Time
31 hours 29 minutes
Difficulty
Beginner
CEU/CPE
30

Video Description

Network Topologies: Ring This lesson focuses on the ring topology. In ring topology, all of the nodes are connected to form a loop between them and data is transferred using a token. A token is a data indicating endpoint. Mesh topology is advantageous because it has fewer collisions and allows for equal access. Disadvantages is that is passes data on to every computer, if one workstation gets it; they all get it.

Video Transcription

00:04
now, our next apology is going to be our ring Topology now are ranked. Apology is going to be a topology where all of our different nodes are connected to form a loop between them in our rink topology data is transferred using a token.
00:17
Now, a token is essentially a bit of data that's tacked onto our packets, or they were passing around between our points.
00:24
That is indicating what in point that this data is indicate is sent for. So if we're passing around our token,
00:33
our tokens going to say, Okay, here's the Here's the address of the data of my destination for this data that I have in this packet.
00:42
Now, as we're passing the token, plus the little bit of data around if computer eh,
00:49
what A,
00:50
B, C and D
00:53
Computer A. Is trying to send data to computer, see, and we have a clockwise
00:59
going ring. Then Computer A is gonna pass it along
01:03
computer B and the tokens going, and then computer B is gonna read the token and say, Oh, this isn't for me. It's gonna pass. It's a computer, See? And then computer, see is going to said say, Oh, this. This isn't for me, either. It's for a computer D, and then computer sees gonna pass it along, and then computer d will read the token and say, Oh, this is for me
01:23
when Computer D gets the token and it gets the data is going to do, Ah, one of two things with the token. If Computer D needs to pass data back to Computer A, it can rewrite Maur information to the token now saying that it's going to pass the data along to computer, eh?
01:42
Or it can clear the token. So if it isn't going to if it's not me, it doesn't need to send any more data
01:49
to computer A than Computer D will clear the token. Now a computer can on Lee send their own data if they have a clear token, and you can only do one of three things with the token.
02:01
If the token is intended for you or if the token is intended for you as the recipient, you can clear or you can reset the token,
02:12
reset it with someone out with another destination.
02:15
If the token is not for you, then you can pass the token. Ah, and keep the data in the same so you can clear, passed or passed or set on a token. But you can on Lee, you can only clear or set if the token is destined for you or you can. And you can only set. If the token is either destined for you or clear.
02:35
Let's explain this a little bit better, since
02:37
we probably can probably confuse the couple people there. Um,
02:43
so again, we have our token now on at Computer D. But now we have a clear token. So it's a blank token with no data.
02:53
Computer D is now is now just gonna send that blank token to computer, eh?
02:59
Computer A says. Oh, I don't mean I don't have any data. I need to pass on to anybody, either.
03:04
Computer A says I don't have any data. I need to pass on
03:07
token. Gets to computer, be in computer, be says Yes, I have data. I need to send this data to computer to computer D. Computer D is very popular.
03:17
Um, and so computer be says yes, I need to pass the state along to computer D.
03:23
So it sets the now clear token
03:28
with
03:30
the with computer see as the destination, plus whatever data it needs to send.
03:36
So now it passes this token to computer See
03:40
are sorry. The destination token is set to Computer D.
03:45
Our destination for this particular token from Computer B is computer date.
03:49
So it passes this token for Computer D to computer See
03:53
and computer See means to send data to computer, eh?
03:59
But it can't right now because even though it has the token, that token is not clear. That token has a destination.
04:06
So computer See says, Oh, I mean to send data. It looks at the token, it says, but it's not clear.
04:13
And so it's gonna pass that along to Computer D because it says on its not clear, and it's not destined for me. So it'll pass that along to Computer D and the Computer D will now read the token
04:27
computer. D now has the token that's destined for it. It's going to read the data, and then now that it read the data, it's going to clear the token
04:35
and that tokens gonna pass the computer. A. Who doesn't need to send anything computer, be who doesn't need to send anything and finally back to computer. See who now who still needs to send data now has a clear token and now consumed their their data along.
04:50
So our token is sort of like our token is sort of like a basket that were passing around the circle
04:57
and if the basket. And if we put something in the basket for somebody else on the other side of the circle, then we put what we need in the basket. And we also mark who the baskets, who, who the recipient is of this stuff in our basket,
05:10
and we passed the back of a basket around the circle, even if someone else needs to use the basket. When we put stuff in the basket, the basket is full. They can't just add more stuff into the basket to pass around. We can only have information in our basket. We could only have information attached to our token for one destination. We can't
05:28
past our token through computer see
05:30
in computer, See says, Oh, this token is destined for computer D, but I also have information on the past. The computer D. I'll just tack my information onto this information No, it can't do that. The information for Computer d was from computer Be so computer be passes it to computer, see who passes to Computer D.
05:49
And then when that tokens clear,
05:51
then that note, then computer see can send the data. So a node can on Lee send data when it has in its when it has in its possession the clear token. And if it doesn't have any data to send, it'll just pass that token around.
06:09
So what's the good side? What? Some of the benefits of this type of scenario? Well, in our ring topology, we're gonna have less collisions.
06:16
Ah, collision is essentially when we have to knows that air trying to send data at the same time. So say this was this was our partial meshed apology. Well, if computer A was trying to talk Thio Computer be at the same time his computer be, maybe was trying to talk back to computer A, then we would have some collisions going on there
06:35
because our computers we may have data
06:39
that is our both trying to use that same line resource at the same time and causing collisions.
06:46
We've talked in earlier modules about collision domains domains where, where anything inside of our of our switch may cause a collision.
06:55
But that's not connected by either switch or a router. May cause a collision if they're connected directly to each other or if they're connected with the hub that could cause collisions.
07:04
Um, we also another good aspect of this is that all of our devices have equal access. All of our devices get equal turns with the token,
07:14
so it passes to everybody.
07:15
Computer d can't can't hoard the token and then
07:20
just send it directly to computer. Be who sends it directly back. The token has to go through everybody, and as soon as soon as it's clear,
07:29
someone else can use it.
07:30
So
07:32
our token gets our ring. Our devices in our ring topology get equal access to our network
07:40
Now, for our downsides Now are downsides are that data does have to pass through potentially all of our computers. So for sending information from computer a two computer D in our clockwise ring, then the date is also going to pass through computer B and computer. See who, if they want to, could read that data,
08:00
so it may pose a security issue.
08:01
The other issue that we may encounter is that if we have one work station down than all our work stations air down because our data passes one direction,
08:13
say, even if, um,
08:16
we get to the point where even if Computer B is trying to pass data into computer, see, it may be able to pass at one time. But as soon as computer see now has a clear token, it's gonna pass that around back to computer a computer. A. Can't send that clear token anywhere
08:33
because it can't send it back against the flow of the stream. It can't send it forward onto computer. Be so Computer B is out of commission computer. Be well, actually say that our links are up. Our actual physical connections are up, but our node went down are maybe the computer shut off
08:50
or the cable got disconnected from our computer or the computer network interface card went bad,
08:54
so that note is out of commission, so that token can't go anywhere. We can't communicate over our network.
09:01
So
09:03
Wooderson, uh, what's, um what's a mitigation strategy that we could use on our ring on our rink? apology to make it a little bit more redundant.
09:11
Well,
09:11
on are ranked apology. We can have concentric rings.
09:16
So say we have one ring. That tramp passes data clockwise,
09:20
and then we have another ring that actually passes data counterclockwise.
09:28
So we still have less collisions.
09:33
We're still giving equal access.
09:37
But now our network's gonna run a little bit quicker
09:41
because we actually have
09:43
two concentric rings. One ring is passing data along one way, and one ring is gonna pass the data along the other way. And then depending on which node that art our node, our computers trying to send data to it may pass it clockwise or counterclockwise and are different. Nodes will get twice as much,
10:03
uh,
10:03
twice as much token time, because there's two rings that cuts the time. They have to wait for tokens by half because they may get a token from the other direction
10:11
with our two concentric rings. This also allows us to mitigate having our entire network down if one if a single link goes down. So if the link from computer aid to computer B goes down, we can't use our outside ring, But we can still use are We can't use our clockwise ring,
10:31
but we can still use our counter clockwise ring.
10:33
So
10:35
that's that's one of our strategies that we may use in order to help our token ring network flow a little bit better.
10:43
So we mentioned a little while ago are logical versus our physical
10:50
token ring network.
10:52
Now, in a logical and a physical token and a physical ring network
10:58
are ranked apology. It would look like this when you actually look at the computers. They are not necessarily the computers, but are different nodes. They would be physically connected in a ring. The cables would go from one to the next to the next to the next back to the first.
11:13
That would be a physical ring topology.
11:18
Now our logical ring topology. And when we're talking about our art, apologies were referring to how the data passes. Logically, we're not We're not nearly is worried about the physical set up. When we're talking about apologies. We're worried about the logical configuration. So if you hear someone asking, you know what kind of topology is your network?
11:39
There are what type of topology did you set this up as
11:41
they're they're asking you how the data is flowing. They're not necessarily asking you about the physical devices. If they are, they'll probably explicitly say physical.
11:50
Um,
11:52
so in a physical are
11:54
in a and R logical set up,
11:58
we may have
12:01
a network that looks like this
12:03
with one central device,
12:07
and then each of our different nodes
12:11
connects to this one central device.
12:13
Now, this looks this looks a lot like another topology. We're gonna talk about
12:18
talk about a little bit later called a start apology.
12:22
But this topology is actually
12:24
a ring topology.
12:26
Because the way this device in here, the way this device right here actually passes data along
12:33
is in a token, it uses a token.
12:35
So
12:37
this central device
12:39
receive may receive data from each of the other devices, and then it's going along, and its internal workings are going to each device and saying, OK, you have the token. You have the token, you have the token, you have the token. And this device itself is managing this network by using a token to decide who can send
12:58
and who gets data went.
13:03
So
13:03
it's almost like inside this device
13:07
we have our token, we are not our token, but we have our we have our ring topology.
13:11
So
13:13
for all intensive purposes,
13:16
if you were just looking at this network physically looking how the cables were set up, you would probably think that this was a star, our star networked apology.
13:24
But once you figured out and once you knew what how this device worked and how this device past data along, then you'd say, Oh, no, this is actually a ring topology, because it's utilizing its usual utilizing a data token, and only one device can talk at a time. So be aware that just because,
13:43
uh, you can't you can't judge a book by its cover. You can't judge a network by its physical layout all the time.
13:48
You actually need to know how the data is flowing in order to determine a DePaul apology

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