hey there is a conflict then......

Discussion in 'Networks' started by kobem, Dec 28, 2007.

  1. kobem

    kobem Megabyte Poster

    791
    1
    50
    this is from tcpipguide

    Next Header





    Next Header: This field replaces the Protocol field and has two uses. When a datagram has extension headers, this field specifies the identity of the first extension header, which is the next header in the datagram. When a datagram has just this “main” header and no extension headers, it serves the same purpose as the old IPv4 Protocol field and has the same values, though new numbers are used for IPv6 versions of common protocols. In this case the “next header” is the header of the upper layer message the IPv6 datagram is carrying. See below for more details.

    and from wikipedia

    Next header - Specifies the next encapsulated protocol. The values are compatible with those specified for the IPv4 protocol field (8 bits).

    according to tcpipguide , payload(data not protocol ) is in "NEXT HEADER field" though due to
    wikipedia NEXT HEADER just carries the "protocol of the payload" then
    looking at this schema

    [​IMG]

    wHICH ONE IS TRUE?

    --------------****is payload(data) in next header or under destination address?*****-------------

    ......................................................

    second

    it is said that ipv6 "main header " format consists of version , flow label , payload length ,
    next header , hop limit , traffic class ,source address and dest.address.

    question : --------****** it says main header but why is "the next header" in it?****** ---------it has to be out of
    main header i think
     
    Certifications: CCNA
  2. hbroomhall

    hbroomhall Petabyte Poster Gold Member

    6,624
    117
    224
    Read them again more carefully. They are both saying the same thing, but in different words. And the TCPIPGuide has far more detail, including diagrams on how the next-header chain works.

    The next-header field is there as an indication of what the next part is. The whole scheme is done like this to allow the easy disassembly of a headers/packet combination.

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
    WIP: Server+
  3. kobem

    kobem Megabyte Poster

    791
    1
    50
    shortly
    1- "is payload(data) under destination address field?"

    2- "main header >>> version , traffic class , flow label , payload length , hop limit ,source
    ve dest. address "

    ext header(s) outside of main header in next header?

    data ?
     
    Certifications: CCNA
  4. hbroomhall

    hbroomhall Petabyte Poster Gold Member

    6,624
    117
    224
    Data will appear after all the headers.
    You have missed out the next-header field. It is needed to start the chain (if there is a chain). And is quite clear in the diagram you quoted.
    There will be one there as well.

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
    WIP: Server+
  5. kobem

    kobem Megabyte Poster

    791
    1
    50
    oh my god , we returned to the start ........

    according to you next header is in main header , data will appear after all the headers mean what?

    please i have read lots of documents but
    main header is mentioned version , traffic class , flow label , payload length , hop limit ,source
    ve dest. address " and next header

    and in a document it says "next header consists of payload(data) and extension headers if there is
    ........

    *****************where is data? (it was after dest.address in ipv4 )*********************
     
    Certifications: CCNA
  6. BosonMichael
    Honorary Member Highly Decorated Member Award 500 Likes Award

    BosonMichael Yottabyte Poster

    19,183
    500
    414
    No, GBL... he didn't listen to my advice. :popcorn
     
    Certifications: CISSP, MCSE+I, MCSE: Security, MCSE: Messaging, MCDST, MCDBA, MCTS, OCP, CCNP, CCDP, CCNA Security, CCNA Voice, CNE, SCSA, Security+, Linux+, Server+, Network+, A+
    WIP: Just about everything!
  7. kobem

    kobem Megabyte Poster

    791
    1
    50
    i have no other chance , i have to achieve on network field somehow.
    and i am honest about that i am reading so many documents related to ipv6
    though

    i can not understand where payload is in ipv6 , i have no problem with ipv4 but ipv6
    is too complicated
     
    Certifications: CCNA
  8. BosonMichael
    Honorary Member Highly Decorated Member Award 500 Likes Award

    BosonMichael Yottabyte Poster

    19,183
    500
    414
    To get into the network field...

    ...start at the bottom...

    ...and work your way up.

    You're trying to work your way into the middle. It simply won't work.

    If you don't have a problem with IPv4, then why are you having such a difficult time figuring out where data goes in a packet?!? :blink IPv6 data goes in the same place as IPv4 data - after the header. Dude - I found this pic in *2* seconds, literally!

    [​IMG]
     
    Certifications: CISSP, MCSE+I, MCSE: Security, MCSE: Messaging, MCDST, MCDBA, MCTS, OCP, CCNP, CCDP, CCNA Security, CCNA Voice, CNE, SCSA, Security+, Linux+, Server+, Network+, A+
    WIP: Just about everything!
  9. kobem

    kobem Megabyte Poster

    791
    1
    50
    that looks nice however from one of my documents i have seen sth like this:

    a-in ipv6 there is a "mandatory main header" then the data thats OK

    b-by means , next header is in main header

    c- main header contains "version, traffic class field , flow label field , hop limit field , source address
    and dest.address field AND NEXT HEADER

    -------1- but extension headers(if any) come after main header ...... if next header is in main header
    how can extension headers come after main header ?----------------

    2- -------but next header includes extension headers (if any) and the protocol and upper layer data-----
     
    Certifications: CCNA
  10. kobem

    kobem Megabyte Poster

    791
    1
    50
    is it like this ?

    [​IMG]
     
    Certifications: CCNA
  11. BosonMichael
    Honorary Member Highly Decorated Member Award 500 Likes Award

    BosonMichael Yottabyte Poster

    19,183
    500
    414
    I hesitate to answer this because you don't have the basic foundation of knowledge for most networking topics... and I'm not going to explain each and every part to you in detail - I get paid to do that level of training in the products I create.

    Extension headers, if required, are placed between the IPv6 header and the payload. The Next Header field tells what kind of information is in the next extension header. If multiple extension headers exist, then the first extension header will have a Next Header field that describes what information is in the next extension header. The final extension header in a packet will have a Next Header field that indicates that upper-layer protocol data will follow (for example, a Next Header value of 6 denotes a TCP packet, and a Next Header value of 17 denotes a UDP packet).

    This stuff is easily findable on the Internet - I simply searched for extension headers on Google and clicked on the first link they provided. To be honest, I didn't know anything about extension headers before I wrote this message. But the explanations I found on the Internet were quite clear. It's *really* that easy.
     
    Certifications: CISSP, MCSE+I, MCSE: Security, MCSE: Messaging, MCDST, MCDBA, MCTS, OCP, CCNP, CCDP, CCNA Security, CCNA Voice, CNE, SCSA, Security+, Linux+, Server+, Network+, A+
    WIP: Just about everything!
  12. kobem

    kobem Megabyte Poster

    791
    1
    50
    as i realised from documents , data comes after addresses if no extension headers are avaliable like
    main header + data(payload)

    if we have extension headers , it is main header + extension header + data (payload) shortly
    next header included in main header

    ..........................








    i apprehended them before you replied . Now trying to understand site-local and link-local
    generation only thing i didn't catch that whether link-local and site-local have
    global prefix ? (i mean router)
     
    Certifications: CCNA
  13. Sparky
    Highly Decorated Member Award 500 Likes Award

    Sparky Zettabyte Poster Moderator

    10,718
    543
    364
    New year, same posts. Might as well keep drinking! :alc
     
    Certifications: MSc MCSE MCSA:M MCSA:S MCITP:EA MCTS(x5) MS-900 AZ-900 Security+ Network+ A+
    WIP: Microsoft Certs
  14. Luddym

    Luddym Megabyte Poster

    797
    19
    74
    :biggrin I thought I was in Groundhog day for a minute there.
     
    Certifications: VCP,A+, N+, MCSA, MCSE
    WIP: Christmas Drunkard
  15. kobem

    kobem Megabyte Poster

    791
    1
    50
    hm as i realised

    link - local unicast address is used for hosts on the same link (subnet)
    and it is like below :

    network prefix following interface id

    fe80::/64 (why 64 hence its binary format is 1111(F) 1110(E) 1000(8) 0000(0) then 52 bits zero
    then 64 bits interface id generated by using MAC address)

    site-local unicast address is used for communications on different subnets

    fec0::/48 (it is similar to link-local even though it also has subnet-id(16 bits) then 64 bits interface id)

    ...............................

    "question one" : link-local is for hosts on the same link , due to this
    can we use them in the environment that "shows there are many PCs linked to a switch?"


    "question two" : it seems impossible to use link-local when a router is on but are we able to do the opposite by means using "site-local " also in the example "i have given in question one "?

    "question three" : either site-local or link-local requires a global prefix to complete
    the addressing configuration?
     
    Certifications: CCNA
  16. greenbrucelee
    Highly Decorated Member Award

    greenbrucelee Zettabyte Poster

    14,292
    265
    329
    honestly :cussing:cussing
     
    Certifications: A+, N+, MCDST, Security+, 70-270
    WIP: 70-620 or 70-680?
  17. wizard

    wizard Petabyte Poster

    5,767
    42
    174
    [​IMG]
     
    Certifications: SIA DS Licence
    WIP: A+ 2009
  18. BosonMichael
    Honorary Member Highly Decorated Member Award 500 Likes Award

    BosonMichael Yottabyte Poster

    19,183
    500
    414
    Ah, rather than use different colors and sizes, he's now gone and used different fonts for each question. :rolleyes:
     
    Certifications: CISSP, MCSE+I, MCSE: Security, MCSE: Messaging, MCDST, MCDBA, MCTS, OCP, CCNP, CCDP, CCNA Security, CCNA Voice, CNE, SCSA, Security+, Linux+, Server+, Network+, A+
    WIP: Just about everything!
  19. kobem

    kobem Megabyte Poster

    791
    1
    50
    OK i' m writing down normally !


    "question one" : link-local is for hosts on the same link , due to this
    can we use them in the environment that "shows there are many PCs linked to a switch?"


    "question two" : it seems impossible to use link-local when a router is on but are we able to do the opposite by means using "site-local " also in the example "i have given in question one "?

    "question three" : either site-local or link-local requires a global prefix to complete
    the addressing configuration?
     
    Certifications: CCNA
  20. hbroomhall

    hbroomhall Petabyte Poster Gold Member

    6,624
    117
    224
    Not sure exactly what you are asking here - but link-local addresses will be dropped by a router - they are 'unroutable'.

    Yes - but you will need (perhaps) to override the automatic IP address configuration.
    They will have the usual FEx prefixes.

    Harry.
     
    Certifications: ECDL A+ Network+ i-Net+
    WIP: Server+

Share This Page

Loading...
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.