2-2 Protocols and Standards

2.5 Identify the components and structure of IP (Internet Protocol) addresses (IPv4, IPv6) and the required setting for connections across the Internet.

An IP is a 32-bit number comprised of a host number and a network prefix, both of which are used to uniquely identify each node within a network. A shortage of available IP addresses has prompted the creation of an addressing scheme known as Classless Inter-Domain Routing (CIDR). Among other capabilities, CIDR allows one IP address to designate many unique IP addresses within a network. In addition, the current version of the IP address, IPv4, is being upgraded to IPv6. The latter uses a 128-bit address, allowing for 2128 total IP addresses, as opposed to IPv4's 232.

> Internet Protocol version 4

Is the fourth iteration of the Internet Protocol (IP) and it is the first version of the protocol to be widely deployed. IPv4 is the dominant network layer protocol on the Internet and apart from IPv6 it is the only protocol used on the Internet.

IPv4 is a data-oriented protocol to be used on a packet switched internetwork (e.g., Ethernet). It is a best effort protocol in that it doesn't guarantee delivery. It doesn't make any guarantees on the correctness of the data; it may result in duplicated packets and/or packets out-of-order.

> Internet Protocol version 6 (IPv6)

A network layer protocol for packet-switched internetworks. It is designated as the successor of IPv4, the current version of the Internet Protocol, for general use on the Internet.

The main improvement brought by IPv6 (Internet Protocol version 6) is the increase in the number of addresses available for networked devices, allowing, for example, each mobile phone and mobile electronic device to have its own address. IPv4 supports 232 (about 4.3 billion) addresses, which is inadequate for giving even one address to every living person, let alone supporting embedded and portable devices. IPv6, however, supports 2128 addresses; this is approximately 5×1028 addresses for each of the roughly 6.5 billion people alive today.

2.6 Identify classful IP (Internet Protocol) ranges and their subnet masks (For example: Class A, B and C).

Systems that have interfaces to more than one network require a unique IP address for each network interface. The first part of an Internet address identifies the network on which the host resides, while the second part identifies the particular host on the given network. This creates the two-level addressing hierarchy.

The leading portion of each IP address identifies the network prefix. All hosts on a given network share the same network prefix but must have a unique host number. Similarly, any two hosts on different networks must have different network prefixes but may have the same host number.

Address Class	Decimal Notation Ranges
Class A Class B Class C	1.xxx.xxx.xxx through 126.xxx.xxx.xxx 128.0.xxx.xxx through 191.255.xxx.xxx 192.0.0.xxx through 223.255.255.xxx

The “xxx” represents the host number field of the address that is assigned by the local network administrator.

Class A - addresses are intended for very large networks and can address up to 16,777,216 (224) hosts per network. The first digits of a Class A addresses will be a number between 1 and 126, the network ID start bit is 0 and default subnet mask is 255.0.0.0

Class B - addresses are intended for moderate sized networks and can address up to 65,536 (216) hosts per network. The first digits of a Class B address will be a number between 128 and 191, the network ID start bit is 10 and the default subnet mask is 255. 255.0.0

Class C - intended for small networks and can address only up to 254 (28-2) hosts per network. The first digits of a Class C address will be a number between 192 and 223, the network ID start bit is 110 and their default subnet mask is 255. 255. 255.0

Basic Class A, B, and C Network Address's

Class A		Class B		Class C
Router A 10.10.0.0		Router B 128.28.0.0		Router C 192.28.0.0
Switch 10.10.0.1		Switch 128.28.0.1		Switch 192.28.0.1
10.10.0.2		128.28.0.2		192.28.0.2

2.7 Identify the purpose of subnetting.

A subnet mask is used to mask a portion of the IP address, so that TCP/IP can tell the difference between the network ID and the host ID. TCP/IP uses the subnet mask to determine whether the destination is on a local or remote network.

Advantages of subnetting a network include the following:

• Reducing network congestion by limiting the range of broadcasts using routers
• Enabling different networking architectures to be joined

2.8 Identify the differences between private and public network addressing schemes.

> Public IP Addresses

For a computer to be visible on the Internet, it must be reachable through a public IP address. The IANA assigns ranges of public IP addresses to organizations that can then assign IP addresses within those ranges to individual computers. This prevents multiple computers from having the same IP address.

The public IP address can be assigned through a Dynamic Host Configuration Protocol (DHCP) server, configured manually, or provided by an Internet service provider (ISP).

> Authorized Private IP Addresses

The IANA has reserved a certain number of IP addresses that are never used on the global Internet. These private IP addresses are used for networks that do not want to directly connect to the Internet but nevertheless require IP connectivity. For example, a user wanting to connect multiple Windows based computers in a home network can use the Automatic Private IP Addressing (APIPA) feature to allow each computer to automatically assign itself a private IP address. The user does not need to configure an IP address for each computer, nor is a DHCP server needed.

Computers on a network using authorized private IP addressing can connect to the Internet through the use of another computer with either proxy or network address translator (NAT) capabilities.

> Unauthorized Private IP Addresses

It is possible, when there is an absolute certainty that your network will never access the Internet, to assign to a node a 32-bit unauthorized private IP address of your choosing. Keep in mind that if any Internet connectivity is ever established with any node on your network, these unauthorized private IP addresses could generate significant problems that would require you to immediately change the IP address of every node that you had assigned in this manner.

2.9 Identify and differentiate between the following IP (Internet Protocol) addressing methods:

> Static / Dynamic

An IP network is somewhat similar to the telephone network in that you have to have the phone number to reach a destination. The big difference is that IP addresses are often temporary (dynamic).

Each device in an IP network is either assigned a permanent address (static) by the network administrator or is assigned a temporary address (dynamic) via DHCP software. Routers, firewalls and proxy servers use static addresses as do most servers and printers that serve multiple users. Client machines may use static or dynamic IP addresses. The IP address assigned to your service by your cable or DSL Internet provider is typically dynamic IP. In routers and operating systems, the default configuration for clients is dynamic IP.

> Self-assigned (APIPA (Automatic Private Internet Protocol Addressing))

Automatic Private IP Addressing (APIPA) is a feature of Windows-based operating systems (included in Windows 98, ME, 2000, and XP) that enables a computer to automatically assign itself an IP address when there is no Dynamic Host Configuration Protocol (DHCP) server available to perform that function.

Using APIPA, a Windows based client assigns itself an IP address from a range reserved for authorized private class B network addresses (169.254.0.1 through 169.254.255.254), with a subnet mask of 255.255.0.0. A computer with an authorized private address cannot directly communicate with hosts outside its subnet, including Internet hosts. APIPA is most suitable for small, single-subnet networks, such as a home or small office. APIPA is enabled by default if no DHCP servers are available on the network.

Note APIPA assigns only an IP address and subnet mask; it does not assign a default gateway, nor does it assign the IP addresses of DNS or WINS servers. Use APIPA only on a single-subnet network that contains no routers. If your small office or home office network is connected to the Internet or a private intranet, do not use APIPA.

2.10 Define the purpose, function and use of the following protocols used in the TCP / IP (Transmission Control Protocol / Internet Protocol) suite:

> TCP (Transmission Control Protocol)

Transmission Control Protocol, A connection based Internet protocol responsible for breaking data into packets, which the IP protocol sends over the network. IP is located at the TCP/IP Internet layer which corresponds to the network layer of the OSI Model. IP is responsible for routing packets by their IP address.

IP is a connectionless protocol. which means, IP does not establish a connection between source and destination before transmitting data, thus packet delivery is not guaranteed by IP. Instead, this must be provided by TCP. TCP is a connection based protocol and, is designed to guarantee delivery by monitoring the connection between source and destination before data is transmitted. TCP places packets in sequential order and requires acknowledgment from the receiving node that they arrived properly before any new data is sent.

> UDP (User Datagram Protocol)

User Datagram Protocol runs on top of IP and is used as an alternative to TCP. UDP does not, however, provide any error checking for guaranteeing packet delivery. Because UDP is not as complex as TCP, it is also faster. It is often used for broadcast messages and for streaming audio and video. UDP is a connectionless transport protocol.

All upper layer applications that use TCP or UDP have a port number that identifies the application. This enables the port number to identify the type of service that one TCP system is requesting from another.

Some commonly used ports

Port Number	Service
80	HTTP
21	FTP
110	POP3
25	SMTP
23	Telnet

> FTP (File Transfer Protocol)

An Internet standard application-level TCP/IP protocol that can be used for transferring files between hosts on a TCP/IP internetwork.

File Transfer Protocol (FTP) is one of the earliest Internet protocols, and is still used for uploading and downloading files between clients and servers. An FTP client is an application that can issue FTP commands to an FTP server, while an FTP server is a service or daemon running on a server that responds to FTP commands from a client. FTP commands can be used to change directories, change transfer modes between binary and ASCII, upload files, and download files.

> SFTP (Secure File Transfer Protocol)

SSH File Transfer Protocol or SFTP is a network protocol that provides file transfer and manipulation functionality over any reliable data stream. It is typically used with the SSH-2 protocol to provide secure file transfer, but is intended to be usable with other protocols as well. The sftp program provides an interactive interface similar to that of traditional FTP clients.

> TFTP (Trivial File Transfer Protocol)

Trivial File Transfer Protocol is a file transfer protocol that transfers files to and from a remote computer running the TFTP service. TFTP was designed with less functions than FTP.

> SMTP (Simple Mail Transfer Protocol)

Simple Mail Transfer Protocol, is used to transfer messages between two remote computers. It is used on the Internet, and is part of the TCP/IP protocol stack.

> HTTP (Hypertext Transfer Protocol)

Hypertext Transfer Protocol is the underlying protocol for the World Wide Web. HTTP defines how all resources on the web are transferred and what action web servers and browsers should take in response to commands.

HTTP is a "stateless" protocol, meaning each command is executed independently, without any knowledge of the commands that came before it.

> HTTPS (Hypertext Transfer Protocol Secure)

The secure hypertext transfer protocol is a communications protocol designed to transfer encrypted information between computers over the World Wide Web. HTTPS is HTTP using a Secure Socket Layer (SSL). A secure socket layer is an encryption protocol invoked on a Web server that uses HTTPS. Most implementations of the HTTPS protocol involve online purchasing or the exchange of private information. Accessing a secure server often requires some sort of registration, login, or purchase. The successful use of the HTTPS protocol requires a secure server to handle the request.

> POP3 / IMAP4 (Post Office Protocol version 3 / Internet Message Access Protocol version 4)

Post Office Protocol, used to retrieve e-mail from a mail server. Most e-mail applications use the POP protocol, although some use the newer IMAP (Internet Message Access Protocol).

This older POP2 requires SMTP to send messages. While POP3, can be used with or without SMTP.

> Telnet

Short for Telecommunication Network, a virtual terminal protocol allowing a user logged on to one TCP/IP host to access other hosts on the network.

> SSH (Secure Shell)

Secure Shell or SSH is a set of standards and an associated network protocol that allows establishing a secure channel between a local and a remote computer. It uses public-key cryptography to authenticate the remote computer and (optionally) to allow the remote computer to authenticate the user. SSH provides confidentiality and integrity of data exchanged between the two computers using encryption and message authentication codes (MACs). SSH is typically used to log into a remote machine and execute commands, but it also supports tunneling, forwarding arbitrary TCP ports and X11 connections; it can transfer files using the associated SFTP or SCP protocols. An SSH server, by default, listens on the standard TCP port 22.

> ICMP (Internet Control Message Protocol)

Internet Control Message Protocol is a maintenance protocol in the TCP/IP suite, required in every TCP/IP implementation, that allows two nodes on an IP network to share IP status and error information. ICMP is used by the ping utility to determine the readability of a remote system.

> ARP / RARP (Address Resolution Protocol / Reverse Address Resolution Protocol)

Address Resolution Protocol, is a TCP/IP protocol used to convert an IP address into a physical address, such as an Ethernet address. A host wishing to obtain a physical address broadcasts an ARP request onto the TCP/IP network. The host on the network that has the IP address in the request then replies with its physical hardware address.

> NTP (Network Time Protocol)

The Network Time Protocol is used to synchronize the time of a computer client or server to another server or reference time source, such as a radio or satellite receiver or modem. It provides accuracy's typically within a millisecond on LANs and up to a few tens of milliseconds on WANs.

> SNMP

Simple Network Management Protocol, is a TCP/IP protocol for monitoring networks and network components. SNMP uses small utility programs called agents to monitor behavior and traffic on the network, in order to gather statistical data.

These agents can be loaded onto managed devices such as hubs, NIC's, servers, routers, and bridges. The gathered data is stored in a MIB (management information base).

To collect the information in a usable form, a management program console polls these agents and downloads the information from their MIB's, which then can be displayed as graphs, charts and sent to a database program to be analyzed.

> NNTP (Network News Transport Protocol)

The Network News Transfer Protocol or NNTP is an Internet application protocol used primarily for reading and posting Usenet articles, as well as transferring news among news servers.

> SCP (Secure Copy Protocol)

Secure Copy or SCP is a means of securely transferring computer files between a local and a remote host or between two remote hosts, using the Secure Shell (SSH) protocol.

The protocol itself does not provide authentication and security; it expects the underlying protocol, SSH, to secure this.

The SCP protocol implements file transfers only. It does so by connecting to the host using SSH and there executes an SCP server (scp). The SCP server program is typically the very same program as the SCP client.

> LDAP (Lightweight Directory Access Protocol)

Lightweight Directory Access Protocol, or LDAP, is a networking protocol for querying and modifying directory services running over TCP/IP.

A directory is a set of information with similar attributes organized in a logical and hierarchical manner. The most common example is the telephone directory, which consists of a series of names organized alphabetically, with an address and phone number attached.

An LDAP directory often reflects various political, geographic, and/or organizational boundaries, depending on the model chosen. LDAP deployments today tend to use Domain Name System (DNS) names for structuring the topmost levels of the hierarchy. Deeper inside the directory might appear entries representing people, organizational units, printers, documents, groups of people or anything else which represents a given tree entry.

> IGMP (Internet Group Multicast Protocol)

The Internet Group Management Protocol is a communications protocol used to manage the membership of Internet Protocol multicast groups. IGMP is used by IP hosts and adjacent multicast routers to establish multicast group memberships. It is an integral part of the IP multicast specification, like ICMP for unicast connections. IGMP can be used for online video and gaming, and allows more efficient use of resources when supporting these uses.

> LPR (Line Printer Remote)

The Line Printer Daemon protocol/Line Printer Remote protocol (or LPD, LPR) also known as the Berkeley printing system, is a set of programs that provide printer spooling and network print server functionality for Unix-like systems. The most common implementations of LPD are the official BSD UNIX operating system and the LPRng project. The Common Unix Printing System (or CUPS), which is more common on modern Linux distributions, borrows heavily from LPD.

A printer that supports LPD/LPR is sometimes referred to as a "TCP/IP printer" (TCP/IP is used to establish connections between printers and workstations on a network), although that term seems equally applicable to a printer that supports CUPS.