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TOPIC: Errata on information

Errata on information 11 years 2 weeks ago #11492

  • Arani
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where do i report an error on one of the web pages?the page which describes the IP header has some errors on it, or that's what i think it is. so where do i report it?
would that be here as well?
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Re: Errata on information 11 years 2 weeks ago #11493

  • DaLight
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Yes Arani, this is the right place.
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alrighty then!!! 11 years 2 weeks ago #11495

  • Arani
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well, in that case..here it goes

i noticed there are some errors on the IP header page under the networking-->protocols-->internet procotol subnetting-->internet protocol header

the second field says its of length 32 bits. its not the actually 32 bits in length.
the actualy sequence of an IP header is:
version(ver) = 4 bits
header length (hlen) = 4 bits
type of service (TOS) = 8 bits
total length (Tot Len) = 16 bits
indentification (ID) = 16 bits
Flags = 3 bits
fragmentation offset (frag) = 13 bits
time to live (TTL) = 8 bits
protocol (proto) = 8 bits
header checksum = 16 bits
source IP address = 32 bits
destination IP address = 32 bits
options = variable length
data = variable length

the description on that page says,
version = 4 bits, but
hlen = 32 bits, this should be 4 bits
feel free to correct me if i am wrong
cheers
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errata corrected with more errors!!! 11 years 2 weeks ago #11499

  • Arani
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sorry to bother you again but i noticed more errors on the header description!!!
the header length has been corrected to 4 bits.
but the fragmentation flag is wrongly labelled as 2 bits, it should be 3 bits
the fragmentation offset is wrongly labelled as 8 bit, it should be 13 bits
rest of the header is ok

feel free to correct me if i am wrong
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Re: Errata on information 11 years 1 week ago #11657

  • Chris
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Arani,

We'll look into the corrections as soon as possible.

Thank you for informing us !
Chris Partsenidis.
Founder & Editor-in-Chief
www.Firewall.cx
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Re: Errata on information 11 years 1 week ago #11733

  • sahirh
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Hmm you're right, that should be

Flags
3 bits. Control flags:

Bit 0 is reserved and must be zero

Bit 1: Don’t fragment bit:
0 May fragment.
1 Don’t fragment.

Bit 2: More fragments bit:
0 Last fragment.
1 More fragments.

Fragment offset
13 bits. Indicates where this fragment belongs in the datagram. The fragment offset is measured in units of 8 bytes (64 bits). The first fragment has offset zero.

or as it is in ip.h

struct ip {
u_char ip_hl:4, /* header length */
ip_v:4; /* version */
u_char ip_tos; /* type of service */
short ip_len; /* total length */
u_short ip_id; /* identification */
short ip_off; /* fragment offset field */
#define IP_DF 0x4000 /* dont fragment flag */
#define IP_MF 0x2000 /* more fragments flag */
#define IP_OFFMASK 0x1fff /* mask for fragmenting bits */
u_char ip_ttl; /* time to live */
u_char ip_p; /* protocol */
u_short ip_sum; /* checksum */
struct in_addr ip_src,ip_dst; /* source and dest address */
};

Thanks for the corrections

Cheers,
Sahir Hidayatullah.
Firewall.cx Staff - Associate Editor & Security Advisor
tftfotw.blogspot.com
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