18/04/10 - 25/04/10

Jumat, 23 April 2010

The Application Layer

The Application layer of the OSI model marks the spot where users actually communicate to the computer. This layer only comes into play when it’s apparent that access to the network is going to be needed soon. Take the case of Internet Explorer (IE). You could uninstall every trace of networking components from a system, such as TCP/IP, NIC card, and so on, and you could still use IE to view a local HTML document—no problem. But things would definitely get messy if you tried to do something like view an HTML document that must be retrieved using HTTP or nab a file with FTP or TFTP. That’s because IE will respond to requests such as those by attempting to access the Application layer. And what’s happening is that the Application layer is acting as an interface between the actual application program—which isn’t at all a part of the layered structure—and the next layer down by providing ways for the application to send information down through the protocol stack. In other words, IE doesn’t truly reside within the Application layer—it interfaces with Application layer protocols when it needs to deal with remote resources.

The OSI Reference Model

One of the greatest functions of the OSI specifications is to assist in data transfer between disparate hosts—meaning, for example, that they enable us to transfer data between a Unix host
and a PC or a Mac.

The OSI isn’t a physical model, though. Rather, it’s a set of guidelines that application developers can use to create and implement applications that run on a network. It also provides aframework for creating and implementing networking standards, devices, and internetworking schemes.

Models Networking

When networks first came into being, computers could typically communicate only with computers from the same manufacturer. For example, companies ran either a complete DECnet solution or an IBM solution—not both together. In the late 1970s, the Open Systems Interconnection (OSI) reference model was created by the International Organization for Standardization (ISO) to break this barrier.

The OSI model was meant to help vendors create interoperable network devices and software in the form of protocols so that different vendor networks could work with each other. Like world peace, it’ll probably never happen completely, but it’s still a great goal. The OSI model is the primary architectural model for networks. It describes how data and network information are communicated from an application on one computer through the network media to an application on another computer. The OSI reference model breaks this approach into layers.

Networking Basics

Before we explore internetworking models and the specifications of the OSI reference model, you’ve got to understand the big picture and learn the answer to the key question, Why is it so important to learn Cisco internetworking?

Networks and networking have grown exponentially over the last 15 years—understandably so. They’ve had to evolve at light speed just to keep up with huge increases in basic missioncritical user needs such as sharing data and printers as well as more advanced demands such as videoconferencing. Unless everyone who needs to share network resources is located in the same office area (an increasingly uncommon situation), the challenge is to connect the sometimes many relevant networks together so all users can share the networks’ wealth.

Configuring VLANs on Cisco Catalyst Switches and Routers

The steps in the Catalyst 1924 Switch:

Switch#config t
Switch(config)#vlan 10
Switch(config)#vlan 20
Switch(config)#interface e0/1
Switch(config-fi)#vlan-membership static 10
Switch(config-if)#interface e0/2
Switch(config-if)#vlan-membership static 10
Switch(config-if)#interface e0/4

Link Collection Super Complete Cisco Certifications (CCNA, CCNP, CCIE etc.)

I tried to collect the download link for the friends who are or want to take a certification from Cisco Systems network. I took all the links from trusted sources is guaranteed accurate. Below are Links that you can download directly via Rapidshare. Check it out!

CNA : 640-822 ICND1 Interconnecting Cisco Networking Devices Part 1 v1.0

CCNA : 640-816 ICND2 Interconnecting Cisco Networking Devices Part 2 v1.0
OR
CCNA : 640-802
ELSE
CCENT : 640-822 ICND1 Interconnecting Cisco Networking Devices Part 1 v1.0

Access Control Lists (ACLs)

ACL is simply used to allow or not the package from the hosts toward a particular goal. ACL consisted of rules and conditions that determine the network traffic and determines whether the router will process the packet will be passed or not. This module will explain the standards and the extended ACL, ACL placement and some applications of the use of ACL.

ACL is a list of conditions used to test the network that tries trfaik through a router interface. These lists tell the router where packets will be accepted or rejected. Acceptance and rejection based on certain conditions.

To filter traffic jaringa, ACL determines if the packet is passed or blocked at router interfaces. Router ACL to make decisions based on source address, destination address, protocol, and port number.

Routing and routing protocols

Routing is the process whereby a router to forward packets to the destination network. A router makes decisions based on the IP address that is addressed by the package. All routers use the destination IP address to send packets. In order routing decisions are correct, the router must learn how to achieve goals. When routers use dynamic routing, information learned from other routers. When using static routing, a network administrator to configure the information on the network you want to target manually.

If static routing is used, then the configuration must be performed manually, the network administrator must insert or remove a static route in case of topology changes. On a large scale network, if still using static routing, it will be a huge waste of time network administrators to update its routing table. Therefore, static routing is only possible for small-scale networks. While the bias is applied in dynamic routing of large scale network and requires more skills than administrators.

WAN and Router

Wide Area Network (WAN) is a data communications network that connects users in a network that is in a large geographic area. WAN has several important characteristics that differentiate it from the LAN. In the first lesson in this module will discuss the introduction of WAN technologies and protocols. And will also explain how the similarities and differences between the WAN and LAN.

It is very important to understand the physical layer components in a router. This knowledge base will add the information and capabilities that will be required to configure the router and set the routing network. This module also describes the technique of the physical connection of the various interfaces.

WAN is a data communications network, spread on a large geographic area like a province or country. WAN always uses transmission facilities provided by telecommunications companies such as telephone service company.