Welcome to
Network technology I, 7.5 ECTS
Magnus.eriksson@miun.se, teaches part CCNA 1
Lennart.franked@miun.se, teaches part CCNA 2
Föreläsningsmaterialet är författat av Magnus Eriksson. Material är även hämtat från
läroboksförfattaren Behrouz Fourozan.
2
Network Technology I
This course presents fundamental concepts of computer
networks. You get practical experience of commands for
troubleshooting and configuration of switches and routers.
The course content corresponds to CCNA Exploration part 1
(Network fundamentals) and 2 (Routing protocols and
concepts). Together with Network Technologies II (i.e.
CCNA part 3 and 4) this course facilitates makes you
eligible to Cisco Academy’s CCNA certification at an
external certifier.
Cisco CCNA certification
 Network technology I, 7.5 hp:
 Cisco Academy CCNA 1 (Network fundamentals).
 CCNA 2 (Routing). Require CCNA 1.
 Network technology II, 7.5 hp
 CCNA 3. Requires CCNA 1 and 2.
 CCNA 4. Requires CCNA 1, 2 and 3.
 Offered in period 4
 After that you are eligible for CCNA certification
at some commercial education company.
4
Course organization
 Each subcourse (e.g. CCNA 1 and CCNA 2 respectivel) consists of:






About 10 chapter self-tests.
About 10 chapter tests (assessments), Rekommendation: 70% correct on each test!
A practice final assessment. 70% required before you can take the final exam.
A supervised final exam in Sundsvall. 70% required for passing.
lab exercises. (CCNA 1: Lab 1.1, 1.2. CCNA 2: Lab 2. In Moodle)
feedback form. Must be filled in before you can be registered on next subcourse.
 Each test and exam takes between 75 and 90 minutes, and
consists of multiple choice questions.
 You will have problems if you only learn the answers by
heart. You must also understand them, otherwize it will be
impossible for you to pass the last labs.
5
Register
At student portal as well as http://cisco.netacad.net.
See Moodle for more information.
6
Amount of information
-
-
Think about a number between 0 and 15. I am now going to guess it using as
few yes and no questions as possible. I start by asking: Is the number larger
than or equal to 8?
Yes
Is it larger than or equal to 12? (The interval is successively divided by 2.)
No.
Is the number larger than or equal to 10?
Yes
Is the number larger than or equal to 9?
Yes.
The amount of information you give me when you tell me that the number is 9
is 4 bits, because the amount of information in bits is the minimum
number of yes and no questions that are required. We had 16 options,
which is = 24 = 2·2·2·2, corresponding to 4 bits. If the number of options was
32 = 25 , it would require 5 bits.
If yes is represented by the binary digit ”1”, and no by ”0”, the value in the
above example can be represented by 1 0 1 1.
7
Bits and Bytes
 N bit can represent M=2N different values.
 M values can be represented by
N = 2log M =log M / log 2 values
 Example: The N=7 bit ASCII character code
consists of M=128 codes.
 8 bits = 1 byte (a unit for measuring amount of data)
 1 kbit = 1000 bit (previously 1024 bit).
 1 Mbit = 1000 kbit (previously 1024 kbit).
 1 Gbit = 1000 Mbit.
 1 Tbit = 1000 Gbit.
8
Range of data communication techniques
0.1 m
1m
10 m
100 m
1 km
Circuit board
Example: EISA
System
Room
Serial/parallel ports
Personal Area Networks (PAN)
Building
Campus
Local area Networks (LAN)
10 km
100 km
City
Country
1000 km
Continent
10,000 km
I/O bus
Planet
Example: RS232 (”com port”), USB, Firewire,
Bluetooth, IEEE 802.15 WPAN
Example: Ethernet, IEEE 802.11 WLAN
Metropolitan Area Networks
(MAN)
Example: Ethernet, ATM, FDDI, IEEE 802.16
Wide Area Networks (WAN)
Example: The Internet.
The Public Service Telephone Network (PSTN)
9
Figure 2.17
The OSI seven layer model
10
The Layers of OSI Model
End
System
R
Application
Presentation
Intermediate
System
Application
Presentation
Session
Session
Transport
Network
Transport
Network
Data Link
Physical
Network
Data Link
Physical
Data Link
Physical
11
Summary of OSI Layer Functions
Application
To translate, encrypt and
compress data
Presentation
Session
To provide reliable end-toend message delivery and
error recovery
To organize bits into
frames, to provide nodeto-node delivery
To allow access to network
resources
Transport
Network
Data Link
Physical
To establish, manage and
terminate sessions
To move packets from source
to destination; to provide
internetworking
To transmit bits over a
medium; to provide
mechanical and electrical
specifications
12
Figure 2.2
The TCP/IP five layer model
Example protocols:
HTTP, SMTP,
FTP, Telnet
TCP, UDP
IP
Ethernet,
PPP over
modems
Only four layers in Cisco literature! Layer 1 and 2 are
merged to a ”Network access layer” or ”Link layer”.
The network layer is called Internet layer.
13
Figure 2.4
An exchange using the Internet model
H – header (pakethuvud): control data added at the front end of the data unit
T – trailer (svans): control data added at the back end of the data unit
Trailers are usually added only at layer 2.
14
Figure 2.3
Peer-to-peer processes
Protocol N on device A and on B are peers (”varandras likar”).
15
Adresses to my computer





Physical MAC address, 48 bits: 00-00-E2-4F-54-04
Public IP address, 32 bitar: 193.10.250.187.
Private NAT IP address (Network Address Translation): 10.14.1.63.
IP subnet mask: 255.255.0.0
DNS name (Domain namn Service): mageripc.itm.miun.se, där
itm.miun.se is DNS suffix, and .se top domainn.
 URL to web page at web server at my computer:
http://mageripc.itm.miun.se:portnummer/filkatalog/filnamn.typ
Port number is default 80. Many computers in the world has DNS alias
”www”.
 URL to ftp file at my computer:
ftp://användanamn:lösenord@mageripc.itm.miun.se/filkatalog/filnamn.typ
 Windows file name for file if shared disk access of my computer:
\\mageripc.itm.miun.se\directory\filename.type .
 E-mail address to user at an e-mail server at my computer:
användarnamn@mageripc.itm.miun.se
16
Systems and protocols for
address translation
 ARP (Address resolution protocol) transaltes IP address to physical
address.
 DHCP (Dynamic Host Configuration Protocol) might give every
computer a free IP address.
 DNS (Domain Name Server) translates IP address to/from DNS
name.
 NAT (Network Address Translation) is a proxy server, often part of
the network firewall, that modifies IP packet by replaceing the private
source IP address and port number by its public IP address and port
number, and vice versa when receiving data. Thus several computers
can share one IP address.
17
Figure 2.5
Physical layer
18
Note:
The physical layer is responsible for
transmitting individual bits from one
node to the next.
Example: RS232 (the serial “com” port)
19
Lager 1
Physical layer duties:
•Contacts
•Electrical levels
•Modulation (Passband transmission)
•Pulse coding (Baseband transmission)
•Multiplexing
•Bit synchronization
•Circuit switching
Example: RS232 (“com”-porten)
20
Figure 2.6
Data link layer/Network access layer
21
Note:
The data link layer is responsible for
transmitting frames from
one node to the next.
22
Lager 2
Datalänklagret är protokoll för transmission av ramar
(frames) från en nod till nästa. Detta kan innefatta:
•Fleraccessprotokoll (multiple access control=MAC)
för att undvika kollisioner
•Adressering inom LAN:et/länken (nätverkskortens
fysiska MAC-adresser eller nivå 2-adress).
•Felhantering (t.ex. vid trådlös kommunikation eller
telefonnätsmodem)
Exempel: Ethernet ligger på lager 1 och 2.
23
Figure 2.7
Node-to-node delivery
24
Figure 2.8
Example 1
I Figure 2.8 sänder en nod med fysisk adress 10 en ram (dvs ett
paket på nivå 2) till en nod med fysisk adress 87. De två noderna är
förbundna med en länk. Ramens huvud (header H2) innehåller bl.a.
avsändarens och mottagarens fysiska adress. Ibland används en
svans (trailer T2) som innehåller felrättande och/eller
25
felupptäckande kod.
Example 1
In Figure 2.8 a node with physical address 10 sends a
frame to a node with physical address 87. The two nodes
are connected by a link. At the data link level this frame
contains physical addresses in the header. These are the
only addresses needed. The rest of the header contains
other information needed at this level. The trailer usually
contains extra bits needed for error detection
26
Figure 2.9
Network layer/Internet layer/Internetwork layer
27
Note:
The network layer is responsible for
the delivery of packets from the
original source to the
final destination.
28
Lager 3
Nätverkslagret ansvarar för
vidareförmedling av paket “end-to-end”, dvs
via kedjan av datalänkar från den
ursprungliga källan till den slutliga
destinationen. Detta innefattar WANadressering (t.ex. IP-adresser) och
routingprotokoll.
Exempel: IP-protokollet.
29
Figure 2.10
Source-to-destination delivery
30
Figure 2.11 Example 2
I figur 2.11 vill vi sända data från
en nod med logisk nätverksadress
(IP-adress) A och fysisk adress 10
till en nod med IP-adress P och
fysisk adress 95. De två enheterna
befinner sig i olika LAN. Därför
kan vi inte enbart använda deras
fysiska adress. Den fysiska
adressen kan enbart användas vid
kommunikation inom ett LAN.
De två routrarna förstår av IPadressen vilken väg paketen ska
vidareförmedlas, och ändrar
paketets fysiska adressering.
31
Illustration of the Source-to-end Delivery at
the Network Layer
 Observe how data are sent from node to node to
reach the final destination.
Animation of Figure 2.11 in the book
32
Figure 2.12
Transport layer
33
Note:
The transport layer is responsible for
delivery of a message from one process
to another.
34
Figure 2.12
Reliable process-to-process delivery of a message
35
Figure 2.14
Example 3
36
Example 3
Figur 2.14 exemplifierar transportlagret (UDPprotokollet). Data som kommer från högre lager förses
med en TCP-header, som innehåller portnummer j och k.
Avsändarprocessens portnummer är j och
mottagarprocessens portnummer är k. Eftersom
meddelandets storlek är större än nätverkslagret kan
hantera, delas datat i två segment (två paket).
Nätverkslagret lägger till nätverksadresserna (A och P)
till varje paket.
37
Lager 4
Transportlagret ansvarar för leverans av
meddelanden “end-to-end”, från en process på
avsändardatorn till en process på mottagardatorn.
Detta kan innefatta:
•portnummer,
•virtuell kretskoppling, dvs flödesstyrning,
felkontroll, segmentnumrering, omsändning,
ordning av segment. (TCP-protokollet. Ej UDPprotokollet.)
38
Figure 2.15
Application layer
39
Note:
The application layer is responsible for
providing services to the user.
40
Lager 5:
Applikationslagret är kommunikationsprotokoll för
att tillhandahålla en komplett
kommunikationstjänst till slutanvändaren.
Exempel:
•HTTP för web
•Telnet för terminalemulering.
•FTP för filöverföring.
•SMTP, POP3 och IMAP4 för Internet e-post
41
Figure 2.16
Summary of duties
42
Bandbredd kan betyda många saker
 Analog bandbredd i Hertz. Övre gränsfrekvens
minus undre gränsfrekvens.
 Net bit rate = Digital bandbreddskapacitet i Bit/s.
= Datatakt exklusive felupptäckande koder.
Net bit rate ≤ Gross bit rate
 Maximal genomströmninshastighet = Maximal
throughput
 Genomströmningshastighet = Throughput =
Digital bandbreddskonsumtion
 Goodput = Filöverföringshastighet
43