Quantum World, Optics, Relativity, Telecoms, Food, Nature & Cricket

What Are The Basic Advantages Of MPLS-TP Over A Regular IP/MPLS Network?

2011-04-12T19:58:00.000+01:00

MPLS-TP, is a set of MPLS protocols that are still being discussed in IETF. It is supposedly a stripped down, "simplified" version of MPLS for transport networks with some of the original MPLS functions turned off: For xample, Penultimate Hop Popping (PHP), Label-Switched Paths (LSPs) merge, and Equal Cost Multi Path (ECMP).

MPLS-TP does not require MPLS control plane capabilities and enables the management plane to set up LSPs manually. Its OAM may operate without any IP layer functionalities.

An example of implementation is Cisco's Carrier Packet Transport (CPT) System, where Service providers can consider implementing industry’s first, standards-based Packet Optical Transport System (P-OTS) that unifies packet and transport technologies using MPLS-TP.

Benefits as quoted by Cisco:

Provides standards-based transport technologies and familiar operational models. Service providers can use a single unified interface for point-and-click provisioning of wavelengths and MPLS-TP label switch paths.
Simplifies the network by combining multiple functions into one. Service providers can reduce the number of network elements and interconnect ports by combining functions such as ROADM, TDM/OTN switching, Ethernet, and MPLS-TP in a single platform, drastically reducing space and power consumption, thus enabling greener networks.
Supports a comprehensive set of packet services for mobile backhaul, legacy TDM, Ethernet, and fiber services targeted at business and residential customers.
Enables an integrated IP/MPLS and MPLS-TP architecture with a single control plane and forwarding mechanism. This provides OpEx savings and allows service providers to set up simple connection-oriented paths for point-to-point or point-to-multipoint connections with in-band operations, administration, and management (OAM) and sub-50 millisecond automatic protection switching.

To summarise, the main properties of MPLS-TP defined by IETF and ITU-T are:

MPLS forwarding plane with restrictions
PWE3 Pseudowire architecture
Control Plane: static or dynamic Generalized MPLS (G-MPLS)
Enhanced OAM functionality
OAM monitors and drives protection switching
Use of Generic Associated Channel (G-ACh) to support fault, configuration, accounting, performance, and security (FCAPS) functions
Multicasting is under further study

There is still a bit of discussion up in the air, especially about the OAM part. For example, here's some insight from Mike Capuano's blog: http://blogs.cisco.com/sp/there-is-no-split-standard-in-mpls-oam/

The current general consensus seems to tend towards "The market will ultimately decide which is the right approach for MPLS-TP OAM."

Well, I guess we will wait and see :-)

IP Backbone Fast Re-Route Capability: Is this feature present on most carriers' MPLS VPN service?

2009-08-08T20:16:00.006+01:00

IP Backbone Fast Re-Route Capability: Is this feature present on most carriers' MPLS VPN service?

As far as I know most major vendors should have FRR implemented. I am sure Cisco and Juniper both does.

Multiprotocol Label Switching (MPLS) Fast Reroute (FRR) refers to local protection methods such as one-to-one and many-to-one (facility) backup. In the general, the term FRR has become a shorthand way of describing the entire spectrum of MPLS traffic protection mechanisms.

In general MPLS traffic protection for Resource Reservation Protocol (RSVP)-signaled label-switched path (LSP) failures is provided by several complementary mechanisms. These protection mechanisms include local protection (fast reroute, link protection, and node-link protection), and path protection (primary and secondary paths). Local protection in conjunction with path protection can provide minimum packet loss for an LSP, and control the way the LSP is rerouted after a failure.

Traditionally, both types of protection rely on fast detection of connectivity failure at the physical level. TE is usually enabled in the core network, where the capacity of the links is high. If a link or a router fails, traffic is rerouted around the failure. This rerouting happens for IP and for MPLS traffic relatively fast. However, even if the rerouting takes only a few seconds, it might mean that a lot of traffic is dropped to the point of failure because of the high capacity of the links. For certain traffic, such as Voice over IP (VoIP), this can be devastating for the service. Although links can potentially be protected at Layer 1—for example, with a mechanism called automatic protection switching (APS)—having a protection at the level of MPLS is best. APS is a well-known mechanism for protecting optical links. A disadvantage of APS is that for every protected link, a backup link and a card on either side are waiting idle until they are needed and the failing protected optical link is switched over to this backup link.

Link and node protection with TE is more efficient because an idle backup link for every protected link is not needed. Therefore, link and node protection used with TE is cheaper than an optical protection scheme. A backup tunnel for each protected link or node is created in advance. That means no time is wasted by having to signal the backup tunnel when the protected device fails. This time can be quite long because a path must be computed for the backup tunnel, and then it must be signaled. The following two explain the local protection schemes possible with TE: link protection and node protection. The two schemes have one thing in common: The repair is done as close to the point of failure as possible. Both methods provide local repair. As such, they are pretty fast and reroute the LSPs from the protected link onto the backup tunnel in tens of milliseconds. A number you might hear a lot is the 50-msec one. That is because this number is also referred to a lot when talking of the switchover time of SONET links. Link and node protection with MPLS TE is referred to as FRR.

Links:

Cisco:http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6557/mpls_te_frr.pdf

Juniper:http://www.juniper.net/techpubs/software/nog/nog-mpls-frr/frameset.htm

Quantum Information, Quantum Non-Locality, Computation and Teleportation

2009-08-08T19:51:00.005+01:00

Quantum information, Computation and Teleportation has become an independent fast growing research field. A computer is a physical device that helps us process information by executing algorithms. An algorithm is a well-defined procedure, with finite description, for realizing an information-processing task. An information-processing task can always be translated into a physical task.

Quantum information processing is the result of using the physical reality that quantum theory tells us about for the purposes of performing tasks that were previously thought impossible or infeasible. Devices that perform quantum information processing are the " quantum computers".

And as far as Quantum Communication is concerned, basically there are two communication protocols, which, as is known so far, can be implemented using quantum mechanics: Super-Dense coding and Quantum Teleportation.

The basic idea behind Quantum Teleportation is the following: Let's say Alice has particle 1 in a certain quantum state, a qubit A ( I am refraining from throwing in mathematical representations as that is not easy to do here) which has two orthogonal states { 0> and 1> } with complex amplitudes. She wishes to deliver this state to Bob but cannot do so directly ( let's say). Now, according to the postulates of QM ( quantum mechanics) any measurement performed by Alice on her particle will destroy the quantum state at hand without giving Bob all the necessary info required in order to reconstruct the quantum state. Then how do they communicate? The way around is to use an ancilliary pair of "ENTANGLED" particles, say, X and Y ( the EPR pair, Einstein, Podolsky & Rosen, Physics Review, 1935, 47, 777-780), where Alice has particle X and Bob particle Y. The EPR pair is also knows as the Bell state. Such a state, for sake of intuitive experimentation, would have to be created ahead of time, when the qubits are in a lab together and can be made to interact in a way which will give rise to the entanglement between them. After the state is created, Alice and Bob each take one of the two qubits away with them. Alternatively, a third party could create the EPR pair and give one particle to Alice and the other to Bob. If they are careful not to let them interact with the environment, or any other quantum system, Alice and Bob's joint state will remain entangled. This entanglement becomes a resource which Alice and Bob can use to achieve protocols such as super-dense coding and teleportation.

For quantum teleportation, the scenario is that Alice wishes to communicate the state of a qubit to Bob. Suppose Alice only has a classical channel linking her to Bob. To send the state of a qubit exactly, it would seem that Alice would either have to send the physical qubit itself, or she would have to communicate the two complex amplitudes with infinite precision. However, if Alice and Bob possess an entangled state this intuition is wrong, and a quantum state can be sent exactly over a classical channel. Teleportation is a protocol which allows Alice to communicate the state of a qubit exactly to Bob, sending only two bits of classical information to him. Technical implementation of many qubit systems has been, so far, a challenge especially the necessity to have a shared EPR pair for every qubit ( or electron, photon, nucleon) whose state is to be teleported. Single qubit states have been successfully teleported in more than one laboratory using optical and NMR techniques ( see references 1 and 2).

THAT leads us to Quantum non-locality of EPR pairs which is so impressive and difficult to accept that it does appear to be on the verge of the mystical as it seems to demonstrate existence of superluminal effects, in other words, exchange of signaling at a speed faster than light. Efforts to clarify non-locality using the transactional interpretation of quantum mechanics ( EPR experiments), and the possibility of superluminal effects (e.g., faster-than-light communication) from nonlocality and non-linear quantum mechanics is still under investigation ( Prof. J. Cramer's group at University of Washington for e.g.).

Excited atoms often produce two photons in a process called a "cascade" involving two successive quantum jumps. Because of angular momentum conservation, if the atom begins and ends with no net angular momentum, the two photons must have correlated polarizations. When such photons travel in opposite directions, angular momentum conservation requires that if one of the photons is measured to have some definite polarization state, the other photon is required by quantum mechanics to have exactly the same polarization state, no matter what measurement is made.Such correlated photon pairs are in an "entangled" quantum states. Experimental tests of Bell's theorem, i.e, the "EPR experiments", usually use entangled photons from such an atomic cascade.

It just so happens that quantum mechanics and Bell's Theorem make qualitatively different predictions about EPR measurements. In other words, the intrinsic nonlocality of quantum mechanics has been demonstrated by the experimental tests of Bell's theorem. It has been experimentally demonstrated that nature arranges the correlations between the polarization of the two photons by some faster-than-light mechanism that violates Einstein's intuitions about the intrinsic locality of all natural processes. What Einstein called "spooky actions at a distance" are an important part of the way nature works at the quantum level. Einstein's faster-than-light spooks cannot be ignored.

Question: Can quantum nonlocality be used for faster-than-light or backward-in-time communication? Perhaps, for example, a message could be telegraphed from one measurement site of the EPR experiment to the other through a judicious choice of which measurement was performed. The simple answer to this question is "No!" Briefly, the quantum operators characterizing the separated measurements always commute, no matter which measurement is chosen, so non-local information transfer is impossible.

HOWEVER, this prohibition against superluminal communication, as stated above, is a part of standard quantum mechanics. This is broken if quantum mechanics is allowed to be slightly "non-linear", a technical term meaning that when quantum waves are superimposed they may generate a small cross-term not present in the standard formalism.

The onset of non-linear behavior is seen in other areas of physics, e.g. laser light in certain media, and, it is suggested by Nobel Laureate Steven Weinberg that this might also be present but unnoticed in quantum mechanics. Weinberg's non-linear QM subtly alters certain properties of the standard theory, producing new physical effects that can be detected through precise measurements.

So, the answer to the query of "Theoretical Possibility" of teleportation (and Beam-me-up Scotty type transport) as it stands today would be an emphatical "YES". Practically, it has not been proven to be so YET. But that does not mean quantum non-locality or entanglement cannot be faster than light in vacuum. It just means that we have, so far, been unable to prove it to be so.

Briefly, at a quantum level it can happen that two objects form a single entity, even at arbitrarily large separation from each other. A classical (macroscopic) physical object broken into pieces can be described and measured as separate components. An n-particle quantum system cannot always be described in terms of the states of its component pieces. For instance, the state I00> + I11> cannot be decomposed into separate states of each of the two qubits . Any attempt to view this quantum entity as a combination of two indepnedent objects fails, UNLESS the posibility of signal propagation at superluminal speeds is allowed.

An entangled system consisting of two subsystems can't be described as the product of quantum state of two subsystems. In this sense the entangled system is considered as inseparable and non-local. The creation of entanglement between two long-lived and distant systems is important and challenging role in quantum information research. There are various schemes of the employing entanglement for quantum computation, teleportation, optical memory, cryptography, and error correction.

The EPR paradox introduced the concept of entanglement in quantum optics. Modern quantum mechanics contains the novel and counterintuitive features as witnessed in the famous dialogue between Niles Bohr and Albert Einstein. Einstein argued that quantum mechanics is incomplete. In 1935, A. Einstein, B. Podolsky and N. Rosen proposed the EPR paradoxical Gedankenexperiment. Consider a quantum system consisting of two particles such that the individual momentum or position isn't well defined. But the sum of the position that is their center mass and the difference of the momentum that is their individual momentum in the center mass system are well defined. Assuming the two particles are separated in arbitrary distances. The measurement of either momentum or position of particle 1can immediately implies the precise momentum or position of particle 2. The measurement of particle 1 doesn't have any influence on particle 2 (locality condition). Thus the property of particle 2 is independent on of the measurement performed on particle 1.

In the famous reply from Bohr, he argued that two particles in EPR case are always part of quantum system and thus measurement on one particle changes the possible predictions that can be made for the system thus for the other particle.

Since then physicists pay more attention to the entangled state especially after invention of laser. Conventionally entanglement is realized in the microscopic system of a few particles like the trapped ions or atoms. There exist several sources of entangled quantum systems. Entangled ions have been prepared in electromagnetic Paul traps. Controlled entanglement between nuclear spins within a single molecule can be achieved by the technique of nuclear magnetic resonance. In quantum optics there are two classes of the entanglement: (a). Entanglement between single photon and (b). Between the quadrature components of light beam.

Parametric down-conversion processes have been utilized for creation a pair of entangled photons. Two different kinds of polarization entanglement between the two photons-parallel and orthogonal can be made by two type of the phase matching scheme in the down-conversion. Varying the phase relation to make the emission of the two photons in different frequency (momentum) and different direction (mode) can also achieve the momentum entanglement. A so-called time entanglement can also be observed if we can vary the phase of the two light path. The quadature component entanglement proposed by L. Vaidman, further elaborated on by Braubstein and Kimble and experimentally realized at Caltech.

A solid step towards a Quantum Internet has been taken by Prof. Seth Lloyd of MIT and Prof. Prem Kumar of NW University by establishing quantum logic gates with "entangled" photons. Please see the link from MIT Tech Review and UoW. The rest should be history in the making…

In my very humble personal opinion, the real- life work in stuff like quantum teleportation (QTP) and quantum non-locality is not really as far away as it seems, especially if the tech-sector biggies ( though IBM and possibly HP are doing some work in their research labs) decide to invest in the research of the same. Besides lack of solid and steady funding, I think development in this area has suffered to some extent because most students of Physics lack a bridge to the realistic world of Communication technology and most telecom engineers lack a thorough insight into Quantum Mecahnics and hence the inspiration to go ahead dissappears quickly.

The Quantum World and manipulation of it perhaps require a bit a of a leg-up in terms of knowledge, insight and application from the world of semiconductor chip based computers that we have known so far. We need to bridge this gap. There is decreasing money in research in this field probably due to scepticism among other reasons ( we did the same with Controlled & Cold Fusion research couple of decades back and almost shut down the most promising source of almost everlasting cheap energy). This is a science that, if successfully implemented, will break all known barriers of technology. But very little Industrial interest is openly exhibited at present time. Physics of subjects like quantum cryptography offers not a "quantum algorithm" or a "quantum software" but a solution based on the quantum system themselves. Technology connected directly to mother nature…

Links:

http://faculty.washington.edu/jcramer/NLS/NL_signal.htm
MIT Tech Review: http://www.technologyreview.com/Infotech/20565/?a=f

References:

1) A. Galindo and M.A. Martin-Delgado: Infomration and Computation: Classical and Quantum Aspects, 74:347-423,
2) Michael A. Nielsen and I. L. Chuang, Quantum Information and Communication. Cambridge University Press, 2001
3) P. H. Eberhard, (1977) Nuovo Cimento 38B, 75.
4) P. H. Eberhard, (1978) Nuovo Cimento 46B, 392
5) Steven Weinberg, (1989) Physical Review Letters 62, 485.
6) Joseph Polchinski, (1991) Physical Review Letters 66, 397.

LDP/TDP Required with RSVP for MPLS TE?

2009-06-25T09:27:00.006+01:00

I was recently asked: Is it possible to eliminate the use / enabling of LDP in MPLS networks while using RSVP for MPLS Traffic Engineering?

The only response I could hack-up at that point in time is the following:

Theoretically, for TE, RSVP with TE extensions takes care of the distribution of the MPLS labels and we do not need to configure Label Distribution Protocol (LDP) on the interfaces. Therefore, the MPLS network does not strictly need to have "mpls ip" on the interfaces, if TE is deployed. However, if you do not deploy TE to carry ALL traffic from ingress LSRs to egress LSRs ( for example, http://wiki.nil.com/MPLS_Traffic_Engineering_in_MPLS_VPN_environment), then you need LDP to avoid unlabeled traffic in the core network. MPLS VPN traffic, for instance, needs to be labeled at all times in the core network or it can demonstrate "unpredicable behaviour".

One of the problems of having a mix of RSVP and non-RSVP (LDP) traffic on a link is that bandwidth accounting is liable to break. A common misconception is that RSVP traffic is somehow special because it was set up with Resource Reservations. This is not true. The RSVP reservation exists in control plane only and no forwarding resources are actually set aside for it.

Inside Cisco IOS, a TE database is built from the TE information that the link state protocol sends. This dataset contains all the links that are enabled for MPLS TE and their characteristics or attributes. From this MPLS TE database, path calculation (PCALC) or constrained SPF (CSPF) calculates the shortest route that still adheres to all the constraints (most importantly the bandwidth) from the head end LSR to the tail end LSR. PCALC or CSPF is a shortest path first (SPF) algorithm modified for MPLS TE, so that constraints can be taken into account. The bandwidth available to TE and the attributes are configurable on all links of the networks. You configure the bandwidth requirement and attributes of the TE tunnel on the tunnel configuration of the head end LSR. PCALC matches the bandwidth requirement and attributes of the TE tunnel with the ones on the links, and from all possible paths, it takes the shortest one. The calculation is done on the head end LSR.

The intermediate LSRs on the LSP need to know what the incoming and outgoing labels are for the particular LSP for that TE tunnel. The intermediate LSRs can only learn the labels if the headend router and intermediate LSRs signal the labels by a signaling protocol. In the past, two signaling protocols were proposed: RSVP with extensions for TE (RSVP-TE) and constraintbased LDP (CR-LDP). Cisco IOS has RSVP with extensions for signaling MPLS TE tunnels and never had an implementation of CR-LDP. At the Internet Engineering Task Force (IETF),consensus was reached to carry on with developing RSVP as the signaling protocol for MPLS TE and to stop further development on CR-LDP. This was documented in RFC 3468, “The Multiprotocol Label Switching (MPLS) Working Group Decision on MPLS Signaling Protocols.”

The following is a quotation from the abstract of that RFC:

“This document documents the consensus reached by the Multiprotocol Label Switching (MPLS) Working Group within the IETF to focus its efforts on “Resource Reservation Protocol (RSVP)-TE: Extensions to RSVP for Label-Switched Paths (LSP) Tunnels” (RFC 3209) as the MPLS signalling protocol for traffic engineering applications and to undertake no new efforts relating to “Constraint-Based LSP Setup using Label Distribution Protocol (LDP)” (RFC 3212).”

References:

Microquasar (?) on Google Sky in Leo ?

2009-04-21T15:25:00.036+01:00

[ Click on images to make them larger]
I saw the following on Google Sky at coordinates 09:47:59, 13:16:50. The object has, what seem like blue jets. The image stands out more than anything else in the whole Leo constellation. To see it Go to the left bar options on Google Sky. Type in the following coordinates in the search box: 09:47:59, 13:16:50

Then, go to
--> Featured Observatories
--> IRAS Infrared Sky
--> IRAS Infrared Sky
--> IRAS Overlay

OR you can just visit http://www.google.com/sky/

Type in 09:47:59, 13:16:50. Click on Infrared. You may need to adjust distance settings to actually see it.

Fig.1 Object at Google Sky at 09:47:59, 13:16:50

You need to activate the Infrared (IRAS) overlay. Otherwise it is not visible. Without IRAS, you see the nearby Planetary Nebula IRAS 09452+1330 as a red dot, also in Leo.

Fig. 2 IRAS 09452+1330 at 09h 47m 57.4s +13° 16' 44" (Leo).

At first glance the object in question looks like a text-book copy of a Microquasar ( something like a GRO J1655-40). It seems to have the jets of relativistic matter being ejected perpendicularly alongwith at least one Radio Lobe that I "think" i see on top in faded blue. But I am not able to find any official reference to it anywhere.

Note: Please keep in mind that these are photographs taken in 2007. Most likely the coordinates of the object have changed by now.

First, I thought it could be IRAS 09452+1330, which is listed as a Planetary Nebula (Peanut Nebula), hence PK designation. A search takes us to http://www.schoenball.de/astronomie/projekte/ppn/ppn.htm , where the following data is listed, (in German) :

Objekt Name Rektaszension Deklination andere Bezeichner
CW Leo Peanut Nebula 09h 47m 57.4s +13° 16' 44" IRAS 09452+1330

From the above data, it is seems that the coordinates of the Nebula "CW Leo" also known as "Peanut Nebula" is slightly different from the numbers presented above ( 09:47:59, 13:16:50)

No.1) 09h 47m 57.4s +13° 16' 44" (from the above table)

Instead of

No.2) 9h 47m 59sec +13h 16m 50s ( object visible in Google Sky IRAS overlay)

The difference is important because both coordinates are supposed to refer to the same object, but the coordinates No.1 point to an object that is also visible on Google Sky without the IRAS overlay, while the coordinates No. 2 point to a dark region in the sky if the IRAS overlay is not present. I think ( I maybe wrong) that the planetary nebulae are usually visible without the IRAS overlay. If so, then the conclusion leads to the fact that the above coordinates cannot be explained as belonging to the "CW Leo" planetary nebula and therefore must belong to "something else".

That got me thinking that it could be a Microquasar. But as mentioned before, I cannot find any references anywhere about it. And it seems close enough in Leo. It seems quite large, in fact comparable in size to Saturn ( at least by Google Sky's scales).

Fig. 3. Saturn and the object in Leo constellation as taken in 2007

Also, I found this on NASA from November 2008: http://science.nasa.gov/headlines/y2008/19nov_cosmicrays.htm

"Nov. 19, 2008: An international team of researchers has discovered a puzzling surplus of high-energy electrons bombarding Earth from space. The source of these cosmic rays is unknown, but it must be close to the solar system and it could be made of dark matter......The least exotic possibilities include, e.g., a nearby pulsar, a 'microquasar' or a stellar-mass black hole—all are capable of accelerating electrons to these energies. It is possible that such a source lurks undetected not far away."

Following link from Caltech gives us some idea about colours of IRAS: http://coolcosmos.ipac.caltech.edu/image_galleries/legacy/iras_orion/caption.html

"... New processing techniques have been used to enhance
faint details and remove the instrumental artifacts (stripes) seen in earlier
IRAS images. The warmest features, e.g.~the stars, are brightest at 12
microns. This emission is coded blue. The interstellar dust is cooler and shines brighter at 60 microns
(coded green) and 100
microns (coded red)."

So, it appears that usually stars and the galactic centers show up as blue on IRAS' images. The object in question is shown as a large area of blue which is centered at a small green region that is only visible after zooming many times (on Google-earth). The fact that this object is not visible without the IRAS overlay indicates that it does not emit light very intensely or at all and the fact that it's blue on IRAS indicates that it's quite hot.

I intend to keep my eye open and see what comes up next :-)

Fig 4. Close up of the "Eye"
Fig 5. MicroQuasar ?

Fig 6. Object with saturn in Leo

Fig. 7. Another view

Fig. 8. The "Iris"

ELECTROMAGNETIC TRAPPING OF COLD ATOMS

2009-04-17T14:01:00.002+01:00

ELECTROMAGNETIC TRAPPING OF COLD ATOMS

Abstract. The review describes the methods of trapping cold atoms in electromagnetic fields and the fields combined of electromagnetic and gravity fields. We discuss first the basic types of the dipole radiation forces used for cooling and trapping atoms in the laser fields. We outline next the fundamentals of the laser cooling of atoms and classify the temperature limits for basic laser cooling processes. The main body of the review is devoted to discussion of atom traps based on the dipole radiation forces, dipole magnetic forces, combined dipole radiation-magnetic forces, and the forces combined of the dipole radiation-magnetic and gravity forces. Physical fundamentals of atom traps operating as the waveguides and cavities for cold atoms are also considered. The review ends with the applications of cold and trapped atoms in atomic, molecular and optical physics.

1. INTRODUCTION

The trapping of atoms in a restricted space volume is a fundamental physical problem of considerable interest from the standpoint of both the performance of the physical investigations with small amounts of atoms and the development of new technologies based on the localization of the spatial motion of atoms. Important physical applications of the methods of trapping atoms in three-dimensional spatial regions include studies into the spectral properties of small amounts of atoms, including counted numbers of radioactive atomic isotopes, improvement of the accuracy and sensitivity of spectral measurements, and studies of quantum-statistical effects in atomic ensembles at low temperatures, such as the Bose-Einstein condensation. No less important physical and technological applications may be associated with the trapping atoms in one or two dimensions, allowing atomic waveguides and cavities to be developed. Important technological applications are expected to ensue from the use of trapped atoms in the atomic frequency and time standards.

In the course of the many decades that this problem has been discussed, numerous physical ideas were put forward that could be used either for trapping atoms in three-dimensional regions of space or for trapping atoms in one or two dimensions. In essence, the practically developed methods appeared to be based on the use of the forces of electric dipole interaction of atoms with quasiresonance laser fields and (or) magnetic dipole interaction of atoms with static magnetic fields. In a sense, the main methods of trapping neutral atoms proved to be similar to those for trapping charged particles (electrons, protons, atom ions). To trap the latter, use is made of electromagnetic traps formed by inhomogeneous radio-frequency fields (Paul traps) or inhomogeneous stationary electric and magnetic fields (Penning traps) (Dehmelt, 1967, 1969; Paul, 1990).

From the physical standpoint, all the known techniques for trapping neutral atoms can be classed with but a few basic methods. These basic methods are: optical trapping using the forces of electric dipole interaction between atoms and laser fields, magnetic trapping based on the use of the forces of magnetic dipole interaction, mixed magneto-optical trapping using simultaneous interaction between atoms and magnetic and laser fields, and also mixed gravito-optical and gravito-magnetic trapping.

Historically, the first to be discussed were the methods of magnetic trapping. The very first suggestions on the possibility of electromagnetic trapping of atoms were already made when the first experiments were conducted on the deflection of atomic beams by a nonuniform magnetic field (Stern and Gerlach, 1921). The development of the idea of the magnetic deflection of atoms and molecules led to the appearance in the 1950s of the hexapole magnetic lenses and hexapole magnetic traps for particles with a permanent magnetic moment (Friedburg and Paul, 1951; Lemonick et al., 1955). These traps were successfully used to trap ultracold neutrons (Kugler et al., 1978; Golub and Pendlebury, 1979; Kugler et al., 1985). Many types of traps for particles with a permanent magnetic moment, starting with the most simple quadrupole trap and ending with the fairly complex Ioffe trap, were discussed in the works on plasma physics (Gott et al., 1962; Artsimovich, 1964; Krall and Trivelpiece, 1973). Concrete magnetic trap arrangements for trapping atoms started to be discussed in the 1960s (Vladimirskii, 1960; Heer, 1963; Letokhov and Minogin, 1980; Pritchard, 1983; Metcalf, 1984; Bergeman et al., 1987).

--
"Education is what remains after one has forgotten everything he learnt in school" - Albert Einstein

...to be continued as soon as I figure out how to post Greek symbols and formulas on this blog template :-)...

Major differences between service providers' MPLS networks?

2009-04-01T19:48:00.012+01:00

I was asked recently the following question while I was at a customer's: What are some major differences between service providers' MPLS networks?

Historically, tag switching ( now called Label) was first proposed as a way to move IP packets more qickly than was possible with conventional routing. But, soon after implementations, it became apparent that any increase in speed was very slight. What really allowed MPLS to grow as an infrastructure technology was that it could provide new IP based services such as VPN's, Traffic Engineering ( TE) etc.

MultiProtocol Label Switching architecture, as discussed in IETF RFC 3031, combines the benefits of the hardware packet switching approach of ATM and the Layer 3 approach of IP. In traditional IP routing, a packet is assigned in each router to a particular flow corresponding to a class of routing or a forward equivalence class (FEC). In contrast, in MPLS this assignment is performed once at the entry, or ingress, to the MPLS network. In an MPLS network, the FEC is identified by the network exit destination, or egress, and by the ingress label-switched router (LSR).

The MPLS architecture separates the control information for packets required for packet transfer itself; that is, it separates the control and data planes. The data plane is used for the transport of packets (or label swapping algorithm), and the control plane is analogous to routing information (for example, the location to which to send the packet). This capability is programmed into hardware by the control plane. This separation permits applications to be developed and deployed in a scalable and flexible manner. Examples of applications that are facilitated by MPLS technology include the following: MPLS QoS, BGP VPNs Border Gateway Protocol (BGP), Traffic engineering Traffic engineering ( enables one to control traffic routing via constraint-based routing), Multicast routing Protocol Independent Multicast (PIM), Pseudowires [These can be used to evolve legacy networks and services, such as Frame Relay, ATM, PPP, High-Level Data Link Control (HDLC), and Ethernet], Generalized MPLS (GMPLS).

Services offered by Service Providers ( SP's) running MPLS on their backbone may include the following:

Layer 2 VPNs
Layer 3 VPNs
Remote Access and IPSec
Integration with MPLS
VPNs
MPLS Security
Traffic Engineering
Quality of Service
Multicast and NGNs
IPv6 over MPLS

The MPLS models adopted by service providers (SP) of broadband services depend on the services offered and also on the models adopted according to customer demands. The services provided have changed significantly through the last few years as techology has progressed. For example, many wholesale providers who offered ATM as access links now have moved on to Gigabit Ethernet.

For example, two of the most common broadband SP's would be the following:

1) Retail Provider: Any provider thats sells services to an end-user which can be business or residential. Usually they would lease bandwidth from a wholesale provider.

2) Wholesale Povider: Any operator that sells services to other network operators. In context of the current broadband world, the wholesaler is usually whoever owns the subscriber plant ( wires, cables etc.)

In between the subscriber and their "ISP" is the wholesale provider who owns actually owns and operates the access network, for e.g, DSL, Cable, Ethernet etc. Of course, for an IP network, these are just different types of access.

Several applications that are facilitated by the implementation of MPLS include:

1) MPLS QoS: Implements quality of service mechanisms, such as differentiated service, which enables the creation of LSPs with guaranteed bandwidth.

2) Layer 3 VPN: Uses BGP in the service provider's network with IP routing protocols or static routing between the service provider and the customer. The BGP protocol is used to exchange the FEC-label binding.
3) Traffic engineering: Uses extensions of IS-IS or OSPF to distribute attributes in the network. Control processes the FEC-binding through RSVP. Traffic engineering enables you to control traffic routing and thus optimize network utilization.

4)Multicast routing via PIM: The protocol used to create FEC tables; extensions of version 2 of the PIM protocol are used to exchange FEClabel binding.

5) Layer 2 VPN: Can be created via a Layer 2 circuit over MPLS, commonly referred to as Any Transport over MPLS. Layer 2 VPNs, therefore, use Layer 2 transport as a building block to construct a Layer 2 VPN service that includes auto
configuration, management, QoS, and so on.

Architectural Components and choices for SP's:

Scaling MPLS VPNs to Multi-AS, Multi-Provider, and Hierarchical Networks:

Inter-AS VPNs:

RFC 4364 discusses the ability to build MPLS VPNs across the autonomous system
boundaries. The three basic models discussed in RFC2547bis for Inter-AS
connectivity are as follows:

1) Back-to-back VPN connectivity between ASBRs
2) VPNv4 exchange of routes and peering between ASBRs
3) IPv4 exchange of routes and peering between
ASBRs
All three models focus on propagating VPN routes from one AS to the other AS. The first model is a simple one in which the ASBRs connect back to back via logical circuits or VLANs one per VRF. The back-to-back connections enable VPN connectivity and the exchange of routes between ASBRs on a per-VPN basis. For example, if ASBR1 and 2 need to exchange routes for 10 VPNs, 10 logical circuits exist between ASBR1 and ASBR2one for each VPN.

Carrier Supporting Carrier:

Another method of scaling MPLS VPNs is to create hierarchical VPNs. Consider a national or international carrier that is selling a VPN service to smaller stub carriers. The smaller stub carriers might in turn be selling another MPLS VPN service to end users (enterprises). By nesting stub carrier VPNs within the core or national carrier VPN, a hierarchical VPN can be built. With the CSC mode described in RFC 2547bis, the stub carrier VPNs and their routes do not show up in the core carrieronly the stub carrier IGP routes are part of the core carrier VPN. So, the core carrier does not need to learn or understand end user routes because the end user of the core carrier is the stub carrier. The core carrier needs only to provide VPN connectivity so that the core carrier's CEs (ironically, they are stub carrier PEs) are reachable. These
CEs are called CSCCEs, whereas the PE that connects to the stub carrier and has MPLS enabled on the PE-CE link is called the CSCPE.

Deployment Guideline considerations will involve the following summary guideline:

Centralizing address translation makes keeping track of address assignment easier. Multiple NAT PEs might be required for load balancing. If this is the case, make sure public address pools do not overlap. One of the possible disadvantages to centralizing is the amount of redundancy that can be achieved by replication. For example, in a noncentralized environment, one gateway/server failure can result in an outage of only that VPN's service. However, in a centralized environment, a single gateway/shared PE failure can affect multiple VPNs. This drawback can be easily overcome by having multiple PEs that serve as shared gateways, which provide services to the same VPNs. So, you can provide redundancy with shared gateways.
If VPNs that use overlapping private address space need to access a shared services segment, make sure that private address space is translated somewhere in the path.
NAT impacts CPU utilization to a degree. Some protocols are more CPU-intensive than others. Therefore, the type of translation being performed could have significant performance impact. The impact is less for newer particle-based routers and more powerful routers.
As the number of translation entries increases, the throughput in terms of packets per second (PPS) decreases. The effect is negligible for less than 10,000 translation table entries.
The rate at which a router can add a new translation table entry decreases as the number of entries in the translation table increases.
As the number of translation entries in the translation table increases, the amount of memory used increases.

In addition to the above, there must be considerations regarding the following tools and policies:

Management, Provisioning, and Troubleshooting
Equipment Scalability Versus Network Scalability

Finally, the basic arichitecture and mode of service will probably depend on customer demand and SP's commitment to deliver. Here is a small list of some of the things that customers want:

More service selections
Better quality
Ease of
migration
Ease of deployment
Ease of maintenance
Lower cost
Fewer hassles

Service Providers want all of the above, plus:

High-margin accounts
Rapid recovery
No loss of
service
99.99999% reliability

Enterprises want:

A simpler, easier network to manage

Enterprise networks range in consistency from very stable to constantly changing.
Companies on growth trends are building new facilities and acquiring other businesses. They want ease of intermigration and implementation. Changes must be ably employed within their limited maintenance windows. Their data centers must run flawlessly.

References:

1) MPLS-Enabled Applications: Emerging Developments and New Technologies by Ina Minei, Julian Lucek

2) MPLS and Next-Generation Networks: Foundations for NGN and Enterprise Virtualization by Azhar Sayeed; Monique Morrow

3) Building MPLS-Based Broadband Access VPNs by Kumar Reddy

ExtraTerrestrials Finally Found!

2009-03-17T10:28:00.004Z

Scientists find new bacteria species in Space:

The Earth layer where bacteria species were found receive high ultraviolet radiation
Three bacterial colonies are new species, ISRO says
ISRO calls study "positive encouragement" to continue quest for origin of life

NEW DELHI, India (CNN) -- Indian scientists have discovered three new species of bacteria in Earth's upper stratosphere that are resistant to ultraviolet radiation, researchers said.
The bacteria do not match any species found on Earth. They were found in samples that scientists collected when they sent a balloon into the stratosphere, the Indian Space Research Organization (ISRO) said in a statement Monday. That layer of the Earth receives heavy doses of ultraviolet radiation, enough to kill most organisms.

In their analyses of the retrieved samples, microbiologists detected 12 bacterial and six fungal colonies. Of them, three bacterial colonies were new species, the ISRO said.
Indian scientists named one of them Janibacter hoylei, after astrophysicist Fred Hoyle.
"While the present study does not conclusively establish the extraterrestrial origin of microorganisms, it does provide positive encouragement to continue the work in our quest to explore the origin of life," the ISRO said.

Quantum Dots and Spintronics for Quantum Computing and Communication

2009-02-18T17:11:00.002Z

It is proposed that an entirely new form of information processing, namely quantum computing, could be possible[1] if the states of electron spins in a given solid can be synthesised (or created), manipulated and measured at the single-quantum level. A spin-quantum dot architecture for a quantum computer, thereby indicating a variety of first generation nanostructures, is reviewed. A spin filter and spin detection mechanism [3] at the single-spin level which can be used for read-in and read-out in conventional as well as in quantum computer gates is discussed. Addressing the feasibilty of quantum communication with entangled electrons [4,5], Einstein-Podolsky-Rosen pairs are discussed.

A way of using Quantum Dots (QD) would be to look at it as a producer of electric charge and use the same electric charge as a qubit. Semiconductor QD's can serve as 3-Dimensional boxes with electrostatic potentials which confine charge quanta. Unfortunately, uncontrolled distant charged motion leads to dephasing. Also scattering reactions such as those triggered by phonon interactions cause coherence times to be relatively short for charge states.

Obtaining of Entangled Photons from Quantum Dots in a cavity for usage in Quantum Computation & Communications is steadily growing in popularity. Some progress has been done in this area [ e.g. Bensaon et. al, 2000; Stace et. al,2003; benycouf et. al., 2004; Kumar et. al., 2004]. It is also expected that there will be other such sources soon. A very demanding but also very promising area, while implementing Quantum Communication, is generating fluorescence photons by manipulating trapped atoms or ions. This is closely connected to Quantum Computation with trapped ion systems and cavity QED systems. A reference source for these techniques is, for example, "Focus On Single Photons On Demand " by Grangier et. al. 2004.

Teleportation of single qubits have already been achieved by multiple groups in laboratories using entangled photons ( for e.g., see ref. Galindo et. al below).

[1] D. Loss, D.P. DiVincenzo, Phys. Rev. A 57 (1998) 120; cond-mat/9701055.
[2] G. Burkard, H.A. Engel, D. Loss, cond-mat/0004182 (Review).
[3] P. Recher, E. V. Sukhorukov, D. Loss, cond-mat/0003089.
[4] D. Loss, E. Sukhorukov, Phys. Rev. Lett. 84, 1035 (2000).
[5] G. Burkard, D. Loss, E. Sukhorukov, to appear in Phys. Rev. B RC, cond-mat/9906071.
[6] A. Galindo and M.A. Martin-Delgado: Infomration and Computation: Classical and Quantum Aspects, 74:347-423, 2002

Best Bandwidth Solution(s) For Video ?

2009-02-18T10:31:00.009Z

I was recently asked the following: What Are The Best Bandwidth Solution(s) For Video Conferencing & Multi-Media Applications? What bandwidth solution (T1, DS3, OCx/Sonet, etc.) would you recommend for a small, medium, and large size business ... and why .... to cover videoconferencing and multi-media applications? No other specifics to offer ...Rather I want your thoughts and recommendations for what a company should plan to (small, medium, and large).

All I could rake up from the depths of the foggyness of my mind is the following: Without knowing the specifics, it is hard to provide a precise answer, but, one can still grope around for a systematic method for calculating required bandwidth. Once you know the bandwidth requirement, then it is all about the balancing act between budget restrictions and providing the required performance. Rule of thumb, as I know it is as follows:

1. Calculate the peak external link bandwidth requirements (inter-office data transfer, video conferencing, email transfers. With attachments running in tens of megabytes, email traffic can’t be ignored these days.).

2. Real time applications being most jitter and delay sensitive - so you have to make sure that you will have enough bandwidth when they need it. The bandwidth of video depends on the mpeg profiles used (without going into specific, generally 1.5 Mbps can give you very good video on a PC (equal to VCD quality). HDTV images can take about 20 Mbps – but that is domain more reserved for IP TV service providers). Most current users of interactive video communications will be happy with the images coded and transmitted @ 512 Kbps. This includes audio and video as well as control signaling. So, one should provision at least 512 Kbps per video stream, and more the better (I would say 1.5 Mbps is the good if you are a big organization and use a large TV for video conferences)). So, multiply bandwidth for a single stream with number of parallel streams required. Now that determines the total peak real time usage.

3. There is no specific rule but wise men with experience advise to keep the peak real time within 60 to 75% of network bandwidth available leaving remaining capacity for background traffic. In a small organization of 5 people - it is easy to tell people not to download gigabyte attachments when video conferencing is going on , but in larger organization it is hard to enforce such things except with router policies (assuming they have QoS support), and you can deal with occasional unhappy users.

4. Now, once you know your bandwidth requirements, it is time to talk to the network operator how they can provide that bandwidth in the most cost effective way.

I'd say it also dedends on what kind of service and QoS you are looking at. For example, when you say "video" I suppose you mean video conferencing and not something like VoD. The Bandwidth requirements will vary according to your service requirements.

For example: For IPTV services, the image quality depends on the encoding deployed: MPEG-2 consumes approx. 3.75 Mbps, whereas MPEG-4 needs approx. 2 Mbps for the same high-quality image production. Also broadcast TV is delivered using IP Multicast which makes the bandwidth required dependent on the number of channels offered and the encoding rate. 200 channels of MPEG-2 in standard definition will take approx. 750 Mbps of bandwidth. VoD, on the other hand, is a unicast per-viewer channel. 1000 standard definition VoD users will need appro. 3.75 Mbps.

The QoS requirements for video conferencing using H.323 ( SIP could be different again) can be planned on the "Rule of 75" as follows: Calculate the minimum bandwidth required b each of your application( e.g., video, voice, data). The total of this badnwidth is the minimum requirement for any given link and it should consume NO MORE than 75% of the total available bandwidth on the link. The 75% rule makes allowances for bandwidth required for over head traffic, such as routing, Layer 2 keepalives and other applications, such as, email, HTTP etc.

So, Capacity planning for H.323, should look like something as follows:

Video data + 20% = bandwidth required.

Example Video data rate: Bandwidth Required: 512 kbps = 614 kbps ; 1.5Mbps = 1.8 Mbps ...

For issues such as number of concurent users and more stuff on video conferencing you can perhaps consider looking into Cisco's solutions offered and also TANDBERG boxes.

Unified Computing and "Network is the Computer" ?

2009-02-10T13:11:00.014Z

Cisco's CTO, Ms. Padmasree Warrior wrote in her blog that “Cisco believes that the network can be a focal point for innovation, helping us enter new and adjacent markets if and when there is the right combination of value proposition and receptive audience.” Ms. Warrior also said “One point I will reiterate is that we see the need for open and consistent standards at many different layers in our developments—from management to protocols to data link definitions to physical layer and power/cooling standards. There is always a balance between innovation and standards, but I feel that in some areas, like Unified Computing, we can can achieve both.”

Personally, for whatever it is worth, I cannot agree more with Ms. Warrior. I am a Cisco fan, having worked extensively with Cisco’s technology for the last 9 odd years. I have reached a point where almost anything Cisco does or touches, I believe they will get the gold. A dissappointment in recent years has been their WAN acceleration areas and persistent CPU issues on some of their other series. But those are small fractions of Cisco’s core market focus. However, if they do go for stuff like data centre virtualisation and unified computing, then they will probably feel compelled to sort the WAFS/WAAS area out as well. May not be easy for Cisco to achieve all of the above with a well advertised hiring freeze on. Could be a delicate balancing issue. Good part on Cisco’s side is they probably have more time than “usual” due to less demand because of spending cuts at most of their customers.

I also believe that healthy competition in technical innovation is good for customers and future of technology. I also do not see any viable reason why people and some competitors of Cisco should receive this move of their’s as aggressively as some of them seem to have.

I tend to agree with all of our colleagues who believe that stuff like combination of propreitory and open source technologies, Cloud computing and network based computing can and will be part of a futuristic technological innovative process. Besides keeping in mind the issues of freedom and versatility that these tend to offer, the technical implementation, from a user’s point of view, so far, has been reasonably simple. An article from IBM about Amazon’s cloud computing services touches on the same.

What has been tedious for amateur technical enthusiasts like myself is the restrictions put on by propreitory licensing. I for exmaple, have tried for awhile to break into applied Quantum Cryptography across networks as I do believe that sooner or later the breakthrough has to come in Quantum Communications and the almost infinite possibilities that show up with it. The part where it may face a hitch is whether the reknowned vendors or Internet communication equipment makers (with the big money…) feel compelled to invest enough behind R&D of the same. The current limitation is the tarnsformation of the theory into efficient practice. However, implmentation of even a simple key exchange script has been challenging simply because I use Cisco and either my scripts don’t work or Cisco’s IOS coding is not compatible with mine. There is no way for me to know as I have no access to their IOS codes. Hence I feel trumped. The point being such restrictions put people without access to extensive R&D facilities at a loss. Of course since that is not a big loss for technology and business, it is unimportant.

Besides further development related to VoIP, VoD, IPv6 etc., I strongly believe that a far more secure internet is necessary. Currently, the financial world is already active in migrating to dedicated fibres due to security risk (SWIFT network). What we very definitely need in future is (almost) unbreakable security and total privacy. I believe what we need to seriously invest into and develop is the applied part of quantum information theory[1] and cryptography alongwith the related disciplines of steganography, traffic security and cryptosystems as applied towards discreet communication. In quantum computing, the laws of physics protect the information using the properties of quantum me- chanics. Open-air quantum key distribution with single photon source (SPS) has been demonstrated in experimental conditions[2][3][4]. In the area of Quantum Cryptography, in particular, it has been shown that there are intrinsic properties in Quantum Mechanics that will enable a Quantum Computer to produce results not possible with a classical computer[5][6][7]. In fututre we need to investigate the concept of development of Internet technologies based on the quantum principles[8] of cryptography, secret sharing and teleportation.

In particular, the possibility of quantum optics giving birth to a new generation of communication protocols over internet has to be seriously looked into and researched. When we do this we shall also need to address the complications arising from the atomic level structure of a quantum computing system such as: decoherence, entanglement, quantum teleportation[9], unitary transformations, and reversible universal gate structures.

Wave - Particle Duality in Classical Gravitation Theory

2008-05-02T11:20:00.011+01:00

Introduction

Trials of analysing a spherical light wave, which supposedly distorts as it interacts with a gravitational field is attempted with the assumption of a flat 4 dimensional space-time. Photons are produced as a result of annihilation of electron-positron pairs and are described by Bose-Einstein statistics. Huygens' wave theory principles are combined with the Newtonian corpuscular model of light as a stream of particles whose masses are subject to the laws of gravity. Efforts have been made to base the calculations on quantum statistical mechanics with a quantum mechanical expectation value for the Newtonian potential energy. A grand partition function has been used to describe the physical characteristics of the two resulting solutions:

closed form wave fronts similar to the Kepler orbits of Newtonian gravitational theory
open form "virtual" wave fronts similar to Coulomb repulsion in electromagnetic theory, e.g., Rutherford scattering of atomic nuclei.

These solutions correspond to the retarded and advanced potentials of electromagnetic theory.

A major focus of theoretical physics in the inter war years 1918 - 1939 was in establishing a bridge to unify the electromagnetic theories of Maxwell and Faraday with Einstein's theory of gravitation. An early attempt at this synthesis was the 5 dimensional geometry of Kaluza-Klein. Since then many theories of increasing complexity have been proposed, without much observational or experimental backing.

to be continued......

On Traffic Engineering and MPLS for Satellite Networks

2008-05-02T11:02:00.012+01:00

This discussion is split into two broad parts:

1) The first part addresses Traffic Engineering as an instrument for optimizing the operational performance of networks and related core problems, discuss solutions in both connectionless and signalled approach, and point to topics for future research and development. Techniques such as multi-path routing, traffic splitting, constraint-based routing (CBR), path-protection etc. that are used for traffic engineering in contemporary Internet Service Provider (ISP) networks are discussed for both connection oriented ( e.g. MPLS ) and connectionless classes ( e.g., distance-vector and link-state algorithms, routing metrics etc.).

2) The second part addresses traffic engineering aspects of MPLS for Satellite Networks. The large-area coverage at efficient infrastructure costs makes satellite networks attractive from a provider’s point of view. However, communication suffers in case of geostationary (GEO) satellites from high free space attenuation, latency and link budgeting criteria. In contrast, Low Earth Orbit (LEO) satellites with their lower latency and link budgets and less free space loss offers better promises for an high efficiency solution. Advantages of MPLS such as forwarding based on exact match of fixed length labels, integration of ATM and IP technologies, traffic engineering and QoS routing, conveniently separated routing and forwarding networks etc. suggests that it can implemented over satellite links to guarantee required QoS service levels. In the past Asynchronous Transfer Mode (ATM) have been considered for dynamic or fixed satellite network topologies for reliable and robust traffic engineering methods. Connectionless IP protocol demands implementation of IP Quality of Service (QoS) architecture [Integrated Service (IntServ) or Differentiated Service (DiffServ)] to provide the required QoS, but does not satisfy mechanisms for traffic engineering as compared ATM. Multiprotocol Label Switching (MPLS), on the other hand, allows adoption of new parameters for conventional IP traffic by decoupling packet forwarding from the information carried in the IP header. This section discusses proposals for IntServ, DiffServ, and MPLS based new QoS architectures for satellite based IP networks.

Note: Would having three Geostationary satellites, rule out the need for MEO Satellite/s to cover Polar surface data? It is a known fact that three Geostationary satellites are sufficient for covering entire earth surface, but do they cover the Polar surfaces too?

Answer: No they don't. Due to its high altitude (approx. 36000 km), one GEO spacecraft caters for approximately one- third of the earth surface. As such, 3 equally-spaced GEO satellites should provide full coverage of the earth BUT with the exception of the polar regions. The polar regions will not be covered in this case. GEO satellites are advantageous because of the few numbers of ground stations that are needed to handle their signals since they move at the same pace as the earth. On the other hand, their costs are high and GEO satellites have some limitations when applied to telephony: the long signal paths offer challenges in terms of signal propagation delay (about 260 ms of round-trip propagation time) which is significant. Also, due to power restrictions, it is not possible to provide a direct satellite connection for handheld mobile phones.

In contrast, the Middle-Earth Orbit (MEO) satellites are 5000 to 12000 km high and have round-trip delays of about 100 ms. For global coverage number of satellies required varies with altitude of the system. LEO/MEO satellites grouped into constellations move at a different pace than the earth and as such, it is necessary to provide a larger number of ground stations, but the number of satellites in their reach varies with time. For an example of diagrams and work on MEO satellite system and its effective data handling, the following paper by Dittberner et. al. is referred: http://www.eumetsat.int/Home/Main/Publications/Conference_and_Workshop_Proceedings/groups/cps/documents/document/pdf_conf_p48_s1_09_dittbern_v.pdf

[ material from above submitted to & accepted by MPLS 2008: http://www.isocore.com/mpls2008/program/technical_sessions.htm]

Quantum Cryptography and Secure Data Communication

2008-04-30T13:23:00.018+01:00

I strongly believe that a far more secure internet is necessary. Currently, the financial world is already active in migrating to dedicated fibres due to security risk (SWIFT network). What we very definitely need in future is (almost) unbreakable security and total privacy. I believe what we need to seriously invest into and develop is the applied part of quantum information theory[1] and cryptography alongwith the related disciplines of steganography, traffic security and cryptosystems as applied towards discreet communication. In quantum computing, the laws of physics protect the information using the properties of quantum me- chanics. Open-air quantum key distribution with single photon source (SPS) has been demonstrated in experimental conditions[2][3][4].

In the area of Quantum Cryptography, in particular, it has been shown that there are intrinsic properties in Quantum Mechanics that will enable a Quantum Computer to produce results not possible with a classical computer[5][6][7]. In fututre we need to investigate the concept of development of Internet technologies based on the quantum principles[8] of cryptography, secret sharing and teleportation. In particular, the possibility of quantum optics giving birth to a new generation of communication protocols over internet has to be seriously looked into and researched. When we do this we shall also need to address the complications arising from the atomic level structure of a quantum computing system.

[ material from above submitted to 9th Biennial IQSA Meeting on Quantum Structures.]

With thanks to Prof. David Wineland (NIST) and Dr. Barbara Terhal (IBM)

References:

[1] Shor, P. (2000), Quantum Information Theory: Results and Open Problems. Geom. Funct. Anal. (GAFA), Special Volume GAFA 2000, 816838.
[2] Allaume, R., Treussart, F., Messin, G., Dumeige, Y., Roch, J-F., Beveratos, A., Brouri-Tualle, R., Poizat, J-P., and Grangier, P. (2004), Experimental open-air quantum key distribution with a single-photon source. New Journal of Physics 6, 92.
[3] O'Brien, J. L. (2007), Optical Quantum Computing. Science 7 December, 318, no. 5856, 1567 - 1570.
[4] Kok, P., Munro, W. J., Nemoto, K., Ralph, T. C., Dowling, J. P. and Milburn, G. J. (2007), Linear optical quantum computing with photonic qubits. Reviews of Modern Physics, January 2007, 79, Issue 1, 135-174.
[5] Bennett, C. H., Brassard, G. and Ekert, A. K. (1992), Quantum cryptography. Scientific American, October 1992, 50-57.
[6] Shor, P.W. (1994), Algorithms for quantum computation: discrete logarithms and factoring. Proceedings 35th Annual Symposium on Foundations of Computer Science, 124-134.
[7] Bennett, C. H., Bessette, F., Brassard, G., Salvail, L. and Smolin, J. (1992), Experimental Quantum Cryptography. Journal of Cryptology, 5, no.1, 3-28.
[8] Slusher D. (2006), Lecture at ARDA. http://www.cleoconference.org/materials/slusher.pdf.
[9] Barrett, M. D., Chiaverini, J., Schaetz, T., Britton, J., Itano, W. M., Jost, J. D., Knill, E., Langer, C., Leibfried, D., Ozeri, R. and Wineland, D. J. (2004), Deterministic quantum teleportation of atomic qubits. Nature, 17 June, 429,737-739.
[10] Hanson, R., Kouwenhoven, L. P., Petta, J. R., Tarucha, S. and Vandersypen, L. M. K. (2007), Spins in few-electron quantum dots. Reviews of Modern Physics, October 2007 { 79, Issue 4, 1217-1265.
[11] Vazirani, U. (1994), Quotation from a newspaper article by Tom Siegfried, Science Editor of the Dallas Morning News.

Blog Start

2008-04-25T00:23:00.004+01:00

I hope to invite comments and exchange of ideas on Quantum Science & Relativity, saving wildlife, MPLS/BGP/Optical communication, Travels (in Africa, India, Middle East, Europe, US, South America & Australia) in general, Networking with Cisco & Juniper, visions on advent and feasibility of Quantum Computers, Cricket, World Peace & Politics, Literature, Einstein and Tagore.

This template is simple but nice. I find it easy to read. However, I shall endeavour to change it and enhance it somehow at some point in time in future. As soon as I get some time to do it.