TCP/IP in 802.3 and 802.11 frame Post: 302265531

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Special Forums IP Networking TCP/IP in 802.3 and 802.11 frame Post 302265531 by Lukas on Sunday 7th of December 2008 10:28:25 PM

12-07-2008

Registered User

TCP/IP in 802.3 and 802.11 frame

I'm new to networking world. So please bear with me.

My Questions:

1. How do we send TCP/IP in a 802.3 frame? My understanding is that we have to incorporate the 802.3 LLC layer. The DSAP and SSAP in the LLC layer will provide information of the type of data inside the Information field of the LLC layer. Is this correct? Can we specify DSAP to tell that the information field inside the LLC is a TCP/IP packet? OR Do we need to use Ethernet-SNAP for the LLC layer before putting the TCP/IP?

2. What is the difference and the significance of DSAP, SSAP, and Ethernet Type field inside LLC layer? My understanding is that the DSAP and SSAP is used for specifying the receiving and the sending network layer process respectively. What does it mean by network layer process? The actual application? The process ID of the applications? Why do we even need DSAP and SSAP? Isn't the information about the protocol type of the data field is enough?

3. According to LLC (Logical Link Control) (Linktionary term), the LLC layer can be used to forward packet to the appropriate network adapter (in a case of a server with many network adapters). Does this mean with Ethernet version II we can't appropriately select a network adapter for transmission? Can someone explain to me the role of LLC? why LLC is important (other than the fact that LLC provide information about the type of packet of the actual data).

4. The Access Point and the WNIC will automatically convert the 802.11 frame into either 802.3 or Ethernet II frame. How does the WNIC knows what kind of frame type should it convert the 802.11 frame into?

5. I did some packet capturing on my wireless network with wireshark. Why is most of the packet that I see is Ethernet II? I thought the 802.3 is the de facto standard?

6. Who wraps the IP datagram with MAC layer? My understanding is that the MAC layer added by the network card controller (OSI Layer 2). How does this work? Does the OS tell the NIC (through the Driver) the destination MAC and the type of packet to the NIC? And the the NIC will placed the same information to the IP datagram?

Thanks in advance.

Lukas

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LEARN ABOUT DEBIAN

ng_atmllc

NG_ATMLLC(4)						   BSD Kernel Interfaces Manual 					      NG_ATMLLC(4)

NAME

     ng_atmllc -- ATM LLC netgraph node type

SYNOPSIS

     #include <netgraph/ng_atmllc.h>

DESCRIPTION

     The atmllc node type translates frames in to and out of ATM LLC encapsulation, as specified by RFC 1483.  In LLC encapsulation the protocol
     of a given protocol data unit (PDU) is specified by an IEEE 802.2 LLC header, possibly followed by an IEEE 802.1a SubNetwork Attachment Point
     (SNAP) header.  This node currently handles the Ethernet and FDDI protocols.

     The node transmits and receives ATM PDUs on the atm hook.	Received PDUs are decoded and forwarded to the ether or fddi hooks as appropriate.
     Data received on the ether or fddi hooks are assumed to be full Ethernet or FDDI packets as appropriate and are encapsulated into a PDU and
     transmitted via the atm hook.

HOOKS

     This node type supports the following hooks:

     atm     ATM connection.  Typically, this hook would be connected to a ng_atm(4) node, which handles transmission of ATM PDUs over an ATM
	     device.

     ether   Ethernet connection.  This hook sends and receives Ethernet frames.  This would normally be connected to an ng_eiface(4) node if in
	     use.

     fddi    FDDI connection.  This hook sends and receives FDDI frames.

CONTROL MESSAGES

     This node type supports the generic control messages.

SHUTDOWN

     This node shuts down upon receipt of a NGM_SHUTDOWN control message, or when all hooks have been disconnected.

SEE ALSO

     netgraph(4), ng_atm(4), ng_eiface(4), ngctl(8)

     J. Heinanen, Multiprotocol Encapsulation over ATM Adaptation Layer 5, RFC 1483.

AUTHORS

     Benno Rice <benno@FreeBSD.org>

BSD
								   March 8, 2004							       BSD

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