Transcript Gavin

Leased Lines
vs.
Internet Based VPNs
Presented By:
Gavin Worden
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 Lines
T-Carrier System &
Synchronous Optical Network
Leased Line Implementations:
• Private Point-to-Point
• Frame Relay
T-Carrier System
Originally 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
Table 1
North American Hierarchy
Transmission
Number of
Designator
Rate
Voice Channels
DS-0
64 Kbps
1
T-1
(DS-1)
1.544 Mbps
24
T-1C
(DS1C)
3.152 Mbps
48
T-2 (DS-2)
6.312 Mbps
96
T-3 (DS-3)
44.736 Mbps
672
T-4 (DS-4)
274.176 Mbps
4032
Table 1
SONET
In 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
Table 2
SONET/SDH Digital Hierarchy
Optical
Level
OC-1
OC-3
OC-9
OC-12
OC-18
OC-24
OC-36
OC-48
OC-96
OC-192
Electrical Line Rate
Payload
Overhead Rate
SDH
Level
(Mbps) Rate (Mbps)
(Mbps)
Equivalent
STS-1
51.84
50.112
1.728 STS-3
155.52
150.336
5.184 STM-1
STS-9
466.56
451.008
15.552 STM-3
STS-12
622.08
601.344
20.736 STM-4
STS-18
933.12
902.016
31.104 STM-6
STS-24
1244.16
1202.688
41.472 STM-8
STS-36
1866.24
1804.032
62.208 STM-13
STS-48
2488.32
2405.376
82.944 STM-16
STS-96
4976.64
4810.752
165.888 STM-32
STS-192
9953.28
9621.504
331.776 STM-64
OC-9, OC-18, OC-24, OC-36, OC-96 are considered orphaned rates.
Table 2
Private Point-to-Point
A 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 Relay
Frame 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 Networks
To 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 VPN
Rather 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 Alternatives
In 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 1
Private 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 2
Frame 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 3
Internet 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
Conclusion
Major 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?
Leased Lines
vs.
Internet Based VPNs
Presented By:
Gavin Worden