0AA001 Data Communication Basis ISSUE2.0.ppt

ISSUE
ISSUE
Fixed Network Curriculum
Development Section
OAA000001 Data
Communication Basis
2.0
2.0

Confidential Information of
Huawei. Security Level: Internal
2
Objective
Hierarchical structure of data
communication and the role of each layer
Constitution and roles of the link layer
protocols
Constitution and roles of network layer
protocols
Constitution and roles of transport layer
protocols
Types and roles of routing protocols
After this session, you will learn:

3
References
Product Manual--Technical Manual--Signaling and
Protocols--Appendix

4
About this Session
Section 1 TCP/IP Architecture and Implementation
Section 2 Link Layer Protocols
Section 3 Network Layer Protocols
Section 4 Transport layer protocols
Section 5 IP Routing

5
OSI Reference Model
Application Application programs
Data format and representation
Interhost communication
End-to-End connections
Addresses and best path
Access to media
Binary transmission
Representation
Session
Transport
Network
Data link
Physical

6
TCP/IP Architecture
FR ETHERNET PPP SLIP …
2
IP
3
TCP UDP
4
7 HTTP FTP SMTP TELNET NFS SNMP
ICMP
ARP/RARP
… …

7
TCP/IP Implementation

8
TCP/IP Transmission Mode
Applicatio
n Layer
Transpor
t layer
Network
layer
Link
layer
Physical
layer
Network
layer
Link
layer
Physical
layer
Link
layer
Physical
layer
Network
layer
Link
layer
Physical
layer
Applicatio
n Layer
Transpor
t layer
Network
layer
Link
layer
Physical
layer
Terminal system Router Terminal system
Router Bridge

9
About this Session

10
Link Layer Protocols
PPP
LAN and WAN

11
PPP Protocol
 PPP – Point-to-point protocol
 PPP supports full duplex and synchronous/asynchronous
transfer modes, and it consists of three types of protocols: LCP
(link control protocol), various kinds of NCPs (network layer
control protocol) and various kinds of PPP extended protocols.
 LCP is mainly used to establish, disconnect and monitor PPP data
link;
 NCP is mainly used for negotiation of the format and type of
packets transmitted over this data link;
 PPP extended protocols are mainly used to provide further support
to PPP functions.
 PPP provides authentication protocols for network security,
such as PAP (Password Authentication Protocol ) and CHAP

12
MP
Network Layer
MP
PPP PPP
PPP

13
Link Layer Protocols
PPP
LAN and WAN

14
LAN and WAN
Different coverage ranges
 LAN: Applicable to limited geographical areas
 WAN: Applicable to remote connection
Different rates
 LAN: 10Mbps, 100Mbps and 1000Mbps
 WAN: 64Kbps, 128Kbps, 384Kbps and 2Mbps
Different technologies are used

15
LAN Types
Ethernet
Switching Ethernet (mainstream of LAN currently)
Token ring network
FDDI (Fiber distributed digital interface)

16
What is Ethernet?
Ethernet is a LAN implementation technology defined by IEEE Std
802.3 as part of the LAN/MAN standards
802.X protocol suite specifies the access mode of network, and the
technologies of the switching Ethernet and fast Ethernet are all named
802.X protocol

17
Ethernet Physical Structure
Bus type (10BASE2 and 10BASE5 at early stage)
A B
Star type (other Ethernet types after 10BASE-T)
C
H I J
D E F
K L M
Relay
Hub/
Bridge
A B C D E F
Hub/
Bridge

18
Ethernet Work Principle – CSMA/CD

CSMA/CD: Carrier Sense Multi Access with Collision Detection

Carrier sense: Detection before transmission

Collision detection: Detection during transmission

Backoff: Handling after a collision is detected

19
Commonly Used Devices in LAN
HUB
LAN SWITCH
ROUTER

Twisted pair

Optical fiber

Network card

20
HUB
It works in the physical layer and copies binary bits one by one
among cables
It is a kind of shared network device connecting together network
cables that are connected to different computers. and the
communication can be connected only between two ports at a
certain time

Gradually washed out in network applications

21
LAN SWITCH
It works in the link layer and stores and forwards frames
between LANs
It connects many hubs through network cables to constitute a
larger network
It connects computer terminals to constitute a LAN

22
Twisted Pair
 10BASE-T
 10:the transmission rate is 10Mbps; BASE: using base band signal; T: twisted
pair; Transmission distance: a maximum of 100m for Category 3/4/5 unshielded
twisted pair cable and Category 5 shielded twisted pair cable
 100BASE-TX
 100:the transmission rate is 100Mbps; Transmission distance: a maximum of
100m for Category 5 unshielded twisted pair cable and Category 5 shielded
twisted pair cable
 10BASE2

2: thin coaxial cable. The maximum transmission distance is 185m
 10BASE5

5: thick coaxial cable. The maximum transmission distance is 500m

23
Optical fiber
100BASE-FX
 The maximum transmission distance of the single-mode optical fiber is
15km and the maximum transmission distance of the multi-mode optical
fiber is 2km for the 100Mbps Ethernet
1000BASE-SX
 Short wavelength optical fiber, 1000Mbps Ethernet, the maximum
transmission distance of the multi-mode optical fiber is 220m
1000BASE-LX
 Long wavelength optical fiber, 1000Mbps Ethernet, the maximum
transmission distance of a multi-mode optical fiber is 550m, the maximum
transmission distance of a single-mode optical fiber is 10km

24
Shared Ethernet
HUB
 When any port receives a packet,
this packet will be broadcast to all
the ports directly, logically
constituting a shared medium
 If two or more ports receive
packets simultaneously, collision
will occur, and DTE will implement
the CSMA/CD algorithm
 Only one DTE can implement
valid transmission at a certain
moment
A B D
Col l i si on
C
Col l i si on Col l i si on Col l i si on

25
Switched Ethernet

Bridge (LAN SWITCH)
 It implements address learning
according to SA (Source Address) of
the received packet to establish the
corresponding relation between
address and port
 After receiving a packet, it checks the
table according to DA (Destination
Address) of the packet and forwards
the packet to the specific port
 Multiple DTEs can implement valid
transmission at a certain moment, and
no mutual interference will occur
A B C D

26
Shared Ethernet vs. Switched Ethernet
Shared Ethernet Switched Ethernet
Topology Structure
Work mode
Bandwidth
Equipment
Equipment processing layer
Main equipment technology
Complexity degree of equipment
Bus type or star type
Half Duplex
Bandwidth of a
shared medium
Hub, relay
Physical layer
CSMA/CD
Simple
Star
Full Duplex
Bandwidth of an
exclusive medium
Bridge
MAC layer
Address learning and
switching
Complicated

27
WAN Types

Packet-switched network X25
(DDN)Digital data network
Frame Relay

28
Packet-switched Network

X.25 protocol is the interface procedure between DTE and DCE
X.25 protocol covers three layers: physical layer, data link layer and
network layer

29
Digital Data Network （ DDN ）

DDN is the point-to-point connected physical layer network

The common rate of DDN is 64Kbps, while the highest speed is 2Mbps

The leased cable service adopts the fixed charging mode

30
Frame Relay

FR is the second layer network, and it is the simplified X.25
Integrated with the advantages of packet switching and DDN, it can
have the same rate as DDN

Lines are not exclusively occupied, thus, the utilization rate is high

31
About this Session

32
Network Protocols
IP
ARP
RARP
ICMP
Protocol application

33
IP
 IP——Internet Protocol.
 As a network layer protocol of the TCP/IP protocol suite, IP is
used to transmit datagrams of the transport layer and the
application layer.
 IP identifies the source and destination through IP address.

34
IP Address
An IP address is a unique 32-bit address assigned to each
host connected to Internet.
0 net-id host-id
1 0 net-id host-id
1 1 0 net-id host-id
1 1 1 0 Multicast address
1 1 1 1 0 Reserved for future use
0 1 2 3 4 8 16 24 31
Class A
Class B
Class C
Class D
Class E

35
IP Address
Usually, every eight bits of the 32-bit IP address is
expressed in decimal digits. A dot is added between every
two sets of these digits. For example, an IP address is as
follows:
10000000 00001011 00000011 00011111
This is a class B address. It can be specified as 128.11.3.31

36
IP Address
Network
type
Available IP
Network
Range
Note:
A 1.0.0.0 ~
126.0.0.0
Network numbers with all 0s or 1s are reserved
for special usage. The all-0 host address is used
to configure network routes while the all-1 host
address is used for broadcast address of this
network. Network number 127 is used for self-
loop interface.
B 128.1.0.0 ~
191.254.0.0
address is used for broadcast address of this
network.
C 192.0.1.0 ~
223.255.254.
Range of IP Address:

37
IP Address
Network
type
Available IP
Network
Range
Note:
D Null Class D addresses are multicast addresses, with
the range of 224.0.0.0 ~ 239.255.255.255. They are
not provided to common users. The all-1 host
address represents the broadcast address, i.e.
broadcast is made to all hosts on the network.
E Null 255.255.255.255 is the whole-network broadcast
address. 240.0.0.0 ~ 255.255.255.254 are reserved
for future use.
Range of IP Address:(cont.)

38
Subnet and Mask
As described above, we can conclude that there the
number of the host addresses that can be distributed in a
network is more than 16,000,000 for class A addresses.
While in the actual networks, this mode is not reasonable
as no network is so big to hold so many hosts. This case
also exists in class B addresses and class C addresses. A
network, therefore, must be fractionalized to improve
effectiveness of IP addresses and ease the management
of them.
Subnets are the actual embodiment of this idea. They are
the small networks in a big network.
The concepts of Subnet and Subnet Mask can help us
plan IP addresses of a network.

39
Subnet and Mask
The introduction of subnet increases the number of networks, which
is realized by reducing the number of hosts. A mask is a 32-bit
numeral consisting of consecutive 1s and consecutive 0s. It
implements bit by bit “and” operation with the IP address, acting as
a screen. Bits of 1 in the mask will not be screened off and will
remain unchanged; For bits of 0, the difference of the host address
will be screened off, thus the same network address will be obtained
in a network.
For example, a class A address can be changed to a class C address
by the following means. Such class C addresses constitute a
subnet::
IP address: 120. 118. 100. 86
Subnet mask: 255. 255. 255. 0

40
Network Protocols
IP
ARP
RARP
ICMP

41
ARP Protocol
ARP——Address Resolution Protocol, ARP implements
the conversion from IP addresses to MAC addresses
(Medium Access Control).
MAC address – A 48-bit binary address, usually appears
as a 12-digit hexadecimal number, like 00e0fc012345.
Each network device has a globally unique MAC address.
Applicable to LANs.
The communications among hosts within a LAN must be
implemented through the MAC address.

42
ARP Protocol
MAC header
FF. FF .FF. FF. FF. FF
08. 02. 80. 65. 63. 09
IP header
189.110.58.69
189.110. 67. 56
ARP request
message: What is
your MAC address?
The process for the host 189.110.67.56 to search the host
189.110.58.69 to obtain the MAC address is as follows:
MAC header
08. 02. 80. 65. 63. 09
05 23. 88. 57. 03. 44
IP header
189.110. 67. 56
189 ． 110 ． 58 ．
69
ARP reply message:
This is my MAC
address
The host 189.110.67.56 sends a broadcast message
The host 189.110.58.69 responses to the message

43
Network Protocols
IP
ARP
RARP
ICMP

44
RARP
RARP - Reverse Address Resolution Protocol
Compared with ARP, RARP works just in the opposite
way: RARP obtains an IP address through the MAC
address. In communications, many hosts do not have an
IP address during initialization, and, in this case, the
RARP protocol must be used to obtain the IP address.
For example: No-disk workstation; when the computer is
configured to obtain IP address automatically.

45
Network Protocols
IP
ARP
RARP
ICMP

46
ICMP
ICPM - Internet Control Message Protocol
It allows hosts or routers to report errors and exceptions.

47
ICMP Protocol
Relation between ICMP message and IP packet
IP packet header IP packet data
ICMP message
I P packet

48
ICMP
ICMP application:
Error messages--messages mainly used to carry changed
routes information
Inquiry messages :
 ICMP Echo request message
 ICMP Echo reply message

49
Network Protocols
IP
ARP
RARP
ICMP

50
Network Layer Protocol Application
The PING command uses ICMP to know whether the
communication with the peer host is normal.
Under DOS mode, ARP –A is used to obtain the
corresponding relation between an IP address and a MAC
address.

51
About this Session

52
Transport Layer Protocols
Functions of transport layer protocols:
 The link layer is responsible for encapsulation and
transmission of data, and the network layer implements IP
packet routing, etc. However, for data communications
mainly based on computers, some problems, like flow
control and reliability, must be solved before the
communications can be realized. These functions are
implemented in the transport layer.

53
TCP
UDP

54
TCP
TCP——Transfer Control Protocol.
TCP has the following three functions:
 Flow control: It implements flow control via slide window;
 Reliability: It realizes reliability through sequence number
and acknowledgement mechanism;
 It indicates the upper layer application by port number so
as to hand the data to the corresponding application
program to process.

55
TCP Protocol
TCP
message
TCP
header
Source port number Destination port number
sequence number
acknowledgment number
TCP U A P R S F
headerReserved R C S S Y I Window size
length N
TCP checksum
Emergency data position
pointer
Options(if any)
Data of variable lengths
Bit 0 3 10 15 31

56
TCP
Source/Destination port numbers :
 Port numbers are used to identify upper layer protocols.
Different applications have different port numbers, so that the
request and received data can be processed by corresponding
applications.
 Port numbers are divided into source port number and
destination port number, which are not necessarily the same in
communications.
 By means of combining port numbers with IP addresses,
different applications at different places can be uniquely
identified within the whole network; in a host, it is determined
through the port numbers of TCP (or UDP) to which application

57
TCP
TCP and UDP port numbers are divided into the following three
classes:
The port numbers with the values smaller than 255 are
used for common applications, for example, FTP, Telnet,
SMTP and HTTP use ports 21, 23, 25 and 80 respectively.
255~1023 are allocated to companies.
1024 and its larger values are not defined yet.

58
TCP
UDP

59
UDP
UDP——User Datagram Protocol .
UDP does not require data buffering during transmission
and does not involve connection management. Under the
UDP mode, Valid arrival of messages can be ensured by
timeout retry mechanism of application program.

60
UDP Protocol
Source port number Destination port number
UDP Message length Checksum
Data of variable lengths
Bit 0 15 31

61
UDP
Comparison between TCP and UDP:
TCP is a connection-oriented reliable transport protocol
UDP is connectionless unreliable transport protocol
TCP is complicated while UDP is simple
UDP is applicable to the communication transmission with
high real-time requirement (for example, voice
communication), while the real-time feature of TCP is not
as good as that of UDP due to large overhead

62
Application of TCP and UDP
TCP and UDP are designed for application programs of
different characteristics. Among common programs,
SMTP, FTP and Telnet adopt TCP, while DNS, SNMP and
multicast adopt UDP.

63
About this Session

64
IP routing
那一个通道 ?
Which channel?
A
B
The important role of the network layer is searching path, that is, forwarding
a data packet to the destination host according to the destination IP
address

The equipment to implement this work is router

Characteristics and Roles of a Router
A router must meet the following requirements:
 It must have two or more network layer interfaces, used for
connection of different networks;
 The protocol must be realized to the network layer.
A router has the following two function:
 Generating routing tables
 Forwarding data packets to other networks

66
Examples of Router Connection
Router
A
Router
B
Interface address
61.1.1.1
Interface address
129.6.0.1
Interface address
129.6.69.107
Interface address
202.6.6.1
Subnet
61.1.1.1/8
Subnet
129.6.0.0/16
Subnet
202.6.6.0/24

Routing Table in Router A
Destination
network address
Destination
network mask
Next Hop Egress interface
202.6.6.0 255.255.255.0 129.6.0.1 129.6.69.107
129.6.0.0 255.255.0.0 129.6.69.107 129.6.69.107
61.0.0.0 255.0.0.0 61.1.1.1 61.1.1.1

Routing Table in Router B
202.6.6.0 255.255.255.0 202.6.6.1 202.6.6.1
129.6.0.0 255.255.0.0 129.6.0.1 129.6.0.1
61.0.0.0 255.0.0.0 129.6.69.107 129.6.0.1
Destination
network address
Destination
network mask
Next Hop Egress interface

Generating Modes of Routing Tables
 Supporting static routing
 The routing information is inputted by operation personnel
entry by entry
 Dynamic routing
 Routing table items are generated by routing protocols
 The common routing protocols include OSPF protocol and
Routing Information Protocol (RIP).

70
Working Flow of a Router
LAN2
IP
ETH PPP
Ethernet
interface
Serial
interface
IP
ETH
PPP
LAN1 WAN
Router Router
Route
selection
protocol
conversion
Protocol
encapsulation
Sending Transmission Receiving
Protocol
decapsulation
Serial
interface
Ethernet
interface

71
Summary
Corresponding to the standard 7-layer model of OSI, the
TCP/IP suite includes four layers: Link layer, network
layer, transport layer and application layer.
The role of the link layer is to ensure reliable and correct
transmission of message information.
The network layer and the transport layer are the key
points of this lesson. The classification method of IP
addresses and the segmentation method of subnets, the
roles of TCP and UDP and the application method of ports
must be mastered.
A router is used to determine the path for packet
transmission. Routing protocols are complicated, and
trainees are just required to understand their functions.

72

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