Network Working Group R. Bless Request for Comments: 3754 Univ. of Karlsruhe Category: Informational K. Wehrle Univ. of Tuebingen April 2004 IP Multicast in Differentiated Services (DS) Networks
Status of this Memo
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 Notice
Copyright (C) The Internet Society (2004). All Rights Reserved.
Abstract
This document discusses the problems of IP Multicast use in
Differentiated Services (DS) networks, expanding on the discussion in RFC 2475 ("An Architecture of Differentiated Services"). It also
suggests possible solutions to these problems, describes a potential implementation model, and presents simulation results.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Management of Differentiated Services. . . . . . . . . . 2
2. Problems of IP Multicast in DS Domains . . . . . . . . . . . . 3 2.1. Neglected Reservation Subtree Problem (NRS Problem). . . 4 2.2. Heterogeneous Multicast Groups . . . . . . . . . . . . . 12
2.3. Dynamics of Any-Source Multicast . . . . . . . . . . . . 13
3. Solutions for Enabling IP-Multicast in Differentiated
Services Networks. . . . . . . . . . . . . . . . . . . . . . . 13 3.1. Solution for the NRS Problem . . . . . . . . . . . . . . 13 3.2. Solution for Supporting Heterogeneous Multicast Groups . 15
3.3. Solution for Any-Source Multicast. . . . . . . . . . . . 16
4. Scalability Considerations . . . . . . . . . . . . . . . . . . 16
5. Deployment Considerations. . . . . . . . . . . . . . . . . . . 17
6. Security Considerations. . . . . . . . . . . . . . . . . . . . 18
7. Implementation Model Example . . . . . . . . . . . . . . . . . 18
8. Proof of the Neglected Reservation Subtree Problem . . . . . . 19 8.1. Implementation of the Proposed Solution. . . . . . . . . 20
8.2. Test Environment and Execution . . . . . . . . . . . . . 21
9. Simulative Study of the NRS Problem and Limited Effort PHB . . 23 Bless & Wehrle Informational [Page 1]
9.1. Simulation Scenario. . . . . . . . . . . . . . . . . . . 24
9.2. Simulation Results for Different Router Types. . . . . . 26
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 31
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31 11.1. Normative References . . . . . . . . . . . . . . . . . . 31
11.2. Informative References . . . . . . . . . . . . . . . . . 31
12. Authors’ Addresses . . . . . . . . . . . . . . . . . . . . . . 33
13. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 34 1. Introduction
This document discusses the problems of IP Multicast use in
Differentiated Services (DS) networks, expanding on the discussion in RFC 2475 ("An Architecture of Differentiated Services"). It also
suggests possible solutions to these problems, describes a potential implementation model, and presents simulation results.
The "Differentiated Services" (DiffServ or DS) approach [1, 2, 3]
defines certain building blocks and mechanisms to offer qualitatively better services than the traditional best-effort delivery service in an IP network. In the DiffServ Architecture [2], scalability is
achieved by avoiding complexity and maintenance of per-flow state
information in core nodes, and by pushing unavoidable complexity to
the network edges. Therefore, individual flows belonging to the same service are aggregated, thereby eliminating the need for complex
classification or managing state information per flow in interior
nodes.
On the other hand, the reduced complexity in DS nodes makes it more
complex to use those "better" services together with IP Multicast
(i.e., point-to-multipoint or multipoint-to-multipoint
communication). Problems emerging from this fact are described in
section 2. Although the basic DS forwarding mechanisms also work
with IP Multicast, some facts have to be considered which are related to the provisioning of multicast resources. It is important to
integrate IP Multicast functionality into the architecture from the
beginning, and to provide simple solutions for those problems that
will not defeat the already gained advantages.
1.1. Management of Differentiated Services
At least for Per-Domain Behaviors and services based on the EF PHB,
admission control and resource reservation are required [14, 15].
Installation and updating of traffic profiles in boundary nodes is
necessary. Most network administrators cannot accomplish this task
manually, even for long term service level agreements (SLAs).
Furthermore, offering services on demand requires some kind of
signaling and automatic admission control procedures.
Bless & Wehrle Informational [Page 2]
However, no standardized resource management architecture for
DiffServ domains exists. The remainder of this document assumes that at least some logical resource management entity is available to
perform resource-based admission control and allotment functions.
This entity may also be realized in a distributed fashion, e.g.,
within the routers themselves. Detailed aspects of the resource
management realization within a DiffServ domain, as well as the
interactions between resource management and routers or end-systems
(e.g., signaling for resources), are out of scope of this document.
Protocols for signaling a reservation request to a Differentiated
Services Domain are required. For accomplishing end-system signaling to DS domains, RSVP [4] may be used with new DS specific reservation objects [5]. RSVP provides support for multicast scenarios and is
already supported by many systems. However, application of RSVP in a DiffServ multicast context may lead to problems that are also
described in the next section. The NSIS Working Group is currently
defining new signaling protocols that may show a different behavior, but the WG has its current focus more on unicast flows than on
multicast flows.
2. Problems of IP Multicast in DS Domains
Although potential problems and the complexity of providing multicast with Differentiated Services are considered in a separate section of [2], both aspects have to be discussed in greater detail. The
simplicity of the DiffServ Architecture and its DS node types is
necessary to reach high scalability, but it also causes fundamental
problems in conjunction with the use of IP Multicast in DS domains.
The following subsections describe these problems for which a generic solution is proposed in section 3. This solution is as scalable as
IP Multicast and needs no resource separation by using different
codepoint values for unicast and multicast traffic.
Because Differentiated Services are unidirectional by definition, the point-to-multipoint communication is also considered as
unidirectional. In traditional IP Multicast, any node can send
packets spontaneously and asynchronously to a multicast group
specified by their multicast group address, i.e., traditional IP
Multicast offers a multipoint-to-multipoint service, also referred to as Any-Source Multicast. Implications of this feature are discussed in section 2.3.
For subsequent considerations we assume, unless stated otherwise, at least a unidirectional point-to-multipoint communication scenario in which the sender generates packets which experience a "better" Per-
Hop-Behavior than the traditional default PHB, resulting in a service of better quality than the default best-effort service. In order to Bless & Wehrle Informational [Page 3]
accomplish this, a traffic profile corresponding to the traffic
conditioning specification has to be installed in the sender’s first DS-capable boundary node. Furthermore, it must be assured that the
corresponding resources are available on the path from the sender to all the receivers, possibly requiring adaptation of traffic profiles at involved domain boundaries. Moreover, on demand resource
reservations may be receiver-initiated.
2.1. Neglected Reservation Subtree Problem (NRS Problem)
Typically, resources for Differentiated Services must be reserved
before they are used. But in a multicast scenario, group membership is often highly dynamic, thereby limiting the use of a sender-
initiated resource reservation in advance. Unfortunately, dynamic
addition of new members of the multicast group using Differentiated
Services can adversely affect other existing traffic if resources
were not explicitly reserved before use. A practical proof of this
problem is given in section 8.
IP Multicast packet replication usually takes place when the packet
is handled by the forwarding core (cf. Fig. 1), i.e., when it is
forwarded and replicated according to the multicast forwarding table. Thus, a DiffServ capable node would also copy the content of the DS
field [1] into the IP packet header of every replicate.
Consequently, replicated packets get exactly the same DS codepoint
(DSCP) as the original packet, and therefore experience the same
forwarding treatment as the incoming packets of this multicast group. This is also illustrated in Fig. 1, where each egress interface
comprises functions for (BA-) classification, traffic conditioning
(TC), and queueing.
Interface A IP Forwarding Interface B
+-----------+ +--------------+ +-----------+
MC-flow | | | replication | | egress |
---->| ingress |---->|------+-------|----->|(class.,TC,|---->
| | | | | | queueing) |
+-----------+ | | | +-----------+
| | |
| | | Interface C
| | | +-----------+
| | | | egress |
| +-------|----->|(class.,TC,|---->
| | | queueing) |
+--------------+ +-----------+
Figure 1: Multicast packet replication in a DS node
Bless & Wehrle Informational [Page 4]
Normally, the replicating node cannot test whether a corresponding
resource reservation exists for a particular flow of replicated
packets on an output link (i.e., its corresponding interface). This is because flow-specific information (e.g., traffic profiles) is
usually not available in every boundary and interior node.
When a new receiver joins an IP Multicast group, a multicast routing protocol (e.g., DVMRP [6], PIM-DM [7] or PIM-SM [8]) grafts a new
branch to an existing multicast tree in order to connect the new
receiver to the tree. As a result of tree expansion, missing per-
flow classification, and policing mechanisms, the new receiver will
implicitly use the service of better quality, because of the "better" copied DSCP.
If the additional amount of resources which are consumed by the new
part of the multicast tree are not taken into account by the domain
resource management (cf. section 1.1), the currently provided quality of service of other receivers (with correct reservations) will be
affected adversely or even violated. This negative effect on
existing traffic contracts by a neglected resource reservation -- in the following designated as the Neglected Reservation Subtree Problem (NRS Problem) -- must be avoided under all circumstances. Strong
admission control policies at the domain boundary will not help to
prevent this problem either, because the new flow that inadmissibly
consumes resources has its origin inside the domain.
One can distinguish two major cases of the NRS Problem. They show a different behavior depending on the location of the branching point. In order to compare their different effects, a simplistic example of a share of bandwidth is illustrated in Fig. 2 and is used in the
following explanations. Neither the specific PHB types nor their
assigned bandwidth share are important; however, their relative
priority with respect to each other is of importance.
40% 40% 20%
+--------------------+---------------------+------------+
|Expedited Forwarding| Assured Forwarding | Best-Effort|
+--------------------+---------------------+------------+
---------------------------------------------------------->
output link bandwidth
Figure 2: An example bandwidth share of different
behavior aggregates
Bless & Wehrle Informational [Page 5]
The bandwidth of the considered output link is shared by three types of services (i.e., by three behavior aggregates): Expedited
Forwarding, Assured Forwarding, and the traditional Best-Effort
service. In this example, we assume that routers perform strict
priority queueing, where EF has the highest, AF the middle, and
Best-Effort the lowest assigned scheduling priority. Though not
mandatory for an EF implementation, a strict non-preemptive priority scheduler is one implementation option as described in section 5.1.1 of RFC 3247 [15]. Were Weighted Fair Queueing (WFQ) to be used, the described effects would essentially also occur, but with minor
differences. In the following scenarios, it is illustrated that PHBs of equal or lower priority (in comparison to the multicast flow’s
PHB) are affected by the NRS problem.
The Neglected Reservation Subtree problem appears in two different
cases:
o Case 1: If the branching point of the new subtree (at first only a branch) and the previous multicast tree is a (egress) boundary
node, as shown in Fig. 3, the additional multicast flow now
increases the total amount of used resources for the corresponding behavior aggregate on the affected output link. The total amount will be greater than the originally reserved amount.
Consequently, the policing component in the egress boundary node
drops packets until the traffic aggregate is in accordance with
the traffic contract. But while dropping packets, the router can not identify the responsible flow (because of missing flow
classification functionality), and thus randomly discards packets, whether they belong to a correctly behaving flow or not. As a
result, there will no longer be any service guarantee for the
flows with properly reserved resources.
Bless & Wehrle Informational [Page 6]
Sender
+---+
| S | DS domains
+---+ / \
.||............... / \ ................
. || .<- ->. .
. || . . .
. +---+ +--+ +--+ *) +--+ +--+ +--+ +------+ . |FHN|===|IN|=====|BN|###########|BN|####|IN|######|BN|####|Recv.B| . +---+ +--+ +--+\\ +--+ +--+ +--+ +------+ . \\ \ . \\ . \ .
. +--+ +--+ . \\ . \ .
. |IN|-----|IN| . \\ . +--+ .
. +--+ +--+ . \\ ..........|BN|..
. || \ . +------+ +--+
. || \ . |Recv.A|
.+--+ +--+. +------+
|BN|........|BN|
+--+ +--+
||
S: Sender
Recv.x: Receiver x
FHN: First-Hop Node
BN: Boundary Node
IN: Interior Node
===: Multicast branch with reserved bandwidth
###: Multicast branch without reservation
*) Bandwidth of EF aggregated on the output link is higher than
actual reservation, EF aggregate will be limited in bandwidth
without considering the responsible flow.
Figure 3: The NRS Problem (case 1) occurs when Receiver
B joins
In figure 3, it is assumed that receiver A is already attached to the egress boundary node (BN) of the first domain. Furthermore,
resources are properly reserved along the path to receiver A and
used by correspondingly marked packets. When receiver B joins the same group as receiver A, packets are replicated and forwarded
along the new branch towards the second domain with the same PHB
as for receiver A. If this PHB is EF, the new branch possibly
exhausts allotted resources for the EF PHB, adversely affecting
other EF users that receive their packets over the link that is
marked with the *). The BN usually ensures that outgoing traffic aggregates to the next domain are conforming to the agreed traffic conditioning specification. The egress BN will, therefore, drop
packets of the PHB type that are used for the multicast flow.
Bless & Wehrle Informational [Page 7]
Other PHBs of lower or higher priority are not affected adversely in this case. The following example in Fig. 4. illustrates this for two PHBs.
+------------------+---------------------+--------------+------+
| Expedited Forw. | Expedited Forw. | Assured Forw.| BE |
| | | | |
| with reservation | excess flow | with reserv. | |
| | without reservation | | |
+------------------+---------------------+--------------+------+
| EF with and without reservation share | 40 % | 20% |
| 40% of reserved EF aggregate. | | |
| -> EF packets with reservation and | | |
| without reservation will be | | |
| discarded! | | |
+------------------+---------------------+--------------+------+
(a) Excess flow has EF codepoint
+------------------+---------------------+--------------+------+
| Expedited Forw. | Assured Forwarding | Assured Forw.| BE |
| | | | |
| with reservation | excess flow | with reserv. | |
| | without reservation | | |
+------------------+---------------------+--------------+------+
| | AF with & without reservation share| 20 % |
| | 40% of reserved EF aggregate. | |
| 40% | -> EF packets with reservation and | |
| | without reservation will be | |
| | discarded! | |
+------------------+---------------------+--------------+------+
(b) Excess flow has AF codepoint
Figure 4: Resulting share of bandwidth in a egress
boundary node with a neglected reservation of
(a) an Expedited Forwarding flow or (b) an
Assured Forwarding flow.
Fig. 4 shows the resulting share of bandwidth in cases when (a)
Expedited Forwarding and (b) Assured Forwarding is used by the
additional multicast branch causing the NRS Problem. Assuming
that the additional traffic would use another 30% of the link
bandwidth, Fig. 4 (a) illustrates that the resulting aggregate of Expedited Forwarding (70% of the outgoing link bandwidth) is
throttled down to its originally reserved 40%. In this case, the amount of dropped EF bandwidth is equal to the amount of excess
bandwidth. Consequently, the original Expedited Forwarding
Bless & Wehrle Informational [Page 8]
aggregate (which had 40% of the link bandwidth reserved) is also
affected by packet losses. The other services, e.g., Assured
Forwarding or Best-Effort, are not disadvantaged.
Fig. 4 (b) shows the same situation for Assured Forwarding. The
only difference is that now Assured Forwarding is solely affected by discards, as the other services will still get their
guarantees. In either case, packet losses are restricted to the
misbehaving service class by the traffic meter and policing
mechanisms in boundary nodes. Moreover, the latter problem (case 1) occurs only in egress boundary nodes because they are
responsible for ensuring that the traffic leaving the
Differentiated Services domain is not more than the following
ingress boundary node will accept. Therefore, those violations of SLAs will already be detected and processed in egress boundary
nodes.
o Case 2: The Neglected Reservation Subtree problem can also occur
if the branching point between the previous multicast tree and the new subtree is located in an interior node (as shown in Fig. 5).
In Fig. 5, it is assumed that receivers A and B have already
joined the multicast group and have reserved resources
accordingly. The interior node in the second domain starts
replication of multicast packets as soon as receiver C joins.
Because the router is not equipped with metering or policing
functions, it will not recognize any amount of excess traffic and will forward the new multicast flow. If the latter belongs to a
higher priority service, such as Expedited Forwarding, bandwidth
of the aggregate is higher than the aggregate’s reservation at the new branch and will use bandwidth from lower priority services. Bless & Wehrle Informational [Page 9]
Sender
+---+
| S | DS domains
+---+ / \
.||............... / \ ................
. || .<- ->. .
. || . . .
. +---+ +--+ +--+ +--+ +--+ +--+ +------+ . |FHN|===|IN|=====|BN|===========|BN|====|IN|======|BN|===|Recv.B| . +---+ +--+ +--+\\ +--+ +--+ +--+ +------+ . \\ \ . \\ . # .
. +--+ +--+ . \\ . # *) .
. |IN|-----|IN| . \\ . +--+ .
. +--+ +--+ . \\ ..........|BN|..
. || \ . +------+ +--+
. || \ . |Recv.A| #
.+--+ +--+. +------+ #
|BN|........|BN| +------+
+--+ +--+ |Recv.C|
|| +------+
FHN: First-Hop Node, BN: Boundary Node, Recv.x: Receiver x
S: Sender, IN: Interior Node
===: Multicast branch with reserved bandwidth
###: Multicast branch without reservation
*) Bandwidth of EF aggregated on the output link is higher than
actual reservation, EF aggregate will be limited in bandwidth
without considering the responsible flow
Figure 5: Neglected Reservation Subtree problem case 2
after join of receiver C
Bless & Wehrle Informational [Page 10]
The additional amount of EF without a corresponding reservation is forwarded together with the aggregate which has a reservation.
This results in no packet losses for Expedited Forwarding as long as the resulting aggregate is not higher than the output link
bandwidth. Because of its higher priority, Expedited Forwarding
gets as much bandwidth as needed and as is available. The effects on other PHBs are illustrated by the following example in Fig. 6. +------------------+---------------------+--------------+------+
| Expedited Forw. | Expedited Forw. | Assured Forw.| BE |
| | | | |
| with reservation | excess flow | with reserv. | |
| | without reservation | | |
+------------------+---------------------+--------------+------+
| 40% | 30% | 30% | 0% |
+------------------+---------------------+--------------+------+
EF with reservation and the excess flow use together 70%
of the link bandwidth because EF, with or without reservation,
has the highest priority.
(a) Excess flow has EF codepoint
+------------------+---------------------+--------------+------+
| Expedited Forw. | Assured Forw. | Assured Forw.| BE |
| | | | |
| with reservation | excess flow | with reserv. | |
| | without reservation | | |
+------------------+---------------------+--------------+------+
| 40% | 60% | 0% |
| | (10% loss) | |
+------------------+---------------------+--------------+------+
AF with reservation and the excess flow use together 60%
of the link bandwidth because EF has the highest priority
(-> 40%). 10% of AF packets will be lost.
(b) Excess flow has AF codepoint
Figure 6: Resulting share of bandwidth in an interior
node with a neglected reservation of (a) an
Expedited Forwarding flow or (b) an Assured
Forwarding flow
The result of case 2 is that there is no restriction for Expedited Forwarding, but as Fig. 6 (a) shows, other services will be
extremely disadvantaged by this use of non-reserved resources.
Their bandwidth is used by the new additional flow. In this case, the additional 30% Expedited Forwarding traffic preempts resources from the Assured Forwarding traffic, which in turn preempts
Bless & Wehrle Informational [Page 11]
resources from the best-effort traffic, resulting in 10% packet
losses for the Assured Forwarding aggregate, and a complete loss
of best-effort traffic. The example in Fig. 6 (b) shows that this can also happen with lower priority services like Assured
Forwarding. When a reservation for a service flow with lower
priority is neglected, other services (with even lower priority)
can be reduced in their quality (in this case the best-effort
service). As shown in the example, the service’s aggregate
causing the NRS problem can itself be affected by packet losses
(10% of the Assured Forwarding aggregate is discarded). Besides
the described problems of case 2, case 1 will occur in the DS
boundary node of the next DS domain that performs traffic metering and policing for the service aggregate.
Directly applying RSVP to Differentiated Services would also result
in temporary occurrence of the NRS Problem. A receiver has to join
the IP multicast group to receive the sender’s PATH messages, before being able to send a resource reservation request (RESV message).
Thus, the join message on the link for receiving PATH messages can
cause the NRS Problem, if this situation is not handled in a special way (e.g., by marking all PATH messages with codepoint 0 and dropping or re-marking all other data packets of the multicast flow).
2.2. Heterogeneous Multicast Groups
Heterogeneous multicast groups contain one or more receivers, which
would like to get another service or quality of service as the sender provides or other receiver subsets currently use. A very important
characteristic which should be supported by Differentiated Services
is that participants requesting a best-effort quality only should
also be able to participate in a group communication which otherwise utilizes a better service class. The next better support for
heterogeneity provides concurrent use of more than two different
service classes within a group. Things tend to get even more complex when not only different service classes are required, but also
different values for quality parameters within a certain service
class.
A further problem is to support heterogeneous groups with different
service classes in a consistent way. It is possible that some
services will not be comparable to each other so that one service
cannot be replaced by the other, and both services have to be
provided over the same link within this group.
Because an arbitrary new receiver that wants to get the different
service can be grafted to any point of the current multicast delivery tree, even interior nodes may have to replicate packets using the
different service. At a first glance, this seems to be a
Bless & Wehrle Informational [Page 12]
contradiction with respect to simplicity of the interior nodes,
because they do not even have a profile available and should now
convert the service of quality of individual receivers.
Consequently, in order to accomplish this, interior nodes have to
change the codepoint value during packet replication.
2.3. Dynamics of Any-Source Multicast
Basically, within an IP multicast group, any participant (actually,
it can be any host not even receiving packets of this multicast
group) can act as a sender. This is an important feature which
should also be available in case a specific service other than best- effort is used within the group. Differentiated Services possess,
conceptually, a unidirectional character. Therefore, for every
multicast tree implied by a sender, resources must be reserved
separately if simultaneous sending should be possible with a better
service. This is even true if shared multicast delivery trees are
used (e.g., with PIM-SM or Core Based Trees). If not enough
resources are reserved for a service within a multicast tree allowing simultaneous sending of more than one participant, the NRS problem
will occur again. The same argument applies to half-duplex
reservations which would share the reserved resources by several
senders, because it cannot be ensured by the network that exactly one sender sends packets to the group. Accordingly, the corresponding
RSVP reservation styles "Wildcard Filter" and "Shared-Explicit
Filter" [4] cannot be supported within Differentiated Services. The Integrated Services approach is able to ensure the half-duplex nature of the traffic, because every router can check each packet for its
conformance with the installed reservation state.
3. Solutions for Enabling IP-Multicast in Differentiated Services
Networks
The problems described in the previous section are mainly caused by
the simplicity of the Differentiated Services architecture.
Solutions that do not introduce additional complexity need to be
introduced so as to not diminish the scalability of the DiffServ
approach. This document suggests a straightforward solution for most of the problems.
3.1. Solution for the NRS Problem
The proposed solution consists conceptually of the following three
steps that are described in more detail later.
Bless & Wehrle Informational [Page 13]
1. A new receiver joins a multicast group that is using a DiffServ service. Multicast routing protocols accomplish the connection of the new branch to the (possibly already existing) multicast delivery tree as usual.
2. The unauthorized use of resources is avoided by re-marking at
branching nodes all additional packets departing down the new
branch. At first, the new receiver will get all packets of the multicast group without quality of service. The management
entity of the correspondent DiffServ domain may get informed
about the extension of the multicast tree.
3. If a pre-issued reservation is available for the new branch or somebody (receiver, sender or a third party) issues one, the
management entity instructs the branching router to set the
corresponding codepoint for the demanded service.
Usage of resources which were not previously reserved must be
prevented. In the following example, we consider a case where the
join of a new receiver to a DS multicast group requires grafting of a new branch to an already existing multicast delivering tree. The
connecting node that joins both trees converts the codepoint (and
therefore the Per-Hop Behavior) to a codepoint of a PHB which is
similar to the default PHB in order to provide a best-effort-like
service for the new branch. More specifically, this particular PHB
can provide a service that is even worse than the best-effort service of the default PHB. See RFC 3662 [16] for a corresponding Lower
Effort Per-Domain Behavior.
The conversion to this specific PHB could be necessary in order to
avoid unfairness being introduced within the best-effort service
aggregate, and, which results from the higher amount of resource
usage of the incoming traffic belonging to the multicast group. If
the rate at which re-marked packets are injected into the outgoing
aggregate is not reduced, those re-marked packets will probably cause discarding of other flow’s packets in the outgoing aggregate if
resources are scarce.
Therefore, the re-marked packets from this multicast group should be discarded more aggressively than other packets in this outgoing
aggregate. This could be accomplished by using an appropriately
configured PHB (and a related DSCP) for those packets. In order to
distinguish this kind of PHB from the default PHB, it is referred to as the Limited Effort (LE) PHB (which can be realized by an
appropriately configured AF PHB [9] or Class Selector Compliant PHB
[1]) throughout this document. Merely dropping packets more
aggressively at the re-marking node is not sufficient, because there may be enough resources in the outgoing behavior aggregate (BA) to Bless & Wehrle Informational [Page 14]
transmit every re-marked packet without having to discard any other
packets within the same BA. However, resources in the next node may be short for this particular BA. Those "excess" packets, therefore, must be identifiable at this node.
Re-marking packets is only required at branching nodes, whereas all
other nodes of the multicast tree (such with outdegree 1) replicate
packets as usual. Because a branching node may also be an interior
node of a domain, re-marking of packets requires conceptually per-
flow classification. Though this seems to be in contradiction to the DiffServ philosophy of a core that avoids per-flow states, IP
multicast flows are different from unicast flows: traditional IP
multicast forwarding and multicast routing are required to install
states per multicast group for every outgoing link anyway.
Therefore, re-marking in interior nodes is scalable to the same
extent as IP multicast (cf. section 4).
Re-marking with standard DiffServ mechanisms [10] for every new
branch requires activation of a default traffic profile. The latter accomplishes re-marking by using a combination of an MF-classifier
and a marker at an outgoing link that constitutes a new branch. The classifier will direct all replicated packets to a marker that sets
the new codepoint. An alternative implementation is described in
section 7.
The better service will only be provided if a reservation request was processed and approved by the resource management function. That
means an admission control test must be performed before resources
are actually used by the new branch. In case the admission test is
successful, the re-marking node will be instructed by the resource
management to stop re-marking and to use the original codepoint again (conceptually by removing the profile).
In summary, only those receivers will obtain a better service within a DiffServ multicast group, which previously reserved the
corresponding resources in the new branch with assistance of the
resource management. Otherwise, they get a quality which might be
even lower than best-effort.
3.2. Solution for Supporting Heterogeneous Multicast Groups
In this document, considerations are limited to provisioning
different service classes, but not different quality parameters
within a certain service class.
The proposed concept from section 3.1 provides a limited solution of the heterogeneity problem. Receivers are allowed to obtain a Limited Effort service without a reservation, so that at least two different Bless & Wehrle Informational [Page 15]
service classes within a multicast group are possible. Therefore, it is possible for any receiver to participate in the multicast session without getting any quality of service. This is useful if a receiver just wants to see whether the content of the multicast group is
interesting enough, before requesting a better service which must be paid for (like snooping into a group without prior reservation).
Alternatively, a receiver might not be able to receive this better
quality of service (e.g., because it is mobile and uses a wireless
link of limited capacity), but it may be satisfied with the reduced
quality, instead of getting no content at all.
Additionally, applying the RSVP concept of listening for PATH
messages before sending any RESV message is feasible again. Without using the proposed solution, this would have caused the NRS Problem. Theoretically, the proposed approach in section 7 also supports more than two different services within one multicast group, because the
additional field in the multicast routing table can store any DSCP
value. However, this would work only if PHBs can be ordered, so that the "best" PHB among different required PHBs downstream is chosen to be forwarded on a specific link. This is mainly a management issue
and is out of the scope of this document.
More advanced concepts may also support conditional re-marking in
dependence on the group address and DSCP value. This is useful if
the group uses different PHBs (e.g., for flows to different transport protocol ports) and the re-marking should thus additionally depend on the DSCP value of an incoming packet.
3.3. Solution for Any-Source Multicast
Every participant would have to initiate an explicit reservation to
ensure the possibility of sending to the group with a better service quality, regardless of whether other senders within the group already use the same service class simultaneously. This would require a
separate reservation for each sender-rooted multicast tree.
However, in the specific case of best-effort service (the default
PHB), it is nevertheless possible for participants to send packets to the group anytime without requiring any additional mechanisms. The
reason for this is that the first DS-capable boundary node will mark those packets with the DSCP of the default PHB because of a missing
traffic profile for this particular sender. The first DS capable
boundary nodes should therefore always classify multicast packets
based on both the sender’s address and the multicast group address. 4. Scalability Considerations
Bless & Wehrle Informational [Page 16]
The proposed solution does not add complexity to the DS architecture or to a DS node, nor does it change the scalability properties of
DiffServ. With current IP multicast routing protocols, a multicast
router has to manage and hold state information per traversing
multicast flow. The suggested solution scales to the same extent as IP multicast itself, because the proposed re-marking may occur per
branch of a multicast flow. This re-marking is logically associated with an addition to the multicast routing state that is required
anyway. In this respect, re-marking of packets for multicast flows
in interior nodes is not considered as a scalability problem or to be in contradiction to the DiffServ approach itself. It is important to distinguish the multicast case from existing justifiable scalability concerns relating to re-marking packets of unicast flows within
interior routers. Moreover, the decision of when to change a re-
marking policy is not performed by the router, but by some management entity at a time scale which is different from the time scale at the packet forwarding level.
5. Deployment Considerations
The solution proposed in section 3.1 can be deployed on most router
platforms available today. Architectures that perform routing and
forwarding functions in software could be updated by a new software
release.
However, there may be some specialized hardware platforms that are
currently not able to deploy the proposed solution from section 7.
This may be the case when a multicast packet is directly duplicated
on the backplane of the router, so that all outgoing interfaces read the packet in parallel. Consequently, the codepoint cannot be
changed for a subset of these outgoing interfaces and the NRS problem can not be solved directly in the branching point.
In this case, there exist several alternative solutions:
1. As mentioned in section 3.1, if traffic conditioning mechanisms can be applied on the outgoing packets at the individual output interfaces, a combination of classifier and marker may be used for each branch.
2. The change of the codepoint for subtrees without properly
allocated resources could take place in the following
downstream router. There, for every incoming packet of the
considered multicast group, the codepoint would be changed to
the value that the previous router should have set. If a LAN
(e.g., a high-speed switching LAN) is attached to the
considered outgoing interface, then on every router connected
to the LAN, packets of the considered group should be changed Bless & Wehrle Informational [Page 17]
on the incoming interface by standard DiffServ mechanisms.
Future releases of router architectures may support the change of the codepoint directly in the replication process as proposed in section 7.
6. Security Considerations
Basically, the security considerations in [1] apply. The proposed
solution does not imply new security aspects. If a join of arbitrary end-systems to a multicast group is not desired (thereby receiving a lower than best-effort quality) the application usually has to
exclude these participants. This can be accomplished by using
authentication, authorization, or ciphering techniques at the
application level -- like in traditional IP multicast scenarios.
Moreover, it is important to consider the security of corresponding
management mechanisms, because they are used to activate re-marking
of multicast flows. On the one hand, functions for instructing the
router to mark or re-mark packets of multicast flows are attractive
targets to perform theft of service attacks. On the other hand,
their security depends on the router management mechanisms which are used to realize this functionality. Router management should
generally be protected against unauthorized use, therefore preventing those attacks as well.
7. Implementation Model Example
One possibility of implementing the proposed solution from section
3.1 is described in the following. It has to be emphasized that
other realizations are also possible, and this description should not be understood as a restriction on potential implementations. The
benefit of the following described implementation is that it does not require any additional classification of multicast groups within an
aggregate. It serves as a proof of concept that no additional
complexity is necessary to implement the proposed general solution
described in section 3.
Because every multicast flow has to be considered by the multicast
routing process (in this context, this notion signifies the multicast forwarding part and not the multicast route calculation and
maintenance part, cf. Fig. 1), the addition of an extra byte in each multicast routing table entry containing the DS field, and thus its
DS codepoint value per output link (resp. virtual interface, see Fig.
8), results in nearly no additional cost. Packets will be replicated by the multicast forwarding process, so this is also the right place for setting the correct DSCP values of the replicated packets. Their DSCP values are not copied from the incoming original packet, but Bless & Wehrle Informational [Page 18]
from the additional DS field in the multicasting routing table entry for the corresponding output link (only the DSCP value must be
copied, while the two remaining bits are ignored and are present for simplification reasons only). This field initially contains the
codepoint of the LE PHB if incoming packets for this specific group
do not carry the codepoint of the default PHB.
When a packet arrives with the default PHB, the outgoing replicates
should also get the same codepoint in order to retain the behavior of current common multicast groups using the default PHB. A router
configuration message changes the DSCP values in the multicast
routing table and may also carry the new DSCP value which should be
set in the replicated packets. It should be noted that although re- marking may also be performed by interior nodes, the forwarding
performance will not be decreased, because the decision of when and
what to re-mark is made by the management (control plane).
Multicast Other List
Destination Fields of
Address virtual Inter- DS
interfaces face ID Field
+--------------------------------+ +-------------------+ | X | .... | *-------------------->| C | (DSCP,CU) | |--------------------------------| +-------------------+ | Y | .... | *-----------+ | D | (DSCP,CU) | |--------------------------------| | +-------------------+ | ... | .... | ... | |
. . . . | +-------------------+ . ... . .... . ... . +-------->| B | (DSCP,CU) | +--------------------------------+ +-------------------+ | ... | .... | ... | | D | (DSCP,CU) | +--------------------------------+ +-------------------+ | ... | ... | . . . . . . Figure 8: Multicast routing table with additional
fields for DSCP values
8. Proof of the Neglected Reservation Subtree Problem
In the following, it is shown that the NRS problem actually exists
and occurs in reality. Hence, the problem and its solution was
investigated using a standard Linux Kernel (v2.4.18) and the Linux-
based implementation KIDS [11].
Furthermore, the proposed solution for the NRS problem has been
implemented by enhancing the multicast routing table, as well as the Bless & Wehrle Informational [Page 19]
multicast routing behavior in the Linux kernel. In the following
section, the modifications are briefly described.
Additional measurements with the simulation model simulatedKIDS [12] will be presented in section 9. They show the effects of the NRS
problem in more detail and also the behavior of the BAs using or not using the Limited Effort PHB for re-marking.
8.1. Implementation of the Proposed Solution
As described in section 3.1, the proposed solution for avoiding the
NRS Problem is an extension of each routing table entry in every
Multicast router by one byte. In the Linux OS, the multicast routing table is implemented by the "Multicast Forwarding Cache (MFC)". The MFC is a hash table consisting of an "mfc-cache"-entry for each
combination of the following three parameters: sender’s IP address,
multicast group address, and incoming interface.
The routing information in a "mfc-cache"-entry is kept in an array of TTLs for each virtual interface. When the TTL is zero, a packet
matching to this "mfc-cache"-entry will not be forwarded on this
virtual interface. Otherwise, if the TTL is less than the packet’s
TTL, the latter will be forwarded on the interface with a decreased
TTL.
In order to set an appropriate codepoint if bandwidth is allocated on an outgoing link, we added a second array of bytes -- similar to the TTL array -- for specifying the codepoint that should be used on a
particular virtual interface. The first six bits of the byte contain the DSCP that should be used, and the seventh bit indicates whether
the original codepoint in the packet has to be changed to the
specified one (=0) or has to be left unchanged (=1). The default
entry of the codepoint byte is zero; so initially, all packets will
be re-marked to the default DSCP.
Furthermore, we modified the multicast forwarding code for
considering this information while replicating multicast packets. To change an "mfc-cache"-entry we implemented a daemon for exchanging
the control information with a management entity (e.g., a bandwidth
broker). Currently, the daemon uses a proprietary protocol, but
migration to the COPS protocol (RFC 2748) is planned.
Bless & Wehrle Informational [Page 20]
JOIN IN 学生用书1 Word List Starter Unit 1.Good afternoon 下午好 2.Good evening 晚上好 3.Good morning 早上好 4.Good night 晚安 5.Stand 站立 Unit 1 6.count [kaunt] （依次）点数 7.javascript:;eight [eit] 八 8.eleven [i'levn] 十一 9.four [f?:] 四 10.five [faiv] 五 11.flag [fl?g] 旗 12.guess [ges] 猜 13.jump [d??mp] 跳 14.nine [nain] 九 15.number ['n?mb?] 数字 16.one [w?n] 一 17.seven ['sevn] 七 18.six [siks] 六 19.ten [ten] 十 20.three [θri:] 三 21.twelve [twelv] 十二 22.two [tu:] 二 23.your [ju?] 你的 24.zero ['zi?r?u] 零、你们的 Unit 2 25.black [bl?k] 黑色26.blue [blu:] 蓝色 27.car [kɑ:] 小汽车 28.colour ['k?l?] 颜色 29.door [d?:] 门 30.favourite [feiv?rit]javascript:; 特别喜爱的 31.green [gri:n] 绿色 32.jeep [d?i:p] 吉普车 33.orange ['?:rind?] 橙黄色 34.pin k [pi?k] 粉红色 35.please [pli:z] 请 36.purple ['p?:pl] 紫色 37.red [red] 红色 38.white [wait] 白色 39.yellow ['jel?u] 黄色 Unit 3 40.blackboard ['bl?kb?:d] 黑板 41.book [buk] 书 42.chair [t???] 椅子 43.desk [desk] 桌子 44.pen [pen] 钢笔 45.pencil ['pensl] 铅笔 46.pencil case [keis] 笔盒 47.ruler ['ru:l?] 尺、直尺 48.schoolbag [sku:l] 书包 49.tree [tri:] 树 50.window ['wind?u] 窗、窗口 Unit 4 51.brown [braun] 棕色 52.cat [k?t] 猫
五年级英语测试卷 学校班级姓名 听力部分（共 20 分） 一、 Listen and colour.听数字，涂颜色。（5分） 1318403080 1420125015 二、 Listen and tick. 听录音，在相应的格子里打“√”。（6分） Play Swim Play the Ride a Roller Play foot Ski table ball piano horse blade tennis Tom Jimmy Iane 三、 Listen and number.听录音，标序号。（9分） pig fox lion cow
snake duck hippo wolf sheep 笔试部分（共 80 分） 一、 Write the questions.将完整的句子写在下面的横线上。(10 分) got it Has eyes on a farm it live sheep a it other animals eat it it Is 二、 Look and choose.看看它们是谁，将字母填入括号内。(8 分) A. B. C. D.
E. F.G.H. ( )pig( )fox( )sheep( ) cat ( ) snake( ) lion( ) mouse ( ) elephant 三、 Look at the pictures and write the questions.看图片，根据答语写出相应的问题。 (10 分) No,it doesn’t.
Yes,it is. Yes,it does. Yes,it has. Yes,it does. 四、 Choose the right answer. 选择正确的答案。 (18 分 ) 1、it live on a farm 2.it fly
Join In剑桥小学英语(改编版)入门阶段Unit 1Hello,hello第1单元嗨,嗨 and mime. 1 听,模仿 Stand up Say 'hello' Slap hands Sit down 站起来说"嗨" 拍手坐下来 Good. Let's do up Say 'hello' Slap hands Sit down 好. 我们来再做一遍.站起来说"嗨"拍手坐下来 the pictures. 2 再听一遍给图画编号. up "hello" hands down 1 站起来 2 说"嗨" 3 拍手 4 坐下来说 3. A ,what's yourname 3 一首歌嗨,你叫什么名字 Hello. , what's yourname Hello. Hello. 嗨. 嗨. 嗨, 你叫什么名字嗨,嗨. Hello, what's yourname I'm Toby. I'm Toby. Hello,hello,hello.嗨, 你叫什么名字我叫托比. 我叫托比 . 嗨,嗨,嗨. I'm Toby. I'm Toby. Hello,hello, let's go! 我是托比. 我是托比. 嗨,嗨, 我们一起! Hello. , what's yourname I'm 'm Toby. 嗨.嗨.嗨, 你叫什么名字我叫托比.我叫托比. Hello,hello,hello. I'm 'm Toby. Hello,hello,let's go! 嗨,嗨,嗨.我是托比. 我是托比. 嗨,嗨,我们一起! 4 Listen and stick 4 听和指 What's your name I'm Bob. 你叫什么名字我叫鲍勃. What's your name I'm Rita. What's your name I'm Nick. 你叫什么名字我叫丽塔. 你叫什么名字我叫尼克. What's your name I'm Lisa. 你叫什么名字我叫利萨. 5. A story-Pit'sskateboard. 5 一个故事-彼德的滑板. Pa:Hello,Pit. Pa:好,彼德. Pi:Hello,:What's this Pi:嗨,帕特.Pa:这是什么 Pi:My new :Look!Pi:Goodbye,Pat! Pi:这是我的新滑板.Pi:看!Pi:再见,帕特! Pa:Bye-bye,Pit!Pi:Help!Help!pi:Bye-bye,skateboard! Pa:再见,彼德!Pi:救命!救命!Pi:再见,滑板! Unit 16. Let's learnand act 第1单元6 我们来边学边表演.
四年级第一单元培优题 一、Basic words(基础单词): things in a room 1.桌子 2.椅子 3.窗户 4.图片 5.墙壁 6.时钟 7.手表 8.盒子 Verb 1.唱歌 2.开始开始 3.结束 phrases 1.起床 2.上学 3.做运动 4.吃午饭 5.做运动 6.睡觉 7.开始上课 8.结束上课 Adj. 1.快的 2.慢的 Time 1.分钟 2.小时 3.天 4.周 5.月 6.季节 7.年 二、Extensive words(拓展词汇): 1.墙壁 2. 疯狂的 3.strike 4.midnight 5.show 6.correct 7. 告诉 8.outside 三、Basic sentences: 1. What’s the time on your watch? It’s (12:30) 2. ?
It’s eight o’clock. 3. What time do you get up？ I get up 4. When do you have lunch? 5. When do classes begin? 6. When does school end? 7. How many minutes are there in an hour? There are 8. How many are there in a year? There are four. 9. ? There are seven days in a week. 10. What time is it by the black watch? (11:30) 四、Extensive sentences: 1. I have got a beautiful clock. But I think it is very . Because at one o’clock it strikes two. At two o’clock my crazy clock four. At ten o’clock it do a thing. But at midnight my clock to sing. 五、Passages: 基础篇 Hello! I’m Sophie. I’m ten years old. I’m from Australia. But now I live in
Join In剑桥小学英语(改编版)入门阶段 Unit 1Hello,hello第1单元嗨,嗨 1.Listen and mime. 1 听,模仿 Stand up Say 'hello' Slap hands Sit down 站起来说"嗨" 拍手坐下来 Good. Let's do itagain.Stand up Say 'hello' Slap hands Sit down 好. 我们来再做一遍.站起来说"嗨"拍手坐下来 2.listen again.Number the pictures. 2 再听一遍给图画编号. 1.Stand up 2.Say "hello" 3.Slap hands 4.Sit down 1 站起来 2 说"嗨" 3 拍手 4 坐下来说 3. A song.Hello,what's yourname? 3 一首歌嗨,你叫什么名字? Hello. Hello.Hello, what's yourname? Hello. Hello. 嗨. 嗨. 嗨, 你叫什么名字? 嗨,嗨. Hello, what's yourname? I'm Toby. I'm Toby. Hello,hello,hello. 嗨, 你叫什么名字? 我叫托比. 我叫托比 . 嗨,嗨,嗨. I'm Toby. I'm Toby. Hello,hello, let's go! 我是托比. 我是托比. 嗨,嗨, 我们一起! Hello. Hello.Hello, what's yourname? I'm Toby.I'm Toby. 嗨.嗨.嗨, 你叫什么名字? 我叫托比.我叫托比. Hello,hello,hello. I'm Toby.I'm Toby. Hello,hello,let's go! 嗨,嗨,嗨.我是托比. 我是托比. 嗨,嗨,我们一起! 4 Listen and stick 4 听和指 What's your name? I'm Bob. 你叫什么名字? 我叫鲍勃. What's your name ? I'm Rita. What's your name ? I'm Nick. 你叫什么名字? 我叫丽塔. 你叫什么名字? 我叫尼克. What's your name ? I'm Lisa. 你叫什么名字? 我叫利萨. 5. A story-Pit'sskateboard. 5 一个故事-彼德的滑板. Pa:Hello,Pit. Pa:好,彼德. Pi:Hello,Pat.Pa:What's this? Pi:嗨,帕特.Pa:这是什么? Pi:My new skateboard.Pi:Look!Pi:Goodbye,Pat! Pi:这是我的新滑板.Pi:看!Pi:再见,帕特! Pa:Bye-bye,Pit!Pi:Help!Help!pi:Bye-bye,skateboard! Pa:再见,彼德!Pi:救命!救命!Pi:再见,滑板! Unit 16. Let's learnand act 第1单元6 我们来边学边表演.
Join in 小学五年级英语教案 介休市宋古二中上站小学庞汝君 Unit 6 Friends 单元目标： 1、单词：sport music kite cap car book dog cat rat frog spider butterfly 2、句型：Who is your best friend ? （重点） How old is he ? When is his birthday ? What’s his favourite food ? 3、段落：介绍自己的好朋友 My best friend’s name is Toby . He is ten years old . His favourite colour is red . His birthday is in May . He has got a dog . 4、语法：第三人称的人称代词和物主代词（难点） 他he 他的his 她she 她的her 一般现在时第三人称单数动词+s
5、故事：Emma , Jackie and Diana . Are you all right ? What’s the matter ? Don’t be silly . We can play together . The first class 一、教学目标： 两个句型1、Who is your best friend ? 2、How old is he ? 二、教学过程： 1、Talk about your best friend . （1）教师说句子Who is your best friend ? My best friend is Anna. 让学生先领会句子的意思，然后模仿， 小组练习对话并上台表演。 （2）第二个句子How old is he ? He is nine years old . 象上面一样练习，等到学生掌握后把两个问句连起来做 问答操练。
五 年 级 英 语 测 试 卷 学校 班级 姓名 听力部分（共20分） 一、Listen and colour . 听数字，涂颜色。（5分） 二、Listen and tick .听录音，在相应的格子里打“√”。（6分）
三、Listen and number.听录音，标序号。（9分） pig fox lion cow snake duck hippo wolf sheep 笔试部分（共80分） 一、Write the questions.将完整的句子写在下面的横线上。(10分) 1.two got it Has eyes?
2.Does on a farm ? it live 3.Is sheep? a it 4.Does other animals? eat it 5.blue? it Is 二、Look and choose.看看它们是谁，将字母填入括号内。(8分)
A. B. C. D. E. F. G. H. ( ) pig ( ) fox ( ) sheep ( ) cat ( ) snake ( ) lion ( ) mouse ( ) elephant 三、Look at the pictures and write the questions.看图片，根据答语写出相应的问题。(10分)
？No,it doesn’t. ？Yes,it is. ？Yes,it does.
？Yes,it has. ？Yes,it does. 四、Choose the right answer.选择正确的答案。(18分) 1、it live on a farm? A.Do B.Has C.Does
五年级下英语月考试卷-全能练考-Join in剑桥英语 姓名：日期：总分：100 一、根据意思，写出单词。（10′） Fanny:Jackie, ________[猜] my animal,my ________最喜欢的 animal.OK? Jackie:Ok!Mm…Has it got a nose? Fanny:Yes,it’s got a big long nose,…and two long ________[牙齿]. Jackie:Does it live in ________[美国]? Fanny:No,no.It lives ________[在] Africa and Asia. Jackie:Can it ________[飞]? Fanny:I’m sorry it can’t. Jackie:Is it big? Fanny:Yes,it’s very big and ________[重的]. Jackie:What ________[颜色] is it?Is it white or ________[黑色]? Fanny:It’s white. Jackie:Oh,I see.It’s ________[大象]. 二、找出不同类的单词。（10′） （）1 A.sofa B.table C.check （）2 A.noodle https://www.doczj.com/doc/84374640.html,k C.way （）3 A.fish B.wolf C.lion （）4 A.bike B.car C.write （）5 A.tree B.farm C.grass （）6 A.big B.small C.other ( ）7 A.eat B.listen C.brown
公司登记（备案）申请书 注：请仔细阅读本申请书《填写说明》，按要求填写。 □基本信息 名称 名称预先核准文号/ 注册号/统一 社会信用代码 住所 省（市/自治区）市（地区/盟/自治州）县（自治县/旗/自治旗/市/区）乡（民族乡/镇/街道）村（路/社区）号 生产经营地 省（市/自治区）市（地区/盟/自治州）县（自治县/旗/自治旗/市/区）乡（民族乡/镇/街道）村（路/社区）号 联系电话邮政编码 □设立 法定代表人 姓名 职务□董事长□执行董事□经理注册资本万元公司类型 设立方式 （股份公司填写） □发起设立□募集设立经营范围 经营期限□年□长期申请执照副本数量个
□变更 变更项目原登记内容申请变更登记内容 □备案 分公司 □增设□注销名称 注册号/统一 社会信用代码登记机关登记日期 清算组 成员 负责人联系电话 其他□董事□监事□经理□章程□章程修正案□财务负责人□联络员 □申请人声明 本公司依照《公司法》、《公司登记管理条例》相关规定申请登记、备案，提交材料真实有效。通过联络员登录企业信用信息公示系统向登记机关报送、向社会公示的企业信息为本企业提供、发布的信息，信息真实、有效。 法定代表人签字：公司盖章（清算组负责人）签字：年月日
附表1 法定代表人信息 姓名固定电话 移动电话电子邮箱 身份证件类型身份证件号码 （身份证件复印件粘贴处） 法定代表人签字：年月日
附表2 董事、监事、经理信息 姓名职务身份证件类型身份证件号码_______________ （身份证件复印件粘贴处） 姓名职务身份证件类型身份证件号码_______________ （身份证件复印件粘贴处） 姓名职务身份证件类型身份证件号码_______________ （身份证件复印件粘贴处）
小学三年级英语（上册）重要知识点归纳 一、单词 Unit 1学习文具：pen (钢笔) pencil (铅笔) pencil-case ( 铅笔盒) ruler(尺子) eraser(橡皮) crayon (蜡笔) book (书) bag (书包) sharpener (卷笔刀) school (学校) Unit 2身体部位：head (头) face( 脸) nose (鼻子) mouth (嘴) eye (眼睛)leg (腿) ear (耳朵) arm (胳膊)finger (手指) leg (腿) foot (脚)body (身体) Unit 3颜色：red (红色的) yellow (黄色的)green (绿色的)blue (蓝色的) purple (紫色的) white (白色的) black (黑色的) orange (橙色的) pink (粉色的)brown (棕色的) Unit 4动物：cat (猫)dog (狗)monkey (猴子)panda (熊猫)rabbit( 兔子) duck (鸭子)pig (猪)bird (鸟) bear (熊)elephant (大象)mouse (老鼠) squirrel (松鼠) Unit 5食物：cake (蛋糕)bread (面包) hot dog (热狗) hamburger (汉堡包) chicken (鸡肉)French fries (炸薯条)coke (可乐)juice (果汁)milk (牛奶) water (水)tea (茶) coffee (咖啡) Unit 6数字：one (一) two (二) three (三)four (四) five (五)six( 六)seven (七) eight (八) nine( 九) ten( 十)doll (玩具娃娃) boat (小船)ball (球) kite (风筝) balloon (气球) car (小汽车)plane (飞机) 二、对话 1、向别人问好应该说――A: Hello! (你好!) B: Hi! (你好!) 2、问别人的名字应该说-――A：What's your name? 你的名字是什么? B：My name's Chen Jie. 我的名字是陈洁。 3、跟别人分手应该说――A: Bye.\ Good bye!(再见) B: See you.(再见) \ Goodbye.(再见) 4、A: I have a pencil\ bag\ruler 我有一只铅笔\书包\尺子。 B: Me too . 我也有。 5、早上相见应该说-――A: Good morning. 早上好!
有限合伙企业登记注册操作指南 风险控制部 20xx年x月xx日
目录 一、合伙企业的概念 (4) 二、有限合伙企业应具备的条件 (4) 三、有限合伙企业设立具备的条件 (4) 四、注册有限合伙企业程序 (5) 五、申请合伙企业登记注册应提交文件、证件 (6) （一）合伙企业设立登记应提交的文件、证件： (6) （二）合伙企业变更登记应提交的文件、证件： (7) （三）合伙企业注销登记应提交的文件、证件： (8) （四）合伙企业申请备案应提交的文件、证件： (9) （五）其他登记应提交的文件、证件： (9) 六、申请合伙企业分支机构登记注册应提交的文件、证件 (9) （一）合伙企业分支机构设立登记应提交的文件、证件 (10) （二）合伙企业分支机构变更登记应提交的文件、证件： (10) （三）合伙企业分支机构注销登记应提交的文件、证件： (11) （四）其他登记应提交的文件、证件： (12) 七、收费标准 (12) 八、办事流程图 (12) （一）有限合伙企业创办总体流程图（不含专业性前置审批） (12) （二）、工商局注册程序 (15)
（三）、工商局具体办理程序（引入网上预审核、电话预约方式） (16) 九、有限合伙企业与有限责任公司的区别 (16) （一）、设立依据 (16) （二）、出资人数 (16) （三）、出资方式 (17) （四）、注册资本 (17) （五）、组织机构 (18) （六）、出资流转 (18) （七）、对外投资 (19) （八）、税收缴纳 (20) （九）、利润分配 (20) （十）、债务承担 (21) 十、常见问题解答与指导 (21)
JOIN IN英语三年级下册课本重点Start unit 1 Words morning afternoon evening night 2 Sentences Good morning !早上好 Good afternoon !下午好 Good evening!晚上好 Good night!晚安 3 Phrases clap your hands 拍拍手 jump up high 往高跳 shake your arms and your legs 晃动你的胳膊和腿 bend your knees 弯曲你的膝盖 touch your toes 摸摸你的脚指
stand nose to nose 鼻子对鼻子站着 Unit 1 Pets 1 Words cat猫dog狗bird 鸟mouse老鼠fish鱼rabbit 兔子frog青蛙hamster仓鼠 budgie鹦鹉tiger老虎monkey 猴子panda熊猫giraffe 长颈鹿elephant 大象bear 熊run跑sit坐fly飞swim游泳roar吼叫eat吃 2 Grammar ★名词的复数:一般在词尾直接加s,不规则变化要牢记: fish-----fish mouse------mice 3 Sentences 1.Have you got a pet ? 你有宠物吗?Yes ,I have. 是的,我有。/No, I haven’t. 不,我没有。 2.2. What have you got ? 你有什么宠物吗?I’ve got a dog . / A dog. 我有一只狗。 3.What colour is the cat ? 你的猫是什么颜色的?It’s black. 它是黑色的。 What iswizard’s pet? 巫师的宠物是什么? 4.What is it ? 它是什么? It’s a rabbit .它是只兔子。
→客户提供：场所证明租赁协议身份证委托书三张一寸相片 →需准备材料：办理税务登记证时需要会计师资格证与财务人员劳动合同 →提交名称预审通知书→公司法定代表人签署的《公司设立登记申请书》→全体股东签署的《指定代表或者公共委托代理人的证明》（申请人填写股东姓名）→全体股东签署的公司章程（需得到工商局办事人员的认可）→股东身份证复印件→验资报告（需到计师事务所办理：需要材料有名称预审通知书复印件公司章程股东身份证复印件银行开具验资账户进账单原件银行开具询证函租赁合同及场所证明法人身份证原件公司开设临时存款账户的复印件）→任职文件（法人任职文件及股东董事会决议）→住所证明（房屋租赁合同）→工商局（办证大厅）提交所有材料→公司营业执照办理结束 →需带材料→公司营业执照正副本原件及复印件→法人身份证原件→代理人身份证→公章→办理人开具银行收据交款元工本费→填写申请书→组织机构代码证办
理结束 →需带材料→工商营业执照正副本复印件原件→组织机构正副本原件及复印件→公章→公司法定代表人签署的《公司设立登记申请书》→公司章程→股东注册资金情况表→验资报告书复印件→场所证明（租赁合同）→法人身份证复印件原件→会计师资格证（劳动合同）→税务登记证办理结束 →需带材料→工商营业执照正副本复印件原件→组织机构正副本原件及复印件→税务登记证原件及复印件→公章→法人身份证原件及复印件→代理人身份证原件及复印件→法人私章→公司验资账户→注以上复印件需四份→办理时间个工作日→办理结束 →需带材料→工商营业执照正副本复印件原件→组织机构正副本原件及复印件→公章→公司法定代表人签署的《公司设立登记申请书》→公司章程→股东注册资金情况表→验资报告书复印件→场所证明（租赁合同）→法人身份证复印件原件→会计师资格证（劳动合同）→会计制度→银行办理的开户许可证复印件→税务登记证备案办理结束
《剑桥小学英语Join In ——Book 3 下学期》教材教法分析2012-03-12 18:50:43| 分类：JOIN IN 教案| 标签：|字号大中小订阅. 一、学情分析： 作为毕业班的学生，六年级的孩子在英语学习上具有非常显著的特点： 1、因为教材的编排体系和课时不足，某些知识学生已遗忘，知识回生的现象很突出。 2、有的学生因受学习习惯及学习能力的制约，有些知识掌握较差，学生学习个体的差异性，学习情况参差不齐、两级分化的情况明显，对英语感兴趣的孩子很喜欢英语，不喜欢英语的孩子很难学进去了。 3、六年级的孩子已经进入青春前期，他们跟三、四、五年级的孩子相比已经有了很大的不同。他们自尊心强，好胜心强，集体荣誉感也强，有自己的评判标准和思想，对知识的学习趋于理性化，更有自主学习的欲望和探索的要求。 六年级学生在英语学习上的两极分化已经给教师的教学带来很大的挑战，在教学中教师要注意引导学生调整学习方式： 1、注重培养学生自主学习的态度 如何抓住学习课堂上的学习注意力，吸引他们的视线，保持他们高涨的学习激情，注重过程的趣味化和学习内容的简易化。 2、给予学生独立思考的空间。 3、鼓励学生坚持课前预习、课后复习的好习惯。 六年级教材中的单词、句子量比较多，难点也比较多，学生课前回家预习，不懂的地方查英汉词典或者其它资料，上课可以达到事半功倍的效果，课后复习也可以很好的消化课堂上的内容。 4、注意培养学生合作学习的习惯。 5、重在培养学生探究的能力：学习内容以问题的方式呈现、留给学生更多的发展空间。 二、教材分析： （一）.教材特点： 1．以学生为主体，全面提高学生的素质。
Starter Unit Good to see you again知识总结 一. 短语 1. dance with me 和我一起跳舞 2. sing with me 和我一起唱歌 3. clap your hands 拍拍你的手 4. jump up high 高高跳起 5.shake your arms and your legs晃晃你的胳膊和腿 6. bend your knees 弯曲你的膝盖 7. touch your toes 触摸你的脚趾8. stand nose to nose鼻子贴鼻子站 二. 句子 1. ---Good morning. 早上好。 ---Good morning, Mr Li. 早上好，李老师。 2. ---Good afternoon. 下午好。 ---Good afternoon, Mr Brown. 下午好，布朗先生。 3. ---Good evening，Lisa. 晚上好,丽莎。 ---Good evening, Bob. 晚上好，鲍勃。 4. ---Good night. 晚安。 ----Good night. 晚安。 5. ---What’s your name? 你叫什么名字？ ---I’m Bob./ My name is Bob. 我叫鲍勃。 6. ---Open the window, please. 请打开窗户。 ---Yes ,Miss. 好的，老师。 7. ---What colour is it? 它是什么颜色？ 它是蓝红白混合的。 ---It’s blue, red and white. 皮特的桌子上是什么？ 8. ---What’s on Pit’s table? ---A schoolbag, an eraser and two books. 一个书包，一个橡皮和两本书。 9. ---What time is it? 几点钟？ 两点钟。 ---It’s two. 10.---What’s this? 这是什么？ ---My guitar. 我的吉他。
JOIN IN英语三年级下册 Start unit 1 Words morning afternoon evening night 2 Sentences Good morning !早上好Good afternoon ！下午好Good evening！晚上好 Good night！晚安 3 Phrases clap your hands 拍拍手 jump up high 往高跳 shake your arms and your legs 晃动你的胳膊和腿 bend your knees 弯曲你的膝盖 touch your toes 摸摸你的脚指 stand nose to nose 鼻子对鼻子站着 Unit 1 Pets 1 Words cat猫dog狗bird 鸟mouse老鼠fish鱼rabbit 兔子frog青蛙hamster仓鼠 budgie鹦鹉tiger老虎monkey 猴子panda熊猫giraffe 长颈鹿elephant 大象bear 熊run跑sit坐fly飞swim游泳roar吼叫eat吃 2 Grammar
★名词的复数：一般在词尾直接加s,不规则变化要牢记: fish-----fish mouse------mice 3 Sentences 1.Have you got a pet ? 你有宠物吗？ Yes ,I have. 是的,我有。/No, I haven’t. 不，我没有。 2.What have you got ? 你有什么宠物吗？I’ve got a dog . / A dog. 我有一只狗。 3.What colour is the cat ? 你的猫是什么颜色的？It’s black. 它是黑色的。 What is wizard’s pet? 巫师的宠物是什么？ 4.What is it ? 它是什么? It’s a rabbit .它是只兔子。 5.How many budgies /mice are there? 这里有多少只鹦鹉/老鼠？ There are + 数字budgies/mice. 这里有------只鹦鹉/老鼠。 6.Fly like a budgie. 像鹦鹉一样飞。Run like a rabbit. 像兔子一样跑。 Swim like a fish. 像鱼一样游泳。Eat like a hamster. 像仓鼠一样吃东西。 Sit like a dog. 像狗一样坐。Roar like a tiger. 像老虎一样吼叫。 7.What are in the pictures. 图片里面是什么？Animals. 动物。 8. What animals? 什么动物？ 9.How many pandas (elephants /bears/ giraffes/ monkeys/ budgies) are there?有多少.？ How many + 可数名词的复数形式 Unit 2 The days of the week
2011-2012 学年度上学期六年级复习题（Unit2-Unit3 ） 一、听力部分 1、听录音排序 ( ) () ()() () 2、听录音，找出与你所听到的单词属同一类的单词 （） 1. A. spaceman B. pond C . tiger （） 2. A.mascots B. potato C . jeans （） 3. A. door B. behind C . golden （） 4. A. sometimes B. shop C . prince （） 5. A. chair B. who C . sell 3、听录音，将下面人物与他的梦连线 Sarah Tim Juliet Jenny Peter 4、听短文，请在属于Mr. Brown的物品下面打√ ( ) ( ) ( ) ( ) ( ) ( ) ( ) 5、听问句选答句 （） 1. A. Yes, I am B. Yes, I have C . Yes, you do （） 2. A.Pink B. A friendship band C . Yes. （） 3. A. OK B. Bye-bye. C . Thanks, too. （） 4. A. Monday. B. Some juice. C . Kitty. （） 5. A. I ’ve got a shookbag. B. I ’m a student. C . It has got a round face. 6、听短文，选择正确答案 （） 1. Where is Xiaoqing from? She is from . A.Hebei B. Hubei C . Hunan （） 2. She goes to school at . A.7:00 B.7:30 C . 7:15 （） 3. How many classes in the afternoon? classes. A. four B. three C . two （） 4. Where is Xiaoqing at twelve o ’clock? She is . A. at home B. at school C .in the park （） 5. What does she do from seven to half past eight? She . A.watches TV B. reads the book C. does homework
Join in三年级上册知识点 1.见面打招呼 Hello! = Hi! 你好 Good morning! 早上好！ Good afternoon! 下午好！ Good evening! 晚上好！ (注意：Good night的意思是“晚安”) 2.询问身体健康状况 How are you? 你好吗？ I’m fine. = I’m OK.我很好。 3.临走分别 Goodbye. = Bye bye. 再见。 See you tomorrow. 明天见。 4.Miss小姐Mr先生 5.询问名字 -What’s your name? 你叫什么名字？ -I’m Toby. = My name is Toby. = Toby.我叫托比。 6.Let’s+动词原形 如Let’s go! 我们走吧！ Let’s begin! 我们开始吧！ 7. Are you ready? 你准备好了吗？ I’m ready. 我准备好了。 8.十二个动词 look看listen听mime比划着表达speak讲read读write写draw画colour涂sing唱think想guess猜play玩9.询问物体 -What’s this? 这是什么？ -It’s my dog. / It’s a dog. / My dog. 这是我的狗。 10.my/your+名词 如my apple我的苹果 your apple你的苹果 11.数字0-10 zero零one一two二three三four四five五six六seven七eight八nine九ten十12.询问电话号码 -What’s your phone number? 你的电话号码是多少？ -It’s . / . 13.guess sth 猜东西 如Guess the number. 猜数字 14. What’s in the box? 盒子里有什么？ 15.询问数量 -How many? 多少？ -Nine. 九个。 16. Here is / are sth. 这是……
It Is Necessary To Clarify The Rights And Obligations Of The Parties, To Restrict Parties, And To Supervise Both Parties To Keep Their Promises And To Restrain The Act Of Reckless Repentance. 编订：XXXXXXXX 20XX年XX月XX日 代理公司注册登记协议书 简易版
代理公司注册登记协议书简易版 温馨提示：本协议文件应用在明确协议各方的权利与义务、并具有约束力和可作为凭证，且对当事人双方或者多方都有约制性，能实现监督双方信守诺言、约束轻率反悔的行为。文档下载完成后可以直接编辑，请根据自己的需求进行套用。 代理公司注册登记协议书 甲方：_________ 地址：_________ 电话：_________ 联系人：_________ 乙方：_________ 地址：_________ 电话：_________ 联系人：_________ 为了充分发挥_________的资源和信息服务优势，甲、乙双方经过友好协商，本着平等互利、友好合作的意愿达成本协议书，并郑重声
明共同遵守： 一、甲方同意按照本协议的规定，授权乙方为其代办公司注册手续。 二、乙方提供的代办咨询服务范围仅限如下： 1.为甲方代办工商营业执照、组织机构代码证、税务证、三章(法人章、公章、财务章); 2.约定的其他服务： _________。 三、甲方的责任： 1.甲方应指定专人配合乙方完成新企业工商登记注册等事务，并提供齐全的证件和规范的法律文件资料。 2.甲方对提供的证件和法律文件资料的真实性、正确性、合法性承担全部责任。
外研社剑桥小学英语Join_in四年级上册整体课时教案Starter Unit Let's begin 第一学时: The pupils learn to understand: How are you today? I’m fine/OK. Goodbye. The pupils learn to use: What’s your name? I’m (Alice). How are you? I’m fine. I’m OK. Activities and skills: Decoding meaning from teacher input. Using phrases for interaction in class. Greeting each other. I Introduce oneself. Asking someone’s mane. Teaching process: Step 1: Warm—up. Sing a song. Hello, what’s your name? Step 2: Presentation. 1. What’s your name? I’m…. (1) The teacher introduces herself, saying: Hello, /Good morning, I’m Miss Sun. (2) Asks a volunteer’s name:
What’s your name? The teacher prompt the pupil by whispering, I’m (Alice). (3) Asks all the pupils the same question and help those who need it by whispering I’m…. 2. How are you today? I’m fine. I’m OK. (1) The teacher explains the meaning of How are you today? (2) Tell the class to ask the question all together and introduce two answers, I’m (not very) fine/I’m Ok. (3) Asks all the pupils the same question and make sure that all the students can reply. Step3: Speak English in class. 1. Tells the pupils to open their books at page3, look at the four photographs, and listen to the tape. 2. Asks the pupils to dramatise the situations depicted in the four photographs. A volunteer will play the part of the parts of the other pupils, answering as a group. 第二学时: The pupils learn to use these new words: Sandwich, hamburger, hot dog, puller, cowboy, jeans, cinema, walkman, snack bar, Taxi, clown, superstar.