carrier extension is used.) Problem 6.28 Explain how operation of a LAN hub and switch differ. How does the auto- learning switch or bridge know to which port it should send a frame? Problem 6.29 Explain the structure of an IPv4 address. Introduction to Telecommunications Network Engineering Problem 6.30 What is the maximum number of IP hosts in networks with class A, class B, class C, and class D IP addresses, respectively? Problem 6.31 What is the subnetwork mask and how is it used? Problem 6.32 A class B IP address is assigned to a company. There are 12 LANs in its net- work. Define the subnetwork mask and host number ranges in binary, hexa- decimal, and dotted decimal notation for each subnet. How many hosts can exist in each subnet? Problem 6.33 Describe the structure of an IP packet. Explain the purpose of each field in its header. Problem 6.34 What are the main advantages of IPv6 compared with IPv4? Problem 6.35 Explain briefly mobile IP operation. Problem 6.36 What is the ARP and how does it operate? Problem 6.37 What is the RARP land how does it operate? Problem 6.38 What is the purpose of the ICMP? Problem 6.39 What are the host-to-host (or transport) layer protocols of TCP/IP and what are their basic differences? Problem 6.40 Explain the TCP connection setup procedure. Data Communications Problem 6.41 Explain the sliding window principle used by TCP. Why are there different windows for transmission and reception? Problem 6.42 Describe the TCP packet header and explain the purpose of its fields. Problem 6.43 What is the Domain Name Server? Explain its hierarchy and basic operation. Problem 6.44 What is a URL? Describe its structure. Problem 6.45 What is the HTTP? Describe its basic operation. Problem 6.46 What is HTML? For what is it used? Problem 6.47 What are the new features that Java provides for Web page designers? Problem 6.48 What are the main advantages and disadvantages of IP networks compared with PSTN for ordinary telephone service? Problem 6.49 Explain the main goals behind the development o