A group of protocols form a protocol suite. A particular suite of protocols is implemented in a particular type of network or used by a vendor for all its products.
Primary Protocols:
NetBEUI
NetBIOS Extended User Interface (NetBEUI) is a Microsoft proprietary non-routable protocol. It is usually used in single LANs comprising one to two hundred clients. NetBEUI was developed by IBM for its LAN Manager product and has been adopted by Microsoft for its Windows NT, LAN Manager, and Windows for Workgroups products. This protocol uses Network Basic Input/Output System (NetBIOS) names to identify the computers on a network.
The main advantages of NetBEUI are listed below:
- It is a high-speed protocol for small networks.
- It is easy to install.
- It provides reliable error protection.
- It provides good performance over slow connections.
- It is easy to configure.
The main disadvantage of this protocol is that it is not routable, so it cannot be used in large networks. It is a broadcast based protocol and can, therefore, cause network congestion if used in large networks.
IPX/SPX
Internet Packet Exchange/Sequenced Packet Exchange (IPX/SPX) is a protocol suite used by Novell NetWare clients to connect to a NetWare server. IPX/SPX is a routable protocol. It is supported by Microsoft operating systems. IPX/SPX can be used for both large and small networks. The Internet does not use this protocol.
IPX addresses consist of hexadecimal numbers that are divided into two parts. The first part represents the address of the network, and the second part represents the MAC address of the workstation or node, which is present on the network card. An example of an IPX address is: 0ADB33CE : 0003EF8D005CE. In this protocol suite, names are assigned only to servers, and the workstations use their respective IPX addresses.
The protocols that constitute this protocol suite are
- Internetwork Packet Exchange (IPX): IPX is a packet or datagram protocol that is used to send messages in packets over the network. It is a connectionless protocol for network route selection, addressing of logical networks, and related connection services. IPX operates at the Network and Transport layers of the OSI model.
- Sequenced Packet Exchange (SPX):Unlike IPX, it is a connection-oriented protocol, which guarantees the delivery of the message in the order in which they were sent over the network. It works on the Transport layer of the OSI model.
- Netware Link State Protocol (NLSP): This protocol is used to exchange routing information in the network.at Network layer of the OSI model.
- Routing Information Protocol (RIP):This is a routing protocol that determines the smallest route to transfer the message packets between the sender and the receiver in the network. It works at the Network layer of the OSI model.
- Service Advertising Protocol (SAP):It is used to announce network services, such as print and file services, by the systems that provide these services. Along with the services, it also announces their addresses on the network. SAP operates at the Application, Presentation, and Session layers of the OSI model.
NWLink
NWLink is a standard network protocol that supports routing. It is the Microsoft equivalent of Novell's IPX/SPX protocol. NWLink provides connectivity between Windows and Novell computers. It can support NetWare client/server applications, where NetWare-aware Sockets-based applications communicate with IPX/SPX Sockets-based applications.
AppleTalk
AppleTalk is the Apple's proprietary protocol suite for Macintosh network communications. It uses the services built into the operating system to provide a multi-layer, peer-to-peer architecture. It has very limited support on other platforms. Windows 2000 versions support the AppleTalk protocol. This protocol suite comprises the following protocols:
- AppleShare: This is an Application layer protocol, which supports file and print sharing.
- Apple Talk Filing Protocol (AFP): This protocol facilitates file sharing on the network. It operates at the Presentation and Application layers of the OSI model.
- Printer Access Protocol (PAP): It provides printing services on the network. PAP operates at the Session layer of the OSI model.
- Apple Talk Data Stream Protocol (ADSP): It is a connection-oriented protocol that helps establish a connection between the network devices. This protocol works at the Session and Transport layers of the OSI model.
- Apple Talk Session Protocol (ASP): This protocol is used to establish a connection and also to disconnect when the message is sent between various devices on the network. It operates at the Session layer of the OSI model.
- Routing Table Maintenance Protocol (RTMP): It maintains the routing tables on a network. It operates at the Transport layer of the OSI model.
- Ether Talk Link Access Protocol (ELAP): It is compatible with the Ethernet Protocol. ELAP operates at the Data Link layer of the OSI model.
- Token Talk Link Access Protocol (TLAP): This protocol operates at the Data Link layer of the OSI model and is compatible with the Token Ring Protocol.
- Apple Talk Address Resolution Protocol (AARP): This protocol maps the Apple Talk addresses to the physical Token Ring and Ethernet addresses. It operates at the Network layer of the OSI model.
- Zone Information Protocol (ZIP): In a Macintosh network, the network devices are divided into logical groups known as Zones. This protocol is used to divide the network devices into logical zones. It operates at the Session layer of the OSI model.
The following table shows the layers of the OSI model at which these protocols operate:
| Layers of OSI model |
Apple Talk Protocols |
| Application layer |
AppleShare and Apple Talk Filing Protocol |
| Presentation layer |
Apple Talk Filing Protocol |
| Session layer |
Apple Talk Data Stream Protocol, Apple Talk Session Protocol, Printer Access Protocol, and Zone Information Protocol |
| Transport layer |
Apple Talk Transaction Protocol, Name Binding Protocol, and Routing Table Maintenance Protocol |
| Network layer |
Apple Talk Address Resolution Protocol and Datagram Delivery Protocol |
| Data-Link layer |
Ether Talk Link Access Protocol and Token Talk Link Access Protocol |
The Apple Talk address consists of two parts: the node address, which is of 8 bits in length, and the network address, which is of 16 bits. So a typical Apple Talk address is a 24 bit decimal number. An example of the Apple Talk address can be 5.79, in which number 5 represents the network address, and 79 represents the node address. The network address is assigned by the network administrators, and the node address is a randomly generated number, which is assigned automatically at the time of the inclusion of the device on the network.
TCP/IP
Transmission Control Protocol/Internet Protocol (TCP/IP) is a suite of standard protocols that govern how data passes between networks. It can be used to provide communication between the basic operating systems, on local and wide-area networks (WANs). TCP/IP is considered as the primary protocol suite for the Internet and the World Wide Web.
The description of the primary protocols in the suite is as follows:
| Protocol Name |
Description |
| IP |
Internet Protocol (IP) is a connectionless network-layer protocol that is the primary carrier of data on a TCP/IP network. |
| TCP |
Transmission Control Protocol (TCP) is a reliable, connection-oriented protocol operating at the transport layer. This protocol can transmit large amounts of data. Application-layer protocols, such as HTTP and FTP, utilize the services of TCP to transfer files between clients and servers. |
| UDP |
User Datagram Protocol (UDP) is a connectionless, unreliable transport-layer protocol. UDP is used primarily for brief exchange of requests and replies. |
| Telnet |
Telnet is a protocol that enables an Internet user to log onto and enter commands on a remote computer linked to the Internet, as if the user were using a text-based terminal directly attached to that computer. |
| FTP |
File Transfer Protocol (FTP) is a primary protocol of the TCP/IP protocol suite, used to transfer text and binary files between computers over a TCP/IP network. |
| SMTP |
Simple Mail Transfer Protocol (SMTP) is used for transferring or sending e-mail messages between servers. |
PPP:Point-to-Point Protocol (PPP) is a set of industry-standard framing and authentication protocols included with Windows remote access to ensure interoperability with third-party remote access software. It is a data link-layer protocol designed to create a direct connection between two computers, typically using telephone lines.
POP3:Post Office Protocol version 3 (POP3) is a protocol used for retrieving e-mail messages. The POP3 servers allow access to a single Inbox in contrast to IMAP servers that provide access to multiple server-side folders.
IMAP:Internet Message Access Protocol (IMAP) is a protocol for receiving e-mail messages. It allows an e-mail client to access and manipulate a remote e-mail file without downloading it to the local computer. It is used mainly by the users who want to read their e-mails from remote locations.
PPTP:Point-to-Point Tunneling Protocol (PPTP) is an encryption protocol used to provide secure, low-cost remote access to corporate networks through public networks such as the Internet. Using PPTP, remote users can use PPP-enabled client computers to dial a local ISP and connect securely to the corporate network through the Internet.
HTTP:Hypertext Transfer Protocol (HTTP) is a client/server TCP/IP protocol used on the World Wide Web (WWW) to display Hypertext Markup Language (HTML) pages. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when a client application or browser sends a request to the server using HTTP commands, the server responds with a message containing the protocol version, success or failure code, server information, and body content, depending on the request. HTTP uses TCP port 80 as the default port.
HTTPS: Hypertext Transfer Protocol Secure (HTTPS) protocol is a protocol used in the Uniform Resource Locator (URL) address line to connect to a secure site. If a site has been made secure by using the Secure Sockets Layer (SSL), HTTPS (instead of HTTP protocol) should be used as a protocol type in the URL.
ARP: Address Resolution Protocol (ARP) is a network maintenance protocol of the TCP/IP protocol suite. It is responsible for the resolution of IP addresses to media access control (MAC) addresses of a network interface card (NIC). The ARP cache is used to maintain a correlation between a MAC address and its corresponding IP address. ARP provides the protocol rules for making this correlation and providing address conversion in both directions. ARP is limited to physical network systems that support broadcast packets.
ICMP: Internet Control Message Protocol (ICMP) is a maintenance protocol and is normally considered a part of the IP layer. ICMP messages are encapsulated within IP datagrams, so that they can be routed throughout an internetwork.
Internet Message Access Protocol 4 (IMAP4) It is an e-mail message retrieval protocol that allows e-mail clients to retrieve e-mail messages from e-mail servers. IMAP4 has the following advantages over the POP3 protocol:
- IMAP4 can be used to download only specific mails from the mail server, while POP3 downloads all the mails from the mail server at a time.
- IMAP4 can download only a part of the message (e.g., the header) initially. Then depending upon the user, the entire message can be downloaded afterwards. However, POP3 downloads the entire message at a time.
- IMAP4 only marks a message as deleted as soon as it is being read. The message will then be deleted as soon as the user logs off, or sends the EXPUNGE command to the mail server.
- IMAP4 supports server side storage. Hence, the location of the user is insignificant. However, POP3 uses a local client application to read the mails.
- Since IMAP4 stores messages on the server side, the user does not have to bother about fault tolerance and system crashes. When the POP3 protocol is used, the messages once downloaded from the server are stored locally and can be lost if the local system crashes.
- IMAP4 allows a user to create multiple mailboxes on multiple servers under the same user name. The user can personalize these mailboxes for receiving specific kinds of mails in each mailbox. However, POP3 allows only a single user account to be configured.
- Changes made to a mail are propagated to the IMAP4 server. This feature is not available under POP3 protocol.
However, there are some disadvantages of IMAP4 over the POP3 protocol, which are as follows:
- If the connection with the mail server drops while reading a mail, it has to be re-established. On the other hand, POP3 downloads the entire mail at a time. Hence, if the connection with the mail server is dropped at the time of reading a mail, it does not affect the reading.
- The POP3 protocol is mostly supported by the commercially available mail servers.
- Since the mails in IMAP4 are stored on the server, the space storage management is a primary concern on such mail servers.
IP Addressing
IP Addresses are used to uniquely identify the computers in a network, so each computer must have its own unique IP address. An IP address consists of two parts: a network identifier and a host identifier. The network identifier denotes the type of network, and the host identifier is a unique number of a particular computer. So in a particular type of network, each node has the same network id and a host id, which are unique.
The type of IP address also depends on the subnet mask, which is used to determine which part of the IP address denotes the network id and which part is the host id. For example, if the IP address is 192.168.1.200 and the subnet mask is 255.255.255.0, the network id will be 192.168.1 and the host id will be 200. In the same way, if the subnet mask is 255.255.0.0, the network id will be 192.168 and the host id will be 1.200. If the subnet mask is 255.0.0.0, the network id will be 192 and the host id will be 168.1.200.
There are two versions of IP addressing, the commonly used IPv4 and the latest version known as IPv6. They have been discussed in detail in the following paragraphs.
IPv4
IP Address
In this version of IP addressing, an IP address is of 32 bits in length, and is divided into four 8 bit decimal values known as octets. In these types of IP addresses, the leftmost bit has the value of 128, which is followed by 64, 32, 16, 8, 4, 2, and 1. An IP address can have values from 0 to 255 because each bit can be either a 0 or a 1. So if all the bits are 1, the value will be 255; and if all the bits are 0, the value will be 0.
Subnet Mask
A subnet mask determines which part of the IP address denotes the network id and which part is the host id. It is also a 32-bit number, which is expressed in decimal format. The subnet mask is assigned according to the class of IP address used.
IP Address Classes
The Internet Assigned Number Authority registers the IP addresses used in the networks to ensure their uniqueness. IP addresses have been divided into five groups or classes known as IP Address classes. Each class of IP address has a particular subnet mask associated with it. The five classes of IP addresses are class A, B, C, D and E, in which class D is reserved for multicast addressing and class E is reserved for future use. So only classes A through C are used for assigning IP addresses to client computers.
- In class A addresses, only the first octet is used to define the network id, and the rest are used for the host id. It has the address range from 1 to 126 and so it can have only 126 numbers of networks. The number of hosts possible in these types of networks is 16,777,214. It uses the subnet mask 255.0.0.0.
- In class B networks, the first two octets represent the network id and the rest are the host id. It has a range of 128-191 and can have 16384 networks with 65,534 hosts. The standard subnet mask assigned to these IP addresses is 255.255.0.0.
- In class C addresses, the first three octets are used to represent the network id. It has a range of 192-223 and can have 2,097,152 networks with 253 hosts. The subnet mask associated with it is 255.255.255.0.
- Class D addresses have an address range of 224-239, and class E addresses have an address range of 240-255.
Default Gateway
Default gateway is a TCP/IP configuration option, used to communicate with TCP/IP nodes on remote network segments. At least one interface must be configured with the IP address of a default gateway.
IPv6
The current version of IP addressing (i.e., IPv4) has its limitations. With the fast increasing number of the networks and the expansion of the World Wide Web, the IP addresses allotted are finishing fast and the need for more network addresses has arisen. IPv6 can solve this problem, as it uses a 128-bit address that can produce a lot more IP addresses. These addresses are hexadecimal numbers, made up of eight octet pairs. An example of an IPv6 address can be 45CF: 6D53: 12CD: AFC7: E654: BB32: 543C.
Subnetting
Subnets are subdivisions of an IP address network, used for creating smaller broadcast domains and for better utilization of the bits in the host ID. Through subnetting, the host id portion of an IP address can be used to create more networks than by using the default subnet mask.
Suppose that a company has been assigned a Class C IP address 200.1.1.0, and the standard subnet mask is 255.255.255.0. This means that the network id will be 200.1.1 and the total number of hosts will be 254. The company has two departments: production and sales. Members of the production department do not need to access the computers of the sales department. So it is better to have separate networks for both the departments for better security and manageability. Through subnetting, the bits from the host id portion can be used to create more networks, which will work as separate networks.
IP Addressing Methods:
Static Addressing
In static addressing, every computer is assigned an IP address manually. It is not preferred in large networks, which have lots of hosts, because the chance of assigning duplicate addresses will be more. This will result in a conflict of IP addresses and deterioration of the speed. Also it is time consuming, as every system is configured manually and if some changes are to be made afterwards, it will consume a lot of time doing it manually for every computer.
Dynamic Addressing
In this type of addressing scheme, the IP addresses are assigned automatically by the use of Dynamic Host Configuration Protocol (DHCP) to all the computers in the network. This results in much less burden on the network administrator and faster configuration of the network. This type of addressing needs a DHCP server, to which a range of IP addresses, is allotted. The DHCP server automatically assigns any address from the range of IP addresses defined to the workstations on the network.
APIPA
Automatic private IP addressing (APIPA) is a feature of Windows XP TCP/IP that configures a unique IP address for each computer on a network when the TCP/IP protocol is configured for dynamic addressing and a DHCP server is not available or offline. The key function of APIPA is to allow resources to be available even if the DHCP server is offline. APIPA addresses are always in the range of 169.254.0.1 and 169.254.255.254 and use a subnet mask of 255.255.0.0.
When a user configures a TCP/IP connection to obtain an IP address automatically, by default the computer tries to find a DHCP server for obtaining the address. The user obtains the address if the computer finds the DHCP server. If it does not find the DHCP server, the computer uses APIPA to configure a unique IP address for the computers of a network. Since APIPA does not offer a gateway address, it can never be used on the Internet, and the clients using APIPA cannot access resources outside the local subnet.
About the Author:
uCertify was formed in 1996 with an aim to offer high quality educational training software and services in the field of information technology to its customers. uCertify provides exam preparation solutions for the certification exams of Microsoft, CIW, CompTIA, Oracle, Sun and other leading IT vendors. To know more about uCertify, please visit www.ucertify.com/ | |
