HighSpeed LAN and Backbone Networks

1
High-Speed LAN and Backbone Networks

• After studying this Chapter you should
• Know which internetworking devices are used in
  backbone networks
• Describe several types of fast Ethernet and fast
  Token Ring
• Describe FDDI
• Describe ATM and fiber channels
• Know ways to improve performance on BN

2
Definition

• Backbone Network (BN) - a large high-speed
  central network that connects all the terminals,
  microcomputers, mainframes, local area networks,
  and other communications equipment on a single
  company or site. Sometimes called a Campus Area
  Network (CAN). Use Higher speed circuits for
  connectivity.

3
Definition

• Enterprise Network (EN) - a supernetwork that
  interconnects all of an organizations networks
  (LANs and WANs), regardless of whether it crosses
  state, national, or international boundaries.

4
Why interconnect networks?

• Reliability
• Performance
• Security

5
Introduction

• There are two approaches to providing high speed
  networking.
• speed up the technologies currently used in
  local area networks.
• Fast Ethernet
• Fast Token Ring
• develop new high speed technologies that provide
  dedicated point-to-point communication circuits
• Switched Ethernet
• Switched Token Ring
• ATM

6
Backbone Network Components

• Two basic components to the BN
• hardware devices that connect the networks to the
  backbone
• hubs
• bridges
• switches
• routers
• brouters
• gateways
• network cable

7
Hubs

• very simple devices that pass all traffic in both
  directions between the LAN sections they link
• same or different cable types
• use physical layer protocols
• pass on every message
• used to connect LANs of similar technology, or to
  extend the distance of one LAN
• can be called repeaters or amplifiers

8
HUB Devices
Repeater/Amplifier
HUB (MAU)
9
Hubs

• inexpensive
• easy to Install
• can connect different media
• very little delay
• limited distance between devices
• limited on the number of repeaters
• no protocol or rate conversion
• no error detection
• does not filter

10
Bridges

• connect two LAN segments that use the same data
  link and network protocol
• operated at the data link layer
• same or different cable types
• forward only those messages that need to go out
  (filtering)
• learn whether to forward packets
• internal routing table
• combination of black box hardware and software

11
Bridges

• There are three types of bridges
• Simple bridge
• Learning bridge
• Multiport bridge

12
Bridges Interconnecting
Bridge
13
Bridges

• may be different data rates and different media
  easy to Install
• no modifications required to the communications
  software
• can learn the ports for data transmission
• understand only data link layer protocols and
  addresses
• no protocol conversion
• broadcasts when it does not know the address

14
Switches

• connect more than two LAN segments that use the
  same data link and network protocol.
• operate at the data link layer
• same or different type cable
• ports are usually provided for 4, 8, 16, or 32
  LAN segments
• ports are used simultaneously
• connect lower speed segments to high speed BN

15
Switches

• Cut-through switches
• use circuit-switching to immediately connect the
  port with the incoming message to the correct
  outgoing port
• very fast as decisions are done in hardware
• outgoing packet is lost if port is in use
• Store-and-forward switches
• copy the incoming packet to memory prior to
  processing the destination address -- transmit it
  when the outgoing port is ready

16
Switches Interconnecting
17
Switches

• much more sophisticated than previously
• enable all ports to work at the same time
• can convert protocols
• configurable
• high speed
• understand only data link layer protocols and
  addresses
• much more expensive then previous options
• higher maintenance

18
Routers

• connect two or more LANs that use the same or
  different data link protocols, but the same
  network protocol.
• same or different cable types
• operate at the network layer
• forward only messages that need to go out
• routers use the internetwork address
• internal routing tables
• only processes messages addressed to it

19
Routers

• choose the best route to send the packet (path)
• IDs of other networks
• paths to the networks
• relative efficiency of the paths

20
Routers

• The router must deal with network differences
• addressing schemes
• minimum packet size
• interfaces
• reliability

21
Routers Interconnecting
Router
\
Ethernet LAN2
X.25 Network the cloud
Token Ring LAN1
22
Routers

• can mix-in-match protocols and convert them
• enable all ports to work at the same time
• can be used as an extra layer of security
• configurable
• high speed
• hard to configure and manage
• access lists must be kept current
• high maintenance/high training costs
• very expensive

23
Brouters

• devices that combine the functions of both
  bridges and routers
• operate at both the data link and network layers
• same or different data link protocol
• same network protocol
• as fast as bridges for same data link type
  networks

24
Gateways

• complex machines that are interfaces between two
  or more dissimilar networks
• connect two or more LANs that use the same or
  different data link layer, network layer, and
  cable types
• operates at the network layer (3) or higher
  layers (4-7)
• forwards only those messages that need to go out
• a combination of both hardware and software

25
Gateways

• translates one network protocol to another
• translates data formats
• translates open sessions between application
  programs
• translates to mainframes

26
Gateways

• Exists in four major types
• LAN-to-IBM mainframe
• Network-to-network
• System-to-network
• System-to-system

27
LAN-to-IBM Mainframe

• Allow LANs using TCP/IP and Ethernet to be
  connected to IBM mainframe using SNA
• Eliminates the need for each PC on the LAN to
  have SNA hardware/software that makes it act like
  an IBM 3270 terminal

Mainframe
Gateway
28
Network-to-Network
\
X.25 Network A
X.75 Gateway
\
X.25 Network B
X.75 provides terminal address translation
29
System-to-Network
\
X.25 Network
Gateway
Minicomputer or Microcomputer
30
System-to-System

• allows connecting one vendors architecture to
  another vendors architecture
• allows both the existence of OSI-based and
  proprietary architectures (like SNA or AppleTalk)
  
• gives management to tools necessary to plan a
  gradual migration to a completely OSI environment
• applications can work with other application

31
System-to-System
Profs E-mail Gateway
\
X.25 Network
LAN E-mail Server
Profs E-mail
LAN E-mail Gateway
32
Backbone Network Devices
Physical Data Link Network Device Oper
ates at Messages Layer Layer
Layer
Hub Physical All transferred S/D Same Same Bridg
e Data link Filtered using S/D Same Same dat
a link layer add. Switch Data link Switched
using S/D Same Same data link layer
add. Router Network Routed using
S/D S/D Same network layer
add. Brouter Data link Filtered
routed S/D S/D Same Network Gateway Network Rout
ed using S/D S/D S/D network layer add.
33
Terminology Warnings

• Multiprotocol bridges translate between different
  data link layer protocols.
• Multiprotocol routers translate between different
  network layer protocols.
• Protocol filtering bridges forward only packets
  of a certain type, i.e., token-ring or ethernet
• Encapsulating bridges connect networks with
  different data link protocols, encapsulating
  messages with correct protocol for transmission
• Layer-3 switches (IP switches) - can also switch
  messages based on their network layer address

34
Shared Media Technologies

• Fast Ethernet
• Fast Token Ring
• Fiber Distributed Data Interface

35
Fast Ethernet

• 100Base-X Ethernet
• 100VG-AnyLAN
• Gigabit Ethernet
• Iso-ENET (isochronous ethernet)

36
100Base-X Ethernet

• IEEE 802.13
• identical to 10Base-T Ethernet
• three data link layer protocols
• 100 Mbps data rate
• standard ethernet bus topology
• ethernet data link packets
• ethernet CSMA/CD media access protocol

37
100Base-X Ethernet

• Three versions of 100Base-X Ethernet
• 100Base-TX
• 100Base-FX
• 100Base-T4

38
100VG-AnyLAN

• IEEE 802.12
• both Ethernet or token-ring
• Demand Priority Access Method (DPAM) polling
• polls each computer to see if it has data to send
• can use a priority system (notification system)
• four sets of twisted pair running at 25 Mbps
• faster than 100Base-T

39
Gigabit Ethernet

• IEEE 802.3Z
• 1000Base-X
• 1000 Mbps (1000 Mbps 1 Gbps)
• high speed of transmission may cause collisions
  to go undetected
• mainly used for point-to-point full-duplex
  communication links (BN, MAN)
• PCs send or receive data at rates up to 100 Mbps

40
Gigabit Ethernet

• Four versions of 1000Base-X Ethernet
• 1000 Base-LX (fiber up to 440 meters)
• 1000 Base-SX (fiber up to 260 meters)
• 1000 Base-T (four pairs twisted-pair up to 100
  meters)
• 1000 Base-CX (one cat 5 cable up to 24 meters)

41
Iso-ENET

• IEEE 802.9A
• isochronous Ethernet
• standard 10Base-T Ethernet 6.144 Mbps
• both transmitted on the same twisted pair
• 6.144 circuit configured for ISDN for
  transmission of voice and video
• mainly used for desktop videoconferencing and
  multimedia products

42
Fast Token Ring

• high-speed token ring (HSTR)
• standard token ring topology
• standard token ring protocols
• token passing media access control
• 100 Mbps instead of 16 Mbps
• category 5 or fiber optics cable
• IBM working on 1 Gbps version

43
Fiber Distributed Data Interface (FDDI)

• ANSI X3T9.5
• Topology - token-passing
• 2 counter-rotating rings
• Each ring operates at 100 Mbps over fiber optic
  cable
• maximum of 1000 stations
• distance 120 mile path (200k)
• required repeaters to push transmission (2K)
• data is usually carried on the primary ring

44
FDDI Station Types

• Dual-Attachment Station (DAS)
• connects to both primary and secondary rings
• requires 4 fibers to the desk
• allows the ring to continue to operate even if a
  break occurs in the line by rerouting through the
  secondary ring (backwards)
• Single-Attachment Station (SAS)
• connects only to the primary ring
• requires 2 fibers to the desk

45
FDDI Topology
Mainframe
Workstations
Primary Ring
Secondary Ring
SAS
SAS
Gateway
FDDI Hub
SAS
Bridge
46
FDDI - How does it work?

• Media accesss control
• variation of token-passing standard
• FDDI allows multiple messages to attach to the
  token - increases throughput above 100 Mbps
• An FDDI-to-IEEE 802.x bridge is required to
  connect to lower speed corporate LANs
• At each node the optical signal is
• converted to an electrical signal
• amplified
• copied (if necessary)
• converted back to light to send to the next node

47
Types of FDDI

• Basic FDDI previously discussed
• FDDI-C (FDDI on Copper)
• Copper Distributed Data Interface (CDDI)
• uses copper wire instead of fiber optic
• FDDI-II
• permits transmission of voice and video over the
  same cable as FDDI token-passing data
• uses time division multiplexing
• 17 channels
• 1 - 768 Kbps channel (token-passing)
• 16 - 6.144 Mbps channels (wide band - voice/video
  or data)

48
Switched Networks

• Switched Ethernet
• Full-Duplex Ethernet
• Switched Token Ring
• Switched FDDI
• Asynchronous Transfer Mode (ATM)
• Fibre Channel

49
Switched Ethernet

• the switch replaces the hub
• creates a point-to-point circuit to the switch
• allows multiple transmissions between computers
• store-and-forward
• improves LAN performance
• circuit to the server is the network bottleneck

50
Other Ethernet Solutions

• Full-Duplex Ethernet
• uses the same cables as regular Ethernet
• 10BaseT but full-duplex
• doubles the speed of connections to 20 Mbps
• full-duplex only from the switch to the server
• may have several connections to one server
• 10/100 switched ethernet
• combines 10BaseT and 100BaseT to the server
• cheaper to install than 100Base-T
• maybe as fast as fast ethernet

51
Switched Token Ring

• token ring switch replaces the token ring hub
• provides a series of point-to-point connections
• star topology
• no token to pass because of full duplex switch
• called token-ring because it uses token ring
  packet format and is compatible with 802.5
  hardware
• dedicated token ring (DTR) full duplex
• 32 Mbps data rate due to full duplex (16 Mbps
  each direction)

52
Switched FDDI

• FDDI witch replaces the FDDI hub
• point-to-point connctions to computers
• star topology
• no token because all computers can transmit and
  receive at will
• same packet format and is fully compatible with
  other FDDI hardwar

53
ATM

• Isochronous networks provide very low and
  predictable node-to-node delays. They are
  capable of dealing with steady, immediate
  delivery, and high-bandwidth requirements of
  multimedia technology.
• Asynchronous Transfer Mode (ATM) is the ultimate
  isochronous technology by allocating bandwidth on
  demand via virtual circuits.
• high-speed, hardware-based, circuit-switching
  technology
• cell-relay
• LANE (LAN Emulation/LAN Encapsulation)
• connection-oriented
• ATM desktop - point-to-point full duplex - low
  speed version for the desktop

54
ATM

• ATM is a switched network but differs from
  switched ethernet and switched token ring in four
  ways
• 1. ATM uses fixed-length packets of 53 bytes
  (ATM encapsulation)
• 2. no error correction on the user data
• 3. ATM uses a very different type of addressing
  from traditional data link layer protocols such
  as ethernet or token ring
• 4. ATM prioritizes transmissions based on
  Quality of Service (QoS).

55
Asynchronous Transfer Mode (ATM)

• Asynchronous Transfer Mode is connection-oriented
  so all packets travel in order through the
  virtual circuit. A virtual circuit can either be
  a
• Permanent Virtual Circuit (PVC) - defined when
  the network is established or modified.
• Switched Virtual Circuit (SVC) - defined
  temporarily for one transmission and deleted with
  the transmission is completed.

56
LAN Translation

• two approaches for translation
• LANE (LAN Emulation/LAN Encapsulation)
• Multiprotocol over ATM (MPOA)

57
LAN Encapsulation

• usually referred to as LAN Emulation
• data link layer packets left intact broken down
  and encapsulated
• reassembled on the LAN side
• LAN thinks that the packets are token ring or
  Ethernet
• requires ATM edge switches at each side

58
Multiprotocol over ATM

• extension of LANE
• uses network layer addresses and data link layer
  addresses
• destination determines which address to use
• route servers required (MPOA servers)

59
ATM to the Desktop

• ATM-25 is a low speed version of ATM which
  provides point-to-point full duplex circuits at
  25.6 Mbps in each direction. It is an adaptation
  of token ring that runs over cat 3 cable and can
  even use token ring hardware if modified.
• ATM-51 is another version designed for the
  desktop allowing 51.84 Mbps from computers to the
  switch.

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ATM Classes of Service

• ATM provides five classes of service
• Constant Bit Rate (CBR)
• Variable Bit Rate-Real Time (VBR-RT)
• Variable Bit Rate-Non-Real Time (VBR-NRT)
• Available Bit Rate (ABR)
• Unspecified Bit Rate (UBR)

61
Fiber Channel

• Fiber channel is relatively new networking
  technology, although it has been used inside
  computer and disk storage devices for several
  years.
• Fiber channel was originally designed to provide
  high speed transmission over fiber optic cable.
  The maximum data rate is 1.062 Gbps up to 10 k
  with higher rates under development.

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Improving Backbone Performance

• change network protocol
• check impact of applications
• replace the hubs with switches and make
  point-to-point connections available
• increase circuit capacity
• make sure BN devices have sufficient memory, so
  packets dont get lost and have to be resent

63
Improving Backbone Performance

• use faster routing protocol
• upgrade computers that perform routing
• use switches from a single vendor
• eliminate need for switch-to-switch routing by
  use of collapsed backbone switch

64
Collapsed Backbone Networks

• uses point-to-point circuits when possible
• uses a switch and a set of circuits to each LAN
• uses more cable, but fewer devices
• backbone exists in the switch
• improved performance
• switch replaces multiple bridges or routers
• lowers costs
• simplifies network management
• if the switch fails, the network is down

65
Improving Circuit Capacity

• increase overall circuit capacity or place
  additional circuits alongside heavily used
  circuits
• move from shared circuit to switched circuit BN
• increase capacity to the server

66
Improving Circuit Capacity
How much bandwidth to expect LAN
Type Speed Ethernet 10 Mbps Token Ring 16
Mbps Fast Ethernet 100 Mbps Faster Ethernet 1
Gbps Fast Token Ring 100 Mbps FDDI 100
Mbps ATM 2.4 Gbps
67
Reduce Network Demand

• restrict high-bandwidth applications
• video conferencing
• medical imaging
• multimedia
• set routing devices to filter broadcast messages

68
Selecting a Backbone Network

• 5 important factors to consider
• Throughput
• Network cost
• Type of application
• Ease of network management
• Compatibility with current and future
  technologies