18. may. 2006 1inf-3190: overview connecting networks by relays layer 1: repeater / hub layer 2:...

18. May. 2006 1 INF-3190: Overview

Connecting Networks by Relays Layer 1: Repeater / Hub Layer 2: Bridge / Switch

Self-learning bridges Spanning-tree algorithm

Source routing bridges Remote bridges

Layer 3: Router / Layer 3 Gateway / Intermediate Systems

Types Circuit switching Message switching Packet switching Virtual circuit switching

Services Connection-oriented

Connection setup QoS negotation Flow control

Connectionless Unreliable connections No flow control

Layer 4 - 5: Gateway / Protocol Converter

1

2

3

4

5

1

2

3

4

5

Physical layer

Data link layer

Network layer

Transport layer

Application layer

Repeater

Bridge

Router

Gateway

End system End systemIntermediatesystem

A

HC

H

B

H

E

H

F

H

D

H

IMP

Host

H 0 B 0H 1 E 0B 0 E 1H 2 B 1H 3 E 2H 4 E 3

A 0 C 0H 0 C 1H 1 A 0A 1 F 0H 2 F 1F 0 H 0

C 0 H 0C 1 H 1F 0 H 2F 1 H 3C 2 F 0

B 0 D 0B 1 D 1E 0 H 0E 1 D 2

A 0 F 0A 1 H 0A 2 C 0A 3 C 1

E 0 D 0B 0 D 1B 1 H 0D 0 B 0

A

B

C

D

E F

IN OUT

Virtual circuit setup


Internet Address resolution

ARP Use broadcast to

search for an IP address

ARP and routing RARP

Use broadcast to acquire own IP address

DHCP RARP improvement

H H H H H

@IP: 9.228.50.3@HW: 0xa3e

target

ARP Response

@IP: 9.228.50.3@HW: 0xa3e

@IP: 9.228.50.8@HW: 0xaa

source

H

target

ARP Request

@IP: 9.228.50.8@HW: 0xaa

@IP: 9.228.50.3@HW:

source

H H H H H

@IP: 9.228.50.3@HW: 0xa3e

target

RARP Response

@IP: 9.228.50.3@HW: 0xa3e

@IP: 9.228.50.8@HW: 0xaa

source

@IP: unknown@HW: 0xaa

target

RARP Request

@IP:@HW: 0xaa

@IP:@HW: 0xaa

source

H


Internet Routing

Routing tables Direct routing / interior

protocols Indirect routing /

exterior protocols Autonomous systems AS, AS backbone area,

area Router classes

AS boundary routers Backbone routers Area border routers Internal routers

EGP Open Shortest Path First

Link state routing Border Gateway Protocol

Distance path mechanism

Multicast routing Spanning tree

Link state routing Reverse path forwarding

with pruning Core-based tree Reverse path broadcast Truncated reverse path

broadcast


Routing Routing

define the route of packets through the network

Routing algorithm Defines on which outgoing

line an incoming packet will be transmitted

Desired properties Correctness Simplicity Robustness Stability Fairness Optimality

Optimality principle Sink trees

Route determination Datagram Virtual circuit

desti-nation

link

A 0B 3C 1D 4

RoutingProcess

Topology, link utilization, etc.information

Fills & Updates

Uses & Looks upData packets

Incominglines

Outgoinglines

ForwardingProcess

Routingtable

Router

Routing table andpacket forwarding


Routing Classes of routing

algorithm Non-adaptive

Non-adaptive shortest path routing

Flooding and selective flooding

Adaptive Centralized routing Isolated routing

Backward learning Distributed routing

Distance vector routing Count-to-infinity

problem Split-horizon

Link state routing Definitions of

distance Oscillations (route

flapping)

2

7

2

2

6

1 2

4

3

3

2

A

C (●,-)

D (●,-)

E (●,-)

F (●,-)

H (●,-)

B (2,A)

G (6,A)

A B CD

EF

GH

I J K L

A 0B 12C 25D 40E 14F 23G 18H 17I 21J 9K 24L 29

A243618277

2031200

112233

I2031198

301960

147

229

H2128362422403119221009

K

2820173018

0

15

8 A20 A

IHIIH

12 H10 I

-6 K

K

line

JA8

delay JI10

JH12

JK6

B C

E F

A D61

2

8

5 7

4 3A

Seq.Age

B C D E F

B 4E 5

Seq.AgeA 4C 2

Seq.AgeB 2D 3

Seq.AgeC 3F 7

Seq.AgeA 5C 1

Seq.AgeB 6D 7

F 6 E 1 F 8 E 8

Link S tate Packets:

Link State Routing

Distance VectorRouting

Dijkstra shortest path


Internet Internet Protocol Stack

IP Connectionless

datagram server Segmentation /

reassembly Route recording and

source routing IP networks

IPv4 Addressing Network classes Subnetworks

Netmasks to find subnetworks

CIDR Longest match prefix

to find subnetworks IPv4 vs IPv6

Data link andPhysical layer

Networklayer

Transportlayer

Applicationlayer

WANs

ATM

LLC & MAC

physical

LANs

MANs

IP+ ICMP+ ARP

TCP UDP

SMTP

HTTP

FTP

TE

LNET N

FS RTP

10 Network Host14 16

Subnet Host6 10

10000001000010000000011100000010e.g. address

129.8.7.2:11111111111111111111110000000000Subnet mask:

subnet addresswith netmask use either 129.8.4.0/255.255.252.0or 129.8.4.0/22

10000001000010000000010000000000Subnet address:

& &

Internet Protocols

IPv4 address, netmask andsubnet address


Transport Protocols & Network Services

Transport layer protocol

ISO Transport layer

protocol depends on the quality of the network layer service

ISO Network types A, B, C

Transport protocol classes 0 – 4

Internet protocols User Datagram

Protocol Transmission Control

Protocol

CLOSED

LISTEN

SYN RCVD SYN SENT

ESTABLISHED

FIN WAIT 1

FIN WAIT 2

CLOSING

TIME WAIT

CLOSE WAIT LAST ACK

Send SYN

Recv SYN ACK

Send ACK

Send FIN

Recv ACK

Recv FIN Send ACK

Timeout

Send FIN

Recv SYN

Send SYN ACK

Recv FINSend ACK

Recv ACK

Timeout

Recv RST

Recv SYN Send SYN ACK

Send FIN

Recv FIN Send ACKRecv FIN ACKSend ACK

Recv ACK

Send SYN

TCP state machine


TCP Features

IP fragmentation vs TCP segmentation RTT estimation for timer management Initial sequence number allocation

Reuse of session identifiers High bandwidth or long-lived slow sessions

Limit transmission rate Both needed Flow Control

Receiver capacity Congestion Control

Network capacity


Flow Control Approaches

Sliding window / static buffer allocation

Sliding window / no buffer allocation

Credit mechanism

TCP’s flow control Sliding window and

credit mechanism Nagle’s algorithm Silly window problem

Sender Receiver

time time

<req 8 buffers>

<cred=4>

<seq=0, data=m0>

<seq=1, data=m1>

<seq=2, data=m2>

<ack=1, cred=3>

<seq=3, data=m3>

<seq=4, data=m4>

<seq=2, data=m2>

<ack=4, cred=0>

<ack=4, cred=1>

<ack=4, cred=2>

<seq=5, data=m5>

<seq=6, data=m6>

<ack=6, cred=0>

<ack=6, cred=4>

A wants 8 buffers

A has 3 buffers left

A has 2 buffers left

Message lost but A thinks it has 1 left

A has 1 buffer left

A has 0 buffer left, must stop

A times out and retransmits

A still blocked

A may now send next msg.

A has 1 buffer left

A is now blocked again

A still blocked

B grants messages 0-3 only

Message lost

B acknowledges 0 and 1permits 2-4

Everything acknowledgedbut no free buffers

B found a new buffersomewhere

A has 1 buffer left

A is now blocked again

TCP credit mechanism


Congestion Control Congestion control

Can worsen without care

Approaches Repair

Packet dropping Max buffer, min

buffer, content related

Choke packets Threshold and

history, several levels

Fair queueing Avoid

Traffic shaping Leaky bucket Token bucket

Reservation

A

B C

D

E F

Smoothed streamPeak rate

Original packet arrival

time

Choke packets

Traffic shaping


Congestion Control and Avoidance Congestion control with TCP

Additive increase, multiplicative decrease

Congestion Window Development

Slow start Congestion window threshold Congestion avoidance phase

Decrease Missing ACKs Timeout

Congestion avoidance with RED and ECN

Random Early Detection Drop packets randomly when

IS queues fill up Early Congestion Notification

Mark packets instead of dropping when IS queues fill up

sender receiver

time

40

20

105

80

15

3025

35

75

55

4550

6560

70

Tail drop

RED

ECN

TCP congestion control

Router queues with RED and ECN


Quality of Service QoS: Characterizes the well defined, controllable behavior of a

system with regard to quantitatively measurable parameters

Techniques to Fulfill Requirements Delay and jitter

Reservation, Buffering, Scaling Continuity

Real-time packet re-ordering, Loss detection and compensation, Retransmission, Forward error correction, Stream switching

Synchronity Fate-sharing and route-sharing, Time-stamped packets, Multiplexing,

Buffering, Smoothing QoS negotiation

Resource reservation Styles

Sender-oriented Receiver-oriented combined


Multimedia Protocols Multimedia

Time-independent media discrete media Time-dependent media continuous media Interdependent media multimedia

Application level framing Applications know their needs, e.g. ordering and loss Application defines data unit size Try to avoid segmentation

Integrated layer processing Process several layers at once Ordering constraints exist


Multimedia Protocols RTP/RTCP

Real-time Transport Protocol ALF and ILP

RTP Profiles Sequencing, synchronization,

payload identification, quality feedbackand session information

Multicast, mixers, translators No reliability, no QoS support

Signaling protocols RTSP

Useful for Video-on-Demand, Near Video-on-Demand, live broadcasts

SIP Useful for internet

telephony andconferencing

Application

RTCP RTP

DecodingEncoding

Application

UDP/IP UDP/IP

RTCPRTP

Decoding Encoding

RTSP signalling

SIP signalling

RTP/RTCP interaction

18. may. 2006 1inf-3190: overview connecting networks by relays layer 1: repeater / hub layer 2:...

Documents

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flow control layer