Download Network

CMPUT429/CMPE382 Winter 2001
TopicA: Network (Adapted from David A.
Patterson’s CS252,
Spring 2001 Lecture Slides)
1/17/01
CMPUT429/CMPE382
Amaral
I/O to External Devices and Other
Computers
Processor
interrupts
Cache
Memory - I/O Bus
Main
Memory
I/O
Controller
Disk
Disk
I/O
Controller
Graphics
I/O
Controller
Network
ideal: high bandwidth, low latency
1/17/01
CMPUT429/CMPE382
Amaral
Networks
• Goal: Communication between computers
• Eventual Goal: treat collection of computers as
one big computer, distributed resource sharing
• Theme: Different computers must agree on
many things
– Overriding importance of standards and protocols
– Fault tolerance critical as well
• Warning: Terminology-rich environment
1/17/01
CMPUT429/CMPE382
Amaral
Example Major Networks
IP - internet Protocol
TCP - Transmission
Control Protocol
CS Net
FDDI
100Mbps
Phonenet
T1, 56Kbps
ARPA net
NSF Net
CS Net
Relay
1.6Mbps
10 Mbps
Token Ring
4Mbps
Ethernet
1/17/01
T3, 230Kbps
Bitnet
ATM
X.25
(Telenet, Uninet_
CMPUT429/CMPE382
Amaral
Networks
• Facets people talk a lot about:
–
–
–
–
–
direct (point-to-point) vs. indirect (multi-hop)
topology (e.g., bus, ring, DAG)
routing algorithms
switching (aka multiplexing)
wiring (e.g., choice of media, copper, coax, fiber)
• What really matters:
–
–
–
–
1/17/01
latency
bandwidth
cost
reliability
CMPUT429/CMPE382
Amaral
Interconnections (Networks)
• Examples:
– MPP networks (SP2): 100s nodes; Š 25 meters per link
– Local Area Networks (Ethernet): 100s nodes; Š 1000 meters
– Wide Area Network (ATM): 1000s nodes; Š 5,000,000 meters
a.k.a.
end systems,
hosts
a.k.a.
network,
communication
subnet
1/17/01
Interconnection Network
CMPUT429/CMPE382
Amaral
More Network Background
• Connection of 2 or more networks:
Internetworking
• 3 cultures for 3 classes of networks
– MPP: performance, latency and bandwidth
– LAN: workstations, cost
– WAN: telecommunications, phone call revenue
• Try for single terminology
• Motivate the interconnection complexity
incrementally
1/17/01
CMPUT429/CMPE382
Amaral
ABCs of Networks
• Starting Point: Send bits between 2 computers
•
•
•
•
Queue (FIFO) on each end
Information sent called a “message”
Can send both ways (“Full Duplex”)
Rules for communication? “protocol”
– Inside a computer:
» Loads/Stores: Request (Address) & Response (Data)
» Need Request & Response signaling
1/17/01
CMPUT429/CMPE382
Amaral
A Simple Example
• What is the format of message?
– Fixed? Number bytes?
Request/
Response
1 bit
Address/Data
32 bits
0: Please send data from Address
1: Packet contains data corresponding to request
• Header/Trailer: information to deliver a message
• Payload: data in message (1 word above)
1/17/01
CMPUT429/CMPE382
Amaral
Questions About Simple Example
• What if more than 2 computers want to
communicate?
– Need computer “address field” (destination) in packet
• What if packet is garbled in transit?
– Add “error detection field” in packet (e.g., CRC)
• What if packet is lost?
– More “elaborate protocols” to detect loss
(e.g., NAK, ARQ, time outs)
• What if there are multiple processes/machine?
– Queue per process to provide protection
• Simple questions such as these lead to more complex
protocols and packet formats
1/17/01
CMPUT429/CMPE382
Amaral
A Simple Example Revisted
• What is the format of packet?
– Fixed? Number bytes?
Request/
Response
Address/Data
CRC
1 bit
32 bits
4 bits
00: Request—Please send data from Address
01: Reply—Packet contains data corresponding to request
10: Acknowledge request
11: Acknowledge reply
1/17/01
CMPUT429/CMPE382
Amaral
Software to Send and Receive
• SW Send steps
1: Application copies data to OS buffer
2: OS calculates checksum, starts timer
3: OS sends data to network interface HW and says start
• SW Receive steps
3: OS copies data from network interface HW to OS buffer
2: OS calculates checksum, if matches send ACK; if not,
deletes message (sender resends when timer expires)
1: If OK, OS copies data to user address space and signals
application to continue
• Sequence of steps for SW: protocol
– Example similar to UDP/IP protocol in UNIX
1/17/01
CMPUT429/CMPE382
Amaral
Network Performance Measures
• Overhead: latency of interface vs. Latency:
1/17/01
network
CMPUT429/CMPE382
Amaral
Universal Performance Metrics
Sender
Sender
Overhead
Transmission time
(size ÷ bandwidth)
(processor
busy)
Time of
Flight
Transmission time
(size ÷ bandwidth)
Receiver
Overhead
Receiver
Transport Latency
(processor
busy)
Total Latency
Total Latency = Sender Overhead + Time of Flight +
Message Size ÷ BW + Receiver Overhead
Includes header/trailer in BW calculation?
1/17/01
CMPUT429/CMPE382
Amaral
Example Performance Measures
Interconnect
MPP
LAN
WAN
Example
Bisection BW
Int./Link BW
Transport Latency
HW Overhead to/from
SW Overhead to/from
CM-5
Ethernet
ATM
N x 5 MB/s 1.125 MB/s N x 10 MB/s
20 MB/s
1.125 MB/s 10 MB/s
5 µsec
15 µsec
50 to 10,000 µs
0.5/0.5 µs 6/6 µs
6/6 µs
1.6/12.4 µs 200/241 µs 207/360 µs
(TCP/IP on LAN/WAN)
Software overhead dominates in LAN, WAN
1/17/01
CMPUT429/CMPE382
Amaral
Total Latency Example
• 10 Mbit/sec., sending overhead of 230 µsec &
receiving overhead of 270 µsec.
• a 1000 byte message (including the header),
allows 1000 bytes in a single message.
• 2 situations: distance 0.1 km vs. 1000 km
• Speed of light = 299,792.5 km/sec (1/2 in
media)
• Latency0.1km =
• Latency1000km =
• Long time of flight => complex WAN protocol
1/17/01
CMPUT429/CMPE382
Amaral
Simplified Latency Model
• Total Latency = Overhead + Message Size /
BW
• Overhead = Sender Overhead + Time of Flight
+ Receiver Overhead
• Example: show what happens as the following
parameters change:
– Overhead: 1, 25, 500 µsec
– BW: 10,100, 1000 Mbit/sec (factors of 10)
– Message Size: 16 Bytes to 4 MB (factors of 4)
1/17/01
• If overhead 500 µsec,
how big a message > 10 Mb/s?
CMPUT429/CMPE382
Amaral
Overhead, BW, Size
Delivered BW
200 o500,b200
0
0
1
2
8
28
79
Effective Bandwidth (Mbit/sec)
1,000
1/17/01
o1,
bw1000
o25,
bw1000
100
10
o1,
bw10
1
o500,
bw100
o25,
bw100
o1,
bw100
o25,
bw10
o500,
bw1000
o500,
bw10
Msg Size
0
o25,bw100: overhead of 25 microseconds,
bandwidth of 100 Mbits/second
0
CMPUT429/CMPE382
Amaral
Cummulative %
Measurement:
Sizes of Message for NFS
100%
90%
80%
70%
60%
50%
40%
30%
20%
10%
0%
Msgs
0
1/17/01
Why?
Bytes
1024
2048
3072
4096
5120
6144
7168
8192
Packet size
• 95% Msgs, 30% bytes for packets Š 200 bytes
• > 50% data transfered in packets = 8KB
CMPUT429/CMPE382
Amaral
Impact of Overhead on Delivered
BW
Delivered BW
(MB/sec)
1000.00
1
100.00
10
100
10.00
1000
1.00
1000
100
10
1
0.10
MinTime
one-way
µsecs
Peak BW (MB/sec)
1/17/01
• BW model: Time = overhead + msg size/peak
BW
CMPUT429/CMPE382
Amaral
• > 50% data transfered in packets = 8KB
HW Interface Issues
• Where to connect network to computer?
–
–
–
–
Cache consistent to avoid flushes? (=> memory bus)
Latency and bandwidth? (=> memory bus)
Standard interface card? (=> I/O bus)
MPP => memory bus; LAN, WAN => I/O bus
CPU
Network
$
I/O
Controller
L2 $
Memory Bus
Memory
1/17/01
Network
I/O
Controller
ideal: high bandwidth,
low latency,
standard interface
I/O bus
Bus Adaptor
CMPUT429/CMPE382
Amaral
SW Interface Issues
• How to connect network to software?
–
–
–
–
Programmed I/O?(low latency)
DMA? (best for large messages)
Receiver interrupted or receiver polls?
Poll-watchdog?
• Things to avoid
– Invoking operating system in common case
– Operating at uncached memory speed
(e.g., check status of network interface)
1/17/01
CMPUT429/CMPE382
Amaral
CM-5 Software Interface
Overhead
• CM-5 example (MPP)
• As rate of messages
arriving changes, use
polling or interrupt?
– Solution: Always enable
interrupts, have interrupt
routine poll until no messages
pending
– Low rate => interrupt
– High rate => polling
1/17/01
90
message overhead (µsecs)
– Time per poll 1.6 µsecs; time
per interrupt 19 µsecs
– Minimum time to handle
message: 0.5 µsecs
– Enable/disable 4.9/3.8 µsecs
100
80
70
60
Polling
50
40
30
Interrupts
20
10
0
0
10
20
30
40
50
60
70
80
90
100
message interarriv al (µsecs)
Time between messages
CMPUT429/CMPE382
Amaral
Network Media
Twisted Pair:
Copper, 1mm think, twisted to avoid
attenna effect (telephone)
Coaxial Cable:
Fiber Optics
Transmitter
– L.E.D
– Laser Diode
light
source
1/17/01
Used by cable companies:
high BW, good noise
immunity
Light: 3 parts
are cable, light
source, light
detector.
Total internal
Multimode
reflection
light disperse
Receiver
– Photodiode (LED), Single
mode sinle
wave (laser)
Silica
Plastic Covering
Braided outer conductor
Insulator
Copper core
Air
CMPUT429/CMPE382
Amaral
Costs of Network Media (1995)
Cost/meter Cost/interface
Bandwidth Distance
Media
$0.23
$2
2 km
1 Mb/s
twisted pair
(0.1 km)
(20 Mb/s)
copper wire
1 km
$1.64
$5
10 Mb/s
coaxial cable
2 km
$1.03
$1000
600 Mb/s
multimode
optical fiber
2000 Mb/s
single mode
100 km
$1.64
$1000
optical fiber
Note: more elaborate signal processing allows higher BW from copper
(ADSL)
Single mode Fiber measures: BW * distance as 3X/year
1/17/01
CMPUT429/CMPE382
Amaral
Connecting Multiple Computers
• Shared Media vs. Switched:
pairs communicate at same time:
“point-to-point” connections
• Aggregate BW in switched
network is many times shared
– point-to-point faster since no
arbitration, simpler interface
• Arbitration in Shared network?
– Central arbiter for LAN?
– Listen to check if being used (“Carrier
Sensing”)
– Listen to check if collision
(“Collision Detection”)
– Random resend to avoid repeated
collisions; not fair arbitration;
– OK if low utilization
1/17/01
(A. K. A. data switching
interchanges, multistage
interconnection networks,
interface message processors)
CMPUT429/CMPE382
Amaral
Example Interconnects
Interconnect
MPP
Example
Maximum length
CM-5
Ethernet
25 m
500 m;
between nodes
optical: 2 km—25 km
4
1
40 MHz
10 MHz
Switch
Shared
2048
254
ATM
copper: 100 m
Š5 repeaters
Copper
Twisted pair
copper wire or
optical fiber
Number data lines
Clock Rate
Shared vs. Switch
Maximum number
of nodes
Media Material
1/17/01
LAN
Twisted pair
copper wire
or Coaxial
cable
WAN
1
•155.5 MHz
Switch
> 10,000
CMPUT429/CMPE382
Amaral
Switch Topology
• Structure of the interconnect
• Determines
– Degree: number of links from a node
– Diameter: max number of links crossed between nodes
– Average distance: number of hops to random
destination
– Bisection: minimum number of links that separate the
network into two halves (worst case)
• Warning: these three-dimensional drawings
must be mapped onto chips and boards which
are essentially two-dimensional media
– Elegant when sketched on the blackboard may look
awkward when constructed from chips, cables, boards,
and boxes (largely 2D)
• Networks should not be interesting!
1/17/01
CMPUT429/CMPE382
Amaral
Important Topologies
N = 1024
Type
Degree Diameter Ave Dist
Bisection
Diam
Ave D
1D mesh
Š2
N-1
1
2D mesh
Š4
2(N1/2 - 1) 2N1/2 / 3
N1/2
63
21
3D mesh
Š6
3(N1/3 - 1) 3N1/3 / 3
N2/3
~30
~10
nD mesh
Š 2n
n(N1/n - 1) nN1/n / 3
N(n-1) / n
Ring
2
N/2
N/4
2
2D torus
4
N1/2
N1/2 / 2
2N1/2
32
16
k-ary n-cube 2n
(N = kn)
n(N1/n)
nk/2
nN1/n/2
nk/4
15
8 (3D)
Hypercube
n = LogN n/2
10
5
N/3
(N = kn)
n
2kn-1
N/2
Cube-Connected Cycles
Hypercude 23
1/17/01
CMPUT429/CMPE382
Amaral
Topologies (cont)
N = 1024
Type
Degree Diameter Ave Dist
Bisection Diam
Ave D
2D Tree
3
2Log2 N
~2Log2 N
1
20
~20
4D Tree
5
2Log4 N
2Log4 N - 2/3 1
10
9.33
kD
k+1
Logk N
2D fat tree
4
Log2 N
N
2D butterfly 4
Log2 N
N/2
20
20
Fat Tree
1/17/01
CMPUT429/CMPE382
Amaral
Butterfly
Multistage: nodes at ends, switches in middle
N/2
Butterfly
°
°
°
• All paths have equal length
• Unique path from any
input to any output
N/2
Butterfly
1/17/01
°
°
°
• Conflicts that try to avoid
• Don’t want algortihm to have
to know paths
CMPUT429/CMPE382
Amaral
Summary: Interconnections
• Communication between computers
• Packets for standards, protocols to cover normal
and abnormal events
• Performance issues: HW & SW overhead,
interconnect latency, bisection BW
• Media sets cost, distance
• Shared vs. Swicthed Media determines BW
• HW and SW Interface to computer affects
overhead, latency, bandwidth
• Topologies: many to chose from, but (SW)
overheads make them look alike; cost issues in
topologies, not algorithms
CMPUT429/CMPE382
1/17/01
Amaral
Review: Performance Metrics
Sender
Sender
Overhead
Transmission time
(size ÷ bandwidth)
(processor
busy)
Time of
Flight
Transmission time
(size ÷ bandwidth)
Receiver
Overhead
Receiver
Transport Latency
(processor
busy)
Total Latency
Total Latency = Sender Overhead + Time of Flight +
Message Size ÷ BW + Receiver Overhead
Includes header/trailer in BW calculation?
1/17/01
CMPUT429/CMPE382
Amaral
Connection-Based vs. Connectionless
• Telephone: operator sets up connection between
the caller and the receiver
– Once the connection is established, conversation can continue for
hours
• Share transmission lines over long distances by
using switches to multiplex several conversations on
the same lines
– “Time division multiplexing” divide B/W transmission line into a
fixed number of slots, with each slot assigned to a conversation
• Problem: lines busy based on number of
conversations, not amount of information sent
• Advantage: reserved bandwidth
1/17/01
CMPUT429/CMPE382
Amaral
Connection-Based vs. Connectionless
• Connectionless: every package of information
must have an address => packets
– Each package is routed to its destination by looking at
its address
– Analogy, the postal system (sending a letter)
– also called “Statistical multiplexing”
– Note: “Split phase buses” are sending packets
1/17/01
CMPUT429/CMPE382
Amaral
Routing Messages
• Shared Media
– Broadcast to everyone
• Switched Media needs real routing. Options:
– Source-based routing: message specifies path to the
destination (changes of direction)
– Virtual Circuit: circuit established from source to
destination, message picks the circuit to follow
– Destination-based routing: message specifies
destination, switch must pick the path
» deterministic: always follow same path
» adaptive: pick different paths to avoid congestion,
failures
» Randomized routing: pick between several good
paths to balance network load
1/17/01
CMPUT429/CMPE382
Amaral
Deterministic Routing Examples
• mesh: dimension-order routing
– (x1, y1) -> (x2, y2)
– first x = x2 - x1,
– then y = y2 - y1,
• hypercube: edge-cube routing
– X = xox1x2 . . .xn -> Y = yoy1y2 . . .yn
– R = X xor Y
– Traverse dimensions of differing
address in order
110
010
111
• tree: common ancestor
• Deadlock free?
011
100
000
001
1/17/01
101
CMPUT429/CMPE382
Amaral
Store and Forward vs. Cut-Through
• Store-and-forward policy: each switch waits for
the full packet to arrive in switch before sending to
the next switch (good for WAN)
• Cut-through routing or worm hole routing: switch
examines the header, decides where to send the
message, and then starts forwarding it immediately
– In worm hole routing, when head of message is blocked, message
stays strung out over the network, potentially blocking other
messages (needs only buffer the piece of the packet that is sent
between switches). CM-5 uses it, with each switch buffer being 4
bits per port.
– Cut through routing lets the tail continue when head is blocked,
compresses the whole message into a single switch. (Requires a
buffer large enough to hold the largest packet).
1/17/01
CMPUT429/CMPE382
Amaral
Store and Forward vs. Cut-Through
• Advantage of cut-through and store-and-forward:
– Latency reduces as a function of:
number of intermediate switches X size of the packet
to
time for 1st part of the packet to negotiate the switches
+ (packet size / interconnect BW)
– (see example on page 594 of Textbook)
1/17/01
CMPUT429/CMPE382
Amaral
Congestion Control
• Packet switched networks do not reserve bandwidth;
this leads to contention (connection based limits input)
• Solution: prevent packets from entering until
contention is reduced (e.g., freeway on-ramp metering
lights)
• Options:
– Packet discarding: If packet arrives at switch and there is no room in
buffer, the packet is discarded (e.g., UDP)
– Flow control: between pairs of receivers and senders;
use feedback to tell sender when it is allowed to send next packet
» Back-pressure: separate wires to tell sender to stop
» Window: destination gives original sender right to send N packets
before getting permission to send more; overlaps latency of
interconnection with overhead to send & receive packet (e.g.,
TCP), adjustable window
1/17/01
CMPUT429/CMPE382
Amaral
Congestion Control (cont.)
• Options (cont.):
– Choke packets: aka “rate-based”;
» Limit traffic only when the network is congested;
» Each switch monitors itself and enters on a warning state when it
passes a threshold;
» Each packet received by a switch that is in the warning state is
sent back to the source as a choke packet, which contains the
original destination.
» When it receives a choke packet, the source reduces traffic to
that destination by a fixed % (e.g., ATM)
1/17/01
CMPUT429/CMPE382
Amaral
Practical Issues for Inteconnection
Networks
• Standardization advantages:
– low cost (components used repeatedly)
– stability (many suppliers to chose from)
• Standardization disadvantages:
– Time for committees to agree
– When to standardize?
» Before anything built? => Committee does design?
» Too early suppresses innovation
• Perfect interconnect vs. Fault Tolerant?
– Will SW crash on single node prevent communication?
(MPP typically assume perfect)
• Reliability (vs. availability) of interconnect
1/17/01
CMPUT429/CMPE382
Amaral
Practical Issues
Interconnection
Example
Standard
Fault Tolerance?
Hot Insert?
MPP
CM-5
No
No
No
LAN
Ethernet
Yes
Yes
Yes
WAN
ATM
Yes
Yes
Yes
• Standards: required for WAN, LAN!
• Fault Tolerance: Can nodes fail and still deliver
messages to other nodes? required for WAN, LAN!
• Hot Insert: If the interconnection can survive a
failure, can it also continue operation while a new
node is added to the interconnection? required for
CMPUT429/CMPE382
WAN, LAN!
1/17/01
Amaral
Cross-Cutting Issues for Networking
• Efficient Interface to Memory Hierarchy vs. to
Network
– SPEC ratings => fast to memory hierarchy
– Writes go via write buffer, reads via L1 and L2 caches
• Example: 40 MHz SPARCStation(SS)-2 vs 50
MHz SS-20, no L2 cache vs 50 MHz SS-20
with L2 cache I/O bus latency; different
generations
• SS-2: combined memory, I/O bus => 200 ns
• SS-20, no L2$: 2 busses +300ns =>
500ns
• SS-20, w L2$: cache miss+500ns => 1000ns
1/17/01
CMPUT429/CMPE382
Amaral
Protocols: HW/SW Interface
• Internetworking: allows computers on independent
and incompatible networks to communicate reliably
and efficiently;
– Enabling technologies: SW standards that allow reliable
communications without reliable networks
– Hierarchy of SW layers, giving each layer responsibility for
portion of overall communications task, called
protocol families or protocol suites
• Transmission Control Protocol/Internet Protocol
(TCP/IP)
– This protocol family is the basis of the Internet
– IP makes best effort to deliver; TCP guarantees delivery
– TCP/IP used even when communicating locally: NFS uses IP even
though communicating across homogeneous LAN
1/17/01
CMPUT429/CMPE382
Amaral
Protocol
• Key to protocol families is that communication occurs logically at
the same level of the protocol, called peer-to-peer, but is
implemented via services at the lower level
• Danger that each level increases latency if implemented as a
hierarchy (e.g., multiple check sums)
1/17/01
CMPUT429/CMPE382
Amaral
TCP/IP packet
1/17/01
• Application sends message
• TCP breaks into 64KB
segments, adds 20B
header
• IP adds 20B header, sends
to network
• If Ethernet, broken into
1500B packets with
headers, trailers
• Header, trailers have
length field, destination,
window number, version,
...
Ethernet
IP Header
TCP Header
IP Data
TCP data
(Š 64KB)
CMPUT429/CMPE382
Amaral
Example Networks
• Ethernet: shared media 10 Mbit/s proposed
in 1978, carrier sensing with expotential
back-off on collision detection
• 10 Mbit Ethernet successors?
–
–
–
–
–
1/17/01
FDDI: shared media (too late)
ATM (too late?)
Switched Ethernet
100 Mbit Ethernet (Fast Ethernet)
Gigabit Ethernet
CMPUT429/CMPE382
Amaral
Connecting Networks
• Bridges: connect LANs together, passing
traffic from one side to another depending
on the addresses in the packet.
– operate at the Ethernet protocol level
– usually simpler and cheaper than routers
• Routers or Gateways: these devices connect
LANs to WANs or WANs to WANs and
resolve incompatible addressing.
– Generally slower than bridges, they operate at the
internetworking protocol (IP) level
– Routers divide the interconnect into separate smaller
subnets, which simplifies manageability and improves
security
• Cisco is major supplier;
basically special purpose computers
1/17/01
CMPUT429/CMPE382
Amaral
Example Networks
MPP
LAN
WAN
IBM SP-2 100 Mb Ethernet
Length (meters)
10
Number data
8
lines
40 MHz
Clock Rate
Switch?
Yes
Nodes (N)
Š512
Material
copper
Bisection BW
320xNodes
(Mbit/s)
320
Peak Link BW
(Mbits/s)
Measured Link
284
BW
1/17/01
ATM
200
100/1000
1
1
100 MHz
155/622…
No
Yes
Š254
copper
10000
copper/fiber
100
155xNodes
100
155
--
80
CMPUT429/CMPE382
Amaral
Example Networks (cont’d)
MPP
LAN
WAN
IBM SP-2 100 Mb Ethernet
Latency (µsecs)
Send+Receive
Ovhd (µsecs)
Topology
Connectionless?
Store &
Forward?
Congestion
Control
Standard
Fault Tolerance
1/17/01
ATM
1
1.5
50
39
440
630
Fat tree
Line
Star
Yes
Yes
No
No
No
Yes
Backpressure
Carrier Sense
Choke packets
No
Yes
Yes
Yes
Yes
Yes
CMPUT429/CMPE382
Amaral
Examples:
Interface to Processor
1/17/01
CMPUT429/CMPE382
Amaral
Packet Formats
• Fields: Destination, Checksum(C), Length(L), Type(T)
• Data/Header Sizes in bytes: (4 to 20)/4, (0 to
CMPUT429/CMPE382
1500)/26, 48/5
1/17/01
Amaral
Example Switched LAN Performance
Network Interface
Switch
Link BW
AMD Lance Ethernet Baynetworks
10 Mb/s
EtherCell 28115
Fore SBA-200 ATM Fore ASX-200 155 Mb/s
Myricom Myrinet
Myricom Myrinet
640
Mb/s
• On SPARCstation-20 running Solaris 2.4 OS
• Myrinet is example of “System Area Network”:
networks for a single room or floor: 25m limit
1/17/01
– shorter => wider faster, less need for optical
– short distance => source-based routing => simpler switches
– Compaq-Tandem/Microsoft also sponsoring SAN, called
“ServerNet”
CMPUT429/CMPE382
Amaral
Networking Summary
• Protocols allow hetereogeneous networking
– Protocols allow operation in the presense of failures
• Routing issues: store and forward vs. cut through,
congestion, ...
• Standardization key for LAN, WAN
– Internetworking protocols used as LAN protocols => large
overhead for LAN
• Integrated circuit revolutionizing networks as well
as processors
• Switch is a specialized computer
1/17/01
CMPUT429/CMPE382
Amaral