Diagnosis and Performance Monitoring - Deploying and Managing a Cloud Infrastructure - page 133

or a few at a time compared to having bonded links, which allows more packets to pass
through at once. As an analogy, think of it as a highway: if you have four cars going to
the same destination, approximately 10 minutes away, and they are traveling at the same
speed on a single-lane road, they would arrive one after the other, with the fourth car pos-
sibly arriving at the 12-minute mark. If you have more cars, it would take more time for all
of them to arrive. Now if you have four lanes, then all four cars would arrive at the same
time, in exactly ten minutes, saving you two minutes. This value just scales up the more
cars you have and the more lanes you have. This is bandwidth aggregation, and all of those
links act as a single large one.
An example of bonding is PPP multilink, where the aggregate bandwidth is the sum of
the individual physical connections. The Multilink Protocol (MP) is an extended version of
Point-to-Point Protocol (PPP), which has the ability to bond multiple parallel connections
together where the resulting virtual connection is equal to the sum of the individual band-
width of each separate connection. Packets are broken up and then distributed over avail-
able links. This technology, however, needs compliant hardware or software at both ends
of the link because these packets need to be recombined and properly sequenced, so this
is doable only with a point-to-point connection from a client toward a directly connected
server. This can be done even if the available links are not using the same bandwidth or
connection speed, and it increases throughput dramatically and provides good redundancy
and failover protection between the connected points.
Teaming
NIC teaming, or connection teaming, is different from bonding, contrary to most people's
belief that they are synonymous, though they are both under the greater umbrella of link
aggregation. Unlike PPP multilink, teaming links do not terminate as pairs of end points;
instead, it is a form of bandwidth aggregation, which does not bond the different links but
only makes them work together as a team.
Each link in a team is set up so all the links maintain individual TCP/IP sessions using
standard protocols. Basically, you have two or more separate connections. Teaming is often
used in a LAN environment with multiple client computers simultaneously connecting
to the Internet through a common gateway. NIC teaming is implemented in the gateway,
which is now referred to as the connection teaming server . The teaming server maintains
multiple connections to the outside or to the Internet. It can have vastly different connec-
tion types, such as a DSL connection, a fiber channel, and a dial-up modem all working at
the same time but not as a whole. The teaming server manages routing between the LAN
and the Internet; it selects the best connection for the type of request or application that
is being requested by the client computer. For example, one client opens an FTP link and
downloads a large file. This connection uses the largest bandwidth link available, which
is the fiber channel, but the client will not gain throughput like that of a bonded connec-
tion because it is just using a single connection. This act of downloading a large file would
be enough to congest a single-link network, but a teaming connection allows for different
connection channels for data to go through. So while one user takes up the fiber channel
with their huge download, other users simply browsing the Web with minimal bandwidth
requirements will be routed using the free links, the DSL and dial-up ones.