How long can something be continuous enroute as it bounces around the internet, not talking about a streaming video but a single packet (or whatever small unit it is). Is it possible to send something on the internet that just loops forever?
Every IP packet has a TTL (time-to-live) number in the packet header. Every time the packet is forwarded to another host, the TTL is decremented. If it reaches zero, the packet is dropped. The purpose of the TTL field is to prevent routing errors that cause things to go in circles from saturating a network.
The TTL field is eight bits, which means the maximum possible value is 255. However, some routers will drop packets with unusually large TTLs (anything above 64 or so) because they’re suspicious and may be part of a DoS attack. The default value is usually something like 30.
So, you couldn’t construct a packet on an IPv4 network that would bounce more than 255 times. Not sure about IPv6.
No. All IP packets have a “time-to-live” (TTL) field. When an IP packet is received, the TTL field is decremented. When the TTL field reaches 0, the packet is dropped. The TTL field has a maximum value of 255, so a packet can make a maximum of 255 hops before it’s dropped.
This is a necessary measure to protect against routing loops. Sometimes routers get confused about how to get a packet to its destination and will send that packet in a loop. If not for the TTL field, such packets would be sent in perpetuity, and the internet would very quickly become horribly congested with unroutable packets.
IPv6 packets have an 8-bit “max hop count” field. It’s exactly the same as the TTL field, but the name is more accurate.
FWIW, I once asked my secretary to scan a picture and email it to me. I watched her send it, and I went to my office to get it. It didn’t show up right away, and I needed it that day, so we did it again. I received the original email about three weeks later.
If you want to have fun, and you know a network manager, daisy chain as many geosynchronous satellite data links as possible. Each hop adds about 250 ms of delay.
In that case, there was a stuck mail queue somewhere. That email was sitting on the hard drive of an SMTP server, not aimlessly drifting through the network.
So, in a Super Worst Case Scenario, how long does it take to bounce around 255 times?
If we take mks57’s time of 250 ms per hop on a satellite link, that would take about 64 seconds. Satellites have much higher latency than most internet hops, though. It takes 15 hops to get from me to straightdope.com and the round-trip time is about 100 ms(which means that there’s about 50 ms of latency between me and straightdope.com).
Man, you party like I wild man! I don’t think I could ever get that crazy!