Download UNIT name: IP protocol

UNIT name: ISO/OSI Model
o AIM of the unit
The student understands the meaning of layering in data transmission (protocols), why
it is important and what is good in it for internetworking.
The student is able to talk with partners about the different networking layers
The student understands that problems can be in different networking layers, when
network does not work properly.
o What are the PRIOR knowledge for unit – concepts what must be covered
before
o Theory (HTML text - possible with links to outside material and simple
flash)
1. ISO/OSI – is it standard?
Kind of… ISO 7498:1984 Open Systems Interconnection - Basic Reference Model:
- http://en.wikipedia.org/wiki/Open_Systems_Interconnection
- http://en.wikipedia.org/wiki/OSI_model
But in everyday life we use more TCP/IP (DARPA) reference model, used mostly as
Internet Protocol Suite with some other protocol standards by IEEE. Look for RFC’s:
- http://www.ietf.org/rfc.html
- http://www.graphcomp.com/info/rfc/
Source: http://www.microsoft.com/technet/itsolutions/network/evaluate/technol/tcpipfund/tcpipfund_ch02.mspx
In ISO/OSI, there is 7 layers defined, starting from physical to application, as showed
in the column “OSI model layers”. But ordinarily there is used 4 packages of layers,
as showed in the column “DARPA layers” (or
http://en.wikipedia.org/wiki/TCP/IP_model refers 5 leyers as Physical&Data-Link
separated). In everyday life we call these 4 layers:
1. physical (Network Interface Layer)
2. network (Internet Layer)
3. transport
4. application
Real protocols in these layers can be found in references listed before.
There is example how NetBIOS/SMB/CIFS works over TCP/IP:
7 Application
6 Presentation
5 Session
4 Transport
e.g. Browser Service
Higher level protocols e.g. SMB / CIFS
Name Service
datagram service
Session Service
UDP
3 Network
TCP
IP
e.g. IEEE 802.2
2 Datalink
e.g. Ethernet II etc
IEEE 802.3 / IEEE 802.5 etc
1 Physical
Token Ring / Ethernet etc
Source: http://timothydevans.me.uk/nbf2cifs/x2803.html
2. Why layering?
Layering is good for some different reasons:
- Simplification - We divide a problem of networking in to pieces – it
simplifies the rules, what one protocol must “do” and how it communicates
with other layers
- Interoperability - We open these simplified problems for opened research
and development. So everyone can develop “he’s own” protocol in some
layers and it can interoperate with others as it compatibles with others as
OSI model defines borders and aims for each layer.
- We used to it - this is as we act in ordinary life (Read about James Bond:
http://www.lewistech.com/rlewis/Resources/JamesBondOSI2.aspx). We are
communicating in some context (as application layer) as lecturers,
sometimes as friends etc. Communication uses some kind of language (as
transport layer), and of course it needs partners who communicate (as
network layer). You already understand that there must be some kind of
physical phenomenon to transport this communication to the partner (as
physical layer, including rules in physical environment like frequency etc.).
In reality this physical phenomenon can be computer network with all these
layers again, where voice carrier is application.
3. Functionality of layers
To understand principles of data transmission from one place to other thorough
ISO/OSI model layers (Look simulation).
1. The Physical layer defines all the electrical and physical specifications for
devices. Also (Datalink Layer in OSI) transfers data between network entities
and detects (and possibly corrects) errors that may occur in the Physical layer.
It covers Network Cards (NIC) and mostly all other active elements in
network, cables and radio resources, ADSL and Modem connections etc.
Read more: http://en.wikipedia.org/wiki/OSI_model#Layer_1:_Physical_Layer and
http://en.wikipedia.org/wiki/OSI_model#Layer_2:_Data_Link_Layer
2. The Network layer is responsible of transferring variable length data
sequences (packets) from a source to a destination. It is mostly dealing with
addresses and routing issues.
Read more: http://en.wikipedia.org/wiki/OSI_model#Layer_3:_Network_Layer
3.
The Transport layer provides transparent transfer of data between end users.
It is dealing with sessions, data fragmentation to frames and defragmentation
to data, error and flow control etc. Read more:
http://en.wikipedia.org/wiki/OSI_model#Layer_4:_Transport_Layer.
4. The Application layer is used by most programs for network communication
(API’s). Data is passed from the program in an application-specific format and
then encapsulated into a transport layer protocol.
Read more: http://en.wikipedia.org/wiki/TCP/IP_model#Application_layer
o Attachments (Videos, Simulations etc – describe!!!)
Starting slide:
changed to “Base Slide” in 3-5 seconds.
Application
B
Application
A (data to
send)
Network System as
„Black Box”
1. Channel is opened for data transport from Application A to B. It is kind of
tube from A to B and data as boxes are moving there. Explained as voice (or
in textbox) that: „for Application A the data transport starts with choosing
some kind of protocol in Application Layer level (HTTP, FTP, TELNET,
SMTP etc) and finding other application to communicate with (as there
defined Application named „B” which is waiting such kind of data transport
as server in some identifiable computer). And actually this is everything that
the Application needs to „know” about networking – nothing about network
cards, cables, routers, etc – they are inside of a network as „black box””
2. Next slide same as previous, but three levels are in both side as follows:
Application
A (data to
send)
Application
B
Network System as
„Black Box”
.... . Sometimes Presentation (6) and Session Layers (5) are used as separate
protocols, but ordinarily Application Layer (7) protocols define them together and
handle these layers itself for organizing data transport. Also, ordinarily there is
not testing utilities for these layers (or protocols) separately although they are
defined separately (as example of MS Windows Browsing service in Application
Layer, which uses SMB/CIFS protocol as Presentation Layer protocol and
different Session Layer protocols besides that. In everyday life we name this as
Windows Browsing or Samba (SMB) service, meaning all the package of these
protocols, and test the working status with some kind of application (Windows
Explorer, SMBCLIENT in Linux, etc). If one Application does not work in the
network, there is possibility, that this application is wrongly configured, or there
is problems in lower layers. You can test then some other applications first and
then if others are not working too, start to test lower layers.”
Words “Windows Browsing” can be linked to table in theory paragraph 1. “There
is example how NetBIOS works over TCP/IP”
3. We continue width the same kind of slide, but add 4. box to the both side and
put the Port number on that as follows
Application
B
Application
A (data to
send)
Network System as
„Black Box”
port 25
port 80
port ..
port 2345
“Transport Layer (4) is similar with other upper layers (5-7), but it is clearly
separated from applications and gives to Applications standardized way to
communicate with each other. Because of that standardization, it is possible to test
this layer separately with utilities (NETSTAT, port scanners etc). We can compare
this layer as a Bus station, where different applications must be recognized and
advertised for others as different numbered bus stations. All the data transport must
go thorough stations as we go on to the buses (or trains etc).
Transport layer communicates with Network layer (3), where data must be
fragmented into packets (as buses take with them some amount of people not more),
but similarly to upper layers, this layer does not know anything about network
structure (network cards, cables, distances etc). “
4. In the next slide there is no Black box, but some kind of networks as follows:
Net
Application
B
Application
A (data to
send)
port 25
port 80
port ..
IP: 192.168.22.110
port 2345
Network B
IP: 192.168.0.10
Network A
GATEWAY between two segments
IP: 192.168.0.1
IP: 192.168.22.1
“Network Layer (3) is different from upper layers. It defines one network as a
collection of active network nodes addressed with the same network address. It is
good (actually important), that different networks are routable in Network Layer
level, because then routers (gateways) can manage data transport with only Network
(and lower) Layer protocols with no need to “know” anything about the upper level
protocols… Otherwise instead of routers there is need for proxies for transporting
data from one network to another using upper level protocols and rules.
Although networks defined in Network Layer are independent of lower layers
topology, typically they cover Physical Network Segments one on one. You can test
Network Layer with IPCONFIG, PING, TRACEROUTE or other such kind of utilities.
”
5. Datalink and Physical level protocols will be added as “Network Interface” on
next slide
Application
B
Application
A (data to
send)
port 25
port 80
port ..
IP: 192.168.22.110
MAC: 00:AB:65:A1:34:21
port 2345
Radio antenna
IP: 192.168.0.10
MAC: 00:FF:AB:9C:78:A6
Segment B radio recources
Connector RJ-45
GATEWAY between two segments
Segment A Cables
HUB (Signal amplifier)
IP: 192.168.0.1
Conn. RJ-45
Conn. RJ-45
MAC: 00:FF:AB:9C:AF:1B
Conn. RJ-45
IP: 192.168.22.1
MAC: 00:FF:AB:9C:AF:1A
Radio antenna
“Physical Layer (1) and Data-Link Layer (2) are defining network segment as a
collection of active network devices (NIC-s, HUB-s etc), connectors, cables or radio
resources attached together by means of some standard. Segments are not routable
but often they can be extended by signal amplifiers (HUBS, Media Converters,
Switches etc.). Remember that routers (gateways) can transport data with Network
Layer protocols from one network to other, but real data transmission is done by
physical phenomenon as radio or light waves in different network segments. Simplest
way to understand, are these layers working, there are signal lamps on devices – you
just need to know or read manual about the indicators.”.
Then last slide can be more like follows:
Source: http://en.wikipedia.org/wiki/TCP/IP_model
So Application Layer (5-7) and Transport Layer (4) are more peer-to-peer (point-topoint) oriented, but Network Layer (3) and Physical Layer (1-2) are more network
topology oriented.
Kas ka näide panna HTTP päringu osas (samuti ruutingu juures).
Application A
- HTTP protocol
- TCP connection establishment
- IP packet (1)
- Ethernet frame (1)
- router
4. More reading:
-
http://www.arvutiweb.ee/index.php?option=com_content&task=view&id=108&Itemid=42
http://www.lr.ttu.ee/side/2005sygis/ Loeng9.pdf , Loeng11.pdf and others.
o Quiz (best is 1…x right answers of 3…6 choices, may be different quizzes –
for self-learning and grading)
1. Network layer protocol is
a. routing network packets (x)
b. routing transmission frames
c. addressing applications
2. These are network layer protocols:
a. TCP
b. IP (x)
c. IPX (x)
d. SPX
e. Ethernet
f. Fibre
g. VPN
3. ISO OSI Reference Model defines
a. 4 layers
b. 5 layers
c. 6 layers
d. 7 layers (x)
4. TCP/IP reference model defines
a. 4 layers (x)
b. 5 layers (x)
c. 6 layers
d. 7 layers
5. Put the layers in right order:
a. Transport (4)
b. Network (3)
c. Session (5)
d. Physical (1)
e. Application (7)
f. Presentation (6)
g. Data Link (2)
6. Transport layer is:
a. searching the right way thorough different network segments
b. transporting data from one host/application to other (x)
c. transmitting data fragments from one active unit to another
7. connect concepts to layers
a. NIC
Transport (b)
b. TCP
Network (c)
c. 192.168.0.53
Data-Link (d)
d. MAC
Physical (a)
e. e-mail
Application (e)
8. Ethernet Hub is operating in layer of
a. Transport
b. Network
c. Application
d. Physical (x)
9. Are next sentences right:
a. WAN-s and LAN-s are using both ISO-OSI reference model layers (x)
b. There can be different Networks in the same Network segment (x)
c. Application layer networking can happen although Network layer is
not configured
10. WAN-s and LAN-s are different in layers
a. Transport
b. Network
c. Data Link (x)
d. Physical (x)