My Netwok Dictionary

This article explains how OSPF algorithm uses the shortest path to determine the best route to a destination. In this algorithm, the best route is the least cost. The algorithm was developed by Dijkstra, a Dutch computer specialist in 1959.

The algorithm considers the network as a set of nodes connected by point to point links. Each link has a cost. Each node has a name. Each node has a comprehensive database of all links and therefore knows the physical topology information in its entirety. All database link-state within a given area are identical. Read the rest of this entry »

The services actually provided to users via the Internet is not defined by the routing mechanisms of transmission control protocol/Internet protocol (TCP IP) but on the contrary, application protocols high level, for example hypertext transport protocol (HTTP), the file transfer protocol (FTP), network news transfer protocol (NNTP) and simple mail transfer protocol (SMTP).

Since these protocols are not incorporated into the Internet itself, it is possible to use a new protocol to the application layer consists only of a server to transmit the protocol data in the appropriate format and a client to receive and interpret such data. However, the usefulness of a service to users increases with the number of servers that service. Read the rest of this entry »

The IPX nodes with more than one IPX interface have a combination of network address / node unique for each one of its interfaces. To connect to a node so you can use any combination of this network address/node.

When SAP announced a service, it provides network/node associated with the service address. In the nodes with multiple interfaces, this means you must choose one of the interfaces as it will spread; this is the function of the primary interface flag we talked about earlier. Read the rest of this entry »

Router LED:

Cisco routers use LED indicators to provide status information. LED indicators vary by model of Cisco router. Interface LED indicates the activity of the corresponding interface. If an LED is off when the interface is active and the interface is properly connected, can signal a problem. If the interface is very active, the LED is continuously lit. The green OK LED to the right of the AUX port is turned on after the system was initialized properly.

Review of initial startup of router:

The information and messages displayed during initial startup. This information varies, depending on the router interfaces and Cisco IOS software version. The screens shown in this chart are for reference only and may not reflect exactly what the screen displays on the console. Read the rest of this entry »

This article presents the OSPF protocol. OSPF is a link-state routing protocol based on open standards. It described in various standards of the Internet Engineering Task Force (IETF). The term “free” in “First Open Shortest Path” means that it is open to the public and is not owned by any company.

Compared with RIP v1 and v2, OSPF is preferred because it is scalable IGP. RIP is limited to 15 hops, it converges slowly and sometimes slow routes chosen because it ignores critical factors such as bandwidth to determining the route. OSPF has overcome these limitations and has become a robust and scalable routing protocol and suitable for modern networks. Read the rest of this entry »

Dial-on-demand routing (DDR) is triggered when traffic is directed to previously defined features out of a DDR-enabled interface. At the traffic triggers a call of DDR is known as interesting traffic. Once the router forwarded by interesting traffic call is interrupted.

The key to efficient operation of DDR is in the definition of interesting traffic. Interesting traffic is defined by dialer-list command. The dial lists can establish that all traffic from a specific protocol DDR activate a link, or you can access a list to determine which types of traffic can activate the link. The dial lists do not filter traffic on an interface. Even a non-interesting traffic will be forwarded if the connection to the destination is active. Read the rest of this entry »

There are many ways to classify the networks, namely in terms of its logical topology (point to point or broadcast), physical topology (radial, bus, and ring), according to the transmission medium (wired, wireless, fixed, mobile); speed transmission protocol, etc.

Internet is often classified as a packet switched network. According to this classification there are three basic types of networks: circuit switched (e.g., telephone networks) connection-oriented packet-switching (such as examples include the X.25 and X.75) and packet switching.

On the other hand, Internet can also be classified as a separate logical architecture of the particular characteristics of the network that connects different types of networks so that computers and people to communicate without doing so may need to know what network are using or how to route the information. Read the rest of this entry »

A protocol is a set of rules for communication between devices (e.g. computers, phones, routers, switches, etc). The protocols governing the format, timing, sequencing and error control. Without these rules, the devices could not detect the arrival of bits.

But the protocols go beyond just basic communication. Suppose you want to send a file from one computer to another. You could send the whole file at once. Unfortunately, it could stop the other users who are using the LAN during the time it takes to send the file. Additionally, if an error occurs during transmission, the entire file would be sent again. To resolve these problems, the file is broken into small pieces called “packets” grouped a certain way.

This means that certain information must be added to the package to tell the receiver where each group belongs in relation to others, but this is a minor issue. To improve the reliability of the information, synchronization and correction must be added the famous package. A useful information (i.e. the message), along with additional information is called a protocol. Read the rest of this entry »

The PAP, which is used by many Internet Service Providers (ISP), basically works the same way as the normal login procedure. The client authenticates itself by sending a username and password (optionally encrypted) to the server, which is compared by the server with its database of keys / secrets. This technique is vulnerable to intruders who may try to get the password listening on a serial line and others who make repeated attempts to attack by trial and error.

The CHAP does not have these defects. With CHAP, the authenticator (i.e. the server) sends a string of “challenge” to the client randomly generated, along with its computer name. The client uses the computer name to find the appropriate key, combines it with the challenge, and encrypts the string using an encryption function of a single sense. The result is returned to the server along with the name of the client computer. The server now performs the same computation, and warns the customer if you get the same result. Read the rest of this entry »

The Dynamic Host Configuration Protocol (DHCP) works in client/server. DHCP enables DHCP clients obtain their IP network settings from a DHCP server. It’s less work to manage an IP when using DHCP.

The configuration option more significant that the client receives from the server is your IP address. The DHCP protocol is described in RFC 2131. A DHCP client is included in most modern operating systems, including various Windows operating systems, Novell Netware, Sun Solaris, Linux and Mac OS.

When the client requests the DHCP server on network addressing values, this server manages the allocation of IP addresses and responds to configuration requests from customers. The DHCP server can respond to requests from many subnets. DHCP is not intended to configuring routers, switches and servers. These types of hosts need to have static IP addresses. Read the rest of this entry »