Technik der Netze

1

Network Technologies - Switching
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Agenda

• What is switching?
• How does it work?
• Ethernet Switches
• Areas of application for switches

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Switches (1)
4
Switches (2)
CP6923 Switch

• 24 port GbE switch
• Options
• 4 GbE ports front 20 ports rear
• 2x 10 GbE front, 24 ports rear

• Ethernet
• Local Area Networks (LAN)
• What does it switch?

5
Local Area Networks (LAN)
LAN, Protocols, Layer 2, Layer 3?
Source Harald Orlamünder
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Local Area Network - Protocols
ETHERNET (IEEE 802 Reference Model)
ISO/OSI Model
7
Application
Presentation
6
Higher protocol layers
5
Session
4
Transport
Link Service Access Point
Network
3
LSAP
2b
Logical Link Control (LLC)
Link
2
Medium Access Control (MAC)
2a
Physical
Physical
1
1
7
Local Area Network IEEE Standards
Logical Link Control (802.2)
2 Link
Bridging (802.1)
Management (802.1)
Ethernet MAC (802.3)
Wireless MAC (802.11)

1 PHY
LAN-PHY (802.3)
Wireless MAC PHY (802.11)

• Also available IEEE reference model for
  implemetion
• Different physical layers (Coax, Copper Pairs,
  optical fibre), modes (half duplex, full duplex)
  and Speeds
• Classification e.g. 10 BASE-5, 100 BASE-FX,
• To be implemented on switch

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How does it work?
Concepts for switching
9
Home Network
Host
Host
LAN
Switch/Hub
Network Printer
Router DSL-Modem
How do the scenarios work?
Internet
Web Server
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Adressing in the Home Network
192.168.178.21 00130239e5f7
Host
192.168.178.22 000a95d15230
Host
LAN
Network Printer
Switch/Hub
192.168.178.23 00807731b645
192.168.178.1 00040e733f3d
Router DSL-Modem

• IP addresses assigned by the router (DHCP)
• MAC addresses built in by manufacturer of network
  interface

IP-Address (L3) MAC Address (L2)
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How a Hub works (1) Request
100130239e5f7
Host
1000a95d15230
Host
LAN
Network Printer
Hub
100807731b645
100040e733f3d
Propagate request to all ports

• Everything is based on MAC addresses
• Hub multiport repeater

12
How a Hub works (2) Reply
100130239e5f7
Host
1000a95d15230
Host
LAN
Network Printer
Hub
100807731b645
100040e733f3d
Propagate reply to all ports
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From Hubs to Bridges
Bridge
Ethernet the first popular serial bus

• A Hub solders two LAN segments together
  (propagates messages received to all ports
  repeats everything)
• A Bridge bridges two LAN segments (propagates
  only messages from one segment intended for the
  other segment)

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How a Bridge works (1) 1st Request
100130239e5f7
Host
1000a95d15230
Host
LAN
Network Printer
Bridge
100807731b645
100040e733f3d
1st time Propagate request to all ports
Memorize receiver port MAC address
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How a Bridge works (2) Reply
100130239e5f7
Host
1000a95d15230
Host
LAN
Propagate reply to the right port
Network Printer
Bridge
100807731b645
100040e733f3d
A bridge is a hub with memory.
Memorize receiver port MAC address
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How a Bridge works (3) 2nd Request
100130239e5f7
Host
1000a95d15230
Host
LAN
Network Printer
Bridge
100807731b645
100040e733f3d
Propagate request to the right port
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Hubs, Bridges and Switches
Concepts Demo Animation
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Conceptual Architecture
Output buffer
Input buffer
processor
Ports
Ports
Memory (switch routing table)

• Processor analyse protocol header
• Place packet/frame on right output port

How to transmit frames?
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Hubs, Bridges and Switches
A Switch is a Bridge with max. line speed
between any ports.
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Using IP Addresses as host identifiers
192.168.178.21 00130239e5f7
Host
192.168.178.22 000a95d15230
Host
LAN
Network Printer
Hub/Switch
192.168.178.23 00807731b645
192.168.178.1 00040e733f3d
ARP (Address Resolution Protocol) Who is
192.168.178.22?

• IP Addresses convenient host identifiers
• MAC addresses used for message delivery

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Adress Resolution Protocol (1)
192.168.178.21 00130239e5f7
192.168.178.22 000a95d15230
Host
Host
LAN
Who is 192.168.178.22 ?
Network Printer
Hub/Switch
192.168.178.23 00807731b645
Who is request containing destination IP-Adress
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Adress Resolution Protocol (2)
192.168.178.21 00130239e5f7
192.168.178.22 000a95d15230
Host
Host
LAN
Network Printer
Hub/Switch
192.168.178.23 00807731b645
Host replies with MAC adress

• ARP implemented in hosts
• resolves IP adresses into MAC addresses
• MAC addresses used for message delivery

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ARP Demo

• A nice demo of ARP is available at
  http//www.oxid.it/downloads/apr-intro.swf
• Remarks
• ARP is a so called stateless protocol, it is
  not aware whether different requests or replies
  belong to the same transaction or not.
• The demo also shows, how ARP may be misused to
  introduce a sniffer or man in the middle to
  eavesdrop or manipulate data streams
• There are ways to protect networks, but awareness
  of security issues is always needed.
• Local Demo C\Dokumente und Einstellungen\stephru
  \Desktop\Seminar\resources\ARP_Demo\apr-intro.swf

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Switching Routing
Network of switches (L2) Network of Routers
(L3) Network of relations (application level)
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Switching and Routing
Host
Host

• Switching
• Local area network
• Layer 2 protocols

LAN
MAC Address
Port No
Switch/Hub
Network Printer
Router DSL-Modem
IP Address
Port No

• Routing
• Wide area network
• Layer 3 protocols

Internet
Web Server
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Managed Switch/ L3 Switch

• Managed Switch
• has IP address to connect management terminal
  (not needed for message delivery)
• Management via CLI, SNMP, TELNET
• Ethernet/Bridging protocols (Layer 2)
• Link aggregation (802.3ad), VLANs (802.1Q),
  Spanning Tree (802.1D, 802.1w), QoS (802.1p),
  Flow control (802.3x), GVRP, GMRP
• IP routing protocols (Layer 3)
• OSPFv2, RIPv2, VRRP, IGMP snooping, IPv4
  forwarding, DiffServ, ARP, ICMP
• DCHP Client/Server receive/distribute local IP
  addresses

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Ethernet- and IEEE 802.3-Frames
Ethernet-Frame
DestinationAddress
SourceAddress
Type
Information (IP-Packet)
CRC
6
6
2
46 ... 1500
4
IEEE 802.3 Frame
DestinationAddress
SourceAddress
Len
Information (IP-Packet)
CRC
LLC/SNAP
6
6
2
8
38 ... 1492
4
MAC
DSAP
SSAP
crtl.
Org.Code
Type
1
1
1
3
2
LLC
SNAP
Source Harald Orlamünder
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Virtual LAN

• Classify ports and Ethernet frames into groups
• Segmentation into separate and independent LANs
• Controlled environment with reduced complexity

VLAN1
VLAN2
LAN
VLAN3
Trunk
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VLAN Frame Format
QTag Prefix
DestinationAddress
SourceAddress
Tag Type
Tag Control
Type
Data
PAD
FCS
6 octet
6 octet
2 octet
46 ... 1500 octet
4 octet
2 octet
2 octet
Priority ID
CFI
VLAN-ID
CFI Canonical Format Identifier FCS Frame Check
Sequence PAD Padding
3 Bit
1 Bit
12 Bit
Source Harald Orlamünder
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Switched Networks

• Local Area Networks
• Home Networks
• Corporate Networks
• Industry Automation
• Transport
• Medical
• But also
• CPCI Systems according to PICMG 2.16
• Ethernet in the backplane!
• ATCA and mTCA systems

CP6923
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Areas of Application
Communications Indutrial Automation Tansport Medic
al
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Session Control and Media Processing
Video/Audio On demand
Life TV/ local TV

• Media Server
• announcements
• IVR
• conferences
• voice mail
• customised tunes
• streaming media
• trunking gateways

PSTN
Media Server
Trunking GW/ Signalling Gateway
Call Server/ Gateway Controller
IP Network (Carrier)

• Call Server
• control call sessions (SIP/H.323 call control)
• control Media Server Gateways

PLMN
Trunking GW
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CPCI User Agents for Conformance Load Tests
CP-ASM10-PSB
CP6923 Switch (Option)
14 slot 10U CPCI chassis PICMG 2.16 compliant 19
wide, 285 mm deep 4 power supplies (200W each)
for 120/230VAC 600 calls per second per CP6012
CP6012 CPU Blade Intel Core Duo CPU _at_1.66GHz 1 GB
RAM (Option up to 4GB) 40 GB 2.5 SATA HDD on
board 2x GbE on Front Panel 2x GbE on backplane
24 port GbE switch Options 4 GbE ports front 20
ports rear 2x 10 GbE front, 24 ports rear
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Industrial Ethernet

• Many field bus systems will move to Ethernet
  (Industrial Ethernet)
• Requirements
• Low latency
• Distributed systems
• Remote monitoring control
• Areas of application
• Process control
• Facility control
• Communication Technology

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Transport

• Entertainment systems
• Announcements
• Video surveillance
• Replacement of field bus systems

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Medical

• Image Processing
• Image sources (e.g. digital radiography)
• Pre Post-Processing
• Archives
• Workstations
• All connected over Ethernet Networks
• Processors
• Ethernet connectivity
• CPUs, DSPs
• multi-processor
• Communication technology (VoIP)

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Recommeded Reading
Industrielle Netze A. Bormann, I. Hilgenkamp,
Hüthig, 2005, ISBN 3778529501 (in German)
Recommendation Paket-basierende Kommunikationspro
tokolle Harald Orlamünder, Hüthig
Telekommunikation, 2004, ISBN 3826650468 (in
German)
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The End Switching Technologies