Network Topology

What is a Topology

The physical topology of a network refers to the configuration of cables, computers, and other peripherals.

The following sections discuss the physical and logical topologies used in networks and other related topics

Peer to Peer
Client Server
Star
Ring
Bus
Mesh
Hybrid
Point to Point
Point to Multi Point
Multi protocol labeling switch
Ad Hoc Mode
Infrastructure Mode

Peer to Peer Topology

Peer to Peer implementations: (10 or less computers to network)



Advantages:
Lower Cost, Easy to setup and good for temporary network setup

Disadvantages:
Limited growth, No central location, Weak Security, Too many passwords

Client Server Topology

Server based implementations: (10 or more computers to network)


Advantages:
Centralized management, Strong Security, Expansion, Flexibility and Create redundant systems

Disadvantages:
Expensive, difficult to implement, and Central Point of failure

Comparing Servers

A Server is a computer or device on a network that manages network resources. Servers are often dedicated, meaning that they perform no other tasks besides their server tasks or non-dedicated meaning they can do many things. On multiprocessing operating systems however, a single computer can execute several programs at once. A server in this case could refer to the program that is managing resources rather than the entire computer.

Types of Servers

File
Print
Application
Database (SQL, Oracle)
Web (HTTP, IIS, Apache)
Mail (MS Exchange)
DNS
DHCP
WINS
Proxy
Gaming (PS3, Xbox Network)
Multimedia (Netflix)
RADIUS
Terminal
SharePoint
Domain
Real Time (CHAT, IM)
FTP
Collaboration (Groupware)
Telnet
Open Source
Virtual (Hypervisor)
List
RAID
E-Commerce
Transaction
Fax
Communication
Stand Alone
Home
Catalog

Star Topology

A star topology is designed with each computer (file server, workstations, and peripherals) connected directly to a central network called a hub or a switch.



Advantages of a Star Topology

• Easy to install and wire.
• No disruptions to the network then connecting or removing devices.
• Easy to detect faults and to remove parts.

Disadvantages of a Star Topology

• Requires more cable length than a linear topology.
• If the hub or concentrator fails, nodes attached are disabled.
• More expensive than linear bus topologies because of

Ring Topology

Ring Topology -All computers or network devices are attached directly to each other in a ring fashion. An example is an FDDI (fiber distributed data interface) network, where all the hubs connect to each other in a ring or a token ring network.


Advantages of a Ring Topology

• Easy to install and wire.
• Equal Access to devices no one computer will use all the bandwidth
• Easy to detect faults and to remove parts.

Disadvantages of a Ring Topology

• Slow since signals goes in sequential order
• If the MSAU or concentrator fails, nodes attached are disabled.
• Single break in cable

Bus Topology

A bus topology consists of a main run of cable with a terminator at each end.  All nodes (file server, workstations, and peripherals) are connected to the linear cable.  10Base is an example of a network that would use a bus topology.

Advantages of a Linear Bus Topology

• Easy to connect a computer or peripheral to a linear bus.
• Requires less cable length than a star topology.
• Cheaper compared to start topology

Disadvantages of a Bus Topology

• Entire network shuts down if there is a break in the main cable.
• Terminators are required at both ends of the backbone cable.
• Difficult to identify the problem if the entire network shuts down.
• Not meant to be used as a stand-alone solution in a large building.

Mesh Topology

A mesh topology combines characteristics of bus, ring and star topologies. It consists of groups of star-configured workstations connected to a linear bus backbone cable and ring networks Mesh topologies allow for the expansion of an existing network, and enable companies to configure a network to meet their needs

Internet is the most famous example of a mesh topology
Advantages of a Mesh Topology

• Point-to-point wiring for individual segments.  (redundant)
• Supported by several hardware and software venders.

Disadvantages of a Mesh Topology

• Overall length of each segment is limited by the type of cabling used.
• If the backbone line breaks, the entire segment goes down.
• More difficult to configure and wire than other topologies.

Hybrid Topology – A combination of 2 or more different topologies use for networking

Point to Point – Use for connecting one area to another using a high speed connection

Point to Multipoint – Main connection providing services to many devices

Multiprotocol Label Switch is a high performance telecommunications networks that directs data from one network to the next based on short path labels rather that complicated routing tables.  The labels identify virtual links between distant nodes rather than endpoints.

Ad-hoc Mode
Ad-hoc mode is sometimes called peer-to-peer mode Independent Basic Service Set (IBSS).

Infrastructure Mode
Wireless networks running in infrastructure mode use one or more WAP's to connect the wireless network nodes to a wired network segment. A single WAP servicing a given area is called a Basic Service Set (BSS). This service area can be extended by adding more WAP’s. This is called, appropriately, an extended basic Service Set (EBSS).

Considerations When Choosing a Topology:

Costs. A bus network may be the least expensive way to install a network; you do not have to purchase concentrators.

Length of cable needed. The bus network uses shorter lengths of cable.

Future growth. With a star topology, expanding a network is easily done by adding another concentrator.