Paul,
Thanks for your reply. How about helping me with this one:
When are ICMP redirects used in EIGRP?
Looking forward to your reply!
Thanks all.
"Paul Werner" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > > > Excuse me. I meant to ask if a UDP Packet can be
> fragmented
> > >
> > > Yes.
> > >
> > > > and what happens
> > > > to the UDP Header if it can be fragmented?
> > >
> > > Nothing. It's sent unchanged in the first fragment. The
> only header
> > that
> > > gets modified and replicated in each fragment is the IP
> header.
> >
> > So will each fragment have a bit of the UDP Header in it or I
> >am correct in saying that only the first fragment has the FULL
> >UDP >Header in it ...
> > how does the destination router know how to put the UDP paket
> back together?
>
> Priscilla et al. have appropriately addressed your original
> question and follow on questions. What you have not asked (and
> what has not been addressed) is what layers are performing
> which functionality (and why).
>
> The User Datagram Protocol is an OSI transport layer protocol
> that is designed to give a low overhead, unreliable (best
> effort) datagram delivery. Internet standards documents
> describe UDP as a connectionless datagram PDU, while Cisco
> refers to it as a segment. Understand Cisco's version for
> their tests, and understand the Internet version for real
> life. One of the principal reasons for UDP, in addition to its
> low overhead, is the ability to deliver datagrams from one to
> many hosts. TCP is always set up as a one to one connection.
> If you need to deliver UDP datagrams to a host, you must depend
> upon the lower layers for delivery (as you do for TCP).
>
> In the case of delivery over mutliple types of media,
> fragmentation may be required. This is handled as a layer 3
> (network layer) function. IP has as part of its protocol, the
> ability to fragment data that will not traverse a low MTU
> (maximum transmissible unit) path. A typical MTU might be 1500
> bytes in an Ethernet environment, but it might be much larger
> in a Token Ring environment. One of the layers must make
> accomodation for this situation, otherwise you will have lost
> data (you can't fit 10 lbs of manure in a five pound bag :-)
> This process can be optimized to a degree. Many Internet hosts
> and gateways support the ability to do Path MTU discovery which
> will allow for advanced discovery of the Path MTU and set it as
> the default for transmission. In some cases this capability
> works well, in other cases it does not. Additionally, some
> hosts will have a "Do not Fragment" bit set on the IP header to
> not allow any form of fragmentation. If this occurs and
> fragmentation is required but not possible, an ICMP error
> message will be sent to the originator indicating fragmentation
> was required, but not possible. In some instances, if the
> amount of datagrams that need to be fragmented cannot be
> buffered by the receiving host to completion of reassembly, you
> may receive a different ICMP error message indicating a
> fragmentation failure. Either situation will require a
> retransmission of all fragments.
>
> I would strongly recommend reading TCP/IP Illustrated by the
> late W. Richard Stevens. It is a must read to understand the
> TCP/IP protocol suite.
>
> HTH,
>
> Paul Werner
>
> ________________________________________________
> Get your own "800" number - Free
> Free voicemail, fax, email, and a lot more
> http://www.ureach.com/reg/tag
>
> **NOTE: New CCNA/CCDA List has been formed. For more information go to
> http://www.groupstudy.com/list/Associates.html
> _________________________________
> UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html
> FAQ, list archives, and subscription info: http://www.groupstudy.com
> Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
>
**NOTE: New CCNA/CCDA List has been formed. For more information go to
http://www.groupstudy.com/list/Associates.html
_________________________________
UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html
FAQ, list archives, and subscription info: http://www.groupstudy.com
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
