More on TCP/IP (Powerpoint)

puffyyaphankyonkersNetworking and Communications

Oct 26, 2013 (4 years and 12 days ago)

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More on TCP/IP

and

Networking

CS
-
328

Dick Steflik

Open Systems Interconnection Model


7 Layer model


7 Application


6 Presentation


5 Session


4 Transport


3 Network


2 Data Link


1 Physical Hardware Connection

X.25 and the ISO Model


International Standard


Fully compliant with the OSI 7 layer model


X.25 is the set of protocols recommended
by Telecommunications Section of the
International Telecommunications Union
(ITU
-
TS)


Physical Layer


X.25 specifies a standard for physical
interconnection


electrical specs (voltages, current)


connectors

Data Link Layer


specifies how data travels between a host
and the packet switch it is connected to


frame
-

unit of data


specs for framing of data


what defines start of frame and end of frame


frame checksuming and acknowledgement and
receipt


HDLC
-

High level data Link Control

Network Layer


also called the network or communication
subnet layer


defines the basic Unit of Transfer


includes destination addressing and routing


assembles a packet and uses layer to
transfer it to the packet switch

Transport Layer


provides end
-
to
-
end reliability


double checks what what was done at the
lower layers

Session Layer


Remote Terminal Access


so important that it occupies its own layer

Presentation Layer


services used by applications


text compression/decompression


graphic object serialization


Application Layer


applications that use the network


e
-
mail
-

x.400


file transfer

X.25 vs TCP/IP


Main difference is approach to reliability


X.25
-

reliability is at link level and insurance is
provided at all layers


causes possible retries many times


TCP/IP
-

reliability is an end
-
to
-
end problem


done almost exclusively at Transport layer


retries only done at transport layer rather than every layer

Another Difference


X.25
-

idea of a network is a utility that
provides transport service


network vendor provides billing, handling
routing problems, flow control


network is complex with simple hosts at the end
points

Another Difference (more)


TCP/IP


hosts actively participate in reliability,
routing and network control (ICMP)


the network is a simple packet delivery
system with complex hosts at end points