• CHAPTER 4

1. Distinguish between client pcs and servers. What do you have to add to a Windows 95 or 98 PC to make it a client PC? What do you have to add to a PC to make it a server? What are the elements of a LAN to connect the PCs of a PC network?
Answer -ข้อแตกต่างระหว่าง Client PCs และ Servers คือ
Client PCs เป็นเครื่องที่ตั้งบนโต๊ะทำงานแต่ละคน รับข้อมูลจากเครื่อง Servers ซึ่งเป็นหน้าที่หลักของ Client PCs
Servers เป็นตัวศูนย์กลางที่มีไว้เพื่อให้ Client PCs เชื่อมโยง ซึ่งมีหน้าที่ให้บริการกับ Client PCs ที่ต่างชนิดกันได้
-clientn PCs beginning with Windows 95
-to make pc to a server with server hardware
-to connect the PCs of a PC network with physical and data link layers

2.List the six layers of the hybrid TCP/IP-IEEE framework used for LAN standard. How does it differ from the five-layer TCP/IP-OSI framework introduced in Chapter 1?Which layers are subnet layers? Which layers are implemented by the NIC?
Answer -The six layers of the hybrid TCP/IP-IEEE are Application, Transport, Internet, logical Link Control,Media Access Control and Physical layer
-TCP/IP-OSI framework have 5 layer are Application, Transport, Internet, Data Link, Physical
-Data Link and Physical are subnet
- Physical and Data Link Layer are implemented by the NIC

3. Explain each of the elements of “Ethernet 802.3 10Base-T” and “Ethernet 802.3 100Base-TX.” At what layer are these standards defined? Why are many organizations upgrading from 10Base-T to 100Base-TX? Why is this upgrade easy and inexpensive?
Answer -อธิบายแต่ละส่วนของ Ethernet 802.3 10Base-T และ Ethernet 802.3 100Base-TX คือ
“802.3” standard comes from the 802.3 Working Group that develops all Ethernet standards.
“10” operates at 10 Mbps. The “100” operates at 100 Mbps.
“Base” means baseband transmission.
"T" use ordinaly UTP telephone wire
" TX " like " T " but faster
- definedin physical layer
- beacause easy and inexpensive to upgread from 10 Base-T to 100 Base because the wiring between
station and the hub remains the same

4. When the first bit of a frame reaches the hub, what does the hub do? What is the characteristic of the bus topology at the physical layer?
Answer -That each bit is broadcast to all stations attached to all ports. This includes the station doing the transmission. Sending the bit back to the transmitting station allows the station to confirm that its signal is being retransmitted correctly.
-In Ethernet, station use broadcasting to connect at the physical layer.

5. (From the box “Electrical Signaling”) How does Ethernet 802.3 10Base-T represent a one? Why does it do this instead of representing a one as a simple high or low voltage?
Answer -In Ethernet 10Base-T, this is 10 Mbps. The band rate, in turn, is the number of times per second the line can change state per second.
-In 4B/5B, a high or a low voltage represents a bit for its entire bit period. To prevent loss of synchronization because of a long series of ones and zeros, each five bits transmitted carry four data bits. The 5-bit combinations are chosen to contain at least two line changes in the five bits. This is almost as good as synchronization for every bit.

6. What is media access control? At what layer is it implemented? Explain how Ethernet 802.3 handle access conrol.
Answer -media access control is limitation to one transmission at a time at the physical layer means that shared media networks must have media access control (MAC).

7. All the LAN standards discussed in this chapter are shared media standards. In a shared media network of any type, if you have 200 stations on the network, how many may transmit at a time?
Answer - only one may transmit at a time.

8. Name each of the fields in the Ethernet 802.3 MAC layer frame, including the lengh (in octets) and the pupose of each. What does the receiving NIC do if it detects an error?
Answer -แต่ละ fileds ใน The Ethernet 802.3 MAC layer frame ประกอบด้วย
Preamble------- 7 Octets of 10101010 for synchronization
Start of Frame Delimiter------- 1 Octet of 10101011 to show start of frame
Destination Address------- 6 Octets for address of receiving station
Source Address------- 6 Octets for address of transmitting station
Length------- 2 Octets for length to data field in octets
Data (LLC Frame)------- Data to bedelivered (PDU of next higher layer,LLC)
PAD------- padding if needed to make frame 64 octets long
Frame Check Sequence------- 4 Octets of error checking information
-each NIC vendor is given a large block of addresses by assigning it a unique 24-bit initial sequence. The NIC vendor then assigns a unique 24-bit final sequence to each NIC it produces. This ensures that,across NIC vendors, the default address preset at the factory will be unique for every NIC produced.

9. What is the single logical link control layer standard for all IEEE LANs? What error control options does it offer network administratiors? What is its function other than error control?
Answer -All IEEE LANs look exactly the same to the layer 3 program, regardless of the physical and MAC technology used by the LAN.
-The 802.3 Type 1 option (unacknowiedged connection less service).
-This option does not add error correction at the logical link control layer. It has very low overhead.

10. (From the box “Token-Ring Networks”) Compare Ethernet and token-ring networks in terms of physical layer topology. Compare them in terms of MAC layer media access control. Compare them in terms of LLC layer standards.
Answer เปรียบเทียบ Ethernet และ Token-ring network
-Ethernet uses a bus topology, which is characterized by broadcasting and token-ring network stations connect to access, which are themselves connected in a ring(loop).
-At the MAC layer Ethernet uses CSMA/CD for media access control,token-ring network use token passing to determine when each station may transmit.
-In the term of token-ring network are designed to use 802.2 as the logical link control layer standard

11. One file server uses TCP/IP standards. Another uses IPX/SPX standards. Both operate on an Ethernet LAN. At what layers do they have the same standards? At what layers do they have different standards? Can a client PC communicate with both an IPX/SPX server and a TCP/IP server at the same time?
Answer -In Subnet and application Layer have to same standards.
-At the transport and internet layer have different standards.
-Client pc can communicate with both an IPX/SPX server and a TCP/IP server at the same time.

12. What are the three factors to take into account in deciding how many servers to use to implement a PC network’s services?
Answer -The first type of server on PC networks was the file server. In file service, the server acts like a very large hard disk that is shared by many client PCs.

13. Does file service allow file sharing by several people? What happens if two users try to change the same file at the same time? What are access rights?
Answer -ไม่ใช่ ต้องโดย individual people.
-ถ้าผู้ใช้ 2 คน พยายามเปลี่ยน file และเวลาเดียวกัน โดยผู้ใช้คนแรก จะSave แล้ว Retrieve ไปผู้ใช้คนที่2
-They can even copy fiels between virtual drives on 2different file servers..

14. In print service, why is printing to a remote printer the same for a user as printing to a printer directly attached to the user’s PC? In what good way is it different?
Answer -Because the print service work the same way as printing to a local print.
The output comes into the printer through the parallel port, just as it would if the PC were directly attached to the printer.
-มี Remote Access Servers ใช้ Access server ที่อยู่ไกลๆได้ซึ่งต้องมี Remote Access Software.

15.Distinguish between file server program access and client/server processing in terms of the size of applications that may be executed.
Answer -File server program access limits the size of programs bec
ause these programes must be able to fit on most corporatet PCs, even older underpowered PCs. File server program access has very limited scalability.
-Client/Server processing is platform independent. Because we are talking about Pcnetworking, the client machine will be a PC. However, the server can be a high-end PC, a workstation server, or some other high-end computer. This means that evenon PC networks, where the client machines are PCs, there can be high scalability in applications.