What is the fee structure of FDDI

Routers forward the packets intelligently

Route optimization is important when transporting data

Routers are intelligent hubs in structured data networks. In OSI layer 3, routers also connect networks of different topologies (bus, star, ring). With the ability to route (forward) different network types and different protocols, optimal traffic control and network utilization is possible. Routing is only required if communication between the end devices is to take place in different subnets.

A router must be able to recognize all the protocols used, as they convert information blocks (parts of the data packets) on a protocol-specific basis. This means that the protocols used must be routable or implemented accordingly or packed into other protocols (tunneling). Since not all protocols can be routed (e.g. NetBIOS), most routers are also able to bridge packets, which is why the term bridge / router is more precise for such devices.

Compared to bridges, routers ensure better isolation of the data traffic because they do not forward network broadcasts as standard, for example. However, routers usually slow down data transfer. In branched network connections, especially in WANs, however, they lead data more effectively to its destination. Routers, on the other hand, are usually more expensive than bridges. Therefore, if necessary, it must be analyzed which device type makes more sense. (Note: A bridge divides the network traffic strictly on the basis of address tables and works on OSI layer 2)

Different router families:
  • There are local routers, which are mainly used for security reasons, e.g. if communication is only to be allowed between certain nodes in the LAN
  • The serial bridge / router for the LAN-to-LAN coupling is probably the largest installed base
  • Due to the large number of ISDN connections available (in Switzerland and Germany) and the attractive fee structure of ISDN, ISDN routers were often used. These types of routers establish a connection in a matter of seconds, and the connection is terminated when not in use
  • With the further spread of ADSL and VDSL as access technology, the use of ISDN became superfluous. ADSL provides telephony and data communication in parallel, using so-called ADSL routers (or VDSL routers or xDSL routers)

Features of a router

Outwardly, routers, hubs or bridges are almost indistinguishable. The essential skills are within. The picture shows a router from Zyxel in a compact design for the home office or the SME network area (Small Office Home Office - SOHO). When selecting a router, the following features must be taken into account:

LAN interfaces
Most routers have one or more LAN interfaces (interfaces), depending on the topology for Ethernet, Token-Ring, 100BASE-T Fast Ethernet, FDDI or ATM. For the connection of the corresponding media, alternatively usable ports (e.g. Ethernet AUI, BNC, RJ45) are available or the connection is implemented as a plug-in unit and can therefore be adapted to the requirements.

WAN interfaces
WAN lines are offered by different providers with different speeds. The costs and the interfaces vary accordingly.

There are of course applications where a lower transmission rate is sufficient. If higher transmission rates are required, the E1 connection common in Europe (in principle an ISDN primary connection) with a transmission rate of 2048 kbit / s is recommended. The WAN interfaces of the router are illustrated in the following principle scheme:

Two different interfaces are visible in this picture: An interface for the local network (LAN) and an interface for the WAN connection; the Internet connection is often connected to the WAN connection via ADSL with this device type.

Network protocols
A router can route multiple network protocols. The most common network protocol family supported by routers is TCP / IP. Due to the spread of heterogeneous networks, certain routers also offer multi-protocol capability. In addition to TCP / IP, depending on the router and equipment, IPX / SPX, DECnet, AppleTalk, OSI, XNS, VINES and Apollo Domain are also supported. All non-routable protocols such as LAT and NetBIOS are bridged, provided the router also supports the bridge function.

Connection protocols
Since the packets are transported differently over the WAN connection than in the LAN, connection protocols are required that take over the secure transport on the WAN connection. At least one, but mostly several of the following connection protocols are implemented in routers: PPP, HDLC, Frame Relay, ISDN, SMDS, X.25.

PPP is of particular importance, as routers from different manufacturers can use this standardized protocol (provided the PPP versions are compatible) to establish connections with one another.

Device management
In large networks, management is often carried out via SNMP consoles. Various network devices can be monitored and configured simultaneously on an SNMP console. For the home area or the SME network, the management functions implemented by the manufacturers are mostly used. Telnet or browser interfaces have established themselves as the user interface for device management.

For the configuration of a router, a higher management effort must be expected than for the configuration of the plug & play bridges. This fact causes not only problems but also costs. Imagine a company with 100 branch offices where the router software needs to be updated. Every router would have to be visited as there is no employee on site who can update and configure the router. It should therefore be possible to configure, update and thus manage the routers completely from a central point (network management console).

The router software is generally saved in Flash PROMs, which offer the advantage of simple upgrades. When the router is booted, the software is then loaded into the RAM and executed. As far as the scope of the software is concerned, the manufacturers pursue different strategies: Either a basic version is supplied with the router, which can then be expanded later as required, or the entire software is supplied with it. The operating software of a router is now typically updated via Internet download.