GSM TOWARDS LTE NETWORKS

bottlelewdMobile - Wireless

Dec 12, 2013 (3 years and 8 months ago)

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GSM TOWARDS LTE
NETWORKS

Lecture # 3

WIRELESS ACCESS EVOLUTION



New Services


Efficiency


More Data
Services
required

Broadband

Subscribers

Voice


Coverage


Mobility


Voice Quality


Portability


Capacity


Data Service


Broadband


Network
Simplification


Cost of
Ownership

IP Introduction


Overview

Agenda


IP Networks. General Concepts


IP Addressing


Subnetting


Data Link Layer


Network Layer


Transport Layer


IP Networks. General concepts


Why a standard?


First networking technologies created in 60 & 70’s


Based on propietary protocols, different physical connections


No communication between different machines


US Department of Defense created TCP/IP (1972)


Communication standard based on layers (software) and modules
(hardware)


Network Access Layer


Internet Layer (IP)


Host
-
to
-
host layer (TCP, UDP)


Application layer (FTP, Telnet)



IP Networks. General concepts


OSI model (1978)


Based on 7 layers







IP Networks. General concepts


OSI model.
Advantages


Easy to learn


Easy to develop


Multivendor
interoperability


Modular engineering






IP Network. General Concepts

IP Networks. General Concepts



Most interesting (M
-
PBN point of view)


Layer 2


Layer 3


OSI summary


Each layer provides a service to the layer above it in
the protocol specification


Each layer communicates with the same layer’s
software or hardware on the other computers


To accomplish these task, the data is encapsulated
progressively with new headers when sending the data
and is de
-
encapsulated when receiving the data

IP Addressing


An IP (Internet protocol) address is an unique identifier
for a node or host connection on an IP network.


An IP address is a 32 bit binary number usually
represented as 4 decimal values, each representing 8
bits, in the range 0 to 255.


Every IP address consists of two parts, one identifying
the network and one identifying the node.


The Class of the address and the subnet mask
determine which part belongs to the network address
and which part belongs to the node address.

IP Addressing > Classes

IP Addressing > Classes

IP Addressing > Host Configuration

IP Addressing > Host Configuration

Subnetting


What is a subnet?


Logical organization of network addresses ranges
used to separate hosts and network devices


Similar to rooms, floors, building and cities


Subnets are created based on


The number of hosts that needs to exist now and in
the future


The necessary security controls between networks


The performance required for communication
between hosts

Subnetting


What is subnetting?


Subnetting is the process of breaking down an IP Network into
smaller sub
-
networks called subnet



When is subnetting used?


Mainly to separate traffic by function


To apply security measurements


A subnet is defined by


IP address (A.B.C.D)


Subnet mask (A’.B’.C’.D’ or /X)


10.0.0.0/24



10.0.0.0

255.255.255.0

192.168.2.0/26



192.168.2.0

255.255.255.192




Subnetting



How to calculate the equivalence between netmasks?


Manual method: decimal


binary


bit
-
wise AND
operation


binary


decimal








Subnet mask blocks out a portion of the IP address to
distinguish the network ID from the host ID.



Subnet mask determines if the host is in a local or a
remote network





Subnetting

Subnetting > IPv6

Subnetting > IPv6

Layer 2 / Layer 3



Two important rules



If the hosts belong to the same subnet


NO
ROUTING NEEDED (will send ARP request to
retrieve the MAC)


Layer 2



If the hosts belong to different subnet


ROUTING NEEDED (will send the packet to the
default gateway)


Layer 3


ARP


Address Resolution Protocol


ARP maps physical addresses and IP addresses


The physical address is necessary to make up
the packet to be sent


The sender needs the MAC address of the
receiver

ARP

ARP


Once the MAC address is obtained, the L2 packet is made up






ARP tables permit to reduce the number of request


Host



Hardware address

TTL

192.168.0.1


00:30:88:10:b0:dd

2500

192.168.10.2


00:30:88:10:b0:df

253

Layer 3. Indroduction


There are two types of Layer 3 Protocols:


Routed Protocol: It is responsible for the actual transfer of traffic
between devices running L3 protocol. Most widely know protocol is
IP. There are more: IPX (Novell), AppleTalk DDP.


Routing Protocol: It is a protocol that specifies how routers
communicate with each other.


Role: end
-
to
-
end delivery of packets. To accomplish this task, the
network layer defines logical addressing so that any endpoint can be
identified.


It also defines
how routing works

and how routes are learned so that
the packet can be delivered


Routing = building maps and giving directions.


Forwarding = moving packets between interfaces according to the
“directions”








Protocols Classification


Where the protocol is used


Interior Protocols (IGP)


Exterior Protocols (EGP)


Kind of information that is carried and the
way the routing table is calculated


Distance
-
vector Protocols


Link
-
state Protocols

IGP Vs EGP


Interior Gateway Protocol


A single autonomous system


Single network administration


Unique routing policy


Make best use of network resources


Exterior Gateway Protocol


Different autonomous systems


Intependent administrative entities


Communication between independent network
infrastructures

Distance
-
vector Vs Link
-
state


Distance
-
vector Protocols


Each router periodically sends to his neighbors


how far is the destination


the next hop to get there


Install routes directly in tables


Link
-
state Protocols


Each router sends information about


links to which it is attached


state of these links


It is flooded throughout the network


Every router calculates its routing

table


Routing Example

Introduction to TCP


TCP has the following characteristics:


Connection
-
oriented


Session is established before exchanging data.


Full
-
duplex


Reliable


It uses sequence numbers.


It uses acknowledgements.


Byte
-
stream communications


Sender
-
side and receiver
-
side flow control


Segmentation of application
-
layer data


One
-
to
-
one delivery




TCP Three
-
Way Handshake

TCP Normal End of the Session