1
00:00:00,006 --> 00:00:02,001
- [Instructor] A communications protocol

2
00:00:02,001 --> 00:00:04,005
is a telecommunication system of rules

3
00:00:04,005 --> 00:00:08,008
to allow two or more entities to transfer information.

4
00:00:08,008 --> 00:00:11,006
These rules govern semantics, syntax,

5
00:00:11,006 --> 00:00:13,006
and synchronization of data.

6
00:00:13,006 --> 00:00:17,007
Protocols can utilize many types of software or hardware.

7
00:00:17,007 --> 00:00:19,006
These communications must take place

8
00:00:19,006 --> 00:00:22,000
over a common transmission system.

9
00:00:22,000 --> 00:00:25,001
We generally refer to this as the network.

10
00:00:25,001 --> 00:00:28,000
The framework that is most often used on a network

11
00:00:28,000 --> 00:00:31,007
is the TCP/IP and OSI models.

12
00:00:31,007 --> 00:00:34,003
They are both used as a roadmap for vendors

13
00:00:34,003 --> 00:00:36,007
to share a common set of actions.

14
00:00:36,007 --> 00:00:39,003
Modern systems use a layering technique.

15
00:00:39,003 --> 00:00:41,009
Different protocols are used at various levels

16
00:00:41,009 --> 00:00:44,004
to handle specific tasks.

17
00:00:44,004 --> 00:00:48,000
This cooperation is often referred to as a protocol family,

18
00:00:48,000 --> 00:00:51,007
or protocol suite, most notably IPX/SPX,

19
00:00:51,007 --> 00:00:55,003
AppleTalk, and of course, TCP/IP.

20
00:00:55,003 --> 00:00:57,008
Each layer tackles a specific problem,

21
00:00:57,008 --> 00:00:59,007
then passes it onto the next,

22
00:00:59,007 --> 00:01:04,004
issues like application, transport, and network.

23
00:01:04,004 --> 00:01:05,008
At these varying layers,

24
00:01:05,008 --> 00:01:09,003
there are a few fundamental services that need be addressed.

25
00:01:09,003 --> 00:01:11,002
Data formats are crucial.

26
00:01:11,002 --> 00:01:13,007
They break digital messages into bit strings

27
00:01:13,007 --> 00:01:15,005
that are divided into fields

28
00:01:15,005 --> 00:01:17,006
that carry relevant information.

29
00:01:17,006 --> 00:01:20,007
Address formats for data exchange define the standards

30
00:01:20,007 --> 00:01:24,002
by which a sending and receiving host is identified.

31
00:01:24,002 --> 00:01:28,001
This could be the likes of an IP address or MAC address.

32
00:01:28,001 --> 00:01:31,000
Sometimes, address mapping must be performed.

33
00:01:31,000 --> 00:01:33,000
This is where one layers address scheme

34
00:01:33,000 --> 00:01:34,007
is translated to another.

35
00:01:34,007 --> 00:01:38,002
An example would be IP addressing to MAC addressing.

36
00:01:38,002 --> 00:01:40,007
At layer three, the network layer,

37
00:01:40,007 --> 00:01:42,009
routing is crucial to passing traffic

38
00:01:42,009 --> 00:01:44,008
from one network to another.

39
00:01:44,008 --> 00:01:47,005
If traffic cannot be transmitted reliably,

40
00:01:47,005 --> 00:01:51,004
error detection can be implemented to manage the chaos.

41
00:01:51,004 --> 00:01:52,007
Reception acknowledgements

42
00:01:52,007 --> 00:01:55,004
can also improve transmission reliability

43
00:01:55,004 --> 00:01:58,006
and are crucial to some reliable transmission types.

44
00:01:58,006 --> 00:02:00,008
Another important component is how the system

45
00:02:00,008 --> 00:02:03,005
should react to the loss of information.

46
00:02:03,005 --> 00:02:08,000
Protocols are the basis for all network communications.