Network OS (M6.5)

An Operating System(O.S.) is a System software that manages the hardware resources and provides services to the Application software. There are many types of operating systems depending upon its features and functionalities. They can be Batch O.S., Multitasking O.S., Multiprocessing O.S., Network O.S., Hybrid O.S., etc.

Network OS

Network Operating System is a computer operating system that facilitates to connect and communicate various autonomous computers over a network.

• The Network O.S. mainly runs on a powerful computer, that runs the server program. 
• It facilitates the security and capability of managing the data, user, group, application, and other network functionalities. 
• The main advantage of using a network o.s. is that it facilitates the sharing of resources and memory amongst the autonomous computers in the network. 
• It can also facilitate the client computers to access the shared memory and resources administered by the Server computer. 
• In other words, the Network O.S. is mainly designed to allow multiple users to share files and resources over the network. 
• The Network O.S. is not transparent in nature. The workstations connected in the network are aware of the multiplicity of the network devices. 
• The Network Operating Systems can distribute their tasks and functions amongst connected nodes in the network, which enhances the system overall performance. 
• It can allow multiple access to the shared resources concurrently, which results in efficiency. 
• One of the major importance of using a Network O.S. is remote access. 
• It facilitates one workstation to connect and communicate with another workstation in a secure manner. 
• For providing security, it has authentication and access control functionality. 
• The network o.s. implements a lot of protocols over the network, which provides a proper implementation of the network functionalities. 
• One drawback of Network O.S. is its tightly coupled nature in the network.

Some examples of Network O.S. are Novel Netware, Microsoft Windows server (2000, 2003, 2008), Unix, Linux, etc.

There are mainly two types of Network O.S., they are:

1. Peer-to-Peer Network Operating System is an operating system in which all the nodes are functionally and operationally equal to each other.
2. Client-Server Networking Operating System operates with a single server and multiple client computers in the network.

 For More Details

Examples

1.Novel Netware, 

2.Linux

3.Windows 2000

4.Macintosh OS

Device Discovery and Mapping & Troubleshooting Strategies(M6.3)

Device Discovery and Mapping

#Troubleshooting Versus Management

In a very real sense, troubleshooting and management
are just different sides of the same coin. Ideally, management deals with problems
before they happen, while troubleshooting deals with problems after the fact. 

#Characteristics of Management Software

• Discovery and mapping 

Discovery includes both the automatic detection of all devices on a network and the collection of basic information about each device, such as the type of each device, its MAC address and IP address, the type of software being used, and, possibly, the services it provides. Mapping is the creation of a graphical representation of the network showing individual interconnections as well as  overall topology.

• Event monitoring

Once a picture of the network has been created, each device may be monitored to ensure continuous operation. This can be done passively, by waiting for the device to send an update or alert, or by actively polling the device.

• Remote configuration

You should be able to connect to each device and then examine and change its configuration. It should also be possible to collectively track configuration information, such as which IP addresses are in use.

• Metering and performance management

Information on resource utilization should be collected. Ideally, this information should be available in a usable form for purposes such as trend analysis and capacity planning.

• Software management

Being able to install and configure software remotely is rapidly becoming a necessity in larger organizations. Being able to track licensing can be essential to avoid legal problems. Version management is also important.

• Security and accounting

Depending on the sensitivity of data, the organization’s business model, and access and billing policies, it may be necessary to control or track who is using what on the network.

#Discovery and Mapping Tools

A wide range of tools is available. At the low end are point tools—tools designed to deal with specific tasks or closely related tasks.

#Selecting a Product

#Device Discovery

-IP Address Management

-nmap

-arpwatch

#Device Identification

-Stack Fingerprinting

-queso

-nmap Revisited

#Scripts

-Tcl/Tk and scotty

#Mapping or Diagramming

-tkined

Connectivity Testing & Packet Capture(M6.2)

 Connectivity Testing

Cabling

Software Testing with Ping

Path Characteristics

Path characteristics deals with investigating a paths behavior and performance.

Path Discovery with traceroute

Traceroute, a tool used to discover the links along a path. While this is the first step in investigating a path’s behavior and performance, it is useful for other tasks as well.

Path discovery is also an essential step in diagnosing routing problems. 

While you may fully understand the structure of your network and know what path you want your packets to take through your network, knowing the path your packets actually take is essential information and may come as a surprise.

Once packets leave your network, you have almost no control over the path they actually take to their destination. You may know very little about the structure of adjacent networks. Path discovery can provide a way to discover who their ISP is, how your ISP is connected to the world, and other information such as peering arrangements. traceroute is the tool of choice for collecting this kind of information. 

#Options
Two options control how much information is printed. Name resolution can be disabled with the -n option. This can be useful if name resolution fails for some reason or if you just don’t want to wait on it. The -v option is the verbose flag. With this flag set, the source and packet sizes of the probes will be reported for each packet. If other ICMP messages are received, they will also be reported, so this can be an important option when troubleshooting.
Several options may be used to alter the behavior of traceroute.

#Complications with traceroute
The information traceroute supplies has its limitations. In some situations, the results returned by traceroute have a very short shelf life. This is particularly true for long paths crossing several networks and ISPs. 

Path Performance

Once you have a picture of the path your traffic is taking, the next step in testing is to get some basic performance numbers. Evaluating path performance will mean doing three types of measurements. 

Bandwidth measurements will give you an idea of the hardware capabilities of your network, such as the maximum capacity of your network. 

Throughput measurements will help you discover what capacity your network provides in practice, i.e., how much of the maximum is actually available. 

Traffic measurements will give you an idea of how the capacity is being used.

#Performance Measurements

Two factors determine how long it takes to send a packet or frame across a single
link. The amount of time it takes to put the signal onto the cable is known as the
transmission time or transmission delay. This will depend on the transmission rate
(or interface speed) and the size of the frame. The amount of time it takes for the
signal to travel across the cable is known as the propagation time or propagation
delay. Propagation time is determined by the type of media used and the distance
involved.

Once we move to multihop paths, a third consideration enters the picture—the
delay introduced from processing packets at intermediate devices such as routers
and switches. This is usually called the queuing delay.

#Bandwidth Measurements

Bandwidth really measures the capabilities of our hardware. If bandwidth is not adequate, you will need to reexamine your equipment.

ping revisited

pathchar

bing

Packet pair software

#Throughput Measurements

Throughput is typically measured by timing the transfer of a large block of data.
This may be called the bulk transfer capacity of the link.

Poor throughput can result not only from inadequate hardware but also from
architectural issues such as network design. For example, a broadcast domain that
is too large will create problems despite otherwise adequate hardware. The solu-
tion is to redesign your network, breaking apart or segmenting such domains once
you have a clear understanding of traffic patterns.

ttcp - One of the oldest bulk capacity measurement tools is ttcp.

netperf

iperf

Other related tools

You may also want to consider several similar or related tools. treno uses a
traceroute-like approach to calculate bulk capacity, path MTU, and minimum RTP.

treno is part of a larger Internet traffic measurement project at NLANR. treno
servers are scattered across the Internet. 

In general, netperf, iperf, and treno offer a wider range of features, but ttcp is gen-
erally easier to find.

#Traffic Measurements with netstat

There are three basic approaches you can take. 

First, the quickest way to get a summary of the activity on a link is to use a tool such as netstat. Or you can use packet capture to look at traffic. Finally, you could use SNMP-based tools like ntop. 

Troubleshooting and Management & Host Configurations(M6.1)

• The first step in diagnosing a network problem is to collect information. This includes collecting information from your users as to the nature of the problems they are having, and it includes collecting data from your network. 

• Your success will depend, in large part, on your efficiency in collecting this information and on the quality of the information you collect. There is an extraordinary variety of tools available for this purpose, and more  become available daily.

• A small number of tools can be used to solve most problems.

General Approaches to Troubleshooting

• Troubleshooting is a complex process that is best learned through experience.

• Network troubleshooting is the collective measures and processes used to identify, diagnose and resolve problems and issues within a computer network.

• It is a systematic process that aims to resolve problems and restore normal network operations within the network.

• Network troubleshooting is primarily done by network engineers or administrators to repair or optimize a network. 

• It is generally done to recover and establish network or Internet connections on end nodes/devices.

Some of the processes within network troubleshooting include but are not limited to:

• Finding and resolving problems and establishing Internet/network connection of a computer/device/node

• Configuring a router, switch or any network management device

• Installing cables or Wi-Fi devices

• Updating firmware devices on router switch

• Removing viruses

• Adding, configuring and reinstalling a network printer

Network troubleshooting can be a manual or automated task. When using automated tools, network management can be done using network diagnostic software.

Network documentation is important for the following reasons:

• Proper documentation can save you from time-consuming research to fix recurring problems.

• When everything is in place and everybody follows the same processes and procedures, consistency across the network helps to reduce problems and errors.

• You won’t lose important information when a knowledgeable employee leaves the company.

• The documentation helps you to onboard new hires much more quickly.

• You can troubleshoot your network faster when issues come up.

Troubleshooting and Management

Documentation

Network documentation is a technical record of the hardware, software, servers, directory structure, user profiles, data, and how it all works together.

Network documents should include any information that helps administrators and IT professionals to keep the network up and running smoothly. This information can be in any format you want.

The most important source of information is the local documentation created by you or your predecessor, & There are a couple of sets of standard documentation.

The documentation can be divided into two general categories

• Configuration documentation

• Process documentation

Configuration documentation statically describes a system. It assumes that the steps involved in setting up the system are well understood and need no further comments, i.e., that configuration information is sufficient to reconfigure or reconstruct the system. This kind of information can usually be collected at any time.

Process documentation describes the steps involved in setting up a device, installing software, or resolving a problem. As such, it is best written while you are doing the task. This creates a different set of collection problems. Here the stress from the task at hand often prevents you from documenting the process.

Management Practices

• A fundamental assumption is that troubleshooting should be proactive. 

• It is preferable to avoid a problem than have to correct it.

• Proper management practices can help.

• Management practices will determine what you can do and how you do it. 

• This is true both for avoiding problems and for dealing with problems that can’t be avoided. 

Some of the more important management issues

1. Professionalism 

To effectively administer a system requires a high degree of professionalism. This includes personal honesty and ethical behavior. Everything you do should be done from the perspective of a cost benefit trade-off. It is too easy to get caught in the trap of doing some- thing “the right way” at a higher cost than the benefits justify. Performance analysis is the key element.

2. Ego management

The most obvious way an administrator may do this is hide what he actually does and how his system works. This can be done many ways. Failing to document the system is one approach— leaving comments out of code or configuration files is common. The goal of such
an administrator is to make sure he is the only one who truly understands the system. He may try to limit others access to a system by restricting accounts or access to passwords.

3. Legal and ethical considerations

From the perspective of tools, you must ensure that you use tools in a manner that conforms not just to the policies of your organization, but to all applicable laws as well. Packet capture software is a prime example. It allows you to examine every packet  that travels across a link, including applications data and each and every header. Unless data is encrypted, it can be decoded. This means that passwords can be captured and email can be read. For this reason alone, you should be very circumspect in how you use such tools.

4. Economic considerations
Solutions to problems have economic consequences, so you must understand the economic implications of what you do. Knowing how to balance the cost of the time used to repair a system against the cost of replacing a system is an obvious example. Cost management is a more general issue that has important implications when dealing with failures. One particularly difficult task for many system administrators is to come to terms with the economics of networking.