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Router

Router

A router is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet. Data sent through the internet, such as a web page or email, is in the form of data packets. A packet is typically forwarded from one router to another router through the networks that constitute an internetwork (e.g. the Internet) until it reaches its destination node.

A router is connected to two or more data lines from different IP networks. When a data packet comes in on one of the lines, the router reads the network address information in the packet header to determine the ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey.

The most familiar type of IP routers are home and small office routers that simply forward IP packets between the home computers and the Internet. An example of a router would be the owner's cable or DSL router, which connects to the Internet through an Internet service provider (ISP). More sophisticated routers, such as enterprise routers, connect large business or ISP networks up to the powerful core routers that forward data at high speed along the optical fiber lines of the Internet backbone.

The main purpose of a router is to connect multiple networks and forward packets destined either for its own networks or other networks. A router is considered a layer-3 device because its primary forwarding decision is based on the information in the layer-3 IP packet, specifically the destination IP address. When a router receives a packet, it searches its routing table to find the best match between the destination IP address of the packet and one of the addresses in the routing table. Once a match is found, the packet is encapsulated in the layer-2 data link frame for the outgoing interface indicated in the table entry. A router typically does not look into the packet payload,[citation needed] but only at the layer-3 addresses to make a forwarding decision, plus optionally other information in the header for hints on, for example, quality of service (QoS). For pure IP forwarding, a router is designed to minimize the state information associated with individual packets. Once a packet is forwarded, the router does not retain any historical information about the packet.

The routing table itself can contain information derived from a variety of sources, such as a default or static routes that are configured manually, or dynamic routing protocols where the router learns routes from other routers. A default route is one that is used to route all traffic whose destination does not otherwise appear in the routing table; this is common – even necessary – in small networks, such as a home or small business where the default route simply sends all non-local traffic to the Internet service provider. The default route can be manually configured (as a static route), or learned by dynamic routing protocols, or be obtained by DHCP.

A router can run more than one routing protocol at a time, particularly if it serves as an autonomous system border router between parts of a network that run different routing protocols; if it does so, then redistribution may be used (usually selectively) to share information between the different protocols running on the same router.

Besides making a decision as to which interface a packet is forwarded to, which is handled primarily via the routing table, a router also has to manage congestion when packets arrive at a rate higher than the router can process. Three policies commonly used in the Internet are tail drop, random early detection (RED), and weighted random early detection (WRED). Tail drop is the simplest and most easily implemented; the router simply drops new incoming packets once the length of the queue exceeds the size of the buffers in the router. RED probabilistically drops datagrams early when the queue exceeds a pre-configured portion of the buffer, until a pre-determined max, when it becomes tail drop. WRED requires a weight on the average queue size to act upon when the traffic is about to exceed the pre-configured size, so that short bursts will not trigger random drops.

Another function a router performs is to decide which packet should be processed first when multiple queues exist. This is managed through QoS, which is critical when Voice over IP is deployed, so as not to introduce excessive latency.

Yet another function a router performs is called policy-based routing where special rules are constructed to override the rules derived from the routing table when a packet forwarding decision is made.

Router functions may be performed through the same internal paths that the packets travel inside the router. Some of the functions may be performed through an application-specific integrated circuit (ASIC) to avoid overhead of scheduling CPU time to process the packets. Others may have to be performed through the CPU as these packets need special attention that cannot be handled by an ASIC.

The most popular products in category Router All category products

Маршрутизаторы Cisco серии 7600
18
12
Extreme Networks BlackDiamond X8
17
13
Маршрутизаторы серии HPE FlexNetwork MSR3000
9
18
EUROTECH Everyware IoT
6
19
Коммутаторы Cisco Nexus серии 9000
11
11
JUNIPER MX Series 5G Universal Routing Platform
20
1
QFabric System
15
6
ENDIAN Industrial IoT Security
10
9
EXTREME NETWORKS CER 2000 Series Router
19
0
Cisco 4000 Series Integrated Services маршрутизаторы
14
4
Juniper QFX коммутаторы
8
10
Коммутаторы Cisco Nexus серии 7000
5
11

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Compare: Enterprise routers

Characteristics

Number of models

Total onboard WAN 10/100/1000 Mbps ports

Total onboard WAN 10 Gbps ports

Aggregate Throughput

Encrypted Throughput

CPU support

Memory

Storage size

Storage expansion

Number of USB ports

Number of SIC slots

VPN

Firewall

Security system

Power over Ethernet

Max Power consumption

WLAN

3G

LTE

SDN/SD-WAN support

Maximum IPv4 routes

Maximum Ipv6 routes

OEM Software

Warranty

7
2
4
7
15
3
Up to 4
20
Up to 2
Up to 10
N/A
N/A
Up to 2
4
N/A
Up to 2
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Up to 10 Gbps
192 Gbps
Up to 5 Mpps (64 byte packets)
Up to 4.5 Gbps
Up to 10 Tbps
Up to 1.2 Tbps
Up to 7 Gbps
N/A
Up to 3.3 Gbps
N/A
N/A
N/A
N/A
N/A
Up to 6-core 1.3 GHz
Up to 12-core 1.2 GHz
Up to 10-core 2.2 GHz Intel processor
N/A
Up to 8 GB
N/A
Up to 4 GB
Up to 4 GB
Up to 64 GB
N/A
Up to 32 GB
N/A
256 MB
Up to 8 GB
Up to 400 GB
N/A
Up to 2 USB 3.0 Type A
N/A
Up to 2 USB 2.0 Type A
Up to 2 USB 2.0 Type A
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N/A
N/A
N/A
Up to 4
Up to 4
N/A
N/A
Up to 1450 W
Up to 315 W
Up to 300 W
Up to 700 W
Up to 23 kW
Up to 8 PSUs per chassis
N/A
1500000
500000
N/A
N/A
N/A
N/A
256000
500000
N/A
N/A
N/A
90 days
N/A
1 year
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F.A.Q. about Router

What Is a Router?

Routers are the nodes that make up a computer network like the internet. The router you use at home is the central node of your home network.

It functions as an information manager between the internet and all devices that go online (i.e. all devices connected to the router). Generally speaking, routers direct incoming traffic to its destination.

This also makes your router the first line of security in protecting your home network from malicious online attacks.

What Does a Router Do?

Your router handles network traffic. For example, to view this article, data packages coding for this website have to transit from our server, through various nodes on the internet, and finally through your router to arrive on your phone or computer. On your device, your browser decodes those data packages to display the article you’re currently reading.

Since a typical household has more than one device that connects to the internet, you need a router to manage the incoming network signals. In other words, your router makes sure that the data packages coding for a website you want to view on your computer aren’t sent to your phone. It does that by using your device’s MAC address.

While your router has a unique (external) IP address to receive data packages from servers worldwide, every device on your home network also carries a unique MAC address. Simply put, when you try to access information online, your router maintains a table to keep track of which device requested information from where. Based on this table, your router distributes incoming data packages to the correct recipient.

What Is the Difference Between Modems and Routers?

A modem turns the proprietary network signal of your ISP (internet service provider) into a standard network signal. In theory, you can choose between multiple ISPs and some of them may use the same delivery route. Your modem knows which signals to read and translate.

The kind of modem your ISP will provide you with depends on how you’re connecting to the internet. For example, a DSL modem requires a different technology than a cable or fiber optic broadband modem. That’s because one uses the copper wiring of your telephone line, while the others use a coaxial or a fiber optic cable, respectively.

The DSL modem has to filter and read both the low frequencies that phone and voice data produce, as well as the high frequencies of internet data. Cable modems, on the other hand, have to differentiate between television and internet signals, which are transmitted on different channels, rather than different frequencies. Finally, fiber optic uses pulses of light to transmit information. The modem has to decode these signals into standard data packages.

Once the modem has turned the ISP’s network signal into data packages, the router can distribute them to the target device.

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