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Topic: Loop (topology)


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In the News (Tue 20 Aug 19)

  
  Ls   (Site not responding. Last check: 2007-10-19)
It is transmitted by an L_Port to (re)initialize the Loop.
Loop Initialization is a logical procedure used by an L_Port to determine its environment and possibly to validate an AL_PA.
Loop Port Bypass all (LPBfx where f = hex 'FF') is transmitted on a Loop to bypass all L_Ports and activate the optional Bypass Circuit(s) of all L_Ports (except the L_Port at x).
members.aol.com /JRSFSI/1000Wds/Page_Ls.html   (3184 words)

  
  PlanetMath: loop
The collection of all such loops, modulo homotopy equivalence, forms a group known as the fundamental group.
Cross-references: constant, represents, homotopy groups, loop space, compact-open topology, fundamental group, group, homotopy equivalence, collection, continuous map, topological space
This is version 2 of loop, born on 2002-02-03, modified 2002-07-24.
planetmath.org /encyclopedia/Loop.html   (63 words)

  
 Glossary: A Technical SAN Reference
Loop Initialization Hard Assigned frame; a hard assigned AL_PA that is indicated by a bit set and is the third frame transmitted in the loop initialization process after a temporary loop master has been selected.
Loop Initialization Previously Assigned; where the device marks a bit in the bitmap if it had not logged in with the Fabric in a previous loop initialization.
Loop Port Bypass; a primitive sequence transmitted by an L_Port to bypass one or all L_Ports to which it is directed.
www.brocade.com /san/glossary.jsp   (5319 words)

  
 Hepadnavirus Envelope Topology: Insertion of a Loop Region in the Membrane and Role of S in L Protein Translocation -- ...
Microsomes from DHBV-positive primary duck hepatocytes were incubated with antiserum to either the first loop region in the S domain (aa 207 to 226), the pre-S domain (aa 127 to 156), or the second loop region in the S domain (aa 267 to 284) or with a control antibody (Co Ab).
(B) Revised topology of L with the loop region between TM1 and TM2 being shown as membrane embedded and with part of the loop, containing the epitope of aa 207 to 226, shown as a fl bar, being exposed to the lumen and ultimately to the particle surface.
Topology of the large surface protein of duck hepatitis B virus suggests a mechanism for membrane translocation during particle morphogenesis.
jvi.asm.org /cgi/content/full/74/5/2455   (2800 words)

  
 Cisco - Spanning-Tree Protocol Enhancements with Loop Guard and BPDU Skew Detection Features
Loop guard must be enabled on the non-designated ports (more precisely, on root and alternate ports) for all possible combinations of active topologies.
When the loop guard is configured on the port, it disables the root guard configured on the same port.
Loop guard cannot be enabled on dynamic VLAN ports since these ports have portfast enabled.
www.cisco.com /warp/public/473/84.html   (2078 words)

  
 Synonyms of loop — Infoplease.com
usage: the topology of a network whose components are connected in a loop
usage: an intrauterine device in the shape of a loop
usage: fly loops, perform a loop; "the stunt pilot looped his plane"
www.infoplease.com /thesaurus/loop   (245 words)

  
 Fibre Channel Overview   (Site not responding. Last check: 2007-10-19)
The hub maintains loop continuity by bypassing a node when the node or its cabling fails, when the node is powered down, or when the node is removed for maintenance.
In the arbitrated loop topology, a node port is called an NL_Port (node loop port), and a fabric port is called an FL_Port (fabric loop port).
Arbitrated loop provides reduced cost at the expense of bandwidth; all nodes in a loop share the bandwidth (100 MB/sec per loop), and bandwidth degrades slightly as nodes and cables are added.
h30097.www3.hp.com /docs/updates/nhdv2/CHFCVRVW.HTM   (1904 words)

  
 Fibre Channel Group---> University of Minnesota   (Site not responding. Last check: 2007-10-19)
The topology requires no arbitration for the media since the transmit on one node is connected to the receive on the other end of the cable.
Setting up a daisy-chained loop works if the number of devices is small, but it is not very scalable since it requires that all devices on the loop are active at the same time for the loop to be up and running.
The most common physical topology for an arbitrated loop is a hub, which forms a logical loop on a physical star with bypass circuitry to ensure that nodes that are failing or disconnected will not hold up the loop (see Figure 3).
gfs.lcse.umn.edu /fc/Basics   (2668 words)

  
 Valid Measurements - What, exactly, is an Anderson Loop?
The Anderson loop is a fundamental measurement circuit topology.
The added capabilities of the Anderson loop as compared to the Wheatstone bridge arise from the fact that the Wheatstone bridge accomplishes a PASSIVE subtraction while the Anderson loop accomplishes an ACTIVE subtraction of electrical potential differences.
Note that, unlike the Wheatstone bridge, (1) Anderson loop circuit equations are fundamentally linear for any change in circuit elements and (2) wire voltage drops are simply ignored, not somehow compensated for by depending on actual wires to behave exactly alike in the measurement environment.
www.vm-usa.com /loop.html   (715 words)

  
 Dell - Support
This topology is used to directly connect the N_Ports on two nodes, allowing a direct connection between a server and a storage device or between two servers.
The total bandwidth of the FC network is shared among the devices on the loop, which have to request control of the loop before transmitting data.
When a loop is connected to an FL_Port on the switch, it creates a public loop by inheriting the first 16-bits of that port''s address, and using the remaining 8 bits to provide addresses for the members of the public loop.
support.dell.com /us/en/kb/document.asp?dn=1046640   (2164 words)

  
 High-Speed Storage Area Networks Using a Fibre Channel Arbitrated Loop Interconnect
The loop topology was developed as a lower-cost alternative to the switch design, and is becoming a popular means of interconnecting computer systems to SCSI storage subsystems.
Fibre Channel arbitrated loop is an extension to transmission and signaling operations defined in the basic Fibre Channel standard [1] to support a loop topology.
Once loop access is achieved, the port must establish a circuit with the port to which it will communicate.
www.comsoc.org /ni/private/2000/mar/Heath.html   (3977 words)

  
 Mandragor & Apinc - Free Documentation Base
Because of this, address validation is required after a LIP in a loop topology [7] or after NOS/OLS in a point-to-point topology [6].
The private loop may connect a number of devices (max 126) in a logical ring much like Token Ring, and is distinguished from a public loop by the absence of a Fabric Node participating in the loop.
For the Arbitrated Loop topology, with the destination NL_Port on the same AL, the source port must pick the destination port, determine its AL Physical Address, and "Open" the destination port.
docs.mandragor.org /files/RFCs/26xx/2625   (12305 words)

  
 SIXNET Industrial Ethernet Switches - Rugged & Reliable   (Site not responding. Last check: 2007-10-19)
The most common redundant network topology with managed switches is to form a ring or loop.
This topology is ideal when you have advanced devices with dual Ethernet ports such as the SixTRAK IPm DCS Controller or EtherTRAK I/O Gateway.
The advantage to this topology over just a simple loop is that it affords the maximum bandwidth because of the direct connection to the "root".
www.sixnetio.com /html_files/products_and_groups/switches_rstp.htm   (967 words)

  
 2.4 Yoid Tree Management Protocol (YTMP)
Or, in the context of topology rather than root paths: Two members X and Y cannot change parents such that X's new parent is an offspring of Y, and Y's new parent is an offspring of X. This problem is not limited to pairs of members.
A loop also forms among three members X, Y, and Z if simultaneously X becomes an offspring of Y, Y an offspring of Z, and Z an offspring of X. This is shown in Figure 7, where any two of the three changes do not result in a loop, but all three together do.
Emergency loop avoidance is more general than coordinated loop avoidance in that emergency loop avoidance can be used whether or not the changing member has a parent.
www.isi.edu /div7/yoid/docs/ycHtml/node16.html   (2765 words)

  
 [No title]   (Site not responding. Last check: 2007-10-19)
Packet losses and transient loops can also occur in the case of a link down event implied by a maintenance operation, even if this operation is predictable and not urgent.
Since it can be assumed that the original topology was loop-free, Y will never use the link Y->X to reach the destination and hence the path(s) between Y and the destination are guaranteed to be unaffected by the topology change.
Deducing the topology change As has been described, a single event such as the failure or restoration of a single link, single router or a linecard may be notified to the rest of the network as a set of individual link change events.
www.ietf.org /internet-drafts/draft-ietf-rtgwg-ordered-fib-00.txt   (3415 words)

  
 BioMed Central | Full text | Fold classification based on secondary structure - how much is gained by including loop ...
With this motivation in mind we extend the linear structure similarity method based on secondary structure [18] by indicating which loops form parts of hairpins (these are short loops that connect the two strands of an anti-parallel β-sheet, we refer to them as closed loops).
A closed loop is a loop that starts and ends at one of the ends of an anti-parallel beta sheet.
A closed loop with interval {i + 1,..., j - 1} is represented as an annotation j - i at position ⌊(i + j)/2⌋.
www.biomedcentral.com /1472-6807/6/3   (5547 words)

  
 Network Topology
The ideas involved in network topology come from a branch of geometry (topology), which is concerned with the properties of a geometrical figure that do not change when the figure is drawn in alternate forms, where those alternate forms do not involve taking apart or joining together any parts of the figure.
Loop : a path where the ending node is the same as the beginning node.
The broken red line shows the loop that results when the link on the left edge of the tree is changed to a branch (as shown by the blue line).
venus.ece.ndsu.nodak.edu /ece/academics/courses/ee206/notes/cirtop.htm   (2311 words)

  
 University of Chicago Algebraic Topology Seminar
The group theoretic structure of the "universal operations" on certain families of single loop spaces is analyzed, and identified as a group of natural transformations.
I will describe the topology of the classifying space of the group of symplectomorphisms of a rational ruled surface in terms of the deformation theory of complex structures compatible with the symplectic form.
We prove that if X is a loop space and the integral homology of X is finitely generated as an abelian group, then X is homotopy equivalent to a closed, smooth, parallellisable manifold.
www.math.uchicago.edu /~jg/fall03topsem.html   (1187 words)

  
 SAN Solutions
LIHA Loop Initialization Hard Assigned frame; a hard assigned AL_PA that is indicated by a bit set and is the third frame transmitted in the loop initialization process after a temporary loop master has been selected.
LIPA Loop Initialization Previously Assigned; where the device marks a bit in the bitmap if it had not logged in with the fabric in a previous loop initialization.
LPB Loop Port Bypass; a primitive sequence transmitted by an L_Port to bypass the L_Port to which it is directed.
selam.com /san_solution/sansol-terminology.htm   (4611 words)

  
 A look at arbitrated loop
The point-to-point topology, while the least flexible solution because it is limited to the connection of only two nodes, is useful for connecting a single server to single disk array.
Configuring FC-AL in a loop topology presents several limits to the performance of the network because performance is affected by the number of devices attached to the loop.
The simplest hubs provide only a means to bypass ports not attached to the loop, while the more advanced devices feature a wide range of management options that can automatically sense, correct and report problems to the network administrator, as well as providing tools to monitor and configure devices remotely.
beradio.com /mag/radio_look_arbitrated_loop   (1115 words)

  
 Fibre Channel
Essentially, Fibre Channel, using the Arbitrated Loop topology, is simply being used as a replacement for SCSI.
LIP is transmitted by an L_Port after it powers on, or when it detects Loop Failure (loss of synchronization at its receiver).
LIP, LPB, and LPE are Primitive Sequences used in the Arbitrated Loop topoloby for initializing the Loop and enabling or disabling an L_Port.
www.recoverdata.com /fc_tutorial.htm   (8014 words)

  
 [No title]
Loop Proposals The proposals already presented to X3T11 have addressed the addition of isochronous capabilities, and techniques for increasing the total bandwidth, that can be supported in a loop topology.
"The goal is to extend FC loop topologies to support significant additional applications," said Horst Truestedt, of IBM (Rochester, MN) the International Representative of X3T11, Chief Architect of FC-AL, and the facilitator of this week's presentations to X3T11.
A decision is scheduled to be taken in December 1996 on which functionality from the various proposals is to be further developed.
www.ncits.org /press/1996/pr96079.htm   (865 words)

  
 Feedback Circuits
The three port quantities of the input network combine as a sum of voltages around a loop for which loop current is common, or as a sum of currents at a node for which the node voltage is common.
in the shunt (parallel) topology are nulled by shorting the common input node.
By choosing instead the error voltage (input to G) in the series topology or the error current in the shunt topology, summation is by Kirchhoff’s Laws alone.
www.innovatia.com /Design_Center/Feedback_Circuits.htm   (2863 words)

  
 Fibre Channel for Linux | Linux Journal
This kind of topology may be useful for connecting two machines that are physically separated by some distance and are in need of a dedicated high-bandwidth connection.
Every device on this loop now has access to the other devices on the loop as well as every device that is connected to the switch.
A loop connected to a fabric is known as a Public Loop.
www.linuxjournal.com /article.php?sid=4499   (2931 words)

  
 Acronyms   (Site not responding. Last check: 2007-10-19)
A 1-byte value used in the Arbitrated Loop topology used to identify L_Ports.
Used for buffer-to-buffer flow control, this determines the number of frame buffers available in the port it is attached to, i.e., the maximum number of frames it may transmit without receiving an R_RDY.
This Primitive Signal is sent by an L_Port which is currently communicating on the loop (i.e., it has won access to the loop or was opened by another L_Port which had won access to the loop) to close communication with the other L_Port.
www.emulex.com /ts/acronyms.htm   (2243 words)

  
 RFC 2625 - IP and ARP over Fibre Channel
Because of this, address validation is required after a LIP in a loop topology [7] or after NOS/OLS in a point-to-point topology [6].
The private loop may connect a number of devices (max 126) in a logical ring much like Token Ring, and is distinguished from a public loop by the absence of a Fabric Node participating in the loop.
For the Arbitrated Loop topology, with the destination NL_Port on the same AL, the source port must pick the destination port, determine its AL Physical Address, and "Open" the destination port.
www.packetizer.com /rfc/rfc2625   (12334 words)

  
 Page 2 Storage Area Networks Technology
The choice of topology is dependent on requirements in terms of scalability, required bandwidth and expected traffic patterns.
In the loop topology, the bandwidth is shared between all the nodes connected to the loop.
The loop can be wired node-to-node; however, if a node fails or is not powered on, the loop is out of operation.
www.wam.umd.edu /~dhancoc1/san_page2.html   (1714 words)

  
 Fibre Channel Group---> University of Minnesota   (Site not responding. Last check: 2007-10-19)
Arbitrated Loop A shared 100MBps fibre channel transport supporting up to a maximum of 126 devices and 1 attachment to a fabric.
LIP Loop Initialization Process; a means to get an AL_PA address,to indicate a loop failure, or to reset a node.
Topology The physical or logical arrangement of devices in a networked configuration.
gfs.lcse.umn.edu /fc/glossary   (1355 words)

  
 Fibre Channel Overview   (Site not responding. Last check: 2007-10-19)
A Fibre Channel topology in which frames are routed around a loop set up by the links between the nodes in the loop.
Although the fabric topology is more expensive, it provides both increased connectivity and higher performance; switches provide a full-duplex 100 (200) MB/sec point-to-point connection to the fabric.
This logical private loop fabric attach (PLFA) consists of multiple private arbitrated loops (looplets) that are interconnected by a fabric.
h30097.www3.hp.com /docs/updates/TCR51_FC/CHFCVRVW.HTM   (3100 words)

  
 Dr Carlo Kopp's Publications Archive
The simplest network topology which can be used is a simple ring, where a cable connects all devices in the loop, with the last device connected though to the first.
The alternative to the simple loop is the use of a hub or concentrator, which allows a physical star topology, while retaining a logical loop topology.
Gadzoox are touting the FCL1063TW Fibre Channel Arbitrated Loop Active Hub, which provides 9 copper interfaces at 1062.5 Gigabit/s, automatic failover and reconfiguration, optical adaptors may be fitted, and the device may be cascaded to connect up to 126 nodes.
www.csse.monash.edu.au /~carlo/SYSTEMS/Gigabit-IP-LAN-1097.htm   (2456 words)

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