Hey all,
Since I have found that many are not clear on what these terms actually mean, I decided to write a *ORIGINAL* piece detailing the intricasies.
PING
----
This method *its a noun, a verb and a adjective* is often used to measure net connectivity between two nodes connection to any network, whether it be LAN-LAN, LAN-INTERNET, INTERNET-LAN or INTERNET-INTERNET. This is because, when you ping a particular IP address, a packet of data is sent to the target machine and the target machine send a similar packet of data to your machine. Then the time taken for the return packet to reach is added to -(the time when the packet was sent) and you have your ping time. A valid ping time means you are reachable from the source computer.
Now a few more details:
- When you send a packet (a fragment of data) to the target machine, it travels from machine to machine (machine means a networked host, actually could be a router, a gateway, a media converter, what not) before finally reaching the target IP address. How does a HOST decide the next host to which it will hand off the packet. Various ROUTING PROTOCOLS are used to determine that in the automated process. These ROUTING PROTOCOLS function somewhat similar to the SWITCH BOARD operators of the days of yore. But since this process has to be automated, we cant have people sit on machines doing routing.
- Many a times, the ROUTE between you and the target machine is non-optimal. Suppose you have taken BB connetion from a ISP which has taken a cheap way out and is sourcing downstream bandwidth from a Sattelite provider like PCM-THAICOM. *Downstream* signifies the download which it will provide to the customers. So, because having only downstream is useless (if not, then how will the websites and other servers know about the customers request and send the data), the ISP will take some nominal amount of upstream b/w from a local ISP like VSNL, Bharti, Reliance. Then what is happening is, your packets are travelling out over the local ISP connection and returning to you over a different path through the satellite. Thought you might get higher bandwidths, your ping times (that is Round Trip Time = RTT) will suck and will be aroud ~ 800+ ms. You wont be able to do voice chatting and all sorts of interactive activites would lag a lot, including multiplayer games.
- Sometimes, you are getting BAD routing itself. Meaning the ISP is not advertising ur IP address properly. Suppose, you (or rather your ISP) is upstreaming through VSNL and has taken downstream of 10 Mbps from VSNL also. Since VSNL is very well connection to most internations ISPs you should get optimal PINGs. However, if your IP addresses are not advertised as being reachable throught VSNL, then, when the destination computer having recieved your request wants to send a responce, the return packets would travel all over the world before finally reaching VSNL -> ISP -> YOU. Instead of taking a direct path DEST -> DEST-ISP -> VSNL -> YOU, it would be something like: DEST -> DEST-ISP -> RELIANCE -> BHARTI -> VSNL -> ISP -> YOU. All those extra HOPS (the computers the packet has to travel through) add those extra ms to the PING time and make your lag worse.
Latency
Latency is the figure you see in the CS, i.e. the time it takes for the packets to travel from Source to Destination. It does not take into account the time it take for the packets to travel back at you. So, it rather gives a efficiency of the UPSTREAM bandwidth you have.
Summary: PING time = Time taken for the packet to travel from your PC to the destination comp and back.
I hope this guide helped you guys cleared up a few facts.
Source: Kidoman's Brain. This was also posted at Vinuthomas by me and become a very big thread.
hyeah: :hap2:
Cheers,
Karan
Since I have found that many are not clear on what these terms actually mean, I decided to write a *ORIGINAL* piece detailing the intricasies.
PING
----
This method *its a noun, a verb and a adjective* is often used to measure net connectivity between two nodes connection to any network, whether it be LAN-LAN, LAN-INTERNET, INTERNET-LAN or INTERNET-INTERNET. This is because, when you ping a particular IP address, a packet of data is sent to the target machine and the target machine send a similar packet of data to your machine. Then the time taken for the return packet to reach is added to -(the time when the packet was sent) and you have your ping time. A valid ping time means you are reachable from the source computer.
Now a few more details:
- When you send a packet (a fragment of data) to the target machine, it travels from machine to machine (machine means a networked host, actually could be a router, a gateway, a media converter, what not) before finally reaching the target IP address. How does a HOST decide the next host to which it will hand off the packet. Various ROUTING PROTOCOLS are used to determine that in the automated process. These ROUTING PROTOCOLS function somewhat similar to the SWITCH BOARD operators of the days of yore. But since this process has to be automated, we cant have people sit on machines doing routing.
- Many a times, the ROUTE between you and the target machine is non-optimal. Suppose you have taken BB connetion from a ISP which has taken a cheap way out and is sourcing downstream bandwidth from a Sattelite provider like PCM-THAICOM. *Downstream* signifies the download which it will provide to the customers. So, because having only downstream is useless (if not, then how will the websites and other servers know about the customers request and send the data), the ISP will take some nominal amount of upstream b/w from a local ISP like VSNL, Bharti, Reliance. Then what is happening is, your packets are travelling out over the local ISP connection and returning to you over a different path through the satellite. Thought you might get higher bandwidths, your ping times (that is Round Trip Time = RTT) will suck and will be aroud ~ 800+ ms. You wont be able to do voice chatting and all sorts of interactive activites would lag a lot, including multiplayer games.
- Sometimes, you are getting BAD routing itself. Meaning the ISP is not advertising ur IP address properly. Suppose, you (or rather your ISP) is upstreaming through VSNL and has taken downstream of 10 Mbps from VSNL also. Since VSNL is very well connection to most internations ISPs you should get optimal PINGs. However, if your IP addresses are not advertised as being reachable throught VSNL, then, when the destination computer having recieved your request wants to send a responce, the return packets would travel all over the world before finally reaching VSNL -> ISP -> YOU. Instead of taking a direct path DEST -> DEST-ISP -> VSNL -> YOU, it would be something like: DEST -> DEST-ISP -> RELIANCE -> BHARTI -> VSNL -> ISP -> YOU. All those extra HOPS (the computers the packet has to travel through) add those extra ms to the PING time and make your lag worse.
Latency
Latency is the figure you see in the CS, i.e. the time it takes for the packets to travel from Source to Destination. It does not take into account the time it take for the packets to travel back at you. So, it rather gives a efficiency of the UPSTREAM bandwidth you have.
Summary: PING time = Time taken for the packet to travel from your PC to the destination comp and back.
I hope this guide helped you guys cleared up a few facts.
Source: Kidoman's Brain. This was also posted at Vinuthomas by me and become a very big thread.
hyeah: :hap2: Cheers,
Karan
