Csdrhrt

I've been reading about networking hardware and network technologies recently, but I still can't quite link everything together.

The route:

Internet -> Modem -> Router -> Wireless Access Point

This is what I think I know:

1. Modem Converts Analog to Digital, then it sends digital signal to router, and assigns an IP connected to the WAN.

2. Router then converts this WAN so that it can be used as a LAN with switches so that multiple device can be connected to it. This is done via TCP/IP.

2.1. An ISP only gives out one IP, therefore PORT is used to "divide" the IP so that it can be used internally.

3. Access Point is used to connect the devices by emitting a wireless signal.

Question:

1. Where does NAT fit into all of this? (Reading definitions of NAT doesn't help).

2. Where does bridging fit into all of this? (Reading definitions doesn't help too).

3. Where does DHCP fit into all of these?

It would be nice if someone could link a website where they explained networking as a WHOLE.

Some corrections on what you know:

1) Modem Converts Analog to Digital then it sends digital signal to router, and assigns an IP connected to the WAN

IP packets don't care what medium it's traveling around in. Mentioning things like "analog to digital" and "digital signal" aren't needed unless you are building your own modem.

2) Router then converts this WAN so that it can be used as a LAN with switches so that multiple device can be connected to it. This is done via (TCP/IP)

A router forwards (i.e. copies) traffic between a WAN and a LAN. A switch lets multiple devices share one Ethernet port - in the case of most consumer routers, it's letting multiple devices share the "LAN" port.

Routers work using IP (Layer 3), switches work using Ethernet (layer 2)

2.1) An ISP only gives out one IP, therefore PORT is used to "divide" the IP so that it can be used internally.

NAT is used to "divide" the IP - and you can "divide" by telling NAT to forward traffic coming in on a specific port to a specific machine behind the NAT.

1) Where does NAT fit into all of this ? (Reading definitions of NAT
doesn't help).

NAT allows multiple machines "behind" a router to share one public WAN-facing IP. NAT has to track each connection coming in and going out to keep track of who "has" what connection.

If you want machines behind the NAT to be accessible from the outside, you tell the NAT router that traffic on a specific port should be forwarded to a specific machine on the inside.

2) Where does bridging fit into all of this ? (Reading definitions
doesn't help too).

A bridge connects two or more nodes on the same network. Data is not modified when it passes through a bridge.

Your cable modem is a type of bridge, as is your switch and the 4 port switches often built into consumer level routers.

If you want to connect two or more nodes on different networks (you can think of "the Internet" as a separate network), you use a router, not a bridge. Routers forward traffic for networks behind them, and this means they "rewrite" the traffic since they are resending it for machines behind it.

3) Where does DHCP fit into all of these ?

DHCP is a way for a node to ask for an IP. A DHCP server keeps track of who has what IPs and makes sure no one gets duplicates.

Most consumer routers also have built-in DHCP servers. Machines behind them ask it for what is usually private, LAN IPs. Your router asks the ISP's DHCP server for a public, WAN IP in the same way.

Answers:

1. 
   

   NAT allows multiple machines to share a single IP. Your "statement" 2 and 2.1
   would seem (at least partially) incorrect - this is what NAT does. It may help if
   you look at it the reverse ways - multiple computers connecting to the Internet but
   appearing behind a single IP address. NAT [ Network Address Translation ] takes the
   internal IP's (normally 192.168.x.x or 10.x.x.x) and rewrites the source IP address.
   It also records source IP, target IP, source port and target port and maps the response
   back based on this.

   
   
   

   I wonder if by "PORT" you mean "Port Mapping" ? Port mapping is the process of
   allowing an incoming connection from the wider internet through to specific machines
   depending on the external port. Thus port 25 might be mapped to 1 machine to handle
   incoming email while port 80 might be mapped to a webserver. (Similarly you might
   map port 81 externally to port 80 if you have 2 web servers, then you can refer
   to EXT.IP.ADDR:81 to see the second one).

   
   



2. Bridging only has to do with the LAN side of things. Think of a simple switch -
   this is basically a multiport bridge. Bridging is putting to network interfaces
   together so they appear to be one. Its used quite a bit in Access points so that
   WIFI devices and devices on the LAN appear to be talking directly to each other.




3. DHCP is the mechanism computers use to get an IP address, gateway, DNS server
   and possibly other information needed to establish an IP (version 4) address.
   [ You don't need a DHCP server if everything uses static IP addresses, similarly
   practically speaking, a DHCP server must be on a connection which is directly
   connected to each machine it serves ]

Networking for Beginners - Dictionary of Network Terminology

NAT

Network Address Translation (NAT) is a network protocol used in IPv4 networks that allows multiple devices to connect to a public network using the same public IPv4 address. NAT modifies the IP address information in IPv4 headers while in transit across a traffic routing device. (http://en.wikipedia.org/wiki/Network_address_translation)

You have many computers on the network, since your ISP provides only one IP for your network NAT helps all the computers to manage their connections using the same IP.

BRIDGING

Network bridging describes the action taken by network equipment to allow two or more communication networks, or two or more network segments, to create an aggregate network. Bridging is distinct from routing which allows the networks to communicate independently as separate networks. A network bridge is a network device that connects multiple network segments. (http://en.wikipedia.org/wiki/Bridging_(networking) ).

Bridging is what connects two different networks. eg: Your ISP's network and your network or even two of your own networks.

DHCP

The purpose of DHCP is to automate the IP address configuration of a computer without a network administrator. IP addresses are typically selected from a range of assigned IP addresses stored in a database on the server and issued to a computer which requests a new IP address. An IP address is assigned to a computer for a set interval, after which, the computer must renew the IP address or acquire a new one. (http://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol)

DHCP helps all the computers on your network to obtain IP addresses automatically without you assigning one to them manually.