W4_Ether Basics1.pptx - Ethernet and Routing Basics I March...

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Ethernet and Routing
Basics I
March 2017

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Topics
1. Warm up
2. Layer 2 Ethernet Overview
3. ARP and ICMP

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1
Warm Up

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What Do We Know About Routing?

If you don’t know how to go to an address...
Somebody tells you!

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What Do We Know About Routing?

Same as process of telling somebody an address
Internet
I want to go to Google,
how can i go there?
hat is IP address of ?
=74.125.128.104
74.125.128.104
Web Server

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What Do We Know About Routing?

Computer asks the the way to 74.125.128.104 to
closest router
So how can i go to 74.125.128.104?
Internet
74.125.128.10

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What Do We Know About Routing?

Routing is:
o
Forwarding IP packets to the destination that they want to
reach based on the destination IP addresses in their header
!!!!

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Layer 3 Connects Multiple Layer 2 Networks
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Layer 3 Routing vs. Layer 2 Switching
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Internet
74.125.128.104

IP Routing is about forwarding datagrams end-to-
end , most often through multiple hops (routers)

Layer 2 Switching is about forwarding datagrams to
the immediate next-hop , which can be connected on
a point-to-point link, or a broadcast environment.
00:e0:b1:88:0d:c0 00:e0:b1:a4:38:fd 00:e0:b1:5a:e5:3c 00:b8:73:fb:c1:58
Broadcast Point-to-Point

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2
Layer 2 Ethernet Overview

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Layer 2 Overview
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Why do we need Layer 2?

Required for higher-layer data transfer
Characteristics of Layer 2

Scope Local network

Encapsulating the packet into a frame for Layer 2
forwarding

Layer 2 Framing

Addressing/Identification, MTU
Examples of Layer 2 Protocols

Ethernet, ATM , Frame Relay , TDM

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Scope of Data Link Layer
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
L2 frames are transmitted only to devices and hosts within the
same network

L2 networks are separated by routers

The PCs on the left side of Ethernet network do not require
anything than L2 Ethernet framing to communicate each other

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