Thorough Information on Routers
A router (Router,
also known as a path) is a computer network device that transmits packets
through a network to the destination (selecting the transmission path of the
data), a process called routing. A router is a device that connects more than
two individual networks, and routing works on the third layer of the OSI
model-the network layer, such as the Internet Protocol, IP layer.
Basic
introduction
Router (Router),
is connected to the Internet in each LAN, WAN equipment, it will automatically
select and set the route according to the situation of the channel, to the best
path, in order to send the signal before and after. Routers are the hub of the
internet, "traffic police". At present, routers have been widely
used in all walks of life, a variety of different grades of products has become
the backbone of a variety of internal connections, backbone network
interconnection and backbone network and Internet interconnection business. The
main difference between routing and switching is that the switch occurs at the
second layer of the OSI Reference Model (the Data Link layer), and the routing
occurs on the third layer, the network layer. This difference determines that
the routing and switch need to use different control information in the process
of moving information, so the two ways to achieve their respective functions
are different.
Main Features
The router has the
function of judging the network address and choosing the IP path, it can
establish the flexible connection in the multi-network environment, the
different data grouping and the media access method may connect each kind of
subnet, the router only accepts the source station or other router's
information, belongs to the network layer one kind of interconnection
equipment.
It does not care
about the hardware devices used by each subnet, but requires running software
that is consistent with the Network layer protocol.
Routers are local
routers and remote routers, the local routers are used to connect network
transport media, such as optical fiber, coaxial cable, twisted pair; a remote
router is used to connect remote transmission media and requires appropriate
devices such as telephone lines to be equipped with modems, wireless via
wireless receivers, transmitters. Routers are the main node devices of the
Internet. Routers determine the forwarding of data through routing. The
forwarding strategy is called routing (routing), which is also the origin of
the router name (router, forwarding). As the hub of interconnection between
different networks, the router system constitutes the main thread of Internet
based on TCP/IP, and it can be said that routers constitute the skeleton of the
Internet. Its processing speed is one of the main bottlenecks of network
communication, and its reliability and stability directly affect the quality of
network interconnection.
Therefore, in the
park intranet, regional intranet, and even the whole Internet research field,
the router technology is always at the core position, its development course
and direction, become a miniature of the whole internet research.
In the current
China's network infrastructure and information construction in the ascendant,
to explore the role of routers in the interconnection network, status and
development direction, for the domestic network technology research, network
construction, and clear network market for routers and network interconnection
of various plausible concepts, are of great significance. In recent years, the
Exchange router products, in essence, it is not a new technology, but to
improve communication capabilities, the principle of the switch to the router,
so that the data transmission capacity faster and better.
Action function
1. Connect to
different networks
From the point of
view of filtering network traffic, the function of router is very similar to
that of switch and Network Bridge. However, unlike the switches that work on
the network physical layer and physically divide the network segment, routers
use specialized software protocols to logically divide the entire network. For
example, a router that
supports IP protocols can divide the network into multiple subnet segments,
and only network traffic that points to a particular IP address can pass
through the router. For each received packet, the router recalculates its
checksum and writes the new physical address. Therefore, the speed with which
data is forwarded and filtered by routers is often slower than the switch that
only looks at the physical address of the packet. However, for those networks
with complex structures, using routers can improve the overall efficiency of
the network. Another obvious advantage of routers is that they can
automatically filter webcasts. Overall, the entire installation process of
adding routers to a network is much more complex than a Plug and play switch.
2.
Select
a route for information transfer
Some routers only
support a single protocol, but most routers can support the transmission of
multiple protocols, that is, multi-protocol routers. Since each protocol has
its own rules, it is bound to degrade the performance of routers in order to
complete multiple protocols in a router. The main task of the router is to find
an optimal transmission path for each data frame passing through the router and
to effectively transfer the data to the destination site. This shows that the
choice of the best path strategy is the routing algorithm is the key to the
router. In order to do this, the relevant data-the path table (Routing table)
of various transmission paths are stored in the router for routing purposes.
The path table holds the logo information of the subnet, the number of routers
on the network, and the name of the next router.
The path table can
be fixed by the system administrator, or can be dynamically modified by the
system, can be automatically adjusted by the router, can also be controlled by
the host.
Static routing
table: by the system administrator set up a fixed path table is called a static
path table, is generally installed in the system according to the configuration
of the network pre-set, it will not change with the future network structure
changes. Dynamic routing Table: Dynamic path table is the path table that the
router adjusts automatically according to the network system's operation.
Routers provide the functions of the routing protocol (Routing Protocol) to
automatically learn and memorize network operations and automatically calculate
the best path for data transfer when needed.
Router level
1.
Access
router
The access router
connects Small business customers within the home or ISP. The access router has
started not only to provide slip or PPP connections, but also to support
virtual private network protocols such as PPTP and IPsec. These protocols
should be able to run on each port. Technologies such as ADSL will quickly
increase the bandwidth available to households, which will further increase the
burden on access routers.
As a result of
these trends, access routers will support many heterogeneous and high-speed
ports in the future, and will be able to run multiple protocols on each port
while avoiding telephone switching networks.
2.
Enterprise-Class
Routers
Enterprise or
campus-level routers connect many terminal systems with the primary goal of
achieving as many endpoint interconnects as possible, and further requiring
support for different quality of service. Many existing enterprise networks are
Ethernet segments that are connected by a hub or network bridge. Although these
devices are inexpensive, easy to install, and require no configuration, they do
not support service levels. In contrast, a network with routers involved can
divide a machine into multiple collision domains, and thus be able to control
the size of a network. In addition, routers support a certain level of service,
allowing at least several priority levels to be divided. However, the cost per
port of a router is more expensive, and a lot of configuration work is needed
before it can be used. Therefore, the success of the enterprise router is
whether to provide a large number of ports and the cost per port is very low,
whether it is easy to configure, whether to support QoS. Enterprise-class
routers are also required to effectively support broadcast and multicast. The
corporate network also handles a variety of legacy LAN technologies and
supports a variety of protocols, including IP, IPX, and Vine. They also support
firewalls, packet filtering, and a large number of management and security
policies, as well as VLANs.
3.
Backbone-level
routers
Backbone routers
realize the interconnection of enterprise-level networks. The demand for it is
speed and reliability, while the price is subordinated. Hardware reliability
can be obtained by using the technology used in telephone switching networks,
such as hot backup, dual power supply, and dual data access. These technologies
are almost standard for all backbone routers. The main performance bottleneck
of a backbone IP router is the time it takes to find a route in a forwarding
publication. When a packet is received, the input port looks for the
destination of the packet in the forwarding address to determine its
destination port, which increases the cost of routing lookups when the packet
is shorter or when the package is destined for many destination ports.
Therefore, putting some of the frequently accessed destination ports into the
cache can improve the efficiency of routing lookups. Both the input buffer and
the output buffer router have the bottleneck problem of routing lookup.
In addition to
performance bottlenecks, the stability of routers is a frequently overlooked
issue.
4.
Too-bit
routers
Of the three main
technologies used in the future of the core Internet, fiber optics and DWDM are
already mature and readily available. The development of high-performance
backbone switching/routers (too bit routers) has become an urgent requirement
without routers that correspond to the original bandwidth provided by existing
optical fiber technology and DWDM technology, and the new network
infrastructure will not be able to fundamentally improve performance. Too-bit
router technology is now mainly in the development of experimental phase.
5.
Multi-Wan
router
Dual-Wan routers have
a physical 2 WAN ports as external network access, so that the intranet
computer can go through the dual WAN Router load balancing function at the same
time using 2 external network access lines, greatly improve the network
bandwidth.
The current dual-WAN
router has the advantage of "bandwidth convergence" and "one
Network and two lines", which is not to be done by traditional single WAN
routers.
Functional level
1. Broadband router
Broadband router is a new network product in
recent years, it comes into being with the popularization of broadband.
Broadband routers in a compact box integrated router, firewall, bandwidth
control and management functions, with fast forwarding capabilities, flexible
network management and rich network status and so on. Most broadband routers
are optimized for China's broadband applications, which can meet different
network traffic environment, and have good adaptability and network
compatibility. Most broadband routers use highly integrated design, integrated
10/100mbps Broadband Ethernet WAN interface, and built-in multiple-port
10/100mbps adaptive switch, convenient for multiple machines to connect the
internal network and the Internet, can be widely used in families, schools,
offices, Internet cafes, community access, government, enterprises and other
occasions.
2. Modular Router
The modular router
mainly refers to the router's interface type and the partial extension function
is can according to the user actual demand to configure the router, these
routers in the factory generally only provides the most basic route function,
the user may choose the corresponding module according to the network type
which the connection wants to connect, Different modules can provide different
connection and management functions. For example, most modular routers allow
users to choose the network interface type, some modular routers can provide
functional modules such as VPN, and some modular
routers also provide firewall functions, and so on. Most routers today are
modular routers.
3. Non-modular router
Non-modular
routers are low-end routers, usually at home for this type of non-modular
routers. This class of routers is primarily used to connect small business
customers within a home or ISP. It not only provides slip or PPP connections,
it also supports virtual private network protocols such as PPTP and IPsec.
These protocols should be able to run on each port. Technologies such as ADSL
will soon improve the broadband available to households, which will further
increase the burden on access routers.
As a result of
these trends, this class of routers will support many heterogeneous and
high-speed ports in the future, and will be able to run multiple protocols on
each port while avoiding telephone switching networks.
4. Virtual router
Virtual router to
be virtual truth. Recently, a number of new breakthroughs in IP backbone
network equipment have paved the way for the realization of new Internet
services in the future. Virtual routers are a new technology that makes it
possible for some new internet services. With these new services, users will be
able to control the performance of the network, Internet address and routing,
and network security.
The Israeli R&D
Network company is a manufacturer of LAN to WAN solutions, which first proposed
the concept of virtual routing.
5. Core router
The core router,
also known as "backbone router," is a router located in the center of
the network. The router at the edge of the network is called an access router.
Core routers and edge routers are relative concepts. They all belong to the
router, but they have different sizes and capacities. A layer of core routers
is another layer of edge routers.
6. Wireless router
Wireless router is
a wireless coverage of the router, which is mainly used for user access to the
Internet and wireless coverage.
Popular wireless
routers in the market generally support dedicated line xdsl/cable, dynamic XDSL,
PPTP Four kinds of access mode, it also has some other functions of network
management, such as DHCP service, NAT firewall, MAC address filtering and so
on.
7. Single ARM
router
The concept of a
one-armed router is to appear in the three-tier switch, the network between the
VLAN communication can be implemented with ISL, in that case, the router
becomes a "single arm router", the data between the VLAN to enter the
first router processing, and then output, In order to make most of the message
in the same VLAN in the network will not need to pass through the router directly
between the switching device for high-speed transmission. The disadvantage of
this routing method is that it is still a centralized routing strategy, so the
backbone network generally set up a number of redundant "single arm"
routers to share data processing tasks, which can reduce bottlenecks caused by
routers, but also can increase redundant links, However, if there is a large
amount of data transfer between VLANs in the network, bottlenecks will be
formed at the router.
Single-arm routers
are now largely replaced by layer 3rd switches.
8. Wireless
network router
A wireless network
router is a communication device used to connect to a wired and wireless
network, and it can send and receive wireless signals via Wi-Fi technology to
communicate with personal digital assistants and laptops.
A wireless network
router can easily set up a computer network without a cable. However, it is
generally possible that the speed of the data transmission outside the wireless
network is affected by the weather. Other wireless networks include infrared,
Bluetooth and satellite microwaves.
9. Intelligent Flow Control Router
Intelligent flow
Control Router can adjust the bandwidth of each node automatically, so that the
speed of each node can reach the fastest, do not limit the rate of each node,
this is its biggest feature. Intelligent Stream control routers are often used
on the main roads of telecommunications, such as Huawei, Cisco.
Internet cafes,
hotels and other common network star routers.
10. Dynamic Speed
Limit Router
The dynamic
speed-limiting router is a kind of bandwidth that can calculate the needs of
each user in real time. Accurate analysis of user access type, and reasonable
allocation of bandwidth, to achieve on demand, reasonable use, but also has a
priority channel of intelligent provisioning function, this function is mainly
used in Internet cafes, hotels, communities, schools and so on, the most
commonly used internet cafes are audio center routers.
11. Soft Router
The use of desktop
or server with the software to form a routing solution, mainly relying on
software settings, to achieve the function of the router, the common grass soft
routes, sea spiders and so on.
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