Chapter1NetManagement.txt

To establish an open, flexible and standard networking software architecture which would be used as a framework to guide the compatible implementation of protocols and technology

No functionality is missing. The TCP/IP stack incorporates the functions of the OSI Application, Presentation and Session layers in its Application layer. This is an example of the flexibility of the OSI architecture concept. Another example is the NetWare stack that does not have seven layers.

SNMP is part of the Application layer of the TCP/IP protocol stack

A NMS is set of applications and does not belong to any layer. It can be thought of as residing above the Applications layer and being serviced by that layer

The Protocol Data Unit (PDU) contains the data element provided by the application and an element consisting of the headers created by appropriate protocols in the stack. The header element encapsulates the data element.

An SNMP packet would contain the Application layer, Transport Layer and Network layer and Network Interface layer headers.

A Web Browser uses the Hypertext Transfer Protocol (HTTP) of the Application Layer

That switch may be configured not to accept packets from a specified hardware address because it is inappropriate for that address to be communicating with the device.

In a switched LAN one can configure Virtual Private Networks (VPNs). These are independent virtual circuits that can transmit and receive data simultaneously without the collisions that would occur in a 10BASE2 LAN under such circumstances.

No they are not always layer-2 devices these days. The architecture of some switches enables hardware, network and transport layer headers to be examined before switching the PDU to the destination device.

Hubs enable the devices on the LAN to be connected directly to a central location which provides easy access for network configuration.

The IEEE 802.3 implements the Carrier Sense Multiple Access with Collision Detection (CMSA/CD) specification. This specification takes into account signal loss and signal transit time between devices. To meet the criteria determined by values of these parameters, two devices can be no further than 200 meters apart. Thus no device can be connected to the hub with a 10BASET cable that is longer than 100 meters.

The bridge table maps the source address of a packet received by the bridge to the port from which the packet was received. This enables the bridge to drop packets that are addressed to a device on the same segment. The result is the only packets whose destination is a device on the other segment are transmitted, greatly reducing unnecessary traffic.

Switch tables map destination addresses to the port to which the destination device is attached.

Routing tables map destination network addresses to port numbers

The Ethernet II frame contains a Type field that follows the Source Address field. This field specifies the first protocol header in the Data field. For TCP/IP, this is usually the network layer protocol IP. The IEEE 802.3 frame has two fields that follow the Source Address field before the Data field. The first is the Length field and the second is the LLC field. The LLC field contains the Logical Link Control header that enables reliable communication on a single network. The length field is the number of bytes in the LLC and Data fields.

The NDIS makes it possible for multiple media specifications (e.g. Ethernet II) to be compatible with the TCP/IP protocol stack. If the media driver is written to the NDIS standard, it will interface correctly with the Network Interface layer.