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Prof. E.Borcoci- UPB -2011-2012 2

Retele si Servicii

Sem II licenta spec. RST

(English version)

Network and Services

E. Borcoci, UPB

2011-2012

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CONTENTS

1 INTRODUCTION-ARCHITECTURE REVISION 5

1.1 NETWORKS LAYERED ARCHITECTURES 51.1.1 General Principles and Functional Layers 51.1.2 OSI Reference Model 61.1.3 Real Stack Examples. Incomplete stacks 9

1.1.3.1 TCP/IP Stack 91.1.3.2 IEEE 802.x standards for LAN, MAN 131.1.3.3 Signalling System No.7 131.1.3.4 MPLS architecture 14

1.1.3.4.1 MPLS IP stack 141.2 MULTIPLE PLANES ARCHITECTURES 15

1.2.1 Principles 151.2.2 Signalling Issues 161.2.3 Next Generation Networks Architecture- high level view 17

1.3 BUSINESS MODELS FOR (MULTIMEDIA)COMMUNICATION ARCHITECTURES 201.3.1.1 Customers and Users 201.3.1.2 Providers (PR) 20

1.3.2 Service Level Agreements/Specifications (SLA/SLS) 221.4 EXAMPLES OF MULTIPLE PLANE ARCHITECTURES 241.4.1 IEEE 802.16 multi-plane stack 241.4.2 Generic Example of a multi-plane architecture 261.4.3 Architectural stack for wireless heterogeneous mesh network 261.4.4 Control Plane in GSM (2G) 28

2 INTERCONNECTION- REVISION 29

2.1 MODURI DE LUCRU CU IFR CONEXIUNE CO/CL 292.2 CERINELE UNUI SERVICIU DE INTERCONECTARE (LA NIVEL TREI) 302.3 MODUL DE LUCRU CO( CONEXIUNE LA NIVEL REEA) 312.4 MODUL DE LUCRU CL (FARA CONEXIUNE LA NIVEL REEA) 312.5 INTERCONECTAREA DE TIP PUNTE (BRIDGE APPROACH) 31

2.6 EXEMPLE DE INTERCONECTRI 322.6.1 Interconectarea de reele LAN prin puni (B) 342.6.1.1 Puni transparente (Transparent Bridges- TB) 362.6.1.2 Punti cu rutare de tip sursa 36

3 ROUTING ALGORITHMS AND PROTOCOLS 36

3.1 GENERALITATI 363.2 ALGORITMI DE CAUTARE A CELUI MAI SCURT DRUM 40

3.2.1 Algoritmul Dijkstra (centralizat) 413.2.2 Algoritmul Ford (Fulkerson) 43

3.3 IPROUTING PROTOCOLS 473.3.1 Internet Protocol reminder 473.3.2 Principles of IP routing 49

3.3.3 Network hierarchies 503.3.4 Address Resolution Protocol (ARP), Reverse ARPRARP 533.3.5 Interior Gateway Protocols 55

3.3.5.1 Routing Internet Protocol (RIP) 553.3.5.2 Ad hoc On-Demand Distance Vector (AODV) 58

3.3.5.2.1 Open Shortest Path First (OSPF) 633.3.6 Border Gateway Protocol (BGP) 68

3.4 IPV6 703.5 ICMPV6 73

4 SERVICES 73

4.1 REFERENCES 744.2

GENERAL LIST OF ACRONYMS 74

5 ANNEX 1 81

5.1 ETHERNET FRAME FORMATS: 81

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1 INTRODUCTION-ARCHITECTURE REVISION

1.1 Networks Layered Architectures

1.1.1 General Principles and Functional LayersArchitectural Model : set of functions and relations between them, independent of

implementation

Objective:

management of high complexity: (divide et impera) - principle

interoperability among different products

Tools: definition of functional layers + interfaces

Network element: terminal, switching node, multiplexer, router, etc. = hierarchical set of

levels

-tasks:

- information transport (lower layers)

- high level processing of information (upper layers)

Ta Tb

Processing

functions

Network

functions

Appl.

processes

Processing

functions

Network

functions

Appl.

processes

C1

C2

N2

N1

Ta Tb

Network(s)

User

Protocols

Physical medium

Upper layers

protocols

Complexity/

Intelligence Future Internet?

(more intelligent networks)

E.g. Content aware networks

a b

Figure 1-1 Simplified architectural model for communication

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a. Network and terminals b.Two level model : Ta, Tb = terminals

-application processes ( usually resident in Ta, Tb - they communicate through a set of rules

(protocol) at user level:

Protocols at different levels between:

- application processes

- higher layers processing functions (higher layers)

- network transport functions (lower layers)

- set of layers = protocol stack

Layering principle is extended inside each of the two layer

1.1.2 OSI Reference Model

Classical architectural mode (1970-80)

ISO (International Standardization Organization): OSI - RM ("Open System Interconnection -Reference Model")for layered architecture networks

OSI RM defines: architectural and functional principles for open systems able to beinterconnected no matter the equipment manufacturer

- real world stack can be different of OSI-RM, but the same principles are applied

- OSI, TCP/IP modelone plane architectural model

Usage examples of layered architecture networks use:

- industry, administration, business, health, military, education, research, etc.

- data and multimedia networks: local (LAN), metropolitan (MAN) wide area WAN (typical

example: INTERNET, Intranets, Extranets)

-digital telecommunication wide area networks:

- fixed communications: ISDN, BISDN, GSM ( e.g.Signalling System No.7 SS7used to control the digital telecom networks)

- networks for mobile communications 2G, 3G,

- Integrated (convergent) networks

- TCP/IP based, 3G, 4G- for fixed or mobile communications

- Next Generation Networks ( ITU-T) ~ 1995-2000

- Future Internet: evolution/revolution for current Internet ( > 2005)

Fundamental Architectural Principles:

- layer N offers to N+1 a service set

- that can be accessed through interfaces (SAP = Service Access Point)

- service implementation is achieved by the protocol of the lower layer

-service primitives - information transport between adjacent layers

- protocols- specify the rules of comm between two peer entities

Criteria for function distribution on layers :

- homogeneity inside a layer

-minimal interactions between layers

- small number of layers

Note about word service usage

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- very general term used in a lot of contexts

- much confusion out of this

- OSI model defines very precise semantic for service- Adopting such semantic we distinguish among:

o Low level services , e.g:

L2 service = connectivity service between two nodes L3 service = connectivity service over a network domain L4 service = E2E connectivity service

o High level services , e.g:

data oriented services: FTP, e-mail, web access to info, transactional

services

multimedia-oriented services: VoIP, video conf, A/Vstreaming, DVB,IPTV, etc.

Curent trends:

-traditionally we want/have low coupling between layers

- today this principle is no longer considered good by all professional communities

- Cross-layer optimisation especially in wireless on L1-L3

- Content aware networks and Network Aware Applications

- pros and cons this approachstill open issue

Base layers (1-3) ( network access and information transfer through network(s)

Upper layers (4-7)

- higher layer processing functions (closer to user application processes)

- usuallylayers 4-7 belong to terminals (endto-end ( E2E) protocols independent of:

- Network technology, Number of networks, Fixed or mobile mode

Important Notes:

o the same function name can be encountered on different layers but with different

semantics

o Not all functions listed must be present in a layer (large variety in practical stacks)

Layer 1 (Physical- PHY) ; Layer 2 (Data Link Layer - DL ); Layer 3 (Network) :

Layer 4 (Transport T); Layer 5 (Terminal SessionS); Layer 6 (Presentation);

Layer 7 (Applicaion) :

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Local Processes

Communication

Processes

Ta

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Local Processes

Communication

Processes

Tb

7 Application

6 Presentation

5 Session

4 Transport

3 Retea

2 Data Link

1 Physical

Different level

Protocols

3 Network

2 Data Link

1 Physical

Transport Protocol

Network node

Physical transmission

medium

User Entities

Service Access

Point

Service Primitives

Protocol Data

Units (PDU)

Information flow circulation

through layers

E2E

Protocols

Network

Transport

Protocols

Higher

Layer

Protocols

Network

Acces

Protocols

Network

environment

OSI Environment

Real systems environment

Figure 1-2 OSI Reference Model

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Figure 1-3 Internetworking example in OSI Model

Note : Service Provider = Transport Service Provider

1.1.3 Real Stack Examples. Incomplete stacks

1.1.3.1 TCP/IP Stack

- TCP/IP stackdifferent from OSI

- much greater success (history, simpler stack, market driven)

- WWW/Internet strengthened the usage of TCP/IP stack

Important note:

o Advances in microelectronics and huge increase of perf/cost allowed to include the

full TCP/IP stack in all terminals (including small mobile devices)

o This naturally creates the posibility to integrate all kind of high level services based

on TCP/IP stack

o That is why TCP/IP ( called Internet is accepted today as a basis for fu ll networkand services integration

Communication models:

o Hierachy criterion

Classic model: Client/server( asymmetric one)

After 2000 Peer to peer (P2P) model

Symmetric model

huge expansion in last years ( ~70% of the total Internet traffic)

o Time criterion

Synchronous communication (usually r.t: VoIP, AVC, VoD, but also FTP,etc.)

Asynchronous communication : e-mail, publish/subscribe

o Mode to get information: push/pull

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- Original TCP/IP stack single architectural plain containing several protocols fordata transfer and control

Application services

Transport (TCP)

Internetworking (IP)

Subnetworks

Figure 1-4 Simplified view of TCP/IP stack

Application(communication between processes or

applications on separate hosts)

Telnet, FTP, E-mail,

SNMP, etc

Transport(end-to-end data transfer service reliable or unreliable)

TCP, UDP

Network layer( network resources mng.,

routing the data to destination)

IP, ICMP, IGMP,

OSPF, etc.

Data link(acces CO or CL to network layer)

(LLC) + MAC

Physical layer

Figure 1-5 Simplified view of the TCP/IP protocol stack

MIME

BGP

(*1)

FTP

Telnet HTTP SMTP RTCP

TCP (Connection oriented)

IP (Connectionless)

(LLC)+MAC (e.g.IEEE 802.x), AAL+ATM,

Physical Layer

ARPRARP

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Video

Voice

RTP SNMP

Multicast

protocols RIP

(*) BOOTP RSVP

UDP (Connectionless)

OSPF

(*1)

ICMP,

IGMP(*2)

IP (Connectionless)

(LLC)+MAC (e.g IEEE 802.x) , AAL+ATM, etc

Physical Layer

ARP RARP

Figure 1-6 Example of TCP/IP stack protocols

(*1)they are not transport protocols but cooperate with IP

MIMEMultipurpose Internet Mail Extensions

BGPBorder Gateway Protocol

HTTPHypertext Transfer Protocol

SMTPSimple Mail Transfer Protocol

SNMPSimple Network Management Protocol

FTPFile Transfer protocol

RTPReal Time Protocol

ICMPInternet Control Messages Protocol

IGMPInternet Group Management Protocol

OSPFOpen Shortest Path First Protocol

Transport:

TCPTransmission Control Protocol (connection oriented -CO)

UDPUser Datagram Protocol ( connectionless CL)

Network: IPInternet Protocol + ICMP, IGMP, BGP, OSPF

Data link Layer:

LLCLogical Link Control + MAC- Medium acces Control

Example: AALATM Adaptation Layer + ATMAsynchronous TransferMode

Example: FTP, TCP, IP, (LLC) + MAC ( driver Ethernet)

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Multicasting:

IGMPInternet Group Management Protocol ( v.1, v.2, v.3)

Multicast routing protocols:

DVMRPDistance Vector Multicast Routing Protocol

PIM-DMProtocol Independent MulticastDense ModePIM-SMProtocol Independent MulticastSparse Mode

CBTCore based Tree

MOSPFMulticast OSPFmulticast extension of OSPF

MBGPMulticast BGPextension of BGP to multicast

Multicast transport protocols:

RMTPReliable Multicast Transport Protocol

SRMScalable Reliable Multicast Protocol

MFTPMulticast File Transfer ProtocolPGMPretty Good Multicast

Ping FTPTelnet

Rlogin

SMTP

X

Trace-

route

DNS

TFTP

BOOTP

SNMP

NFS+RPC

User

process

UDPTCP

IP

IGMP

ARP RARP

ICMP

(LLC) MAC

Appl

Transport

Data link

Network

User

processes

Figure 1-7 Example of logical links between layers

ARPAddress Resolution Protocol

RARPReverse Address Resolution Protocol

TFTPTrivial FTP, BOOTPBootstrap Protocol

NFSNetwork File Server

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1.1.3.2 IEEE 802.x standards for LAN, MAN

Figure 1-8 IEEE 802 LAN/MAN Standards- examples

1.1.3.3 Signalling System No.7

SS7:

- datagram virtual network for digital circuit switching network ( ex. ISDN, GSM) control

- Control plane for Telecom Digital Networkcontaining the signaling protocols

Example for GSM - MSC:

(MSC- Message Switching Centremain switch in GSM)- MTP 1-2-3subsystem for message transport (layers 1-3)

- Layers 4-5-6 : void

- signaling applications : TUP, ISUP, MAP, etc

ISUP, TUP, MAP, TCAP

MTP-1

MTP-2

MTP-3

7

4-6

3

2

1

Control Plane

of Telecom

Network

SCCP

Figure 1-9 Example of incomplete stack: SS7 signalling stack

Signalling Connections Control Part (SCCP)optionally completes the L3 (CO mode for L3)

- applications :

TCAP -"Transaction Capabilities Application Part" - realizes a common general transaction service

offered to other applications

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Transaction : communication of type query/response (suitable for low volume of information

transfer)

Examples of signalling applications :

TUP - "Telephonic User Part"- telephonic call control

ISUP - "ISDN User Part" - ISDN call control

MAP - "Mobile Application Part"mobility control in GSM

All these applications use the message transport part MTP1-3

in CL mode ( if they work directly over MTP 3)

in CO mode ( if they work directly over SCCP)

1.1.3.4 MPLS architecture

Packet Forwarding in IP Networks

IP forwarding is done independently at every hop

IP forwarding decision is made on:

o

Packet header, Routing algorithm output (routing table)

o Note: Searching in routing table- time consuming operation done for every

packet

Each IP hop runs its own instance of the routing algorithm

Each IP hop makes its own forwarding decisions

Figure 1-10 IP routing example (Cisco Systems)

MPLS ideas

Packet forwarding is done based on label switching (not IP addresses, no search in the

forwarding table of routers) Labels are shortallow indexed addressing- fast switching

Labels are assigned when the packets enter into the network (edge)

Assignment is result of classification at the ingress node in a MPLS domain (criteria:

destination, VPN, QoS, TE, Multicast )

Labels are added in frontof the IP packets

1.1.3.4.1 MPLS IP stack

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Application

Transport TCP, UDP

Internet layer IP, ICMP, IGMP,OSPF, etc.

MPLS sublayer

Data link layer (LLC) + MAC

Physical layer

Figure 1-11 MPLS oriented IP stack

IP-H TCP-H Application Data IP Datgram

MPLS-H IP-H TCP-H Application Data Labelled IP

Datagram

LABEL EXP S TTL Header MPLS

20 Bit 3 1 832 bit

Figure 1-12 MPLS label adding

1.2 Multiple Planes Architectures

1.2.1 Principles

Ongoing standardization : IETF, ITU-T ETSI, IEEE, 3GPP

Telecom originated layered architectures: more than one architectural plane

IETF (TCP/IP- Internet) stackoriginally only one plane

Nowadays- recognized the need of defining several cooperating architectural planes

Reasons: Real systems/networks deals with:

- user data flow transfer

- network resources ( paths, links, buffers, etc. ) should be controlled

- short time scale, long time scale

- high level services should be controlled (short and long time scale)

Architectural Planes

Data plane ( DPl)- transport of user data traffic directly:

o Examples of functions: traffic classification, packet marking traffic policing, traffic

shaping, buffer management, congestion avoidance, queuing and scheduling

o transfer the user dataflows and accomplish the traffic control mechanisms to assure

the desired level of QoS

Control plane (CPl)

o controls the pathways for user data traffic: e.g. Admission control, Routing, Resource

reservation.

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o short term actions for resource and traffic engineering and control, including routing.

In multi-domain environment theMPl and also CPl are logically divided in two sub-

planes: inter-domain and intra-domain. This approach allows each domain to have its

own management and control policies and mechanisms.

Management plane (MPl)

o the operation, administration, and management aspects of the resources and services

to serve user data traffic: Monitoring, Management Policies (management based not

on fixed configuration of network elements but on set of rules), Service

Management, Service and network restoration.

o long term actions related to resource and traffic management in order to assure the

desired QoS levels for the users and also efficient utilization of the network resources

Examples of early multiple plane architectures (DPl + CPl + MPl):

ISDN , GSM, BISDN

- reason: telecom design philosophy (user data have been seen long time ago - from the

beginning of telecom systems as separate entities from signalling and management) data s

TCP/IP :

- Initially: mono-plane (data + control + management)

- Currently it becomes multi-plane (DPl + CPl + MPl)

New stacks- multiple plane: IEEE802.16, 3G, 4G

1.2.2 Signalling Issues

Signaling = actions performed in the control plane :

-

convey application (or network) performance requirements

- reserve network resources across the network

- discover routes

- general control messages

- QoS related signalling

QoS signaling : in bandor out of band.

In band

- signalling info is part of the associated data traffic( typically presented in a particular header fieldof the data packets.(e.g., the TOS field in IPv4 as in DiffServ and 802.1p)

- Performed in the data plane neither introduces additional traffic into the network nor incurs setup

delay for the data traffic.

- not suitable for resource reservation or QoS routing, which needs to be done a priori before data

transmission

- in-band signaling by definition is path-coupled (signaling nodes must be collocated with routers)

Out of band

- signalling info - carried by dedicated packets, separate from the associated data traffic. - introducesextra traffic into the network and incurs an overhead for delivering desired network performance

it entails the use of a signaling protocol and further processing above the network layer, which tends

to render slower responses than in-band signaling.

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- lends itself naturally to resource reservation or QoS routing.

- depending on whether the signaling path is closely tied to the associated data path, signaling is path-

coupledor decoupled

Path-coupled

- signaling nodes must be collocated with routers

signaling messages - routed only through the nodes that are potentially on the data path.

- advantage of reduced overall signaling processing cost (since it leverages network- layer routing

tasks)

- disadvantage of inflexibility in upgrading routers or in integrating control entities (e.g., policy

servers) not on the data path (or nontraditional routing methods)

If a path-coupled mechanism involves a signaling protocol, routers need to support the protocol and

be able to process related signaling messages

- Example of a path-coupled signaling protocol : RSVP

Path-decoupled

- signaling messages are routed through nodes that are not assumed to be on the data path

only out-of-band signaling may be path-decoupled. (to date, most out-of-band QoS signaling schemes

are path coupled.)

- signaling nodes should be dedicated and separate from routers

- advantage of flexibility in deploying and upgrading signaling nodes independent of routers or in

integrating control entities not on the data path

- disadvantage of added complexity and cost in overall processing and operational tasks.

Example: Session Initiation Protocol for VoIP, videoconference, etc.

Standardization Effort

NSIS ( Next Step in Signalling)

- Standards efforts underway specifically dealing with QoS signaling- e.g. IETFnsis working group

- developing a flexible signaling framework with path-coupled QoS signaling as its initial major

application

- a QoS signaling protocol defined under the framework - expected to address the limitations of RSVP

On path-decoupled signaling there seems not enough support in the IETF for a new project after

some explorative discussion

1.2.3 Next Generation Networks Architecture- high level view

Standardization Players

ATIS NGN FG: Alliance for Telecommunication Industry Solutions, Next Generation Networks

Focus Group - USA

ITU-T NGN FG: International Telecommunication Union (Telecom), Next Generation NetworksFocus Group

ETSI TISPAN: European Telecommunications Standards Institute, Telecoms & Internet

converged Services & Protocols for Advanced Networks

3GPP: Third Generation Partnershipstandardization in Mobile 3G networks

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NGN

packet-based network

able to provide Telecommunication multiple services

able to make use ofmultiple broadband,

QoS-enabled transporttechnologies

service-related functions are independent from underlying transport-related technologies.

enables unfettered access for users to networks and to competing service providers and/or services

of their choice.

supports generalized mobility which will allow consistent and ubiquitous provision of services to

users.

Key requirements of an NGN Architecture

Trust:Operator should be able to trust the network. User should be able to trust the operator

Reliability: Users should find it reliable

Availability: Network should always be available

Quality: Able to control Quality of the Service

Accountability: Determine usage of the Service

Legal: Comply with laws in the local jurisdictions

GeneralizedMobility support

Note: Classical Internet cannot respond in very controllable manner to the above requirements

NGN characteristics

NGN: new telecommunications network for broadband fixed access

facilitates convergence of networks and services

enables different business models across access, core network and service domains

it is an IP based network

IETFSession Initiation Protocol (SIP) will be used for call & session control

3GPP release 6 (2004) IMS will be the base for NGN IP Multimedia Subsystem

enables any IP access to Operator IMS; from

Mobile domain

Home domain

Enterprise domain

enables service mobility

enables interworking towards circuit switched networks

maintains Service Operator control for IMS signaling & media traffic

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Transport Level

Applications and

Service Level

Management

Plane

User (Data)

Plane

Control

Plane

INTERNET

SCN

Figure 1-13 NGN Architecture

Design Principles

Service is rendered in exchange for value

o explicitly requested and explicitly stopped, providing a basis for charging

o only delivered to authorized users

o

only saleable if QoS and security can be guaranteedNote : Traditional Internet does not offer this!

Dedicated VoIP infrastructure is expensiveo Only a converged(packet) network that supports multiple services over one

infrastructure can be commercially viable NGN will be deployed in an unbundled environment

o Competition on service values other than price

o Support for value-added applications

Affordable multi-service architecture

o Do not mix application and transport!

Support service for roaming users

o Service provided from HOME service provider

o New Home Box concept

End user as content consumer and/or content provider

Service provider determines media route

o Service may include in-band media events

o Support for Lawful Intercept

o

Call Routing follows the money

o QoS flows cost money so service providers will do least cost routing on it (providing

QoS can be met)

Technologies are transient:NGN is technology independent !

Clear separation of Application/Services from Transport Services

o Note that this concept is in discussion today!! Provide a modular architectural framework which is easy to introduce and extend.

Use a meta-protocol to specify the technology and inter-working to all applicable protocols

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1.3 Business Models for (Multimedia) Communication Architectures

1.3.1.1 Customers and Users

Customer (CS) (may be a subscriber) :- entity, having legal ability to subscribe to QoS-based services offered byProviders

(PR) orResellers (RS)

- target recipients of QoS-based services: CS/PR or CS/RS interaction

-

Examples of CS: Householders, SMEs, large corporations, universities or public

organisations

Service Level Agreements (SLA)- concluded betrween CS and providers

CS differentiation by : size , type of business, type of services required

User (US)

- entity (human or process) - named by a CS and appropriately identified by PR for

actually requesting/accessing and using the QoS-based services cf. SLAs

- USs are end-users of the services, they can only exist in association with a CS

- may be associated with one or several CS using services according to the agreed

SLAs of the respective CS. (e.g. Company = Customer, End User = employee)

Note: In the current public internet, the majority of users are subscribers for Connectivity servicesonly and maybe for a small subset of high level services (e.g e-mail)

- there is no SLA concluded for high level services quality; e.g for media A/V

streaming, IPTV, etc.

- best effort access to high level services is practised but with no guarantees

1.3.1.2 Providers (PR)

PR types :

(High Level) Service Providers (SP) IP Network Providers (NP)

Physical Connectivity Providers (PHYP) (or PHY infrastructure Providers)

Resellers (RS)

Content Providers (CP)

Network Providers (NPs)

- offer QoS-based plain IP connectivity services

- own and administer an IP network infrastructure

- may interact withAccess Network Providers'(ANP) or CS can be connected directly

to NPs

-

Expanding the geographical span of NPs- Interconnected NPs - corresponding peering agreements

- IP NPs differentiation: small ( e.g. for a city) , medium (region) and large ( e.g.

continental)

(High Level) Service Providers (SPs)

- offer higher-level (possible QoS-based) services e.g. : e-mail, VoIP, VoD, IPTV,

A/VC, etc.

- owns or not an IP network infrastructure

- administer a logical infrastructure to provision services (e.g. VoIP gateways, IP

videoservers, content distribution servers)

-

may rely on the connectivity services offered by NPs (SPs Providers' interact withNPs following a customer-provider paradigm based on SLAs

- expanding the geographical scope and augmenting the portfolio of the services

offered SP may interact with each other

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- size : small, medium and large

Physical Connectivity Providers (PHYP)

- offer physical connectivity services between determined locations

- services may also be offered in higher layers (layer-3 e.g. IP), ( but only between

specific points)

- distinguished by their target market:

Facilities (Infrastructure) Providers (FP)

Access Network Providers (AP) (could be seen as distinct stakeholders)

FPs services - are mainly offered to IP NPs (link-layer connectivity , interconnect with their peers

FPs differentiation : size of technology deployment means

ANPs - connect CS premises equipment to the SPs or NPs equipment

- own and administer appropriate infrastructure

- may be differentiated by- technology (e.g. POTS, FR, ISDN, xDSL, WLAN, Ethernet, WiMAX, hybrid)

- their deployment means and their size

- may not be present as a distinct stakeholder in the chain of QoS-service delivery

- may be distinct administrative domains, interacting at a business level with SPs /NPs and/or

CSs

Interactions between Providers

- mainly governed by the legislations of the established legal telecom regulation framework

- may follow a customer-provider and/or a consumer-producer paradigm on the basis of

SLAs

Reseller (RS)

- intermediaries in offering the QoS-based services of the PRs to the CSs

- offer market-penetration services (e.g. sales force, distribution/selling points) to PRs for

promoting and selling their QoS-based services in the market

- may promote the QoS-based services of the PRs either 'as they are' or with 'value-added',

however adhering to the SLAs of the services as required by the 'Providers'

- interact with :

CSs on a customer-provider paradigm (SLA based)

PRs based upon respective commercial agreements..

Different types RSs:

- according to whether they introduce value-added or not

- their market penetration means

- size ( # of of points of presence and/or sales force)

RSs examples: Dealers, electronic/computers commercial chains, service portals

Content Provider (CP)

-

an entity (organisation) gathering/creating, maintain, and distributing digitalinformation.

- owns/operates hosts = source of downloadable content

- might not own any networking infrastructure to deliver the content

- content is offered to the customers or service providers.

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- can contain : Content Manager(CM); several Content Servers (CS

New enties (in the perspective of Future Internet)

Virtual Network Provider (VNP)

- composes and configures and offer Virtual Network slices, i.e., a set of virtual

resources at request of higher layers, as a consequence of its provisioning policy orduring self-healing operations

- this approach avoids for the higher layers to establish direct relationships with

infrastructure providers and to take care of inter-domain connections at physical

layer.

Virtual Network Operator (VNO)

- manages and exploits the VNEt s provided by VNPs , on behalf of HLSPs or end

users

Note: the same organisational entity migh play the both roles :VNP and VNO

1.3.2 Service Level Agreements/Specifications (SLA/SLS)

SLA

it is a contract : documented result of a negotiation between a customerand aprovider

of a service that specifies the levels of availability, serviceability, performance,

operation or other attributes of the transport service

SLA contains technical and non-technical terms and conditions

May be established offline or online (using negotiation oriented-protocols)

Service Level Specification (SLS)

It is a part of SLA SLS = set of technical parameters and their values, defining the service, offered by the provbider

to the customer

o e.g. service offered to a traffic stream by a network domain (e.g. Diffserv domain)

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(HIGH LEVEL)SERVICEPROVIDER 1

USER

RESELLER

CUSTOMERIP NETWORK

PROVIDER 1

PHYSICALCONNECTIVITY

PROVIDER 1

PROVIDER/OPERATOR 1

HIGH LEVEL

SERVICEPROVIDER N

IP NETWORK

PROVIDER M

PHYSICALCONNECTIVITY

PROVIDER P

. . . . .

May be joinedwithin the sameentity

. . . . .

. . . . .

Content

Provider

USER

USER

Figure 1-14 Generic IP Business Model (I) - and business relationships (SLA)

Figure 1-15 Example: IP Business Models (II) - Hub model and Cascade model

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1.4 Examples of Multiple Plane Architectures

1.4.1 IEEE 802.16 multi-plane stack

IEEE 802.16 : PHY + MAC

Multiple plane architecture: Data Plane(DPl), Control Plane (CPl), Management Plane (MPl)

Figure 1-16 Basic IEEE 802.16 multi-plane protocol stack

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Figure 1-17 (IEEE 802.16g-05/008r2, December 2005)

Figure 1-18 Relation IEEE802.16 vs. WiMAX NWG

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1.4.2 Generic Example of a multi-plane architecture

Stratum:Applicatio

n

Stratum:Transport

Data

Plane

ApplicationApplication Data flow-user

Inter-domainResources and traffic Mng.

Access & Core

Intra-domainResources and traffic Mng.

Access & Core

Services and session Control

ControlPlan

Control ResurseInter si Intra domeniu

Service Mng. (Planning provisioning,Offering, monitoring)

Mana

gement

Plane

Control flow

Figure 1-19 Generic example of a multi-plane architecture

1.4.3 Architectural stack for wireless heterogeneous mesh network

European Research Project, FP7, 2008-2011

SMART-antenna multimode wireless mesh Network

Vertical structure of the architectural stack:

Application and Service Macro-Layer (ASM)

Transport Macro-Layer (TM) (layers 1-4 in the OSI terminology)

ASM- contains applications (real-time or not real-time), which in their turn may use services

offered by the system (e.g. a given complex application may use, among others, a VoIP

service).

TM- abstraction of layers providing IP connectivity services, (any PHY and MACtechnologies)

This view offers a complete independency to the application and service providers with

respect to the transport infrastructure.

The application and service providers can be third parties using connectivity services providedby the Transport Macro-Layer based on agreed Service Level Agreements (SLA) betweenthem.

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Applications &Services

PHY

Multimode MAC

( 802.11, 802.16, ..)

ConvergenceSublayer

TCP/IP

Services andSession

Mng&Ctrl

PHY Mng&CtrlSmart Antennas and RAT Control

Data Plane Management and Control Plane

ResourceMng &Control

Coordinator

AccesControl

MobilityMng

QoS

Data Link Mng&CtrlQoS, Mobility, RR Control,

Scheduling

NetworkCoding

CrossLay

er

Optimization

Trans

ortMacro-La

er

Applicationand

ServiceMacro-Lay

er

DataFlows

Routing

Sec

RM&C

Figure 1-20 Multi-plane generic functional architecture

The architecture is horizontally divided into MPl, CPl, DPl.

The Data Plane (DPl) processes the data packets (e.g. traffic classification and conditioning,

conversion, coding/transcoding, prioritizing, marking and queuing) and transfer the multimedia flows.

At ASM level, the DPl may run mechanisms to adapt/transform media flows (fixed or scalable

coding/decoding, transcoding, compression, conversion, security operations) under the control

of some Media Control Middleware (MCM).

At TM level DPl runs all network level data flow mechanisms for traffic control and QoS

assurance if guarantees are required from the connectivity service offered by this macro-layer.

The MPl performs essentially mid-long-term functions related to:

At ASM: management of high level services (e.g subscription, invocation, etc.)

At TM network, resources and traffic management operations.

The CPl performs the short-term control functions including (at different layers):

At ASM: it accomplishes the service and session control.

At TM: PHY processing control, MAC processing, routing, mobility,resource and QoS

control, security, etc.

Further vertical decomposition can be seen in the TM

The lower layers covers Data Link layers and below. The upper layers cover the network

and traditional Layer 4 (transport).

A convergence layer will solve the compatibility with Layer 3. The MPL and CPl contains

all low-layer mechanisms for PHY/MAC (these are usually defined in the 802.x

standards) but also management and control methods/algorithms which are intentionally

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not specified by the standards (to give freedom to constructors to use their best knowhow for them).

The QoS will be assured with several levels of guarantee (depending on application

requirements), by considering two time scale approaches for resource management and

control:

provisioning for those applications flows where future resource consumptions

can be forecasted (e.g. media distribution applications), done at aggregated

levels based on Service Level Agreements/Specifications between entities;

per session/flow QoS control for dynamic call requests.

1.4.4 Control Plane in GSM (2G)

PLMN Public Land Mobile Network

MSMobile Station

BTSBase Tranceiver Station

BSC Base Station ControllerMSC Mobile Switching Center

GMSC Gateway MSC

HLR/VLR Home Visitor Location Register

EIREquipment Identity Register

AUC- Authentication Center

ISDN Integrated Services Digital Network

PSPDN Packet Switched Public Data Network

EIRBSC

MS

HLR

GMSC

MSC

VLR

MSC

VLR

PLMN

AUC

ISDN/IN

PSTN

PSPDN Other PLMNs

MS

BTS

Figure 1-21 GSM Network General Architecture

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Distribution

DTAPBSSMAP

BSSAP

MS BTS BSC

RIL3-CM

RIL3-

MM

DTAP

RIL3-

RR

I/F radio

LAPDm

4-5-

3

Distrib

Um Abis

RSM

LAPD

64 kb/s

4-5-6

3

RIL3_RR

SCCP

4-5-6

MTP1-3

Releu

LAPDm

I/F radio

4-5-6

3

LAPD

64 kb/s

4-5-6

3

RIL3_RR RSM

Relay

to MSC

anchor

Protocol MM

Protocol CM

PHY Conections

7 OSI-RM

2

1

BSS

MSC/VLR

Relay

A

SCCP

4-5-6

MTP1-3

Distribution

DTAPBSSMAP

BSSAP

RIL3-CM

RIL3-MM MAP/E

MAP/G

TCAP

NSS

Figure 1-22 Control Plane in GSM

RIL3 - Radio Interface Layer; CM, MM, RR - Connection, Mobility, Radio Resource -

Management; Distrib distribution RSM - Radio Subsystem Management; BSSAP - Base StationSubsystem Appl. Part;

2 INTERCONNECTION- REVISION

(Romanian)

2.1 Moduri de lucru cu i fr conexiune CO/CL

CO/CL

DTE-A DTE-B

ISa

SN3

SN2SN1

ISc

ISb DTE-C

14 3 2

n CO PDU

32

1

1CL PDU

Figura 2-1 Modul de lucru cu i fr conexiune

ISSistem intermediar; SN - subreea

- COfiecare IS joncioneaz ntre ele dou segmente de circuit virtual ( Ex. ATM, MPLS)

- CL - fiecare IS ia pentru fiecare PDU o decizie de dirijare ( forwarding n mod independentde cele anterioarenu se garanteaz pstrarea secvenei datelor

-

Interneti poate baza transportul sau pe suporturi fizice ale altor reele der telecomunicatii (PSTN, ISDN, CATV, etc.) sau pe suportul unor reele publice de pachete de arie mare

- elemente interconectabile: sisteme de capt (hosts) , sisteme intermediare (puni,comutatoare de nivel doi, comutatoare MPLS, rutere), subreele

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A B

P2

P3

P1

PPR

R R

A B

P2

P3

P1

PN

PN

PN

Telco

Figura 2-2 a. Reea public cu comutaie de pachete b. Reea Internet

PNPacket Network

2.2 Cerinele unui serviciu de interconectare (la nivel trei)- s asigure link-uri ntre reele diferite

- adresare i rutare/dirijare prin reele diferite

- contabilizarea utilizrii rersurselor pentru a ti starea fiecrui element de interconectare ( lanivel de element de reea; la nivel de domeniu administrativ)

- s furnizeze serviciile de mai sus astfel nct s se poat interconecta la reele de tipuri diferitefr a modifica infrastructura intern a fiecreia; deci trebuie rezolvate problemele:

- scheme de adresare diferite

- dimensiuni maxime diferite ale unitilor de date (este necesarsegmentatare/reasamblare)

- mecanisme de acces la reea diferite

- valori diferite de expirare pentru diverse temporizatoare ( timers )

- diferite metode (sau inexistente) de recuperare a erorilor

- rapoarte de stare

- tehnici de rutare diferite

- controlul accesului utilizatorilormecanisme diferite

- mod de lucru CO/CL

NSAP_1

SNICP

SNDCP

SNDAP

DL

PHY

SNDCP

SNDAP DL

PHY

SNDCPSNDAPDL

PHY

Releu + rutare: SNICP

T

IS

ES/H

Nivel

N = 3

Retea 1 Retea 2

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Figura 2-3 Architectura generic anivelului de reea

soluie pentru acomodarea diferitelor reele: divizarea nivelului reea n trei subnivele:

SNICP, SNDCP, SNDAP

SNICP Subnetwork Independent Convergence Protocol

SNDCP - Subnetwork Dependent Convergence Protocol

SNDAP - Subnetwork Dependent Access Protocol (can be void)

2.3 Modul de lucru CO ( conexiune la nivel reea)

- faze: stabilire, meninere, eliberare de VC

- este nevoie ca toate subreelele sa cunoasc acelai protocol CO pentru a putea construi VCmulti-reea

- deci presupunem c fiecare subreea ofer acelai serviciu de conectivitate (de nivel trei!)

de tip CO; rezultatul final este concatenarea unor segmente de VC (virtual circuits)

- Figura 2-4.a: - mod de lucru CO - accesul la subreele se face prin intermediul aceluiaiprotocol de reea nu este nevoie de mai multe subnivele

- funciunile unui ruter CO :

o funcie de releu pentru unitile de date de la o reea la alta ( forwarding)

o selectarea iniial a rutei (nod cu nod) are loc n faza de stabilire a conexiunii

o fiecare ruter jonctioneaz ntre ele segmente de VC (conexiuni logice)

2.4 Modul de lucru CL (fara conexiune la nivel reea)

- tratare independent a fiecarei uniti de date n fiecare nod de reea (ruter)

- este util a defini un protocol de reea comun, independent de diferite tipuri de subreeaparticulare: IP = SNICP (RFC 791) ; ISO 8473 Connectionless Network Protocol (CLNP) -

are funciuni similare

- accesul la subreele particulare se face prin subnivelul de adaptare dependent de tehnologiaspecific (SNDAP= N1, N2, N3; SNDCP poate fi necesar sau nu, depinde de caz)

- Figura 2-4.bexemplu de stiv

- Avantaje CL:

- robustete (datorit tratrii independente a unitilor de date - datagrame); flexibilitate (poate

lucra peste subreele CO sau CL); ofer cel mai potrivit serviciu pentru un nivel transport detip CL

- Dezavantaje CL:

- servicu nativ fr garanii ( best effort )relativ la band, pierderi, ntrzieri de transfer,fluctuaia de intrziere, secvenialitate

2.5 Interconectarea de tip punte (Bridge approach)

- Punte = bridge = releu de nivel MAC lucrnd n mod CL

- Nu se analizeaz adresele de nivel trei

- Utilizate de regul pentru interconectare de LAN-uri

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A BSN2SN1 SN3

T

N

L1

P1

RN N

L1 L2

P1 P2

RN N

L2 L3

P2 P3

T

N

L3

P3

T

I

N1

L1

P1

I

N1 N2

L1 L2

P1 P2

I

N2 N3

L2 L3

P2 P3

T

I

N3

L3

P3

T

I

LLC

MAC1

P1

Relay

MAC1 MAC2

P1 P2

T

I

LLC

MAC3

P3

Relay

MAC2 MAC3

P2 P3

a

c

b

ISbISa

Figura 2-4 Arhitecturi de interconectare

a. mod CO b. mod CL c. Mod de lucru de tip punte ( Bridge operation)

2.6 Exemple de interconectri

Examplu 1: Conexiune FTP client-server

Client

FTP

TCP

IP

MAC1

ETH

PHY1

IP

MAC1

ETH

MAC2

TR

PHY1 PHY2

Server

FTP

TCP

IP

MAC2

TR

PHY2

Figura 2-5 Acces FTP acces ntre dou reele LAN via un ruter

Examplu 2: IP peste o configuraie de subrutele: LAN-reea public de pachete -LAN

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TCP

IP

LLC

MAC

P1

IPX.25-3

LLC

MAC

X.25-2

P1 P2

A BLAN1 LAN2WAN

X.25R1 R2

IPX.25-3

LLCX.25-2

MAC

P2 P3

TCP

IP

LLC

MAC

P3

12

3 4

786

5

1,6, 7 IP-H TCP-H Date

2, 5 LLC1-H IP-H TCP-H Date

MAC1-H LLC1-H IP-H TCP-H Date MAC1-T

8 P-H IP-H TCP-H Date

DL-H P-H IP-H TCP-H Date DL-T

9

3,4

9

Tunel X.25

Figura 2-6 Operarea protocolului Internet via reea public de pachete (WAN ex.X.25)

Note:- avem acelai nivel IP ( SNICP) n toate sistemele ( A, R1, R2, B)

- au loc ncapsulri/decapsulri succesive n timp ce PDU traverseaz in sus i in jos nivelelefuncionale (vezi figura)

- se face segmentare/reasamblare daca e necesar

- informatie de rutare: necesara in R1 i R2- R1 sau R2 ofera un serviciu de conectivitate nefiabil (best effort)

- congestii posibile (deoarece banda unui VC este limitat n reeaua X.25)- intarziere de transfer variabil

Examplu 3: Interconectare de tip punte (distant) peste o reea de pachete

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\

3

LLC

MAC

P1

Releu

X.25-3

MAC X.25-2

P1 P2

A BLAN1 LAN2WAN

X.25B1 B2

Releu

X.25-3

X.25-2 MAC

P2 P3

3

LLC

MAC

P3

1

2

3 4 6

5

1 Data

2 LLC-H Data

3,4 MAC-H LLC-H Data MAC-T

5 X.25-H MAC-H P-H Data MAC-TDL-H X.25-H MAC-H P-H Data MAC-T DL-T6

Figura 2-7Operarea protocolului Internet prin puni interconectate la nivel doi printr-o reeade pachete ( exemplu: X.25 WAN )

- presupunem c avem n LAN1 si LAN2 acelai MAC dei nu este obligatoriu

- diferena fa de interconectarea IP/WAN este ca in acest caz cadrele de nivel doi sunttransportate prin tunelul X.25 i nu datgramele IP

2.6.1 Interconectarea de reele LAN prin puni (B)

Interconectarea de nivel 1 ( prin repetor):

o Permite extinderea distantei fizice

o Stiva arhitectural este aceeai n toate sistemele (nivel 1- nivel 7)

o Repetorul: obiect de interconectare de nivel fizic care regenereaza formatul electric al

semnalului

o Repetor: cost sczut, dar non-inteligent

o

Efect generalaceeai reea dar cu extindere pe dimensiuni fizice mai mario Exemplu clasic: reea Ethernet cu repetoare (Hub)

Interconectarea la nivel 2 a retelelor locale (LAN ): prin punti (B =Bridge)

- Interconectri pentru reele cu MAC diferit; LLC i nivele >2 aceleai

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Aplicatie

TCP/UDP

IP

(LLC)*MAC1-ETH

PHY1

Aplicatie

TCP/UDP

IP

(LLC)*MAC2TR

PHY2

Releu (LLC partial)

MAC1-ETH MAC2-TR

PHY1 PHY2

LAN 1LAN 2

Figura 2-8 Arhitectura de interconectare prin puni

(*) n principiu LLC poate lipsi

Cadrele recepionate de ctre B pe un port (de la un segment de LAN) : memorate, verificate

CRC, convertite la formatul noului MAC, redirijate Are loc o filtrare a adreselor locale (adrese MAC)

Avantaje ale punilor (sunt mai importante dect dezavantajele)

o Memorare + retransmisie MAC1 poate fi diferit de MAC2. Exemplu : 802.3 802.5posibile extensii gradate spre tehnologii diferite

o Elimin constrngerile de distan fizic (repetorul interconectare de nivel 1 nu faceasta)

o B este releu pe baz de adres MAC- transparent la nivele superioare

o Uureaz gestionarea reelelor mai mari (dac n B se include SW de management)

o Crete securitatea reelelor (datorit filtrrii traficului local/extern)

o Creste fiabilitatea /disponibilitatea segmentelor

o Conceptul de B se extinde imediat la comutatoare de nivel 2 ( Layer 2 switch)

o Permit crearea de LAN-uri virtuale (VLAN)foarte important in practic

Dezavantaje ale punilor (Problemele de principiu greu rezolvabile/netriviale)

o Lungime diferit de cadre

o Lucru diferit cu prioriti

o Incompatibilitate ntre valorile timerelor utilizate

o probleme de gestiune a configuraiei mixte

Alte probleme:

- lipsa de control de flux la nivel MAC posibilitatea suprancrcrii memoriei din B

- memorare + retransmisie ntrzieri mai mari dect la interconectarea repetoare

- probleme cu expirri de timere n MAC-uri diferite dac distana este mare

- modificarea cadrelor la traversarea B + calculul pentru noul CRC erori eventuale n timpultranslatrii (releu) care rmn nedetectate

Concluzii : avantajele sunt mai mari dect dezavantajele B utilizate foarte frecvent ( azi sub

form de comutatoare de nivel 2)Exemple de standarde:

IEEE 802.1 -puni transparente

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IEEE 802.5conine o parte referitoare la B cu rutare de tip surs

2.6.1.1 Puni transparente (Transparent Bridges- TB)

Caracteristici generale

prezena n reea a (n>1) puni - transparena pentru staiile ce intercomunic

TB- se iniializeaz i configureaz automat la introducerea n reea (fr o intervenie special

din partea restului reelei)

reconfigurarea dinamic n timpul funcionrii

sunt prevzute cu n 2 porturi pentru n 2 LAN-uri

fiecare port are chip-set-uri MAC corespunztoare tipului de LAN i SW de gestiunecorespunztor

( SW initializeaz chip-set-ul; gestioneaz memoria (buffere) aloc buffere pentru chip-setMAC dinMAC de recepie ; paseaz buffere pline spre chip-setMAC de transmisie ).

Extensie 1: comutatoare de nivel 2 ( punti cu n > 2 porturi) eventual cu tehnologii diferite

Extensie 2 : VLAN

2.6.1.2 Punti cu rutare de tip sursa

Punti transparente : B participa in mod colectiv la rutare intr-un mod transparent pentru

statii . Statiile comunica intre ele ca i cum ar fi pe acelasi LAN.

Punti cu rutare sursa : statia src include in cadrele emise informatii de rutare pana la

destinatie . Info- rutare in antetul cadrului folosita de punti pentru rutare (fiecare Bdetermina daca acel cadru trebuie dirijat spre alt segment sau nu)

Informatia de rutare = secventa de perechi ( S- B ) unde S= segment ( adresa LAN) B= id

punte

Observatie Rutarea sursa se utilizeaza in special in IEEE 802.5 ( fiind o parte a acestuistandard) Exemplu cadru 802.5

3 ROUTING ALGORITHMS AND PROTOCOLS

(Romanian)

Not complete

3.1 GeneralitatiProtocol de rutare +algoritm + mecanism de schimb de nesaje intre nodurile retelei

Retea-abstractizata printr-un graf orientat/neorientat

A

D

C

B2

12

1

3

1

asimetric

asimetric

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Figura 3-1 Exemplu simplu de graf orientat

G(V,E); V- set de noduri; Eedge set set de link-uri

Ponderi/costuri asociate link-urilor

Problema de rutare: gasirea unui arbore cu cost minm de la un nod sursa catre orice destinatie

- costul oricarei cai = minim ( SPT = Shortest path tree)

- cost total al arborelui = minim (arbori Steiner)

Clasificarea algoritmilor de rutare

- Centralizati /distribuiti de tip mixt

Criterii de cost/metrica:

- metrica simpla ( 1 criteriu)

- compusamai multe criterii

Exemple de metrici: nr. de noduri traversate, intarziere ( dinamic) , 1/B, cost admin., grad de incarcarea unui link (dinamic), cost total al unui arbore, etc.

Obs: n>1 metrici => problemne NP-hard; se cauta solutii aproximante quasi-optime

Se poate dem. in unele cazuri care este departarea fata de optimul teoretic

Exemple:

2 5 8 11

3

7

9

10

4

6

M= {1,5,6,9,11}

Cost/link =1

S

a.

Network graph

1

2 5 8 11

3

7

9

10

4

6

M= {1,5,6,9,11}

Cost/link =1

S

b.

Shortest Path Tree (SPT)Source Specific Tree

C = 8

Dmax = 3

Dav =2.5

1

Figura 3-2 Exemplu de graf si SPT

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2 5 8 11

3

7

9

10

4

6

M= {1,5,6,9,11}

Cost/link =1

S

Group Shared Tree

Example of Steiner Tree

1

Figura 3-3 Arbore Steiner- exemplu

Steiner Tree Problem in Networks (SPN) - NP-complete problem

Given: G = (V,E)undirected M = multicast group included in V cuv = cost of link (u,v); u,v V Required: t = (VT, ET), which spans M so that

imumc

T

uv

Evu

min),(

Steiner nodes = nodes u,v VT but they do not belong to MExample

Steiner nodes= {4,7} M = {1,5,6,9,11}

CT = 6 !! less than in SPT DSav = (2 + 3 + 4 + 3)/4 = 12/4 = 3

Constrangeri:

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Constraints to a link (e.g bandwidth, available buffer, etc.). to a path or to the whole tree,

Tree constraints can be ( m = metric) additive (e.g. E2E delay on every path from source to destination)

m(u,v) = m(u,i) + m(i,j) + m(pv), for a path P( u,i,j, ..v) Sum of the costs on all edges of the tree

multiplicative ( e.g the probability that a packet will reach the destination,being given the loss probability on each link)

m(u,v) = m(u,i) *m(i,j) * m(pv), for a path P( u,I,j, ..v) concave (e.g. minimum bandwidth on a chain of links on a path)

m(u,v) = Min{ m(u,i), m(i,j), m(pv)}, for a path P( u,I,j, ..v)

Moduri de lucru ale protocolului:

- Proactiv/reactiv/mixt

Clasificare d.p.d.v cunoasterea topologiei:

- vectori de distanta

- link state

Probleme suplimentare:

- mobilitatea; inteferentein radio; refacerea rutelor deteriorate

- problema link-urilor asimetrice

- problema cailor diferite in cele doua sensuri.

Caracteristici dorite ale protocolului: convegenta, optimalitate, complexitate redusa, robustete,

extensibilitate, echitate, fiabilitate, etc. (unele sunt contradictorii)

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S2

S1

R4

R3R2

R1 R5

RP

S2

S1

R4

R3R2

R1 R5

S2

S1

R4

R3R2

R1 R5

Unidirectional treeOne tree per source

S1 rooted tree (SPT)S2 rooted tree (SPT)

Optimised for source specific mccommunication

Unidirectional Shared(by all sources) tree

Components:Shared tree

Data path S1RP

Data path S2 RP

Bidirectional Shared TreeDistribution of S1 data

Distribution of S2 data

Figura 3-4 Tipuri de arbori

3.2 Algoritmi de cautare a celui mai scurt drum

- Retea- echiv cu un graf

- Caut drumul cel mai scurt intre doua noduri d.p.d.v cost

- Cost cu : nr. Noduri/dist./t. intarziere/ inversul benzii

i

k1

k2

Fig 1. Cautarea drumului minim intre nodurile I si j

dij min = min { dik+ dkj}k

unde k este un nod oarecare prin careexista drum spre nodul j.

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3.2.1 Algoritmul Dijkstra (centralizat)

Se cauta toate drumurile minime de la un nod sursa catre toate celelalte. Rezulta un arbore cu

radacina in nodul sursa. Se repeta alg. ptr. fiecare nod al retelei.

- date: lista nodurilor, lista interconectarilor, costurile link-urilor.

Alg.: Fie un nod A

Se construieste arborele drumurilor minime cu radacina in A extinzandu-l succesiv pana ce

toate nodurile apartin arborelui.

Notatii:

Fie v, w, noduri ale grafului

D(v) = distanta intre A si nodul v ( suma costurilor pe un drum intre A si v)

l (v, w) = distanta ( costul arcului) intre v si w

N = multimea nodurilor din arbore

1. Initializare:

N={A}

Ptr. v N se eticheteaza nodul v astfel : v(A,D(v)), unde A este nodul din arbore prin care

v are acces spre A.

In particular avem: v(A, D(v)) pentru nodurile legate direct la A

v(-, ) pentru nodurile care nu sunt legate direct la A

2. Se completeaza arborele cu un nod nou , astfel:

- se cauta w N, pentru care D(w) = minim

- N= N {w}se include in arbore nodul w- Se reeticheteaza fiecare vecin v (care nu apartine lui N) al lui w, prin recalcularea dist. la

A tinand seama de noul nod inclus in arbore , astfel:

D(v) = min{ D(v), D(w) + l(w, v)},

v N, v V(w)

unde V(w) este multimea vecinilor lui w. Ca urmare a reetichetarii, A din eticheta v(A,D(v)), varamane A sau va deveni w daca prin w se obtine un nou drum mai scurt spre A.

3. Se repeta etapa 2 pana ce toate nodurile apartin arborelui.

Exemplu:

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A

B(A,1)

D(A,3)

C(A,6)

E(-,)

1 1

3

6

3

1

24

Initial: N={A}

A

B(A,1)

D(B,2)

C(D,4)

E(D,5)

1 1

3

6

3

1

24

Pas (2): N= {A,B,D}

Se adauga D

A

B(A,1)

D(B,2)

C(B,5)

E(-,)

1 1

3

6

3

1

2

4

Pas 1: N={A,B}

Se adauga B

= dist. recalculate

V(B) C (N)C (N)= complement al

lui N

A

B(A,1)

D(B,2)

C(D,4)

E(D,5)

1 1

3

6

3

1

24

Pas (3): N= {A,B,D,C}

Se adauga C

A

B(A,1)

D(B,2)

C(D,4)

E(D,5)

1 1

3

6

3

1

24

Pas (4): N= {A,B,D,C, E}Se adauga E

Arbore de drumuri minime

de la A la B,C,D,E

costuri

Fig.1.1 Exemplu de calcul pentru algoritmul Dijkstra

Arborele de rutare pentru nodul A va fi cel din tabelul de mai jos :

Destinatia Nodul urmator

B B

C B

D B

E B

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3.2.2 Algoritmul Ford (Fulkerson)

- cauta drumurile de cost minim

- nodul radacina ( fie A) este considerat ca destinatie

- rularea algoritmului este gata dupa etichetarea tuturor nodurilor cu dist. fata de A si cu

eticheta nodului urmator pe drumul minim catre A

- constructia tab. rutare = repetarea alg. pentru fiecare nod destinatie.

Eticheta are aceeasi forma ca la alg Dijkstra . Ex B(5, D) este eticheta nodului B care arata cadistanta pana la A este 5, via nodul vecin D

1. Initializare

Fie nodul A = destinatie, D(A) = 0.

Se eticheteaza toate celelelte noduri cu ( -, ).

1. Etichetarea tuturor nodurilor cu distantele minime pana la A

Pentru nod v A executa:

- actualizeaza distantele D(v) pana la destinatia A, pentru fiecare nod , prin utilizarea

valorilor curente D(w) ale tuturor vecinilor w ai lui v, adica pentru toti w V(v). Se faceatribuirea:

D(v) = min{D(w) + l(w,v)}

w V(v)

- se actualizeaza eticheta de nod cu nr. nodului vecin care minimizeaza expresia de

mai sus si cu noua distanta D(v).

2. Repeta etapa 2 pana cand nu mai apar modificari.

v

w

t

u

A

duA

dtA

dwA

lau

lat

law

Comparison:(lau + duA) < > (lat + dtA) < > (law + dwA)

Vv

Figure 3-1 Actualizarea distantelor lui v fata de A

Exempluproblema.

1.Sa se determine arborele drumurilor minime in raport cu nodul A ptr. reteaua din fig.

1. Sa se scrie tab de rutare din nodul A pentru host-urile Hi, I < > 1.

2. Folosind drumurile de lungime minima sa se aloce numere de circuite virtuale pentru

conexiunile ( solicitate temporal in ordinea data) H1 - H7, H3 - H7, H2 - H6, H1H6,H1H5.

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B

A

C

D F

G

E

H1

`

H3

`

H6

`

H7

`

H2

H4

12

1

2 2 3

4

4

8

3

7

H4

V( B)

Figure 3-2 Configuratia retelei. Nodul A este destinatie.

Lista etichetelor initiale

B C D E F G

(-, ) (-, ) (-, ) (-, ) (-, ) (-, )

Pasul 1.1 : v = B

Nod w D(w) l (v,w) D(w) + l (v,w) Noua eticheta

ptr. nodul B

A 0 1 1 (A, 1)

C 1

D 2

Lista etichetelor dupa pasul 1.1

B C D E F G

(A,1) (-, ) (-, ) (-, ) (-, ) (-, )

Pasul 1.2 : v = C


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ptr. nodul C

A 0 2 2 (A, 2)

B 1 1 2

D 3 *

F 3 *

G 2 *

* = se poate inlocui cu x ( nu conteaza)


B C D E F G

(A,1) (A,2) (-, ) (-, ) (-, ) (-, )

Pasul 1.3 : v = D


ptr. nodul D

B 1 2 3 (B,3)

C 2 3 5

G x


B C D E F G

(A,1) (A,2) (B,3) (-, ) (-, ) (-, )

Pasul 1.4 : v = E


ptr. nodul E

A 0 7 7 (A,7)

G x

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B C D E F G

(A,1) (A,2) (B,3) (A,7) (-, ) (-, )

Pasul 1.5 : v = F


ptr. nodul F

C 2 3 5 (C,5)

G x


B C D E F G

(A,1) (A,2) (B,3) (A,7) (C,5 ) (-, )

Pasul 1.6 : v = G

Nod w D(w) l (v,w) D(w) + l (v,w) Noua etichetaptr. nodul G

C 2 2 4 (C,4)

D 3 8 11

E 7 4 11

F 5 4 9


B C D E F G

(A,1) (A,2) (B,3) (A,7) (C,5) (C,4)

Repetand pasul doi se constata ca nu mai apar modificari.

Atentie: rezolvarea completa presupune si terminarea pasului 2 ( adica 2.12.6).

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B

A

C

D F

G

E

H1

H3

H6

H7

`

H2

H4

12

1

2 2 3

4

4

8

3

7

H4

Figure 3-3 Arborele drumurilor minime pana la nodul A

Tabelul de rutare pentru nodul A este :

Destinatia Ruta ( via) Cost

H2 B 1

H3 C 2

H4 B 3

H5 E 7

H6 C 5

H7 C 4

Algoritmul se repeta pentru fiecare nod pentru care se construieste tabelul de rutare.

3.3 IP Routing Protocols

3.3.1 Internet Protocol reminder

- connectionless style, RFC 791- official specification of IP

- best effort protocolno guarantees- problems for real time traffic

- if problems appearrejection of datagrams (IP-DGs)

- functions:

- segmentation / reassembly (segmentation at the input of

first subnetwork and reassembly only at the end destination

machine)- routinghop-by-hop principle

-error reporting

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IP services

- two service primitives : send( ), deliver( )

- primitive parameters:

- source and destination IP addresses ( IPa_src, IPa_dst)

-protocol ( recipient of IP-DGs)- type of serviceindicatorspecifies data treatment

- identifierused in combination with IPa_src, IPa_dstand

protocol field to uniquely identify data unit

- dont fragmentsegmentation indication

- time to livelife time of DGmeasured in network hops

- data lengthlength of data being transmitted

- option dataoption request by the IP user- securityallow a security label attached to IP-DG

- source routinglist of routers

- route recordingfield allocated to record the sequence of

routers

- stream identificationnames reserved used for stream

service

- time-stamping source IP entity and some or all intermediate routers add atimestamp ( precision - ms) to the data unit

- datadata to be transmitted

IP Service quality options

- precedenceeight level of importance

- reliabilitytwo levels (normal / high)

- delaytwo levels ( normal/high)

- throughput two levels ( normal/high)

IP Datagram format

- versionindicates version number

-Internet header length (IHL) in 32 bits words

(minimum IP-H20 octets)

- type of servicereliability, precedence, delay, throughput

- identifier( 16 bits)together with IPa_src, IPa_dstuniquely

identifies the IP-DG

- flags ( more bit, dont fragment bit)used in segmentation-fragment offset( measured in 64 bit units)used in segmentation

- time to live (TTL) measured in router hops

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0 4 8 16 31

Version IHL Type of service Total length ( in octets)

Identification Flags Fragment offset

Time to live (TTL) Protocol Header checksum

Source IP adress (x1.y1.z1.w1)

Destination IP adress (x2.y2.z2.w2)

Options

Information

20

oct.

Figure 3-4 IP datagram format

- protocolindicates the higher level protocol

- header checksum- error detecting code for header only

re-verified at each router (1 complement addition of all 16 bit words

in IP-H)

- options (variable) encodes the options requested by the user

-paddingto assure multiple of 32 bits

- data fieldinteger multiple of 32 bits, 65 535 octets

3.3.2 Principles of IP routing

- if source and destination are on same local network then IP-DG sent arrives directly to the

destination ( broadcast medium or serial line)

- if not, the IP-DG is sent to a router charged to forward the IP-DG (based on routing tables) (

to another router) up to the destination

- routing table consulted for each IP-DG

- routing protocols are executed to build the routing tables

- hop by hop routing principle

- one machine can be configured to function as a router also ( that is to retransmit the received

IP-DGs which are not addressed to itself)

one entry in the routing table (RT) :

-IPa_dst- destination IP address (machine addr. or network addr.)

- next hop router address or an address of a network directly

connected

- flags - indicates ifIPa_dstbelongs to a machine or a network, etc.

- interfacespecification where the IP_DG must be sent

IP forwarding operation

- search in RT (ActuallyFT) of an entry corresponding to:

- full destination address (if found then route to next hop

router or to I/F directly connected ( depending on flags)

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- or, destination network address - similar actions

- or default entry

UDP TCPnetstat

commandroute

command

routing

demon

packet for

this dest?

ICMP

IP process

options

forwarding

( compute

the next

hop)

Routing

table

Source routing

yes

Retransmission

(if valid)

no

update

redirection

Network interfaceIP layer

Figure 3-5 IP actions on the received datagrams

3.3.3 Network hierarchies

The current Internet is a decentralized collection of computer networks from all around the world.

Each of these networks is typically known as a domain or an autonomous system (AS)

AS = network or group of networks under a common routing policy, and managed by a single

authority.

Today, the Internet is basically the interconnection of more than 20,000 ASes [4].

Intradomain routing: Every one of these ASes usually uses one or more interior gateway protocols

(IGPs), such as Intermediate System to Intermediate System (IS-IS) or Open Shortest Path First

(OSPF), to exchange routing information within the AS.

Interdomain routing focuses on the exchange of routes to allow the transmission of packets between

different ASes.

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Figure 3-6 A simplified inter-domain scenario

When an AS is connected to multiple different ASes, it is referred to as a multihomedAS.

Types: single-homed, multi-homed, transit AS. Note a transit AS could be sometimes considered as

multi-homed stub AS. ( e.g. AS 2).

Todays Internet : hierarchy of transit ASes [5].This hierarchical structure is rooted in the two different types of relationships that could exist between

ASes

- customer-provider- peer-to-peer).

Thus, for each transit AS any directly connected AS is either a customer or peer.

Level 1: the top of this hierarchy we found the largest ISPs, (Tier-1 ISPs).

- There are about 20 Tier-1s at present which represents less than 0.1 percent of the total

number of ASes in the Internet

- Tier-1s are directly interconnected in almost a full mesh and compose the Internet core. In

the core all relationships between Tier-1s are peer-to-peer, so a Tier-1 is any ISP lacking

an upstream provider.

Second level of the hierarchy is composed ofTier-2 ISPs.- A Tier-2 is any transit AS that is a customer of one or more Tier-1 ISPs

- A representative example of a Tier-2 ISP is a national service provider. Tier-2 ISPs tend

to establish peer-to-peer relationships with other neighboring Tier-2s for both

economical and performance reasons (SLA-s can be negotiated)

- This is typically the case for geographically close Tier-2 ISPs that exchange large

amounts of traffic.

-

Tier-3 ISPs : those transit ASes in the hierarchy that are customers of one or more Tier-2 ISP, such

as regional ISPs within a country.

- Stub ASes are non-transit ASes that are customers of any ISP (Tier-1, Tier-2, or Tier-3)

- In Fig. 1-31 ISPs such as AS11, AS12, AS21, AS23, and AS31 would be classified

as Tier-2 ISPs, while AS22 represents a Tier-3 ISP.- An important corollary of this hierarchical structure is that the diameter of the Internet is

very small in terms of AS hops.

Single-homed

stub AS

Multi-homed

stub AS

Transit AS

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General definitions

Hierarchy: - backbone network, - autonomous systems, - networks, subnetworks, hosts

- Autonomous System (AS) ( Domain) logical portion of larger IP networks administeredby a single authority. The AS would normally comprise the internetwork within an

organization, and would be designated as such to allow communication over public IPnetworks with ASs belonging to other organizations. It is mandatory to register an

organization's internetwork as an AS in order to use these public IP services.

- Gateways (Routers): IGInterior Gateway( Router), EG - Exterior(Border) Gateway

- Protocols: IGP, EGP - Interior Gateway Protocol, Exterior Gateway Protocol (e.g.

Border Gateway Protocol- BGP)

- AS-s can be organised on more than one level ( nets, subnets, etc.)

- IP addressglobal address equivalent to NSAP addressesdifferent from Network Point ofAttachment (NPA) which depends on particular subnetwork mapping: IP_addr NPA

- routing based on IP_addr requires finding the NPA (MAC address) which corresponds

to IP_addr

- Adress Resolution Protocol (ARP) , Reverse Address Resolution Protocol (RARP) solve

the problem

Backbone net

EG

EG

EG

EG SN1

IG

IG IG

N2

SN1

N1 N3

AS1

EGP

IGPIGP

second level IG router

AS2

AS3

EGP

host

Figure 3-7 Generic hierarchical Internet topology

Protocol scopes

- ARP used in one network to find the NPA_dst address corresponding to IPa_dst

HiARP Hk

HiARP IGj ARP Hk

- IGP, EGP used between routers

IGiIGP IGjIGP EGk EGP EGn

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Demon Interior Gateway Protocol (IGP) Exterior Gateway Protocol EGP

HELLO RIP OSPF EGP BGP

routed V1

gated V.2 V1 V1

gated V.3 V1, V2 V2 V2, V3

Table 3-1 Routing protocols supported by routedand gateddaemons

[Note: In Unix and other computer multitasking operating systems, a daemon is a computer program

that runs in the background, rather than under the direct control of a user; they are usually initiated as

background processes. Typically daemons have names that end with the letter "d": for example,

syslogd, the daemon that handles the system log, or sshd, which handles incoming SSH connections.]

In TCP/IP software operating systems, routing protocols are often implemented using one of two

daemons:

Routed: Pronounced routeD. : basic routing daemon for interior routing supplied with the majorityof TCP/IP implementations. It uses the RIP protocol

GatedPronounced gate D. : more sophisticated daemon on UNIX-based systems for interior and exteriorrouting. It can support a number of additional protocols such as OSPF, BGP

In TCP/IP the routing protocols are implemented in the operating system.

3.3.4 Address Resolution Protocol (ARP), Reverse ARPRARP

-RFC 826ARP specifications

- ARP, RARP - integral part of IP

IP_addr

(32 bits)

NPA_addr

(e.g. MAC_addr 48 bits)

ARP

RARP

Figure 3-8 ARP and RARP actions

ARP

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driver

Ethernet

ARP

driver Ethernet

ARP

TCP

IP

driver

Ethernet

ARP

TCP

IP

FTPDNS

machine name

(1)

machine name

IP address (IP_a)

(0)

(2) setup connection

with IP addr = IP_a

(3) sendIP dg(IP_a) (conn-req)(4)

(5)

(6) (7) (8) send

IP dg(IP-a, MAC_a)

(conn-req)

ARP_req(IP_a)

source

(client)

destination

(server)

Ethernet LAN

Figure 3-9 Example of ARP role in sending IP datagrams

- ARP of a host maintains a table hostid/NPA address pairs for all hosts connected to this

network with which host communicates

- IP-DGs comes from upper layer, ARP table is consulted

- ifIPa_dstentry exists then NPA_addris red and a pointer to address of IP-DGs is passed

(together withNPA_addr) to SNDAP sublayer protocol

- if not, then anARP_reqt(IPa_src, NPA_src, IPa_dst) is broadcasted or sent to the default IG

- in the second case the ARP in IG relays theARP_requestto the destination host- the destination host replies withARP_reply(NPA_addr), using the

NPA_addrof source to return the result

- the source host stores the result ofARP_reply and sends IP-DG to SNDAP

- cache ARPincrease efficiency, limited life time of entries

- proxy ARP IGP responds on behalf and instead of some machines linked behind it ; thesource does not see the real configuration

RARP

- obtains the IP_addr associated to a given NPA_addr

- useful in diskless machines at start-up

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3.3.5 Interior Gateway Protocols

- function: finding the routing information within an AS

- distributed protocolsmessages between routers ( nodes)

- dynamic routing

-proactive/on-demand protocols

Distance Vector Algorithm (DVA) based protocols - examples

- most used: Routing Information Protocol (RIP)each node bases its routing decisionsonly on neighbours information on distances (one node does not know the whole domain

topology)

- AODV ( Adhoc on demand Distance vector protocol)used on WLANS- MANET

- DVMRPDistance Vector Multicast Routing Protocolextension to mcast

Link state Protcol

- Open Shortest Path First (OSPF)link-state algorithm - examples

- each node gets messages from neighbours ( info about links, costs) and

builds a network graph

- on this graph it determines the shortest path to the destination by applying

some shortest path algorithm (Dijkstra, Ford, etc.) using a given metric

- Optimized Link State Routing Protocol (OLSR)- used in MANET

- Multicast OSPF (MOSPF)extension of OSPF multicast

Control PlaneRouting

Protocols

Switch( bus, matrix,

etc.)Packets

.

.

I/F

I/F

Figure 3-10 Generic Router diagram

3.3.5.1 Routing Internet Protocol (RIP)

Distance vector-based protocol:

The distances in the tables are computed from information provided by neighbor routers.

Each router transmits its own distance vector table across the shared network.

The sequence of operations :

Each router is configured with an identifierand a costfor each of its network links. The cost is

normally fixed at 1, reflecting a single hop, but can reflect some other measurement taken for

the link such as the traffic, speed, etc.

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Each router initializes with a distance vector table containing zero for itself, one for directly

attached networks, and infinity for every other destination.

Each router periodically (typically every 30 seconds) transmits its distance vector table to

each of its neighbors. It can also transmit the table when a link first comes up or when the

table changes (event triggered updates).

Each router saves the most recent table it receives from each neighbor and uses the

information to calculate its own distance vector table (Ford distributed algorithm).

The total cost to each destination is calculated by adding the cost reported in a neighbor's

distance vector table to the cost of the link to that neighbor.

The distance vector table (the routing table) for the router is then created by taking the lowest

cost calculated for each destination

a

w

v

u

D

duD

dvD

dwD

lau

lav

law

Comparison:(lau + duD) < > (lav + dvD) < > (law + dwD)

Message : Routing table of w:

(D, dWD)

Figure 3-11 Principle of RIP distance vector based counting of costs

- RFC 1058/1988official specification of RIP

- very used as a simple distributed intra-domain routing protocol

- RIP messages between nodes are transported in UDP datagrams (Non reliable):

IP-H, UDP-H, RIP_message = IP-DG format for RIP

Destination Next hop Distance Timers Flags

NetB Router 2 3 (in hop count) t1, t2, t3 x,y

NetA Router1 5 t1, t2, t3 x,y

Table 3-2 Typical RIP Routing Table

Note: in RIP the RT is the same as Forwarding Table

- RIP maintains only the best route to a destination

- messages exchanged at request or periodically ( e.g. 30 sec)- newer implementations- event triggered updates

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RIP packet format

- command - specifies a request or response message

- version number- specifies RIP implementation

- up to 25 routes having the format:

- address family IDshows the address family used (e.g. IP_addr)

- addressIP destination address (4 octets),- metricHop count ( how many routers) up to the destination

- a RIP message can contain the whole or part of the source RT

- update timer30 sec ( each router sends its RT to neighbours each 30 sec)

- route invalid timerwhen expires a route is marked invalid ( e.g. 90 sec), neighbours arenotified of this fact

- route flush timerwhen expires route is erased from RT

Figure 3-12 RIP packet format

Stability features

-Hop count limit( < 16) prevents count to infinity routing loops

-Hold downrouters hold down any changes reported by neighbours regarding a route which

was just removed route (prevent oscillations)

- Split horizonavoids loops

- Poison reverse updates increasing metric indicates loops; therefore a node detecting thissends a reverse messages to remove that route

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R1Net A

directions to which R2 may forward

and advertiseits route to NetA via R1

R2

(Net A, cost)

Figure 3-13 Split horizon-prevent loops between adjacent routers

RIP Extensions

RIP-2RIP-2 is a draft standard protocol. Its status is elective (RFC 1723).

RIP-2 extends RIP-1. It is less powerful than OSPF but it has the advantages of easy implementation

and lower overheads.It can replace for RIP that can be used on small to medium-sized networks

- can be employed in the presence of variable subnetting Classless Inter-Domain Routing(CIDR)

- can interoperate with RIP-1

RIPng for IPv6: intended to allow routers to exchange information for computing routes

through an IPv6-based network (RFC2080 )

3.3.5.2 Ad hoc On-Demand Distance Vector (AODV)AODV RFC 3561- is originally a reactive ( i.e. on demand) distance-vector routing protocol for

mobile ad hoc networks (MANETs) and other wireless ad-hoc networks. AODV is capable of bothunicast and multicast routing. The usual metric is hop count.

Other usage: in mesh networks.

WLANS and Mesh networks

- Technology: 802.11, 802.16, 802.15

Figure 3-14 WLANs and Meshnetworks: a) WLAN-infrastructure; b) WLAN-ad hoc; c)

mixedmode; d) mesh network.

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