Talk:Web Science/Part1: Foundations of the web/Internet Protocol/IP header

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Quiz-question 1 seems to be wrong

The first question says that an "Ethernet frame can have a data payload of 1500 Bytes minus 20 Bytes of IP header.". The question though asks "to store a standard IPv6 package with IHL=5". First of all, there is no IHL-field in the IPv6-header. Second, the IPv6-header has a fixed length of 40 bytes [RFC2460]. For an IPv4 package with no additional options set, this answer would be correct. --Onse (discuss • contribs) 10:49, 24 October 2013 (UTC)

In the quiz I ment an IPv4 package (since we are talking about IPv4 inside this MOOC) Thanks for your hint. Next time if you find a mistake you could also correct it directly on the quiz page --Renepick (discuss • contribs) 10:55, 24 October 2013 (UTC)

quiz question 2 clarifying

An error message will be send to the sender (specifying the maximum allowed data size) - you marked as true. Is it true? I can not find the answer, in wiki we have only:

If the DF flag is set, and fragmentation is required to route the packet, then the packet is dropped. w:IPv4#Flags

Nothing about sending error message back. --oleamm (discuss • contribs) 10:33, 31 October 2013 (UTC)

from the RFC 1191 (Path MTU Discovery) I quote:

If any of the datagrams are too large to be forwarded without fragmentation by some router along the path, that router will discard them and return ICMP Destination Unreachable messages with a code meaning "fragmentation needed and DF set"

The Internet Control Message Protocol itself is described in: rfc 792 --Renepick (discuss • contribs) 11:51, 31 October 2013 (UTC)

quiz question 4 clarifying

Not sure about "increase the profit of internet service provider" =) Was it designed especially for this purpose? I thought only for traffic prioritization.--oleamm (discuss • contribs) 10:33, 31 October 2013 (UTC)

What other reasons do you know for traffic prioritization? --Renepick (discuss • contribs) 11:51, 31 October 2013 (UTC)

quiz question 6 clarifying

As I understood "Total length" CAN be changed (if fragmentation is required). The same for source & destination IP addresses (they will be changed only if NAT was used). But that changes will not occur always. Only TTL will be changed always. Or I misunderstood something? --oleamm (discuss • contribs) 10:33, 31 October 2013 (UTC)

I am currently not sure if total length will stay the same during fragmentation or not (when I created the quiz question I had the unfragmented version in mind) can anyone find a reference for this? --Renepick (discuss • contribs) 11:51, 31 October 2013 (UTC)

Question about Total Length attribute in IPv4 header

"IP header" video shows that the Total Length attribute allows IP package with 65536 Bytes as maximum. I have read RFC 791, and in page 13 of Total Length part, it says "This field allows the length of a datagram to be up to 65,535 octets." Is that means the maximum total length of IPv4(header part plus data part) is 65535 Bytes but the package length is 65536 Bytes according to 4 Bytes architecture? --Schin (discuss • contribs) 18:26, 21 January 2014 (UTC)

q

a --141.26.90.250 (discuss) 10:51, 5 November 2014 (UTC)

DSCP

could you explain more about DSCP? --141.26.69.70 (discuss) 20:00, 4 November 2016 (UTC)