Local Area Networks , 3rd Edition David A. Stamper

1. Local Area Networks, 3rd EditionDavid A. Stamper Chapter 15 Internet Technology Part 5: Connecting to Other Systems and Networks

2. Chapter Preview In this chapter you will study: • Describe the TCP/IP protocol • Discuss Internet addressing • Describe several protocols used on the Internet • Define a subnet and describe how they are used • List several components of the TCP/IP protocol suite

3. Internet Addresses • Internet addresses are represented in a variety of formats; however, all the formats are ultimately resolved to a 32-bit number known as an IP address. • A 128-bit address is part of a new version of the IP protocol. • On the Internet, all network addresses must be unique. Within a network, all subnet addresses must be unique, and within a subnet all node addresses must be unique. • Currently there are four address classes, A through D; Class E is defined but reserved for future use.

4. Internet Address Class Summary Class Subnets Nodes Comments 27 = 128 214 = 16,000 221 = 2 million 224 = 16 million 216 = 64,000 28 = 256 A B C D Address begins with a 0 bit Address begins with bits 10 Address begins with bits 110 Address begins with bits 1110

5. Subnet Addresses • An Internet address is composed of three basic parts: the class type identifier, the network address, and the node addresses. An installation that was fortunate to have a Class A address space has the potential for approximately 16 million node addresses. It is unlikely that the company would want all these nodes associated with a single network address. Consequently, it is possible for a company to divide the node address range into two parts, a subnet address and a node address within the subnet. • This is accomplished by placing a subnet mask over the local or node address part of the IP address.

6. Internet Node Addresses • Static Addressing • Static addressing means that a node is assigned a permanent IP address. This is common for nodes that are continuously operating on the Internet or network using TCP/IP. • Dynamic Addressing • In dynamic addressing, a node is assigned an Internet address when one is needed. With dynamic addressing, a node will be given any address that is not currently in use. The most common mechanism for dynamically assigning Internet addresses is the dynamic host configuration protocol (DHCP). • Internet Addressing on LANs • If a LAN node also has an IP address, an IP message can be delivered only if the IP address is first translated into MAC address. The protocol that performs this function is called the address resolution protocol (ARP).

7. IP Routing • Devices called routers are responsible for internetwork message forwarding. Each router is connected to two (or more) networks (some routers have more than two ports), and each router port has an address on the attached subnet. • Each router maintains a router table. • Internet Naming Conventions • For most Internet users, the four-octet address representation, called a dotted decimal, is too cumbersome. Therefore, most users substitute a naming convention called a uniform resource locator (URL). A URL uses names and abbreviations that are easier to use and remember than the dotted decimal representation. • Domain names are a hierarchical word-oriented representation of an Internet address.

8. Root Level Domain Names Com edu gov mil net org at au be ca de es fi fr it jp us Commercial enterprise education, for example, a university U.S. government U.S. military network service nonprofit organization Austria Australia Belgium Canada Denmark Spain Finland France Italy Japan United States

9. Domain Name Hierarchy Countries Most General AF AU CA CN DE FR JP...US...ZW COM EDU GOV MIL NET ORG Organizational ABC Acme BGH….XYZ Companies grumpy doc sneezy… bashful Hosts

10. Some URL Protocols http ftp file mailto news Gopher finger hypertext transfer protocol file transfer protocol file access Send mail to a recipient. Access a newsgroup or new article. Use the Gopher text-oriented access. Use utility to access information about a user.

11. IP Routing Algorithm • Source node obtains the destination node’s IP address. • IP protocol builds the IP header and affixes it to the packet • Send packet to router. • Determine the network address of the destination node. • If the network address is this network, use local delivery method and skip remaining steps. • Router consults routing table for network address. • Router sends message out on port addressed to next router • Receiving router decrements time-to-live field. • If time-to-live field is 0, packet is discarded. • Return to step 3.

12. Internet Tools • Finger • Finger is a utility that allows a user to gather information about other network users. For security reasons, some systems do not allow the use of this utility. • Tracert • Tracert allows a user to trace the round trip between the user’s node and another node on the network. • Ping • Ping allows a user to determine if a given system is active on the network. Some versions of Ping also give performance information like number of hops to the system and speed of the links if the system is available. • Talk and Internet Relay Chat (IRC) • Talk is a UNIX utility that allows on user to communicate interactively with another user. Through the talk utility, characters typed at one station are immediately displayed on the other participant’s monitor.

13. Key Upgrades in IPv6 • Expanded Address Space • Currently, the length of Internet addresses is 32 bits. This gives an address space of approximately 4 billion; however, the actual number of addresses available is less than that because some addresses are reserved and because some address ina class may not be used. IPv6 increases the size of the address field to 128 bits; this will allow an address space from 0 to 3x1038. • Quality of Service • To accommodate time-sensitive transmissions like audio and video, IPv6 will institute service categories to prioritize the flow of data. Transmissions declared as real-time will be provided with improved performance. • IP Header Changes • Changes will be necessary to provide for the larger address space and quality of service. • Security and Privacy • IPv6 will allow extensions to the header to provide security capabilities. The extensions will allow a variety of authentication algorithms and allow detection or elimination of known techniques for one node to impersonate another node for sending or receiving packets.

14. Ipv6 Header Format Field Size in Bits Comments Contains protocol version 6 for Ipv6 Message priority Quality-of-service identifier Size in octets of packet following the header Type of header extension, if any Number of hops allowed before datagram is discarded Sender’s IP address Recipient’s IP address Version Priority Flow control Payload length Next header Hop limit Source address Destination address 4 4 24 16 8 8 128 128

15. A Generic Firewall LAN The Internet Generic Firewall Protected Systems

16. A Gateway Firewall The Internet Private Network Gateway Firewall

17. A Screened Subnet Firewall Traffic Not Allowed The Internet Private Network Traffic Allowed Traffic Allowed Screened Subnet (Private)

18. Information Superhighway Uses • A business might use the information superhighway to conduct a conference among employees in different locations. • A software company might use the information superhighway to distribute software directly to customers. • A publishing company might distribute books or magazines directly to readers or perhaps to a local outlet for on-demand printing. • Movies and games may be available on demand. • Education classes at all levels may be available and allow people to learn new skills at their home or office. • Electronic mail and video images may be exchanged. Interactive use of such technologies may give rise to online discussion groups and conferencing.

19. Potential Information Superhighway Implementation Backbone Network Large Business Fiber Optic Cable Fiber Optic Cable Local Distribution Point Coaxial Cable or Twisted-Pair Wires Homes or Small Businesses