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Rivier College
CS575: Advanced LANs
Gigabit Ethernet
CS575
Gigabit Ethernet
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Overview
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What is Gigabit Ethernet?
Why Gigabit Ethernet
Physical Layer Technologies
Functional Elements of Gigabit Ethernet Technology
Performance Issues
Gigabit Ethernet Migration and Application Environments
Vendor Implementation Examples
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Gigabit Ethernet
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What is Gigabit Ethernet?
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An extension to 10 Mbps and 100 Mbps IEEE 802.3 Ethernet
Offering 1000 megabits per second data rate
An emerging IEEE 802.3z Ethernet standard
The first draft of the standard was produced by IEEE in January
1997
The final standard was approved in June 1998
Can be implemented in either hubs (repeaters) or switches
The hub is a shared medium technology (medium access control
such as CSMA/CD is needed) and the switch is a dedicated
medium technology (no medium access controls are needed)
Allows half-duplex (HDX) and full-duplex (FDX) operation at
speeds of 1000 Mbps (2000 Mbps effective throughput for FDX)
Expected to be deployed initially as a backbone network as well as
for high speed server connections
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Gigabit Ethernet
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What is Gigabit Ethernet? (concluded)
0 Evolutionary high speed network using existing standards and
proven technology
0 Compatible with existing Ethernet
- Unchanged Ethernet MAC Layer (CSMA/CD) protocol
- Unchanged Ethernet frame format and frame size (both
maximum and minimum)
0 Support existing star-wired topology
0 Support existing Ethernet applications
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Gigabit Ethernet
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Why Gigabit Ethernet?
0 Faster and more power computers continues to grow
0 The need for gigabit LAN backbone to interconnect faster LANs
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such as Fast Ethernet
Growing number of complex, time critical, and bandwidth intensive
applications such large image file transfers
Capability to support new applications and data types such as voice
and video
Easy migration to higher performance levels (from wide installation
base of Ethernet/Fast Ethernet) without disruption (compare to
ATM or other technologies)
Low cost of ownership including both purchasing cost and support
cost
Internetworking and network design flexibility
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Gigabit Ethernet
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Applications Driving Network Growth
Application
Data Types/Size
Scientific Modeling,
Engineering
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Publications, Medical Data
Transfer
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Internet/Intranet
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Data Warehousing,
Network Backup
Desktop Video
Conferencing, Interactive
Whiteboarding
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Data Files
100's of megabytes to
gigabytes
Data Files
100's of megabytes to
gigabytes
Data files now
Audio now
Video is emerging
High transaction rate
Large files, 1 MB to
100 MB
Data Files
Gigabytes to terabytes
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Constant data stream
1.5 to 3.5 Mbps at the
desktop
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Network Traffic
Implication
Large files increase
bandwidth required
Network Need
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Large files increase
bandwidth required
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Large files increase
bandwidth required
Low transmission
latency
High volume of data
streams
Large files increase
bandwidth required
Transmitted during
fixed time period
Class of service
reservation
High volume of data
streams
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Higher bandwidth for
desktops, servers, and
backbone
Higher bandwidth for
desktops, servers, and
backbone
Higher bandwidth for
servers, and backbone
Low latency
Higher bandwidth for
servers, and backbone
Low latency
Higher bandwidth for
servers, and backbone
Low latency
Predictable latency
Source: Gigabit Ethernet Alliance
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Physical Layer Technology
0 The Physical Layer technology for Gigabit Ethernet is mainly based
on the ANSI X3T11 standards for Fibre Channel
0 Since Fibre Channel technology has been in use for for several
years, the IEEE 802.3z standards committee decided to adopt this
technology to reduce development time and risk for the Gigabit
Ethernet standard
0 Four physical media types are defined for Gigabit Ethernet
- Single mode fiber
- Multimode fiber
- Shielded twisted pair cable (STP)
- Unshielded twisted pair (UTP-5) cable
0 Two Physical Layer standards
- 1000BASE-X (IEEE 802.3z)
- 1000BASE-T (IEEE 802.3ab)
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Physical Layer Technology (continued)
0 1000BASE-X is based on Fibre Channel Physical Layer standard
- Three media types included in 1000BASE-X
= 1000BASE-SX: Short wavelength (850 nm) laser on
multimode fiber
= 1000BASE-LX: Long wavelength (1300 nm) laser on single
mode and multimode fiber
= 1000BASE-CX: Short haul copper “twinax” STP
- 1000BASE-SX is targeted at lowest cost multimode fiber runs
in horizontal and shorter backbone applications
- 1000BASE-LX is targeted at longer multimode building fiber
backbones and single mode campus backbones
- 1000BASE-CX is used for interconnection of equipment within
a short distance (25 m) in a computer room
- Based on Fibre channel’s 8B/10B encoding (25% overhead)
- 1.25 Gbps wire speed to achieve 1 Gbps data rate
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Physical Layer Technology (continued)
1000BASE-X Cable Type and Distances
Cable Type
Single-mode Fiber (9 micron)
Multimode Fiber (62.5 micron)
Multimode Fiber (50 micron)
Short-haul Copper
Distance
5000 m using 1300 nm laser (LX)
275 m using 850 nm laser (SX)
550 m using 1300 nm laser (LX)
550 m using 850 nm laser (SX)
550 m using 1300 nm laser (LX)
25 m
Source: Gigabit Ethernet Alliance
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Physical Layer Technology (continued)
0 1000BASE-T Standard
- A standard (IEEE 802.3ab) for Gigabit Ethernet over 4 pairs of
Category 5 UTP for distance up to 100 meters
- Based on the specifications of ANSI/TIA/EIA-568A (1995)
- No need to replace existing Category 5 cabling (conforming to
1995 ANSI/TIA/EIA-568A standards) to use 1000BASE-T
- Any link supporting 100BASE-TX should support 1000BASE-T
- Installed cabling should be tested for return loss (echo), caused
by impedance mismatches (typically the fault of of poor
connectors) and far-end crosstalk (signal leakage from
adjoining wire pairs at the far end of the transmitter creates
electrical noise)
- Uses a symbol rate of 125 Mbaud
- uses a more sophisticated 4-dimensional, 5-level Pulse
Amplitude Modulation (4D-PAM5) coding scheme
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Physical Layer Technology (concluded)
- 4-levels to achieve 2 bits per symbol and the fifth level for Trellis
Froward Error Correction coding
- Supports FDX on each pair of Category 5 UTP
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Functional Elements of Gigabit Ethernet
Technology
Ethernet Upper Layers
Media Access Control (MAC)
Full duplex/ Half duplex
Gigabit Media Independent Interface (GMII)
1000BASE-T
Encoder/Decoder
1000BASE-X 8B/10B
Encoder/Decoder
1000BASE-LX
LWL
Fiber Optic
Tranceiver
1000BASE-SX
SWL
Fiber Optic
Tranceiver
1000BASE-CX
Shielded Balanced
Copper
Tranceiver
1000BASE-T
UTP
Category 5
Tranceiver
9 u SMF - 5km
50 u MMF - 550 m
62.5 u MMF - 500 m
50 u MMF - 550 m
62.5 u MMF - 220 - 275m
25 m
100 m
802.3z physical layer
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Gigabit Ethernet
802.3ab
physical layer
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Performance Issues
0 Limitations of shared medium (HDX) Gigabit Ethernet
- Without modification to the Ethernet MAC layer protocol, the
maximum network diameter/size of Gigabit Ethernet is limited
to about 20 m
- To keep the maximum network diameter/size of Gigabit
Ethernet to 200 m (same as Fast Ethernet), the minimum
CSMA/CD carrier time and the Ethernet slot time have been
extended to 512 bytes (should be 640 bytes)
- Packets smaller than 512 bytes have an extra carrier extension
- If all traffic consisting of 64-byte frames, the effective
throughput would drop to 120 Mbps
- The Gigabit Ethernet throughput would be between 300 - 400
Mbps for average frame size on most Ethernet in the 200- 500byte range
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Performance Issues (continued)
0 Gigabit Ethernet switches must be used to extend network size
0 Not appropriate for seamless integration of LAN, MAN, and WAN
0 Doesn’t deliver the QoS guarantees needed by multimedia
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applications
Working on standards to provide Quality of Service (QoS) and
Class of Service (CoS) to IP traffic
Use 802.1Q/p to provide priority information for frames in the
network
Use 802.3x for flow control
QoS support by switch vendors such as Foundry Networks
- Policy-based traffic classification on
= Type of Service (ToS)
= IP precedence mapping
= Layer 2/3/4 defined traffic flow
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Performance Issues (continued)
- Queue management
= Strict Priority (SP) Queue
= Weighted Fair Queue (WFQ)
= 802.1p queue mapping
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Gigabit Ethernet
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Performance Issues (concluded)
Source: Stallings: Data and Computer Communications
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Gigabit Ethernet
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Gigabit Ethernet Migration and Application
Environments
Fast Ethernet Switch to Switch Links
Source: Gigabit Ethernet Alliance
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Gigabit Ethernet Migration and Application
Environments (continued)
Upgrading Switch to Switch Links
Source: Gigabit Ethernet Alliance
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Gigabit Ethernet Migration and Application
Environments (continued)
Fast Ethernet Switch to Server Links
Source: Gigabit Ethernet Alliance
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Gigabit Ethernet Migration and Application
Environments (continued)
Upgrading Switch to Server Links
Source: Gigabit Ethernet Alliance
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Gigabit Ethernet Migration and Application
Environments (continued)
Switched Fast Ethernet Backbone
Source: Gigabit Ethernet Alliance
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Gigabit Ethernet Migration and Application
Environments (continued)
Upgrading Switched Fast Ethernet Backbone
Source: Gigabit Ethernet Alliance
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Gigabit Ethernet Migration and Application
Environments (continued)
Shared FDDI Backbone
Source: Gigabit Ethernet Alliance
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Gigabit Ethernet Migration and Application
Environments (continued)
Upgrading Shared FDDI Backbone
Source: Gigabit Ethernet Alliance
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Gigabit Ethernet Migration and Application
Environments (concluded)
Upgrading High-Performance Desktops
Source: Gigabit Ethernet Alliance
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Examples of Gigabit Ethernet Switches
Lucent P550 Cajun Switch
CS575
Foundry BigIron 4000
Gigabit Ethernet Switch
Gigabit Ethernet
Extreme BlackDimaond
Gigabit Ethernet Switch
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Enterprise-Campus Network Example
Source: Foundry Networks
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Gigabit Ethernet
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Traditional Router and Hub Campus Intranet
Source: Cisco White Paper
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Traditional Campus Wide VLAN Design
Source: Cisco White Paper
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Campus Wide VLAN with Multilayer Switching
Source: Cisco White Paper
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Multilayer Model with Server Farm
Source: Cisco White Paper
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References
W. Stalling, Local and Metropolitan Area Networks,
6th edition, Prentice Hall, 2000, Chapter 7
W. Stalling, Data and Computer Communications,
6th edition, Prentice Hall, 2002, Chapters 13-14
A. Wu, Advanced Local Area Networks, Lectures &
Slides, Rivier College, 2001.
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