Network Administration: Easing Away Tensions

A t the

end of the day, your enterprise network could make you tear

your hairs out ...

The rapid

development and acceptance of network technologies and applications

to gain a competitive advantage introduces significant traffic

management challenges. Keeping the network "up" is

no longer sufficient: the network must be an active component

in providing enterprise connectivity. Administrators must deliver

predictable and cost-effective performance levels for a diverse

set of corporate stakeholders. With organizations relying on

the Internet and corporate intranets to support core business

processes, network performance has become a bottomline business

metric. In addition, enterprise traffic issues may also impact

the integrity of the corporation's network security.

Without

consistent and reliable performance levels, the network cannot

provide the necessary infrastructure to deliver valuable information

to employees, suppliers, and customers. The result may be missed

business opportunities and lost revenues. The following are

a few examples of network-based performance problems and their

results:

• Customers
  
  cannot access information on the company's web servers quickly
  
  enough, resulting in lost business
  
  
  
  
• E1/64
  
  kbps leased links are added to accommodate rising bandwidth
  
  needs, but without a noticeable improvement in service
  
  
  
  
• Each
  
  new network application results in a precipitous drop in performance
  
  
  
  
• Consolidation
  
  of servers across the backbone results in performance degradation.
  
  
  
  

In addition

to causing serious business and productivity problems, enterprise

traffic issues may also impact the integrity of the corporation's

network security. All too often, when individual users become

frustrated with unreliable service, they attempt to establish

Internet connectivity outside the corporate infrastructure -

thereby compromising the enterprise security policy and putting

the entire network at risk. Enterprise traffic management is

an on-going challenge because it encompasses a number of variables.

Network

Performance Variables



Some of the variables that affect the performance of enterprise
networks include:

Criticality





Organizations depend on the corporate network to support core
business processes, such as accounting, sales, and operations.

Poor network performance can cripple these processes, dramatically

affecting business productivity. Criticality is magnified as

network resources are extended to external users, through an

extranet or by using the Web as a vehicle for advertising, product

information, and direct sales. These scenarios bring many more

users into the enterprise network environment, placing additional

stress on network performance. More than just a measure of availability,

criticality today involves performance requirements such as

response times, file transfer times, and network latency.

Complexity



The deployment of intranets and extranets adds significant complexity
to enterprise networks. Network administrators must manage traffic

not only on the backbone and on internal network segments, but

also at WAN access points. Matching the data rates of local

area networks (e.g., Ethernet or Fast Ethernet) to the limited

capacity of a corporation's wide area connection introduces

a potential performance bottleneck. In addition, the growing

number of Internet-based applications and services creates additional

performance demands. The wide range of content importance requires

dynamic traffic management to balance conflicting demands and

ensure adequate levels of service.



Return on Investment (ROI)

Over the

last decade, corporations have made massive investments in network

infrastructures. As with any corporate resource, this investment

must be actively managed to capture its full benefit. By effectively

managing the performance of LAN and WAN infrastructures, organizations

not only can support critical applications, but also can extend

the life of the network and maximize ROI. It is important to

note that organizations should avoid a "design by hope"

strategy that throws excess infrastructure and capacity at performance

problems in the hope of alleviating the problem. Too often,

the result is that the points of congestion or performance degradation

are shifted, rather than resolved. Dynamically managing the

performance of the existing network can obviate or defer the

need to make additional investments in hardware, bandwidth,

or server capacity.

Dynamism





The dynamic nature of networks creates additional challenges
to providing consistent and reliable performance levels. In

today's Internet-centric network, traffic patterns change rapidly

and unpredictably. This is becoming especially true as Web-based

services proliferate. The availability of new content on the

Web can shift traffic patterns and volumes dramatically in very

short periods of time. Other emerging technologies, including

audio and video streaming applications and "push"

services, add to the dynamic condition of networks. The inelastic

nature of real-time streaming requires guaranteed network performance.

Without adequate traffic management, the bandwidth necessary

to provide continuous streaming will not be available.

Similarly,

push applications typically transfer data in large bursts across

the network, rapidly consuming limited network resources. An

effective traffic management solution can assign appropriate

privileges for these applications so that more important services

or users are not starved of network bandwidth. In dynamic environments,

a network's performance history cannot be used to predict future

network needs. Traffic management for dynamic networks must

be policy-based, provide coverage for the entire enterprise,

and must actively provide analysis and feedback so the network

can adapt to changing network conditions. An effective traffic

management solution allows network administrators to balance

these often conflicting variables and provide a predictably

high quality of service.

... Get

this done right away, if you have to survive ...



Setting a Network Equilibrium Point


In order to provide a consistent quality of service for users,
network administrators must establish a "network equilibrium

point" that specifies a target state for the traffic management

system to maintain. A stable network equilibrium point gives

administrators a level of network control not possible with

traditional enterprise management approaches. For example, many

earlier traffic management tools simply "reserved"

a fixed amount of bandwidth for a given application or service.

Unfortunately, a reservation is a static control mechanism and

cannot adapt to the dynamic behavior of real networks. Maintaining

consistent network equilibrium requires dynamic and adaptive

control mechanisms. Achieving network balance also extends the

useful life of the current infrastructures by avoiding the need

for continual expensive upgrades. Current capacity and resources

are efficiently utilized to maximize return on investment. Network

equilibrium points are defined with management policies that

drive the traffic management system to deliver stable service

levels. Traffic management policies dynamically balance conflicting

network demands and optimize overall network performance.

... And

to be sane, follow up with ...



A Traffic Management Solution


Effective traffic management requires the close integration
of multiple control and analysis elements, including instrumentation,

bandwidth management, load balancing, and network layer tools.

All of these elements are integrated by the enterprise traffic

policy, which defines how the network should react to changing

conditions.

Policy-based



Policies are the rules, or constraints, placed on the traffic
management system. They define the decision-making criteria

and integrate all traffic management components.

Because

every organization has different requirements, the policy definition

should be flexible, allowing granular control of network traffic.

For comprehensive enterprise management, performance policies

should integrate with a corporation's security policy. Network

equilibrium can only be achieved when traffic is managed across

the entire enterprise, with a single traffic management policy.

This enterprise-wide policy should be centrally managed and

capable of leveraging a global directory service that provides

real-time information on network users and resources.

Centralized

management minimizes administrative burdens since the policies

are defined once and automatically distributed to multiple enforcement

points. Administrators are spared the drudgery of repetitive

configurations and gain the confidence that network performance

is managed coherently with a single policy. Enterprise-wide

policies are also more effective and secure than trying to synchronize

a set of independent management tools.

Furthermore,

policy-based traffic management must support the automatic distribution

of a single policy to multiple enforcement points, typically

all Internet and intranet access points. The enforcement points

provide active implementation of the policy by continually inspecting

traffic and utilizing real-time feedback mechanisms to maintain

network equilibrium. Logging of traffic flows and resource usage

also occurs at all enforcement points. Traffic management policies

must be defined to support dynamic network conditions.

For example,

by anticipating large bursts of discretionary network traffic,

the administrator can establish guarantees that ensure the availability

of bandwidth for important applications.

Traffic

inspection-based



Traffic management requires detailed information on all network
traffic. The various mechanisms which regulate network performance

require comprehensive traffic information in order to make intelligent

decisions consistent with the traffic management policy. Traffic

inspection should not only determine the source and destination

of a network communications, but it should also yield information

on application type, direction, and connection state.

Application

type-Flexible traffic management policies require that traffic

be classified by Internet service or application in order to

deliver the appropriate level of network resources for that

service. With this capability, applications with critical bandwidth

requirements can be granted priority over low priority services.

Direction-When

the traffic management policy applies different control criteria

to inbound and outbound traffic, the ability to identify traffic

direction becomes critical. For example, if an organization

supports electronic commerce, inbound HTTP traffic will typically

require a higher priority than outbound HTTP traffic.

State information-Arguably

the most critical aspect of traffic inspection is the ability

to derive state information from an individual IP packet. Understanding

the state of network traffic is crucial to applying the appropriate

management policy. Discrete packets yield little useful information

because they cannot be associated with an established or newly

requested network connection. State information allows the traffic

management solution to manage each packet in relation to the

entire transmission. Using this state information, traffic management

can be successfully applied to individual network connections.

Instrumentation-based



Network instrumentation provides the raw data for the traffic
management system. This data must then be analyzed to provide

pertinent information on network traffic flows.

With the

proper instrumentation and analysis tools, network administrators

can characterize traffic mix by application, heavy consumers

of network bandwidth, and the variations of traffic. This information

is necessary to establish the desired network equilibrium and

define the appropriate policies. Instrumentation also provides

the ongoing feedback to drive the adjustments that maintain

network equilibrium.

Bandwidth

management-based



Heavy Internet and intranet usage can result in network congestion
at a corporation's network access points. Even at moderate traffic

levels, the desired network equilibrium point can be upset and

the performance and availability of critical network services

can be degraded. Typically, this is a result of incorrectly

assuming that all network traffic has equal priority, which

is most often not the case. Furthermore, chasing the problem

with more bandwidth does not address the root problem, because

traffic will invariably increase to fill the available bandwidth.

The only viable solution is to actively manage bandwidth resources.

Policy-based bandwidth management can alleviate network congestion

by dynamically controlling traffic at all Internet/intranet

access points. The bandwidth policy defines the privileges granted

to specific users and applications.

Bandwidth

management solutions classify inbound and outbound traffic according

to user-defined classes, and then schedule traffic for transmission

based on its relative merit or importance. There are a number

of important points to consider when choosing and deploying

policy-based bandwidth management solutions.

Level of

bandwidth control-Bandwidth management should be provided on

an aggregate level, allowing the network administrator to establish

an equilibrium point that allocates available bandwidth based

on entire classes of traffic, not just individual connections.

For example, guaranteeing a minimum amount of bandwidth for

each HTTP connection will lead to problems if the number of

connections doubles suddenly. The preferred approach is to manage

traffic at an aggregate level that allows the administrator

to define the proportion of available bandwidth granted to all

HTTP connections. When bandwidth is controlled at an aggregate

level, variations in HTTP traffic impact other Web connections,

but bandwidth availability for other traffic classes is unaffected.

Control

criteria-In the past, bandwidth management meant establishing

limits and guarantees. An example of a guarantee is the Committed

Information Rate (CIR) for Frame Relay networking services.

CIR is a minimum bandwidth guarantee that an application or

user can expect to receive.

Limits can

also be placed on the maximum amount of bandwidth that a network

service consumes on a network link. Bandwidth guarantees are

useful for smoothing the burst-and-delay effect inherent in

most Internet traffic. Network users will observe an improved

quality of service due to the allotment of guaranteed bandwidth.

These static

mechanisms alone, however, do not provide a complete bandwidth

management solution for most networks. Weighted priorities are

necessary to support the dynamic traffic mix found in most network

environments. Weighted priorities allocate bandwidth based on

merit or importance in relation to other managed traffic. As

an example, outgoing Web traffic that is sent to satisfy external

requests can, if desired, be deemed twice as important as incoming

FTP traffic. When bandwidth resources are oversubscribed, the

weighted priorities will ensure that the ratio of outgoing Web

traffic to incoming FTP traffic be accurately maintained at

a 2:1 for all available bandwidth resources.

Unlike absolute

priorities, weighted priorities ensure that low priority traffic

is not starved of network bandwidth. Weighted priorities provide

an intuitive method of defining traffic policies and ensure

that even low priority traffic receives some bandwidth on a

consistent basis.

The combination

of weighted priorities, limits, and guarantees offers a new

dimension of flexibility for the network administrator. For

example, a specific Internet service may be assigned a large

weighting indicating a high criticality level. At the same time,

the service may receive a low bandwidth guarantee recognizing

that there is a minimal bandwidth requirement for basic operation.

When bandwidth

management is deployed at a WAN access point it must be able

to support not only all necessary applications, but also the

existing security functions as well. Foremost among these are

data encryption and network address translation. Data encryption

is a fundamental component of Virtual Private Networks (VPNs)

and secures the transmission of data across public networks

such as the Internet. Unless the bandwidth management solution

can intelligently handle encrypted data, it is useless in managing

bandwidth on the large volumes of traffic carried by VPNs.

In many

organizations, the number of users who require access to the

Internet exceeds the number of legal, or registered, IP addresses

assigned to the corporation. Network address translation can

overcome the IP address limitation by translating internal addresses

to one or more registered addresses. This is a very popular

implementation and must be supported by any bandwidth management

solution. Without this support, bandwidth management cannot

be deployed at any WAN access point.

Load-balancing-based





The ability to maintain a user-defined network equilibrium is
dependent on a robust network infrastructure. When a single

application server is relied upon to support a high volume of

client/server traffic, users may experience poor response times

or even connection timeouts. Such unreliable connectivity can

result in missed business opportunities.

Server load

balancing enables a single application server to be replaced

with a logical pool of servers sharing a common IP address.

All application data is replicated so that any individual server

can fulfill client requests. Load balancing permits incoming

connection requests to be shared among all of the available

servers. The deployment of multiple servers eliminates a single

point of failure in a server infrastructure and enhances the

reliability and availability of network resources.

Not only

do users experience noticeably improved response times, but

corporations are spared the expense of continually upgrading

to more expensive servers to meet the increasing demand for

service. Existing hardware can be utilized to increase the capacity

and robustness of a corporation's server infrastructure.

Flexible

load balancing solutions provide multiple balancing algorithms

to meet the specific requirements of an organization. For example,

algorithms are available that distribute connection attempts

to the server experiencing the lightest load. This method evenly

balances the load on all servers in the group.

To support

enterprise networks where network users are geographically dispersed,

incoming traffic can be directed to the closest server based

on domain name. This enhances response times for end users.

Other load balancing algorithms enable connection attempts to

be distributed to individual servers based on round trip delays,

round robin schemes, or random server assignment.

Server infrastructures

can be enhanced with load balancing to help corporations achieve

an optimal network equilibrium point.

... Finally,

you can look at these too.



Network-layer Management Tools


Managing traffic flows at the network layer offers several opportunities
to enhance overall network performance. Traffic can be inspected

at the network layer to extract complete state information and

provide optimal performance. Network-layer traffic management

also provides the flexibility to support a broad range of applications,

including compression and caching.

Network

Compression



Data compression can be performed at the network layer to reduce
the raw volume of data, thus improving performance and better

utilizing network resources. The key to data compression is

selecting efficient algorithms which introduce minimal latency.

Network

Caching



Network-layer caching increases performance by making frequently
requested information available as a local network resource.

Time consuming transactions between the client and the content

server are minimized reducing traffic flows at possible points

of network congestion.



For example, an administrator can cache multiple pages of a
remote Web server that is accessed frequently. Users experience

faster, smoother response time and bandwidth is conserved for

other activities.

Enterprise

traffic management is becoming an increasingly important issue,

especially as more and more corporations build Internet and

related technologies into their core business processes. With

the rapid development and adoption of new applications that

require large amounts of bandwidth, corporations must ensure

that they protect the performance of their business-critical

applications, whether they be client/server applications such

as Oracle or SAP, in-house developed applications, or Web commerce

applications. To do this, each corporation must evaluate its

traffic management requirements and implement an effective enterprise

traffic management solution that is flexible, centrally managed,

and provides the performance and access that customers and employees

need.

This

is based on a white paper on enterprise traffic management by





John McConnell, president, McConnell Consulting Inc.


(extracted from a white paper


written by the author)