I have PC->Router->DSL Modem->ISP, Does ISP Router learn t..

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Archived from groups: comp.dcom.lans.ethernet (More info?)

I wanted to know how Internet works?, especially when my PC is on the
Internet, who know my MAC address, I have this config:

PC <--> Router <--> Cable Modem/ADSL Modem <---> ISP

How omy PC gets packets, who learn the PC MAC address, does Cable
modem/ISP know the PC MAC address, or PC MAC address can't know beyond
my Router at home?. I am very curious to know IP and MAC address
storing and forwarding. Also when I have an e-mail, does my e-mail
client receives my mail based on Port address right, if I assign that
port to some other application, then both applications will receive
that?. Also how can I know which ports are not using, incase if I want
to write some application. Thanks.

 

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Archived from groups: comp.dcom.lans.ethernet (More info?)

Router's are layer 3 devices. Layer 3 of the OSI layers that is. Layer
3 devices in normal operation overwrite the layer 2 information of a
packet (the mac address). So only your router knows your mac address.
Your ISP knows the mac address of your Router and associates that mac
address with the IP address of your router (the IP address that your
ISP gave you). Other routers out on the internet past your directly
connected segment may only know the IP address of your router. They
have a route table saying that in order to get there, they must send to
the next router in the path, and they know the mac address of only the
next hop, not the mac address of the final destination. This is how
the typical ethernet segments are pieced together. ISP's of course use
many different methods for moving data around on the internet, ethernet
being rare and SONET, ATM and others being more prevelant. If you wish
to write a network application, I suggest you lookup and study the OSI
model, and take a look here at the already assigned TCP/UDP ports:
http://www.iana.org/assignments/port-numbers

Kevin

 

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Kevin,

I ma little confused here, so my home Router knows only my PC's MAC
address and IP, similarly My Routers's IP and MAC is known by my ISP (I
have Cable modem in the middle, that doesn't have any MAC or IP?). In
that case my ISP used IP + MAC to send and receive packets from
corresponding web address right?. I am trying to understand why IP and
MAC required, why not only one?. Why this MAC address came into picture
since every PC/Router had IP address?. Thanks.

 

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Archived from groups: comp.dcom.lans.ethernet (More info?)

In article <1114980233.598897.28710@o13g2000cwo.googlegroups.com>,
<santa19992000@yahoo.com> wrote:
:I ma little confused here, so my home Router knows only my PC's MAC
:address and IP, similarly My Routers's IP and MAC is known by my ISP (I
:have Cable modem in the middle, that doesn't have any MAC or IP?). In
:that case my ISP used IP + MAC to send and receive packets from
:corresponding web address right?. I am trying to understand why IP and
:MAC required, why not only one?. Why this MAC address came into picture
:since every PC/Router had IP address?. Thanks.

Not every ethernet device has an IP address. IP is -one- of the
possible mid-layer communications protocols. Appletalk and
IPX (Novell) are two other well-known mid-layer communications
protocols.

Within a LAN, all the -real- work of deliverying packets is handled
by MAC address. Outside of a LAN, all the real work of getting
packets over multiple hops is done by IP address, with the MAC
address being continually changed along the way in order to
do device-to-device conversations.

Roughly speaking, your ISP gets your packets as far as your
router by using the IP address. Once the packet is at your
router, the router sends out a broadcast message saying,
"I have a package here for Mr. Frank N. Packet", and your PC
responds with, "That's me, I'm at pnuematic tube #182!";
your router then remembers that information for awhile, and
further packets to Frank N. Packet are dropped into
pneumatic tube #182 without pausing to check to see whether
Frank N. Packet is still there or is Out To Lunch.

Or if you prefer, think of it as addressing a letter to
a particular job title at a corporate office. The corporate
address is what the mail system uses to get the letter as
far as the corporate mailroom, and the mailroom looks up
the appropriate office number; once that is done, delivery
is done to the office. The same person might have several
different roles, and receive mail for "Job Applications",
"Head, Finances", and "Accounts Receivable" -- the mailroom
can handle that easily, without requiring that each different
role's mail be delivered to a different office.
--
Are we *there* yet??

 

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Archived from groups: comp.dcom.lans.ethernet (More info?)

Walter, Thanks for nice explanation, appreciated.