1 TDC 363 Local Area Networks Metropolitan Area Networks (MAN)

1

TDC 363 Local Area Networks

Metropolitan Area Networks (MAN)

2

MAN Definition

• Not a precise definition available

• Somewhere between a LAN and a WAN with some features of each

• Serves a geographic area larger than a LAN, such as a city or metropolitan region

3

Definition Continued

• MANs can interconnect various sites for one company, or interconnect many companies

• MANs transfer data at LAN speeds (and higher) but often use more complicated protocols

4

MAN Application Areas

• Interconnection and consolidation of corporate data centers

• Transparent extension of the LAN by interconnecting distributed corporate locations

• Support of SAN (storage area networks)

• Server-less offices

5

MAN Application Areas

• Real-time transaction backups

• High-speed disaster recovery

• Interconnection between corporate data center and ISP

• Government, business, medicine and education high-speed interconnections

6

SANs

• Latest evolution of mass data storage for large corporations and institutions

• Normally data storage is attached to the LAN via a server

• But with a SAN high-volume disk arrays and tape storage occupy a network separate, but connected to, a LAN

7

MAN Features

• Why use a MAN?

• Very high speeds (Gbps possible)

• Self-healing networks

• Bandwidth on demand

• MANs cover distances that LANs cannot

• But MANs often provide a lower level of complexity than many WANs

8

MAN Topologies

• Point-to-point– Characterized by very high speeds (10 to 40

Gbps)– Often DWDM over fiber– Redundancy is provided at the card level -

parallel fiber links with redundant equipment at the endpoints

9

MAN Topologies

• Ring– Most common architecture– Can span tens of kilometers– Data rates range from 622 Mbps to 10 Gbps per

channel– SONET rings a typical example– Multiple rings with very fast failover provide

stability

10

MAN Topologies

• Mesh– The future of MANs?– A natural extension of point-to-point MANs– Can also connect to established rings– High speeds, long distances, good redundancy

11

Support Technologies

• SONET/SDH

• ATM

• Gigabit Ethernet

• IP

• Fibre Channel

• FDDI

12

Support Technology - SONET

• Currently most MANs are supported by SONET rings

• SONET is the fundamental transmission technology for both TDM-based circuit switched networks, and most overlay data networks

• Unfortunately, SONET has a number of shortcomings

13

Support Technology - SONET

• SONET disadvantages:– Still fairly expensive– Problems adapting data services to the voice-

designed and voice-optimized hierarchy– Inflexible multiplexing hierarchy (SONET

increments in terms of DS-0s / DS-1s)– SONET cannot be provisioned dynamically

14

Support Technology - ATM

• Favored by many service providers because it can support different protocols and different traffic types into a common protocol format for transmission over SONET

• Unfortunately, ATM is complex, costly, and provides an extra layer of complexity

15

Support Technology - Gigabit Ethernet

• A very interesting newcomer to MAN technology

• A very common and well-understood technology

• Can scale from 10 Mbps, 100 Mbps, 1000 Mbps, to 10 Gbps easily

• Low cost• No need for ATM or SONET

16

Support Technology - IP

• Almost entire data world uses IP

• Also well known, widely adopted, reasonably flexible, relatively simple

• IP is a layer 3 protocol, so question is IP over ATM over SONET? IP over SONET? IP over Ethernet?

17

Support Technology - Fibre Channel

• Predominant data link technology used in SANs

• Economical replacement for SCSI• Interfaces available at 100 MBps with 200

MBps soon and 400 MBps testing• Does not have a short distance limitation

like SCSI• Found in point-to-point, mesh, and

arbitrated loops

18

Support Technology - FDDI

• Basically a legacy technology

• Being replaced by Gigabit Ethernet or ATM

• Can be transparently transported over the optical layer using DWDM

19

SONET vs. Gigabit Ethernet

• Let’s examine the two more interesting support technologies

• Why more interesting?– SONET is the ruler– Gigabit Ethernet is trying to dethrone that ruler

20


• Ethernet is 10 times less expensive than current SONET technology

• Ethernet is a simple and widely understood technology

• Ethernet is the best technology for carrying IP traffic - IP and Ethernet have matured together

21


• Optical Ethernet can support links in the network range from 3 to 6+ miles using single mode 1310 nm wavelength and up to 43.4 miles for 1550 nm wavelength

• Optical Ethernet can segregate traffic of different users and deliver the particular service level each user purchases

22


• Traffic segregation is accomplished by using the IEEE 802.1pQ VLAN standard

• With this standard, each user’s frame is marked with a VLAN tag as it enters the network

• This tag keeps each user’s traffic separate as it crosses the network

23


• Optical Ethernet can also deliver guaranteed levels of latency, jitter, and bandwidth

• To provide these levels of latency and jitter, IETF created the Differentiated Services (Diff-Serv) project

• Diff-Serv - as each frame enters a network, information from the frame is used to assign it to a particular class of service

24


• User contracts also specify bandwidths, which network operators guarantee by limiting the aggregate of guarantees to network capacity (similar to frame relay and ATM)

25

26


• One of the big advantages of Gigabit Ethernet over SONET is the levels of complexity

• SONET has multiple layers - the router network running over the ATM network running over the SONET network running over a collection of point-to-point DWDM links

27


28


• Gigabit Ethernet, however, does not have all the levels, making the technology much simpler and much less expensive

29


30

Yipes…that’s fast!

• 15 months old (as of Fall 2000)

• Up and running in 20 cities

• A “disruptive” approach to networking

• The first fully managed, all-IP regional optical networks using Gigabit Ethernet for linking businesses to eadch other and to the Internet

31

Yipes…that’s fast!

• Fully scalable bandwidth-on-demand from 1 Mbps up to 1 Gbps in 1 Mbps increments

• Busting the regional bandwidth bottleneck between corporate LANs and cross-country fiber networks to drive a new generation of bandwidth-intensive applications

• Unprecedented levels of customer control via the Yipes Care Service Portal

32

Yipes - Typical Regional Network

• Diversely sourced dark fiber

• Concatenated local access loops

• Less than 10 ms latency regional ring

• Multiple peering arrangements

• Several WAN connections

• 24x7 redundant monitoring

33

Yipes - Extending the LANExperience

• Fiber to business locations

• Familiar computing environment

• Granular bandwidth increments - 1 Mbps to 1 Gbps in 1 Mbps increments

• Scalability on demand - no “forklift upgrade” - upgrade with a phone call, and soon with via a Web site

34

Yipes - QoS

• Traffic engineering– know bandwidth at access points and in metro

network for all customers– no over subscribing

• IEEE standard (802.1pQ) for VLANs– identify customer packets with different tags– prioritize packets

35

Yipes - QoS

• Hardware– equipment has separate queues and can

prioritize frames

• Can prioritize at IP layer– Based on IETF’s Diff-Serv

36

Yipes - Security, Survivability and Reliability

• Security– Layer 2 switching using VLAN tags based on IEEE

802.1q/p

• Survivability– Dual fiber entrance to customer premises

– Failover• 2-3 seconds for layer 3 routing

• 30 - 40 seconds for layer 2 bridging/switching (5 seconds in future)

• Reliability– 99.99% migrating to 99.999% by mid 2001

37

Documents

1 TDC 363 Local Area Networks Metropolitan Area Networks (MAN)