IP in LANs
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 1
LAN Technologies
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Ethernet - 10 Mbps, 100Mbps Fast Ethernet, Gigabit Ethernet
Cable TV LANs
Wireless LANs
Token Ring, Token Bus
FDDI
ATM LANE, MPOA
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 2
Ethernet Principles
• Originally utilized shared media
• Operates on almost any media:
• IEEE 802.3 physical layer specifications
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© NOKIA
10BASE5 Thick Coax
10BASE2 Thin Coax
10BASE-T Twisted Pair
10BROAD35 CATV wire
10BASE-F Fibers
DEFAULT.PPT / 22.08.1997 / AO page: 3
Ethernet medium specifications
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10BASE5, 0.5" coax bus
transceiver and drop cable required
Max length of the bus is 500 meters
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 4
Ethernet Medium Specifications - cont
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10BASE2, thin 0.25" coax
Hosts are connected directly to the thin coax bus
Bus max. 200 meters long
susceptible to any faults in the cable or hosts' network equipment
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 5
Ethernet Medium Specifications - cont
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10BASE-T twisted pair cable
Hosts connected to a HUB
At present most popular installation
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 6
Ethernet Medium Specifications - cont
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10BASE-F Fibers especially used between HUBs and LAN core
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Star topology: Up to 33 stations with 1 km link length
2km link length in Point-to-Point connections
A pair of fibers needed for single link - one for transmission and other for
receiving
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 7
Ethernet IEEE 802.3 frame format
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Ethernet is connectionless, frame exchange protocol
Each station has unique 6 octet long address
Frame Size
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max. 1518 octets
min 512 bits
+-------------+--------+----------------------+------------------+-----------+--------------+---+---------+
|Preamble(7)|SFD(1)|Destination addr(6)|Source addr (6)|Length(2)|Data(<1500)|Pad|CRC(4) |
+-------------+--------+----------------------+------------------+-----------+--------------+---+---------+
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 8
Ethernet CSMA/CD
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IEEE 802.3 Medim Access Control (MAC)
CSMA/CD Carrier Sense Multiple Access / Collision Detection
Fairly simple algorithm:
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Listen to the network - wait until media is free
Wait interframe gap time
If still free, start sending - simultaneously monitor received signal
If collision is detected, transmit jam sequence, wait random time and restart algorithm
Min. packet size and max. link length defined so that collisions detected
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 9
Ethernet LAN architecture
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Bridge - a transparent layer 2 device that interconnects several segments
Many benefits
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© NOKIA
Security
Performance
Reliability
Structure
DEFAULT.PPT / 22.08.1997 / AO page: 10
Ethernet Hubs
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10BASET twisted pair from host to hub
Usually Fiber link from hub to LAN backplane
Better structureand security
easier to install and maintain
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 11
Ethernet Switching
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Switching HUB - a HUB operating like learning bridge
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Usually dual-speed: Configurable 10Mbps and 100Mbps ports
FIFO-buffered backplane bus: Hub is able to transmit several frames through
the hub concurrently
Dedicated 10Mbps
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 12
Ethernet Switching
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Ethernet Switches used increasingly to replace routers
Switching much faster than routing
Also Routing Switches available that combine Router and Switch functionality
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© NOKIA
Route once, switch following frames
DEFAULT.PPT / 22.08.1997 / AO page: 13
Address Resolution Protocols
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Underlying network is not aware of IP
ARP used to bind IP addresses to MAC addresses
RFC826: ARP protocol for Ethernet
ARP Solves MAC addresses by broadcasting a ARP request:
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source IP address
source MAC address
destination IP address
empty space for destination MAC address
Reverse ARP - diskless host wants to know its IP address
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 14
DHCP
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Used for similar operation as RARP
Supports three IP address mechanisms:
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automatic
dynamic
manual
Decreases amount of IP-addresses needed in LAN
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 15
DHCP - cont
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Messages:
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DHCPDISCOVER - Client broadcast to locate available servers.
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DHCPREQUEST - Client broadcast to servers requesting offered
parameters from one server and implicitly declining offers from all others.
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DHCPACK - Server to client with configuration parameters, including
committed network address.
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DHCPNAK - Server to client refusing request for configuration
parameters (e.g., requested network address already allocated).
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DHCPDECLINE - Client to server indicating configuration parameters
(e.g., network address) invalid.
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DHCPRELEASE - Client to server relinquishing network address and
cancelling remaining lease.
© NOKIA
DHCPOFFER - Server to client in response to DHCPDISCOVER with
offer of configuration parameters.
DEFAULT.PPT / 22.08.1997 / AO page: 16
applied ARP usage
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A Proxy-host that is attached to LAN and replies to ARP request targeted to
hosts attached behind the Proxy
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can be utilized
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© NOKIA
in simple Firewalls
to create private local sub-net without need to allocate "real" IP-addresses
by a host that tunnels IP packets through some other network technology
DEFAULT.PPT / 22.08.1997 / AO page: 17
LAN development and markets
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100 Mbps Fast Ethernet, included in IEEE 802.3
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compatible with 10Mbps Ethernet
compatible with 10Mbps Cabling
link lengths reduced
Gigabit Ethernet, IEEE 802.3z standardization in process
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© NOKIA
especially to be used on fiber links
LAN backplane
Compatible with 10Mbps frames
DEFAULT.PPT / 22.08.1997 / AO page: 18
Markets
1.1.1 Revenue and Shipments of Shared Media Hubs to Worldwide (Dataquest 08/97)
1997
Ports Shipped (K)
Shipment Growth
Average end-user price (USD)
End-user revenue (USD M)
Revenue growth
1998
1999
2000
72864,8 76563 76211,8 75030,6
16,1 %
5,1 % -0,4 % -1,5 %
66,4
55,6
48,6
46,1
4835,8 4258,7 3703,4 3458,9
3,2 % -11,9 % -13,0 % -6,6 %
2001
CAGR
1997-2001
73604
0,2 %
-1,9 %
46,1
-6,9 %
3390,5
-6,7 %
-2,0 %
1.1.1 Worldwide shared media hub market split by technology (Datamonitor, 07/97)
(USD)
10Mbps Ethernet
100 Mpbs Ethernet
Token Ring
Other (incl. FDDI)
TOTAL
© NOKIA
1995
3800
240
730
180
4950
1996
4020
380
630
250
5280
DEFAULT.PPT / 22.08.1997 / AO page: 19
1997
4330
460
480
330
5600
1998
4490
540
350
390
5770
1999
4580
620
260
430
5890
2000
4420
680
200
410
5710
2001
4200
700
150
350
5400
LAN Markets
1.1.1 Worldwide LAN switch market split by technology, 1995-2001 (Datamonitor,
07/97)
USD millions
ATM
10Mbps Ethernet
100Mbps Ethernet
Gigabit Ethernet
Token ring
IP / L3 switching
Other
1995 1996 1997 1998
140
340
650 1 020
1 080 2 480 3 430 4 150
80
240
610 1 350
0
0
50
200
100
260
450
600
0
0
60
200
100
200
330
400
Total
1 500 3 520 5 580 7 920 10 330 12 700 15 200
© NOKIA
DEFAULT.PPT / 22.08.1997 / AO page: 20
1999
1 340
4 370
2 700
450
600
420
450
2000
1 700
4 400
3 900
950
550
800
400
2001
2 000
4 450
5 100
1 700
450
1 150
350