A primer for consumers, advocates and policy makers
Network management – the process used to maintain the integrity and operations of a communications
network – is a beneficial and necessary function of modern networks that has nonetheless become
embroiled in the controversies related to network neutrality and traffic congestion on the Internet.
This three-part series examines network management – what it is, how it works, what it means to
consumers, and what policies would most benefit consumers and network operators in their efforts to
maintain effective communications. Part I defines network management.
The Internet was initially designed with the
simple goal of assuring an ability to connect Network Management
among private, government and academic
1. All networks require management to
networks. The quality and reliability of the
carry out their mission of effectively
connection was not a key focus.
connecting two or more points on the
The original concept was that the network
would remain simple and "dumb" in order to 2. The purpose of network management is
maximize the ability to establish to enhance the reliability and viability
connections, and that management of the of the network.
communications would be the responsibility
of the software on the devices that used the 3. Network management practices differ
connection. for each layer of the network.
But the theoretical concept of a "dumb" 4. Practices at each level must
network quickly gave way to the necessity interconnect with and support one
for management within the network itself -- another.
to keep data flowing smoothly by avoiding
congestion points caused by variable loads and 5. Network management practices should
equipment failures. The original IP protocol optimize the experience of all users.
was augmented with a "Transmission
Control Protocol" (TCP) to manage 6. No application or user should be
problems of data loss, leading to the TCP/IP permitted to contravene, interfere with
protocol suite that is the foundation of the or compromise these management
“best efforts” Internet today. practices, since to do so would reduce
the reliability and viability of the
Other network management enhancements network.
followed -- real-world needs for firewalls,
network address translators, web content caches
and the like been necessary to allow for the more
sophisticated applications and critical data that
flow over the commercial Internet
To put it in simple terms, every network The commonly-accepted model for the
must have some system to ensure the flow of Internet has five layers.1
data. Even a network consisting of two tin Application Layer
cans and a string must have a system to
ensure that the string remains connected and
taut; otherwise, communications will fail. In Transport Layer
the case of today's communications
networks, that system is called "network Network Layer
Data Link Layer
How The Internet Works
Some parties continue to portray "The
Internet" as a single global structure of The Five-Layer Internet Model
"dumb pipes" that connect computers, users
and applications the world over. In fact, the
Internet consists of tens of thousands of Under this model, the Physical Layer represents
the building blocks for a connection – the
individual networks that are separately physical cables, wireless frequencies, the
owned and administered. satellite signals, the microwaves and light beams
over which communication is carried. It also
Each of these networks has its own mission, includes the physical interfaces between the
its own requirements, its own priorities and various elements and the specification for how
its own network management practices. “bits” are transmitted.
Equally important, the Internet operates on
underlying physical networks that also The Data Link Layer represents the ability to
support a multitude of other uses and users, create an end-to-end connection between two
both IP-based and non-IP-based capabilities. fixed locations (or physical addresses). In effect,
How, then, is the Internet able to operate? it is the roadway between two locations.
The Network Layer is where software and
The answer lies not only in a common
computers control the flow of
protocol, TCP/IP, but in the structured and
communications over the networks
rational manner by which the underlying
described above. This layer identifies the
physical networks operate.
association between physical addresses
(fixed locations on the network) and an
element that is not necessarily stationary –
such as a laptop or cell phone.
A Model Of The Internet
In order to understand this, it is helpful to The "Internet model" is actually derived from the
understand the layers of functionality that seven-layer "Open Systems Integration model." The
Internet model is not official, but is commonly used
work together to make communications as an easy way to think of how the Internet works. It
possible. combines the OSI model's Application, Presentation
and Session layers into a single layer labeled
“Application”. For our purposes, this consolidation
is not an issue.
not concerned with either the content in
The Transport Layer is a mechanism that the packet or the destination.
validates that content reaches its destination.
It is at this level that error detection and The Network Layer is where a
device-to-device flow control come into continually updated “picture” of network
play. When TCP is employed, it adjusts the configurations is stored. This allows
flow rate between two specific connected multiple uses and users to share the same
devices in response to congestion. underlying physical capacity – one of
such uses being the public Internet.
Finally, the Application Layer is where bits Network management reduces the cost
are broken down and reassembled to enable for all users by optimizing the use of
users to interact with web browsers, email available physical capacity. Critically,
systems, and other applications that are the available capacity is not constant due
reached through the public Internet. to the continually changing load as well
as equipment and facility failures.
For the Internet, this is where a path is
Network Management selected for sending packets between
users and content sources. A fixed end-
Just as each of these five layers performs a to-end path does not exist. Rather, a
different function in making path with available capacity is defined
communications possible, each uses between points (or routers) and packets
different kinds of network management: are sent between them one hop at a time.
At the Physical Layer, network Each hop relies on software logic to
management focuses on monitoring the continually move the packets closer to
performance of physical equipment and their ultimate destination. This path is
facilities in order to detect problems subject to continual updating to reflect
such as a cut cable, a faulty circuit board changing network conditions.
and the like. When an issue is detected,
network management procedures A substantial amount of network status
generally call for a switch to a back-up information must be updated
component or a switch to another path to continuously in order for the Internet to
prevent or minimize disruption to the efficiently move billions of packets per
flow of information. After the traffic second. Whenever a physical route is
flow is shifted, the defective element can overloaded, an alternate route must be
be repaired. identified and used until the capacity
constraint is resolved.
The Data Link Layer is where the
performance of the connection between When this happens, packets may be
two points in a larger physical network slowed in their journey (increased
are monitored and managed. latency), may arrive at a non-uniform
Management practices at this level focus rate (increased jitter) or, in the extreme,
on the integrity of the flow of data and not arrive at all (packet drop). Such
the capacity available to handle it. It is events can happen at any time within
any individual physical network used in managed separately by that network’s
the Internet communication chain. operator.
The Transport Layer addresses the In the real world, cables get cut (by accident
computer-to-computer packet flow. This or otherwise), electronics and software
is where the "TCP" part of the Internet periodically fail. While engineers carefully
plays its important role.2 TCP operates plan for all type of uses of the physical
to monitor for increased latency, jitter or capacity, they are not perfect in their
packet loss, any one of which could predictive powers. As a result, load spikes,
indicate network congestion and could whether due to legitimate or malicious
affect application performance. traffic, are a fact of life. When these events
occur, engineers must take steps to assure all
Finally, there is the Application Layer. competing uses of capacity, including the
The application layer, as it relates to Internet, have equitable access to the
network management, insulates the user network’s capacity.
from visibly experiencing minor degrees
of variability in connection performance. Network management practices, at all levels,
Primarily, this involves “buffering” – the are designed to assure sensible sharing of a
temporary storage of incoming data so physical network and to permit a variety of
that it can be delivered at a more uses to co-exist and operate in an efficient
consistent speed and interval. manner. This saves money for everyone.
Application layer functions may also
include screening or filtering to prevent Because the Internet is a network of
unwanted incoming data, such as viruses thousands of individual private networks --
or other harmful transmissions, from each with their own design, policies and
being processed. practices -- effective network management
is a challenging task.
Internet users want their communications to
be reliable, even though the original design There is no central organization or body to
of the Internet favored simple connections impose a single set of rules on a
over reliability.3 Relatively few people configuration that extends to almost every
understand that the Internet is not managed nation and billions of individuals around the
by a single service provider. Rather, each world. There is no simple “cook book” for
network that makes up the Internet is network management, nor could one be
TCP is also used and useful for IP-based networks
other than the public Internet. In addition, other Because of the complexity and scope of the
transport flow mechanisms (e.g., UDP) can be used Internet, network engineers and network
in conjunction with IP and may also operate on the managers must continually reassess and
Internet. TCP is discussed as a non-exhaustive
example of Transport Layer functionality. adapt the approaches they use. Network
Internet mythology says that the Internet was managers need a wide array of tools that can
designed simply and with little or no reliability so be quickly applied and adapted to the
that it could survive a nuclear attack. While this may situation at hand.
have been a policy consideration, the over-riding
engineering consideration was to find a way to
connect literally hundreds of different types of
networks in a way that would let them "talk" to one
Network Management In Practice example, a particular path may not be
available for use. But the same is also
Network management practices can be true of other layers – if a hacker attacks
summarized in six general statements: the Application Layer (i.e., the end user)
it may generate such a load that the
1. All networks require management to Transport Layer cannot adapt or the
effectively support communications Network Layer cannot find enough
between two or more points. In the capacity to deliver legitimate traffic.
real world, networks that are not
managed have substantial performance Therefore, the management practices at
variability. But, stable and predictable each layer must not only be compatible
performance is critical for advanced with one another, but must work in
applications such as online banking, tandem to be effective. Any action taken
video streaming, Voice over IP to remove or weaken a practice at one
telephony and eHealth. level will affect every other level,
potentially jeopardizing the reliability of
2. The purpose of network management the entire network.
is to enhance the reliability and
affordability of the network. Network 5. Network management practices
management, at its heart, is concerned should optimize the experience of all
with three things. First, it protects the users. In today's world, a myriad of
network – and, by extension, every applications, communications and users
computer and user on the network – must be accommodated at the same time
from security threats. Second, it works on each physical network used.
to ensure the performance of the Network management provides the
applications using the network. Third, it means to handle day-to-day variations in
seeks to maximize the availability and capacity requirements implicit in a
use of capacity. By succeeding in this dynamic environment such as the
area, costs are held down for all users. Internet, and does so in ways that
benefits all users.
3. Network management practices differ
for each layer of the network. Each 6. Networks users and application are
layer addresses different functionality, expected to respect the integrity of the
so in turn the management techniques network and act in accord with
must focus on the purpose served by a management practices. Unfortunately,
particular layer. Regulating one “layer” some Internet users act in unacceptable
jeopardizes the overall effectiveness of ways. Hackers assault destinations on
all layers and likely requires active the Internet in an effort to steal
regulation of all layers. information, inject viruses, disrupt traffic
flow, or damage targeted organizations.4
4. Practices at each level must work with Others use the network to perpetrate
and support one another. The Internet, frauds and some users send large
and any other IP-based network, is volumes of spam. Users of the Internet
designed in a way that each layer
supports those above and below. If there 4
The Pentagon, headquarters for the military of the
is a failure in the Physical Layer, for United States, claims that it suffers from three million
attempted hacker attacks each day.