Internet Engineering Task Force A. Ford, Ed.
Internet-Draft Roke Manor Research
Intended status: Experimental C. Raiciu
Expires: April 22, 2010 University College London
S. Barre
Universite catholique de
Louvain
J. Iyengar
Franklin and Marshall College
B. Ford
Max Planck Institute for Software
Systems
October 19, 2009
Architectural Guidelines for Multipath TCP Development
draft-ford-mptcp-architecture-00
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Abstract
Often endpoints are connected by multiple paths, but the nature of
TCP/IP restricts communications to a single path per socket.
Resource usage within the network would be more efficient were these
multiple paths able to be used concurrently. This should enhance
user experience through higher throughput and improved resilience to
network failure.
This document outlines architectural guidelines for the development
of a Multipath Transport Protocol, with references to how these
architectural components come together in the Multipath TCP (MPTCP)
protocol. This document also contains suggestions for functional
separation within an implementation, maximising the flexibility that
can be achieved with these architectural components.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Goals . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1.1. Functional Goals . . . . . . . . . . . . . . . . . . . 4
1.1.2. Performance/Efficiency Goals . . . . . . . . . . . . . 5
1.2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 5
1.3. Requirements Language . . . . . . . . . . . . . . . . . . 6
2. Fundamentals . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
2.2. Reference Scenario . . . . . . . . . . . . . . . . . . . . 7
2.3. Layered Representation . . . . . . . . . . . . . . . . . . 7
3. Multipath Architecture . . . . . . . . . . . . . . . . . . . . 8
3.1. Motivations . . . . . . . . . . . . . . . . . . . . . . . 8
3.2. Decomposing Transport Functions . . . . . . . . . . . . . 8
3.3. TCP Performance . . . . . . . . . . . . . . . . . . . . . 10
4. Implementation Architecture . . . . . . . . . . . . . . . . . 11
4.1. Functional Separation . . . . . . . . . . . . . . . . . . 11
4.1.1. Application to default MPTCP protocol . . . . . . . . 11
4.1.2. Generic architecture for MPCTP . . . . . . . . . . . . 14
4.2. PM/MPS interface . . . . . . . . . . . . . . . . . . . . . 15
5. Security Considerations . . . . . . . . . . . . . . . . . . . 16
6. Interactions with Applications . . . . . . . . . . . . . . . . 16
7. Interactions with Middleboxes . . . . . . . . . . . . . . . . 17
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
10.1. Normative References . . . . . . . . . . . . . . . . . . . 17
10.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
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1. Introduction
Multipath TCP (MPTCP) will provide a set of extensions for regular
TCP [2] to allow one TCP connection to be spread across multiple
paths. This section describes the motivation behind the design of
Multipath TCP.
Companion documents to this architectural overview are those which
provide details of the protocol extensions, congestion control
algorithms, and application-level considerations. Put together,
these components build a complete Multipath TCP implementation.
Other components, however, could be introduced in place of these, in
accordance with the architecture specified in this document.
Please note this document is a work-in-progress and covers several
topics, some of which may be more appropriately moved to separate
documents as this work evolves.
1.1. Goals
This section outlines what we perceive to be the most important goals
for a multipath-capable transport protocol. We divide these goals
into two categories: functional goals and performance/efficiency
goals.
1.1.1. Functional Goals
o Multihoming: The multipath transport protocol must allow for a
logical transport endpoint as seen by the application to
correspond to multiple physical network attachment points, such as
multiple IP addresses on the same or different network interfaces.
o Application Compatibility: Multipath-capable equivalents of
existing transports such as concurrent multipath versions of TCP,
SCTP, or DCCP, must retain backward compatibility with existing
APIs, so that existing applications can use the newer transports,
merely by upgrading the operating systems of the end-hosts.
o Network Compatibility: Multipath transport protocols must remain
backward compatible with the Internet as it exists today,
including being able to traverse predominant existing middleboxes
such as firewalls, NATs, and performance enhancing proxies [3].
o Automatic Negotiation: A host supporting a multipath-capable
equivalent of an existing transport must be able to detect
reliably whether a new communication partner supports the next-
generation protocol, using it if so, and otherwise automatically
falling back to the existing protocol (e.g., standard TCP, SCTP,
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or DCCP).
o End-to-End Reliability and Security: The multipath-capable
equivalent of an existing transport must retain its end-to-end
reliability properties and allow for end-to-end authentication
and/or privacy protection in a network-compatible fashion, i.e.,
maintain compatibility with legacy middleboxes.
1.1.2. Performance/Efficiency Goals
o Multihoming and Multipath Capable: The protocol mustbe able to
detect and utilize multiple available paths between two logical
endpoints, either one path at a time (fail-over multipath) or
several at once (concurrent multipath).
o Resource Pooling: Transports should be able to balance traffic
among available paths, optimizing network utility in a global
sense by shifting load away from congested bottlenecks and taking
advantage of spare capacity wherever it may be located [4].
o TCP-Friendliness: The architecture must enable new multipath
transport flows to coexist gracefully with predominant existing
transport flows, competing for bandwidth neither unduly
aggressively or unduly timidly (unless low-precedence operation is
specifically requested by the application, such as with LEDBAT).
o Congestion State Sharing: Since popular applications such as HTTP
often use multiple transport instances between the same pair of
hosts, the protocol must avoid multiplicative explosions in
multipath congestion control contexts - i.e., N transport
instances times M multipath flows each - by enabling a multipath
"bundle" of congestion control contexts to be shared cleanly among
application-visible transport instances.
o Support Small Transactions: Recognizing that many applications
today make heavy use of frequent small communications, such as
HTTP conditional GET transactions or streaming media frames, next-
generation transports should minimize the performance costs of
supporting these common application behaviors, including by
minimizing unnecessary protocol overhead on small packets and by
unnecessary round-trip delays or state maintenance costs when
applications use short transactions.
1.2. Motivation
As the Internet evolves, demands on Internet resources are ever-
increasing, but often these resources (in particular, bandwidth)
cannot be fully utilised due to protocol constraints on both the end-
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systems and within the network. These unused resources, if they
could be used, would lead to an enhanced user experience. This would
also reduce the necessary expenditure on network infrastructure which
would otherwise be needed to create an equivalent experience
improvement.
By the application of resource pooling [4], these available resources
can be 'pooled' such that they appear as a single logical resource to
the user. The purpose of Multipath TCP, therefore, is to provide a
TCP to the user that is able to make use of multiple available paths.
The achievement of resource pooling through Multipath TCP bring two
key benefits:
o To increase the resilience of the connectivity by providing
multiple paths, protecting end hosts from the failure of one.
o To increase the efficiency of the resource usage, and thus
increase the network capacity available to end hosts.
A Multipath TCP MUST follow the same service model as TCP [2]: byte
oriented, in order reliable delivery. To have a deployable protocol,
MPTCP SHOULD adhere to the following "do no harm" philosophy:
multipath TCP SHOULD behave no worse (throughput wise) than running a
single TCP connection over any of its paths, and using multiple paths
MUST not harm users using single path TCP at shared bottlenecks. In
addition, it should aim to be backwards-compatible where possible
with existing, regular TCP.
Multipath TCP as presented in [5] follows these aims, and achieves
resource pooling by combining multiple TCP sessions running over
multiple paths, and presenting them as a single TCP connection to the
application. This is not the only way of creating a Multipath TCP,
however, and as such this architecture is designed so that other
components can be used in place
1.3. Requirements Language
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 RFC 2119 [1].
2. Fundamentals
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2.1. Terminology
Path: A sequence of links between a sender and a receiver, defined
in this context by a source and destination address pair.
Endpoint: A host operating an MPTCP implementation, and either
initiating or terminating a MPTCP connection.
Subflow: A flow of TCP packets operating over an individual path,
which forms part of a larger MPTCP connection.
Multipath TCP (MPTCP): A modified version of the TCP [2] protocol
that supports the simultaneous use of multiple paths between
endpoints.
2.2. Reference Scenario
TBD?
Endpoints, routes. Addresses/path selection mechanisms?
2.3. Layered Representation
A Multipath TCP operates at the transport layer, and its existence
should be transparent to both higher and lower layers. It is a set
of additional features on top of standard TCP, and as such the impact
on applications should be minimal, or entirely transparent, and these
application considerations are discussed in detail in [6].
Multipath-aware applications would be able to use an extended sockets
API to have further influence on the behaviour of MPTCP, which is
also specified in [6]. Figure 1 illustrates this architecture.
+-------------------------------+
| Application |
+---------------+ +-------------------------------+
| Application | | MPTCP |
+---------------+ + - - - - - - - + - - - - - - - +
| TCP | | Subflow (TCP) | Subflow (TCP) |
+---------------+ +-------------------------------+
| IP | | IP | IP |
+---------------+ +-------------------------------+
Figure 1: Comparison of Standard TCP and MPTCP Protocol Stacks
This layered model could apply to any multipath transport protocol,
with any multipath, transport and network layers. This is explored
in more detail in Section 3.2.
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This document now proceeds with a detailed discussion of an
architecture for developing a multipath TCP implementation,
especially regarding the functional separation by which different
components should be developed, in Section 3.
3. Multipath Architecture
This section describes the layered functional separation that drives
the design of the MPTCP protocol. Its main goal is to separate MPTCP
in two parts that communicate through a well defined interface. We
first provide the motivations for this functional separation, then we
describe in more details the two main components of the MPTCP
architecture.
3.1. Motivations
The major goal behind MPTCP is to send data over different paths in
the same time. This assumes that an MPTCP implementation must be
able to discover and use the multiple paths that connect two given
hosts, when they exist. However, different mechanisms can be
envisioned for multipath discovery and use. Examples are as follows:
Use multiple addresses: This is the method currently proposed in the
MPTCP protocol design [5] - if hosts are multi-addressed,
different address pairs may take different routes.
Use a path selector value: An end-host might be able to tag packets
with a path selector value, or adjust existing packet metadata.
If some network nodes are able to read this tag and use it as a
path selector, the host can influence the outgoing path of the
packet.
Next-hop selection: In a network configuration where multiple next-
hops can offer to forward packets, a host may decide to send some
of its packets through one next-hop, and some through another.
The above list is not exhaustive, and could grow as new network
technologies are deployed.
3.2. Decomposing Transport Functions
As shown in Figure 2, we first loosely separate functions within
transports into "application-oriented" and "network-oriented" parts.
We use this separation of functions as an architectural framework
that a multipath transport must recognize, primarily to maintain
backward compatibility with applications and with the network. The
desire for network compatibility will impact design choices at the
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subflow level, while the need for application compatibility will
primarily impact design choices at the higher, application-facing
MPTCP layer.
The top application-oriented "Semantic" functions are whatever
communication abstractions are to be made available to applications,
including providing the end-to-end reliability and ordering
properties of abstractions like TCP's byte streams or SCTP's message-
based multi-streams; these functions essentially deal with concerns
of application-visible semantics.
We consider the bottom part "network-oriented" because they represent
functions that, while traditionally located in the ostensibly "end-
to-end" Transport Layer, have proven in practice to be of great
concern to network operators and the middleboxes they deploy in the
network to enforce network usage policies [7][8] or optimize
communication performance [9]. The network-oriented functions
include congestion control and other performance-management functions
("Flow" performance functions), and endpoint/service identification
functions (e.g., port numbers) that network operators and their
middleboxes require to enforce network access and security policies
("Endpoint" functions). These network-oriented transport functions
are collectively labeled in figure Figure 2 as "Flow/Endpoint"
functions.
+-----------------+
| Application |
+---------------+ ---> +-----------------+
| Application | / | Semantic | (Application-Oriented
+---------------+ <-- | Functions | Functions)
| Transport | |- - - - - -|
+---------------+ <-- | Flow / Endpoint | (Network-Oriented
| Network | \ | Functions | Functions)
+---------------+ ---> +-----------------+
| Network |
+-----------------+
Figure 2: Decomposition of Transport Functions
Following from the discussion above, a multipath transport would have
to manage Flow/Endpoint functions for every path in an end-to-end
connection, while providing a transparent single interface to the
application. In keeping with this architectural worldview, MPTCP
divides the Transport Layer into two components: the MPTCP part,
which is responsible for the Semantic functions of global ordering of
application data and reliability; and the "legacy TCP" part, which
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implements the Flow/Endpoint functions. The figure below shows how
MPTCP implements this architecture:
+--------------------------+ +-------------------------+
| Application | | Application |
+--------------------------+ +-------------------------+
| Semantic | | MPTCP |
|- - - - - - - - - | + - - - - - + - - - - - +
| Flow/Endpt | Flow/Endpt | | TCP | TCP |
+--------------------------+ +-------------------------+
| Network | Network | | IP | IP |
+--------------------------+ +-------------------------+
Figure 3: Mapping Transport Architecture to MPTCP
3.3. TCP Performance
To provide multipath transport, Multipath TCP must send data over
multiple paths. A naive implementation could simply run a standard,
unmodified TCP congestion control algorithm [10] on each subflow. As
listed in Section 1.1.1, however, it is a goal that MPTCP does not
cause harm to other TCP flows, and such a naive approach would lead
to a multipath session taking a disproportionate amount of bandwidth
at shared bottlenecks.
Therefore, in addition to purely sending data over multiple paths,
MPTCP must do it in a way that will not affect TCP performance of
non-multipath users. This raises the need for an efficient multipath
congestion control algorithm. While this specification does not
mandate the use of any particular algorithm for congestion control,
it ensures that the protocol is designed in such a way that any
congestion control algorithm can be designed, independently of the
other components in use in the MPTCP implementation. Consequently,
our architecture for MPTCP decouples the policy from the mechanism.
The policy is the decision of what path to use for each packet to
send. It is mainly driven by the implementation-dependent congestion
control algorithm. The mechanism is the technology used to ensure
that a packet will be sent on the desired path. This separation is
intended to be relatively future-proof by allowing these components
to evolve at different speeds.
The decomposition of the transport functions, as described in
Section 3.2, places the congestion control functionality in the flow/
endpoint layer, which maps to an individual subflow in the MPTCP
design. In order to meet the "do-no-harm" philosophy, however, there
must be an interface to the congestion control implementation that
permits the appropriate coupling of congestion windows at the upper
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(MPTCP) layer.
4. Implementation Architecture
This section provides suggestions for an architecture to implement an
extensible, modular multipath transport protocol.
4.1. Functional Separation
This section describes a generic view of the internal implementation
of a Multipath TCP, through which the technical components specified
in the companion documents can fit together. It shows how an
implementation could be built that permits extensibility between
components without changing the external representation.
We first show the functional decomposition of an MPTCP solution that
is completely contained in the transport layer. That solution is
described in more details in [5]. Then we generalize the approach to
allow good extensibility of that solution.
4.1.1. Application to default MPTCP protocol
Although, in the default approach, MPTCP is fully contained in the
transport layer, it can still be divided into two main modules. One
manages the scheduling of packets as well as congestion control. The
other one manages the control of paths. The interface between the
two is dealt with thanks to a Path Index. As shown in Figure 4, the
Path Manager announces to the MultiPath Scheduler what paths can be
used trough path indices, and maintains the mapping between that
value and the particular action that it must apply to use the path
(an example of such a mapping is in Table 1). In the case of the
built-in Path Manager, the action is to replace an address/port pair
with another one, in such a way that another path is used across the
Internet to forward that packet.
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Control plane <-- | --> Data plane
+---------------------------------------------------------------+
| Multipath Scheduler (MPS) |
+---------------------------------------------------------------+
^ | |
| | [A1,B1,|pA1,pB1]
|For conn_id | |
|<A1,B1,pA1,pB1> | +-------------+
|Paths 1->4 can be | | Data packet |<--Path idx:3
|used. | +-------------+ attached
| | | by MPS
| | V
+--------------------------------------------\------------------+
| Path Manager (PM) \[A1,B1]->[A1,B2] |
+--------------------------------------------------\------------+
/ \ | \
/-----------------------------\ | /"\ /"\ /"\ /"\
| rewriting table: || | | | | | | | |
| Subflow id <--> network_id || | | | | | | | |
| || | | | | | | | |
| [see table below] || | | | | | | | |
| || \./ \./ \./ \./
+------------------------------+| path1 path2 path3 path4
Figure 4: Functional separation of MPTCP in the transport layer
The MultiPath Scheduler only deals with abstract paths, represented
by numbers. It only sees one address pair throughout the
communication, that we call the connection identifier. However, the
MultiPath Scheduler must be able to perform per-subflow congestion
control, and thus to distinguish between the subflows. This leads to
define a subflow identifier, that consists of the usual transport
identifier extended with the path index:
<addr_src,psrc,addr_dst,pdst,path_index>. The following options,
described in [5], are managed by the MultiPath Scheduler.
o MULTIPATH CAPABLE (MPC): Tell the peer that we support MPTCP.
Note that the MPC option also holds a token, which is necessary
only if the built-in Path Manager is used. In the next section we
describe the generalized case, where the token can be ignored by
the receiver if another path manager is used.
o DATA SEQUENCE NUMBER (DSN): Identify the position of a set of
bytes in the meta-flow.
o DATA FIN (DFIN): Terminate a meta-flow.
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An implementation MUST use those options even if another Path Manager
than the default one is implemented.
The Path manager applies a particular technology to give the MPS the
possibility to use several paths. The built-in MPTCP Path Manager
uses multiple IPv4 addresses as its mean to influence the forwarding
of packets through the Internet.
When the MPS starts a new connection, the PM chooses a token that
will be used to identify the connection. This is necessary to allow
the PM applying the correct path index to incoming packets. An
example mapping table is given hereafter:
+-----------------+------------------+---------+-----------------+
| connection id | subflow id | token | Network id |
+-----------------+------------------+---------+-----------------+
| <A1,B1,pA1,pB1> | <conn_id,pi1> | token_1 | <A1,B1,pA1,pB1> |
| <A1,B1,pA1,pB1> | <conn_id,pi2> | token_1 | <A2,B2,pA1,pB2> |
| <A1,B1,pA1,pB1> | <conn_id,pi3> | token_1 | <A1,B2,pA1,pB2> |
| <A1,B1,pA1,pB1> | <conn_id,pi4> | token_1 | <A2,B1,pA1,pB1> |
| <A1,B1,pA1,pB3> | <connect_id,pi1> | token_2 | <A1,B1,pA1,pB3> |
| <A1,B1,pA1,pB3> | <connect_id,pi2> | token_2 | <A2,B1,pA1,pB3> |
+-----------------+------------------+---------+-----------------+
Table 1: Example mapping table for built-in PM
Table 1 shows an example where two connections are ongoing. One is
identified by token_1, the other one with token_2. Since addresses
are rewritten by the path manager, the attachment to the right
connection is achieved thanks to the token, which is used at
connection establishment and subflow establishment. It is then
remembered. The first column holds the information that is exposed
to the applications, while the last column shows the information that
is actually written in packets that will fly through the network. We
note that additionnally to the addresses, ports can be rewritten,
which contributes to supporting NATs. The table also shows the role
of the token, which is to attach various combinations of ports and
addresses to a single connection. The token is specific to the
built-in path manager, and can be ignored if another path manager is
used. An implementation of the built-in path manager MUST implement
the following options (defined in more details in [5]):
o Add Address (ADDR): Announce a new address we own
o Remove Addresse (REMADDR): Withdraw a previously announced address
o Join Connection (JOIN): Attach a new subflow to the current
connection
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Those options form the default MPTCP Path Manager, based on declaring
IP addresses, and carries control information in TCP options. An
implementation of Multipath TCP can use any Path Manager, but it MUST
be able to fallback to the default PM in case the other end does not
support the custom PM. Alternative Path Managers may be specified in
separate documents in the future.
4.1.2. Generic architecture for MPCTP
Now that the functional decomposition has been shown for MPTCP with
the built-in Path Manager, we show how that architecture can be
generalized to allow the implementation of other Path Managers for
MPTCP. A general overview of the architecture is provided in
Figure 5. The Multipath Scheduler (MPS) learns about the number of
available paths through notifications received from the Path Manager
(PM). From the point of view of the Multipath Scheduler, a path is
just a number, called a Path Index. Notifications from the PM to the
MPS MAY contain supporting information about the paths, if relevant,
so that the MPS can make more intelligent decisions about where to
route traffic. When the Multipath Scheduler initiates a
communication to a new host, it can only send the packets to the
default path. But since the Path manager is layered below the MPS,
it can detect that a new communication is happening, and tell the MPS
about the other paths it knows about.
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Control plane <-- | --> Data plane
+---------------------------------------------------------------+
| Multipath Scheduler (MPS) |
+---------------------------------------------------------------+
^ | |
| | [A1,B1,|pA1,pB1]
| | |
|Announcing new | +-------------+
|paths. (referred | | Data packet |<--Path idx:3
|to as path indices) | +-------------+ attached
| | | by MPS
| | V
+--------------------------------------------\------------------+
| Path Manager (PM) \__________zzzzz |
+--------------------------------------------------------\------+
/ \ | \
/---------------------------\ | /"\ /"\ /"\
| subflow_id Action | | | | | | | |
|<A1,B1,pA1,pB1,1> xxxxx | | | | | | | |
|<A1,B1,pA1,pB1,2> yyyyy | | \./ \./ \./
|<A1,B1,pA1,pB1,3> zzzzz | | path1 path2 path3
+---------------------------+
Figure 5: Overview of MPTCP architecture
From then on, it is possible for the MPS to attach a Path Index to
the control structure of its packets (internal to the MPTCP
implementation), so that the Path Manager can map this Path Index to
the corresponding action. (see table in the lower left part of
Figure 5). The particular action depends on the network mechanism
used to select a path. Examples are address rewriting, tunnelling or
setting a path selector value inside the packet.
The applicability of the architecture is not limited to the MPTCP
protocol. While we define in this document an MPTCP MPS (MPTCP
Multipath Scheduler), other Multipath Schedulers can be defined. For
example, if an appropriate socket interface is designed, applications
could behave as a Multipath Scheduler and decide where to send any
particular data. In this document we concentrate on the MPTCP case,
however.
4.2. PM/MPS interface
The minimal set of requirement for a Path Manager is as follows:
o Outgoing untagged packets: Any outgoing packet flowing through the
Path Manager is either tagged or untagged (by the MPS) with a path
index. If it is untagged, the packet is sent normally to the
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Internet, as if no multi-path support were present. Untagged
packets can be used to trigger a path discovery procedure, that
is, a Path Manager can listen to untagged packets and decide at
some time to find if any other path than the default one is
useable for the corresponding host pair. Note that any other
criteria could be used to decide when to start discovering
available paths. Note also that MPS scheduling will not be
possible until the Path Manager has notified the available paths.
The PM is thus the first entity coming into action.
o Outgoing tagged packets: The Path Manager maintains a table
mapping path indices to actions. The action is the operation that
allows using a particular path. Examples of possible actions are
route selection, interface selection or packet transformation.
When the PM sees a packet tagged with a path index, it looks up
its table to find the appropriate action for that packet. The tag
is purely local. It is removed before the packet is transmitted.
o Incoming packets: A Path Manager MUST ensure that each incoming
path is mapped unambiguously to exactly one outgoing path. Note
that this requirement implies that the same number of incoming/
outgoing paths must be established. Moreover, a PM MUST tag any
incoming path with the same Path Index as the one used for the
corresponding outgoing path. This is necessary for MPTCP to know
what outgoing path is acknowledged by an incoming packet.
o Module interface: A PM MUST be able to notify the MPS about the
number of available paths. Such notifications MUST contain the
path indices that are legal for use by the MPS. In case the PM
decides to stop providing service for one path, it MUST notify the
MPS about path removal. Additionnaly, a PM MAY provide
complementary path information when available, such as link
quality or preference level.
5. Security Considerations
Please see [11] for a threat analysis of Multipath TCP.
6. Interactions with Applications
Interactions with applications - incuding, but not limited to
performances changes that may be expected, semantic changes, and new
features that may be requested of an API, are presented in [6].
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7. Interactions with Middleboxes
TBD?
List of issues that may arise with NATs, firewalls, proxies, etc?
This will be an overview only, and protocol-specific solutions to
this will be given in the companion docments.
8. Acknowledgements
Alan Ford, Costin Raiciu and Sebastien Barre are supported by Trilogy
(http://www.trilogy-project.org), a research project (ICT-216372)
partially funded by the European Community under its Seventh
Framework Program. The views expressed here are those of the
author(s) only. The European Commission is not liable for any use
that may be made of the information in this document.
9. IANA Considerations
None.
10. References
10.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
10.2. Informative References
[2] Postel, J., "Transmission Control Protocol", STD 7, RFC 793,
September 1981.
[3] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and Issues",
RFC 3234, February 2002.
[4] Wischik, D., Handley, M., and M. Bagnulo Braun, "The Resource
Pooling Principle", ACM SIGCOMM CCR vol. 38 num. 5, pp. 47-52,
October 2008,
<http://ccr.sigcomm.org/online/files/p47-handleyA4.pdf>.
[5] Ford, A., Raiciu, C., Handley, M., and S. Barre, "TCP
Extensions for Multipath Operation with Multiple Addresses",
draft-ford-mptcp-multiaddressed-01 (work in progress),
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July 2009.
[6] Scharf, M. and A. Ford, "MPTCP Application Interface
Considerations", draft-scharf-mptcp-api-00 (work in progress),
October 2009.
[7] Srisuresh, P. and K. Egevang, "Traditional IP Network Address
Translator (Traditional NAT)", RFC 3022, January 2001.
[8] Freed, N., "Behavior of and Requirements for Internet
Firewalls", RFC 2979, October 2000.
[9] Border, J., Kojo, M., Griner, J., Montenegro, G., and Z.
Shelby, "Performance Enhancing Proxies Intended to Mitigate
Link-Related Degradations", RFC 3135, June 2001.
[10] Allman, M., Paxson, V., and W. Stevens, "TCP Congestion
Control", RFC 2581, April 1999.
[11] Bagnulo, M., "Threat Analysis for Multi-addressed/Multi-path
TCP", draft-bagnulo-mptcp-threat-00 (work in progress),
October 2009.
Authors' Addresses
Alan Ford (editor)
Roke Manor Research
Old Salisbury Lane
Romsey, Hampshire SO51 0ZN
UK
Phone: +44 1794 833 465
Email: alan.ford@roke.co.uk
Costin Raiciu
University College London
Gower Street
London WC1E 6BT
UK
Email: c.raiciu@cs.ucl.ac.uk
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Sebastien Barre
Universite catholique de Louvain
Pl. Ste Barbe, 2
Louvain-la-Neuve 1348
Belgium
Phone: +32 10 47 91 03
Email: sebastien.barre@uclouvain.be
Janardhan Iyengar
Franklin and Marshall College
Mathematics and Computer Science
PO Box 3003
Lancaster, PA 17604-3003
USA
Phone: 717-358-4774
Email: jiyengar@fandm.edu
Bryan Ford
Max Planck Institute for Software Systems
Saarbrucken,
Germany
Email: baford@mpi-sws.org
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