KW S wrote:
> I am reading RFC760 (IP protocol) and have the following questions.
>
> IHL : 4 bits
>
> Internet header length is the length of the internet header in 32 bits
words
>
> Question: what do u mean by the 4 bits and 32 bits words
The IHL is 4 bits long, and thus can have a maximum value of 2^4-1=15.
Which, in turn, means that the IP header could in theory be a maximum of
15 32-bit(=4 byte) units ('words') long, or 60 bytes.
> Total length :16 bits
>
> Total length is the length of the IP packets in octect including the
> internet headers and data. This field allows the length of a packet to be
up
> to 65,535 octets.
>
> Question: How do we arrive to the figure 65,535 octects
2^16-1.
> Such long packets are impractical for most host and networks.
Think MTU and fragmentation. An *IP packet* can be up to 64KB large, but
that does no mean that the underlying network must be able to transmit
or receive *frames* that long.
>
> All hosts must be prepared to accept datagram of up to 576 octects
>
> Question : 576 octects is the same as 576 bytes and how can it fit into the
> total length of 16 bits which is 2 bytes
See above. The length is a *16-bit value*, not 16 bits itself.
Regards,
Marco.
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