TRUYỀN SỐ LIỆU VÀ MẠNG Ch04 communication networks

Data Communication and
Networking
Dr. –Ing. Vo Que Son
Email:

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

1


Content
 Chapter 3: Data Link Layer Protocols
 Flow Control
 Error Control
 Connection Management
 Data link layer Protocols

 Chapter 4: Communication Networks
 Introduction to communication networks
 802.x standard and TCP/IP Model
 Ethernet, Token Pass, Token Ring
 IP Addressing: Classfull and VLSM
 Network devices
 Switching and Routing
 STP, VLAN
Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

2


Local Area Network
 A local area network (LAN) is a computer network that
interconnects computers in a limited area such as a home,
school, computer laboratory, or office building using network
media
 Medium:
 Coaxial cable
 Twisted-pair line

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

3


Wide Area Network
 A wide area network (WAN) is a network that covers a broad
area (i.e., any telecommunications network that links across
metropolitan, regional, or national boundaries) using private
or public network transports

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

4


Physical Topology
Bus

Ring

Star

Telecomm. Dept.
Faculty of EEE

Extended Star

Hierarchical

Mesh

DCN
HCMUT

5

Project 802
 IEEE 802 refers to a family of IEEE standards dealing with local
area networks and metropolitan area networks
 The services and protocols specified in IEEE 802 map to the
lower two layers (Data Link and Physical) of the seven-layer
OSI networking reference model. In fact, IEEE 802 splits the
OSI Data Link Layer into two sub-layers named Logical Link
Control (LLC) and Media Access Control (MAC), so that the
layers can be listed like this:

Data link layer
• LLC Sublayer:
• MAC Sublayer

Physical layer
Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

6


Project 802
 Modules in Project 802
 LLC: based on HDLC protocol
 Multiplexing protocols

transmitted over the MAC
layer (when transmitting) and
decoding them (when
receiving).
 Providing node-to-node flow
and error control
 MAC: provides addressing and
channel access control
mechanisms that make it possible
for several terminals or network
nodes to communicate within a
multiple access network that
incorporates a shared medium
Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

7


LLC Frame formats
LLC PDU:
DSAP: Destination
Service Access Point
SSAP: Source Service
Access Point

Control field:

HDLC format

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

8


Ethernet
 Topology: bus, star, ring
 Media Access Control: Deterministic, Non-deterministic
 Addressing:
Every computer has a unique way of identifying itself :
MAC address or physical address.
The physical address is located on the Network Interface
Card (NIC).
MAC addresses have no structure, and are considered flat
address spaces. MAC addresses are sometimes referred to
as burned-in addresses (BIAs) because they are burned
into read-only memory (ROM) and are copied into
random-access memory (RAM) when the NIC initializes.
• 0000.0c12.3456 or 00-00-0c-12-34-56
• If MAC is all bits 1: broadcast address
Telecomm. Dept.
Faculty of EEE

DCN

HCMUT

9


IEEE 802.3: frame format
 Preamble: 10101010 (7 bytes)
 The Start Frame field (10101011) tells other devices on the network that a
frame is coming down the wire.
 The Address field stores the source and destination MAC addresses.
 Source address is unicast, Destination address can be unicast, multicast or broadcast

 The Type/Length field is an optional field
 Exact length of frame, or Layer 3 protocol making the sending request, or Not used

 The Data field is the actual information being sent by the upper layer
protocols. Therefore, it will be all upper layer data.
 CRC: 4 bytes, error checking

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

10


Ethernet: 802.3










10Base-2:
10Base-5:
10Base-T:
10Base-F:
100Base-TX:
100Base-T4:
100Base-FX:
1000Base-T:

Telecomm. Dept.
Faculty of EEE

50Ω Thin cable, 185m.
50Ω Thick cable, 500m.
100Ω UTP cable, 100m.
Fiber optic cable, 1000m.
100Ω UTP/STP cable, 100m.
100Ω UTP (4p) cable, 100m.
Fiber optic cable, 400m.
100Ω UTP/STP cable, 100m.

DCN

HCMUT

11


Ethernet: 10BASE-5
 NIC: Network Interface Card
 MAU: Medium Attachment Unit
 Thick Ethernet (thicknet)
 50Ω Thick cable, 500m

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

12


Ethernet: 10BASE-2
 Thin Ethernet
 50Ω Thin cable, 185m.

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

13


Ethernet: 10BASE-T
 Twisted-pair cable
 100Ω UTP cable, 100m.
 Data rate: 10 Mbps

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

14


Ethernet Operation
Specified by the technology
being used.
Determine who can transmit
and when.
Two types:
Deterministic: “Let’s take
turns”.
• Token-Ring, FDDI.

Non-deterministic: “First come,
first serve”.
• Ethernet : CSMA/CD.

Carrier Sense Multiple Access with Collision
Detection (CSMA/CD).
Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

15


Three common layer 2 technologies
Ethernet: logical
broadcast topology
Token Ring: logical
token ring topology
FDDI: logical token ring
topology
Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

16


Ethernet MAC
Ethernet is a shared-media broadcast
technology. The access method CSMA/CD

used in Ethernet performs three functions:
Transmitting and receiving data packets
Decoding data packets and checking them for
valid addresses before passing them to the upper
layers of the OSI model
Detecting errors within data packets or on the
network

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

17


CSMA/CD Process

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

18


Fast Ethernet
 Speed: 100 Mbps

 Distance: <250m
 Backward compatible with Ethernet
10 Mbps
 Uses Twisted-pair or Fiber

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

19


Gigabit Ethernet
 >1 Gbps
 Using Fiber optic
 Deployed as backbone
network, connecting Fast
Ethernet networks

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

20

Token Ring
 Token ring LAN technology was a
protocol which resided at the data link
layer (DLL) of the OSI model. It used a
special three-byte frame called a token
that travels around the ring. Tokenpossession grants the possessor
permission to transmit on the medium.
Token ring frames travel completely
around the loop.
 Initially used only in IBM computers, it
was eventually standardized with
protocol IEEE 802.5.
 Physical ring topology
Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

21


Token Ring
 The data transmission process goes as follows:
 Empty information frames are continuously circulated
on the ring.
 When a computer has a message to send, it seizes the
token. The computer will then be able to send the
frame.
 The frame is then examined by each successive

workstation. The workstation that identifies itself to
be the destination for the message copies it from the
frame and changes the token back to 0.
 When the frame gets back to the originator, it sees
that the token has been changed to 0 and that the
message has been copied and received. It removes
the message from the frame.
 The frame continues to circulate as an "empty"
frame, ready to be taken by a workstation when it has
a message to send.

 Issues:
 Who generates token?
 If the node keeping token is dead, what happens?
Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

22


Token Bus
 Also use token as Token Ring
 Physical Bus topology
 Token bus was standardized by IEEE standard 802.4. It is
mainly used for industrial applications
 Due to difficulties handling device failures and adding new
stations to a network, token bus gained a reputation for being

unreliable and difficult to upgrade

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

23


IP Addressing: IPv4
 An IPv4 address is 32 bits
long.
 The IPv4 addresses are
unique and universal.
 Network address + Host
address: Hierarchical
Addressing Schemes.

Telecomm. Dept.
Faculty of EEE

DCN
HCMUT

24


IP Header

IP protocol version
number
header length
(bytes)
“type” of data
max number
remaining hops
(decremented at
each router)
upper layer protocol
to deliver payload to
how much overhead with
TCP?
 20 bytes of TCP
 20 bytes of IP
 = 40 bytes + app layer
overhead
Telecomm. Dept.
Faculty of EEE

32 bits
ver head. type of
len service

length
fragment
16-bit identifier Flags
offset
upper
time to

header
layer
live
checksum

total datagram
length (bytes)
for
fragmentation/
reassembly

32 bit source IP address

32 bit destination IP address
Options (if any)

data
(variable length,
typically a TCP
or UDP segment)

E.g. timestamp,
record route
taken, specify
list of routers
to visit.

DCN
HCMUT

25