mac头是不是一定要在数据链路层加?

我在看一个中间层驱动源程序时,从ip层收到的包已经有mac头
这是为什么?

windows里好象物理层和数据链路层里的mac子层是和miniport driver划等号的

mac头是由NIC加的，不过如果你要直接写NIC，就要自己加mac头。

和数据链路层是等号！！可是物理层好象不是啊~~~是间接画等号吧！都是调用NDIS和HAL的东西来开发miniport的啊~~那怎么等？他们还在下面！miniport都被隔离了！

mac头都是协议层加的。只有mac crc才是nic加的。

Network Drivers: Windows 2000 DDK
2.1 Windows 2000 Network Architecture and the OSI Model
The Microsoft? Windows? 2000 network architecture is based on the 7-layer networking model developed by the International Standards Organization (ISO). Introduced in 1978, the ISO Open Systems Interconnection (OSI) reference model describes networking as a series of protocol layers with a specific set of functions allocated to each layer. Each layer offers specific services to higher layers while shielding these layers from the details of how the services are implemented. A well-defined interface between each pair of adjacent layers defines the services offered by the lower layer to the higher one and how those services are accessed.

Network drivers under Windows 2000 implement the bottom four layers of this network architecture:

Physical Layer
This is the lowest layer of the OSI model. This layer is involves the reception and transmission of the unstructured raw bit stream over a physical medium. It describes the electrical/optical, mechanical, and functional interfaces to the physical medium. The physical layer carries the signals for all the higher layers.
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Under Windows 2000, the physical layer is implemented by the network interface card (NIC), its transceiver, and the medium to which the NIC is attached.
For network components that use serial ports, the physical layer can also include low-level network software that defines how the serial stream of bits is divided into packets of data.
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我们应该说的是driver和协议对应关系吧。上面这句你怎么理解的？

Data Link Layer
This OSI layer is further divided by Institute of Electrical and Electronics Engineers (IEEE) into two sublayers: LLC and MAC. The LLC sublayer provides error-free transfer of data frames from one node to another. The LLC sublayer establishes and terminates logical links, controls frame flow, sequences frames, acknowledges frames, and retransmits unacknowledged frames. The LLC sublayer uses frame acknowledgement and retransmission to provide virtually error-free transmission over the link to the layers above. The MAC sublayer manages access to the network media, checks frame errors, and manages address recognition of received frames. In the Windows 2000 network architecture, the Logical Link Control sublayer is implemented in the transport driver, while the Media Access Control sublayer is implemented in the network interface card (NIC). The NIC is controlled by a software device driver called the NIC driver. Windows 2000 ships with NIC drivers for a number of popular NICs.
Network Layer
This layer controls the operation of the subnet. It determines the physical path the data should take, based on the following:
network conditions
priority of service
other factors, including routing, traffic control, frame fragmentation and reassembly, logical-to-physical address mapping, and usage accounting
Transport Layer
This layer ensures that messages are delivered error-free, in sequence, and with no loss or duplication. It relieves the higher-layer protocols from any concern with the transfer of data between them and their peers. A minimal Transport Layer is required in protocol stacks that include a reliable Network or Logical Link Control sublayer that provides virtual circuit capability. For example, because the Windows 2000 NetBEUI transport driver includes an OSI-compliant LLC sublayer, its Transport Layer functions are minimal. If the protocol stack does not include an LLC sublayer, and if the Network Layer is unreliable and/or supports datagrams (as with TCP/IP's IP layer or NWLink's IPX layer), the Transport Layer should include frame sequencing and acknowledgment, as well as retransmission of unacknowledged frames.

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In the Windows 2000 network architecture, the Logical Link Control, Network, and Transport layers are implemented by software drivers known as transport drivers, which are sometimes referred to as protocols, protocol drivers, or protocol modules. Windows 2000 ships with TCP/IP, IPX/SPX, NetBEUI, and AppleTalk transport drivers.
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我的理解是从这里来的，看来太片面啦.hoho

Built on Wednesday, June 28, 2000