Presented By:Gavin Worden

Leased Lines vs.

Internet Based VPNs

Evolution of WAN Technologies

(1)  1837 – Telegraph

(2)  1876 – Telephone

(3)  1960’s - T-carrier system developed by AT&T for internal use.

(4) 1969 - ARAPNET (later becomes Internet) - first packet switching network

(5) 1970’s - Dataphone Digital Service (DDS) started deployment in 1974, bringing digital transmission facilities to the customer's premise.

(6) 1980’s – T-1 services become commercially popular

(7) 1990’s – Frame Relay began Deployment

Leased LinesT-Carrier System &

Synchronous Optical Network

Leased Line Implementations:• Private Point-to-Point

• Frame Relay

T-Carrier SystemOriginally developed by AT&T in the 1960’s for internal use.

Initially used for voice, T1 and T3 lines are widely used to create point-to-point private data networks.

T-carrier lines use four wire cables. One pair is used to transmit and the other to receive

T-Carrier System

DS-0 64 Kbps 1T-1 (DS-1) 1.544 Mbps 24T-1C (DS-

1C) 3.152 Mbps 48T-2 (DS-2) 6.312 Mbps 96T-3 (DS-3) 44.736 Mbps 672T-4 (DS-4) 274.176 Mbps 4032

Table 1

Table 1

North American Hierarchy

DesignatorTransmission

RateNumber of

Voice Channels

SONETIn contrast to the copper transmission lines used for T-carrier systems, the synchronous optical network, or SONET, uses fiber-optic transmission technology.

Employed by telephone companies and common carriers, speeds range from 51 Mbps to 40 Gbps.

SONET backbones are widely used to aggregate T1 and T3 lines”

SONET

Optical Level

Electrical Level

Line Rate (Mbps)

Payload Rate (Mbps)

Overhead Rate (Mbps)

SDH Equivalent

OC-1 STS-1 51.84 50.112 1.728 -OC-3 STS-3 155.52 150.336 5.184 STM-1OC-9 STS-9 466.56 451.008 15.552 STM-3OC-12 STS-12 622.08 601.344 20.736 STM-4OC-18 STS-18 933.12 902.016 31.104 STM-6OC-24 STS-24 1244.16 1202.688 41.472 STM-8OC-36 STS-36 1866.24 1804.032 62.208 STM-13OC-48 STS-48 2488.32 2405.376 82.944 STM-16OC-96 STS-96 4976.64 4810.752 165.888 STM-32OC-192 STS-192 9953.28 9621.504 331.776 STM-64

Table 2

SONET/SDH Digital Hierarchy

OC-9, OC-18, OC-24, OC-36, OC-96 are considered orphaned rates.  

Table 2

Private Point-to-PointA permanent telephone connection between two points set up by a telecommunications common carrier. Typically, leased lines are used by businesses to connect geographically distant offices.

AT&T offers private digital transmission at speeds ranging from 9.6 kbps, 56 Kbps, T1, Channelized DS1, E1, DS3, OC3c, OC12c, OC48c, OC192c, Ethernet and STM-1/STM-4.

This the most expensive option. A prime component of cost is geographic distance of the line.

Frame RelayFrame relay is a telecommunication service designed for cost-efficient data transmission for intermittent traffic between local area networks (LANs) and between end-points in a wide area network (WAN).

Frame Relay networks in the U.S. support data transfer rates at T-1 (1.544 Mbps) and T-3 (45 Mbps) speeds. Frame Relay is a way of utilizing existing T-1 and T-3 lines owned by a service provider. Most telephone companies now provide Frame Relay service for customers who want connections at 56 Kbps to T-1 speeds.

Virtual Private NetworksTo emulate a point-to-point link, data is encapsulated, or wrapped, with a header that provides routing information allowing it to traverse the shared or public transit internetwork to reach its endpoint. To emulate a private link, the data being sent is encrypted for confidentiality.

Network to Network VPNRather than using an expensive long-haul dedicated circuit between the branch office and the corporate hub, both the branch office and the corporate hub routers can use a local dedicated circuit and local ISP to connect to the Internet. The VPN software uses the local ISP connections and the Internet to create a virtual private network between the branch office router and corporate hub router.

Client to Server VPN

Client VPNs differ from network to network VPNs in that the connection for a client VPN is made directly from the client machine to the organization’s VPN concentrator/server instead of from the client’s local network to the organization’s primary network.

Evaluation of AlternativesIn order to adequately evaluate the various WAN alternatives explored in this report, three different WAN scenarios will be examined.

All three scenarios will be outlined from the perspective of a single organization that has ten offices around the world. The organization needs:

•secure internal e-mail•files sharing•intranet•network management•Internet access

Scenario 1Private Point-to-Point to Each Site

• Provides stable & centrally managed WAN.

• Will provide control of bandwidth / performance

• Single interface to Internet

• Higher degree of network security

• All requirements will be met for this scenario

• This option is the most expensive

Scenario 2Frame Relay to Each Site

• Provides stable & centrally managed WAN.

• Will provide control of bandwidth

• Single interface to Internet

• Good degree of network security

• All requirements will be met for this scenario

• This option is the next most expensive

Scenario 3Internet based Network to Network VPN

• Enhanced transport security (encryption)

• Much lower connection costs

• More complex setup and maintenance

• Multiple interfaces with Internet increases security risks

•All requirements met with this scenario

ConclusionMajor Determining Factors Include:

• Performance Requirements

• Security Requirements

• and Cost

High Security / Performance requirements will typically require private point-to-point.

Lower Security / Performance requirements will allow organizations to take advantage of the low costs and flexibility of VPNs.

Questions?

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Presented By:Gavin Worden

Leased Lines vs.

Internet Based VPNs