TDC 363 Local Area Networks

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)

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 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