TelecommunicationsNetwork Design

Econets Slide Show

Instructor: Roshan L. Sharma

P.O. Box 822938 Dallas TX 75382(214) 691-6790

ECONETS: Learning Resources

1. Text book: Network Design Using EcoNets, International Thomson Computer Press,1997

2. Slide Show (SS1,SS2,SS3,SS4)3. VCR Tapes for only distance-

learning students.

ECONETS: Learning Resources (Contd.)

1. The Textbook is ideal for an in-depth study of all networking ideas, concepts and equations,

2. The slide show highlights only the main ideas and concepts,

3. The VCR tapes describes the actual hands-on design process for remote students.

CONCEPTS: Networks• Nature provides many examples of

beautiful networks (e.g. human circulatory or a neural networks)

• Humans also create many types of useful networks(e.g broadcast, highways, railroads, freight trucking and oil /gas pipelines)

CONCEPTS: Networks

• Nature provides many examplesof beautiful networks (e.g. humancirculatory or a neural networks)

• Humans also create many types ofuseful networks(e.g broadcast,highways, railroads, freighttrucking and oil /gas pipelines)

CONCEPTS: Networks

• Nature provides many examplesof beautiful networks (e.g. humancirculatory or a neural networks)

• Humans also create many types ofuseful networks(e.g broadcast,highways, railroads, freighttrucking and oil /gas pipelines)

CONCEPTS: Networks

• Nature provides many examplesof beautiful networks (e.g. humancirculatory or a neural networks)

• Humans also create many types ofuseful networks(e.g broadcast,highways, railroads, freighttrucking and oil /gas pipelines)

An Enterprise Network Model

• An typical enterprise network consists ofthe following components:

1. Subscriber (S) nodes (e.g. Phone,WS)

2. Subscriber Lines (SLs)

3. CPE nodes (e.g. PABX, LAN) & SWs

4. Access Lines (ALs) and trunks (TKs)

5. Off-Net ALs (ONALs) to serve offnetsubscribers(ONSs) via public nets (PNs)

Some Models of Enterprise Networks

(On an Informal Basis Only)

Enterprise Network Model

PTN

SW

CPE

TK

AL

SL

CO

TK

ONS

ONAL

SW

PN

PN

CPE

S

A Traditional Public TelephoneNetwork Model

• It consists of many hierarchical ALsand switches

• Examples of links are SLs, 4 levels ofALs and 1-level of Trunks (TKs)

• Examples of switches are centraloffices (COs), Local Tandems (LTs),Tandem SWs (TSWs), Primary SWs,Secondary SWs and Regional SWs.

Traditional PTN Model

CO

TSW

PSW

SSW

RSWTKs

ALs

S

SL

LT

A Modern Public Network (PN)Model

• A modern public network (PN) isa flat network consisting of ALsand trunks connecting accessnodes generally called points ofpresence (POP) and switches.

• Physical layout is different fromthe manner switches are actuallyconnected to route traffic.

Modern Public Network:A Generalized Model

POP

SWALs

POP

TKs

SW

SP-BackBone

SP-POPs

Enterprise BackBone

Enterprise Access SWs

Enterprise CPEs (Hubs,PBXs, LANs)

Sources Destinations

Integrated NMC

Switched Network Architecture

• Networks can be classified by theirarchitectures.

• A network architecture can be definedby following attributes

1. Geographic coverage

2. Network topology

3. Network access technique

4. Switch/Xmission/MPlxg/NMC technology

Modeling A Network:Geographical Coverage

1. Local Area Network (LAN): Oneor more sites over a campus

2. Metropolitan Area Net (MAN):Two or more sites over a city

3. Wide Area Net (WAN):One ormore sites over a state/nation

4. Global Area Net (GAN):One ormore sites over several nations

Modeling A Network:Geographical Coverage

1. Local Area Network (LAN): Oneor more sites over a campus

2. Metropolitan Area Net (MAN):Two or more sites over a city

3. Wide Area Net (WAN):One ormore sites over a state/nation

4. Global Area Net (GAN):One ormore sites over several nations

Modeling A Network:Topological Considerations

• Bus and ring topologies are generallyemployed by data LANs (or LANs)

• Star topologies are generally employedby voice LANs/PBXs and data WANs

• Multidrop(MD) and directed link (DL)topologies are employed in polled SNAand modern PS (e.g. frame relay)networks respectively.

Modeling A Network:Bus Topology of a LAN

BUS

Station

LANs based on the CSMA/CD (orEthernet) and Token Bus technologyemploy a bus topology. Stations sharea bus but CSMA/CD may experiencecollisions at high loads.

Modeling A Network:Ring Topology of a LAN

The Ring Topology is employed by theToken Ring (TR) technology. It allows Nstations to share a ring through the use ofa token mechanism without collisions.

Station1

2

34

5

N

RING

Modeling A Network: StarTopologies for LANs & WANS

• Star topologies are optimum withwith respect to response times.

• Network topologies default to astar one for voice & high-volumedata applications

• Integrated voice, data and imagegenerally require a star topology.

Examples of a Star Topologies:LANs

SW

S

SW= PABX/PS/StarLAN / EtherSwitch

SW

PABX/LAN

S

AL

Example of InterconnectedStar Topologies: WANs

CPE/PABX/LAN

SW/PS/T1-MPLXR

ALs

TKs

• Low-Volume data networks based onSNA use a MD topology. These arecontrolled by a host and use a pollingscheme to share a netlink.

• Many modern PS networks use a DLtopology - several low cost PS nodesshare a DL netlinlk, each PS nodeserves a set of low-volume user nodes.

Multidrop(MD) & DirectedLink (DL) Topologies in WANs

A MD Topology for WANs

TKs

PS or SW PSController/CPE

NetLink branch TK

A DL Topology For WANs

PS or SW PS/Controller/CPE

NetLink branch TK

TKs

Some Additional Words onMD and DL Topologies

1. MD topology is not efficient in termsof link utilization and response time

2. DL topology is quite efficient interms of low response times at highlink utilizations( for FPS application)

3. Dial-up lines may be used to increasethe reliability of a DL topology bymeans of LOOP realizations.

Some Additional Words onMD and DL Topologies

4. A netlink based on the MD topology isgenerally cheaper than that based onthe DL topology since it employs theminimal spanning tree (MST)algorithm to interconnect the alreadyspecified nodes for the netlink.

5. A MST topology with capacityconstraint is difficult to design whenthe number of nodes exceed 20.

Fully-Connected Mesh Topology

It is mainly used to connect N BackBoneSwitches via N(N-1)/2 trunk bundles :

Switched Networks:Access Methods

• There are basically 3 access methods:

1. Demand Access: Uncontrolled butvery responsive for nominal loading

2. Polled Access: Centrally controlled,and relatively slow and inefficient

3. Multi-Access: Fully distributed andfully shared

Access Methods:Demand Access

• According to this scheme, asubscriber goes off-hook, gets adial tone before dialing the callednumber.

• Generally employed by voicenetwork based on CS technology

• Several data networks also usethis method

Access Methods:Polled Access

• According to this scheme (e.g. SNA), aa host polls controllers (each serving aset of users) on a netlink inviting aninput message. Upon its receipt, thehost finally sends the output message.

• Performance suffers when the netlinkwith many controllers is overloaded.

Access Methods:Multi- Access

• According to this scheme, a stationstarts transmission after satisfying aset of network requirements. Duringheavy loading, collisions may occurin some systems.

• Generally employed by LANs (e.g.Ethernet, token ring) although someWANs (e.g. ALOHA) also use it.

Switched Networks:Switching Technology

• Any of the following switchingtechniques can characterize aswitched network:

1. Circuit Switching (CS) or fast CS

2. Packet Switching (PS) or fast PS

3. S/F Message Switching (MS)

4. Fast PS or FPS (e.g. frame relay,SMDS and ATM)

Switching Technology (Contd.)

• Intelligent switches based on any of theabove technologies may or may notprovide the following capabilities:

1. Intelligence used for networkmanagement and control

2. Intelligence used for self-healing

3. Intelligence used to control congestioncaused by either overloads or failures

Transmission Techniques forSwitched Networks

Switched networks may be modeledaccording to the types of transmissionfacilities employed. Some examples:

1. Analog lines ( leased for voice or data)

2. Digital 56/64kbps (leased or switched)

3. T1/T3 (leased/owned/switched)

3. Satellite, digital micro-wave and fiber-optical (leased/owned/switched)

Multiplexing Techniques forSwitched Networks

• Space Division Multiplexing (SDM)technique used for bundling 2/4 wirecircuits into a single bundle

• FrequencyDM for bundling frequencybands into one large one

• TimeDM for combining many bitstreams into a single stream (e.g. T1)

• SONET Syn. Digital Hierarchy (SDH)

Multiplexing Techniques forSwitched Networks (Contd)

Japan

N.America

Europe/CCITT

4032

420

9624

30 120 480 1920

672

57601440

#VGCs/Multipxd Line

T-1 T-2

T-3

CCITT SDH....

OC-NNA SONET.... N=1, 3, 48, 192., OC-1=52Mbps

STM-N N=1, 4, 16, 64., STM-1=OC-3

FIBER MPXG

Class Assignment

Based on the language developed for modeling any network, please model an Advanced Intelligent Network (AIN). You may use any search engine on the Internet but you must convert their description to the ones developed in the class. Please limit the model to one (1) page or less.