November 3rd, 2009 by Bob
The internet layer of the TCP/IP networking model, primarily defined by the Internet Protocol (IP), works much like the postal service. IP defines addresses so that each host computer can have a different IP address, just as the postal service defines addressing that allows unique addresses for each house, apartment, and business. Similarly, IP defines the process of routing so that devices called routers can choose where to send packets of data so that they are delivered to the correct destination.
IP defines logical addresses, called IP addresses, which allow each TCP/IP-speaking device (called IP hosts) to have an address with which to communicate. IP also defines routing, the process of how a router should forward, or route, packets of data.
All the CCNA exams cover IP fairly deeply. For the ICND1 exam, this book’s Chapter 5 covers more of the basics, with Chapters 11 through 15 covering IP in much more detail.
Next up is the Network Access Layer…
Tags: CCENT, CCNA, IP, TCP/IP
Posted in Certification, ICND1, Networking | No Comments »
October 27th, 2009 by Bob
The TCP/IP transport layer consists of two main protocol options:
the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).
TCP/IP needs a mechanism to guarantee delivery of data across a network and the transport layer handles this. In short the transport layer provides a service to the layer above it, the application layer.
The benefits of TCP error recovery cannot be seen unless the data is lost. Let’s say Bob’s web browser was to request information from Larry’s server, if either transmission were lost (Bob’s request to Larry or Larry’s response to Bob), HTTP would not take any direct action, but TCP would resend the data and ensure that it was received successfully.
In the above example demonstrates a function called adjacent-layer interaction, which defines the concepts of how adjacent layers in a networking model, on the same computer, work together. The
higher-layer protocol (HTTP) needs to do something it cannot do (error recovery). So, the higher layer asks for the next lower-layer protocol (TCP) to perform the service, and the next lower layer performs the service. The lower layer provides a service to the layer above it.
| Concept |
Description |
| Same-layer interaction on different computers |
The two computers use a protocol to communicate with the same layer on another computer. The protocol defined by each layer uses a header that is transmitted between the computers, to communicate what each computer wants to do. |
| Adjacent-layer interaction on the same computer |
On a single computer, one layer provides a service to a higher layer. The software or hardware that implements the higher layer request that the next lower layer perform the needed function. |
Tags: CCENT, CCNA, ICND1, Networking, TCP/IP, Transport Layer
Posted in Certification, ICND1, Networking | No Comments »
August 12th, 2008 by Bob
Here is a list of the more common command-line utilities that you should find useful while trouble shooting your network.
TCP/IP Command-Line Tolls
| Command |
Description |
| IPCONFIG |
Displays the basic local host configuratioon – IP address,the subnet address, the subnet mask and default gateway. |
| PING |
Sends a test packet to a specified address.If all is well, it will return. Use the loopback address (127.0.0.1) to test the IP architecture and configuration. |
| ARP |
Used to see the entries in the Address Resolution table. |
| ROUTE |
Use to see the local routing table and to add entries to it. Use ROUTE PRINT to display contents, ROUTE ADD to add entries and ROUTE DELETE to remove entries. |
| NBSTAT |
Used to check the resolutions of NetBIOS names to TCP/IP addresses. |
| NETSTAT |
Used to check the status of current IP connections. |
| TRACERT |
Used to verify the route to a remote host, |
| NSLOOKUP |
Used to verify entries on a DNS derver. |
Tags: command-line utilities, network, TCP/IP, Utilities
Posted in Everything Else, Networking, Utilities | No Comments »
