/download>.
[23] Dreibholz, T., "Evaluation and Optimisation of Multi-Path
Transport using the Stream Control Transmission
Protocol", Habilitation Treatise, 13 March 2012,
<https://duepublico.uni-duisburg-
essen.de/servlets/DerivateServlet/Derivate-29737/
Dre2012_final.pdf>.
[24] Dreibholz, T., "NorNet -- A Real-World, Large-Scale Multi-
Homing Testbed", Online: https://www.nntb.no/, 2022,
<https://www.nntb.no/>.
[25] Dreibholz, T. and E. G. Gran, "Design and Implementation
of the NorNet Core Research Testbed for Multi-Homed
Systems", Proceedings of the 3nd International Workshop on
Protocols and Applications with Multi-Homing
Support (PAMS) Pages 1094-1100, ISBN 978-0-7695-4952-1,
DOI 10.1109/WAINA.2013.71, 27 March 2013,
<https://www.simula.no/file/
threfereedinproceedingsreference2012-12-207643198512pdf/
download>.
[26] Gran, E. G., Dreibholz, T., and A. Kvalbein, "NorNet Core
– A Multi-Homed Research Testbed", Computer Networks,
Special Issue on Future Internet Testbeds Volume 61, Pages
75-87, ISSN 1389-1286, DOI 10.1016/j.bjp.2013.12.035, 14
March 2014,
<https://www.simula.no/file/simulasimula2236pdf/download>.
[27] Hornig, R. and A. Varga, "INET Framework Git Repository",
Online: https://github.com/inet-framework/inet, 2016,
<https://github.com/inet-framework/inet>.
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[28] Dreibholz, T., "An Introduction to Multi-Path Transport at
Hainan University", Keynote Talk at Hainan University,
College of Information Science and Technology (CIST), 14
December 2017, <https://www.simula.no/file/haikou2017-
multipath-presentationpdf-0/download>.
[29] Dreibholz, T., "NorNet Core Beginner Tutorial at Hainan
University", Tutorial at Hainan University, College of
Information Science and Technology (CIST), 15 December
2017, <https://www.simula.no/file/haikou2017-nornet-
tutorialpdf-0/download>.
Authors' Addresses
Martin Becke
HAW Hamburg, Informatics Department
Berliner Tor 7
20099 Hamburg
Germany
Phone: +49-40-42875-8104
Email: martin.becke@haw-hamburg.de
URI: http://www.scimbe.de/about.html
Thomas Dreibholz
Simula Metropolitan Centre for Digital Engineering
Pilestredet 52
0167 Oslo
Norway
Email: dreibh@simula.no
URI: https://www.simula.no/people/dreibh
Nasif Ekiz
University of Delaware, Computer and Information Sciences Department
Newark, Delaware 19716
United States of America
Email: nekiz@udel.edu
Janardhan R. Iyengar
Franklin and Marshall College, Mathematics and Computer Science
PO Box 3003
Lancaster, Pennsylvania 17604-3003
United States of America
Phone: +1-717-358-4774
Email: jiyengar@fandm.edu
Becke, et al. Expires 2 September 2024 [Page 26]
Internet-Draft Load Sharing for SCTP March 2024
Preethi Natarajan
Cisco Systems
425 East Tasman Drive
San Jose, California 95134
United States of America
Email: prenatar@cisco.com
Randall R. Stewart
Netflix
Chapin, South Carolina 29036
United States of America
Email: randall@lakerest.net
Michael Tüxen
Münster University of Applied Sciences
Stegerwaldstrasse 39
48565 Steinfurt
Germany
Email: tuexen@fh-muenster.de
URI: https://www.fh-muenster.de/fb2/personen/professoren/tuexen/
Becke, et al. Expires 2 September 2024 [Page 27]
