Frame relay wide area networks became a popular typology
in the 1990s.
It was the departure from the circuit-switched T1s
to more of a packet-based communication.
This is where we took LAN traffic
and we encapsulated within frame relay frames,
and sent it into the frame relay cloud.
Inside of that cloud, the provider
had their own method of getting the data to the other side.
And you, as the end user, never saw
what that process happened to be.
We would simply put data into the frame relay
cloud with the destination location,
and the provider would take care of getting it
to that remote site.
On the low end, it was common to see frame relay installed
on 64 kilobits per second, and you could have that speed range
all the way up to DS3, which would be
around 45 megabits per second.
This has been effectively replaced
with MPLS and other types of networking,
but you may still see a number of frame relay implementations
used on legacy networks.
ATM stands for Asynchronous Transfer Mode,
and it's a way of communicating over a SONET network.
ATM didn't use frames or packets, it used 53 byte cells.
Every bit of data put onto an ATM network
was 53 bytes in length.
It was really 48 bytes for the data
and five bytes for a header.
This provided high throughput, it
provided real-time communication,
and it had very low latency because you
knew exactly when the next 53 byte cell would
come through the network.
The speeds of ATM had a maximum of OC-192,
or about 10 gigabits per second, which at the time
were extremely fast communication speeds.
These speeds were often limited by the segmentation
and reassembly that had to occur, or the SAR.
That's because our ethernet frames are much larger
than the 53 byte cells.
We had to split our ethernet frames up into smaller pieces,
put them inside of the ATM network,
and then reassemble all of those frames on the other side.
ATM gained market share in the 1990s,
but the technology faded away as IP-based technologies became
more popular.
A much more modern wide area network technology
is MPLS, or Multiprotocol Label Switching.
We looked at frame relay and ATM and took
the best of both of those typologies to build MPLS.
In a method similar to frame relay,
MPLS data is put onto the WAN with a label that designates
what the destination is.
This makes it easy for the provider
to route that traffic through the core of the network.
And we can send many types of traffic over MPLS--
they can be IP packets, we can send those older ATM cells,
and we can even send ethernet frames.
MPLS has become a very common way of providing wide area
network connectivity, and it's easy to find
services and hardware that can support an MPLS network.
One of the terms you'll hear referenced with MPLS
is pushing and popping as we send data into the MPLS cloud.
There is a label that is pushed onto packets, so
that the internal provider network will
know what the destination will be for that data.
And when that data arrives on the other side,
that label is popped off, and the data
is provided to the customer.
Another popular WAN technology is PPP,
or the point-to-point protocol.
This is a way to connect two devices so that you can then
send other types of protocols over that WAN link.
PPP is commonly used for dial-up connections, serial links,
you'll see it for mobile phones, and it's
used for DSL connections for your home or business.
Some of the advantages of PPP is that it
can be used for authentication of the network,
data can be compressed through PPP,
there's the ability to detect errors,
and you can build multiple PPP connections
and multi link those together for larger bandwidths.
PPPoE is an extension of PPP that
encapsulates the PPP protocol within an Ethernet frame.
This is very common on DSL networks,
and telephone providers certainly know how to use PPP,
so the PPP over Ethernet is a logical extension to that.
It's very easy to implement a PPP over Ethernet connection,
since most operating systems already understand PPPoE.
There's no complex routing decisions to make,
and the architecture of PPPoE is very similar to the operation
of a dial-up network.
PPPoE also gives you some choices
in your internet provider.
You can use PPP over Ethernet to connect to the network,
and then decide which Internet Service Provider you'd
like to use at that point.
A popular Cisco WAN technology is the DMVPN,
or Dynamic Multipoint VPN.
It's something you commonly find on Cisco routers
because you can connect your network
and have it decide when and where it would like
to connect to other locations.
You're effectively having all of your sites
build their own VPNs as needed.
The tunnels are built dynamically and on-demand,
depending on what location needs to speak with another location.
For example, it would be very common to have
a main office and multiple remote sites,
and you might want to connect your main office
to each individual remote site.
But what if one remote site wanted to talk to another?
In this scenario, they would have
to communicate to the main office and then
back down to the remote site.
But with the DMVPN, those sites can dynamically
build a connection between each other,
send the communication they'd like to send,
and then tear down the connection.
This means that any of the remote sites
can send data to any of the other remote sites
in the most efficient way possible.
SIP is the Session Initiation Protocol.
It's one of the more popular control protocols
that are used for Voice over IP communication.
With a traditional business PBX, or Private Branch Exchange,
you would bring in T1 lines or ISDN connections
to bring in voice channels.
You would also have a separate wire
going to every desk that would be
used for the telephone that's on everyone's desktop.
When you fill up all of those 23 voice channels,
people calling in would get a busy signal.
With SIP trunking, you're using a Voice
over IP connection to an IP or PBX
provider that allows you to communicate
using Voice over IP.
This is a much more efficient use of bandwidth--
then you can control just how much compression you're
using on these Voice over IP calls,
so you're able to support much more capacity
than a traditional ISDN or T1 connection.
It's less expensive than ISDN lines,
and you have many more options available on your digital Voice
over IP communication.