DOC PREVIEW
Berkeley COMPSCI 252 - Lecture 16 Networks & Interconnect

This preview shows page 1-2-3-19-20-39-40-41 out of 41 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 41 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 41 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 41 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 41 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 41 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 41 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 41 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 41 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 41 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

Lecture 16: Networks & Interconnect (Routing, Examples, Protocols) + Intro to Parallel ProcessingReview: Performance MetricsReview: InterconnectionsConnection-Based vs. ConnectionlessSlide 5Routing MessagesDeterministic Routing ExamplesStore and Forward vs. Cut-ThroughSlide 9Congestion ControlPractical Issues for Inteconnection NetworksPractical IssuesCross-Cutting Issues for NetworkingCS 252 AdministriviaProtocols: HW/SW InterfaceFTP From Stanford to BerkeleyProtocolTCP/IP packetExample NetworksConnecting NetworksSlide 21Example Networks (cont’d)Examples: Interface to ProcessorPacket FormatsExample Switched LAN PerformanceExample Switched LAN Performance (1995)UDP/IP performanceNFS performanceEstimated Database performance (1995)Summary: NetworkingParallel ComputersParallel Processors “Religion”Opportunities: Scientific ComputingExample: Scientific ComputingOpportunities: Commercial ComputingWhat level Parallelism?Whither Supercomputing?Parallel ArchitectureParallel FrameworkShared Address Model SummaryNetworking SummaryDAP Spr.‘98 ©UCB 1Lecture 16: Networks & Interconnect (Routing, Examples, Protocols) + Intro to Parallel ProcessingProfessor David A. PattersonComputer Science 252Spring 1998DAP Spr.‘98 ©UCB 2Review: Performance MetricsSenderReceiverSenderOverheadTransmission time(size ÷ bandwidth)Transmission time(size ÷ bandwidth)Time ofFlightReceiverOverheadTransport LatencyTotal Latency = Sender Overhead + Time of Flight + Message Size ÷ BW + Receiver OverheadTotal Latency(processorbusy)(processorbusy)Includes header/trailer in BW calculation?DAP Spr.‘98 ©UCB 3Review: 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. Switched 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, should not be programming issueDAP Spr.‘98 ©UCB 4Connection-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 bandwidthDAP Spr.‘98 ©UCB 5Connection-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 packetsDAP Spr.‘98 ©UCB 6Routing 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 loadDAP Spr.‘98 ©UCB 7•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•tree: common ancestor•Deadlock free?Deterministic Routing Examples001000101100010110111011DAP Spr.‘98 ©UCB 8Store 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, accordioning the whole message into a single switch. (Requires a buffer large enough to hold the largest packet).DAP Spr.‘98 ©UCB 9Store and Forward vs. Cut-Through•Advantage–Latency reduces from function of:number of intermediate switches X by the size of the packet to time for 1st part of the packet to negotiate the switches + the packet size ÷ interconnect BWDAP Spr.‘98 ©UCB 10Congestion 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 no room in buffer, packet is discarded (e.g., UDP)–Flow control: between pairs of receivers and senders; use feedback to tell sender when allowed to send next packet»Back-pressure: separate wires to tell to stop»Window: give original sender right to send N packets before getting permission to send more; overlapslatency of interconnection with overhead to send & receive packet (e.g., TCP), adjustable window–Choke packets: aka “rate-based”; Each packet received by busy switch in warning state sent back to the source via choke packet. Source reduces traffic to that destination by a fixed % (e.g., ATM)DAP Spr.‘98 ©UCB 11Practical 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 interconnectDAP Spr.‘98


View Full Document

Berkeley COMPSCI 252 - Lecture 16 Networks & Interconnect

Documents in this Course
Quiz

Quiz

9 pages

Caches I

Caches I

46 pages

Lecture 6

Lecture 6

36 pages

Lecture 9

Lecture 9

52 pages

Figures

Figures

26 pages

Midterm

Midterm

15 pages

Midterm

Midterm

14 pages

Midterm I

Midterm I

15 pages

ECHO

ECHO

25 pages

Quiz  1

Quiz 1

12 pages

Load more
Download Lecture 16 Networks & Interconnect
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Lecture 16 Networks & Interconnect and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Lecture 16 Networks & Interconnect 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?