| Ping is a utility used to test connectivity and to | | | | Reply from Pathways-WAN-PC32: bytes=32 |
| measure round trip delay between network | | | | time<40ms TTL=128 |
| devices. Ping works by sending an ICMP | | | | Reply from Pathways-WAN-PC32: bytes=32 |
| echo-request packet to the destination and | | | | time<40ms TTL=128 |
| expects an ICMP echo-reply in return. The time | | | | Reply from Pathways-WAN-PC32: bytes=32 |
| taken for this process to occur is recorded and | | | | time<285ms TTL=128 |
| displayed on the output screen. The following are | | | | Reply from Pathways-WAN-PC32: bytes=32 |
| some examples of how the timer is affected | | | | time<40ms TTL=128 |
| under different network conditions. | | | | Ping statistics for Pathways-WAN-PC32: |
| Test #1. Ping across a vast distance | | | | Packets: Sent = 4, Received = 4, Lost = 0 |
| C:\it-pathways.com>ping satellite-hop | | | | (0% loss), |
| Pinging satellite-hop with 32 bytes of data: | | | | Approximate round trip times in milli-seconds: |
| Reply from satellite-hop: bytes=32 time<765ms | | | | Minimum = 40ms, Maximum = 285ms, |
| TTL=128 | | | | Average = 101ms |
| Reply from satellite-hop: bytes=32 time<760ms | | | | Discussion: This computer is some distance away |
| TTL=128 | | | | and the results are consistent with our latency |
| Reply from satellite-hop: bytes=32 time<765ms | | | | expectations of a WAN. The third response |
| TTL=128 | | | | shows a large increase in latency. This may be a |
| Reply from satellite-hop: bytes=32 time<765ms | | | | sign of congestion. |
| TTL=128 | | | | Test #4. Terrible Ping response from another PC |
| Ping statistics for satellite-hop: | | | | across the WAN |
| Packets: Sent = 4, Received = 4, Lost = 0 | | | | C:\it-pathways.com>ping Pathways-WAN-PC47 |
| (0% loss), | | | | Pinging Pathways-WAN-PC47 with 32 bytes of |
| Approximate round trip times in milli-seconds: | | | | data: |
| Minimum = 760ms, Maximum = 765ms, | | | | Reply from Pathways-WAN-PC47: bytes=32 |
| Average = 764ms | | | | time<3005ms TTL=128 |
| Discussion: Studies suggest that the human ear | | | | Request timed out. |
| can begin to notice delays 125ms or greater. | | | | Reply from Pathways-WAN-PC47: bytes=32 |
| Needless to say, if we tried to use any real-time | | | | time<2950ms TTL=128 |
| applications across the link on Test #1 we would | | | | Reply from Pathways-WAN-PC47: bytes=32 |
| not have a positive experience because the | | | | time<3852ms TTL=128 |
| delays have been recorded at 764 milli-seconds | | | | Ping statistics for Pathways-WAN-PC47: |
| on average. One point of note, this is a rare | | | | Packets: Sent = 4, Received = 3, Lost = 1 |
| example where high delay is not caused by a | | | | (25% loss), |
| busy network. This is simply a case where the | | | | Approximate round trip times in milli-seconds: |
| packet has to travel really, really far and it takes | | | | Minimum = 2950ms, Maximum = 3852ms, |
| a lot of time to do so. | | | | Average = 3269ms |
| Test #2. Ping another PC in the same office | | | | Discussion: Windows Ping times out at 4000ms (4 |
| C:\it-pathways.com>ping Pathways-PC1643 | | | | seconds) by default so the timed out request |
| Pinging Pathways-PC1643 with 32 bytes of data: | | | | may just be that the reply did not arrive in time |
| Reply from Pathways-PC1643: bytes=32 | | | | (as opposed to the packet being lost). This type |
| time<2ms TTL=128 | | | | of high latency plays havoc with the TCP |
| Reply from Pathways-PC1643: bytes=32 | | | | retransmission delay timers, the last thing you |
| time<1ms TTL=128 | | | | would want on this network is a lost packet. TCP |
| Reply from Pathways-PC1643: bytes=32 | | | | Performance would be highly impacted. |
| time<1ms TTL=128 | | | | Test #5. No ping response |
| Reply from Pathways-PC1643: bytes=32 | | | | C:\it-pathways.com>ping Pathways-PC947 |
| time<1ms TTL=128 | | | | Pinging Pathways-PC947 with 32 bytes of data: |
| Ping statistics for Pathways-PC1643: | | | | Request timed out. |
| Packets: Sent = 4, Received = 4, Lost = 0 | | | | Request timed out. |
| (0% loss), | | | | Request timed out. |
| Approximate round trip times in milli-seconds: | | | | Request timed out. |
| Minimum = 1ms, Maximum = 2ms, Average | | | | Ping statistics for Pathways-PC947: |
| = 1ms | | | | Packets: Sent = 4, Received = 0, Lost = 4 |
| Discussion: This is about as good as it will get. The | | | | (100% loss), |
| initial 2ms delay may have been due to an arp | | | | Discussion: This response can actually be produced |
| resolution. This type of lightning response is only | | | | under 4 circumstances: |
| really seen on a Local Area Network (LAN). A | | | | 1. The destination PC is protected by a firewall |
| WAN will normally take 10ms to 50ms depending | | | | that does not allow ICMP |
| on the distance. | | | | 2. The destination PC is not working (or |
| Test #3. Ping another PC across a WAN | | | | disconnected) |
| C:\it-pathways.com>ping Pathways-WAN-PC32 | | | | 3. There is a faulty router between the source |
| Pinging Pathways-WAN-PC32 with 32 bytes of | | | | and destination PC |
| data: | | | | 4. |