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Local Area Networking. Chapter 8. Knowledge Concepts. Components of a LAN Transmission media Transport Access methods Topologies Interconnection VLANs Switches and routers. LAN Cabling system Broadband vs baseband CSMA/CD Token Tree ISPF, RIP BGP-4. Bus Ring Star Switch Vlan

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Presentation Transcript

Knowledge concepts
Knowledge Concepts

  • Components of a LAN

  • Transmission media

  • Transport

  • Access methods

  • Topologies

  • Interconnection

  • VLANs

  • Switches and routers


Important vocabulary

LAN

Cabling system

Broadband vs baseband

CSMA/CD

Token

Tree

ISPF, RIP

BGP-4

Bus

Ring

Star

Switch

Vlan

Bridge

Router learning

Static vs dynamic

Important Vocabulary


Topology
Topology

Topology is the basic geometric layout of the network -- the way in which the computers on the network are interconnected.

  • Ethernet uses a bus topology (a high speed circuit and a limited distance between the computers, such as within one building).


Bus topology
Bus Topology

Terminators required on each end


Ring topology
Ring Topology

Data Flow



Star topology
Star Topology

Preferred method for today’s LANs

Wiring Hub


Media access control
Media Access Control

  • Ethernet uses a contention-based technique called Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

  • If two computers attempt to transmit at the same time, they detect the collision, send a jamming signal, wait a random amount of time, then re-broadcast.




Ethernet tree topology
Ethernet Tree Topology

  • Each hub broadcasts to own segment

  • Misbehaving nodes will be shut off by the hub


Throughput
Throughput

  • CSMA/CD works well for small number

  • Of nodes per wire

  • Throughput defined as useful data that

  • Can go across wire

  • PPS (packet per sec) or percent

  • Utilization of wire speed




Network servers everything you wanted to know but were afraid to ask
Network Servers: Everything You Wanted to Know But Were Afraid to Ask!

  • Servers use multiple processors

    • Very important to access-intensive operations

    • Multiple processors provide 50% improvement

  • Buses provide backbone internal support for data transfer

  • RAM provides a buffer for operations


Lan operating system functions
LAN Operating System Functions Afraid to Ask!

  • Optimized I/O

    • One of the main services provided by a server is disk access. Disk access consists of three components: seek, latency, and transfer.

    • I/O optimization attempts to reduce one or more of these disk access components.

  • Disk Configurations

    • One of the functions of an OS is to implement a file system. This involves allocating and deallocating disk space and keeping track of space allocated to each file.

    • Partitioning

      • Sometimes it is beneficial to divide a single disk drive in two or more partitions; each partition can be managed separately


Lan operating system functions cont
LAN Operating System Functions (cont.) Afraid to Ask!

  • Single Disk Volume

    • A volume is a logical disk (a partition or collection of partitions) or physical disk that has been formatted and can be used to store data by an OS.

  • Multiple Disk Volumes or Volume Sets

    • Most LAN OSs allow multiple partitions or disks to be combined to form a single logical partition.

    • A volume created from multiple partitions is called a volume set.

  • RAID Level 0—Striping without parity

    • Another capability provided with some LAN OSs is called a Redundant Array of Inexpensive Disks (RAID) Level 0 or striping without parity. Multiple partitions on different disks can be combined to proved a single logical disk; striping with parity differs from a volume just described in that data is written to all partitions simultaneously.


Fault tolerance
Fault Tolerance Afraid to Ask!

  • A LAN with fault tolerance allows the server to survive some failures that would ordinarily be disabling. Fault tolerance usually is provided by a combination of backup hardware components and software capable of using the backup hardware.

  • A level of fault tolerance also can be provided by using redundant arrays of inexpensive disks (RAID). There are six levels of RAID, but for fault tolerance we are concerned only with RAID Level 1 and RAID Level 5.


It s a raid
It’s a RAID! Afraid to Ask!

  • Disk arrays improve performance and redundancy

  • RAID (Redundant Array of Inexpensive Disks) is a method used to write across (stripe) multiple disks to improve performance and fault tolerance

  • RAID 1 and 5 most popular but all have problems


RAID Afraid to Ask!

File

Disk 1

Disk 2

RAID 0--Stripes data between disks

RAID 1--Mirrors data between disks


Mirrored disk drives
Mirrored Disk Drives Afraid to Ask!

Duplexed

Controllers

Controller 1

Controller 2

File 1

File 1

File 2

File 2

2

1


Raid level 5 technology
Raid Level 5 Technology Afraid to Ask!

Server

File 1 Part 1

File 1 Part 2

File 1 Parity

File 1 Part 3

File 2 Part 2

File 2 Part 3

File 2 Part 1

File 1 Parity

1

2

3

4


A fault tolerant duplexed server
A Fault-Tolerant Duplexed Server Afraid to Ask!

Duplexed Servers

Dedicated High-Speed

Connection

Disk Drive

Disk Drive

Mirrored Disk Drives


Backup software
Backup Software Afraid to Ask!

  • The software used to perform the backups is as important as the hardware. Backup software is responsible for reading the files being backed up and writing them to the backup device.

  • Backup devices often come with a backup/restore program (both capabilities are contained on one program), and most LAN system software includes a backup/restore module.

  • Some LAN administrators choose to purchase a separate, more functional backup system than the LAN or backup device versions.


Immediate and recurring costs of a lan
Immediate and Recurring Costs of a LAN Afraid to Ask!

Immediate Costs

Equipment upgrades

Documentation

Installation of cabling

System software installation

Creating user environments

Space required for new equipment

LAN management—personnel costs

Consumable supplies—toner, paper, etc.

Training users, operators, administrators

Site preparation

Hardware installation

Installing applications

Testing

Supplies and spares

Hardware and software maintenance

Training new users, administrators

Recurring Costs


Basic lan management tasks
Basic LAN Management Tasks Afraid to Ask!

User/Group Oriented

Add, delete users and groups

Set user environment

Install/remove printers

Maintain printers

Add/change/delete hardware

Add/change/delete hardware

Plan and implement changes

Make backups

Carry out recovery as necessary

Plan capacity needs

Serve as liaison with other network administrators

Set user/group security

Solve user problems

Setup user/printer environment

Manage print jobs

Establish connections with other networks

Diagnose problems

Maintain operating procedures

Educate users

Monitor the network for problems and to gather statistics for capacity planning

Printer Oriented

Hardware/Software Oriented

General


Backup devices
Backup Devices Afraid to Ask!

  • Removable Disk Drives

    • Manual intervention is necessary for changing disk cartridges, whereas some tape backup system provide tapes with much higher storage capacity and with automatic tape changing.

  • Hard-Disk Drives

    • The arguments for and against this alternative are much the same as those for diskettes. The major difference is that the capacity of hard-disk drives is greater than that of diskettes.


Backup devices cont
Backup Devices (cont.) Afraid to Ask!

  • Optical Disk Drives

    • Optical disk drives are gaining popularity as input, output, and backup devices. The reasons for this are their decreasing costs and large storage capacity.

  • Magnetic Tape Drives

    • A magnetic tape drive is the usual choice for a backup device. Magnetic tapes are less expensive than the other options. They hold large volumes of data, are easy to use and store, and generally provide good performance.


Primary backup technologies
Primary Backup Technologies Afraid to Ask!

1.44 MB

Multiple capacities

40 MB to over 1 G

To 15 GB

160 MB

2.2 GB

To 2.2 GB

To 100 MB

To 4 GB

10-14 GB

2.88 MB

60 MB

500 MB

15 GB

20 MB

150 MB

1.2 GB

70 GB (compressed)

Diskette backup

Hard drive, fixed

Hard drive, removable cartridge

Tape backup, 4mm or 1/4 inch

Tape backup, 8mm or VCR

Tape backup, 9-track

Optical drives

Digital versatile disks (when available)


Backup functions
Backup Functions Afraid to Ask!

Back up all files

Differential backup

Back up all files modified since a particular date

Back up by directory

Back up automatically by time or calendar

Back up all but a list of files to be excluded

Start backup from workstation or server

Back up by interface to a database

Back up using wildcard characters in file names

Incremental backup

Maintain index on tape and disk

Maintain cross-reference of tape serial numbers and backup

Back up manually

Back up by list of files

Back up by index

Compress data

Back up multiple volumes

Generate reports


Gateways
Gateways Afraid to Ask!

  • Gateways operate at the network layer and use network layer addresses in processing messages.

  • Gateways connect two or more LANs that use the same or different (usually different) data link and network protocols. They may connect the same or different kinds of cable.

  • Gateways process only those messages explicitly addressed to them.


Gateways1
Gateways Afraid to Ask!

  • Gateways translate one network protocol into another, translate data formats, and open sessions between application programs, thus overcoming both hardware and software incompatibilities.

  • A gateway may be a stand-alone microcomputer with several NICs and special software, a FEP (Front End Processor) connected to a mainframe computer, or even a special circuit card in the network server.


Gateways2
Gateways Afraid to Ask!

  • One of the most common uses of gateways is to enable LANs that use TCP/IP and Ethernet to communicate with IBM mainframes that use SNA.

  • The gateway provides both the basic system interconnection and the necessary translation between the protocols in both directions.


Gateways3
Gateways Afraid to Ask!


Classic SNA Architecture Afraid to Ask!



LAN-based SNA Gateways Afraid to Ask!



TCP/IP Encapsulation Afraid to Ask!


Switched media technologies
Switched Media Technologies Afraid to Ask!

  • Over the past few years, there has been a major change in the way we think about LANs and backbone networks. LANs have traditionally used multipoint circuits, and WANs have traditionally used point-to-point circuits.

  • As the shared circuits in LANs and BNs (Backbone Networks) have become overloaded with traffic, networks are starting to use switched point-to-point circuits rather than shared multipoint circuits.


Switched ethernet
Switched Ethernet Afraid to Ask!

  • The concept behind switched ethernet - and all switched media technologies - is simple; replace the LAN hub with a switch. Each computer now has its own dedicated point-to-point circuit.

  • Switched ethernet dramatically improves LAN performance. However, since much of the network traffic is to and from the server, the circuit to the server is often the network bottleneck.


Switched ethernet1
Switched Ethernet Afraid to Ask!


Switched ethernet2
Switched Ethernet Afraid to Ask!

  • One obvious solution is to increase the number of connections from the server to the switch so that traffic now can reach the server on several circuits.

  • Other solutions include:

    • Full Duplex Ethernet (full duplex over traditional 10Base-T).

    • 10/100 Switched Ethernet (combines 10Base-T and 100Base-T). This is often used to provide 10 Mbps to the clients and 100 Mbps to the server.


Full duplex ethernet
Full Duplex Ethernet Afraid to Ask!


Switched ethernet3
Switched Ethernet Afraid to Ask!

Switched Ethernet at Fish & Richardson


Switched ethernet site networks

Switched Ethernet Site Networks Afraid to Ask!

No Maximum Distance Spans

Hierarchies and Single Possible Paths

High Speeds and Low Prices


Ethernet switched networks
Ethernet Switched Networks Afraid to Ask!

There are Distance Limits Between

Pairs of Switches

  • 100 meters with UTP

  • Longer with optical fiber

Ethernet

Switch

Maximum

Separation

100 m with UTP

Longer with optical fiber


Hierarchies
Hierarchies Afraid to Ask!

Ethernet Switches Must be Arranged in a Hierarchy

  • Root is the top-level

Root

Ethernet

Switch


Hierarchies1
Hierarchies Afraid to Ask!

  • Usually, Fastest Switches are at the Top (Root)

100Base-X

Building Switch

Gigabit

Ethernet

Campus

Switch

10Base-T

Workgroup

Switch


Hierarchies2
Hierarchies Afraid to Ask!

Vulnerable to Single Points of Failure

  • Switch or Link (trunk line between switches)

  • Divide the network into pieces

X

X

Ethernet

Switch


Hierarchies3
Hierarchies Afraid to Ask!

Single Possible Path Simplifies Switch Forwarding Decisions

  • When frame arrives, only one possible output port (no multiple alternative routes to select among)

  • Switch sends frame out that port

Simple

Forwarding

Decision

Ethernet

Switch


Hierarchies4
Hierarchies Afraid to Ask!

Switches allow only a single path for each MAC destination address

  • Associated with a single port on each switch

  • So switch forwarding table has one and only one row for each MAC address

Ethernet

Switch

Address

A3..

B2..

Port

3

5


Hierarchies5
Hierarchies Afraid to Ask!

Ethernet switch only has to find the single row that matches the destination MAC address

  • Only has to examine half the rows on average; less if the table is alphabetized

  • Comparison at each row is a simple match of the frame and row MAC addresses

Address

A3..

B2..

Port

3

5


More on switched ethernet

More on Switched Ethernet Afraid to Ask!

Switch Learning

Purchase Considerations

VLANs

Intelligent Switched Network Design



Switch learning
Switch Learning Afraid to Ask!

  • Switch Forwarding Table has Address-Port Pairs

  • Manual Entry is Too Time Consuming

    • Many addresses

    • Addresses change

  • Solution: Learn addresses automatically

Address

A3..

B2..

Port

3

5


Switch learning1
Switch Learning Afraid to Ask!

Every Few Minutes, Switch Erases Switch Forwarding Table

  • To eliminate obsolete information

  • Relearning is very fast

Ethernet

Switch

Address

Port

Erased

A1

BF

C9


Switch purchasing decisions
Switch Purchasing Decisions Afraid to Ask!

Maximum Number of MAC address-port entries

  • Small switches may not be able to store many MAC addresses

  • For addresses that cannot be stored, switch must act like a hub, broadcasting and so creating latency

Address

A1

C9

Port

1

5


Switch purchasing decisions1
Switch Purchasing Decisions Afraid to Ask!

Queue Size

  • Incoming frames are placed in queues if they cannot be processed immediately

    • May have several queues

  • If queues are too small, frames will be lost during brief peak loads

Frames

Input

Ports

Queues

Switch

Matrix

Output

Ports


Switch purchasing decisions2
Switch Purchasing Decisions Afraid to Ask!

Switching Matrix

  • Receives input from multiple input ports, via queues

  • Switches each frame to the correct output port

Switch Matrix

Frames

Input

Ports

Queues

Output

Ports


Switch purchasing decisions3
Switch Purchasing Decisions Afraid to Ask!

Reliability through Redundancy

  • Redundant power supplies and cooling fans

  • May even have redundant switch matrix for backup

Frames

Input

Ports

Queues

Switch

Matrix

Output

Ports


Switch purchasing decisions4
Switch Purchasing Decisions Afraid to Ask!

Manageability

  • Can be managed remotely from the network administrator’s desk

    • Network administrator can check on status of switch

    • Network administrator can modify how the switch functions

  • Remote management greatly reduces labor

Frames

Input

Ports

Queues

Switch

Matrix

Output

Ports


Multiple access
Multiple Access Afraid to Ask!


Network segmentation
Network Segmentation Afraid to Ask!


Network segmentation1
Network Segmentation Afraid to Ask!


Switch connections
Switch Connections Afraid to Ask!


Dedicated segments
Dedicated Segments Afraid to Ask!


Routing Types Afraid to Ask!


Routing and addresses
Routing and Addresses Afraid to Ask!



Router Installations Afraid to Ask!



Ip address classes
IP Address Classes Afraid to Ask!


Ip address instruction
IP Address Instruction Afraid to Ask!


Masks
Masks Afraid to Ask!

  • IP Addresses are Always Paired with a Second 32-bit Number Called a Mask

  • Two Types: Network Masks and Subnet Masks

    • Network Mask Tells the Length of the Network Part

    • Subnet Mask Tells the length of the Network Plus Subnet Parts (not just subnet part)

    • IP Address will be paired with one or the other, but not both simultaneously


Using subnet masks
Using Subnet Masks Afraid to Ask!




Osi networking model
OSI Networking Model Afraid to Ask!

Provide network

services

To OS through

network client

Layer 7

Application

Application & OS

Network Client

Application & OS

Data compression

& decompression; data

Encryption/decryption

Layer 6

Presentation

54321

12345

Connection between

Client & server

Layer 5

Session

Session

Packet control

& sequencing error

control

Layer 4

Transport

Packets

Packet construction,

Transmission, &

reception

Layer 3

Network

Data Packet with Header & Trailer

Bit stream connection

protocol

Layer 2

Data Link

Network card & drivers

Network Wiring &

specifications

Layer 1

Physical


Protocols
Protocols Afraid to Ask!

  • A protocol is a standard for communication between peer processes, that is, processes at the same layer, but on different machines

    • HTTP: Browser and webserver application programs are at the same layer but on different machines

Message

App

HTTP

App


Protocols1
Protocols Afraid to Ask!

  • A protocol is a standard for communication between peer processes, that is, processes at the same layer, but on different machines

    • TCP, IP, and PPP all have “protocol” as their final “P;” they are all protocols

    • TCP (Transmission Control Protocol) is the protocol governing communication between transport layer processes on two hosts

Message

Trans

TCP

Trans


Layered communication

Layered Communication Afraid to Ask!

Layers work together

Encapsulation and De-encapsulation


Indirect communication
Indirect Communication Afraid to Ask!

  • Application programs on different machines cannot communicate directly

    • They are on different machines!

HTTP Request

Browser

Web App

Trans

Trans

Int

Int

DL

DL

Phy

Phy

User PC

Webserver


Layer cooperation on the source host
Layer Cooperation on the Source Host Afraid to Ask!

  • Application layer process passes HTTP-request to transport layer process

Application

HTTP Request

Transport

Internet

Data Link

User PC

Physical


Layer cooperation on the source host1
Layer Cooperation on the Source Host Afraid to Ask!

  • Transport layer makes TCP segments

    • HTTP message is the data field

    • Adds TCP header fields shown earlier

    • Transport process “encapsulates” HTTP request within a TCP segment

TCP Segment

HTTP Request

TCP-H

Data

Field

TCP

Header


Encapsulation
Encapsulation Afraid to Ask!

  • Encapsulation is delivering a message in the data field of another message

    • TCP encapsulates HTTP request messages

    • Can also encapsulate other types of messages

TCP Segment

HTTP Request

TCP-H

Data

Field

TCP

Header


Layer cooperation on the source host2
Layer Cooperation on the Source Host Afraid to Ask!

  • Transport layer process passes the TCP segment down to the internet layer process

Application

Transport

TCP segment

Internet

Data Link

User PC

Physical


Layer cooperation on the source host3
Layer Cooperation on the Source Host Afraid to Ask!

  • Internet Layer Process Encapsulates TCP Segment within an IP packet

    • An IP packet to deliver a TCP segment has a TCP segment in its data field

Data IP Packet

TCP segment

IP-H

Data

Field

IP

Header


Layer cooperation on the source host4
Layer Cooperation on the Source Host Afraid to Ask!

  • The internet layer process passes the IP packet to the data link layer process

    • Internet layer messages are called packets

Application

Transport

Internet

IP packet

Data Link

User PC

Physical


Layer cooperation on the source host5
Layer Cooperation on the Source Host Afraid to Ask!

  • Data Link Layer Encapsulates IP Packet Within a PPP Frame

    • Data link layer messages are called frames

    • Data PPP frame has IP packet in data field

PPP Frame Encapsulating an IP Packet

PPP-T

IP packet

PPP-H


Layer cooperation on the source host6
Layer Cooperation on the Source Host Afraid to Ask!

  • The data link layer process passes the PPP frame to the physical layer process, which delivers it to the physical layer process on the first router, one bit at a time (no message at the physical layer)

Application

Transport

Internet

To first

router

Data Link

PPP frame

User PC

Physical (10110 …)


Layer cooperation on the source host7
Layer Cooperation on the Source Host Afraid to Ask!

  • Recap: Adding Headers and Trailers:

Application

HTTP msg

Transport

HTTP msg

TCP-H

Internet

HTTP msg

TCP-H

IP-H

Data Link

PPP-T

HTTP msg

TCP-H

IP-H

PPP-H

User PC

Physical


Layer cooperation on the source host8
Layer Cooperation on the Source Host Afraid to Ask!

  • Encapsulation in Layering

    • Whenever a process at Layer N (the application, transport, internet, or data link layer) creates a message,

    • That Layer N process passes the message down to the next-lower-layer process, the process at layer N-1

    • The N-1 process encapsulates the Layer N message by placing it in the data field of a Layer N-1 message and adding headers and perhaps trailers to create the full Layer N-1 Message


Layer cooperation on the source host9
Layer Cooperation on the Source Host Afraid to Ask!

  • Small but important detail on naming

  • Layer 3 (internet) messages are called packets

    • IP message is a packet

  • Layer 2 (data link) messages are called frames

    • PPP message is called a frame


Layer cooperation destination host

User PC Afraid to Ask!

Physical

Webserver

Layer Cooperation: Destination Host

  • Destination host reverses processes on the sending host

    • Delivers HTTP message to the webserver application program

Application

Transport

Internet

Data Link


Layer cooperation destination host1

Final Router Afraid to Ask!

Physical

Webserver

Layer Cooperation: Destination Host

Data link layer program processes the data link frame’s header and trailer, deencapsulates the IP packet, and passes the IP packet to the next higher layer, the internet layer

  • Successively pass up layer messages

Application

Transport

IP-Packet

Internet

DL-Frame (protocol unknown)

containing IP packet in data field

Data Link


Layer cooperation destination host2

Final Router Afraid to Ask!

Physical

Webserver

Layer Cooperation: Destination Host

  • Successively pass up layer messages

    • Other layers pass successive data fields (containing next-layer messages) up to the next higher layer

HTTP msg

Application

TCP segment

Transport

IP-Packet

Internet

DL-Frame (protocol unknown)

Data Link


Layer cooperation destination host3

Final Router Afraid to Ask!

Physical

Webserver

Layer Cooperation: Destination Host

  • Successively pass up layer messages

    • Other layers process headers & trailers, pass up message in data field

HTTP msg

Application

HTTP msg

TCP

segment

HTTP seg

TCP-H

Transport

HTTP msg

TCP-H

IP-H

Internet

IP Packet

PPP-T

HTTP msg

TCP-H

IP-H

PPP-H

Data Link



Layer cooperation on the first router
Layer Cooperation on the First Router Afraid to Ask!

  • So far, we have only looked at hosts

    • But deencapsulation and encapsulation also occur on EACH router

  • Frame arrives at a port on the first router

    • Port’s data link layer process receives the PPP frame containing an IP packet

Internet

PPP Frame

Data Link

Data Link

First Router


Layer cooperation on the first router1
Layer Cooperation on the First Router Afraid to Ask!

  • Incoming Data Link Process on the Router

    • Deencapsulates the IP packet from the PPP frame

    • Passes the IP packet to the router’ internet layer process

First Router

Internet

IP Packet

Data Link

Data Link

Incoming Port on First Router


Layer cooperation on the first router2
Layer Cooperation on the First Router Afraid to Ask!

  • Routers only have physical, data link, and internet layer processes

    • So internet layer process is the highest-layer process on a router for router forwarding

    • Internet layer process decides where to send the packet next: another router or the destination host

Internet

Data Link

Data Link

First Router


Layer cooperation on the first router3
Layer Cooperation on the First Router Afraid to Ask!

  • Internet layer process passes IP packet to data link layer process on the selected output port that will carry the IP packet to the next router or the destination host

First Router

Internet

IP Packet

Data Link

Data Link

Selected Output Port on First Router


Layer cooperation on the first router4
Layer Cooperation on the First Router Afraid to Ask!

  • The data link and physical layer process on the selected port sends the frame encapsulating the IP packet onto the next router (or destination host)

Internet

Internet

Data Link

Data Link

Frame

Selected Output Port

On First Router

Physical

Layer

Input Port

On Next Router

(Or Destination Host)


Layer cooperation on the first router5
Layer Cooperation on the First Router Afraid to Ask!

  • For router forwarding, routers only use physical, data link, and internet processes

  • Routers First Receive Frames

    • Receiving interface deencapsulates the IP packet, passes the packet to the internet layer process

  • Routers Then Send Frames Out

    • On a different output interface (port)

    • This requires encapsulating of the IP packet in a data link layer frame


Domain name system dns
Domain Name System (DNS) Afraid to Ask!

  • Subtlety

    • Organizations or ISPs have local DNS hosts

    • These hosts must know only local host names and IP addresses

    • For other host names, local DNS host passes request to another DNS host

User PC

Internet

Layer

Process

Local

DNS

Host

Remote

DNS

Host


Domain name system dns1
Domain Name System (DNS) Afraid to Ask!

  • Subtlety

    • Remote DNS host passes information back to the local DNS host

    • Local DNS host passes information back to user PC

    • Browser only talks to local DNS host

User PC

Internet

Layer

Process

Local

DNS

Host

Remote

DNS

Host


Autoconfiguration
Autoconfiguration Afraid to Ask!

  • Every computer attached to the Internet is a host

    • Including desktop PCs

  • Every host must have an IP address

  • Some hosts, such as routers and webservers, get permanent IP addresses

    • So that they can be found easily


Autoconfiguration1
Autoconfiguration Afraid to Ask!

  • User PCs do not need permanent IP addresses

    • They only need to be found within a use session

    • They usually are given temporary IP addresses each time they use the Internet

    • They may get a different IP address each time they use the Internet


Autoconfiguration2
Autoconfiguration Afraid to Ask!

  • Request-Response Cycle

    • User software requests IP address for the user PC in Autoconfiguration Request message

    • Autoconfiguration Response message contains temporary IP address to use in current session

Autoconfiguration

Request

User PC

Autoconfiguration

Host

Temporary

IP Address in

Autoconfiguration Response


Autoconfiguration3
Autoconfiguration Afraid to Ask!

  • Most popular autoconfiguration protocol is DHCP

    • Dynamic Host Configuration Protocol

    • Built into Windows after Win 3.1

    • Supplies host with temporary IP address

  • DHCP can give more information too

    • Usually gives IP address of a default gateway (Microsoft terminology for router)

    • Can give IP address of a local DNS host

    • Can give other information


FDDI Afraid to Ask!

  • Based on the token ring design using 100 Mbps fiber connections.

    • Allows for two concentric rings - inner ring can support data travel in opposite direction or work as backup.

    • Token is attached to the outgoing packet, rather than waiting for the outgoing packet to circle the entire ring.


Gigabit ethernet ieee802 3z
Gigabit Ethernet (IEEE802.3z) Afraid to Ask!

  • Similar to 100Base-X, 1000Base-X is a set of standards that provide 1 Gbps. One problem with 1000Base-X is that using the standard CSMA/CD media access control on a shared network may cause problems.

  • For this reason, gigabit ethernet may remain primarily a backbone technology for use only in point-to-point full duplex data communications links.


Fast Ethernet at GMAC Afraid to Ask!


Fiber distributed data interface fddi
Fiber Distributed Data Interface (FDDI) Afraid to Ask!

  • FDDI is a token-passing ring network that operates at 100 Mbps over two-counter-rotating fiber optic cable rings.

  • It will support up to 500 stations

    on each ring


Topology1
Topology Afraid to Ask!

  • The FDDI standard assumes a maximum of 1000 stations and a 200k path that requires a repeater every 2k. The second ring is for backup.

  • Single attachment stations (SAS) and dual-attachment stations (DAS) are both computer that can connect to one or both of the rings, respectively.

  • If the cable in the FDDI ring is broken, the ring can still operate in a limited fashion.


Topology2
Topology Afraid to Ask!


Ring wrapping
Ring-Wrapping Afraid to Ask!


SAS Afraid to Ask!

DAS


Fddi and fault tolerance
FDDI and Fault Tolerance Afraid to Ask!

  • Dual ring--ring wrapping (works for 1 failure, only)

  • Optical by-pass— mirrors reflect light back by-pass failed device

  • Dual-homing—dual concentrators with one active and the other inactive


Ethernet virtual lans
Ethernet Virtual LANs Afraid to Ask!

Broadcasting

  • Sometimes, station needs to send a frame to all other stations; this is broadcasting

  • For example, servers send a frame to advertise their presence with a broadcast message every minute or so


Ethernet virtual lans1
Ethernet Virtual LANs Afraid to Ask!

  • Broadcasting with Ethernet Switches

    • Broadcaster sets the destination MAC address to all ones (48 ones)

    • When switch sees this address, it broadcasts frame out all stations

    • All stations read frames with this address

Ethernet

Switch

Broadcast

Frame


Ethernet virtual lans2
Ethernet Virtual LANs Afraid to Ask!

Broadcasting is a Problem in Large Switched Networks

  • Server broadcasts go to all stations, creating a great deal of network traffic

  • Create congestion

Broadcast

Frame


Ethernet virtual lans3
Ethernet Virtual LANs Afraid to Ask!

Ethernet switches do implement multicasting

  • A server and the clients it serves are treated as a single virtual LAN (VLAN)

  • Can only communicate among themselves, as if they were on their own LAN

Marketing

VLAN Server

Frame

Marketing

VLAN Client


Ethernet virtual lans4
Ethernet Virtual LANs Afraid to Ask!

VLAN Benefits

  • VLANs reduce traffic on the switched network

  • Other benefits

    • They provide weak security because clients cannot reach all servers (easily defeated but good first line of defense)

    • VLANs give ease of management because if a user changes organizational membership, VLAN membership is easily changed centrally

New


Bad switch organization
Bad Switch Organization Afraid to Ask!

  • One Server for All Clients

    • All traffic goes to and from server

    • Bottlenecks: no simultaneous conversations

    • No major benefits compared to hub

Bottleneck

Ethernet

Switch


Bad switch organization1
Bad Switch Organization Afraid to Ask!

  • Multiple Servers for Clients

    • Allows simultaneous conversations

    • Brings switching’s main benefit

Ethernet

Switch


Early site networks
Early Site Networks Afraid to Ask!

Organization

  • LANs (subnets) based on hubs

  • Routers link hubs

  • Hierarchy of Routers

Router

Hub


The switching revolution
The Switching Revolution Afraid to Ask!

Switches Push Routers to the Edge

  • Router still needed at the edge of the site network to communicate with outside world because routers handle expensive long-distance links very well

External

Switch


The switching revolution1
The Switching Revolution Afraid to Ask!

Layer 3 Switches

  • Traditional switches operate at Layer 2; Switch based on MAC addresses

  • Layer 3 switches switch based on internet layer IP addresses

External

Layer 3

Switch


The switching revolution2
The Switching Revolution Afraid to Ask!

Layer 3 Switches

  • Layer 3 switches are replacing many Layer 2 switches in site networks because of their ability to switch based on IP addresses

External

Layer 3

Switch


The switching revolution3
The Switching Revolution Afraid to Ask!

Layer 3 Switches versus Routers

  • Layer 3 switches are much faster than routers

  • Layer 3 switches cost less than routers

External

Layer 3

Switch


The switching revolution4
The Switching Revolution Afraid to Ask!

Layer 3 Switches versus Routers

  • Layer 3 switches rarely support Layer 2 WAN protocols

  • Routers usually are still needed at the edge of the site network, to communicate with external links

External

Layer 3

Switch


The switching revolution5

Routers Afraid to Ask!

Forward based on IP addresses and other internet layer addresses

Expensive and slow

Handle multiple internet layer protocols

Handle multiple LAN and WAN subnet protocols

Layer 3 Switches

Forward based on IP addresses, sometimes IPX addressesInexpensive and Fast

Do not handle multiple internet layer protocols

Do not handle multiple LAN and WAN subnet protocols

The Switching Revolution


The switching revolution6
The Switching Revolution Afraid to Ask!

Layer 4 Switches

  • Examine port fields in TCP and UDP

  • These fields describe the application

  • Therefore, can switch based on application (to give priority by application, etc.)

Layer 4

Switch


Congestion latency and remedies

Congestion, Latency, and Remedies Afraid to Ask!

Peak Loads

Congestion and Latency

Overprovisioning Capacity

Priority

Quality of Service

Traffic Shaping


The peak load problem
The Peak Load Problem Afraid to Ask!

  • Capacity Sufficient Most of the Time

    • Otherwise, get bigger switches and trunk lines!

  • BriefTraffic Peaks can Exceed Capacity

    • Frames will be delayed in queues or even lost if queue gets full

Traffic

Peak

Capacity


Overprovisioning
Overprovisioning Afraid to Ask!

Overprovisioning: Install More Capacity than Will be Needed Nearly All of the Time

Wasteful of capacity

Still, usually the cheapest solution today because of its simplicity

Overprovisioned Capacity

Traffic

Peak


Priority
Priority Afraid to Ask!

Assign Priorities to Frames

  • High priority for time-sensitive applications (voice)

  • Low priority for time-insensitive applications (e-mail)

  • In traffic peaks, high-priority frames still get through

  • Low-priority applications do not care about a brief delay for their frames

Low-Priority Frame

Waits Briefly

High-Priority

Frame Goes


Bridges
Bridges Afraid to Ask!

  • A bridge can be used to connect two similar LANs, such as two CSMA/CD LANs.

  • A bridge can also be used to connect two closely similar LANs, such as a CSMA/CD LAN and a token ring LAN.

  • The bridge examines the destination address in a frame and either forwards this frame onto the next LAN or does not.

  • The bridge examines the source address in a frame and places this address in a routing table, to be used for future routing decisions.



Bridges interconnect
Bridges Interconnect Afraid to Ask!


Connecting lans
Connecting LANs Afraid to Ask!


Bridges connect similar
Bridges Connect Similar Afraid to Ask!


Bridge Installations Afraid to Ask!


Bridge switch combo
Bridge & Switch Combo Afraid to Ask!


Frames are converted
Frames Are Converted Afraid to Ask!



Storage Area Network Afraid to Ask!





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