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

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26 SONET vs. Gigabit Ethernet 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 SONET vs. Gigabit Ethernet

28 SONET vs. Gigabit Ethernet Gigabit Ethernet, however, does not have all the levels, making the technology much simpler and much less expensive

29 SONET vs. Gigabit Ethernet

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 LAN Experience 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 seconds for layer 2 bridging/switching (5 seconds in future) Reliability –99.99% migrating to % by mid 2001

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