Linux O.S. ( 25 Sep. 2012 )

There are three default permission levels in linx

user / creator level                              u

group level                                          g

others level                                         o

collectively these are denoted with      a   

there are three permission types in linux

read                       r

write                     w

execute                               x

+             sign stands for assign the following & doesn’t effect other permission

And    -   sign deassign or deduct and doesn’t effect other permissions

=    sign makes permission equal / same as following

How to edit access permission

Chmod u+r file/foldername

Group read permission granted and other deassign read permission       Chmod g+x,o-r file/foldername

Chmod go+r file/foldername

Chmod a+rx file/foldername

Chmod a=rx file/foldername

To get all permission deassign from al users                                         Chmod a-rwx file/foldername

To change permission of main folder as well sub folders                                Chmod –R u-r,o+x file/foldername

To assign permission from numeric

0              -              -              -

1              -              -              x

2              -              w            -

3              -              w            x

4              r              -              -

5              r              -              x

6              r              w            -

7              r              w            x

Chmod 402 file/foldername

In above command first no 4 is for user 0 for group and 2 for other’s permission

click on below links for further study on linux permission levels

Click here for Link1

Click here for Link 2

Click here for Link 3

Click here for Link 4 



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Network Design and management ( 25 Sep. 2012 )

 

Static routing was discussed in detail

different commands for assigning ip address manually was discussed    

A lab was done on packet tracer with 3 routers and 2 computers

 

Types of routing

Static routing

                  Static routing is a concept describing one way of configuring path selection of routers in computer networks. It is the type of routing characterized by the absence of communication between routers regarding the current topology of the network.^[1] This is achieved by manually adding routes to the routing table. The opposite of static routing is dynamic routing, sometimes also referred to as adaptive routing.
In these systems, routes through a data network are described by fixed paths (statically). These routes are usually entered into the router by the system administrator. An entire network can be configured using static routes, but this type of configuration is not fault tolerant. When there is a change in the network or a failure occurs between two statically defined nodes, traffic will not be rerouted. This means that anything that wishes to take an affected path will either have to wait for the failure to be repaired or the static route to be updated by the administrator before restarting its journey. Most requests will time out (ultimately failing) before these repairs can be made. There are, however, times when static routes can improve the performance of a network. Some of these include stub networks and default routes.
Dynamic Routing
Dynamic routing protocols are supported by software applications running on the routing device (the router) which dynamically learn network destinations and how to get to them and also advertise those destinations to other routers. This advertisement function allows all the routers to learn about all the destination networks that exist and how to to those networks.
A router using dynamic routing will 'learn' the routes to all networks that are directly connected to the device. Next, the router will learn routes from other routers that run the same routing protocol (RIP, RIP2, EIGRP, OSPF, IS-IS, BGP etc). Each router will then sort through it's list of routes and select one or more 'best' routes for each network destination the router knows or has learned.
Dynamic routing protocols will then distribute this 'best route' information to other routers running the same routing protocol, thereby extending the information on what networks exist and can be reached. This gives dynamic routing protocols the ability to adapt to logical network topology changes, equipment failures or network outages 'on the fly'.





Ping command is icmp packet or echo signal

B.P. ( 25 Sep. 2012 )

Different models for modeling were discussed


Sir told students to draw map to your home from uni to practice model designing


Bottle neck are the hurdles you face during modeling


1. As is model
2. To be model


SIPOC
      Supplier input process output customer
this model is assignment for tomorrow