Modern Ethernet variations. based on Chapter 5 of CompTIA Network+ Exam Guide, 4th ed., Mike Meyers

Transcription

1 Modern Ethernet variations based on Chapter 5 of CompTIA Network+ Exam Guide, 4th ed., Mike Meyers

2 recap: obsolete versions of Ethernet Coaxial cable physical bus topology 10Base5 (standard IEEE 802.3, 1983) 10Base2 (standard IEEE 802.3a, 1985) Twisted-pair cable physical star topology 10BaseT (standard IEEE 802.3i, 1990) Optical fiber physical point-to-point topology 10BaseFL (standard IEEE 802.3j, 1993) Intended for backbones

3 "Now" a Moving Target

4 Modern Ethernet versions still transport frames, but sometimes with additions Preamble: Dest. MAC 6 octets Src. MAC 6 octets Type / length 2 octets Payload octets Padding? octets FCS 4 octets IFG: 96 bittimes New versions of Ethernet remain "backward compatible" Preamble, IFG change with different versions IEEE 802.1Q VLANs Virtual LANs require an additional header inserted and removed between src-addr and type/length headers by conformant switches Preamble: Dest. MAC 6 octets Src. MAC 6 octets 802.1Q VLAN 2 octets Type / length 2 octets Payload octets Padding? octets FCS 4 octets

5 The first speed increase IEEE 802.3u, 1995 a.k.a. Fast Ethernet; 100Mbps 100Base-TX uses the same two twisted pairs as 10BaseT, requires Cat 5 or better cable Standard today, compatible with 10BaseT equipment Generally called 100Base-T 100Base-T4 early version, uses all four twisted pairs in a Cat 3 or better cable Uncommon, because it wasn't backwards compatible 100Base-FX multimode optical fiber (MMF) allows 2000m lengths 2000m = 2km 1.6 miles Good for backbones, or where electrical interference

6 Connecting the Nodes 100Base-T networks can be connected via hubs and interconnected with 10Base-T hubs and NICs 100Base-T NICs must be auto-sensing in order to work with older 10Base-T hubs They just slow down to 10Mbps when so connected Most 100Base-T NICs are actually 10/100 NICs 100Base-T hubs are rare switches are more effective, and cost no more Most/all 100Base-T switches are auto-sensing, autonegotiating they can support 100Base-T and 10Base-T nodes, at the highest speed for each

7 Switch features Auto-sensing Detect available speeds, use fastest supported speed on each port forwarding frames from a 100Mbps port to a 10Mbps port will require buffering, queuing Auto-negotiation Determine whether half-duplex or full-duplex is available, on port-per-port basis Newest standards require full duplex Auto-MDI / MDIX Detect whether straight-through or crossover connection is required

8 Half-Duplex versus Full Duplex 10Base-T and 100Base-T support bidirectional ("duplex") communications Only one direction can be used at a time IEEE 802.3x, 1997, specifies optional fullduplex communications Most current switches and NICs auto-negotiate duplex as well as speed when connecting

9 100BaseFX optical fiber or more simply, 100BaseF Two choices of connector can be used Adapter cables use both right: ST connectors below: SC connectors A pair of multimode optical fibers provides fullduplex operation

10 Gigabit Ethernet Another 10x Speedup IEEE 802.3z, BaseCX: twinax cable 25m maximum length 1000BaseSX (short): multimode optical fiber, LED sources m maximum length 1000BaseLX (long): single-mode optical fiber, laser sources 5000m (~3 mile) maximum length

11 Gigabit Ethernet Another 10x Speedup 1000BaseCX: twinax cables at first Short-range use only 1000BaseSX: MMF; 1000BaseLX: SMF Small-Form-Factor (SFF) connectors MT-RJ LC

12 Gigabit Ethernet Over Twisted Pairs IEEE 802.3ab, Base-T, a.k.a. GigE 1000Mbps (1Gbps), 100m maximum length Full duplex only Requires all four twisted pairs Crossover cables must swap all pairs, unlike 10Base-T/100base-T crossover cables Automatic MDI/MDI-X configuration permits NICs and switches to use either a straight-through or a crossover cable

13 Gigabit Ethernet in the LAN an older enterprise example Core connected enterprise resources Wiring Closet "Access" switches

14 Gigabit Ethernet Switches 2017 prices TP-Link TL-SG1024: $70 small businesses Cisco 2960X- 24TS-L: $2000 Accesslayer switch

15 PoE Power over Ethernet 2003 IEEE 802.3af "Alternative A", spare-wire "Alternative B", commonmode 2009 IEEE 802.3at 25W power levels 2017 IEEE 802.3bt Ethernet cable carries power along with data Good for remote device installations 100W power, alternative A Available on twisted pair cables 10Base-T, 100Base-T: alternative B GigE: both alternatives

16 10-Gigabit Ethernet IEEE 802.3ae, Gbps, optical fiber SONET compatibility Synchronous Optical Networking is popular for optical fiber links IEEE 802.3an, GBaseT, a.k.a. 10GigE or 10GbE 10Gbps, Shielded TP 55m on Cat 6 cable 100m on Cat 6a or Cat 7 cable uses all four twisted pairs full-duplex only, so CSMA/CD not needed Server racks

17 Ethernet and Servers at Facebook Servers. Lots of servers. Here s a look at the racks inside the Lulea facility, with network switches at the top of the rack, servers filling the bulk of the rack, and storage at the bottom.

18 A 10-Gigabit Backbone at William Paterson University, New Jersey 2013 "Today, the WPUnjNet backbone consists of four Cisco Gigabit core switches and two Cisco Nexus Gigabit core switch[es] strategically located across the campus optimized for performance and bandwidth. Faulttolerance between the Gigabit switches is accomplished by using a redundant path from and to each Gigabit switch. Routing is accomplished by utilizing the same Gigabit technology capable of wire-speed routing. A total of 220 Virtual LANs (VLANs) are connected to this 10 gigabit core fabric."

19 10GigE to the desktop? the University of Michigan has a 10GigE network for researchers

20 Beyond 10 Gbps Uses for extremely fast Ethernet Connections between processor blades of a multiblade server "Top-of-rack" connections between servers Core connections between server groups Backbone connections Current targets: 25 Gbps, 40 Gbps easiest to achieve 50 Gbps, 100 Gbps preferable 200, 400 Gbps longer-term goal

21 2010: 40 Gbps, 100 Gbps Ethernets IEEE 802.3ba, June 17, 2010 first standard to specify two speeds 40Gbps intended for switchserver connections earlier deployment, lower cost 100Gbps intended for switch-switch backbones Specifications for optical fiber, twinax wire, and backplane installations Backplanes connect multiple devices in a shared cabinet/rack

22 A Cisco vision for 40GbE / 100GbE 40Gbps between Distribution and Core 40Gbps between Core and Data Center 40Gbps, 100Gbps within Data Center

23 A not-too-obsolete IEEE projection for bandwidth requirements

24 25GbE more economical than 40GbE 40Gbps Ethernet is actually 4 10Gbps "lanes" at the PHY level, used in parallel IEEE 802.3by defines single-lane 25Gbps standards June 2016 less expensive installations than 4-lane 40Gbps On the horizon: 2018? IEEE 802.3cd defining single-lane 50Gbps standards

25 June 2016 IEEE 802.3bq provides for 25GBase-T, 40GBase-T Twisted-Pair! Cheaper than optical fiber Relatively short runs: 5 to 30 meters maximum New TIA/EIA category 8 cabling

26 Below 10Gbps September 2016 IEEE 802.3bz 2.5 Gbps over cat 5e unshielded twisted pair 5 Gbps over cat 6 UTP Needed to keep up with highest-speed Wi-Fi Allows speed improvement without replacing existing cabling