Just as in the OSI model, the Network Access layer is responsible for framing the packets of information for the underlying topology and merging the data on the wire. The Network Access layer also grabs the frames off the network. If they are for that MAC address or for broadcast/multicast, the Network Access layer passes them up to the appropriate protocol.
Summary
This chapter has provided an overview of Microsoft networking. You have also been introduced to the TCP/IP stack. You have learned that Windows NT (and Microsoft networking) in general fits either the OSI model or the TCP/IP model. NetBIOS has been shown as the main protocol for internal portions of NT networking. You have also learned that a translation layer is used to allow this to run on top of Winsock. The next chapters discuss more of the details for the main layers in the TCP/IP stack.
Test Yourself
1. What are the four main services provided by NetBIOS?
2. What is the unit of communications between a redirector and server in NetBIOS?
3. What are the five main layers in the Windows NT networking architecture? 4. Which of the layers are boundary layers?
5. What is the main advantage of using a layered approach?
6. What are the two main APIs found at the application/file system driver layer? 7. How many redirectors can you add to Microsoft NT?
8. What protocols come with Windows NT?
9. Which protocol is not intended for host-to-host communications? 10. Which of the protocols are not routeable?
11. Which protocol enables you to work with a Novell network? 12. What is a LANA Number?
13. What is the main advantage of NDIS?
14. At the TDI layer, what is created to direct the SMB to the correct protocol? 15. How many layers are there in the OSI reference model? In TCP/IP? 16. What is a socket?
17. Which socket numbers are reserved for services to use? 18. What will use sockets?
19. When you use sockets, how is the data being transferred addressed so that it reaches the correct destination?
20. What is the main difference between TCP and UDP? 21. What are the protocols at the IP layer?
23. For the following IP address and subnet masks, determine the network ID: 145.42.36.45 255.255.0.0 198.53.14.6 255.255.255.0 205.47.18.5 255.255.255.0 75.25.255.42 255.0.0.0 128.45.6.245 255.255.0.0
24. What does ARP do?
25. What address will ARP look for if the host your are communicating with is a local host? For a remote host?
26. What is the purpose of ICMP? 27. When is IGMP used?
Test Yourself Answers
1. The services provided by NetBIOS are: name management, connection- oriented data transfer, connectionless data transfer, and session management. 2. Redirectors and servers talk to each other using SMBs (Server Message Blocks). 3. The five main layers in Windows NT networking architecture are: application/
file system driver, transport driver interface (TDI), protocols, network driver interface specification (NDIS), and adapter card drivers.
4. The TDI and NDIS layers are the boundary layers.
5. The layered approach allows more flexibility as to what can be added to each layer. Developers need only be concerned with communicating with the layer above and the layer below.
6. The two main APIs in Microsoft networking are the NetBIOS API and the WinSock API.
7. As many as you want. System performance might suffer, however, if too many are installed.
8. Windows NT has five protocols: TCP/IP, NWLink (an IPX/SPX-compatible protocol), NetBEUI, AFP, and DLC.
9. The DLC (Data Link Control) protocol is intended for communications between a system and an HP Jetdirect card, or using a 3270 emulation with an IBM mainframe.
10. Both NetBEUI and DLC are not routable.
12. A LANA Number is a Local Area Network Adapter number and it describes a logical link between the protocols and the network cards.
13. NDIS allows multiple protocols to bind (or work with) multiple network cards without having to load multiple instances of either driver.
14. The TDI layer creates a NCB or Network Control Block to move the SMB (as data) to the correct protocol.
15. The OSI model uses seven layers to describe a networking model. The TCP/IP protocol uses only four. The main reason for the difference is increased responsibility at the Application layer and an isolation, and the Network Access layer because TCP/IP is topology-independent.
16. A socket is a number that represents the location of a service. Sockets provide endpoints for communications between two hosts.
17. The first 1,024 sockets are reserved. These are under the control of the Internet Assigned Numbers Authority.
18. All communications over TCP/IP use a socket, including NetBIOS traffic. 19. The addressing includes the IP address, transport protocol (TCP or UDP), and
the port (socket) number to which the data should be delivered.
20. TCP is a connection-oriented transport protocol, meaning that it can guaran- tee delivery of the packet to the other system. UDP is connectionless and delivers data on a “best-effort” basis.
21. At the IP layer, four main protocols are: IP (Internet Protocol), ICMP (Internet Control Messaging Protocol), IGMP (Internet Group Messaging Protocol), and ARP (Address Resolution Protocol).
22. IP must first determine whether the address is a local or remote address. IP performs this function by ANDing the local IP address with subnet mask to determine the local network ID. Then IP will AND the subnet mask with the remote host to determine a pseudo-network address (it might be incorrect). The two network addresses assume the other host is local. Otherwise, it is remote. 23. 145.42.36.45 255.255.0.0 145.42.0.0 198.53.14.6 255.255.255.0 198.53.14.0 205.47.18.5 255.255.255.0 205.47.18.5 75.25.255.42 255.0.0.0 75.0.0.0 128.45.6.245 255.255.0.0 128.45.0.0
24. ARP or Address Resolution Protocol is used to find the hardware (MAC) address of a host you are communicating with.
25. In the case of a local host, ARP attempts to find the host MAC address. In the case of a remote host, ARP finds the address of the default gateway.
26. The Internet Control Messaging Protocol is used to report error conditions of a packets in transit. It can also be used to control the flow of data on the network.
27. Internet Group Messaging Protocol is used to communicate with systems that are multicasting. Multicasting enables one system to send to a special address. Many systems can then receive the same information from that one transmission.