Chương 2

Mạng Ethernet là một mạng cục bộ (LAN) sử dụng công nghệ Ethernet để kết nối các thiết bị điện tử với nhau. Ethernet là một họ các tiêu chuẩn định nghĩa cách truyền dữ liệu qua cáp xoắn đôi hoặc cáp quang. Các thiết bị được kết nối với mạng Ethernet thường bao gồm máy tính, máy tính xách tay, máy in, máy chủ và thiết bị định tuyến.

 Cơ bản về mạng

What Is a Network?

A network is a connected collection of devices that can

communicate with each other Networks carry data in many kinds of environments, including homes, small businesses, and large enterprises

Common Physical

Components of a Network

Interpreting a Network Diagram

Resource-Sharing Functions and Benefits

 Data and applications

Network User Applications

 Web browser (IE, Firefox, and so on)

 Instant messaging (Yahoo IM, Microsoft Messenger, and so on)

 Collaboration (Whiteboard, Netmeeting, WebEx, and so on)

 Databases (file servers)

Impact of User Applications on the Network

 Batch applications

 FTP, TFTP, inventory updates

 No direct human interaction

 Bandwidth important, but not critical

Physical Topology Categories

Logical Topologies

Bus Topology

All devices receive the signal.

Star Topology

Transmission through a central point.

Single point of failure.

Extended-Star Topology

More resilient than star topology.

Ring Topology

Signals travel around ring.

Single point of failure.

Dual-Ring Topology

Signals travel in opposite directions.

More resilient than single ring.

Full-Mesh Topology

Highly fault-tolerant

Partial-Mesh Topology

Trade-off between fault tolerance and cost

Connection to the Internet

Local Area Network

LAN Sizes

2.1 Giới thiệu về mạng Ethernet.

started a project, called Project 802, to set

standards to enable intercommunication among equipment from a variety of

manufacturers Project 802 does not seek to replace any part of the OSI or the Internet model Instead, it is a way of specifying

functions of the physical layer and the data

2.1 Giới thiệu về mạng Ethernet.

into two sublayers: logical link control

(LLC) and media access control (MAC).

IEEE has also created several physical layerstandards for different LAN protocols.

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2.1 Giới thiệu về mạng Ethernet.

traditional OSI model

LAN Standards

2.1 Giới thiệu về mạng Ethernet.

2.1 Giới thiệu về mạng Ethernet.

 Data Link Layer:

1)Logical Link Control (LLC) :

In IEEE Project 802, flow control, error control, and part ofthe framing duties are collected into one sublayer called the

logical link control

The LLC provides one single data link control protocol for allIEEE LANs.

A single LLC protocol can provide interconncctivity betweendifferent LANs because it makes the MAC sublayertransparent.

The purpose of the LLC is to provide flow and error controlfor the upper layer protocols that actually demand these

2.1 Giới thiệu về mạng Ethernet.

2)Media Access Control (MAC):

802.3 MAC frame

2.1 Giới thiệu về mạng Ethernet.

IEEE Project 802 has created a sublayer called

media access control that defines the specific access method for each LAN

For example, it defines CSMA/CD as the media access method for Ethernet LANs and the token passing method for Token Ring and Token Bus LANs

In contrast to the LLC sublayer, the MAC sublayer contains a number of distinct modules; each defines the access method and the framing format specific to the corresponding LAN protocol.

MAC Address Components

2.1 Giới thiệu về mạng Ethernet.

MAC addresses:

2.1 Giới thiệu về mạng Ethernet.

on the implementation and type of physical

specifications for each LAN implementation.

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2.1 Giới thiệu về mạng Ethernet.

b) Ethernet:

The original Ethernet was created in 1976 atXerox's Palo Alto Research Center (PARC).Since then, it has gone through four generations:Standard Ethemet (10 Mbps), Fast Ethemet (100Mbps), Gigabit Ethemet (1 Gbps), and TenGigabit Ethemet (10 Gbps).

Ethernet Evolution

2.1 Giới thiệu về mạng Ethernet.

CSMA/CD

Ethernet Frame Structure

Communicating Within the LAN

2.1 Giới thiệu về mạng Ethernet.

Ethernet evolution through four generations

2.1 Giới thiệu về mạng Ethernet.

1) Standard Ethernet :

2.1 Giới thiệu về mạng Ethernet.

-Frame Format :

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2.1 Giới thiệu về mạng Ethernet.

-Frame Length :

2.1 Giới thiệu về mạng Ethernet.

-Addressing : Each station on an Ethernet network (such as aPC, workstation, or printer) has its own network interface card(NIC) The NIC fits inside the station and provides the stationwith a 6-byte physical address.

Example of an Ethernet address in hexadecimal notation:

2.1 Giới thiệu về mạng Ethernet.

Unicast, Multicast, and Broadcast Addresses: Asource address is always a unicast address-theframe comes from only one station Thedestination address, however, can be unicast,multicast, or broadcast.

2.1 Giới thiệu về mạng Ethernet.

- Access Method: CSMA/CD

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2.1 Giới thiệu về mạng Ethernet.

2.1 Giới thiệu về mạng Ethernet.

 Encoding in a Standard Ethernet implementation:

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2.1 Giới thiệu về mạng Ethernet.

2)Fast Ethernet

The goals of Fast Ethemet can be summarized:

Upgrade the data rate to 100 Mbps.

Make it compatible with Standard Ethernet.

Keep the same 48-bit address.

Keep the same frame format.

Keep the same minimum and maximum frame lengths.

2.1 Giới thiệu về mạng Ethernet.

 MAC Sublayer

-Autonegotiation: is a new feature added to Fast

negotiate the mode or data rate of operation

- Autonegotiation was designed particularly for thefollowing purposes:

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2.1 Giới thiệu về mạng Ethernet.

2.1 Giới thiệu về mạng Ethernet.

 Physical Layer.

- Topology :

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2.1 Giới thiệu về mạng Ethernet.

-Implementation

2.1 Giới thiệu về mạng Ethernet.

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2.1 Giới thiệu về mạng Ethernet.

3) Gigabit Ethernet

The goals of the Gigabit Ethernet design can be summarized as follows:

Upgrade the data rate to 1 Gbps.

Make it comoatible with Standard or Fast Ethernet.

Use the same 48-bit address.

Use the same frame format.

Keep the same minimum and maximum frame lengths.

To support autonegotiation as defined in Fast Ethernet

2.1 Giới thiệu về mạng Ethernet.

The maximum length of the cable is determined bythe signal attenuation in the cable

2.1 Giới thiệu về mạng Ethernet.

The half-duplex approach uses CSMA/CD.

The maximum length of the network in this approach is totallydependent on the minimum frame size Three methods havebeen defined: traditional, carrier extension, and framebursting

2.1 Giới thiệu về mạng Ethernet.

 Physical Layer

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2.1 Giới thiệu về mạng Ethernet.

-Implementation

2.1 Giới thiệu về mạng Ethernet.

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2.2 Kết nối mạng cục bộEthernet.

 Connecting devices

Five categories of connecting devices

2.2 Kết nối mạng cục bộEthernet.

-Passive hub is just a connector.

-Passive hub connects the wires coming from differentbranches.

- In a star-topology Ethemet LAN, a passive hub is just apoint where the signals coming from different stationscollide; the hub is the collision point This type of a hub ispart of the media; its location in the Internet model is belowthe physical layer.

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2.2 Kết nối mạng cục bộEthernet.

2.2 Kết nối mạng cục bộEthernet.

-A repeater is a device that operates only in the physicallayer.

-Signals that carry information within a network can travel afixed distance before attenuation endangers the integrity ofthe data.

-A repeater connects segments of a LAN

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2.2 Kết nối mạng cục bộEthernet.

2.2 Kết nối mạng cục bộEthernet.

repeater It is normally used to create connectionsbetween stations in a physical star topology Hubs canalso be used to create multiple levels of hierarchy

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2.2 Kết nối mạng cục bộEthernet.

link layer.

addresses in a frame

2.2 Kết nối mạng cục bộEthernet.

A bridge connecting two LANs

2.2 Kết nối mạng cục bộEthernet.

 Routers

A router is a three-layer device that routes packets

based on their logical addresses (host-to-hostaddressing) A router normally connects LANs andWANs in the Internet and has a routing table that isused for making decisions about the route Therouting tables are normally dynamic and are updatedusing routing protocols

2.2 Kết nối mạng cục bộEthernet.

Routers connecting independent LANs and WANs

2.2 Kết nối mạng cục bộEthernet.

 Gateway

A gateway is normally a computer that operates in all fivelayers of the Internet or seven layers of OSI model Agateway takes an application message, reads it, andinterprets it This means that it can be used as a connectingdevice between two internetworks that use different models.For example, a network designed to use the OSI model canbe connected to another network using the Internet model.The gateway connecting the two systems can take a frame asit arrives from the first system, move it up to the OSIapplication layer, and remove the message

2.2 Kết nối mạng cục bộEthernet.

2.2 Kết nối mạng cục bộEthernet.

Operate at Layer 2 of the OSI model

Forward, filter, or flood frames

Have few ports



2.2 Kết nối mạng cục bộEthernet.

LAN Switch

High port density

Large frame buffers

Mixture of port speeds

Fast internal switching

Switching modes:

–Fragment-free

2.2 Kết nối mạng cục bộEthernet.

Transmitting Frames through a Switch

2.2 Kết nối mạng cục bộEthernet.

2.2 Kết nối mạng cục bộEthernet.

How Switches Learn Host Locations

2.2 Kết nối mạng cục bộEthernet.

•Station A sends a frame to Station C

•Switch caches station A MAC address to port E0 by learning the source address of data frames

•The frame from station A to station C is flooded out to all ports except port E0 (unknown unicasts are flooded)

2.2 Kết nối mạng cục bộEthernet.

•Station D sends a frame to station C

•Switch caches station D MAC address to port E3 by learning the source Address of data frames

•The frame from station D to station C is flooded out to all ports except port E3 (unknown unicasts are flooded)

2.2 Kết nối mạng cục bộEthernet.

How Switches Filter Frames

• Station A sends a frame to station C

• Destination is known, frame is not flooded

2.2 Kết nối mạng cục bộEthernet.

Broadcast and Multicast Frames

•Station D sends a broadcast or multicast frame

•Broadcast and multicast frames are flooded to all ports other than the originating port

2.2 Kết nối mạng cục bộEthernet.

Loops

2.2 Kết nối mạng cục bộEthernet.

Spanning tree protocol

2.4 Quá trình phân phối gói tin từ host to host thông qua switch

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Layer 2 Addressing

Assigned to end devices

Layer 3 Devices and Their Function

The network layer provides connectivity and path selection between two host systems.

In the host, this is the path between the data link layer and the upper layers of the NOS

In the router, it is the actual path across the network

Layer 3 Addressing

OSI uses NSAP

TCP/IP uses IP

Host-to-Host Packet Delivery (1 of 10) -UDP

Host-to-Host Packet Delivery (2 of 10)

Host-to-Host Packet Delivery (3 of 10)

Host-to-Host Packet Delivery (4 of 10)

Host-to-Host Packet Delivery (5 of 10)

Host-to-Host Packet Delivery (6 of 10)

Host-to-Host Packet Delivery (7 of 10)

Host-to-Host Packet Delivery (8 of 10)

Host-to-Host Packet Delivery (9 of 10)

Host-to-Host Packet Delivery (10 of 10)

Host-to-Host Packet Delivery (1 of 22)-TCP

Host-to-Host Packet Delivery (2 of 22)

Host-to-Host Packet Delivery (3 of 22)

Host-to-Host Packet Delivery (4 of 22)

Host-to-Host Packet Delivery (5 of 22)

Host-to-Host Packet Delivery (6 of 22)

Host-to-Host Packet Delivery (7 of 22)

Host-to-Host Packet Delivery (8 of 22)

Host-to-Host Packet Delivery (9 of 22)

Host-to-Host Packet Delivery (10 of 22)

Host-to-Host Packet Delivery (11 of 22)

Host-to-Host Packet Delivery (12 of 22)

Host-to-Host Packet Delivery (13 of 22)

Host-to-Host Packet Delivery (14 of 22)

Host-to-Host Packet Delivery (15 of 22)

Host-to-Host Packet Delivery (16 of 22)

Host-to-Host Packet Delivery (17 of 22)

Host-to-Host Packet Delivery (18 of 22)

Host-to-Host Packet Delivery (19 of 22)

Host-to-Host Packet Delivery (20 of 22)

Host-to-Host Packet Delivery (21 of 22)

Host-to-Host Packet Delivery (22 of 22)

Default Gateway