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Re: [ns] IP headers
Have you looked at chapter 12 in ns manual.
Regards,
Kun-chan Lan
On Fri, 2 Mar 2001, sdcoulso wrote:
> Hello,
>
> I am working on my final year project and I am using ns. I however need to alter
> some of the values in the IP hearer for the datagrams sent over my modelled
> network.
>
> A summary of the contents of the internet header follows:
>
> 0 1 2 3
> 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> |Version| IHL |Type of Service| Total Length |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Identification |Flags| Fragment Offset |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Time to Live | Protocol | Header Checksum |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Source Address |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Destination Address |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
> | Options | Padding |
> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
>
>
> In particular I would like to alter the values for the 'Type of Service' field.
> The Type of Service provides an indication of the abstract parameters of the
> quality of service desired. These parameters are to be used to guide the
> selection of the actual service parameters when transmitting a datagram through
> a particular network. Several networks offer service precedence, which somehow
> treats high precedence traffic as more important than other traffic (generally
> by accepting only traffic above a certain precedence at time of high load). The
> major choice is a three way tradeoff between low-delay, high-reliability, and
> high-throughput.
>
> Bits 0-2: Precedence.
> Bit 3: 0 = Normal Delay, 1 = Low Delay.
> Bits 4: 0 = Normal Throughput, 1 = High Throughput.
> Bits 5: 0 = Normal Relibility, 1 = High Relibility.
> Bit 6-7: Reserved for Future Use.
>
> 0 1 2 3 4 5 6 7
> +-----+-----+-----+-----+-----+-----+-----+-----+
> | | | | | | |
> | PRECEDENCE | D | T | R | 0 | 0 |
> | | | | | | |
> +-----+-----+-----+-----+-----+-----+-----+-----+
>
> Precedence
>
> 111 - Network Control
> 110 - Internetwork Control
> 101 - CRITIC/ECP
> 100 - Flash Override
> 011 - Flash
> 010 - Immediate
> 001 - Priority
> 000 - Routine
>
> My aim is to send packets accross the netwok and have control over the values in
> this field, ie send packets through a particular link with different type of
> service tags and log the effects. I have all this set up, all I need to do is
> know how to change the values in the 'type of service' field. I suspect this is
> easy once you know how and where to do it.
>
> Any help would be greatly welcome
>
> Stephen Coulson
> ---------------
> [email protected]
> [email protected]
>
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> *************************************
>
> Why Rule The World When I Can Eat Baked Beans (Neil Freeman 15/11/99)
>