First, let me comment on the specific issue of packet headers. I've
actually programmed system code in protocol testers, and I'm working
now on an extension to OSPF and ISIS. When I was actually
programming, I could usually tell you the particular byte or bit
offset of a field, but, in general, I can't do that now. Nor do I
feel any particular day-to-day need to do so.
Now, if you are doing real-time operations and your protocol
analyzers or debug tools do not translate the field offsets, there
may be a practical reason to memorize the actual positions.
Otherwise, the important thing is to know what fields exist and what
they do.
If you know that a specific test asks for offsets, then I suppose you
must memorize them. A test that asks for them, IMNSHO, demonstrates
more a lazy test writer than it does understanding of the topic.
Flashing back to my clinical laboratory days, we were expected to use
checklists in performing life-critical tests, not to trust to memory.
While physicians usually do know the dosages of drugs they use every
day, it's malpractice not to look up something of which you aren't
100% sure. Indeed, many of the incentives underway to reduce health
care errors focus on computer-assisted prescribing systems that will
check dosages before the prescription is issued, rather than hoping a
doctor's handwriting is clear.
All this being said, I do find that there is a recent rash of
questions asking specifics that are reasonably easily found online.
People may have noticed that I'm often answering a question with a
question, suggesting sources for study.
To me, the idea of knowing that a protocol offset will be in an RFC,
and how to retrieve RFCs, is a pretty basic skill. Checking on CCO
is both easier and a more essential skill for anyone who expects to
progress in certification.
But I do like the idea of cow milking candidates. As a kid, my
theory was that you got the different milk products from separate
output interfaces on the cow. No cow had more than four ports. If
you needed additional products, you got a cow of a different color,
which was hard-wired for other products. Brown cows, of course,
provided chocolate milk.
>CNXs can rattle off the IP, TCP, and UDP header contents no problem. &;-)
>
>Priscilla
>
>
>At 02:22 PM 8/18/00, Chuck Larrieu wrote:
>>This thread did get a bit carried away. I believe I provided an adequate, if
>>minimal answer to the question. As one of the smart asses of the group, and
>>one prone to a bit of sarcasm myself, I still think that it is more than
>>fair for other folks - new folks and regulars - to point out that this is
>>indeed supposed to be a place where people can ask for help, information,
>>resources without belittlement.
>>
>>Let me offer all folks new to the certification game some information on
>>protocols.
>>One can find a wealth of information at
>>http://www.radcom-inc.com/acad/acatoc.htm , including the World of protocols
>>book I referred to. Everything you didn't want to know about the contents of
>>those headers at all layers.
>>
>>I would also like to ask - how many people, without looking at a chart
>>someplace, can define the contents of an IP header, a TCP header, a UDP
>>header. I mean bit for bit in order? I would guess that most of us have an
>>idea of the contents. Most of us know there are 20 bytes in both the TCP and
>>IP headers, and that the UDP header is 8 bytes 9 had to look it up. Was
>>thinking 10 ), but could tell all without referring to something.
>>
>>This is the kind of depth that is not covered in CCNA or CCNP, and with all
>>due respect to the difficulty of the CCIE, I don't recall anything about
>>this in my reading and references there either.
>>
>>It's ok to ask questions that will further your knowledge about routing,
>>routers, and how it all works. Honest.
>>
>>Chuck
>>
>>
>>From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
>>Jason
>>Sent: Friday, August 18, 2000 12:07 PM
>>To: [EMAIL PROTECTED]
>>Subject: Re: question on ip packet
>>
>>There is absolutely no value whatsoever in this reply. Please stop reading
>>if you are expecting to find any thing of value in this message.
>>The only reason I'm replying is that I figure if I'm going to have to wade
>>through all this cow jokes and whathaveyou, I might as well add to it.
>>
>>By the way, I'm a CCMC but I do not know what is inside milk. Is it white
>>color or can I get brown color and pink color milk from the cow or do I have
>>to feed them differently ? . I know this is a simple Q, but I know lots of
>>CCMC working in multi-million dollar milk farm who doesn't know how to
>>config a router or server and I figure I'm ahead of them in this game . NOW
>>if you are wondering how I get my CCMC, well, I know how to milk a Cow and
>>the Sybex book on CCMC never ask me to look at the color of the milk. I also
>>make use of the CCMC for Dummies book. I feel that that is a great book and
>>is just the right book for me.
>>
>> (Certified Cow Milking Candidate)
>>
>>"Luan Kim" <[EMAIL PROTECTED]> wrote in message
>>[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
>> > Brian,
>> > My knowledge of tcp/ip is enough for me to configure routers/switches.
>> > I'm still learning. There is nothing wrong with a network engineer who
>> > holds a ccna cert. that doesn't know what's inside an ip packet. I have
>> > friends who are 20+ years old and are currently network engineers and work
>> > for multi-billion dollar companies but they still don't know how to milk a
>> > cow:). Cheers.
>>
>> >
>> > > On Wed, 16 Aug 2000, Luan Kim wrote:
>> > >
>> > > > Can someone lighten me up as to what's inside an "ip packet"? Is
>>there a
>> > > > udp/tcp header in it? Is there a mac-address in it? Thanks for any
>> > > > input.
>> > >
>> > > You are a Network Engineer for a multi-million dollar company, hold a
>> > > CCNA, and are asking something trivial like whats in an IP packet? If
>>you
>> > > searched the web you would get that answer in a quick query. I am not
>>one
>> > > to flame, I just find it unreal that you could study for your CCNA and
>>not
>> > > come across what makes up an IP packet.........I even find it more mind
>> > > boggling that anyone could get their CCNA, have a job as a network
>> > > engineer, and not be with in 10 walking paces from a decent tcp/ip
>> > > reference that would have this in the first chapter.
>> > >
>> > > Brian
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