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IEX8175 RF Electronics

Avo Otstelekommunikatsiooni õppetool,

TTÜ raadio- ja sidetehnika inst.avo.ots@ttu.ee

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Network Engineering• The process concerned with optimally selecting topology and

bandwidth in a layer network, based on – (pro-active) traffic demands expected between any two locations in the network

and – (re-active) the actual traffic demand

• It is an inter layer network process• NwE process in each layer network

– advertises the nodes and their ports within the layer network– monitors the layer network and determines if/when a new (topological) link

should be added or an existing link should be modified or released, based on the network provider's policy

– determines best set of connections between ports in the layer network– requests those connections to be set up by its server layer networks; i.e.

generates outgoing calls for client connections• It is implemented by the (distributed) Network Engineering

Controllers (NEC) within the layer network

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Shared & Dedicated B W

Dedicated Bandwidth Circuits Shared Bandwidth Circuits

Mbp

s

Time

Dedicated Transport & Transfer Rate In Network

Actual Data Rate Usage vs. Time

Wasted Bandwidth

Mbp

s

Time

Multiple Data Customers in Shared Trunk Bandwidth

Sum of Aggregate BandwidthMuch Less Wasted Bandwidth

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Internet protocol• Provides best effort, connectionless packet delivery

– motivated by need to keep routers simple and by adaptibility to failure of network elements

– packets may be lost, out of order, or even duplicated– higher layer protocols must deal with these, if necessary

• RFCs 791, 950, 919, 922, and 2474.• Internet STD also includes:

– Internet Control Message Protocol (ICMP), RFC 792– Internet Group Management Protocol (IGMP), RFC 1112

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IP address

RNetwork

128.135.0.0

Network

128.140.0.0

H H

HH H

R = routerH = host

Interface Address is

128.135.10.2

Interface Address is

128.140.5.35

128.135.10.20 128.135.10.21

128.135.40.1

128.140.5.36

128.140.5.40

Address with host ID=all 0s refers to the network

Address with host ID=all 1s refers to a broadcast packet

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1

2

3

4

5

6

Node (switch or router)

Routing in Packet Networks

• Three possible (loopfree) routes from 1 to 6:– 1-3-6, 1-4-5-6, 1-2-5-6

• Which is “best”?– Min delay? Min hop? Max bandwidth? Min cost?

Max reliability?

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Packet Switch: Meet

1

2

N

1

2

N

• • •

• • •

• Inputs contain multiplexed flows from access muxs & other packet switches

• Flows demultiplexed at input, routed and/or forwarded to output ports

• Packets buffered, prioritized, and multiplexed on output lines

• • •

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Controller

1

2

3

N

Line card

Line card

Line card

Line card

Inte

rcon

nect

ion

fabr

ic

Line card

Line card

Line card

Line card

1

2

3

N

Input ports Output ports

Data path Control path (a)

…………Generic Packet Switch

“Unfolded” View of Switch• Ingress Line Cards

– Header processing– Demultiplexing– Routing in large switches

• Controller– Routing in small switches– Signalling & resource

allocation• Interconnection Fabric

– Transfer packets between line cards

• Egress Line Cards– Scheduling & priority– Multiplexing

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1

2

3

N

1

2

3

N

…

SharedMemory

QueueControl

Ingress Processing

ConnectionControl

…

Shared Memory Packet Switch

Output Buffering

Small switches can be built by reading/writing into shared memory

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1

2

3

N

1 2 3 N

Inputs

Outputs

(a) Input buffering

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3…

…

1

2

3

N

1 2 3 N

Inputs

Outputs

(b) Output buffering

…

…

Crossbar Switches

Large switches built from crossbar & multistage space switches Requires centralized controller/scheduler (who sends to whom

when) Can buffer at input, output, or both (performance vs complexity)

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UDP Multiplexing

• All UDP datagrams arriving to IP address B and destination port number n are delivered to the same process

...

UDP

IP

1 2 n ...

UDP

IP

1 2 n ...

UDP

IP

1 2 n

A B C

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Congestion Control• Buffers at intermediate routers between source and

destination may overflow

Router

R bpsPacket flows from

many sources

• Congestion occurs when total arrival rate from all packet flows exceeds R over a sustained period of time

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Phases of Congestion Behavior

1. Light traffic – Arrival Rate << R– Low delay– Can accommodate more

2. Knee (congestion onset)– Arrival rate approaches R – Delay increases rapidly– Throughput begins to saturate

3. Congestion collapse– Arrival rate > R– Large delays, packet loss– Useful application throughput

drops

Thro

ughp

ut (b

ps)

Del

ay (s

ec)

R

R

Arrival Rate

Arrival Rate

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Compute

Communicate Communicate

StoreCommunicate

Communications and computing

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Compute

Sense

Environment

ActCommunicate Communicate

StoreCommunicate

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Computation

Devices

Dynamical Systems

DevicesCommunication Communication

Control

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From• Software to/from human• Human in the loop

To• Software to Software• Full automation• Integrated control,

comms, computing• Closer to physical

substrateCompute

Communicate Communicate

StoreCommunicate

Computation

Devices

Dynamical Systems

Devices

Communication Communication

Control

• New capabilities & robustness• New vulnerabilities

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IPv4 >to>> IPv6• Expanded addressing capabilities• Header format simplification• Improved support for extensions and

options• Flow labelling capability• Authentication and privacy capabilities

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Basic Headers• IPv6 Header

• IPv4 Header

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Basic Headers• Fields

– Version (4 bits) – only field to keep same position and name

– Class (8 bits) – new field– Flow Label (20 bits) – new field– Payload Length (16 bits) – length of data, slightly

different from total length– Next Header (8 bits) – type of the next header, new idea– Hop Limit (8 bits) – was time-to-live, renamed– Source address (128 bits)– Destination address (128 bits)

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Basic Headers

• Simplifications– Fixed length of all fields, not like old options field –

IHL, or header length irrelevant– Remove Header Checksum – rely on checksums at

other layers– No hop-by-hop fragmentation – fragment offset

irrelevant – MTU discovery– Add extension headers – next header type (sort of

a protocol type, or replacement for options)– Basic Principle: Routers along the way should do

minimal processing

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Extension Headers

• Extension Header Types– Routing Header– Fragmentation Header– Hop-by-Hop Options Header– Destinations Options Header– Authentication Header– Encrypted Security Payload Header

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Lõpulingidhttp://www.ietf.org/rfc/rfc0791.txt?number=791

http://www.ietf.org/rfc/rfc2474.txt?number=2474

http://www.apple.com/airportextreme/specs.html

http://tools.ietf.org/html/rfc1924

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Linkshttp://www.ietf.org/rfc/rfc0791.txt?number=791

http://www.ietf.org/rfc/rfc2474.txt?number=2474

http://www.apple.com/airportextreme/specs.html

http://tools.ietf.org/html/rfc1924