GATE Overflow Test Series | Computer Networks | Test 1 | Question: 26

Question

Every host in an $IPv4$ network has a $1$ millisecond resolution real-time clock with battery backup. Each host needs to generate up to $4096$ unique identifiers per second. Assume that each host has a globally unique $IPv4$ address. If you are to design a $60$-bit globally unique ID for this purpose, the time period (in seconds) after which the identifiers generated by a host wrap around will be _________

Answer 1

Each host needs to generate $4096$ unique identifiers per second which requires $\lg 4096 = 12\; \text{bits}$.
    
Now, these $12\;\text{bits}$ along with $32\;\text{bit}$ globally unique IP address will give a globally unique $44\;\text{bit}$ IDs which stays constant.
Since we are allowed $60\;\text{bits}$ we can use the next $16\;\text{bits}$ using the clock which changes every millisecond interval. Thus our IDs will wrap around once in $2^{16}\;\text{milliseconds or }\; 65.536\;\text{sec}.$

Comments

The second extension addresses the problem of TCP’s 32-bit Sequence-
Num field wrapping around too soon on a high-speed network. Rather
than define a new 64-bit sequence number field, TCP uses the 32-bit
timestamp just described to effectively extend the sequence number
space. In other words, TCP decides whether to accept or reject a seg-
ment based on a 64-bit identifier that has the SequenceNum field in
the low-order 32 bits and the timestamp in the high-order 32 bits. Since
the timestamp is always increasing, it serves to distinguish between two
different incarnations of the same sequence number. Note that the time-
stamp is being used in this setting only to protect against wraparound; it
is not treated as part of the sequence number for the purpose of ordering
or acknowledging data.

Source:Larry Peterson

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what is the name of this topic? any reference to study this?

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https://gateoverflow.in/2061/gate-cse-2014-set-3-question-27