Network Architecture and Protocols: A Comprehensive Guide, Study notes of Computer Systems Networking and Telecommunications

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Introduction

Outline^ Network Architecture^ Networks^ Statistical Multiplexing^ Performance Metrics

ISO Architecture

End host ApplicationPresentationSessionTransport NetworkData linkPhysical

End host ApplicationPresentationSessionTransport NetworkData linkPhysical

NetworkData linkPhysical

NetworkData linkPhysical One or more nodes within the network

Layering

-^ Use abstractions to hide complexity •^ Abstraction naturally lead to layering •^ Alternative abstractions at each layer

Request/replychannel

Message streamchannel Application programs Host-to-host connectivity

Hardware

Protocols

-^ Building blocks of a network architecture •^ Each protocol object has two different interfaces^ –^

service interface

: operations on this protocol

-^ peer-to-peer interface

: messages exchanged with peer

-^ Term “protocol” is overloaded^ – specification of peer-to-peer interface^ – module that implements this interface

Protocol Machinery

-^ Protocol Graph^ – most peer-to-peer communication is indirect^ – peer-to-peer is direct only at hardware level

Digital Filelibraryapplicationapplication

Videoapplication RRP^

Host 1 MSP HHP

Digital Filelibraryapplicationapplication

Videoapplication RRP^

Host 2 MSP HHP

Machinery (cont)

-^ Multiplexing and Demultiplexing (demux key) •^ Encapsulation (header/body)

RRP^ DataHHP Applicationprogram

Applicationprogram

Host 1^

Host 2

Data RRP RRP Data HHP

Data RRP RRP^ Data HHP

Switched Networks

-^ A network can be defined recursively as...^ – two or more nodesconnected by a link, or - two or more networksconnected by two ormore nodes

Strategies for Network Design • Circuit switching

: carry bit streams

• original telephone network • Packet switching

: store-and-forward messages

• Internet Network Services offered: Connection-oriented, connection-less, reliable, unreliable

Multiplexing

-^ Time-Division Multiplexing (TDM) •^ Frequency-Division Multiplexing (FDM)

L1 L2 L

R1 R2 R

Switch 1

Switch 2

Statistical Multiplexing

-^ On-demand time-division •^ Schedule link on a per-packet basis •^ Packets from different sources interleaved on link •^ Buffer packets that are

contending

for the link

-^ Buffer (queue) overflow is called

congestion^ …

What Goes Wrong in the Network? • Bit-level errors (electrical interference) • Packet-level errors (congestion) • Link and node failures • Messages are delayed • Messages are deliver out-of-order • Third parties eavesdrop

Performance Metrics

-^ Bandwidth (throughput)^ –^

data transmitted per time unit – link versus end-to-end – notation^ • KB = 2

10 bytes

• Mbps = 10

6 bits per second

-^ Latency (delay)^ –^

time to send message from point A to point B – one-way versus round-trip time (RTT) – components^ Latency = Propagation + Transmit + Queue^ Propagation = Distance / c^ Transmit = Size / Bandwidth

Delay x Bandwidth Product

-^ Amount of data “in flight” or “in the pipe” •^ Example: 100ms

x^ 45Mbps = 560KB

Bandwidth

Delay