Local area networking
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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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Local area networking

Local Area Networking

Chapter 8


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


Token ring

Token Ring


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.


Node number access determines type

Node Number/Access Determines Type


Most of the world uses ethernet

Most of the World Uses Ethernet


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


Lans cheaper as nodes increase

LANs Cheaper as Nodes Increase


Break point

Break-point


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

  • 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.)

  • 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

  • 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!

  • 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


Local area networking

RAID

File

Disk 1

Disk 2

RAID 0--Stripes data between disks

RAID 1--Mirrors data between disks


Mirrored disk drives

Mirrored Disk Drives

Duplexed

Controllers

Controller 1

Controller 2

File 1

File 1

File 2

File 2

2

1


Raid level 5 technology

Raid Level 5 Technology

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

Duplexed Servers

Dedicated High-Speed

Connection

Disk Drive

Disk Drive

Mirrored Disk Drives


Backup software

Backup Software

  • 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

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

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

  • 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.)

  • 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

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

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

  • 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

  • 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

  • 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


Local area networking

Classic SNA Architecture


Local area networking

Standalone PC 3270 Terminal Emulation


Local area networking

LAN-based SNA Gateways


Local area networking

SNA/LAN Incompatibilities Yield Multiple Networks


Local area networking

TCP/IP Encapsulation


Switched media technologies

Switched Media Technologies

  • 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

  • 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


Switched ethernet2

Switched Ethernet

  • 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


Switched ethernet3

Switched Ethernet

Switched Ethernet at Fish & Richardson


Switched ethernet site networks

Switched Ethernet Site Networks

No Maximum Distance Spans

Hierarchies and Single Possible Paths

High Speeds and Low Prices


Ethernet switched networks

Ethernet Switched Networks

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

Ethernet Switches Must be Arranged in a Hierarchy

  • Root is the top-level

Root

Ethernet

Switch


Hierarchies1

Hierarchies

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

100Base-X

Building Switch

Gigabit

Ethernet

Campus

Switch

10Base-T

Workgroup

Switch


Hierarchies2

Hierarchies

Vulnerable to Single Points of Failure

  • Switch or Link (trunk line between switches)

  • Divide the network into pieces

X

X

Ethernet

Switch


Hierarchies3

Hierarchies

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

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

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

Switch Learning

Purchase Considerations

VLANs

Intelligent Switched Network Design


How much of a packet does a switch need

How Much of a Packet Does a Switch Need?


Switch learning

Switch Learning

  • 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

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

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

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

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

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

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


Network segmentation

Network Segmentation


Network segmentation1

Network Segmentation


Switch connections

Switch Connections


Dedicated segments

Dedicated Segments


Local area networking

Routing Types


Routing and addresses

Routing and Addresses


Local area networking

Network Address Translation


Local area networking

Router Installations


Local area networking

Routing Evolution Scenarios


Ip address classes

IP Address Classes


Ip address instruction

IP Address Instruction


Masks

Masks

  • 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


Multiple network protocols

Multiple Network Protocols


Standards for web server access

Standards for Web Server Access


Osi networking model

OSI Networking Model

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

  • 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

  • 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

Layers work together

Encapsulation and De-encapsulation


Indirect communication

Indirect Communication

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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

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

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

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

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


Local area networking

Router’s Use of Data-Link and Network Layer Addresses


Layer cooperation on the first router

Layer Cooperation on the First Router

  • 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

  • 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

  • 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

  • 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

  • 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

  • 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)

  • 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)

  • 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

  • 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

  • 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

  • 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

  • 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


Local area networking

FDDI

  • 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)

  • 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.


Local area networking

Fast Ethernet at GMAC


Fiber distributed data interface fddi

Fiber Distributed Data Interface (FDDI)

  • 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

  • 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


Ring wrapping

Ring-Wrapping


Local area networking

SAS

DAS


Fddi and fault tolerance

FDDI and Fault Tolerance

  • 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

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

  • 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

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

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

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

  • 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

  • Multiple Servers for Clients

    • Allows simultaneous conversations

    • Brings switching’s main benefit

Ethernet

Switch


Early site networks

Early Site Networks

Organization

  • LANs (subnets) based on hubs

  • Routers link hubs

  • Hierarchy of Routers

Router

Hub


The switching revolution

The Switching Revolution

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

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

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

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

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

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

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

Peak Loads

Congestion and Latency

Overprovisioning Capacity

Priority

Quality of Service

Traffic Shaping


The peak load problem

The Peak Load Problem

  • 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

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

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

  • 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.


Local area networking

Use of Data-Link Addressing by Bridges


Bridges interconnect

Bridges Interconnect


Connecting lans

Connecting LANs


Bridges connect similar

Bridges Connect Similar


Local area networking

Bridge Installations


Bridge switch combo

Bridge & Switch Combo


Frames are converted

Frames Are Converted


Local area networking

Overall Internetworking Design Strategies


Local area networking

Storage Area Network


Local area networking

Relationship Between the OSI Model and Internetworking Devices


Local area networking

LAN Switches and Virtual LANs


Local area networking

Layer 2 vs. Layer 3 Virtual LANs: An Architectural Comparison


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