Posted: September 22nd, 2008 | Author: TnT Admin | Filed under: Concepts | Tags: network, traceroute | No Comments »
The program was written by Van Jacobson and others. It is based on a clever use of the Time-To-Live (TTL) field in the IP packet’s header. The TTL field is used to limit the life of a packet. When a router fails or is mis-configured, a routing loop or circular path may result. The TTL field prevents packets from remaining on a network indefinitely should such a routing loop occurs. A packet’s TTL field is decremented each time the packet crosses a router on its way through a network. When its value reaches 0, the packet is discarded rather forwarded. When discarded, the ICMP TIME_EXCEEDED message is sent back to the packet’s source to inform the source that the packet was discarded. By manipulating the TTL field original packet, the program traceroute uses information from these ICMP messages to discover paths through a network. Read the rest of this entry »
Posted: September 13th, 2008 | Author: TnT Admin | Filed under: Analyze | Tags: Bottleneck, network | No Comments »
At the network level, many things can affect performance. The bandwidth (the amount of data that can be carried by the network) tends to be the first culprit checked. Assuming you have determined that bad performance is attributable to the network component of an application, there is more likely cause of bad network performance than network bandwidth. The most likely cause of network performance is the application itself and how it is handling distributed data and functionality. Read the rest of this entry »
Posted: July 6th, 2008 | Author: TnT Admin | Filed under: Concepts | Tags: network | No Comments »
Let’s understand a little bit of network 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 propagations time or propagations delay. Propagation time is determined by the type of media used and the distance involved. Read the rest of this entry »
Posted: June 7th, 2008 | Author: TnT Admin | Filed under: How-Tos | Tags: network, Ping | 1 Comment »
To isolate network problems with ping, follow the steps listed which actually starts from the loopback interface, IP address, name resolution, router connectivity, traceroute to remote machines. You will need to run the ping command repeatedly, changing your destination address so that you work your way through each intermediate device to your destination. Read the rest of this entry »
Posted: June 4th, 2008 | Author: TnT Admin | Filed under: Concepts | Tags: network, Ping | No Comments »
One network device sends a request for a reply to another device and records the time the request was sent. The device receiving the request sends a packet back. When the reply is received, the round-trip time for packet propagation can be calculated. The receipt of a reply indicates a working connection. This elapsed time provides an indication of the length of the path. Consistency among repeated queries gives an indication of the quality of the connection. With the above in mind, ping answers two basic questions: “one, do I have a connection?” Two, “how good is that connection?” Read the rest of this entry »