2.4. Differentiating Between Network Protocols
Protocols are rules of expected behavior in a given circumstance. Many types of network protocols have been established over time for devices that communicate on a network. It is these rules of expected behavior that allow communication to take place on the network. In order for two devices to communicate effectively, they both must be using the same protocol. In this section, we will examine the most common network protocols.
2.4.1. Critical Information
You should be able to differentiate between the following network protocols in terms of routing, addressing schemes, interoperability, and naming conventions.
2.4.2. IPX/SPX
Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) is a proprietary protocol developed by Novell for NetWare servers. It is a routable protocol that was popular for many years prior to the Internet and the World Wide Web. It has now been largely replaced by TCP/IP to the point that the last few versions of Novell NetWare have used TCP/IP as their default protocol and have allowed IPX/SPX to be used only if needed. IPX/SPX is interoperable with the newer Microsoft operating systems through a protocol called NWLink that was developed by Microsoft to emulate the IPX/SPX protocol.
IPX/SPX is actually a suite of protocols, much like TCP/IP. You should know the major protocols in the IPX/SPX suite. In the following paragraphs, we will discuss the protocols that compose the IPX/SPX suite and their functions.
2.4.2.1.
2.4.2.1.1. IPX
Not surprisingly, Internetwork Packet Exchange (IPX) is one of the major protocols in the IPX/ SPX suite. IPX is primarily responsible for logical network addressing, route selections, and connection services. Route selections are determined by tables created by other protocols in the IPX/SPX suite. IPX is not a routable protocol and it is connectionless; therefore, it works in conjunction with SPX to provide reliability of communication.
IPX addressing is somewhat less complex than IP addressing, since IPX addresses automatically make use of the MAC address on a computer. The IPX address is a routable address that is a combination of an eight-character hexadecimal address, which is automatically assigned by the first server on the network, and the MAC address assigned to the NIC. In addition, the leading zeros in the network portion of the address are generally dropped. For example, a computer that is installed on the 00AC33CD network and has a NIC installed in it with a MAC address of 00-05-1B-04-02-06 would have an IPX address of AC33CD:00051B040206.
2.4.2.1.2. SPX
Sequenced Packet Exchange (SPX) is a routable protocol that adds reliability to IPX. SPX is a connection-oriented protocol, which means that it relies on acknowledgments of packets received. SPX is responsible for fragmenting packets of data and sequencing the data to ensure that the receiving device knows the correct order for the data. SPX is also responsible for reassembling the data on the other side of a connection.
2.4.2.1.3. RIP
Routing Information Protocol (RIP) is responsible for the establishment of routes for IPX addressing. It facilitates communication between routers to calculate the most efficient routes between the source and destination on the IPX/SPX network. This communication is usually based on periodic broadcasts and is an older and less efficient method of calculating routes.
2.4.2.1.4. NLSP
NetWare Link State Protocol (NLSP) is a newer method of calculating routes that can also be used by IPX/SPX networks. It facilitates the communication between routers so that they can each build a map of the network, and then keeps them up to date about the health or "link state" of each of the paths in the network. Routers can use this information to pass packets from the source address to the destination address in the most efficient manner. Since NLSP does not rely on periodic broadcasts, it makes more efficient use of network bandwidth than does RIP.
2.4.2.1.5. SAP
Service Advertising Protocol (SAP) is a protocol used by NetWare to allow systems that provide network services (such as file and print servers) to announce their services and their address to the network. It broadcasts about every 60 seconds. In today's tighter security environment, this type of service advertising may not be as popular as it was before.
2.4.2.1.6. NCP
NetWare Core Protocol (NCP) is a connection-oriented protocol that is primarily responsible for providing a connection between the clients and the services on a Novell network.
2.4.3. NetBEUI
NetBEUI stands for NetBIOS with an Extended User Interface. NetBIOS stands for Network Basic Input Output System. Therefore, NetBEUI stands for Network Basic Input Output System with an Extended User Interface. In other words, the NetBEUI protocol is the NetBIOS service with a GUI interface. NetBEUI uses the NetBIOS names assigned by network administrators. These names can be a maximum of 15 characters in length.
NetBEUI is a simple, fast protocol with a very low overhead. It is self-configuring and is therefore sometimes used for very small networks. Its biggest downfall is that it is not routable and therefore cannot be used by larger networks or on the Internet. Table 2.1 highlights the main characteristics of NetBEUI.
| Routable (Yes or No) | Addressing Schemes | Interoperability | Naming Conventions |
|---|---|---|---|
| No | NetBIOS names assigned by administrator | Not interoperable with other protocols, since it is not routable | Uses NetBIOS names that can be a maximum of 15 characters |
2.4.3.1. AppleTalk
The AppleTalk protocol suite, as you may have guessed, was designed specifically for Apple computer networks. The AppleTalk suite is made up of several protocols. It is not necessary that you know all of the protocols, but you should know about the following main protocols in the suite:
AppleShare
AppleTalk over IP
AppleTalk over IP allows Macintosh clients to connect to an Apple Remote Network Server (ARNS) using IP over the Internet.
Name Binding Protocol (NBP)
NBP maps computer names to Network layer addresses.
EtherTalk Link Access Protocol (ELAP)
ELAP is a communications protocol that is compatible with Ethernet.
TokenTalk Link Access Protocol (TLAP)
TLAP is a communications protocol that is compatible with the IBM Token Ring protocol.
Zone Information Protocol (ZIP)
ZIP divides network devices into logical groups called zones.
AppleTalk node addresses are automatically generated by the computer when it is booted. The network administrator assigns the network number. The full address is a combination of a 16-bit network address followed by an 8-bit node address. Networks with large numbers of users can also use zones to divide the network for administrative purposes.
Because AppleTalk is a proprietary protocol, it is not very interoperable at all. In fact, it can only be used by Macintosh systems. Other systems, such as Microsoft Windows, can provide special support communication with AppleTalk.
AppleTalk is a routable protocol. Routing is enabled by a distance vector routing protocol, much like RIP, called Routing Table Maintenance Protocol (RMTP). RMTP creates and maintains the tables by which routers make decisions.
AppleTalk systems can be assigned names to make it easier for users to locate resources in the network. Naming functionality is provided by NBP, which handles the name resolution of computer names to network addresses. Table 2.2 highlights the main characteristics of AppleTalk.
| Routable (Yes or No) | Addressing Schemes | Interoperability | Naming Conventions |
|---|---|---|---|
| Yes – RTMP | 8-bit network address assigned by administra-tor. 16-bit random node address automatically assigned by system. | Not interoperable with other protocols. Microsoft systems can install special software to communicate. | Naming system functionality is provided by NBP. |
2.4.3.2. TCP/IP
In the late 1970s and early 1980s, the Department of Defense needed to develop a reliable system of communication for its mainframe computers. The Advanced Research Projects Agency (ARPA) began to experiment with communications protocols and developed a network system known as ARPANET. The original ARPANET protocol was NCP but, due to limitations, another protocol was soon needed. Transmission Control Protocol/Internet Protocol (TCP/IP) was developed to be a robust, reliable, and scalable protocol. It soon became the protocol of choice for the ARPANET, which eventually grew into what we now know as the Internet.
The TCP/IP suite of protocols includes protocols that work at various layers of the OSI model. We will discuss the details of each of these protocols later in this chapter. TCP/IP is an open standard protocol, which makes it interoperable with all operating systems. In fact, the interoperability of TCP/IP is one of the factors that is largely responsible for its growth.
The IP protocol of the TCP/IP suite is most responsible for the addressing function.
We will discuss IP addressing in detail later in this chapter. In general, each node of a network is identified by a unique address, and so is each network segment. The IP address consists a 32-bit address made up of four sets of eight bits (referred to as octets), which are expressed as dec-imal numbers, such as 192.168.0.1. These addresses can be manually configured by administrators or automatically configured by special servers called Dynamic Host Configuration Protocol (DHCP) servers.
TCP/IP nodes are generally referred to as hosts. They can be referred to by their IP address or by their hostname. Name resolution can take place through a text file (hosts.txt) or a dynamic database referred to as Domain Name System (DNS). We will discuss name resolution services in greater detail later in this chapter.
TCP/IP is fully routable, which makes it perfect for networks of all sizes. The TCP/IP suite contains routing protocols such as Routing Information Protocol (RIP) and Open Shortest Path First (OSPF). RIP is a distance vector protocol and OSPF is a link-state protocol. Distance vector protocols require frequent communication between routers to maintain routing tables. Link-state protocols build a map of the entire topology of a the routers that make up a network and only change the map when a change is made to that topology. Most large net-works use a link-state protocol because of its lower overhead and greater intelligence for routing decisions. Table 2.3 highlights the main characteristics of TCP/IP.
2.4.4. Exam Essentials
Know the routability of each of the major protocols. TCP/IP and IPX/SPX are routable protocol suites. NetBEUI is not a routable protocol. RIP is a routing protocol used for communication between routers to populate routing tables.
Define the addressing schemes of each of the major protocols. You should know the addressing schemes used by the most common protocols. In addition, you should be able to differentiate between the addressing schemes used.
Know the interoperability of each of the major protocols. You should know which of the major protocols are interoperable with other systems. In addition, you should know by what means they can become interoperable.
Know the naming conventions used by each of the major protocols. You should know the naming conventions that are used by each of the major protocols. In addition, you should know about any name resolution mechanisms that they use.