are key to your organization's WAN strategy. Here are some
tips on buying these layer 3 boxes. by Mahesh Rathod
are designed to link many network technologies, and are used
in campus and enterprise networks
"routing table" ensures that packets travel the most efficient
paths to their destinations
router is a device that operates at the Network Layer, or
layer 3 of the OSI model. Routers are designed to link diverse
network technologies, and are frequently used in large campus
and enterprise networks. At the network layer of operation,
you find a wider range of mechanisms that are designed to
deal with the issues that can arise when building large network
systems. By operating at the network layer, routers can easily
deal with computers attached to everything from slow serial
links to high-speed LAN systems.
In sufficiently large and complex networks, and especially
networks with multiple network technologies, you may wish
to use a router for the benefits it can bring. Many vendors
provide routers with multi-protocol capabilities, making it
possible to deal with various protocols in a single device.
Purpose of routers
Routers are primarily used to connect two or more IP networks,
or an IP network to Net. A router consists of a computer with
at least two NICs (network interface cards) that support the
IP protocol. The router receives a packet from one NIC and
forwards the received packets to an appropriate output NIC.
Routers forward packets based on the packet's IP destination
address, along with routing information held within the router
in a routing table. A network road map that routers use, ensure
that packets reach their destinations using the most efficient
paths. If a link between two routers fails, the sending router
can determine an alternate route to keep traffic moving.
Routers can be classified on their functionality or the applications
they can be used for.
Based on their function, routers can be classified as static
Static routers choose the shortest way to the destination
and are cheaper. Dynamic routers choose
the best way to the destination after taking network traffic
Based on applications, routers can be of three types: access,
backbone and IP aware switches. Access routers can be seen
as Internet gateways, where packets are classified and traffic
is policed to ensure that flows do not violate their assigned
bandwidths. Backbone routers take care of large amounts of
aggregated IP traffic, at very high speeds. IP aware switches
use IP addresses to switch the packets on to and between different
local area networks.
Routers or Switches?
Routers are typically used to connect workgroups to the backbone.
Here fiber optic cables are used for backbones, with ATM,
token ring or Ethernet as the networking technology. Routers
also form the central point for connecting a company's
different sites together over a WAN, using
technologies such as Frame Relay, leased lines, X.25 and ATM.
In WAN environments, routers play a more crucial role than
switches do. Routers not only effectively manage range of
WAN technologies, but also make optimal use of WAN resources
through intelligent path selection.
Within the network core, Ethernet switches are generally used
to segment workgroup network. They provide dedicated bandwidth
to servers, high-performance users, and smaller groups of
Here's a list of some of the key features you need to consider
when buying a router.
Multiple network protocol support:
Enterprises need the flexibility of working with multi-protocol
networks, since they communicate with diverse hardware and
software from many vendors. Routers need to support various
standard networking protocols such as:
AppleTalk (Phase 1 and Phase 2)
Xerox's Universal Protocol (PUP)
Frame Relay serial encapsulation
Point-to-Point Protocol (PPP)
Support for standard media:
need to support the following industry-standard networking
Synchronous serial V.35, RS-232, and RS-449
Ethernet IEEE 802.3 and Type II
FDDI Single and dual mode
Token Ring IEEE 802.5
High-Speed Serial Interface (HSSI) T3 rates
Multiple routing protocol support:
should be able to support various routing protocols such as:
Network Address Translation
Open Shortest Path First
Hot Standby Router Protocol (HSRP)
Border Gateway Protocol (BGP)
Enhanced Interior Gateway Routing Protocol
Carrier class reliability:
should be able to assure the highest possible reliability
and network availability, as these are the needs of ISP and
enterprise networks. Automatic switchover capability allows
the router to operate without data or connection loss in the
event of primary component failures.
today's application intensive IP networks, the ability to
control quality of service (QoS) becomes increasingly important.
Routers should have hardware-based QoS controls and features
that enable a network administrator to easily control and
manage network traffic and applications with no degradation
in system performance.
administrators should be able to manage the router by using
CLI (command line interface), Web browser or GUI (graphical
user interface). The network management system must be able
to provide centralized status, statistics monitoring, and
Mahesh Rathod can be reached at email@example.com