The Barnes & Noble Review
Networking Complete, Second Edition is a broad, useful overview of networking at a price that's hard to beat.
Drawing from the best books in their networking library, Sybex's editors have brought together authoritative coverage of an exceptionally wide range of day-to-day networking techniques and concepts, from network design to maintenance, security to troubleshooting.
Among the highlights: an excellent chapter on preparing for -- and then installing -- a local area network; the principles of network design (written originally for Windows networks but useful in any environment); and two chapters on tracking down network problems (one offering a step-by-step methodology, the other outlining several common scenarios, including ping problems, undelivered email, connectivity trouble, and poor performance. There's also a full chapter on disaster recovery for small-to-midsize companies: planning, effective backups, RAID, clustering, et cetera.
The authors walk you through the basics of building an infrastructure for delivering Internet and intranet services, including setting up DNS, and working with a business ISP. There's also a five-chapter section on security and remote connectivity -- focused primarily on Windows 2000 and NetWare environments, but including some basic guidance for UNIX/Linux servers, as well. Tucked in at the end: a handy 35-page networking glossary.
If you're just starting out with networking, or if you've got a problem to solve and no idea where to start, this book will get you rolling -- and still leave cash in your pocket.
Bill Camarda is a consultant, writer, and web/multimedia content developer with nearly 20 years' experience in helping technology companies deploy and market advanced software, computing, and networking products and services. His 15 books include Special Edition Using Word 2000 and Upgrading & Fixing Networks For Dummies®, Second Edition.
Read an Excerpt
Chapter 5: Major Protocol Suites
This chapter provides a detailed discussion of the most
important of these suites and takes a look at some other
protocols and protocol standards. Although your Networking
Essentials exam will not require that you have mastered much
of this material, a further understanding of protocol suites
broadens your knowledge base as a network administrator.
These are the protocol suites examined in this chapter:
- NetWare IPX/SPX, Novell NetWare's proprietary pro-
- TCP/IP, the nonproprietary protocols that make up the
- AppleTalk, Apple Computer's proprietary protocols,
which began with the Macintosh
Review of Protocols, Models, and Implementations
A protocol is a set of rules for communication. A simple example of a protocol from the realm of human communications is the different ways of
greeting people: should you bow, shake hands, or kiss both cheeks of the
person you're greeting? It depends on where you are and whom you are
greeting. If you make a mistake,you could be misunderstood.
Although in the data communications world protocols are more complex and precise, the same idea holds true. For example, a protocol may
define the shape of a packet that will be transmitted across the network,
as well as all the fields within the packet and how they should be interpreted. Obviously, both the sender and receiver must agree on the exact
way the packet should be formatted in order for communication to occur.
Any protocol product available on the market will necessarily be a protocol
implementation, which means any one company's interpretation of the protocol definition or standard. Therefore, one company may interpret a standard in
a different way than another, which can cause incompatibility.
A protocol suite is a group of protocols that evolved together, whether
created by the same company, as in the case of IBM's SNA, or used in the
same environment, such as the Internet protocol suite. Protocol suites have
definitions for the interface between protocols that occur at adjacent layers
of the OSI model, such as IPX and SPX in the NetWare suite.
NetWare IPX/SPX Protocols
The NetWare protocol suite takes its name from the two main protocols
at the network and transport layers of the OSI model: IPX and SPX.
NetWare was first developed by Novell,Inc., in the early 1980s. Its design was
based on a network developed by Xerox at its Palo Alto Research Center (PARC)
called Xerox Network System (XNS).
The NetWare IPX/SPX protocol suite provides file, print, message, and
application services. This architecture is server-centric because workstations
make requests for file services or other services from the server. To the user
at a workstation, all resources appear local to that workstation. For example, saving a file to a file server on the network is simply a matter of saving it to
drive F (or another mapped drive) in the same way it would be saved to the
user's C hard drive.
The NetWare protocols are modular; you can use them with many different hardware configurations. You can also use other protocols, such as
TCP/IP and AppleTalk, with NetWare, making it very flexible. NetWare,
therefore, is not limited to its proprietary protocols,IPX and SPX. Allowing additional protocols provides more interoperability with other computer systems.
The NetWare protocol suite can be mapped to the OSI model as shown
in Figure 5.1. The following sections discuss the NetWare protocols, organized by their function with respect to the OSI model.
Figure 5.1: The NetWare protocol suite mapped to the OSI model
NetWare Lower-Layer Protocols
NetWare normally runs over standard lower-layer protocols, such as
Ethernet (IEEE 802.3) and Token Ring (IEEE 802.5). The lower-layer
protocol discussed here, MLID, is a proprietary standard for network
interface card drivers.
MLID (Multiple Link Interface Driver)
The MLID protocol operates at the MAC sublayer of the OSI model's data
link layer. It is concerned with medium access and uses these methods:
The MLID is a standard for network drivers. Each type of network
board has a unique MLID driver. The MLID is implemented in software.
A common example is the DOS file called NE2000.COM, written for the
Novell/Eagle NE2000 network card.
- Token passing
The MLID is also called the network driver or LAN driver. Its job is to
communicate directly with the hardware network card. The MLID is independent of upper-layer protocols because of the LSL (link support layer)
module at the LLC sublayer of the data link layer, which acts as an interface between the MLID and network layer protocols.
The interaction between the MLID, LSL, and other components is
specified by the ODI (Open Data-link Interface) specification, a Novell
standard for modular network communications. The ODI specification
allows you to easily configure client software using the same programs,
regardless of the type of network board used. With this architecture only
the MLID changes; before ODI, you needed to create a customized version of the IPX driver for each network card.
NetWare Middle-Layer Protocols
NetWare's middle-layer protocols include the following:
- IPX: Used for transporting packets
- RIP and NLSP: Routing protocols
- SPX: Runs at the transport layer and adds connection-oriented
service when added reliability is required
IPX (Internetwork Packet Exchange)
Novell's main network layer protocol is IPX. It deals with addressing (the
logical network and service addresses), route selection, and connection
services. IPX provides connectionless datagram service, which means
that data is sent over the whole network segment rather than across a
direct connection.IPX is based on the IDP (Internetwork Datagram Protocol) of XNS (Xerox Network System).
Because of its connectionless nature, IPX is not suitable for some
types of network communications. Most of the communication on a network, including workstation connections and printing, uses the SPX protocol, described later in this chapter. Simple IPX is used for broadcast
messages, such as error notifications and time synchronization.
IPX performs dynamic route selections based on RIP tables, which
contain a list of identified and reachable networks. In NetWare 4.1, IPX
is usually implemented by the IPXODI.COM program, which follows the
ODI specification. Earlier NetWare versions used a program called
IPX.COM. As discussed in the section "MLID (Multiple Link Interface
Driver)" earlier in this chapter,before ODI, a custom version of IPX was
required for each type of network card and settings.
RIP (Routing Information Protocol)
RIP is the default protocol NetWare uses for routing. RIP uses the distance-vector route discovery method to determine hop counts. The hop
count is the number of intermediate routers a packet must cross to reach
a particular device.
RIP functions at the network layer of the OSI model, although it has a
service address assigned to it. Because it is a distance-vector routing protocol, RIP periodically broadcasts routing table information across the
internetwork. This can create a bottleneck when the information must be
transmitted over wide area links. For WANs, you should use a link-state
routing protocol instead,such as NLSP.
NLSP (Network Link Services Protocol)
NLSP is another routing protocol that functions at the network layer. NLSP
uses the link-state route discovery method to build routing tables. It is
based on an OSI routing protocol called IS-IS (Intermediate System-to-Intermediate System)....