Data Link Issues: Relates To Lab 2
Data Link Issues: Relates To Lab 2
Data Link Issues: Relates To Lab 2
Relates to Lab 2.
This module covers data link layer issues, such as local area networks
(LANs) and point-to-point links, Ethernet, and the Point-to-Point Protocol
(PPP).
Application
Layer
Application
Layer
Transport
Layer
Network
Layer
(Data) Link
Layer
Presentation
Layer
Session
Layer
Transport
Layer
Network
Layer
(Data) Link
Layer
Physical
Layer
TCP/IP Suite
OSI
Reference
Model
Network
Layer
Data Link
Layer
Data Link
Layer
Physical
Layer
Physical
Layer
Types of Networks
There are two types of communication networks:
Broadcast Networks: All stations share a single
communication channel
Point-to-Point Networks: Pairs of hosts (or routers) are
directly connected
Broadcast Network
Point-to-Point Network
Typically, local area networks (LANs) are broadcast and wide area
networks (WANs) are point-to-point
Bus LAN
Ring LAN
Data Link
Layer
802.1
Logical Link
Control
802.2
802.6
802.5
802.4
802.3
Medium
Access
Control
Physical
Layer
Higher
Layer
Data Link
Layer
Physical
Layer
Ethernet
Speed:
Standard:
10-1000 Mbps
802.3, Ethernet II (DIX)
10Base-T
10Base2
100Base-TX
100Base-FX
1000Base-FX
Bus Topology
10Base5 and 10Base2 Ethernets have a bus topology
Star Topology
With 10Base-T, stations are connected to a hub in a star
configuration
Hub
10
Hub
Switch
CSMA/CD
CSMA/CD
CSMA/CD
CSMA/CD
CSMA/CD
CSMA/CD
CSMA/CD
CSMA/CD
CSMA/CD
CSMA/CD
CSMA/CD
CSMA/CD
CSMA/CD
HighSpeed
Backplane
CSMA/CD
CSMA/CD
CSMA/CD
Input
Buffers
Output
Buffers
11
12
802.3 MAC
destination
address
source
address
type
data
CRC
46-1500
0800
IP datagram
38-1492
0806
ARP request/reply
28
0835
RARP request/reply
28
PAD
10
PAD
10
13
802.3 MAC
802.2 LLC
802.2 SNAP
destination
address
source
address
length
DSAP
AA
SSAP
AA
cntl
03
org code
0
type
data
CRC
38-1492
0800
IP datagram
38-1492
0806
ARP request/reply
PAD
28
10
0835
RARP request/reply
PAD
28
0xaa
10
14
Access
Router
Modems
Dial-Up Access
Router
Router
Router
Router
Point-to-Point Network
15
PPP - IP encapsulation
The frame format of PPP is similar to HDLC and the 802.2
LLC frame format:
flag
addr
ctrl
7E
FF
03
protocol
data
CRC
flag
7E
<= 1500
0021
IP datagram
C021
8021
16
PPP
Other than a framing method PPP provides:
The link control protocol (LCP) which is responsible for
establishing, configuring, and negotiating a data-link
connection
LCP is specified in RFC 1331.
For each network layer protocol supported by PPP, there is
one network control protocol (NCP)
The NCP for IP is specified in RFC 1332
17