7.4.1 Follow Data Through an Internetwork

advertisement
OSI Data Link Layer
Network Fundamentals – Chapter 7
思科网络技术学院理事会.
http://www.catc.edu.cn
1
Objectives

Explain the role of Data Link layer protocols in data transmission.

Describe how the Data Link layer prepares data for transmission
on network media.

Describe the different types of media access control methods.

Identify several common logical network topologies and describe
how the logical topology determines the media access control
method for that network.

Explain the purpose of encapsulating packets into frames to
facilitate media access.

Describe the Layer 2 frame structure and identify generic fields.

Explain the role of key frame header and trailer fields including
addressing, QoS, type of protocol and Frame Check Sequence.
思科网络技术学院理事会.
http://www.catc.edu.cn
2
Context Index
 7.1 Data Link Layer – Accessing the Media
 7.2 Media Access Control Techniques
 7.3 Media Access Control Addressing and Framing Data
 7.4 Putting it All Together
 7.5 Labs and Activities
思科网络技术学院理事会.
http://www.catc.edu.cn
3
7.1 Data Link Layer –
Accessing the Media
思科网络技术学院理事会.
http://www.catc.edu.cn
4
7.1.1 Data Link Layer – Supporting &
Connecting to Upper Layer Services
 The Data Link layer performs two basic services:
-Allows the upper layers to access the media using techniques
such as framing
-Controls how data is placed onto the media and is received from
the media using techniques such as media access control and
error detection
思科网络技术学院理事会.
http://www.catc.edu.cn
5
7.1.1 Data Link Layer – Supporting &
Connecting to Upper Layer Services
 Data Link Layer Terms
思科网络技术学院理事会.
http://www.catc.edu.cn
6
7.1.1 Data Link Layer – Supporting &
Connecting to Upper Layer Services
 Numerous Data Link layer protocols are being used
over various types of LANs and WANs.
思科网络技术学院理事会.
http://www.catc.edu.cn
7
7.1.2 Data Link Layer – Controlling Transfer
across Local Media
 Layer 2 protocols specify the encapsulation of a packet
into a frame .
思科网络技术学院理事会.
http://www.catc.edu.cn
8
7.1.3 Data Link Layer – Creating a Frame
 Data Link layer frame includes:
思科网络技术学院理事会.
http://www.catc.edu.cn
9
7.1.3 Data Link Layer – Creating a Frame
 The role the Data Link layer plays in linking the
software and hardware layers
思科网络技术学院理事会.
http://www.catc.edu.cn
10
7.1.4 Data Link Layer – Connecting Upper
Layer Services to the Media
 Data Link layer is often divided into two sub-layers:
-Logical Link Control
-Media Access Control
思科网络技术学院理事会.
http://www.catc.edu.cn
11
7.1.5 Data Link Layer – Standards
 Standards for the Data Link layer
思科网络技术学院理事会.
http://www.catc.edu.cn
12
7.2 Media Access Control Techniques
思科网络技术学院理事会.
http://www.catc.edu.cn
13
7.2.1 Placing Data on the Media
 Explain the necessity for controlling access to the
media
思科网络技术学院理事会.
http://www.catc.edu.cn
14
7.2.2 Media Access Control for Shared Media
 There are two basic media access control methods for
shared media:
-Controlled - Each node has its own time to use the medium
-Contention-based - All nodes compete for the use of the medium
思科网络技术学院理事会.
http://www.catc.edu.cn
15
7.2.2 Media Access Control for Shared Media
 There are two basic media access control methods for
shared media:
-Controlled - Each node has its own time to use the medium
-Contention-based - All nodes compete for the use of the medium
思科网络技术学院理事会.
http://www.catc.edu.cn
16
7.2.2 Media Access Control for Shared Media
 There are two basic media access control methods for
shared media:
-Controlled - Each node has its own time to use the medium
-Contention-based - All nodes compete for the use of the medium
思科网络技术学院理事会.
http://www.catc.edu.cn
17
7.2.3 Media Access Control for Non-Shared
Media
 Define Full Duplex and Half Duplex as it relates to
Media Access Control for non-shared media
思科网络技术学院理事会.
http://www.catc.edu.cn
18
7.2.3 Media Access Control for Non-Shared
Media
 Define Full Duplex and Half Duplex as it relates to
Media Access Control for non-shared media
思科网络技术学院理事会.
http://www.catc.edu.cn
19
7.2.3 Media Access Control for Non-Shared
Media
 Define Full Duplex and Half Duplex as it relates to
Media Access Control for non-shared media
思科网络技术学院理事会.
http://www.catc.edu.cn
20
7.2.4 Logical Topology vs Physical Topology
 The representation of how the media is used to
interconnect the devices is the physical topology.
 A logical topology is the way a network transfers frames
from one node to the next.
 Topologies used in networks
are:
-Point-to-Point
-Multi-Access
-Ring
思科网络技术学院理事会.
http://www.catc.edu.cn
21
7.2.5 Point-to-Point Topology
 A point-to-point topology connects two nodes directly
together.
思科网络技术学院理事会.
http://www.catc.edu.cn
22
7.2.5 Point-to-Point Topology
 A virtual circuit is a logical connection created within a
network between two network devices.
思科网络技术学院理事会.
http://www.catc.edu.cn
23
7.2.5 Point-to-Point Topology
 A virtual circuit is a logical connection created within a
network between two network devices.
思科网络技术学院理事会.
http://www.catc.edu.cn
24
7.2.6 Multi-Access Topology
 Data from only one node can be placed on the medium
at any one time.
 Every node sees all the frames that are on the medium,
but only the node to which the frame is addressed
processes the contents of the frame.
 A Data Link media access control method is required to
regulate the transmission of data.
 The media access control methods are typically
CSMA/CD or CSMA/CA.
思科网络技术学院理事会.
http://www.catc.edu.cn
25
7.2.6 Multi-Access Topology
 How nodes access the media in a multi-access
topology
思科网络技术学院理事会.
http://www.catc.edu.cn
26
7.2.7 Ring Topology
 In a logical ring topology, each node in turn receives a
frame. If the frame is not addressed to the node, the
node passes the frame to the next node.
 If there is no data being transmitted, a signal (known
as a token) may be placed on the media and a node
can only place a data frame on the media when it has
the token.
思科网络技术学院理事会.
http://www.catc.edu.cn
27
7.2.7 Ring Topology
 How nodes access the media in a logical ring topology
思科网络技术学院理事会.
http://www.catc.edu.cn
28
7.3 Media Access Control Addressing
and Framing Data
思科网络技术学院理事会.
http://www.catc.edu.cn
29
7.3.1 Data Link Layer Protocols – The Frame
 The structure of the frame and the fields contained in
the header and trailer vary according to the protocol.
思科网络技术学院理事会.
http://www.catc.edu.cn
30
7.3.2 Framing – Role of the Header
 The role of the frame header in the Data Link layer
思科网络技术学院理事会.
http://www.catc.edu.cn
31
7.3.3 Addressing – Where the Frame Goes
 Data Link layer addressing is contained within the
frame header and specifies the frame destination node
on the local network.
 If the device is moved to another network or subnet,
physical addresses will still function with the same
Layer 2 physical address.
 The intermediate device - a router - will decapsulate the
original frame, create a new frame for the packet.
思科网络技术学院理事会.
http://www.catc.edu.cn
32
7.3.3 Addressing – Where the Frame Goes
 Addressing Requirements
思科网络技术学院理事会.
http://www.catc.edu.cn
33
7.3.4 Framing – Role of the Trailer
 The role of the frame trailer in the Data Link layer
思科网络技术学院理事会.
http://www.catc.edu.cn
34
7.3.5 Data Link Layer Protocol – The Frame
 Given the wide range of physical media used in
networking, there are a correspondingly high number of
Layer 2 protocols in use.
802.11 Wireless
Frame
802.11 Wireless
Frame
HDLC
Frame Relay
PPP frame
Ethernet Frame
思科网络技术学院理事会.
http://www.catc.edu.cn
35
7.3.5 Data Link Layer Protocol – The Frame
 Ethernet Protocol for LANs
思科网络技术学院理事会.
http://www.catc.edu.cn
36
7.3.5 Data Link Layer Protocol – The Frame
 Point-to-point Protocol for WANs
思科网络技术学院理事会.
http://www.catc.edu.cn
37
7.3.5 Data Link Layer Protocol – The Frame
 Wireless Protocol for LANs
From
Retry
Power
More
Fragments
Data
DS
field
Management
field
field
-Contains
Set
- -to
Set
Set
1(RA)
to
ifin
field
to
the
1field
--1indata
Set
-cyclic
indicate
Set
for
To
DS
field
-field
Set
to
1Depending
frames
Transmitter
(TA)
field
-aType
and
fields
–Indicates
Duration/ID
Order
Fragment
Sequence
Number
Number
-field
field
adata
-frame
-todata
Indicates
type
on
the
Protocol
Wired
Equivalent
Version
field
Version
(WEP)
of
FCS
field
-Subtype
afield
32-bit
Destination
Source
Address
Address
(SA)
(DA)
field
-to
MAC
Frame
Body
field
-Privacy
Contains
the
Receiver
Address
field
-1isto
802.11
frame
in
Identifies
one
of
functions
and
sub
type
frame
the
number
ofaddress
frame,
for
number
represents
each
Strictly
fragment
assigned
Ordered
either
of
the
to
service
adata
the
frame
redundancy
check
(CRC)
of system
frame
destined
for
the
distribution
address
of
the
of
node
the
the
final
initiated
destination
the
information
being
transported;
for
MAC
that
identifies
the
wireless
frames
retransmission
1
to
to
asequence
indicate
node
exiting
that
inuses
have
power-save
that
ofuse
aanother
an
distribution
node
earlier
will
mode
fragment
frame
besystem
that
in
more
field
-that
Set
to
1the
ifthree
the
frame
contains
time,
class
frame;
in
(does
retransmitted
microseconds,
not
need
frames
reordering)
required
are
to and
node
frame
the
network
functions
ofbuffered
the
frame:
control,
data,
frames,
typically
an
IP
packet
device
that
is
the
immediate
recipient
of
(devices
in
the
wireless
structure)
WEP
information
for
security
power-save
frames
are
mode
for
that
node
deviceencrypted
that
transmitted
the
frame
transmit
identified
by frame
duplicate
or an
sequence
association
the
framethe
management
identity (AID) for the station that
numbers
transmitted the frame
思科网络技术学院理事会.
http://www.catc.edu.cn
38
7.4 Putting it All Together
思科网络技术学院理事会.
http://www.catc.edu.cn
39
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
40
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
41
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
42
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
43
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
44
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
45
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
46
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
47
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
48
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
49
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
50
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
51
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
52
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
53
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
54
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
55
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
56
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
57
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
58
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
59
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
60
7.4.1 Follow Data Through an Internetwork
 A simple data transfer between two hosts across an
internetwork.
思科网络技术学院理事会.
http://www.catc.edu.cn
61
Summary
思科网络技术学院理事会.
http://www.catc.edu.cn
62
思科网络技术学院理事会.
http://www.catc.edu.cn
63
Download