text:
Network Working Group
Differentiated Services (Diffserv)-aware MPLS Traffic Engineering:
W. Lai
Bandwidth Constraints Models for
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
Copyright © The Internet Society (2005).
IESG Note
The content of this RFC has been considered by the IETF (specifically in the TE-WG working group, which has no problem with publication as an Informational RFC), and therefore it may resemble a current IETF work in progress or a published IETF work. However, this document is an individual submission and not a candidate for any level of Internet Standard. The IETF disclaims any knowledge of the fitness of this RFC for any purpose, and in particular notes that it has not had complete IETF review for such things as security, congestion control or inappropriate interaction with deployed protocols. The RFC Editor has chosen to publish this document at its discretion. Readers of this RFC should exercise caution in evaluating its value for implementation and deployment. See RFC 3932 for more information.
"Differentiated Services (Diffserv)-aware MPLS Traffic Engineering Requirements", RFC 3564, specifies the requirements and selection criteria for Bandwidth Constraints Models. Two such models, the Maximum Allocation and the Russian Dolls, are described therein. This document complements RFC 3564 by presenting the results of a performance evaluation of these two models under various operational conditions: normal load, overload, preemption fully or partially enabled, pure blocking, or complete sharing.
2. Bandwidth Constraints Models ....................................4
3. Performance Model ...............................................5
3.1. LSP Blocking and Preemption ................................6
3.2. Example Link Traffic Model .................................8
3.3. Performance under Normal Load ..............................9
4. Performance under Overload .....................................10
4.1. Bandwidth Sharing versus Isolation ........................10
4.2. Improving Class 2 Performance at the Expense of Class 3 ...12
4.3. Comparing Bandwidth Constraints of Different Models .......13
5. Performance under Partial Preemption ...........................15
5.1. Russian Dolls Model .......................................16
5.2. Maximum Allocation Model ..................................16
6. Performance under Pure Blocking ................................17
7. Performance under Complete Sharing .............................19
8. Implications on Performance Criteria ...........................20
9. Conclusions ....................................................21
12.1. Normative References ....................................22
12.2. Informative References ..................................22
Differentiated Services (Diffserv)-aware MPLS Traffic Engineering (DS-TE) mechanisms operate on the basis of different Diffserv classes of traffic to improve network performance. Requirements for DS-TE and the associated protocol extensions are specified in references [1] and [2] respectively.
To achieve per-class traffic engineering, rather than on an aggregate basis across all classes, DS-TE enforces different Bandwidth Constraints (BCs) on different classes. Reference [1] specifies the requirements and selection criteria for Bandwidth Constraints Models (BCMs) for the purpose of allocating bandwidth to individual classes.
This document presents a performance analysis for the two BCMs described in [1]:
(1) Maximum Allocation Model (MAM) - the maximum allowable bandwidth
usage of each class, together with the aggregate usage across all classes, are explicitly specified.
(2) Russian Dolls Model (RDM) - specification of maximum allowable
usage is done cumulatively by grouping successive priority classes recursively.
The following criteria are also listed in [1] for investigating the performance and trade-offs of different operational aspects of BCMs:
(1) addresses the scenarios in Section 2 of [1]
(2) works well under both normal and overload conditions
(3) applies equally when preemption is either enabled or disabled
(4) minimizes signaling load processing requirements
(5) maximizes efficient use of the network
(6) minimizes implementation and deployment complexity
The use of any given BCM has significant impacts on the capability of a network to provide protection for different classes of traffic, particularly under high load, so that performance objectives can be met [3]. This document complements [1] by presenting the results of a performance evaluation of the above two BCMs under various operational conditions: normal load, overload, preemption fully or partially enabled, pure blocking, or complete sharing. Thus, our focus is only on the performance-oriented criteria and their implications for a network implementation. In other words, we are only concerned with criteria (2), (3), and (5); we will not address criteria (1), (4), or (6).
Related documents in this area include [4], [5], [6], [7], and [8].
In the rest of this document, the following DS-TE acronyms are used:
BC    Bandwidth Constraint
BCM   Bandwidth Constraints Model
MAM   Maximum Allocation Model
RDM   Russian Dolls Model
There may be differences between the quality of service expressed and obtained with Diffserv without DS-TE and with DS-TE. Because DS-TE uses Constraint Based Routing, and because of the type of admission control capabilities it adds to Diffserv, DS-TE has capabilities for traffic that Diffserv does not. Diffserv does not indicate preemption, by intent, whereas DS-TE describes multiple levels of preemption for its Class-Types. Also, Diffserv does not support any means of explicitly controlling overbooking, while DS-TE allows this. When considering a complete quality of service environment, with Diffserv routers and DS-TE, it is important to consider these differences carefully.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.
2. Bandwidth Constraints Models
To simplify our presentation, we use the informal name "class of traffic" for the terms Class-Type and TE-Class, defined in [1]. We assume that (1) there are only three classes of traffic, and that (2) all label-switched paths (LSPs), regardless of class, require the same amount of bandwidth. Furthermore, the focus is on the bandwidth usage of an individual link with a given capacity; routing aspects of LSP setup are not considered.
The concept of reserved bandwidth is also defined in [1] to account for the possible use of overbooking. Rather than get into these details, we assume that each LSP is allocated 1 unit of bandwidth on a given link after establishment. This allows us to express link bandwidth usage simply in terms of the number of simultaneously established LSPs. Link capacity can then be used as the aggregate constraint on bandwidth usage across all classes.
Suppose that the three classes of traffic assumed above for the purposes of this document are denoted by class 1 (highest priority), class 2, and class 3 (lowest priority). When preemption is enabled, these are the preemption priorities. To define a generic class of BCMs for the purpose of our analysis in accordance with the above assumptions, let
Nmax = link capacity; i.e., the maximum number of simultaneously
established LSPs for all classes together
Nc = the number of simultaneously established class c LSPs,
for c = 1, 2, and 3, respectively.
For MAM, let
Bc = maximum number of simultaneously established class c LSPs.
Then, Bc is the Bandwidth Constraint for class c, and we have
Nc <= Bc <= Nmax, for c = 1, 2, and 3
N1 + N2 + N3 <= Nmax
B1 + B2 + B3 >= Nmax
For RDM, the BCs are specified as:
B1 = maximum number of simultaneously established class 1 LSPs
B2 = maximum number of simultaneously established LSPs for classes
and 2 together
1, 2, and 3 together
Then, we have the following relationships:
N1 <= B1
N1 + N2 <= B2
N1 + N2 + N3 <= B3
B1 < B2 < B3 = Nmax
3. Performance Model
Reference [8] presents a 3-class Markov-chain performance model to analyze a general class of BCMs. The BCMs that can be analyzed include, besides MAM and RDM, BCMs with privately reserved bandwidth that cannot be preempted by other classes.
The Markov-chain performance model in [8] assumes Poisson arrivals for LSP requests with exponentially distributed lifetime. The Poisson assumption for LSP requests is relevant since we are not dealing with the arrivals of individual packets within an LSP. Also, LSP lifetime may exhibit heavy-tail characteristics. This effect should be accounted for when the performance of a particular BCM by itself is evaluated. As the effect would be common for all BCMs, we ignore it for simplicity in the comparative analysis of the relative performance of different BCMs. In principle, a suitably chosen hyperexponential distribution may be used to capture some aspects of heavy tail. However, this will significantly increase the complexity of the non-product-form preemption model in [8].
The model in [8] assumes the use of admission control to allocate link bandwidth to LSPs of different classes in accordance with their respective BCs. Thus, the model accepts as input the link capacity and offered load from different classes. The blocking and preemption probabilities for different classes under different BCs are generated as output. Thus, from a service provider's perspective, given the desired level of blocking and preemption performance, the model can be used iteratively to determine the corresponding set of BCs.
To understand the implications of using criteria (2), (3), and (5) in the Introduction Section to select a BCM, we present some numerical results of the analysis in [8]. This is intended to facilitate discussion of the issues that can arise. The major performance objective is to achieve a balance between the need for bandwidth sharing (for increasing bandwidth efficiency) and the need for bandwidth isolation (for protecting bandwidth access by different classes).
3.1. LSP Blocking and Preemption
As described in Section 2, the three classes of traffic used as an example are class 1 (highest priority), class 2, and class 3 (lowest priority). Preemption may or may not be used, and we will examine the performance of each scenario. When preemption is used, the priorities are the preemption priorities. We consider cross-class preemption only, with no within-class preemption. In other words, preemption is enabled so that, when necessary, class 1 can preempt class 3 or class 2 (in that order), and class 2 can preempt class 3.
Each class offers a load of traffic to the network that is expressed in terms of the arrival rate of its LSP requests and the average lifetime of an LSP. A unit of such a load is an erlang. (In packet-based networks, traffic volume is usually measured by counting the number of bytes and/or packets that are sent or received over an interface during a measurement period. Here we are only concerned with bandwidth allocation and usage at the LSP level. Therefore, as a measure of resource utilization in a link-speed independent manner, the erlang is an appropriate unit for our purpose [9].)
To prevent Diffserv QoS degradation at the packet level, the expected number of established LSPs for a given class should be kept in line with the average service rate that the Diffserv scheduler can provide to that class. Because of the use of overbooking, the actual traffic carried by a link may be higher than expected, and hence QoS degradation may not be totally avoidable.
However, the use of admission control at the LSP level helps minimize QoS degradation by enforcing the BCs established for the different classes, according to the rules of the BCM adopted. That is, the BCs are used to determine the number of LSPs that can be simultaneously established for different classes under various operational conditions. By controlling the number of LSPs admitted from different classes, this in turn ensures that the amount of traffic submitted to the Diffserv scheduler is compatible with the targeted packet-level QoS objectives.
The performance of a BCM can therefore be measured by how well the given BCM handles the offered traffic, under normal or overload conditions, while maintaining packet-level service objectives. Thus, assuming that the enforcement of Diffserv QoS objectives by admission control is a given, the performance of a BCM can be expressed in terms of LSP blocking and preemption probabilities.
Different BCMs have different strengths and weaknesses. Depending on the BCs chosen for a given load, a BCM may perform well in one operating region and poorly in another. Service providers are mainly concerned with the utility of a BCM to meet their operational needs. Regardless of which BCM is deployed, the foremost consideration is that the BCM works well under the engineered load, such as the ability to deliver service-level objectives for LSP blocking probabilities. It is also expected that the BCM handles overload "reasonably" well. Thus, for comparison, the common operating point we choose for BCMs is that they meet specified performance objectives in terms of blocking/preemption under given normal load. We then observe how their performance varies under overload. More will be said about this aspect later in Section 4.2.
3.2. Example Link Traffic Model
For example, consider a link with a capacity that allows a maximum of 15 LSPs from different classes to be established simultaneously. All LSPs are assumed to have an average lifetime of 1 time unit. Suppose that this link is being offered a load of
2.7 erlangs from class 1,
3.5 erlangs from class 2, and
3.5 erlangs from class 3.
We now consider a scenario wherein the blocking/preemption performance objectives for the three classes are desired to be comparable under normal conditions (other scenarios are covered in later sections). To meet this service requirement under the above given load, the BCs are selected as follows:
For MAM:
up to 6 simultaneous LSPs for class 1,
up to 7 simultaneous LSPs for class 2, and
up to 15 simultaneous LSPs for class 3.
For RDM:
up to 6 simultaneous LSPs for class 1 by itself,
up to 11 simultaneous LSPs for classes 1 and 2 together, and up to 15 simultaneous LSPs for all three classes together.
Note that the driver is service requirement, independent of BCM. The above BCs are not picked arbitrarily; they are chosen to meet specific performance objectives in terms of blocking/preemption (detailed in the next section).
An intuitive "explanation" for the above set of BCs may be as follows. Class 1 BC is the same (6) for both models, as class 1 is treated the same way under either model with preemption. However, MAM and RDM operate in fundamentally different ways and give different treatments to classes with lower preemption priorities. It can be seen from Section 2 that although RDM imposes a strict ordering of the different BCs (B1 < B2 < B3) and a hard boundary (B3 = Nmax), MAM uses a soft boundary (B1+B2+B3 >= Nmax) with no specific ordering. As will be explained in Section 4.3, this allows RDM to have a higher degree of sharing among different classes. Such a higher degree of coupling means that the numerical values of the BCs can be relatively smaller than those for MAM, to meet given performance requirements under normal load.
Thus, in the above example, the RDM BCs of (6, 11, 15) may be thought of as roughly corresponding to the MAM BCs of (6, 6+7, 6+7+15). (The intent here is just to point out that the design parameters for the two BCMs need to be different, as they operate differently; strictly speaking, the numerical correspondence is incorrect.) Of course, both BCMs are bounded by the same aggregate constraint of the link capacity (15).
The BCs chosen in the above example are not intended to be regarded as typical values used by any service provider. They are used here mainly for illustrative purposes. The method we used for analysis can easily accommodate another set of parameter values as input.
3.3. Performance under Normal Load
In the example above, based on the BCs chosen, the blocking and preemption probabilities for LSP setup requests under normal conditions for the two BCMs are given in Table 1. Remember that the BCs have been selected for this scenario to address the service requirement to offer comparable blocking/preemption objectives for the three classes.
Table 1. Blocking and preemption probabilities
BCM     PB1      PB2      PB3      PP2      PP3    PB2+PP2  PB3+PP3
MAM   0.03692  0.03961  0.02384     0     0.02275  0.03961  0.04659
RDM   0.03692  0.02296  0.02402  0.01578  0.01611  0.03874  0.04013
In the above table, the following apply:
PB1 = blocking probability of class 1
PP2 = preemption probability of class 2
PB2+PP2 = combined blocking/preemption probability of class 2 PB3+PP3 = combined blocking/preemption probability of class 3
First, we observe that, indeed, the values for (PB1, PB2+PP2, PB3+PP3) are very similar one to another. This confirms that the service requirement (of comparable blocking/preemption objectives for the three classes) has been met for both BCMs.
Then, we observe that the (PB1, PB2+PP2, PB3+PP3) values for MAM are very similar to the (PB1, PB2+PP2, PB3+PP3) values for RDM. This indicates that, in this scenario, both BCMs offer very similar performance under normal load.
From column 2 of Table 1, it can be seen that class 1 sees exactly the same blocking under both BCMs. This should be obvious since both allocate up to 6 simultaneous LSPs for use by class 1 only. Slightly better results are obtained from RDM, as shown by the last two columns in Table 1. This comes about because the cascaded bandwidth separation in RDM effectively gives class 3 some form of protection from being preempted by higher-priority classes.
Also, note that PP2 is zero in this particular case, simply because the BCs for MAM happen to have been chosen in such a way that class 1 never has to preempt class 2 for any of the bandwidth that class 1 needs. (This is because class 1 can, in the worst case, get all the bandwidth it needs simply by preempting class 3 alone.) In general, this will not be the case.
It is interesting to compare these results with those for the case of a single class. Based on the Erlang loss formula, a capacity of 15 servers can support an offered load of 10 erlangs with a blocking probability of 0.0364969. Whereas the total load for the 3-class BCM is less with 2.7 + 3.5 + 3.5 = 9.7 erlangs, the probabilities of blocking/preemption are higher. Thus, there is some loss of efficiency due to the link bandwidth being partitioned to accommodate for different traffic classes, thereby resulting in less sharing. This aspect will be examined in more detail later, in Section 7 on Complete Sharing.
4. Performance under Overload
Overload occurs when the traffic on a system is greater than the traffic capacity of the system. To investigate the performance under overload conditions, the load of each class is varied separately. Blocking and preemption probabilities are not shown separately for each case; they are added together to yield a combined blocking/preemption probability.
4.1. Bandwidth Sharing versus Isolation
Figures 1 and 2 show the relative performance when the load of each class in the example of Section 3.2 is varied separately. The three series of data in each of these figures are, respectively, class 1 blocking probability ("Class 1 B"),
class 2 blocking/preemption probability ("Class 2 B+P"), and class 3 blocking/preemption probability ("Class 3 B+P").
For each of these series, the first set of four points is for the performance when class 1 load is increased from half of its normal load to twice its normal. Similarly, the next and the last sets of four points are when class 2 and class 3 loads are increased correspondingly.
The following observations apply to both BCMs:
The performance of any class generally degrades as its load increases.
The performance of class 1 is not affected by any changes (increases or decreases) in either class 2 or class 3 traffic, because class 1 can always preempt others.
Similarly, the performance of class 2 is not affected by any changes in class 3 traffic.
Class 3 sees better (worse) than normal performance when either class 1 or class 2 traffic is below (above) normal.
In contrast, the impact of the changes in class 1 traffic on class 2 performance is different for the two BCMs: It is negligible in MAM and significant in RDM.
Although class 2 sees little improvement (no improvement in this particular example) in performance when class 1 traffic is below normal when MAM is used, it sees better than normal performance under RDM.
Class 2 sees no degradation in performance when class 1 traffic is above normal when MAM is used. In this example, with BCs 6 + 7 < 15, class 1 and class 2 traffic is effectively being served by separate pools. Therefore, class 2 sees no preemption, and only class 3 is being preempted whenever necessary. This fact is confirmed by the Erlang loss formula: a load of 2.7 erlangs offered to 6 servers sees a 0.03692 blocking, and a load of 3.5 erlangs offered to 7 servers sees a 0.03961 blocking. These blocking probabilities are exactly the same as the corresponding entries in Table 1: PB1 and PB2 for MAM.
This is not the case in RDM. Here, the probability for class 2 to be preempted by class 1 is nonzero because of two effects. (1) Through the cascaded bandwidth arrangement, class 3 is protected somewhat from preemption. (2) Class 2 traffic is sharing a BC with class 1. Consequently, class 2 suffers when class 1 traffic increases.
Thus, it appears that although the cascaded bandwidth arrangement and the resulting bandwidth sharing makes RDM work better under normal conditions, such interaction makes it less effective to provide class isolation under overload conditions.
4.2. Improving Class 2 Performance at the Expense of Class 3
We now consider a scenario in which the service requirement is to give better blocking/preemption performance to class 2 than to class 3, while maintaining class 1 performance at the same level as in the previous scenario. (The use of minimum deterministic guarantee for class 3 is to be considered in the next section.) So that the specified class 2 performance objective can be met, class 2 BC is increased appropriately. As an example, BCs (6, 9, 15) are now used for MAM, and (6, 13, 15) for RDM. For both BCMs, as shown in Figures 1bis and 2bis, although class 1 performance remains unchanged, class 2 now receives better performance, at the expense of class 3. This is of course due to the increased access of bandwidth by class 2 over class 3. Under normal conditions, the performance of the two BCMs is similar in terms of their blocking and preemption probabilities for LSP setup requests, as shown in Table 2.
BCM      PB1      PB2      PB3      PP2      PP3    PB2+PP2  PB3+PP3
MAM    0.03692  0.00658  0.02733     0     0.02709  0.00658  0.05441
RDM    0.03692  0.00449  0.02759  0.00272  0.02436  0.00721  0.05195
Under overload, the observations in Section 4.1 regarding the difference in the general behavior between the two BCMs still apply, as shown in Figures 1bis and 2bis.
The following are two frequently asked questions about the operation of BCMs.
(1) For a link capacity of 15, would a class 1 BC of 6 and a class 2
BC of 9 in MAM result in the possibility of a total lockout for
class 3?
This will certainly be the case when there are 6 class 1 and 9 class 2 LSPs being established simultaneously. Such an offered load (with 6 class 1 and 9 class 2 LSP requests) will not cause a lockout of class 3 with RDM having a BC of 13 for classes 1 and 2 combined, but will result in class 2 LSPs being rejected. If class 2 traffic were considered relatively more important than class 3 traffic, then RDM would perform very poorly compared to MAM with BCs of (6, 9, 15).
(2) Should MAM with BCs of (6, 7, 15) be used instead so as to make
the performance of RDM look comparable?
The answer is that the above scenario is not very realistic when the offered load is assumed to be (2.7, 3.5, 3.5) for the three classes, as stated in Section 3.2. Treating an overload of (6, 9, x) as a normal operating condition is incompatible with the engineering of BCs according to needed bandwidth from different classes. It would be rare for a given class to need so much more than its engineered bandwidth level. But if the class did, the expectation based on design and normal traffic fluctuations is that this class would quickly release unneeded bandwidth toward its engineered level, freeing up bandwidth for other classes.
Service providers engineer their networks based on traffic projections to determine network configurations and needed capacity. All BCMs should be designed to operate under realistic network conditions. For any BCM to work properly, the selection of values for different BCs must therefore be based on the projected bandwidth needs of each class, as well as on the bandwidth allocation rules of the BCM itself. This is to ensure that the BCM works as expected under the intended design conditions. In operation, the actual load may well turn out to be different from that of the design. Thus, an assessment of the performance of a BCM under overload is essential to see how well the BCM can cope with traffic surges or network failures. Reflecting this view, the basis for comparison of two BCMs is that they meet the same or similar performance requirements under normal conditions, and how they withstand overload.
In operational practice, load measurement and forecast would be useful to calibrate and fine-tune the BCs so that traffic from different classes could be redistributed accordingly. Dynamic adjustment of the Diffserv scheduler could also be used to minimize QoS degradation.
4.3. Comparing Bandwidth Constraints of Different Models
As is pointed out in Section 3.2, the higher degree of sharing among the different classes in RDM means that the numerical values of the BCs could be relatively smaller than those for MAM. We now examine this aspect in more detail by considering the following scenario. We set the BCs so that (1) for both BCMs, the same value is used for class 1, (2) the same minimum deterministic guarantee of bandwidth for class 3 is offered by both BCMs, and (3) the blocking/preemption probability is minimized for class 2. We want to emphasize that this may not be the way service providers select BCs. It is done here to investigate the statistical behavior of such a deterministic mechanism.
For illustration, we use BCs (6, 7, 15) for MAM, and (6, 13, 15) for RDM. In this case, both BCMs have 13 units of bandwidth for classes 1 and 2 together, and dedicate 2 units of bandwidth for use by class 3 only. The performance of the two BCMs under normal conditions is shown in Table 3. It is clear that MAM with (6, 7, 15) gives fairly comparable performance objectives across the three classes, whereas RDM with (6, 13, 15) strongly favors class 2 at the expense of class 3. They therefore cater to different service requirements.
By comparing Figures 1 and 2bis, it can be seen that, when being subjected to the same set of BCs, RDM gives class 2 much better performance than MAM, with class 3 being only slightly worse.
This confirms the observation in Section 3.2 that, when the same service requirements under normal conditions are to be met, the numerical values of the BCs for RDM can be relatively smaller than those for MAM. This should not be surprising in view of the hard boundary (B3 = Nmax) in RDM versus the soft boundary (B1+B2+B3 >= Nmax) in MAM. The strict ordering of BCs (B1 < B2 < B3) gives RDM the advantage of a higher degree of sharing among the different classes; i.e., the ability to reallocate the unused bandwidth of higher-priority classes to lower-priority ones, if needed. Consequently, this leads to better performance when an identical set of BCs is used as exemplified above. Such a higher degree of sharing may necessitate the use of minimum deterministic bandwidth guarantee to offer some protection for lower-priority traffic from preemption. The explicit lack of ordering of BCs in MAM and its soft boundary imply that the use of minimum deterministic guarantees for lower- priority classes may not need to be enforced when there is a lesser degree of sharing. This is demonstrated by the example in Section 4.2 with BCs (6, 9, 15) for MAM.
For illustration, Table 4 shows the performance under normal conditions of RDM with BCs (6, 15, 15).
Regardless of whether deterministic guarantees are used, both BCMs are bounded by the same aggregate constraint of the link capacity. Also, in both BCMs, bandwidth access guarantees are necessarily achieved statistically because of traffic fluctuations, as explained in Section 4.2. (As a result, service-level objectives are typically specified as monthly averages, under the use of statistical guarantees rather than deterministic guarantees.) Thus, given the fundamentally different operating principles of the two BCMs (ordering, hard versus soft boundary), the dimensions of one BCM should not be adopted to design for the other. Rather, it is the service requirements, and perhaps also the operational needs, of a service provider that should be used to drive how the BCs of a BCM are selected.
5. Performance under Partial Preemption
In the previous two sections, preemption is fully enabled in the sense that class 1 can preempt class 3 or class 2 (in that order), and class 2 can preempt class 3. That is, both classes 1 and 2 are preemptor-enabled, whereas classes 2 and 3 are preemptable. A class that is preemptor-enabled can preempt lower-priority classes designated as preemptable. A class not designated as preemptable cannot be preempted by any other classes, regardless of relative priorities.
We now consider the three cases shown in Table 5, in which preemption is only partially enabled.
Table 5. Partial preemption modes
preemption modes         preemptor-enabled     preemptable
"1+2 on 3" (Fig. 3, 6)   class 1, class 2        class 3
"1 on 3"   (Fig. 4, 7)       class 1             class 3
"1 on 2+3" (Fig. 5, 8)       class 1         class 3, class 2
In this section, we evaluate how these preemption modes affect the performance of a particular BCM. Thus, we are comparing how a given BCM performs when preemption is fully enabled versus how the same BCM performs when preemption is partially enabled. The performance of these preemption modes is shown in Figures 3 to 5 for RDM, and in Figures 6 through 8 for MAM, respectively. In all of these figures, the BCs of Section 3.2 are used for illustration; i.e., (6, 7, 15) for MAM and (6, 11, 15) for RDM. However, the general behavior is similar when the BCs are changed to those in Sections 4.2 and 4.3; i.e., (6, 9, 15) and (6, 13, 15), respectively.
5.1. Russian Dolls Model
Let us first examine the performance under RDM. There are two sets of results, depending on whether class 2 is preemptable: (1) Figures 3 and 4 for the two modes when only class 3 is preemptable, and (2) Figure 2 in the previous section and Figure 5 for the two modes when both classes 2 and 3 are preemptable. By comparing these two sets of results, the following impacts can be observed. Specifically, when class 2 is non-preemptable, the behavior of each class is as follows:
Class 1 generally sees a higher blocking probability. As the class 1 space allocated by the class 1 BC is shared with class 2, which is now non-preemptable, class 1 cannot reclaim any such space occupied by class 2 when needed. Also, class 1 has less opportunity to preempt, as it is able to preempt class 3 only.
Class 3 also sees higher blocking/preemption when its own load is increased, as it is being preempted more frequently by class 1, when class 1 cannot preempt class 2. (See the last set of four points in the series for class 3 shown in Figures 3 and 4, when comparing with Figures 2 and 5.)
Class 2 blocking/preemption is reduced even when its own load is increased, since it is not being preempted by class 1. (See the middle set of four points in the series for class 2 shown in Figures 3 and 4, when comparing with Figures 2 and 5.)
Another two sets of results are related to whether class 2 is preemptor-enabled. In this case, when class 2 is not preemptor- enabled, class 2 blocking/preemption is increased when class 3 load is increased. (See the last set of four points in the series for class 2 shown in Figures 4 and 5, when comparing with Figures 2 and 3.) This is because both classes 2 and 3 are now competing independently with each other for resources.
5.2. Maximum Allocation Model
Turning now to MAM, the significant impact appears to be only on class 2, when it cannot preempt class 3, thereby causing its blocking/preemption to increase in two situations.
When class 1 load is increased. (See the first set of four points in the series for class 2 shown in Figures 7 and 8, when comparing with Figures 1 and 6.)
When class 3 load is increased. (See the last set of four points in the series for class 2 shown in Figures 7 and 8, when comparing with Figures 1 and 6.) This is similar to RDM; i.e., class 2 and class 3 are now competing with each other.
When Figure 1 (for the case of fully enabled preemption) is compared to Figures 6 through 8 (for partially enabled preemption), it can be seen that the performance of MAM is relatively insensitive to the different preemption modes. This is because when each class has its own bandwidth access limits, the degree of interference among the different classes is reduced.
This is in contrast with RDM, whose behavior is more dependent on the preemption mode in use.
6. Performance under Pure Blocking
This section covers the case in which preemption is completely disabled. We continue with the numerical example used in the previous sections, with the same link capacity and offered load.
For RDM, we consider two different settings:
"Russian Dolls (1)" BCs:
Note that the "Russian Dolls (1)" set of BCs is the same as previously with preemption enabled, whereas the "Russian Dolls (2)" has the cascade of bandwidth arranged in reverse order of the classes.
As observed in Section 4, the cascaded bandwidth arrangement is intended to offer lower-priority traffic some protection from preemption by higher-priority traffic. This is to avoid starvation. In a pure blocking environment, such protection is no longer necessary. As depicted in Figure 9, it actually produces the opposite, undesirable effect: higher-priority traffic sees higher blocking than lower-priority traffic. With no preemption, higher- priority traffic should be protected instead to ensure that it could get through when under high load. Indeed, when the reverse cascade is used in "Russian Dolls (2)", the required performance of lower blocking for higher-priority traffic is achieved, as shown in Figure 10. In this specific example, there is very little difference among the performance of the three classes in the first eight data points for each of the three series. However, the BCs can be tuned to get a bigger differentiation.
For MAM, we also consider two different settings:
"Exp. Max. Alloc. (1)" BCs:
up to 8 simultaneous LSPs for class 3.
up to 7 simultaneous LSPs for class 1, with additional bandwidth for
1 LSP privately reserved
These BCs are chosen so that, under normal conditions, the blocking performance is similar to all the previous scenarios. The only difference between these two sets of values is that the "Exp. Max. Alloc. (2)" algorithm gives class 1 a private pool of 1 server for class protection. As a result, class 1 has a relatively lower blocking especially when its traffic is above normal, as can be seen by comparing Figures 11 and 12. This comes, of course, with a slight increase in the blocking of classes 2 and 3 traffic.
When comparing the "Russian Dolls (2)" in Figure 10 with MAM in Figures 11 or 12, the difference between their behavior and the associated explanation are again similar to the case when preemption is used. The higher degree of sharing in the cascaded bandwidth arrangement of RDM leads to a tighter coupling between the different classes of traffic when under overload. Their performance therefore tends to degrade together when the load of any one class is increased. By imposing explicit maximum bandwidth usage on each class individually, better class isolation is achieved. The trade- off is that, generally, blocking performance in MAM is somewhat higher than in RDM, because of reduced sharing.
The difference in the behavior of RDM with or without preemption has already been discussed at the beginning of this section. For MAM, some notable differences can also be observed from a comparison of Figures 1 and 11. If preemption is used, higher-priority traffic tends to be able to maintain its performance despite the overloading of other classes. This is not so if preemption is not allowed. The trade-off is that, generally, the overloaded class sees a relatively higher blocking/preemption when preemption is enabled than there would be if preemption is disabled.
7. Performance under Complete Sharing
As observed towards the end of Section 3, the partitioning of bandwidth capacity for access by different traffic classes tends to reduce the maximum link efficiency achievable. We now consider the case where there is no such partitioning, thereby resulting in full sharing of the total bandwidth among all the classes. This is referred to as the Complete Sharing Model.
For MAM, this means that the BCs are such that up to 15 simultaneous LSPs are allowed for any class.
Similarly, for RDM, the BCs are
up to 15 simultaneous LSPs for class 1 by itself,
Effectively, there is now no distinction between MAM and RDM. Figure 13 shows the performance when all classes have equal access to link bandwidth under Complete Sharing.
With preemption being fully enabled, class 1 sees virtually no blocking, regardless of the loading conditions of the link. Since class 2 can only preempt class 3, class 2 sees some blocking and/or preemption when either class 1 load or its own load is above normal; otherwise, class 2 is unaffected by increases of class 3 load. As higher priority classes always preempt class 3 when the link is full, class 3 suffers the most, with high blocking/preemption when there is any load increase from any class. A comparison of Figures 1, 2, and 13 shows that, although the performance of both classes 1 and 2 is far superior under Complete Sharing, class 3 performance is much better off under either MAM or RDM. In a sense, class 3 is starved under overload as no protection of its traffic is being provided under Complete Sharing.
8. Implications on Performance Criteria
Based on the previous results, a general theme is shown to be the trade-off between bandwidth sharing and class protection/isolation. To show this more concretely, let us compare the different BCMs in terms of the overall loss probability. This quantity is defined as the long-term proportion of LSP requests from all classes combined that are lost as a result of either blocking or preemption, for a given level of offered load.
As noted in the previous sections, although RDM has a higher degree of sharing than MAM, both ultimately converge to the Complete Sharing Model as the degree of sharing in each of them is increased. Figure 14 shows that, for a single link, the overall loss probability is the smallest under Complete Sharing and the largest under MAM, with that under RDM being intermediate. Expressed differently, Complete Sharing yields the highest link efficiency and MAM the lowest. As a matter of fact, the overall loss probability of Complete Sharing is identical to the loss probability of a single class as computed by the Erlang loss formula. Yet Complete Sharing has the poorest class protection capability. (Note that, in a network with many links and multiple-link routing paths, analysis in [6] showed that Complete Sharing does not necessarily lead to maximum network-wide bandwidth efficiency.)
Increasing the degree of bandwidth sharing among the different traffic classes helps increase link efficiency. Such increase, however, will lead to a tighter coupling between different classes. Under normal loading conditions, proper dimensioning of the link so that there is adequate capacity for each class can minimize the effect of such coupling. Under overload conditions, when there is a scarcity of capacity, such coupling will be unavoidable and can cause severe degradation of service to the lower-priority classes. Thus, the objective of maximizing link usage as stated in criterion (5) of Section 1 must be exercised with care, with due consideration to the effect of interactions among the different classes. Otherwise, use of this criterion alone will lead to the selection of the Complete Sharing Model, as shown in Figure 14.
The intention of criterion (2) in judging the effectiveness of different BCMs is to evaluate how they help the network achieve the expected performance. This can be expressed in terms of the blocking and/or preemption behavior as seen by different classes under various loading conditions. For example, the relative strength of a BCM can be demonstrated by examining how many times the per-class blocking or preemption probability under overload is worse than the corresponding probability under normal load.
BCMs are used in DS-TE for path computation and admission control of LSPs by enforcing different BCs for different classes of traffic so that Diffserv QoS performance can be maximized. Therefore, it is of interest to measure the performance of a BCM by the LSP blocking/preemption probabilities under various operational conditions. Based on this, the performance of RDM and MAM for LSP establishment has been analyzed and compared. In particular, three different scenarios have been examined: (1) all three classes have comparable performance objectives in terms of LSP blocking/preemption under normal conditions, (2) class 2 is given better performance at the expense of class 3, and (3) class 3 receives some minimum deterministic guarantee.
A general theme is the trade-off between bandwidth sharing to achieve greater efficiency under normal conditions, and to achieve robust class protection/isolation under overload. The general properties of the two BCMs are as follows:
allows greater sharing of bandwidth among different classes
performs somewhat better under normal conditions
works well when preemption is fully enabled; under partial preemption, not all preemption modes work equally well
does not depend on the use of preemption
is relatively insensitive to the different preemption modes when preemption is used
provides more robust class isolation under overload
Generally, the use of preemption gives higher-priority traffic some degree of immunity to the overloading of other classes. This results in a higher blocking/preemption for the overloaded class than that in a pure blocking environment.
This document does not introduce additional security threats beyond those described for Diffserv [10] and MPLS Traffic Engineering [11, 12, 13, 14], and the same security measures and procedures described in those documents apply here. For example, the approach for defense against theft- and denial-of-service attacks discussed in [10], which consists of the combination of traffic conditioning at Diffserv boundary nodes along with security and integrity of the network infrastructure within a Diffserv domain, may be followed when DS-TE is in use.
Also, as stated in [11], it is specifically important that manipulation of administratively configurable parameters (such as those related to DS-TE LSPs) be executed in a secure manner by authorized entities. For example, as preemption is an administratively configurable parameter, it is critical that its values be set properly throughout the network. Any misconfiguration in any label switch may cause new LSP setup requests either to be blocked or to unnecessarily preempt LSPs already established. Similarly, the preemption values of LSP setup requests must be configured properly; otherwise, they may affect the operation of existing LSPs.
Inputs from Jerry Ash, Jim Boyle, Anna Charny, Sanjaya Choudhury, Dimitry Haskin, Francois Le Faucheur, Vishal Sharma, and Jing Shen are much appreciated.
[1]  Le Faucheur, F. and W. Lai, "Requirements for Support of
Differentiated Services-aware MPLS Traffic Engineering", RFC
3564, July 2003.
[2]  Le Faucheur, F., Ed., "Protocol Extensions for Support of
Diffserv-aware MPLS Traffic Engineering", RFC 4124, June 2005.
[3]  Boyle, J., Gill, V., Hannan, A., Cooper, D., Awduche, D.,
Christian, B., and W. Lai, "Applicability Statement for Traffic
Engineering with MPLS", RFC 3346, August 2002.
[4]  Le Faucheur, F. and W. Lai, "Maximum Allocation Bandwidth
Constraints Model for Diffserv-aware MPLS Traffic Engineering",
[5]  Le Faucheur, F., Ed., "Russian Dolls Bandwidth Constraints Model
for Diffserv-aware MPLS Traffic Engineering", RFC 4127, June
[6]  Ash, J., "Max Allocation with Reservation Bandwidth Constraint
Model for MPLS/DiffServ TE & Performance Comparisons", RFC 4126,
[7]  F. Le Faucheur, "Considerations on Bandwidth Constraints Models
for DS-TE", Work in Progress.
[8]  W.S. Lai, "Traffic Engineering for MPLS," Internet Performance
and Control of Network Systems III Conference, SPIE Proceedings
Vol. 4865, Boston, Massachusetts, USA, 30-31 July 2002, pp.
[9]  W.S. Lai, "Traffic Measurement for Dimensioning and Control of
IP Networks," Internet Performance and Control of Network
Systems II Conference, SPIE Proceedings Vol. 4523, Denver,
Colorado, USA, 21-22 August 2001, pp. 359-367.
[10] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W.
Weiss, "An Architecture for Differentiated Service", RFC 2475, December 1998.
[11] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J.
McManus, "Requirements for Traffic Engineering Over MPLS", RFC 2702, September 1999.
[12] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G.
Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001.
[13] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE)
Extensions to OSPF Version 2", RFC 3630, September 2003.
[14] Smit, H. and T. Li, "Intermediate System to Intermediate System
(IS-IS) Extensions for Traffic Engineering (TE)", RFC 3784, June
Wai Sum Lai
Room D5-3D18
200 Laurel Avenue
EMail: wlai@att.com
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text:
The University of Rochester (UR) is a private, nonsectarian, coeducational, research university located in Rochester, New York. The university grants undergraduate, graduate, doctoral, and professional degrees. The university is home to several noted schools and programs, including the number one ranked Eastman School of Music, and The Institute of Optics, the oldest optics program in the U.S. The university enrolls approximately 4,600 undergraduates and 3,900 graduate students. University of Rochester competes in the NCAA's Division III for athletics. UR is a highly research oriented institution, hosting numerous centers of research, and boasts the most powerful ultraviolet laser in the world. UR with its affiliated Strong Health System, is the largest employer in the Greater Rochester area.
The University of Rochester was founded in 1850 as a Baptist-sponsored institution. The impetus to form the university came primarily from the little town of Hamilton, New York, which has been home to Colgate University since 1819. In 1848, the Baptist Education Society planned to move Colgate University (Then known as Madison University) to the city of Rochester, but was halted by legal action. Dissenting Colgate trustees, faculty, and students founded the University of Rochester, receiving a charter from the Regents of the University of the State of New York on January 31, 1850. Classes began that November, with approximately 60 students enrolling, including 28 transfers from Madison.
University of Rochester's campus was originally in downtown Rochester at the United States Hotel, which was located on Buffalo Street near Elizabeth Street, which today is West Main Street near the I-490 overpass. In 1853, the campus moved east to a then-suburban location on what is now University Avenue. Local businessman and Congressman Azariah Boody donated 8 acres of land for the new campus, and the University purchased a further 17 acres from him.
The first women students were admitted in 1900, the result of an effort led by Susan B. Anthony and Helen Barrett Montgomery. During the 1890s, a number of women took classes and labs at the university as "visitors" but were not officially enrolled nor were their records included in the college register. President David Jayne Hill allowed the first woman, Helen E. Wilkinson, to enroll as a normal student, although she was not allowed to matriculate or to pursue a degree. Thirty-three women enrolled among the first class in 1900, and Ella S. Wilcoxen was the first to receive a degree, in 1901.
Major growth occurred under the leadership of Rush Rhees, during his 1900-1935 tenure. During this time, George Eastman became a major donor, giving more than $50 million to the university. The first Ph.D. was awarded in 1925. In 1955, the separate colleges for men and women were merged into The College. In 1958, three new schools were created in engineering, business administration, and education.
In 1995, university president Thomas H. Jackson announced the launch of a "Renaissance Plan" for The College that, among several changes, reduced enrollment and created a more selective admissions process. The plan also revised the undergraduate curriculum significantly, creating the current system with only one required course and only a few distribution requirements(known as "clusters").
Arts, Sciences, and Engineering
William E. Simon Graduate School of Business Administration Margaret Warner Graduate School of Education and Human Development
Medical, Research, and Cultural Components
Strong Health
Laboratory for Laser Energetics
Memorial Art Gallery
University of Rochester Press
Center for Optics Manufacturing
Susan B. Anthony Center for Women's Leadership
C. E. K. Mees Observatory (Bristol Hills)
University of Rochester's undergraduate enrollment consists of about 4,500 full-time and about 100 part-time students from across the U.S. and over 90 countries.Graduate enrollment comprises about 3,300 full-time and about 550 part-time graduate students. The university has more than 97,000 living alumni. The university employs more than 1,200 tenure-track faculty, with more than 17,000 faculty and staff across the university and the Strong Health System. UR's faculty include fellows of all four National Academies of the U.S., Guggenheim Fellows, and recipients of many other awards and recognitions.
The defining feature of the undergraduate program at the University is the Rochester Curriculum. There are no required subjects outside of a prerequisite writing course, which may be tested out of. The Curriculum requires that undergraduates study in all of three areas of knowledge: humanities, social sciences, and natural sciences. Aside from the area of study which a student's major falls in, undergraduates must complete 3-4 courses of related materials (called "clusters") within each of the remaining areas. For example, a student with a concentration in mathematics, a natural science field, must complete at least one cluster in the humanities and one in social sciences. A second concentration or a minor also satisfies this requirement. The only exceptions are students concentrating in an accredited engineering field (biomedical engineering, chemical engineering, electrical and computer engineering or mechanical engineering), who are only required to have one cluster in either humanities or social sciences.
Recent Rankings
Kaplan's 2008 "How to Get Into College" guide lists the Eastman School of Music as the Hottest Music School
Kaplan's 2007 guide includes the University of Rochester as one of 25 "New Ivies."
US News and World Report 2008
National universities: 35th
Best graduate schools—School of Engineering and Applied Sciences: 30th
Best graduate schools—political science: 13th
Best graduate schools—economics: 19th
Center for College Affordability and Productivity 2008
(ranks colleges based on student outcomes)
Times of London 2007
World universities: 21st
Washington Monthly 2007
(ranks colleges by what they give back to the country)
The University of Rochester ranked 95th in the 2007 THES-QS World University Ranking
The University of Rochester ranked 119th in the 2008 THES-QS World University Ranking
The University of Rochester ranked 141st in the 2009 THES-QS World University Ranking
The University of Rochester ranked 128th in the 2010 QS World University Ranking
Labels: University of Rochester, USA, World University Ranking

redpajama_set_name: RedPajamaCommonCrawl


text:
John Peterson, A Veteran Sailor, and His Wife Ann
Captain John Peterson, a longtime sailor in the United States and abroad, died on January 4, 1900. An obituary for Capt. Peterson appeared in the January 4, 1900 issue of the Norwalk Reflector, having been reprinted from the Sandusky Register. It read:
VETERAN SAILOR
Capt. John Peterson in the Haven of Eternal Rest
From the Sandusky Register
At midnight last night Captain John Peterson, one of the oldest, if not the oldest lake mariner, was called from this world into that port not tossed by storms. His death occurred at the residence of his daughter, Mrs. J. Holland, on East Adams Street, after an illness of some length. His career was in some respects most remarkable. He was born in Sonnderburg, Denmark, in 1812, and was at the time of his death 88 years old. He came to this country when a young man, and in 1837 settled at Huron, where his brother. Capt. J. D. Peterson, still resides. He followed the lakes for 53 years, during 43 years of which time he was master of some boats. In 1860 he made a trip from Huron to Liverpool, Eng., in the schooner Evelyn Bates. On this trip he  encountered the historic whirlwind storm which raged for six days and will be remembered by some of the older residents. In 1864 he came to Sandusky and has resided here since that time. He was captain of several boats, among which were the schooners C. N. Ryan and Provost. During the past ten years he has been of necessity in active on account of his advanced age. His wife died in 1881 and his only remaining relatives are his daughter and brother.
Capt. Peterson's wife, the former Ann Lee, had died in 1881. Both John and Ann Peterson are buried in Sandusky's Oakland Cemetery.
The Peterson monument stands tall in the western portion of Oakland Cemetery. John Peterson was a brave man, who faced danger on the waters, many a time. Ann Lee Peterson must have been a strong women, as both her husband, and her brother Seth Lee, were seafaring men. She had to face life head on, by herself, when her husband and brother were on lengthy trips.
John Landeck, Died from Consumption
Sentimental Sunday: Sandusky Library 1901 Glass Fl...
Mrs. Amelia Holland Marshall, 1817-1901


text:
A little bit of American religious history: Part 2
By Matt Tittle on October 7, 2007 at 9:00 AM
This is the middle portion of my talk at the University of Houston-Clear Lake last week. In this section, I address separation of church and state in 16th century Europe and 18th/19th century North America.
The status quo in 16th century Europe was either a corpus-Christianum (church-state) or a state-church such as Saxony, Zurich, and Geneva. The Anabaptists of the day, so named because of their view that baptism could not occur until someone was of sufficient age to determine for themselves whether to devote their lives to Christ…the Anabaptists were very concerned with ensuring the separation of church and state. They were the first to directly confront the status quo of church and state integration and coercion of the church by the state. The Anabaptists, on the grounds that the church could not be coerced, called for the disestablishment of the state church as a minimum requirement for religious freedom. This 16th century call for disestablishment will ring familiar in 18th and 19th century U.S. history.
The Anabaptists believed that the civil government denied spiritual government and so the two could not be in anyway related. The Anabaptist conviction toward separation of church and state included two vital positive affirmations:
1) The civic right of a free man to private religious interpretation.
2) The Christian duty of voluntary association to enforce a strong internal discipline.
In these two ideas lay the seeds of the U.S. Constitution's declaration of religious and individual freedom.
At the 1538 Bern Disputation, the Anabaptists declared that state authorities have a place in the non-Christian world, but the only authority of Christians was the Lord Jesus Christ. Again, the state had a specific role of keeping order in society, given the existence of those who perpetrate evil. What the Anabaptists did not recognize was government authority in spiritual matters.
Hans Denck is credited by some as being the first Anabaptist leader to articulate a person's right to individual religious interpretation. Otherwise, the Anabaptists were more concerned with the congregational level of religious liberty. Both of these approaches have specific parallels in the development of American political and religious notions of religious liberty. For example, congregational autonomy would be a primary goal of the Puritans in their declaration of the Cambridge Platform in 1648. I'll tell you an interesting story about the Cambridge Platform a little later. Today, the Unitarian-Universalists, United Church of Christ, the National Association of Congregational Christian Churches and the Conservative Congregational Christian Conference all claim some measure of heritage from the articles of the Cambridge Platform and the congregational polity that it established.
The separation of church and state is an issue that is most often taken for granted by Americans via the First Amendment of the U.S. Constitution's Bill of Rights. However, this issue is not as easily parsed as one might assume. Back in 16th century Europe, those calling for strict separation included the notion that religious leaders were prohibited from running for political office, and that politicians had to renounce their church membership before they could run. Imagine if that were the case in the U.S. today…not only would there be no Al Sharptons, Pat Robertsons, or Jesse Jacksons running for political office. We wouldn't be discussing the faith of the various candidates because they would have renounced their faith.
You may have heard that Republican candidate Fred Thompson said recently that he isn't a churchgoer. I don't know how well that will serve him in the polls, but at least he is honest with his answer. And interestingly, all of the candidates are being honest this year as they talk very openly about their faith….This emphasis on the religion and spirituality of those running for president on both sides of the aisle, is called integralism. It is a concept that isn't used much any more, but it means that one's religion ought to inform their social and political values. Basically, that we act with integrity by having our religion, politics, social values, family values, etc. all be in sync with one another. There is a refreshing honesty in such integrity. In the past, it seemed that many candidates either took on or changed their religious affiliation to get elected.
Back to separation of church and sate…We often hear popular and vehement idea that the U.S was established as a Christian nation. But many scholars contend that the influence of religious motives in bringing about the American Revolution is often overstated. While clergy were zealous at the time, church membership had actually reached a low point before the revolution. However, secular momentum took on a religious identity that I contend the government maintains today despite the religious freedom guaranteed by the First Amendment. George Washington was "identified publicly with both Moses and Joshua as a divinely appointed agent of deliverance from bondage." Thomas Jefferson even suggested that the seal of the U.S. include an image of Moses leading Israel out of bondage and into freedom.
As I imagine is the case for most Americans, I had come to believe over the years that the First Amendment was clear and easily interpretable within the context of a "wall" of separation. That is, neither institution could legally encroach into the affairs of the other. Some scholars have challenged the assumption that the First Amendment was drafted (or should be interpreted) as a statement of separation of church and state. Despite Thomas Jefferson's 1802 letter noting that the Amendment was nothing short of such a separation, the issue was initially one of disestablishment (i.e. the removal of a particular church as the officially recognized church). I am fondly reminded that I learned the word "antidisestablishmentarianism" in the 6th grade as the longest word in the English language. Our teacher tried to explain to us what it meant, but the meaning was lost on me at 11. Now I "get it." The antidisestablishmentarians were in part the separations…those opposed to disestablishment. The separationists actually lost the battle, and the disestablishmentarians won.
"Separation" was historically an anticlerical, antiecclesiastical movement, and was not what was desired by the dissenters who influenced the inclusion of the First Amendment. The dissenters wanted freedom from the laws recognizing religion and giving government salaries to ministers based on their religion. These dissenters were religious minorities, apparently trying to protect themselves from domination by larger religions, which might be recognized by the state, rather than their own direct domination by the state.
Just as the Anabaptists were minority dissenters in Reformation in Europe, various groups in the U.S. wanted the church to be free from government control. This is, of course, not a direct parallel. In 16th century Europe, new churches were being established, in 18th century North America a new state was being established. What the Anabaptists had yearned for, a government with no authority over church affairs and spirituality, the U.S. would apparently achieve.
"Separation" as a movement, despite Jefferson's earlier declaration wasn't popular again until the mid-19th century. Separationists were worried about the influence of the church on the government. They and the secularists fought for an amendment that guaranteed separation of church and state. When they couldn't get it, they went back to the notion that the First Amendment was sufficient. Here is an interesting notion.
At least one Catholic scholar in 1960, John Murry, stated that the first amendment stems from "the necessity of creating a social environment, protected by law, in which men of differing faiths can live together in peace." In this context, the first amendment is pluralistic, liberal, generous, not restrictive. However, he also asserts that, via the First Amendment, civil law is given authority over religious law, and that to even address religious freedom in the constitution is to make the state religious, which is antithetical to the purpose of religious freedom. Consequently, Murry says that separation of church and state implies a subordination of church to state, because the state decided the issue. But he says that the First Amendment is sufficient if viewed as an article of peace rather than an article of faith.
Seeing these interesting challenges to my preconceived notions about separation of church and state, I have decided to look again at the source. Of course, returning to the source is what generations of religious and political reformers alike reformers have done when faced with the morass that results from centuries of institutional trappings.
The First Amendment reads as follows: "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press, or the right of the people peaceably to assemble, and to petition the government for a redress of grievances." So, the First Amendment is a restriction against Congress in making laws that:
a) respect an establishment of religion,
b) prohibit the free exercise of religion,
c) abridge the freedom of speech,
d) abridge the freedom of the press,
e) abridge the right of the people peaceably to assemble,
f) abridge the right to petition the government for a redress of grievances.
Read in the broader context, I see this as a specific limitation of government power regarding religion, free speech, free press, peaceable assembly, and petition. I do not read this as a limitation on the church. I, unlike Thomas Jefferson, read "respecting an establishment of religion" to be a statement of disestablishment. I read "prohibiting the free exercise thereof," as a guarantee against persecution. Interestingly, the only other mention of religion in the U.S. Constitution is concerning qualification for public office and states that "no religious test shall ever be required." Again, I believe this is a declaration of disestablishment, prohibiting the state from respecting any particular church, but also prohibiting such influence by a church over the state.
Today we are presented with issues of church and state in which, all sides argue their case based on the first Amendment. Both those for and against maintaining the words "under God" in the Pledge of Allegiance invoke the First Amendment as justification – as did those in the case of Judge Roy Black and his placement of the Mosaic Covenant in an Alabama Courthouse. Indeed, even the U.S. Supreme Court building has an engraved image of Moses with the tablets on its exterior architecture. Does the United States enjoy true separation of church and state or are we a nation of two kingdoms, both ordained by God? As I have stated already, I don't think we enjoy true separation. Neither is the U.S. a church-state nor a state-church. We are both, but with a strong element of official disestablishment. I daresay that we will always live in the U.S. with a certain measure of dissonance in matters of church and state. Such dissonance is a natural by-product of religious pluralism and liberalism. Perhaps the Anabaptists would accuse us today of being simple magisterial reformers. Perhaps the radicals among us will keep us healthily away from either state or church domination in the realm of human values and meaning-making.
In a few days, I will conclude this series of posts with a discussion of the parallels between some of the founding religious and political documents in North America.
Keep the faith,
Rev. Matt
Matt Tittle


GRAZ, Austria ‒ On March 12-13, 2019, the American University of Armenia (AUA) Erasmus+ INCLUSION team participated in the Coordination Meeting and Workshop on Inclusive Teaching and Learning Methodology Toolkit Development (INCLUSION Project WP4). The meeting and workshop were held at Karl Franzens University of Graz (KFUG), Austria. Also attending the workshop were representatives from State Academy of Fine Arts of Armenia (SAFAA), Unison NGO for Support of People with Special Needs, University of Travnik (UNT), University of Tuzla (UNTZ), Sarajevo Meeting of Cultures (SMOC), World University Service (WUS), KFUG, University College Leuven-Limburg (UCLL), University of Roehampton (UoR), Armenian National Students' Association (ANSA), RA Ministry of Education and Science (MoES), Federal Ministry of Education and Science of Bosnia and Herzegovina (BiH), RA Ministry of Labor and Social Affairs (MLSA). The toolkit is intended for use by high school teachers that will be trained by AUA and SAFAA trainers.
AUA, as the leader of WP4 on Inclusive Teaching and Learning Methodology Toolkit Development, presented the progress made in WP4. The four AUA participants Mimi Zarookian, Adjunct Lecturer at the College of Humanities & Social Sciences (CHSS), Gayane Makaryan, AUA Grants Manager, as well as AUA students Elen Grigoryan (MPSIA '19) and Nektar Harutyunyan (CTR '19) led a World Café discussion on the draft toolkit with the consortium participants in attendance. They discussed the goals of the toolkit and the activities proposed for high school teachers within respective country specific contexts. Using the findings from the World Café and recommendations by European partners and BiH colleagues, AUA will circulate the guiding work plan among all consortium partners.
Additionally, as the lead partner of WP6, Makaryan briefed the attendees on the dissemination activities under WP6, after which she presented AUA's recommendations for developing the RA National Guidelines, the AUA INCLUSION Master Plan and implementation mechanisms for 2018-2019. Also, during the monitoring activity discussions conducted by WUS Austria and SAFAA, Zarookian and Makaryan presented project sustainability issues placing particular emphasis on public accessibility to assistive technologies, INCLUSION Master plan, delivery of on-going (preferably mandatory) faculty/staff trainings, etc. These are issues that AUA has addressed in its Strategic Plan.
Consortium partners then heard the presentation of the New Self-Assessment Quality Assurance Survey developed by WUS Austria. Once this toolkit is finalized, Higher Education Institution (HEI) staff will conduct a two-day training for high school teachers and faculty members in both program countries, Armenia and BiH, in May 2019.


Selected references for "When walking makes your legs hurt"
Bergan JJ et al. "Mechanisms of Disease: Chronic Venous Disease," The New England Journal of Medicine (August 3, 2006), Vol. 355, pp. 488-98.
Feldman EL and McCulloch DK. "Treatment of diabetic neuropathy." UpToDate (January 29, 2008).


text:
Tag "Jupiter Ascending"
The Wachowskis say their big-budget movie days are over
Jupiter Ascending has opened in theaters with weak numbers, grossing only $18 million. The Wachowski siblings, who directed the film, have been on a rocky road ever since after The Matrix
Jupiter Ascending Review
Way back in 1999, the Wachowskis created one of the best sci-fi films ever with The Matrix. Their ambitious creative approach to filmmaking changed sci-fi action films for years to come.
New trailer for Jupiter Ascending starring Channing Tatum and Mila Kunis
Jupiter Ascending, the film by Andy and Lana Wachowski (The Matrix Trilogy) that was pushed back to February 6, 2015, now has a new trailer, courtesy of Warner Bros. Pictures and Village
SDCC 2014: Saturday schedule revealed
• Preview night + Thursday • Friday • Sunday San Diego Comic-Con 2014 has just released the schedule for Saturday, July 26 and it comes with some very heavy hitters
'Jupiter Ascending' delayed to 2015
By now if you have been paying attention to the interwebs or have friends who do, you'll know that the sci-fi epic, Jupiter Ascending, has been delayed to February 2015. Why?
WB releases 'Jupiter Ascending' trailer
WB UK has released the trailer to the new Wachowski siblings' science fiction film, Jupiter Ascending starring Channing Tatum and Mila Kunis. The film was written by Lana and Andy
Nexus 2019, a pop-up bar inspired by Blade Runner, is coming to LA in November
The Witcher fans are upset with Yennefer casting in new photos
SDCC 2019: Conan O'Brien teases this year's Funko Pops
Get a first look at the Adidas x Naruto collaboration
Spider-Man: Far From Home in 4DX swings you right into the action
Conan pays homage to Into the Spiderverse with his cold open
SDCC 2019: IT: Chapter Two brings Pennywise's terrorizing antics to ScareDiego
Dragon Ball achieves simultaneous Kamehameha world record
NBA's Kyrie Irving shows off SpongeBob SquarePants collaboration
Skullcandy brings 12 Moods to ComplexCon Chicago
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New York rapper A$AP Ferg and Diddy's relationship go back further than people think. The rap heavyweights linked up this week for a few priceless hip-hop moments.
Heading into the weekend, Ferg shared the backstory behind his late dad's contributions to Puff Daddy's Bad Boy Records empire.


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Q: In Docker, how can I share files between containers and then save them to an image? I want to commit the data in a container's shared volume to an image. I cannot seem to do it? I kind of get the impression this perhaps is not possible in Docker but that seems totally at odds with the whole philosophy of not leaving data on the host so part of me thinks there must be a way to do this.
1. Terminal 1
Start up a container in Terminal 1 with a volume.
$ docker run -it -v /data ubuntu:14.10 /bin/bash
root@19fead4f6a68:/# echo "Hello Docker Volumes." > /data/foo.txt

2. Terminal 2
Start up a second container in Terminal 2 the file from container 1 is there so docker volumes are all working.
$ docker run -it --volumes-from 19fead4f6a68 ubuntu:14.10 /bin/bash

root@5c7cdbfc67d8:/# cat /data/foo.txt
Hello Docker Volumes.

3. Terminal 3
My understanding is that I can only commit diffs to images so I check what the diffs are on both the containers. For some bizarre reason my changes do not show up!??
$ docker diff 19fead4f6a68
A /data

$ docker diff 5c7cdbfc67d8
A /data

4. Back in Terminal 1
I create a file outside of the volume folder
 root@19fead4f6a68:/# echo "Docker you are a very strange beast...." > /var/beast.txt

5. Back in Terminal 3
We now have some changes we can commit although I am rather frustrated as this is not the data from the volume I needed to share with my other container.
$ docker diff 19fead4f6a68
A /data
C /var
A /var/beast.txt

Clearly this is by design. Anyone have any ideas as to why docker don't allow me to save volume data to a commit? Is there anyway at all to share files between containers and then save them to an image? I feel like there must be something I am missing? Especially to the ends of sharing data whilst avoiding host dependencies.

A: Volumes are outside of container images.  That's exactly what they are for - bringing data inside a container that isn't in the image.
From the Docker docs:

A data volume is a specially-designated directory within one or more containers that bypasses  the Union File System to provide several useful features for persistent or shared data:

*

*Data volumes can be shared and reused between containers

*Changes to a data volume are made directly

*Changes to a data volume will not be included when you update an image

If you want to save some changes as part of an image, make the changes inside the image and not in a volume.  If you want to share changes across multiple containers, put that data in a volume but you have to make your own arrangements for snapshots, rollback, etc., because Docker doesn't have that feature.
Maybe you would be interested in Flocker.

A: It looks as though there is an open issue around adding volume layers to docker:
https://github.com/docker/docker/issues/9382

redpajama_set_name: RedPajamaStackExchange


DJ Hero is as addictive as Guitar Hero!
Well it came as a shock to us to, we are all of the metal persuasion when it comes to music, but DJ Hero may well be good enough to convert rockers to ravers!
The new game has been out for a few days now and having battled the shopping masses to get the game on release day, we have had some time to sit down and really get into the game. coming from the same makers as the Guitar Hero series you would be correct in assuming it shares a lot of the same features (renamed but still there, thinly disguised!) and some of those skills your fingers developed in GH will certainly come in handy while mixing.
The game operates as if you were a DJ playing 2 records at the same time, mixing and scratching between them and adding your samples over the top, this is easily represented in the game by the green and blue glowing lines as your two records, which can be scratched and played independently of each other or at the same time by use of the crossfader. You also have the samples which are represented by the red line, this allows you to play in the samples the song requires but also gives you the ability to throw in some of your own when you get the chance - not exactly contributing to the song very well but more making your friends laugh at all the air horns you are putting over an otherwise great track.
The mixes and DJ's represent a real variety of DJ based music from hip hop, old school, funk, r n b, dance, electronica and scratching genres and even through you may not think you'd like the music, when it feels like you have some control over it you really do feel involved.
The DJ controller is small but perfectly formed, it feels good, works well (so far!), and is not too big to have lying around with all your other plastic toys. We have done a complete stripdown of the controller and are in the process of getting the article ready at the moment, as soon as it is done we can show you the inner workings so all you modders can start thinking of how to pimp it up a little!
The longevity of the game will depend on DLC (and how deep your pockets are) and how much you love the music but with the difficulty akin to maybe GHWT, most people should be able to 4/5 star things on easy after a bit of practise but hard and then expert will take some work, this should last a good while.
Xbox Live gold members can head over to the game demos section and download a free playable demo of Band Hero, the latest offering in the Guitar Hero Family.
Band Hero is built using the same basic engine as Guitar Hero 5, the look and feel of the game is very similar. The big differences between the two games is the target audience, Band hero caters for a more diverse audience, it is easier to pick up and play than some Guitar Hero titles and the music is more mainstream with more pop hits including tracks like Walking On Sunshine (Katrina & The Waves) which is included along with two other decent tracks in the demo version.
- 3 Doors Down - "When I'm Gone"
- The Airborne Toxic Event - "Gasoline"
- The All American Rejects - "Dirty Little Secret"
- Aly and AJ - "Like Whoa"
- Angels & Airwaves - "The Adventure"
- Ben Harper and the Innocent Criminals - "Steal My Kisses"
- Big Country - "In a Big Country"
- The Bravery - "Believe"
- Carl Douglas - "Kung Fu Fighting"
- Cheap Trick - "I Want You To Want Me (live)"
- Cold War Kids - "Hang Me Up To Dry"
- Corinne Bailey Rae - "Put Your Records On"
- Counting Crows - "Angels of the Silences"
- Culture Club - "Do You Really Want To Hurt Me"
- Dashboard Confessional - "Hands Down"
- David Bowie - "Let's Dance"
- Devo - "Whip It"
- Don McLean - "American Pie"
- Duffy - "Warwick Avenue"
- Duran Duran - "Rio"
- Evanescence - "Bring Me To Life"
- Everclear - "Santa Monica (Watch The World Die)"
- Fall Out Boy - "Sugar, We're Goin' Down"
- Filter - "Take A Picture"
- Finger Eleven - "Paralyzer"
- The Go-Go's - "Our Lips Are Sealed"
- Hilary Duff - "So Yesterday"
- Hinder - "Lips Of An Angel"
- Jackson 5 - "ABC"
- Janet Jackson - "Black Cat"
- Jesse McCartney - "Beautiful Soul"
- Joan Jett - "Bad Reputation"
- Joss Stone - "You Had Me"
- Katrina and The Waves - "Walking On Sunshine"
- The Kooks - "Naive"
- KT Tunstall - "Black Horse and the Cherry Tree"
- The Last Goodnight - "Pictures Of You"
- Lily Allen - "Take What You Take"
- Maroon 5 - "She Will Be Loved"
- Marvin Gaye - "I Heard It Through The Grapevine"
- Mighty Mighty Bosstones - "The Impression That I Get"
- Nelly Furtado - "Turn Off The Light"
- No Doubt - "Just A Girl"
- No Doubt - "Don't Speak"
- OK Go - "A Million Ways"
- Papa Roach - "Lifeline"
- Parachute - "Back Again"
- Pat Benatar - "Love Is A Battlefield"
- Poison - "Every Rose Has Its Thorn"
- Robbie Williams and Kylie Minogue - "Kids"
- The Rolling Stones - "Honky Tonk Women"
- Roy Orbison - "Oh Pretty Woman"
- Santigold - "L.E.S. Artistes"
- Snow Patrol - "Take Back the City"
- Spice Girls - "Wannabe"
- Styx - "Mr. Roboto"
- Taylor Swift - "Love Story"
- Taylor Swift - "Picture To Burn"
- Taylor Swift - "You Belong With Me"
- Tonic - "If You Could Only See"
- The Turtles - "Happy Together"
- Village People - "YMCA"
- Yellowcard - "Ocean Avenue"
There are some great songs in there even if they are not ear-bleeding guitar solo tracks, they will make a great playlist at any party and should go someway to combining the (and this is not a sexist view just personal experience) mainly female played Singstar, and mainly male played Guitar Hero. Just imagine finding a game that you and your girlfriend can enjoy at the same time - what a novelty!
One of the most welcome bits of news included in this Band Hero announcement is the inclusion of the song import function. As you can transfer tracks from GHWT to GH5, you can also transfer the GHWT songs and GH5 songs into Band Hero or vice versa.
In conclusion, this should be a great game and a welcome addition to your now towering pile of Guitar Hero titles.
Use your GHWT drums on your PC as e-drums!
We wrote an article a while ago with a great deal of help from one of our visitors showing you how you can use your e-drums as a Guitar Hero Game Controller. This was a very popular article with lots of interest.
Now the cleaver guys over at pctutorialsonline.net have written the software and created some great tutorial videos showing how to connect your Guitar Hero World Tour drums to the PC and use them like a real professional e-drum kit. So now we have the best of both worlds, whatever skins you own can be used for gaming and creating music!
I mentioned a while ago that I would create a how to video on using your Guitar Hero World Tour Drum kit on your PC. Thanks to Magnus' PS360MIDI Drummer software, the ability to use the GH:WT drum kit on PC became possible. To think that you could turn a gaming controller into a high quality midi controller is amazing. Something like a Yamaha DTXpress costs $800 AU + .
I encourage you all to pop over and have a look at what they have created, it is quite amazing!


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Q: Turbo C++ GCC Compiler I'm currently developing a gui application in turbo c++ (mandatory) for a project using C language, and i need to invoke turbo c++'s compiler(gcc), my question is HOW DO I CALL IT? i can't find any sources in the internet regarding this.
here's a snippet of my code
int program(){
 int opt=-1,j;
 char menu[4][20]={"Open File","Compile", "Run","Quit"};
 close=1;
 dropmenu(menu,10,33,131,105,opt);
 do{
  showmouse();
  getmousepos(&buttonm,&xm,&ym);
  if(xm>=10+10&&xm<=131-10&&ym>=33+8&&ym<=105-8&&buttonm==1){
   for(j=0;j<(105-33-8)/14;j++)
    if((ym-33-8)/14==j){
     opt=j;
     break;
    }
   dropmenu(menu,10,33,131,105,opt);
   switch(opt){
    case 0: openFile(); break;
    case 1: compile(); break;
    case 2: run(); break;
    case 3: delay(100);cleardevice();closegraph();exit(0);
   }
  }else if(xm>=10&&xm<=34&&ym>=18&&ym<=32&&buttonm==1){
   dropmenu(menu,10,33,131,105,opt);
   continue;
  }else if(buttonm==1){
   break;
  }
 }while(close);
 return 0;
}
void openFile() {

}
void compile() {
//i would like to put that invoking here
}
void run() {

}

A: Firstly gcc is not equivalent to turbo-c. turbo uses tc for compiling the codes. You can probably find that from the documentations of turbo c. To compile a file you can use system function. This function helps to execute command on the turbo c shell. I am not sure gcc would be accessible from the turbo shell. Since turbo elevates(mount) the directories giving it restricted permissions only. Also if you want to use the system it would be like following:
system("tc source.c -o destination");

    or

system("gcc source.c -o  destination");

remember the above code also shows error if any in the text mode only therefore you might want to redirect them to some file. You can find out about redirecting of output of command line from google. There are many resources about it.


7/8"custom braided oil lines with correct 30mm radius Porsche style ball end with OEM fittings will be included to replace the stock oil lines.
Stainless steel heater boxes include additional piping to run heat into the cabin.
Cold Air Intake Kit improves induction into the intake manifold and is a direct replacement for the large, restrictive OEM metal intake box and filter.
Direct replacement for the OEM muffler and catalytic converter assembly.