Advanced Computer Networks - A. Duda

Introduction

Course goals

Advanced Computer Networks

 Advanced topics in networking   

cross-layer vision advanced functionalities design, management

 Organization 

Introduction

 

Prof. Andrzej Duda [email protected]

36 h course, 18h networking lab demos, exercises, questions, homework slides are not exhaustive - you must take notes and ask questions!

 Your team  

course: A. Duda lab: M. Heusse, S. Viardot

http://duda.imag.fr 1

2

Networking lab

Contents

 Important part of the course

 Introduction

 

perform required operations, write lab reports cannot be repeated 



grade < 8, you repeat your year!



 Goals  

 

VLANs and bridges, spanning tree protocol

 Interconnection Layer 3

acquire practical knowledge use Zebra as a router emulator

 

 Rooms D200 and D201: 

network architectures

 Interconnection Layer 2

    

80 PCs with multiple network interfaces network equipement: hubs, switches, routers isolated from the rest of the network

IPv6 Routing (RIP, OSPF, BGP)

Congestion control Quality of service MPLS, multicast Mobility Network management

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Course support

Overview

 Web site 

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 Network architectures

http://duda.imag.fr/3at

 L. Toutain "Réseaux locaux et Internet", 3me édition, Hermes, 2003  C. Huitema "Le routage dans l'Internet", Eyrolles, 1995.  R. Perlman "Interconnexions : ponts et routeurs", Addison-Wesley, 1994.  Gisèle Cizault "IPv6", O'Reilly 2001.



protocol architectures



interconnection structure



related protocols







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how entities cooperate? which entities are connected? how and where different functionalities are implemented?

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Introduction

Layered Protocol Stack  Managing complexity

Introduction: network structure, architecture and protocols



a layer corresponds to an independent module (protocol entity)

 A layer supports   

common data format - PDU (Protocol Data Unit) rules of cooperation: peer-peer procedures service interface: SAP (Service Access Point)

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Protocol Architecture

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Protocol architecture

 Protocol entity 

provides a set of services, eg. 

  

data

data multiplexing/demultiplexing construction/analysis of PDUs execution of procedures

SAP



multiplexing

layer n

header: control functions opaque data

SAP Protocol entity layer n PDU

PDU

 Procedures 

demultiplexing procedures

Protocol entity

 Protocol unit (PDU) 

data

connect, send

Lower layer protocols

actions to perform protocol functions: eg. lost packet retransmission

layer n-1

layer n-1

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Internet design principles

Internet protocol stack

 Cerf and Kahn’s internetworking principles:    

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 Application: supporting network applications

minimalism, autonomy - no internal changes required to interconnect networks best effort service model stateless routers decentralized control



 Transport: host-host data transfer 

 define today’s Internet architecture

TCP, UDP

 Network: routing of datagrams from source to destination 

IP

 Link: data transfer between neighboring network elements 

Application

FTP, SMTP, HTTP, OSPF, RIP Transport Network Link Physical

PPP, Ethernet

 Physical: bits “on the wire” 11

12

2

Introduction

ATM protocol stack  Application: native applications, other protocols 

SSCOP

 Adaptation: adapt the ATM layer to different types of applications  

 Management: e.g. construct forwarding tables

Application

LAN Emulation, IP, Signaling

 Transport: host-host data transfer 

LAN stack

circuit emulation, real-time data AAL5 suitable for IP traffic



Transport

 LLC: multiplex different protocols

Adaptation



Management

SNAP: Spanning Tree protocol IP, IPX, SNAP

LLC Data-link MAC

 MAC: medium access

ATM



Physical

802.3 (Ethernet), 802.4 (Token Ring), 802.5 (Token Bus), 802.11 (Wi-Fi)

Physical

 Physical: bits “on the wire”

 ATM: cell switching over virtual circuits  Physical: bits “on the wire” 13

Network architecture

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Interconnection structure - layer 2

 Logical structure 

interconnected entities

 Protocol architecture 

how entities cooperate



switch (bridge)

interconnection layer 2

 Related protocols different functionalities

VLAN

host

15

Interconnection at layer 2

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Protocol architecture

 Switches (bridges)   

interconnect hosts logically separate groups of hosts (VLANs) managed by one entity

 Type of the network 

 





Transport

3

Network

1

LLC MAC Physical

host

flat address space forwarding tables: one entry per host works if no loops 

Application

2

broadcast

 Forwarding based on MAC address 

5 4

L2 PDU (LLC Frame) L2 PDU (MAC Frame)

LLC MAC Physical

switch (bridge)

 Switches are layer 2 intermediate systems  Transparent forwarding  Management protocols (Spanning Tree, VLAN)

careful management Spanning Tree protocol

not scalable 17

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3

Introduction

Protocols

Interconnection structure - layer 3 network

data IP

router

management interconnection layer 3

SNAP

Ethernet v2

data-link

LLC

802.3

Physical layer

switch (bridge)

subnet 2 subnetwork 1

subnet 3 VLAN

host 19

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Interconnection at layer 3

Protocol architecture

 Routers   

interconnect subnetworks logically separate groups of hosts managed by one entity

 Forwarding based on IP address    

5

Application

4

Transport

3

Network LLC

2

structured address space routing tables: aggregation of entries works if no loops - routing protocols (IGP - Internal Routing Protocols) scalable inside one administrative domain

L3 PDU (IP packet)

MAC Physical

1

host

LLC L2 PDU (MAC Frame)

MAC Physical

Application

5

Transport

4

Network

3

LLC L2 PDU (MAC Frame)

switch (bridge)

MAC Physical

2 1

router

 Routers are layer 3 intermediate systems  Explicit forwarding 

host has to know the address of the first router

 Management protocols (control, routing, configuration) 21

configuration

DNS

routing

DHCP

RIP

UDP

TCP control

groups

ICMP

IGMP

IP

address resolution

ARP

Ethernet v2

network

naming

data-link

routing

OSPF

Autonomous systems transport application

Protocols

22

23

border router

autonomous system

internal router

interconnection layer 3

switch (bridge)

subnetwork

interconnection layer 2

VLAN

host 24

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Introduction

Long-haul links

Protocol architecture

 Fiber at physical layer (SONET/SDH) 

Dense Wave Division Multiplexing (DWDM) 

one color of the light λ

 

ATM

ATM Frame Relay POS (Packet over SONET/SDH)

SDH DWDM λ

AAL5 ATM cell

router

 Type of the network 

NBMA (Non Broadcast Multiple Access) or point-to-point

IP

 Complex protocol hierarchies 

IP

AAL5

 Different technologies 

L3 PDU (IP packet)

IP

PPP SDH DWDM λ

IP over ATM

ATM SDH DWDM λ

ATM switch L3 PDU (IP packet) L2 PDU (PPP frame)

router

ATM cell

ATM SDH DWDM λ

router

IP PPP SDH DWDM λ

router

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26

Interconnection of AS

Internet

 Border routers

autonomous system



NAP, GIX, IXP

interconnect AS

 NAP or GIX, or IXP 

exchange of traffic - peering

 Route construction  

subnetworks

 

border router

based on the path through a series of AS based on administrative policies routing tables: aggregation of entries works if no loops and at least one route - routing protocols (EGP - External Routing Protocols)

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Residential access transport application

Protocols

28

routing

BGP

TCP

address resolution

IP

ARP

Ethernet v2

data-link

ICMP

network

control

29

router

interconnection layer 3

modem POTS (phone network)

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5

Introduction

Residential access

Protocol architecture

 Modem 

connects a host to the first router

 Point-to-point encapsulation (PPP)    

activate a connection authenticate the user negotiate network address multiplex different protocols (IP, IPX)

5

Application

4

Transport

3

Network

2

PPP

1

Physical

L3 PDU (IP packet)

L2 PDU (PPP Frame)

host

Application

5

Transport

4

Network

3

PPP

2

Physical

1

router

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Residential access network

Protocols IP header compression

CHAP

router

NCP LCP

PPP

ATM network

negociation

data Physical layer

33

ATU-R ADSL modem/bridge/router

Protocol architecture L3 PDU (IP packet)

IP

ADSL

ADSL modem

ATM ADSL/SDH

DSLAM

ATM cell

34

IP

L2 PDU (PPP frame)

PPPoA

PPPoA

AAL5

ATM

ATM

SDH

ADSL

router

AAL5 ATM cell

ATM ADSL/SDH

ADSL modem

 IP over ATM 

L3 PDU (IP packet)

IP

AAL5 ATM cell

DSLAM (ATU-C) DSL Access Multiplexer

Protocol architecture

IP

AAL5 ATM

ATM switch

interconnection layer 3

data-link

PAP

authentication

32

DSLAM

ATM cell

ATM SDH

router

 PPP over ATM (PPPoA)

requires fixed IP address



35

multiple users share ADSL link

36

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Introduction

Conclusion

Protocol architecture IP

IP

IP

PPPoE

PPPoE

PPPoE

Ethernet

Ethernet

 Complex architectures

L3 PDU (IP packet)



L2 PDU (PPP frame)

Ethernet



Rapid growth



No central control



Three level hierarchy

LLC/SNAP AAL5 ATM Physical

host

Physical

ADSL

ADSL bridge/router



ATM cell

ATM



ADSL/SDH

DSLAM 

 PPP over Ethernet (PPPoE) 

other types of networks used as data links

 Internet

host, subnetwork, autonomous system



manage complexity

Advances  

37

coherent development





multiple users share ADSL link

scalability

larger address space - IPv6 performance - quality of service, e.g. DiffServ security - Virtual Private Networks (VPN) 38

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