This document provides an overview of networking concepts including network components, layers of the OSI model, network structures, IP addressing, subnetting, routing, and TCP/IP protocols. Key points covered include the core, distribution, and access layers of a network hierarchy; functions of the physical, data link, network, and transport layers; MAC addressing; IP addressing classes and subnetting; TCP and port numbers; and routing protocols.

1. Networking Basics

2. Defining components of the
network
home
office
internet
mobile
users
Branch office Main Office

3. Network Structure Defined by
Hierarchy
Core
Layer
Distribution
Layer
Access
Layer

4. Access Layer Characteristics
Access
Layer
End Station entry point to the network

5. Distribution Layer
Characteristics
•Access Layer Aggregation Point
•Routes Traffic
•Broadcast/Multicast Domains
•Media Translation
•Security
•Possible point for remote access

6. Core Layer Characteristics
•Fast Transport to enterprise services
•No packet manipulation

7. TCP/IP Protocol Layers
Application
Presentation
Session
Transport
Network
Data Link
Physical
OSI Reference Model

8. OSI Model Overview
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application Layers
Data Flow Layers
Telnet, FTP
JPEG, ASCII
Operating System
TCP, UDP, SPX
IP, IPX
HDLC
EIA/TIA-232
V.35

9. Encapsulating/Decapsulating
Data
Application
Presentation
Session
Transport
Network
Data Link
Physical
Application Layers
Data Flow Layers
PDU
PDU
PDU
Segment
Packet
Frame
Bits

10. Physical Layer Functions
Defines: Media type
Connector Type
Signaling type
• Only one station on a shared Ethernet segment can send a frame at one time but all
Stations receive and look at the frame to determine if it is for them
• All end stations on a segment that hear all the traffic on the wire are in the same
collision domain.
• Station that are in the same collision domain are always in the same broadcast domain

11. Hubs Operate at Physical Layer
HUBS ARE USED TO EXTEND THE PHYSICAL MEDIA
• All devices in the same collision domain
• All devices in the same broadcast domain
• Devices share the same bandwidth

12. Hubs: One Collision Domain
• More end stations means more collisions
• CSMA/CD is used

13. LAN Physical Layer
Physical Layer Implementations Vary
MODULE TYPE HALF/FULL DUPLEX
Ethernet 10base2 185m max
Coax (802.3) 10base5 500m max
Cat 3,4,5(2-pair) 10BaseT 100/100m
Cat 5 (2-pair)-802.3u 100BaseTX 100/100m
Multimode Fiber 10BaseFL 2/2Km
-802.3u- 100BaseFX 400/2Km
Single Mode Fiber-802.3u-100BaseFX10/10Km

14. UTP device
RJ-45 Connector
PIN WIRE PAIR
1 Pair 3
T2
2 Pair 3 R2
3 Pair 2 T3
4 Pair 1 R1
5 Pair 1 T1
6 Pair 2 R3
7 Pair 4 T4
8 Pair 4 R4
RJ-45 Straight: 1-to-1, 2-to-2 e.t.c.
RJ-45 Crossover: 1-to-3, 2-to-6 e.t.c.

15. WAN Physical Layer
Physical Layer Implementations Vary
HDLC PPP FRAME RELAY ISDN BRI (WITH
PPP)
EIA/TIA-232 RJ-45
EIA/TIA-449
(greater distance than 232,for same bit rate) Note: Pinouts are
X.21 V.24 V.35 HSSI different than
LAN RJ-45
DTE (Router’s
interface)
• End of user’s device on
the WAN link (Router’s
interface)
DCE (e.g. modem)
• End of the WAN provider’s
side of the communication
facility
• DCE is responsible for
clocking

16. Data Link Layer Functions
DEFINES:
• Physical source and destination addresses
• Network topology
• Frame sequencing
• Flow Control
• Connection-oriented or Connectionless

17. Data Link Layer Functions (continued)
8 6 6 2 Variable 4
Preamble Destinat
Address
Source
Addres
s
Length Data FCS
MAC ADDRESS
0000.0C XX.XX.XX
IEEE assigned Vendor assigned

18. MAC Address

19. Switches and Bridges Operating at
Layer 2
• Each segment (port) has its own collision domain
• ALL segments are in the same broadcast domain
• Layer-2 switching is hardware-based bridging (ASIC)
• Layer-2 bridging is software-based
• Bridges can have up to 16 ports
• One STP/BRIDGE, many STP/switch
• All segments must use the same data link implementation (Ethernet
or token ring for example) otherwise need router for translation
• One device/segment can send frames at the same time

20. Internet Layer Overview
Internet Protocol (IP)
Internet Control Message
Protocol (ICMP)
Address Resolution
Protocol (ARP)
Reverse Address
Resolution Protocol
(RARP)
Application
Transport
Internet
Data Link
Physical
OSI network layer corresponds to
the TCP/IP internet layer

21. Network Layer Functions
IP Header Source
Address
Destination
Address
Data
Logical Address 172.15.1.1
Two types of Network Layer Packets
• Network Layer Data Packets- Include upper layer control/user data
• Route Discovery/Update Packets- Sent between routers (include information about
e.g. distance between two networks, information for how to reach this network)
• Need to know addressing which usually provide hierarchy in the network

22. Network Layer Functions (continued)
1.0
1.2 1.1
2.1 2.2
3.0
3.2
3.1
Routing Table Routing Table
Network Interface Metric
1 E0 0
2 S0 0
4 S0 1
Network Interface Metric
1 S0 1
2 S0 0
4 E0 0

23. Introduction to TCP/IP
Addresses
172.18.0.1
172.18.0.2
172.16.0.1
172.17.0.1
172.17.0.2
172.16.0.2
10.13.0.0 192.168.1.0
10.13.0.1
192.168.1.1
HDR SA DA DATA

24. IP Addressing
Address Mask
172.16.122.204 255.255.0.0
10101100 00010000 01111010 11001100
11111111 11111111 00000000 00000000
NETWORK HOST

25. IP Addressing

26. IP Address Classes

27. IP Address Classses

28. IP Address Classes

29. Determining Available Host
Addresses

30. Subnet Addressing
172.16.2.200
172.16.2.2
172.16.2.160
172.16.2.1
172.16.3.1
E0
E1
172.16.3.5
172.16.3.100
172.16.3.150
172.16 . 2 . 160
Network Subnet Host

31. Subnet Mask

32. Decimal Equivalents of Bit Patterns

33. Subnet Mask without Subnets

34. Subnet Mask with subnets
• Network Extended by Eight Bits

35. Subnet Mask with Subnets
• Network Number extended by ten bits

36. Broadcast Addresses
172.16.1.0
172.16.3.0
172.16.2.0
172.16.4.0
172.16.3.255
(Directed Broadcast)
255.255.255.255
(Local Network broadcast)
172.16.255.255
(all subnets broadcast)

37. Exercise
ADDRESS CLASS NETWORK HOST
10.2.2.1
128.63.2.100
201.222.5.64
192.6.141.2
256.241.201.10
130.113.64.16

38. Exercise Subnet Mask
ADDRESS CLASS NETWORK HOST
172.16.2.10 255.255.255.0
10.6.24.20 255.255.240.0
10.30.36.12 255.255.255.0

39. Exercise Broadcast address
ADDRESS Subnet Mask Class Subnet Broadcast
201.222.10.60 255.255.255.248
15.16.193.6 255.255.248.0
128.16.32.13 255.255.255.252
153.50.6.27 255.255.255.128

40. Finding the IP address of the LAN

41. Address Resolution Protocol
172.16.3.1 172.16.3.2
IP: 172.16.3.2 = ???
IP: 172.16.3.2
Ethernet: 080A.0B20.118C
Map IP MAC
I need the Ethernet
address of 176.16.3.2
Local ARP
I heard that
broadcast. The
message is for me.
Here is my Ethernet
address

42. Reverse ARP
Ethernet: 080A.0B20.118C IP=???
Ethernet: 080A.0B20.118C
IP: 172.16.3.2
Map MAC IP
What is my IP
Adress?
I heard that
broadcast. Your IP
address is
172.16.3.25

43. What is a Variable-Length Subnet Mask?
172.16.14.32/27
A
172.16.14.64/27
B
172.16.14.96/27
C
172.16.14.132/30
172.16.14.136/30
172.16.14.140/30
172.16.1.0/24
HQ 172.16.0.0/16
172.16.2.0/24

44. Calculating VLSMs
172.16.32.0/26
172.16.32.64/26
172.16.32.128/26
172.16.33.0/30
172.16.33.4/30
172.16.33.8/30
HQ
172.16.33.12/30 172.16.32.192/26
Derived from the
172.16.33.0/26 subnet
30-bit mask
(2 hosts) 26-bit mask
(62 hosts)
Derived from the 172.16.32.0/20 Subnet

45. Exercise: Calculating VLSMs
25 Users
25 users
25 users
HQ
25 users
Using VLSMs, define appropriate subnets for addressing the networks using 192.168.49.0/24
25 users
A
B
C
D
E
HQ
Address for WAN links
A Serial______________
B Serial______________
C Serial______________
D Serial______________
E Serial______________
A
B
C
D
E

46. What is Route Summarisation?
172.16.25.0/24
172.16.26.0/24
172.16.27.0/24
A B
Routing Table
172.16.25.0/24
172.16.26.0/24
172.16.27.0/24
I can route to thw
172.16.0.0/16
Routing Table
172.16.0.0/16
network
• Routing protocols can summarize addresses of
several networks into one address

47. Summarizing within an Octet

48. Summarizing Addresses in a VLSM
-Designed Network
172.16.128.0/20
B
172.16.14.64/26
C
172.16.64.0/20
D
A
172.16.14.128/26
172.16.128.0/20
172.16.32.0/24
172.16.64.0/20
172.16.0.0/16
Corporate
Network

49. Implementation Considerations
• Multiple IP addresses must have the same
highest-order bits
• Routing decisions are made based on the
entire address
• Routing protocols must carry the prefix
(subnet mask) length

50. Route Summarization Operation in Cisco
Routers
172.16.5.33 /33 Host
172.16.5.32 /27 Subnet
172.16.5.0 /24 Network
172.16.0.0 /16 Block of Networks
0.0.0.0 /0 Default
• Supports host-specific routes,
blocks of networks, default routes
• Routers use the longest path

51. Routers: Operate at the Network
Layer
• Broadcast control
• Multicast control
• Optimal Path
Determination
• Traffic Management
• Logical Addressing
• Connects WAN services

52. Transport Layer Functions
• Distinguishes between upper layer applications
• Establishes end-to-end connectivity between applications
• Defines flow control
• Provides reliable/unreliable services for data transfer

53. TCP Segment Format
Source Port (16) Destination Port (16)
Sequence Number (32)
Acknowledgement Number (32)
Header Length (4) Reserved (6) Code Bits (6) Window (16)
Checksum (16) Urgent (16)
Options (0 or 32 if any)

54. Port Numbers
FT
P
T
EL
NET
S
MT
P
DNS TFT
P
S
N
MP
R
I
P
21 23 25 53 69 161 520
TCP UDP

55. TCP Port Numbers
Source Telnet Z Port Dest Port ...
Host A Host Z
SP DP
1028 23 ...
Dest. port = 23.
Send packet to
my Telnet
application

56. TCP Three way Handshake/Open
Connection
Host A

Send SYN (seq=100 ctl=SYN)
SYN received
Established (seq=101
ack=301 ctl=ack)

Host B
SYN received
 Send SYN, ACK (seq=300
ack=101 ctl=syn, ack)

57. TCP Simple Acknowledgment
Send 1
Receive ACK 2
Send 2
Receive ACK 3
Send 3
Receive ACK 4
Send 1
Receive ACK 2
Send 2
Receive ACK 3
Send 3
Receive ACK 4
Window size = 1

58. TCP Sequence and Acknowledgment
Numbers
Source Port Dest Port Sequence #
I just
sent #11
I just got #11,
now I need #12
Acknowledgment # ...
Source Dest. Seq. Ack.
1028 23 10 100
Source Dest. Seq. Ack.
1028 23 11 101
Source Dest. Seq. Ack.
1028 23 100 11
Source Dest. Seq. Ack.
1028 23 101 12

59. TCP Windowing
Window size = 3
Send 1
Window size = 3
Send 2
Window size = 3
Send 3
Window size = 3
Send 3
Window size = 3
Send 4
Window size = 3
ACK 3
Window size = 2
ACK 5
Window size = 2
Receiver
Packet 3 is dropped
Sender

60. UDP Segment Format
Source port (16) Destination Point
Length (16) Checksum (16)
Data (if any)
No sequence or acknowledgment fields