Mobile IP

Before Mobile IP 
Mobile Computing means or refers to a system allow a computer to move from one location to another
IP addressing scheme which was designed and optimized to stationary host ,so it is difficult for mobility
A prefix of each host identifies the network and the routers use this prefix to direct datagram to correct delivery.So moving from a host require to change two thing
Host address must change
Datagram forwarding must change

Two condition used to acquire dynamic address

• First

When it boots it uses DHCP to get IPV4

• Second

Operating system detect the loss and reconnect the another network

Problem is all transporting layer connection stop to work when it detect loss the connection
(ie the disadvantage of mobile computing  is breaking transport layer connection)

If a host offer to run network services (run server) are assigned with domain name  , so when it change location DNS must be updated, but an arbitary computer is not allowed to update DNS entry

Mobility via changes in datagram
In theory we can retain the IP address of host when a host changes it s location , but to do that we need change change forwarding tables in routers through out network
In practical it is not possible because because routing protocol work only for exchange routing information about stationary network
and routing protocol designed to network rather than each host in the network, if we are using Host specific then routing traffic will be overwhelming

After Mobile IP

MOBILE IP

The IETF devised a technology MOBILE IP
By using this technology we can retain our IP address when we change our location.
Advantage
It allows host to not change its IP address and not requiring host specific routing
Disadvantage
Datagram forwarding can be inefficient .

Mobile IP working
Mobile host assumed to have a permanent home in the Internet.And its primary address is assigned to Home address The host contain a special network system Home agent, Home agent agree to intercept each datagram that arrives for the host permanent address and forward datagram to current location(foreign network/secondary address)

Q.h.Describe the various steps involved in optimization of mobile ip.(5marks)[B. Tech. Degree VII Semester Examination November 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)]

DVMRP ,NAT,DHCP

DVMRP Distance Vector Multicast Routing Protocol

One of the First multicast routing protocol
It allows multicast routers to pass group membership and routing information among themselves
Its like RIP with extended for multicast
Protocol passes information about current multicast group membership and the cost to transfer datagram between them

NAT Network Address Translation

When an incoming datagram arrives from the internet ,NAT looks up the datagram's destination address in the translation table extracts the corresponding address of an internal host, replaces the datagram's destination address with the host 's address and forward the datagram across the local network to the host

122.232.56.69 →incoming from internet to →local network host 192.168.1.25


DHCP dynamic Host Configuration Protocol

• step 1

DHCP DISCOVER
Client send a discovery message to DHCP server with destination address 255.255.255.255

• Stept 2

 DHCP OFFER
Server acknowledge with  DHCP OFFER message with client MAC address+new IP address+subnet address+lease duration. two or more DHCP server can offer the DHCP OFFER message

• Step 3

DHCP REQUEST
Client the send A DHCP REQUEST To selected DHCP server for requesting offered IP address

• Step 4

DHCP ACKNOWLEDGEMENT
Server now assign the IP for the client and send DHCP ACKNOWLEDGE signal to client to use that IP


NAT and PAT Demonstration

Q.I.d.Illustrate the six main states of a DHCP client and transitions among them.[B. Tech. Degree VII Semester Examination November 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)]

MAIN PROBLEMS OF SIGNAL PROPAGATION

Main Problems OF Signal Propagation are:

• Attenuation,
• Scattering, 
• Diffraction, 
• Reflection,
• Refraction.

 Except for attenuation all other effects can divert the waves from a straight line.

Attenuation
Extreme form of attenuation blocking or shadowing of building blocks
Reflection
If object (like mountain buildings) are larger compared with wave length of signal then signal will reflected .the more often it si reflected or bounced signal become more weak
Scattering
if object is in order or less compared with wave length of signal then wave can scatter
Diffraction
A signal can be form several smaller signal when it hit on edge of object which will propagate different direction and so it become weakerRefraction.
when it travel from one media to another refraction take place

Compare the features of SDMA, FDMA and CDMA

Approach	SDMA	TDMA	FDMA	CDMA
Idea	Segment spaced into cells(Tower) or sectors.	Segments sending time into disjoint time slots demand driven or fixed patterns.	Segment the frequency band into disjoint subbands	Spread the spectrum using orthogonal codes.
Terminals	Only one terminal can be active in one cell or one sector.	All terminals are active for short periods of time on same frequency.	Every terminal has its own frequency uninterrupted	All terminals can be active at the same place at the same moment uninterrupted.
Signal separation	Cell structure, directed antennas	Synchronization in time domain	Filtering in the frequency domain.	Code plus special receivers.
Transmission scheme	Continuous	Discontinuous	Continuous	Continuous
Cell capacity	Depends on cell area	Limited	Limited	No absolute limit on channel capacity but it is an interference limited system
Advantages	Very simple, increases capacity per	Established fully digital, flexible	Simple, established, robust	Flexible, less frequency planning needed, soft handover
Disadvantages	Inflexible, antennas typically fixed	Guard space needed (multipath propagation), synchronization difficult	Inflexible, frequencies are scarce resource	Complex receivers, needs more complicated power control for senders
Comment	Only in combination with TDMA, FDMA or CDMA useful	Standards in fixed networks, together with FDMA or SDMA used in many mobile networks	Typically combined with TDMA and SDMA	Still faces some problems, higher complexity, lowered expectations, will be integrated with TDMA or FDMA

Q.Compare the features of SDMA, FDMA and CDMA (15mark)[B. Tech Degree VII Semester Special Supplementary Examination June 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)] 

ICMP Internet Control Message Protocol

ICMP allows routers to send error or control messages back to source of a datagram that caused a problem
ICMP messages are not usually delivered to application

• ICMP can be think like  as providing communication between an ICMP module on one machine and ICMP module in another

ICMP is used to allow routers to report error or provide information about unexpected circumstances

ERROR reporting and ERROR correction

• ICMP does not interact with the host
• ICMP does not attempt to correct the error

ICMP provide a way for routers that encounter an error to report the error to the original source

• Routers are stateless as possible
• The idea of error reporting rather than error correcting help to improve security
• If an attacker send frequently incorrect message and the router tries to correct the problem it will not respond slowly ,So error correction is not done by router
• If the router detect a problem the IP cannot know the set of intermediate machine that processed the datagram .So it cannot inform them of the problem instead of silently discarding the datagram,the router use ICMP to inform the original source

ICMP message format

All ICMP message begin with same three field

1. TYPE :- identify specific ICMP message to purse remainder of message
2. CODE :- Information about ICMP ...eg :- TIME EXCEEDED message can have a code value(to indicate the hop count (TTC) of datagram reached zero)
3. CHECKSUM :-

MESSAGE BODY :- depend entirely on message type

Testing reachability and status

Ping send an ICMP echo request message to remote computer
ping program receives ICMP Echo reply from the remote Computer
ECHO Request and Reply message format of ICMP

TYPE - request-IPV4→8-IPV6→128
TYPE - reply-   IPV4→0-IPV6→129
CODE-0
An Echo reply contain sequence data on Echo request arbitrary data can also sent

Queuing Shaping and Policing

Queuing Shaping and Policing

Queing 

If a sequential server is busy processing a request when a subsequent request carries the server cannot place incoming request in queue multiple request can arrives in a rapid successive to hand burst typical queue size are extremely small

Shaping
To consist queuing and forwarding a router that offer QOS usually implements a mechanism to handle packet burst ,Here each burst is smoothed . To smooth burst a router temporary queues incoming datagram then sends to them steady rate

Scheduling
A router needs to assign prior to out going traffic and choose which packet to send a given time

Four factor affecting scheduling

1. Fairness :- bandwidth fall under assigned to flow
2. Delay :- Packet should not delay excessively
3. Adaptability :- If a given flow does not have packet to send scheduler should divide extra bandwidth 
4. Computational overhead :- Scheduler must not in care much computational overhead

Policing
Policing Mechanism protect other flows to insure that each flows receives its fair share

Q.IV. (b) What is meant by the terms 'shaping' and 'policing'? (7)[B. Tech Degree VII Semester Special Supplementary Examination June 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)] 

BGP Border Gateway Protocol-- Extra hop problem

Extra hop problem

 case 1

case 2


case 2 get extra unnecessary routes  it goes through back bone network twice to reach the host

Autonomous System (AS)
A group of networks and routers controlled by a single administrative authority is called autonomous system
This allows them to choose its own mechanism for

• Discovering 
• Propagating 
• Validating
• and Checking the consistency of routes

Autonomous system can can be large enterprise ,corporation or university

in short we can give definition like any group that run a large network is AS

The boundaries between autonomous must be defined precisely to allow automated algorithm to make routing decisions and to prevent the routing update protocols used in one AS from accidentally reach a at which it can no longer controlled into another

• AS avoid routing path between competitors AS even such path exists.
• AS is assigned with an AS number by central authority
• Each AS can define a set of policies
• This is helpful for automated routing algorithm to distinguish between AS

When routers in two AS exchange information the protocol arrange them to learn other AS number

Exterior Gateway Protocol (EGP) and reachability (BGP)
 AS system configures one or more of its routers to communicate with other AS.
information flows in two directions
Routers must collect information about network insides routes and pass to out
Routers must accept the information about networks in other AS and spread to its inside AS

EGP
Exterior Gateway protocol
AS advertise its reachability to the outside AS
A single EGP used to advertise reachability or exchange routing information in the internet is BGPBorder gateway protocol

When Two AS agree exchange information between them each must designate a router that will speak BGP on its behalf.

A router speaking BGP must communicate with a peer in another AS
so it will be the  border router communicating with outside hence border gateway or  border router

Router R1 collect information from AS 1 and use the BGP to report to R2
same way R2 also collects information from AS 2 and use BGP to report to R1

BGP CharacteristicsBGP is an Unusual protocol in many waysIts neither a distance vector algorithm nor a link state algorithm instead it is using path vector alogorithm

BGP is characterized by following

• Inter Autonomous System Communication :- BGP advertise reachability information , so its primary role is  allow communication among AS.
• Coordination among multiple BGP speakers: - if an AS contain multiple routers,each communicating with a peer in an outside AS , and coordination among them is done with iBGP a form of router for guaranteed propagation with consistent information
• Propagation of reachability information :- BGP allow an AS to to advertise destination that are reachable either through or in it . also learn such information from another AS
• Next Hop Paradigm :- It provide next hop information for each destination like distance vector protocol
• Policy Support :-BGP can implements routes that the local administrator choose,Routers running BGP can be configured to distinguish between the set of destination reachable inside the AS and set of destination advertised to other AS
• Reliable transport :- BGP is unusual among protocol that pass routing information because it assume reliable transport (TCP for all communication)
• Path information :- Instead of specifying destination that can be reached and a next hop for each,  BGP uses path paradigm in which advertisement specify path information that allow a receiver to learn a series of AS  along path to destination.
• Incremental Updates :- to conserve network bandwidth BGP does not pass full information in each  update message ,Instead full information exchanged once and successive message carry incremental updates  called deltas.
• Support IPV4, IPV6 BGP send a prefix length along with each message (prefix→large blocks of subnets )
• Route aggregation :- BGP allow conserve bandwidth by allowing a sender to aggregate routing information and send a single entry to represent multiple related network
• Authentication :- BGP allows receiver to authenticate the messages
• BGP can handle big routing tables: In which IGP cannot handle big routing table currently global internet contain 500000 routes 

BGP functionality and types

BGP peer perform 3 functions :-

1. Initial peer acquisition and authentication :- the two peer establish a TCP connection and then perform message exchange this will guarantee both side to agree to communicate  
2. Primary focus on the protocol :- each can send +ve or -ve reachability information ,ie sender can declare that one or more destination are reachable by giving next hop to each or previously advertised destination is no longer reachable.
3. On going Verification :- that the peer and the network connection between them are functioning correctly

BGP message types

1. OPEN :  initialize communication
2. UPDATE :- advertise or with draw routes
3. NOTIFICATION : Response to incorrect messages
4. KEEPALIVE :- Actively test peer connection
5. REFRESH : Request re advertisement from peer 

BGP OPEN message

After OPEN message is sent receiver should reply with KEEPALIVE knowledge message before they can exchange router information

BGP UPDATE message

After KEEPALIVE message the peer use UPDATE message to advertise new destination that are reachable or withdrawn previous advertised destination that are unreachable  

Path Attributes
A sender can use the path attributes to specify a next hop for the advertised destination ,a list of AS along the to the destination and whether the path information was learned from another AS or derived from within the sender AS 

Path Attributes are important in BGP message for 3 reason

• Reason 1

Path information allows receiver to check for forwarding loops
The sender allows the exact path of AS that will be used to to reach the destination
If the receiver AS appears on the list ,Advertise must be rejected

• Reason 2

Path information allow receiver to implement policy constraints
eg ;- reject the path that includes competitors AS

• Reason 3

Path information allows a sender to specify the information whether it come from inside or outside the AS.It can helps the receiver to know source of all routes. So that it can reject or Accept the routes
Path Attributes field
ID of origin path information
List of AS on path to destination
Next Hop to use for destination
Descriminator used for multiple AS exist point
Preference used within an AS
Indication that have be aggregated routes
ID of AS that aggregated routes ID of community for advertised destination

BGP KEEPALIVE message
BGP peer periodically exchange KEEPALIVE message to test the network reachability and verify both peer continue to function
Two reason for BGP uses KEEPALIVE message
Because BGP use TCP for transport ,TCP does not test reachability of destination or do not report for send data fails
Re sending the same ,message is wasting of network bandwidth ,because routing information is often large ,KEEPALIVE is small message to ensure the connectivity
BGP REFRESH message
BGP NOTIFICATION message

BGP used notification message for control or when an error occur , ,BGP send notification message and then closes TCP connection

ERROR code messages

• 1→ERROR in message header
• 2→Error in Open message
• 3→ERROR in Update message
• 4→Hold time expired
• 5→Finite state machine error
• 6→Lease ,termination connection

Q.IV.Explain the exterior gateway protocol BGP along with its four basic message types. (15marks)[B. Tech. Degree VII Semester Examination November 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)]

RIP PROTOCOL

RIP PROTOCOL
In the smallest intranet manager can establish and modify routes manually.
The manager keep a list of  networks and updates the forwarding tables when ever a new network is added to deleted from the network
RIP protocol remained in widespread use in early in the internet
Originally RIP was known by the software which implements it,routed.

RIP operation
The underlying RIP protocol is a straight forward implementation of distance vector routing for local networks.
RIP support two type of participants

1. ACTIVE :-Active partipants advertise thier routes to others
2. PASSIVE :- Passive participants listen to to RIP messages and updates their forwarding tables

A router running RIP active mode broadcast  a updating  messages every 30 seconds

Update message
It contain  a set of pairs, each pair contain (IP network,integer distance to that network).
The update contains information taken from its forwarding infomation tables (FIB)

Hop Count metric
RIP use a hop count metric to measure distances, a router is defined to be one hop from directly connected network
one hop :- direct connection
two hop :- a network that is reachable through one another

cases
network 1→inter mediate network routes→network 5

If intermediates routes contian slower path with small hop number it is not taken
So selecting hop count minimum for shortest path routing is not produce optimal results
from above exmple although shrtest path is from through sattellite is not best to reach fastest way to to the other network

And some time two path can be exited with same hop count to the network .(1,1) means it can reach network 1 with distance 1.
(1,3) means it can reach network 1 with distance 3


In that case it take which advertise its routes first.

RIP use few rules to improve performance and reliability 

Timer reset (180seconds)
Routes become invalid after 180 seconds if routes is not advertised within that time
So if a router fail it will get invalid path through that router within 180seconds
 If a router failed and installed new router it will advertise its same routes for updating FIB and that time its timer is reset.
It uses hysteresis ,means that it will not replace routes with equal cost

Three kinds of error handled by RIP

• Algorithm does not cleaarly detect forwardind loops,so RIP must either trust or take precautionto prevent such loops
• To prevent instabilities RIP must use a low value for maximum possible distance (16),manger must divide the intranet into sections or use an alternatice protocol
• The distance vector alogorithm can create slow convergence or count o infinity in which inconsistance occur , because routing propagation occur slowly across network , choosing small infinity(16) helps to limit convergence but dot not eliminate it.

Slow Convergent Problem

Network 1 → R1→R2→R3
Network 1 X R1→R2→R3  ( network 1 failed )
Network 1 X R1⇌R2→R3  ( Here R2 is broadcasted its routing information with hop 2, this will taken by R1 router and add hop 3 and broadcast with distance 3 and this continues until the datagram's hop limit is reached )

Solution is like  good news travel quickly and bad news  travel slowly

1. Split horizon update,It does not propagate information about a router back over the same technique
2. Hold down:- wait long enough to ensure that all machine receives the bad news and not mistakenly accept a message that is out of date,Hold down set time for RIP is set to 60seconds, i.e twice as long a normal update message
3. Poison reverse :- Once a connection disappear the router advetising the connection retain the entry for several update period and include an infinit cost route in its broadcast
4. Triggered update :-Triggered update mechanism forces a router to broadcast the changes in routing information immediatly after receiving bad news

Q.I.c.Poison reverse combined with triggered updates can solve slow convergence problem created byRIP. Justify the given statement.(5 mark)[B. Tech. Degree VII Semester Examination November 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)]

The Open SPF Protocol

The Open SPF Protocol

It is a interior gateway protocol that use the link state algorithm

Open standard

• Anyone can implement without paging license fee.
  AS name implies specification is avalable in published literature

Type of Service Routing

• Manger can install multiple routes to given destination,one for each priority or type of service

Load balancing

• OSPF distributs traffic over all routes equally
• If a manger specifies multiple routes to a given destination at same cost  then also traffic distributed equally over all routes

Heirarchical subdivision into areas

• It allows large intranet or site to partition its network and routers into subset called areas and limit routing overhead
• Each area is self-contained, knowledge of an area topology remain hidden from other areas
• multiple group with in a site can cooperate even when Each group retain the ability to change its internal network topology independently.

Support for authentication

• Support variety of authentication schema and allows one area to choose a different scheme than another one

Arbitrary granularity

• OSPF includes support for host specific subnet specific network specific  and default routes

Support for Multi Access Network

• If k router present in an Ethernet they broadcast K^2 status messages , each node represent either a network or router and only  A designated gateway sends link status messages on behalf of all routers attached to the network

Multicast Delivery

• To reduce load on non participating system OSPF uses hardware multicast capabilities
• two IPV4 multicast address are pre assigned to OSPF 
• 224.0.0.5 for all routers
• 224.0.0.6 for all nodes

Virtual topology

•  A manger can create a virtual network topology, A manger can create virtul link between two roters even if physical connection between them require multiple transit networks

Route Importation

• OSPF can import and spread routing information based from external site(i.e from routes that do not use OSPF)

Direct use of IP

• OSPF message are encapsulated directly in IP datagaram

RARP (Assigning Internet address at start up)

RARP  (Assigning Internet address at start up)
RARP was once an essential protocol used to bootstrap system that did not have stable storage (i.e disk-less computer)

Operation field contain RARP req and RARP reply
Frame header contain frame type field to identify RARP type 803516

At start up
A system braodcast a RARP request to obtain IP address

• RARP+Ethernet address→request

All receives RARP request,only authorized supply RARP services process
RARP server look up ETHERNET address in its database if not contain extract the correspond IPV4 address from database ,once reply arrives the disk-less system continues to boot assigning its IPV4 address for communication
A network should contain at least one RARP server to respond

Primary and back up RARP server
Case 1

• Primary RARP server only respond no primary not respond 

Case 2

• Primary RARP server respond immediately non primary server respond delayed 

Address Resolution Problem

Two types physical address

• Ethernet:- Large,fixed physical address ,Address resolution is difficult
• proNET :-small easily configured

Resolution through direct mapping
proNET
When installing an interface board in a computer,

• proNEt use small integers for physical address
• Allow users to choose hardware address

One has the freedom to choose both IP and physical address
One can assign an IP address like 172.5.48.3 with the host id portion 3
One assign IP address with the host ID portion equal to 1,2,3 and so on
When installing network interface hardware selects a physical address that corresponds to the IP address
eg:- 192.5.48.3
The system administrator would select physical address 3 for computer with 192.5.48.3 becuase it is a class c address with the host id portion 3 ,Mapping is easy to maintain ,because it can be performed without reference to any external data.
Extracting physical address is extracting host portion of IP
A new computer can be added to the network without changing existing assignments or compiling code
resolving IP address IA  means computing
Pa =f(IA) 

Resolution through Dynamic Binding
Address Resolution is difficult for some networks like Ethernet technology
here 48 bit physical address is assigned during manufacturing the device ,when hardware fails and required to replace the Ethernet interface the machine address changes more over it is 48 bit address ,so no hope it can be enconded to 32-bit address
Designers of TCP/Ip protocol found a creative solution to Address resolution problem for network like Ethernet having broadcast capability
Solution allow new host or routers to be added to the network with out recompiling the code and does not require to maintain centralized database

Address Resolution Protocol 
Designers chose to use a low level protocol to bind address dynamically.termed ARP
this also provide both reasonably efficient and easy to maintain
Working of Dynamic ARP
When A host want to resolve IP address IB
It broadcast a special packet asking the host IB to respond with its physical address PB

All host receives the packet  including B
But only host B recognize its IP address and sends a reply that contain its physical address PB

When A receive the reply ,it uses the physical address to send the internet packet directly to B

ARP CACHE
ARP cache time out
To reduce communication cost,computer use ARP maintain a cache of recently required IP to physical address binding
When transmitting packet it looks in its cache for binding, before sending ARP request

SOFT STATE
A technique used in network protocol ,information can be fried out without warning,because ETHERNET does not have a guaranteed delivery ,it normally set to 20 minutes expiry time
ARP with other protocol
ARP as part of the physical system and not as part of the internet protocol

ARP IMPLEMENTATION

ARP is divided into two
first part

• maps IP to physical address

Second part

• Answer request from other machine

Steps

• 1.check if IP and physical adress are in its cache
• 2.if not send ARP request (set n timer)
• 3.reply may delyed
• 4.reply may destroy
• 5.target host may crashes
• 6.send same packet after time expires if reply is not arrived
• 7.extract IP and physical address from both request and reply
• 8.Check the request containing target host if then prepare a reply

ARP encapsulation and identification

Frame header contain a field to identify ARP message type
Frame data contain ARP message which contain ARP request or ARp reply ,physical address IP etc

ARP PROTOCOL FORMAT

ARP messages does not have a fixed format header .
The design allow ARP to map arbitrary high level protocol address to an arbitrary network address.
In practice ARP is only used to map 32 bit IPV4 address to 48 bit ETHERNET address

• Operation type field contain:- ARP req ARP reply RARP req RARP reply
• Hardware type filed:- I for ethernet
• Protocol address field:- 080016 for IP address ,type of higher level protocol address
• HLEN and PLEN allow ARP to be used arbitrary networks

when making a request it swap the sender and target ( IP , hardware )pair and operation field to reply

Q.II.Summarize the address resolution through dynamic binding using ARP. Outline the
steps involved in an ARP process.(15 marks)[B. Tech. Degree VII Semester Examination November 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)]

Internet Multicast

Internet Multicast 

Broadcast address ( all 1's  )reserved for sending to all station simultaneusly

Multicast

• A limited form of broadcast
• A subset of the computer on a network agree to listen to given multicast address
• The set of participating computer is called multicast group
• A computer should instruct its host interface to accept froup's multicast address for joining a multicast group

IP MULTICAST
Internet abstraction of hardware multicasting
General characteristics:-

Group address
Each multicast group is unique class D address

• →A few IP multicast address are permenently assigned by internet authority
• →Other addresses are temporary and are available for private use

Number of groups
IP provides address for upto 2^28 simultaneous multicast groups

Dynamic Group membership
A host can join or leave an IP multicast group

Use of hardware
If hardware does not support multicast .IP uses broadcast or unicast to deliver IP multicast

Inter-network forwarding
Membership of an IP multicast group can attach to multiple physical network ,special multicast routers are required to forward IP multicast

Delivery semantics
Multicast datagram can be lost ,delayed ,duplicated or delivered out of order

Membership transmission
Group membership is only used to determine whether the host receives datagram sent to the group

IP MULTICAST ADDRESS

IP multicast addresses are divided into two types

• Those are permanently assigned
• Those are temporary use

Permenent Address
Permanent address are called well known
They used for major service on the global Internet also as well as used for infrastructure maintenance

Temporary address
It correspond to transient multicast group
They are created when needed ,discarded when the count of group member reaches zero
IP reserve class D address for multicast

GSM ( GLOBAL SYSTEM FOR MOBILE )

GSM  ( GLOBAL SYSTEM FOR MOBILE )

It is a second generation cellular standard ( most famous working standard mobile phase )
It is developed to cater voice and data delivery
It is using digital modulation
The utility of gsm provides national and international roaming very simple and easy between mobile phone generator

GSM SERVICES 

• TELE SERVICE:-includes mobile phone ,emergency calling
• DATA SERVICE:-includes sms ,fax,electronic mail,voice mails
• SUPPLYMENTARY SERVICES:-incoming ,outgoing calls, call waiting ,call forwarding,call holding,conference etc

GSM ARCHITECTURE

• Network Sub system
• Radio sub system
• Operation maintenance sub system

NETWORK SUB SYSTEM
Network sub system perform :call processing , subscriber related function
It includes;-

1. MSC-mobile switching center
2. HLR-Home location register
3. VLR-Visitor location Register
4. AUC-Authentication center
5. EIR-Equipment identity register
6. GMSC-Gateway MSC

MSC:-Mobile switching center

function carried out these are listed

• Call processing :-includes control of data/voice call setup
• Operation and Maintenance Support :- data base management,traffic metering and measurement
• Internet Work:- Manges the interface b/w the GS network and PSTN
• When the MSC provides the interface with other network in the GSM network it is known as Gateway MSC

HLR
:-Home Location Register sub system reference database for subscriber parameter

• Mobile Subcriber roaming number
• Subscriber ID (IMSC & MSISDN )
• Current location of subscriber
• Subscriber status ( registered or unregistered)
• Automating Key and AUC functionality

VISITORS LOCATION REGISTER

• It provides local database for the subscribers where ever they are in physically located within PLMN
• It is local database and contains copy of most of the data stored in HLR
• It contain Mobile Status :- busy status,no answer
• Location area identifies LAI ,MSRNand TMSI

AUR

Authentication center subsystem

• It provides authentication and encryption parameter for the verification  of subscriber identity
• It ensure confidentiality of each cell
• It protect network operator from frauds found in today's cellular world

EIR
Equipment identity register sub system
It contain centralized database for validating international mobile equipment identity IMEI

RADIO SUB SYSTEM
Management of radio network and is controlled by msc
it consists of

• BSC: Base station controller
• BTS: Base transceiver station

BSC

• Base station controller sub system
• It is connected to MSC
• Controls one or more BTS
• Switches traffic and signalling b/w BTS and MSC

BTS
Base transceiver station sub system

• The BTS is networking component s of a mobile communication  system from which all signals are sent and received.
• A BTS is controlled by MSC
• A BTS is also called a base station(BS) and is commonly refered as a cell phone tower

OPERATION AND MAINTENANCE SUBSYSTEM

• Dynamic monitoring and controlling of network operation and maintenance data function
• Configuration management
• Fault report and alarm handling
• Performance supervision
• Storage of software and data
• Store data for minimum one year

Q.Explain the architecture of GSM in detail. (15mark)[B. Tech Degree VII Semester Special Supplementary Examination June 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)]

Classful Internet address

Classful Internet address

IP address is 32 bit( dotted decimal notation for IP address)
IP address is a hierarchical address IP address is location based .
The designers are free to choose packet format and sizes addresses delivery techniques and so on..
Nothing is dictated by the hardware.

For  addresses the designers  of TCP IP chose scheme analogous to Physical network addressing in which each Host on the internet is assigned 32 bit integer address called  its internet address or IP address
Integer are chosed carefully to make routing efficient.
IP address encodes the identification of the network to which a host attaches as well as identification of a unique host. EA is a pair ,net IDand  host ID .net ID identifies  the network and host ID identifies a host on that network each address is a pair (net ID ,host ID)
Net ID identifies a network
host ID identifies a host on that network
The partition into prefix and suffix is not uniform throughout the entire internet because the designer  did not specify a single boundary

In the original addressing scheme which is known as class full each  IP address had  one of the first three form.

In the classful addressing scheme each address is said to be self identify because the boundary between prefix and suffix can be computed from the address alone without reference to external information
Subnet and supernet (classless addresses )extensions
A unique prefix for each physical network would exhaust the address space quickly consequently an Addressing  extension was developed to conserve network prefix known as subnet addressing scheme allows multiple physical networks to share a prefix.

A second extension was devised that ignored the classful heirarchy and allowed the division b/w perfix and suffix to occur at arbitary point called classles addressing or supernetting .
The scheme allows more complete utilization of the address space

Q.I.a.What is meant by subnet addressing?(5 mark)[B. Tech Degree VII Semester Special Supplementary Examination June 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)]
Q.I.b.With the help of a neat diagram show the original classful IP addressing scheme.(5 mark)[B. Tech. Degree VII Semester Examination November 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)]

VLAN

VLAN
A set  of ports on an ethernet switch that are configured by the network manager to be part of a single broadcast domain.
 Vlan allows a manager to configure the switch to operate like Several smaller switches.

A manager can use virtual LAN to separate computer according to policies

A manager can create one or more virtual LAN by specifying which computer attached to which virtual LAN
EG:

• VLAN  for employees
• VLAN  for visitors

Each virtual LAN define a broadcast domain which means that when a computer send a broadcast packet ,the packet only delivered to the set of computer in the same VirtualLAN .

Virtual LAN is treated exactly like a separate physical network.
Virtual LAN technology emulate a set of independent physical network
A computer in a given virtual LAN share broadcast and multicast access on a given virtualLAN  and does not spread to other virtualLAN ,just like a separate physical network broadcast and multicast send


Q.III.a.Write short notes on VLAN. (8marks)[B. Tech. Degree VII Semester Examination November 2012 CS/IT 703 ADVANCED COMPUTER NETWORKS (2006 Scheme)]

Extending an ethernet with bridges

Extending an ethernet with bridges
Adaptive bridge

• Connecting 2 Ethernet with bridges in superoir to connecting them in repeater a hub because bridges operate on packet rather than electrical signal
• bridges
• do not replicate noise
• do not replicate error
• donot replicate malformed frames
• validates the frame before transmitting to other the other network
• hides the details of interconnections : set of bridges segmentsact as like a single ethernet
• and Ethernet follow CSMNCD rules
• make intelligent decisions about frame to forward

Collision and propagation delays on one segment remain isolated from those on the other

Bridges network are  classified as transparent

Adaptive bridge/learning bridge
Bridges makes intelligent decision about frame to forward
An adaptive bridge consist of a computer with two Ethernet interfaces software in adaptive bridge keep two address stack

when a frame srrives from ethernet \(E_1\), the adaptive bridge add a 48 bit Ethernet source address to list associated with \(E_1\)
similiarly
when a frame arrive from \(E_2 \) to bridge adds the source address to list associated with \(E_2\)
Thus adaptive bridge will learn which machine lie on \(E_1\) and which lie on \(E_2\)

In bridge packet forwarding is used by softwares
bridge work only for half duplex mode
Switch
In this packet forwarding using by ASIC(Application Specified Integrated Circuits)
Operates in comparatively higher speed than bridge
superior than bridge
Method of switching in switching is store and forward ,cut through switching or fragment free
Normally switches has more ports than a bridge
Switches operates in half duplex mode or full duplex mode