MULTICHANNEL CONNECTIONS IN FILE SYSTEM SESSIONS
BACKGROUND
[0001] A variety of techniques exists for sharing files, printers, and other resources
between two computers on a network. For example, one application-layer network
protocol for sharing resources is Server Message Block (SMB). SMB is used by
MICROSOFT TM WINDOWS TM and other operating systems to allow two computers
or other resources to communicate, request access to resources, specify intended access of
resources (e.g., reading, writing, etc.), lock resources, and so on. MICROSOFT TM
WINDOWS TM Vista introduced SMB 2.0, which simplified the command set of SMB
1.0 and added many other enhancements. MICROSOFT TM WINDOWS TM 7 and
Server 2008 R2 introduced SMB 2.1, which added opportunistic locking (oplocks) and
other enhancements.
[0002] Most protocols for remote sharing of resources assume a one-to-one relationship
between connections and sessions. A session represents the lifetime of any single request
to access a resource and the subsequent access of that resource until the connection is
terminated. A session may also be associated with a particular security principal and
validated security credentials that determine the actions that are authorized during the
session. A connection can include a Transmission Control Protocol (TCP) or other type of
connection over which higher-level protocols like SMB can communicate to carry out
commands. An SMB session typically involves opening a TCP connection between a
source of a request and a target of the request, sending one or more SMB commands to
access the target resource, and then closing the session.
[0003] Many computers today are connected in such a way that there are multiple
available connections between the computers. For example, datacenter servers are often
built with two or more Network Interface Cards (NICs) so that if one fails network traffic
can be sent over the other one. Client computers may include a wireless network
connection (Wi-Fi), a Bluetooth connection, a wired Ethernet (e.g., Local Area Network
(LAN)) connection, and so forth. Server computers may include a storage area network
(SAN), connections via Fibre Channel, wired Ethernet, and so forth. Some or all of these
connections may provide connectivity to some or all of the same resources.
[0004] Unfortunately, the available connection information is generally unavailable to
an application or application layer protocols that use the network. An application that
requests a connection to a server will typically hand all responsibility for choosing the
device/protocol over which to make the connection to a lower-level network layer, and the
network layer will make a single connection to carry out the application's commands. If
the connection fails, the application or network layer may try another connection by
setting up the session again or may involve manual intervention to do so. Use of a single
connection leads to a fragile connection that is terminated if the connection fails for any
reason, and is unable to leverage the aggregate bandwidth provided by multiple networks.
Some protocols, like the Network File System (NFS) include parallelization extensions
(e.g., pNFS) that allow for use of redundant paths to data to improve throughput, but these
do not provide any information to higher levels that can be used to manage the connection.
Another example is the experimental Multipath TCP (MPTCP) protocol that has a specific
goal of remaining undetected to higher layers for backwards compatibility. The function
of these protocols is completely out of the control of higher layers, and the network layer
may not automatically select the fastest connection on its own or provide the most
efficient use of connections for failover, throughput, or other purposes.
SUMMARY
[0005] A multi-connection information system is described herein that uses multiple
connections to connect to a resource in a single file system session in a way that is
controllable from protocols above a transport layer, such as the SMB application-layer
protocol. The system may also allow a single connection to be shared by multiple
sessions. The concept of a channel is introduced to represent the binding of a particular
session to a particular connection. Sessions can be bound to multiple connections to
enable communication over multiple transports. During the initial negotiation of a
session, a client and server can determine whether multiple connections are supported
between a client and a server within a session. After establishing an initial connection,
additional connections can be established and bound to the existing session. The multiple
connections can be used for failover and/or load balancing. The multi-connection
information system provides a protocol for discovering a capability to establish multiple
channels within a session. The protocol provides information about the available
connections between two particular resources as well as whether the server side and client
side of the connection supports multiple channels within a session. Thus, the multiconnection
information system provides a way to intelligently select and use multiple
connections for a single session at layers above the transport layer.
[0006] This Summary is provided to introduce a selection of concepts in a simplified
form that are further described below in the Detailed Description. This Summary is not
intended to identify key features or essential features of the claimed subject matter, nor is
it intended to be used to limit the scope of the claimed subject matter.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 is a block diagram that illustrates components of the multi-connection
information system, in one embodiment.
[0008] Figure 2 is a flow diagram that illustrates processing of the multi-connection
information system to initiate a session and receive transport information, in one
embodiment.
[0009] Figure 3 is a flow diagram that illustrates processing of the multi-connection
information system to add an additional connection to a previously established session, in
one embodiment.
[0010] Figure 4 is a network packet diagram that illustrates setup of multiple
connections using the multi-connection information system, in one embodiment.
[0011] Figure 5 is a block diagram that illustrates the potential many-to-many
relationship between sessions and connections using the multi-channel information
system, in one embodiment.
DETAILED DESCRIPTION
[0012] A multi-connection information system is described herein that uses multiple
connections to connect to a resource in a single file system session in a way that is
controllable from protocols above a transport layer in the Open Systems Interconnection
(OSI) model, such as the SMB application-layer protocol. The system may also allow a
single connection to be shared by multiple sessions. The concept of a channel is
introduced to represent the binding of a particular session to a particular connection.
Sessions can be bound to multiple connections to enable communication over multiple
transports. During the initial negotiation of a session, a client and server can determine
whether multiple connections are supported between a client and a server within a session.
After establishing an initial connection, additional connections can be established and
bound to the existing session. The multiple connections can be used for failover and/or
load balancing. The multi-connection information system provides a protocol for
discovering a capability to establish multiple channels within a session. The protocol
provides information about the available connections between two particular resources as
well as whether the server side and client side of the connection supports multiple
channels within a session.
[0013] During the establishment of an initial session between a client and a server (e.g.,
an SMB client and server), a negotiation occurs to indicate that both the client and server
support multiple connections within a session. This may include negotiating a protocol
version that provides support for multiple connections. The client can invoke a file system
control message (FSCTL) or other application-programming interface (API) to obtain a
list of server transport interfaces. In alternative embodiments, the client can query a DNS
service to get more information on server network interfaces and capabilities. The client
can also find the local interfaces associated with each server IP address and gather
additional information about local interfaces, including type and speed. The client can
then select an interface for establishing an initial connection. In some embodiments, the
client establishes the initial connection first and then uses that connection for negotiating
information with the server about other available transports. For the establishment of
additional channels, the client can sort the multiple interfaces by type and speed to
determine the top interfaces and establish additional channels using the top interfaces.
After the client has established multiple channels, some channels that are not in the top
interfaces can optionally be torn down (or simply not used) in favor of using channels that
are ranked higher based on type and speed. Thus, the multi-connection information
system provides a way to intelligently select and use multiple connections for a single
session at layers above the transport layer.
[0014] Figure 1 is a block diagram that illustrates components of the multi-connection
information system, in one embodiment. The system 100 includes a session initiation
component 110, a channel discovery component 120, a channel selection component 130,
a binding component 140, a command receiving component 150, a command routing
component 160, and a failover handling component 170. Each of these components is
described in further detail herein.
[0015] The session initiation component 110 receives requests to initiate a session
between a client and server for sharing one or more resources. For example, the
component 110 may receive a request from an application running on a client that
identifies a server to which the application wants to connect to access files or other
resources. The session initiation component 110 may receive an SMB initial request, such
as a "Negotiate" message that opens communications between a client and server. The
session initiation component 110 creates sessions in response to application requests and
may provide security information, such as a request user's authentication information, so
that the server can respect any restricted network access to resources.
[0016] The channel discovery component 120 determines one or more connection
transports that are available for communication between the client and server. Clients and
servers may be connected by a variety of transports, such as Ethernet and Wi-Fi, as well as
redundant connections of the same transport, such as two Ethernet NICs. In addition,
some connection transports may support capabilities, such as Remote Direct Memory
Access (RDMA) that affect the speed of one connection transport over another. The
channel discovery component 1 0 gathers this type of information and collects the
information for the client to use in selecting an appropriate transport. The component 120
may use an initial connection to the server to identify server transport interfaces and
negotiate multiple channels for connections. The component 120 may also gather
information outside the client and server, such as querying a DNS server for information
about connection types available to the server.
[0017] The channel selection component 130 selects one or more connection transports
from the determined available connection transports to bind to the session between the
client and the server. In some cases, the client will establish a first connection to the
server, and then upon discovering that some condition exists, will use information
discovered via the first connection to later establish additional connections to the server.
For example, the condition may include detecting that the client is sending a large amount
of data to the server that will take a long time over the initial connection. The condition
may also include determining that the client has a high expectation of reliability for the
session between the client and server, such that redundant connections may be helpful for
failover. The channel selection component 130 can be modified or configured by an
application or particular implementation of the system 100 to select connections based on
goals and priorities that are significant to the particular implementation. For example,
some implementations may favor making connections over the fastest transport
connections first, while others may reserve fast connections for certain types of network
traffic and use slower or lower priority connections for other types of traffic.
[0018] The binding component 140 associates the selected connection transports with
the session. A session captures information about a security principal associated with a
particular series of communications between the client and server. The session may also
contain other metadata that defines capabilities or commands available for the particular
series of communications. Binding a selected connection transport to the session makes
that connection transport available for use for that session, and may negotiate any security
credentials or other exchange with the server to prepare the connection for use with the
session. Note that just as a single session may bind to multiple connections, multiple
sessions may also bind to a particular connection. The connection provides the conduit
over which communications travel between the client and server while the session gives
each communication semantic meaning in the context of what the application layer is
trying to accomplish or is allowed to do.
[0019] The command receiving component 150 receives one or more commands related
to a session between the client and the server. The purpose of being able to communicate
between the client and server is for the client to send commands to access resources. For
example, the client may send an "open" request to open a file or a "lock" request to
prevent others from accessing a file while the client modifies the file. The command
receiving component 150 receives these commands and invokes the command routing
component 160 to determine one or more transports over which to send the command. In
some embodiments, the system 100 guarantees that a response will be sent over the same
transport connection over which a corresponding request was sent. Thus, by routing a
particular command to a particular transport connection, the client can also select how data
related to the request will be returned to the client. For large data and varying connection
speeds, selecting appropriately can dramatically affect the overall duration of the
operation.
[0020] The command routing component 160 selects a connection transport bound to a
session over which to send a particular command. The command routing component 160
split commands up and use multiple transports to carry out the command, such as for
retrieving large files or sending large files. The component 160 may also select fast
connection transports for some commands while selecting slower or less frequently
utilized connection transports for lower priority commands. The command routing
component 160 may also determine that additional available transport connections should
be bound to the session, such as upon receipt of a request to transfer a large file that will
be too slow over the existing bound connections. The command routing component 160
may also detect imminent connection maintenance or outages and cause additional
connections to be made to ensure reliability.
[0021] The failover handling component 170 handles a disconnection of a particular
transport connection from the session. For example, a network wire could be cut, a NIC
could fail, or other conditions could lead to a connection that worked previously being
disconnected. The failover handling component 170 determines whether other
connections are available, and may invoke other components, such as the channel
discovery component 1 0 to select additional channels and the command routing
component 160 to route commands to a non-disconnected connection. The failover
handling component 170 may also handle replaying any commands that were queued on
the disconnected connection transport and waiting for the server's responses over another
transport connection so that the commands are carried out reliably in spite of the failure.
In this way, the system 100 provides higher reliability.
[0022] The computing device on which the multi-connection information system is
implemented may include a central processing unit, memory, input devices (e.g., keyboard
and pointing devices), output devices (e.g., display devices), and storage devices (e.g.,
disk drives or other non-volatile storage media). The memory and storage devices are
computer-readable storage media that may be encoded with computer-executable
instructions (e.g., software) that implement or enable the system. In addition, the data
structures and message structures may be stored or transmitted via a data transmission
medium, such as a signal on a communication link. Various communication links may be
used, such as the Internet, a local area network, a wide area network, a point-to-point dialup
connection, a cell phone network, and so on.
[0023] Embodiments of the system may be implemented in various operating
environments that include personal computers, server computers, handheld or laptop
devices, multiprocessor systems, microprocessor-based systems, programmable consumer
electronics, digital cameras, network PCs, minicomputers, mainframe computers,
distributed computing environments that include any of the above systems or devices, set
top boxes, systems on a chip (SOCs), and so on. The computer systems may be cell
phones, personal digital assistants, smart phones, personal computers, programmable
consumer electronics, digital cameras, and so on.
[0024] The system may be described in the general context of computer-executable
instructions, such as program modules, executed by one or more computers or other
devices. Generally, program modules include routines, programs, objects, components,
data structures, and so on that perform particular tasks or implement particular abstract
data types. Typically, the functionality of the program modules may be combined or
distributed as desired in various embodiments.
[0025] Figure 2 is a flow diagram that illustrates processing of the multi-connection
information system to initiate a session and receive transport information, in one
embodiment. Beginning in block 210, the system receives from an application a request to
initiate a session between a client and a server. The application may include operating
system components or other service-level applications, as well as typical client
applications. Many types of applications and services connect to a server to share files,
printers, or other resources. Upon receiving the request, the system begins setting up a
session and may send one or more packets to the server to negotiate available dialects of
the network protocol used to communicate between the client and server, as well as to
detect other capabilities of the client and server to ensure compatibility. During this
process, the server may indicate that it supports multi-connection sessions so that the
client can leverage the techniques described herein to increase throughput, improve
failover, and so forth.
[0026] Continuing in block 220, the system selects an initial transport for sending
commands between the client and server. The system may default to one type of transport
for the first connection, such as an Ethernet connection on a first NIC, or may select based
on application-specified criteria. The criteria may indicate to select the fastest connection,
the connection with the highest bandwidth, the most robust connection, or any other
criteria helpful to the application. Continuing in block 225, the client establishes an initial
connection to the server. Because the client and server share information about available
transports, the client is able to choose an appropriate connection for any particular session.
[0027] Continuing in block 230, the system determines one or more available transports
for establishing a second connection between the client and the server. The system has
both internal and external means of determining the available transports. External means
are those outside of the client/server connection, such as querying a separate DNS server,
datacenter metadata, or other information. Internal means are those within the connection
between the client and the server, such as sending a capabilities request or query to
identify available devices and transports. The client can identify local transports by
querying the client operating system or by querying the server over the initial connection.
The multi-channel information system compiles a list of available transports and any
metadata discovered about the transports that may help in determining under what
conditions to use each transport.
[0028] Continuing in block 240, the system establishes a second connection via the
selected transport. For example, if the protocol is SMB, then the client may send a
negotiate message over the selected transport that sets up an SMB connection. Individual
connections may appear as they do in systems today, with the bind step combining the
single connections into a single session. Establishing the connection may involve several
packets going back and forth between the client and server to perform any connection
setup and gather any metadata needed for using the connection.
[0029] Continuing in block 250, the system binds the established second connection to
the session of the initial connection. Binding informs the system that the session is
affiliated with the connection and that the system can use the connection for sending
commands. The system may track which connections are bound to which sessions, so that
as sessions close or connections disconnect, the system can clean up appropriately. After
all sessions that use a connection have ended, the system can close the connection.
Similarly after all connections have disconnected that are bound to a session, the system
can clean up the session.
[0030] Continuing in block 260, the system sends a command received from the
application through either established connection bound to the session. The system may
select among multiple such connections to choose a connection suited to the current
command. The system may consider bandwidth, latency, current queue depth, battery
power (e.g., for a mobile device), priority, or any other factors to select the connection for
handling the command. The system may also split the command to use multiple
connections concurrently to speed up operations. Continuing in block 270, the system
receives a response to the sent command via the same transport used to send the
command. The received response may indicate whether the command was successful,
may include requested data, or any other response defined for a particular request.
[0031] Continuing in decision block 280, if there are more commands or the session has
not been closed, then the system loops to block 260 to send more commands, else the
system completes. The system continues in this way, sending commands associated with a
session over available connections. If at any point the system determines that additional
connections would be helpful to carry out commands, then the system may establish and
bind additional connections to the session for commands to use. After block 280, these
steps conclude.
[0032] Figure 3 is a flow diagram that illustrates processing of the multi-connection
information system to add an additional connection to a previously established session, in
one embodiment. The steps of Figure 3 may occur after those of Figure 2 after a particular
condition is detected or a threshold is reached for expanding a session from a single
connection to multiple connections. For example, the system may detect a large file
transfer that would complete faster over multiple connections.
[0033] Beginning in block 310, the system detects a condition for establishing an
additional connection for a previously established session that already has at least one
bound connection between a client and a server. The condition may include exceeding the
bandwidth of existing connections, latency too high on existing connections, wanting
additional bandwidth for an upcoming command requesting or sending large data, and so
on. Upon detecting the condition, the system performs the following steps to add
additional connections to the session.
[0034] Continuing in block 320, the system selects an additional transport from a
previously discovered list of transports. The system may discover the transports through a
capabilities request to the server, by querying DNS information, or any other mechanism
for discovering ways to connect the client and server. The system may sort the available
transports and/or select a transport based on characteristics received during discovery. For
example, the system may prefer a connection with a high bandwidth, a connection with
high availability, a connection that is currently idle, and so forth.
[0035] Continuing in block 330, the system establishes a connection via the selected
transport. Establishing a connection may include establishing a transport layer connection,
such as via TCP/IP, as well as session protocol negotiation, such as an SMB negotiate
sequence. The system may also exchange metadata over the established connection to
confirm the connection type and receive any setup information for using the connection
(e.g., whether the connection supports certain features, such as selective
acknowledgements, and so on).
[0036] Continuing in block 340, the system binds the newly established connection to
the existing session, so that the session has multiple available connections from which to
select when sending commands. Binding may associate a connection that is already
associated with another session to the current session, so that both sessions can leverage
the connection. Binding also informs the session about the connection, so that if the
session closes session management logic can perform appropriate cleanup steps to unbind
and/or close the connection.
[0037] Continuing in block 350, the system receives an application-level command
destined for the server to which there are now multiple connections. An application may
request to open a file, request to print to a shared printer, or perform other common shared,
remote usage of a resource. The operating system or other service code may provide one
or more application programming interfaces (APIs) through which applications can invoke
the system to send commands to the server.
[0038] Continuing in block 360, the system selects one or more transports among the
newly established connections and one or more previous connections over which to send
the received command. The system may route commands to a default connection unless
one or more threshold criteria are met, such as a request for a large amount of data. Upon
receiving a larger request, the system may select a higher bandwidth connection or split
the command to use multiple connections to complete the operation specified by the
command faster. As another example, the system may detect when a connection goes
down and use alternate connections as a method of smooth failover transparent to an
application. After block 360, these steps conclude.
[0039] In some embodiments, the multi-connection information system provides a file
system API within an operating system through which applications or services at a client
can request information about available network interfaces of a remote server. For
example, MICROSOFT TM WINDOWS TM uses file system control messages (FSCTLs)
for interacting with one or more file systems. The system may add a message,
FSCTL LMR QUERY TRANSPORT INFO that is a command for requesting active
network interfaces of the remote server. One structure that a server may provide in
response to this command includes the following members described in further detail
below: Next (4 bytes), Iflndex (4 bytes), Capability (4 bytes), RssQueueCount (4 bytes),
LinkSpeed (8 bytes), SockAddr_Storage (128 bytes).
[0040] The Next member provides the offset from the beginning of the current structure
to the beginning of a subsequent 8-byte aligned network interface. The Next member is
set to zero as a null terminator when no further network interfaces follow. The Iflndex
member provides a numerical index for the current network interface. The Capability
member contains flags that indicate capabilities of the current network interface, such as
whether the interface is RDMA or Receive Scaling Support (RSS) capable. The
RssQueueCount member indicates an RSS queue count for RSS capable interfaces. In
some cases, the system uses the RSS queue depth as a hint as to how many connections to
make using a particular NIC. The LinkSpeed member indicates a speed of the interface in
bits per second. The SockAddr Storage member indicates a network interface address for
establishing connections using the interface. This field can use the well-known sockets
structure SOCKADDR STORAGE.
[0041] Figure 4 is a network packet diagram that illustrates setup of multiple
connections using the multi-connection information system, in one embodiment. In this
example, a client 405 establishes multiple connections to a server 495 by sending the
following packets (or multi-packet messages). The client 405 sends a first negotiate
request 410 to the server 495. The server 495 responds with a negotiate response 420 to
the client 405. The client 405 then sends a first session setup request 430 to the server
495. The server 495 responds with a session setup response 440 to the client 405. The
session setup may make multiple round trips between the client and server. At this point,
the first channel for the session is established and the client can begin sending commands
to the server using the session. Subsequently (it may be immediate or some time later),
the client 405 decides to establish a second connection to the server 495 for the same
session. The client 405 sends a second negotiate request 450 over the new transport to the
server 495. The server 495 responds with a negotiate response 460 to the client 405. The
client 405 then sends a second session setup request 470 to the server 495. Unlike the first
session setup request 430, this request 470 may include a binding flag that indicates to
attach the new connection with the previous session. The server 495 responds with a
session setup response 480 to the client 405. This session setup also may make multiple
round trips between the client and the server. At this point, both connections are available
to the client for sending commands to the server.
[0042] Figure 5 is a block diagram that illustrates the potential many-to-many
relationship between sessions and connections using the multi-channel information
system, in one embodiment. The diagram includes a first session 510 and a second session
520. The diagram also includes a first connection 530 and a second connection 540.
Traditionally, each session had a one-to-one relationship with a connection, such that the
first session 510 would have been the only session using the first connection 530, and the
second session 520 would have been the only session using the second connection 540.
Using the techniques described herein, the concept of channels is introduced, whereby
each session may use multiple connections and may even share connections with other
sessions. Thus, as shown the first session 510 is bound to the first connection 530 through
a first channel 550. The first session 510 is also bound to the second connection 540
through a second channel 560. Likewise, the second session 520 is bound to the first
connection 530 through a third channel 570, and the second session 520 is bound to the
second connection 540 through a fourth channel 580. Thus, either session can use either
connection as dictated by application or implementation-specific preferences.
[0043] In some embodiments, the multi-connection information system does not inform
the application of available connections. As noted herein, the system can be implemented
at a layer between applications and a transport layer (e.g., TCP). For example,
MICROSOFT TM WINDOWS TM provides an SMB implementation that applications
can use. The system can perform the techniques described herein to automatically use
multiple transports when available and to provide applications with higher reliability and
throughput automatically, without input by the application. The system may allow the
application to configure whether the capability is enabled. If the capability is on, the
system may automatically pick the transports over which to establish connections and
which transports to use for various commands from the application. In other
embodiments, the system may provide more control to the application, so that the
application can establish the criteria for selecting each connection or make the selection
itself.
[0044] From the foregoing, it will be appreciated that specific embodiments of the
multi-connection information system have been described herein for purposes of
illustration, but that various modifications may be made without deviating from the spirit
and scope of the invention. Accordingly, the invention is not limited except as by the
appended claims.
CLAIMS
1. A computer-implemented method for initiating a session allowing multiple
connections in a file system and receiving transport information, the method comprising:
receiving from an application a request to initiate a session between a client and a
server;
determining one or more available transports available for establishing a
connection between the client and the server;
selecting an initial transport for sending commands between the client and server;
establishing a connection via the selected transport;
binding the established connection to the initiated session; and
sending a command received from the application through the established
connection bound to the session,
wherein the preceding steps are performed by at least one processor.
2. The method of claim 1wherein receiving the request comprises receiving a request
from an application to access a file stored remotely on the server using Server Message
Block (SMB) protocol.
3. The method of claim 1wherein receiving the request comprises setting up a
session and sending one or more packets to the server to negotiate available dialects of the
network protocol used to communicate between the client and server.
4. The method of claim 1wherein receiving the request comprises querying the
server to determine whether the server supports multi-connection sessions.
5. The method of claim 1wherein determining available transports comprises
querying a domain name system (DNS) server to identify one or more addresses of the
server.
6. The method of claim 1wherein determining available transports comprises
querying a client operating system to identify available network interfaces.
7. The method of claim 1wherein determining available transports comprises
querying sending a capabilities request to the server to identify available network
interfaces on the server.
8. The method of claim 1wherein selecting the initial transport comprises selecting
based on application-specified criteria that establishes the application's connection
preferences.
9. The method of claim 1 wherein establishing the connection comprises sending a
negotiate message over the selected transport that sets up a Server Message Block (SMB)
connection.
10. The method of claim 1 wherein binding the established connection comprises
preparing the connection for use by the session for sending commands from the client to
the server.
11. The method of claim 1 wherein binding the established connection comprises
storing information for cleaning up the session and/or connection.
1 . The method of claim 1 wherein sending the command comprises selecting among
multiple bound connections to choose one or more connections suited to handling the
current command.
13. A computer system for providing multichannel connections in file system sessions,
the system comprising:
a processor and memory configured to execute software instructions embodied
within the following components;
a session initiation component that receives requests to initiate a session between a
client and a server for sharing one or more resources;
a channel discovery component that determines one or more connection transports
that are available for communication between the client and server;
a channel selection component that selects one or more connection transports from
the determined available connection transports to bind to the session between the client
and the server;
a binding component that associates the selected connection transports with the
session;
a command receiving component that receives one or more commands related to a
session between the client and the server; and
a command routing component that selects a connection transport bound to a
session over which to send a particular command.
14. The system of claim 13 wherein the session initiation component is further
configured to receive a request from an application running on the client that identifies the
server to which the application wants to connect to access files or other resources.
15. The system of claim 13 wherein the channel discovery component is further
configured to determine whether each connection transport supports Remote Direct
Memory Access (RDMA) and/or Receive Scaling Support (RSS).