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TDC 363 Local Area Networks Metropolitan Area Networks (MAN) 1 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 2 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 3 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 4 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 5 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 6 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 7 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 8 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 9 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 10 Support Technologies • • • • • • SONET/SDH ATM Gigabit Ethernet IP Fibre Channel FDDI 11 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 12 Support Technology - SONET • SONET disadvantages: – Still fairly expensive – Problems adapting data services to the voicedesigned and voice-optimized hierarchy – Inflexible multiplexing hierarchy (SONET increments in terms of DS-0s / DS-1s) – SONET cannot be provisioned dynamically 13 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 14 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 15 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? 16 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 17 Support Technology - FDDI • Basically a legacy technology • Being replaced by Gigabit Ethernet or ATM • Can be transparently transported over the optical layer using DWDM 18 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 19 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 20 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 21 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 22 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 23 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) 24 25 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 26 SONET vs. Gigabit Ethernet 27 SONET vs. Gigabit Ethernet • Gigabit Ethernet, however, does not have all the levels, making the technology much simpler and much less expensive 28 SONET vs. Gigabit Ethernet 29 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 30 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 31 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 32 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 33 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 34 Yipes - QoS • Hardware – equipment has separate queues and can prioritize frames • Can prioritize at IP layer – Based on IETF’s Diff-Serv 35 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 36 37