From: Janet Davis (jlnd_at_cs.washington.edu)
Date: Mon Jan 12 2004 - 12:56:52 PST
You can assume that sequence numbers are unique and sequential for each
sender, but not unique for the entire network.
Imagine how difficult it would be to have global sequence numbers. What
if two nodes decided to send a packet at the same time?
Cheers,
Janet
On Mon, 12 Jan 2004, Abhinav Jain wrote:
> Janet,
>
> i understand the TTL part, but i think I am confused on the sequence
> number... First i thought that whenever we send any message we will have our
> address as src address and the N as seq num for N th packet we sent,, but
> than i realized that could lead to some duplicacy as my 2nd packet could be
> same as my friends third packet.
>
> SO how is the sequence number implemented,,, and which node is the first one
> to send out a message
>
> Abhinav
> ----- Original Message -----
> From: "Janet Davis" <jlnd_at_cs.washington.edu>
> To: <cse461_at_cs.washington.edu>
> Sent: Monday, January 12, 2004 10:54 AM
> Subject: [Cse461] Re: TTL Specifications
>
>
> > An addendum:
> >
> > The range of valid sequence numbers is 1..MAX_TTL. When you originate a
> > packet, its TTL should be MAX_TTL when you call sendPkt. For forwarding,
> > also note that you can't send a packet with TTL 0.
> >
> > On the receiving side, you should accept (i.e., process) any packet that
> > has a valid TTL when it arrives.
> >
> > Cheers,
> > Janet
> >
> > On Sun, 11 Jan 2004, Janet Davis wrote:
> >
> > > The important thing to note is that it is not valid to send a packet
> with
> > > TTL=0. This implies that when you get a packet with TTL=1, you should
> > > process it if you are its destination---and then drop it if its TTL
> > > becomes 0. You can generalize this rule to higher TTL values.
> > >
> > > Cheers,
> > > Janet
> > >
> > > On Sun, 11 Jan 2004, Alissa Harrison wrote:
> > >
> > > > Janet,
> > > >
> > > > My partner and I were discussing the specification for decrementing
> > > > TTLs. We think that because there is ambiguity between when a TTL gets
> > > > decremented that interoperability problems could arise. This would
> > > > happen if one app decremented the TTL on the send while another
> > > > decremented on the recieve of a packet (when talking to another
> student,
> > > > we found we were disagreeing when to decrement). Shouldn't there be a
> > > > clear guideline for the whole class?
> > > >
> > > > Alissa and Jon
> > >
> > > --
> > > Janet Davis
> > > jlnd_at_cs.washington.edu
> > > http://www.cs.washington.edu/homes/jlnd/
> > >
> > >
> >
> > --
> > Janet Davis
> > jlnd_at_cs.washington.edu
> > http://www.cs.washington.edu/homes/jlnd/
> >
> > _______________________________________________
> > Cse461 mailing list
> > Cse461_at_cs.washington.edu
> > http://mailman.cs.washington.edu/mailman/listinfo/cse461
> >
>
>
-- Janet Davis jlnd_at_cs.washington.edu http://www.cs.washington.edu/homes/jlnd/ _______________________________________________ Cse461 mailing list Cse461_at_cs.washington.edu http://mailman.cs.washington.edu/mailman/listinfo/cse461
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