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Community Member

Packet

Dear all

I don't think,there is  a fix TTL value in every packet, i want to know, how ttl is managed in internet connection, where

the packet has to traverse across thousands of hops, please can u help me to avoid this confusion?

and what are the factors, that effects to assign the initial TTL value in a packet.

Thanks for a kind  response

2 REPLIES
Cisco Employee

Re: Packet

Hello,

Typically, the TTL value is set as per RFCs (1700 for example) which specify a value of 64 for IP packets. But different OS manufacturers use different values (between 1 to 255). Windows sets it at 128 (it can be changed through modifying registry values).

http://support.microsoft.com/kb/314053

Similarly, when you are doing traceroute, the TTL value will be started at 1 and for every hop, it will be incremented.

Hope this answers your questions.

Regards,

NT

Re: Packet

Hari,

TTL eventhough is time to live is decremented on everyhops (earlier RFC recommended a 1 sec decrement per hop)

Its a misconception that the packet has to travel through 1000 hops across the internet.

For eg: ive personally checked that it takes less than 20-25 hops between two nodes seperated by 5000 miles

You may check with a trace to google.com and confirm..-:)

The packets are decremented everyhop, starting from the value implemented w.r.t to the IP stack for that OS till the value reaches 0 and then would die.

The max value being 255 since TTL has 8 bits in the IP Packet header.

Hope to help,

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