Advanced Network Architectures Lecture 1...6 Lecture 01 - Introduction to main network architecture...

Lecture 1

Overview and logistics

Introduction to main network architecture principles

Dimitrios Klonidis – 18/02/2019

Advanced Network Architectures

2 Lecture 01 - Introduction to main network architecture principles

Outline


Overview and logistics


Network Architecture

▪Network:‒ Describes the connectivity among users

• from the physical medium up to the application layer

‒ … but also today connectivity among machines, sensors, …‒ … and also in near future connectivity among programs

▪ Architecture:• A very broad term…

‒ Refers to the overall design and interconnectivity approach, and typically includes:• Topology of the network• Technologies (i.e. protocols)• Interworking issues

Note:In computer science courses the term Network architecture typically refers to data network principles only (Ethernet, IP, TCP, etc.)


Course objective

▪ To provide a good understanding of the network architecture principles and a view of the modern and future trends in networking.

▪ In particular:‒ The established data network and broadband network technologies‒ The current state of the art in access, metro, core, datacenter networks‒ The future trends driven by the advances in optical networking and hybrid

wireless-optical networks‒ The network transformation trends for the future and the effects that other

scientific topics (i.e. AI, big data, cloud computing) have.

▪ To present different broadband technologies and related architectures and learn about their basics in design and implementation

▪ Familiarize with some of the most important up-to-date and emerging networking standards and developments

▪ Develop the ability to explore advanced topics and the driving forces in network and protocol design, and telecommunication technologies.


My objectives

▪ To understand the different technologies‒ What each technology offers‒ At which part of the network it is applied ‒ How they relate with different applications‒ How they interwork with each other

▪ To examine each technology in more detail (from the networking point of view) and understand the basic operating and design principles.

▪ To provide you the ability to explore advanced topics in new networking technologies and protocol design.


Evaluation

▪… Under consideration‒ To be shortly confirmed within next two lectures

▪ 60% - 80% Exam

▪ 20% - 30% Quizzes (1 mid term or 2 shorter)

▪ or/and short assignment


Communication

▪ By email: [email protected]

▪ By skype upon arrangement

▪ Before lecture upon arrangement

mailto:[email protected]


Suggested textbooks

▪ Important note‒ Textbooks are meant only to provide you only additional information on

various topics or a more complete way to familiarize with certain topics.‒ The slides and the additional material (examples, articles, references) will

provide all the required information for the final evaluation.


Course Outline

▪ Network architecture principles‒ Main concepts

• Narrowband – Broadband• Packet switching – Circuit switching• Edge – Access – Core • Datagram – Virtual Circuits

‒ Networking concepts• Network structure• Network functions (traffic management, resource allocation, error

control, compression, encryption)

‒ Multiplexing‒ Network Layering and Protocols

▪ Internet IP/TCP‒ Overview

• IP, Addressing, Subnetting, IPv6, NAT, TCP, flow control, congestion control, ICMP


Course Outline

▪ Traffic management‒ Network performance

• Throughput, Delay, Jitter• Variable/Fixed length packets

‒ Resource allocation‒ Queuing disciplines

• FiFo format• Fairness in queuing

‒ Flow Control• Throughput vs. Traffic load• TCP control for flows

‒ Congestion control• End-to-end congestion control • Network assign congestion control

▪ Traffic engineering‒ QoS and scheduling techniques ‒ Monitoring and adjusting network resources


Course Outline

▪ MPLS, GMPLS ‒ IP over ATM‒ Adding QoS in IP‒ Control plane and MPLS‒ Multi-Protocol Label Switching (MPLS) control

• Main concepts• Label switch routers (LSR)• Extensions to MPλS, and GMPLS

▪ Software Defined Networking‒ Main principles‒ ETSI MANO architecture

▪ Broadband for the metro/core network ‒ PDH ‒ SDH/SONET‒ OTN (Optical Transport Networks)

• Details and architectures


Course Outline

▪ Broadband for the access network‒ Access network principles and chracteristics

‒ Ethernet ‒ xDSL schemes (ADSL, VDSL)

‒ Passive Optical Netwotks (PONs)• FTTx (Fibre-To-The- home, curb)

▪ 5G networking‒ Main trends‒ Hybrid fixed wireless architectures

▪ Data Center Interconnects‒ DCI architectures‒ Scalability issues‒ Distributed DCI concepts


Network growth drivers and design criteria


Network growth

▪ Data volume increase → Network capacity increase

▪ New data types (apps) → Higher traffic complexity, network control

▪ New connectivity types → Capacity increase, traffic complexity, control

▪ Extended coverage → Network infrastructure growth

▪ Reliability → New technologies, Higher capacity

▪ Security → New technologies and designs

▪ …

Data volume

New Apps

New devices

Infrastructure, CapacityComplexityTechnologies (switching, transport)

Control and management

Ap

ps

and

Ser

vice

s


Data and Services evolution

▪Many reports, graphs and predictions in the web‒ Dedicated consultancy companies for market growth forecast

that are typically based on technology penetration and data volume increase predictions• Deloitte, Dell’Oro, Ovum, IHS Markit, …

▪ Two major open data growth reports:‒ Cisco Visual Networking Index

• Latest release: Nov 2018

‒ Ericsson Mobility report• Latest release: Nov 2018

https://www.ericsson.com/en/mobility-report/reports/november-2018

https://www.cisco.com/c/en/us/solutions/collateral/service-provider/visual-networking-index-vni/white-paper-c11-741490.html#_Toc529314173



Ericsson Mobility report



Source: 5G Infrastructure Association: 5G Empowering vertical industries. White Paper, 2016,


Towards broadband networking

▪ Doing everything faster

▪ Doing everything better‒ Stereo sound

‒ High quality video – HDTV – 3D TV

‒ Unlimited downloads and uploads

▪ Maintaining reliability & availability

▪ Achieving convergence (i.e. bring services and technologies together)

‒ “Seamless” services over fixed & mobile

‒ Supporting mobility (of users and equipments)

‒ Minimising spectrum use reducing cost

Broadband


Aspects of broadband networks

▪ With respect o Physical performance‒ High-capacity transmission links

• Extended use of optical links in fixed infrastructures • Move towards mmWave and THz communications in wireless

‒ High-speed and performance switching and multiplexing• System on chip for ultra high capacity switching (towards 32Tb/s)

‒ High-speed signal-processing technologies‒ Allowing real time processing and transmission improvement,

▪ With respect to Enhanced Services‒ Efficient software application processing‒ High integration of different types of data: voice, audio, video, text,

graphics, images‒ QoS requirements (throughput, delay, delay variation, packet loss)‒ Enable for e-services (eHealth, eGovernment, eLearning, eCommerce,

telecommuting)‒ Affordable residential access services


Network structure: The big picture

22


Network structure

▪ As message sent from user in the network undergoes different types of networks with different characteristics and requirements. In general divided into:

‒ Access (LAN)‒ Metro (MAN‒ Global – wide (GAN, WAN)

▪ Different technologies also set different characteristics and requirements that lead to the use of different communication protocols.

‒ Circuit switching in the metro-core‒ Packet switching in the access-metro

▪ Infrastructure (network elements):‒ physical medium‒ switching components‒ control layer


Network expansion drivers

▪ Access is driving growth and expansion of broadband networks‒ High capacity @ access ➔ even higher capacity @ metro, core‒ New models for bringing information at metro level. Then keep core for

large volume data synchronization and update

▪ e-services and pervasive applications ➔ high commercialization of every-day life!

▪ Video and audio streaming (VoD, VoIP, P2P, etc). ‒ Vast number of services that enable high capacity at access

▪ Service integration and technology convergence

▪ Competitive pricing

▪ Always-on service and personalization trends


Main Network design aspects

▪ Switching: ‒ circuit vs. packet switching‒ store-and-forward, ‒ multiple access

▪ Connectivity mode: ‒ shared links (multiple access) vs. direct (point-to-point) links

▪ Multiplexing: ‒ statistical, TDM, FDM, WDM, scheduling

▪ Addressing: ‒ identifying network components by assigning unique numbers.

▪ Routing: ‒ determine source-destination packet delivery. Multicasting.

▪ Internetworking: ‒ way of connecting heterogeneous or similar nets (using, e.g., gateways,

switches) and allowing protocol interoperability.


Main Network design aspects (ctd.)

▪ Traffic Management: ‒ flow control: traffic regulation, resource reservation‒ congestion control: monitoring, prevention, policing, priority control‒ QoS: transmission quality guarantees and enforcement

▪ Resource Allocation ‒ Handling of physical resources (bandwidth, fibre, wavelength channels)‒ Handling of processing resources (memory, CPU)

▪ Error Control: ‒ guarantee end-to-end delivery and reliability.‒ error-detection and correction (FEC), ‒ coding

▪ Feedback Control: ‒ close-loop (implicit/explicit)‒ ACKs and retransmissions

▪ Compression, encryption

27 Lecture 01 - Introduction to main network architecture principles 27

Network criteria

To be considered effective and efficient, a network must meet a number of criteria. The most important are:

DATA COMMUNICATIONNETWORK CRITERIA

PERFORMANCE RELIABILITY SECURITY

• Number of users• Transmission medium• Hardware• Software

• Frequency of failure• Recovery time after failure• Catastrophe

• Unauthorized Access• Viruses


Multiplexing – Channel Sharing


Allow multiple channels/users share link capacity: multiplexing.

Very common in long-haul networks where multiple traffic streams are combined over high-speed lines (trunks).

Multiplexer (MUX): groups independent traffic streams over the same link

Demultiplexer (DEMUX): separates a single stream into individual traffic streams

T1

T3

T1

MU

XD

EM

UX

N inputs N outputsN channels

Multiplexing


Frequency-Division Multiplexing (FDM): each channel is allocated a particular portion of the bandwidth (called bands).

All (modulated) signals are carried simultaneously on different frequencies.

CH 1 CH 2 CH 3 CH 4

BW (Hz)

Examples: Radio, TV, GSM (partially)

Multiplexing techniques – FDM


Time-Division Multiplexing (TDM): time-axis is divided up into timeslots.

Each channel is allowed to be carried during pre-assigned timeslots only.

Also called synchronous TDM

Examples: SDH/SONET, GSM (partially)

Time

1 2 3 4 1 2 3 4 . . .Usr 1 U2 U3 U4 U1 U2 U3 U4

firstcycle

secondcycle

Remark: Simple to implement and widely used in broadband telecomms,

but inefficient as empty slots exists when no data are transmitted

Multiplexing techniques – TDM


Statistical Time-Division Multiplexing (STDM): Each timeslot is allocated on a demand basis (dynamically).

Also called asynchronous or intelligent TDM

Examples: ATM

Remark: Improved performance, but it requires buffering when aggregate input load exceeds link capacity.

Time

1 2 3 4 1 2 3 4 . . .Usr 1 U2 U1 U4 U3 U2 U3 U1

firstcycle

secondcycle

Multiplexing techniques – STDM


Wavelength Division Multiplexing (WDM): Used in optical communications.

The same as FDM but we refer to the wavelength rather than the signal frequency.

Note: wavelength λ is the distance occupied by a signal cycle. If v is the signal’s velocity and f its frequency then λ•f = v. where here v = c (the speed of light, 3e8 m/sec).

WDM is used only in optical communications and is a standard by itself.Channel spacing by 100GHz (or ~0.8nm) ➔ 150 λ-channels over S,C,L bands

Dense WDM (DWDM) the newest standard that doubles the channels by placing the closer in the optical spectrum.

Channel spacing by 50GHz (or ~0.4nm) ➔ 300 λ-channels over S,C,L bands

800 1000 1200 1400 1600 1800

1.0

2.0

3.0

Loss

(dB/km)

Wavelength (nm)

usable bw

800 1000 1200 1400 1600 1800

1.0

2.0

3.0

Loss

(dB/km)

Wavelength (nm)

usable bw Areas of operation with low attenuation

Multiplexing techniques – WDM


Packet and Circuit switching


Network Taxonomy

▪ Circuit-switched networks: wired, wireless telephony.

▪ Packet-switched networks: Internet.

Telecommunicationnetworks

Circuit-switchednetworks

FDM TDM

Packet-switchednetworks

Networkswith VCs

DatagramNetworks


Circuit switching

Switching method used in telephone networks.

A fixed path (circuit) is established.

A call requires explicit end-to-end connection set-up and tear-down phases.

Information rate is guaranteed.

Simple addressing and routing (developed hierarchically -numbering).

Reliable (most of the time or 99.999%).

S D

Source DestinationS

S S

S


Circuit switching characteristics

▪ Dedicated communication path between two stations

▪ Three phases‒ Establish

‒ Transfer

‒ Disconnect

▪ Must have switching capacity and channel capacity to establish connection

▪ Must have intelligence to work out routing – (signaling)


Circuit switching characteristics

▪ Digital Switch‒ Provide transparent signal

path between devices

▪ Network Interface

▪ Control Unit‒ Establish connections

• Generally on demand• Handle and acknowledge

requests• Determine if destination

is free• construct path

‒ Maintain connection‒ Disconnect


Packet switching characteristics

▪ Packets from different sources are interleaved.▪ Efficient use of resources (since they are used on a

demand): statistical multiplexing. ‒ Nobody reserves a lane on a freeway!

▪ Store-and-forward: intermediate nodes (e.g., routers) store (buffer) incoming packets, process them and forward them to the appropriate outgoing link.

A

B

C

D

aa

a

b bb

b a ab b b

aaa

bbb


• each end-end data stream

divided into packets

• user A, B packets share

network resources

• each packet uses full link

bandwidth

• resources used as needed

• resource contention:

• aggregate resource demand

can exceed amount

available

• congestion: packets queue,

wait for link use

• store and forward: packets

move one hop at a time

– Node receives complete packet

before forwarding

Packet switching characteristics ctd.


Principle of packet multiplexing

▪ Sequence of A & B packets does not have fixed pattern ➔ statistical multiplexing.• Note: In TDM each host gets same slot in revolving TDM frame.


Statistical multiplexing

▪ Packet multiplexing evens out bursty traffic.

▪ Due to the multiplexing gain egress link capacity need not be the aggregate of the ingress link capacities.

▪ If instantaneous sum of ingress flow rates exceed that of egress link capacity packets will be dropped.


• 1 Mb/s link

• each user: – 100 kb/s when “active”

– active 10% of time

• circuit-switching: – 10 users

• packet switching: – with 35 users, probability is

less than .0004

Packet switching allows more users to use network!

N users

1 Mbps link

Packet vs. Circuit switching - Example


Packet vs. Circuit switching

▪ Packet Switching is great for bursty data‒ resource sharing

‒ simpler, no call setup

▪ …but … Excessive congestion: packet delay and loss‒ protocols needed for reliable data transfer, congestion control

▪ Q: How to provide circuit-like behavior over packet switched network?

‒ data rate / delay guarantees needed for audio/video apps

‒ many approaches, ongoing research

44

➔ Is packet switching a “slam dunk winner?”


Packet switching – Routing types

▪ Goal: move packets through routers from source to destination

‒ several path selection (i.e. routing) algorithms

▪ Datagram network (routing): ‒ destination address in packet determines next hop

‒ routes may change during session

‒ analogy: driving, asking directions

▪ Virtual-Circuit network (switching): ‒ each packet carries tag (virtual circuit ID), tag determines next hop

‒ fixed path determined at call setup time, remains fixed thru call

‒ routers maintain per-call state


Packet switching – Datagram

▪ Information is divided into chunks (bursts) of data

▪ Packet switching is great for bursty data (i.e. computer data)‒ resource sharing‒ simpler, no call setup

▪ Excessive congestion (reliability): packet delay and loss‒ protocols needed for reliable data transfer, congestion control

▪ How to provide circuit-like behavior?‒ bandwidth guarantees needed for audio/video apps‒ some approaches: e.g., flow-based switching


Packet switching – Datagram

•Each packet treated independently

•Packets can take any practical route

•Packets may arrive out of order

•Packets may go missing

•Up to receiver to re-order packets and recover from missing packets


Packet switching – Virtual Circuit

▪ “Source-to-destination path behaves much like telephone circuit/channel”, full-duplex logical channels that are called VCs

‒ performance-wise‒ network actions along source-to-dest path

▪ Call setup, teardown for each call before data can flow

▪ Each packet carries VC identifier (not destination host address)

▪ Every router on source-dest path maintains “state” for each passing connection

▪ Link, router resources (bandwidth, buffers) may be allocated to VC


Packet switching – Virtual Circuit

•Preplanned route established before any packets sent

•Call request and call accept packets establish connection (handshake)

•Each packet contains a virtual circuit identifier instead of destination address

•No routing decisions required for each packet

•Clear request to drop circuit

•Not a dedicated path


Datagram vs Virtual circuit

▪ Common for both cases‒ Data transmitted in small packets

• Longer messages split into series of packets• Each packet contains a portion of user data plus some control info

‒ Control info• Routing (addressing) info

‒ Packets are received, stored briefly (buffered) and past on to the next node• Store and forward

▪ Virtual circuits‒ Network can provide sequencing and error control‒ Packets are forwarded more quickly

• No routing decisions to make

‒ Less robust• Loss of a node looses all circuits through that node

▪ Datagram‒ No call setup phase

• Better if few packets

‒ More flexible• Routing can be used to avoid congested parts of the network

‒ No packet delivery guarantees (best-effort)‒ Slower (use of look up routing table)

Advanced Network Architectures Lecture 1...6 Lecture 01 - Introduction to main network architecture...

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