One document matched: draft-ietf-nsis-applicability-mobility-signaling-10.xml
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<front>
<title abbrev="NSIS Signaling in Mobility">Applicability Statement of NSIS Protocols in Mobile Environments</title>
<author initials='T.' surname="Sanda (Ed.)" fullname='Takako Sanda'>
<organization abbrev="Panasonic">
Matsushita Electric Industrial Co., Ltd. (Panasonic)
</organization>
<address>
<postal>
<street>5-3, Hikarino-oka, Yokosuka City</street>
<city>Kanagawa</city>
<code>239-0847</code>
<country>Japan</country>
</postal>
<phone>+81 50 3687 6563</phone>
<email>sanda.takako@jp.panasonic.com</email>
</address>
</author>
<author initials='X.' surname="Fu" fullname='Xiaoming Fu'>
<organization abbrev="University of Goettingen">
Computer Networks Group, University of Goettingen
</organization>
<address>
<postal>
<street>Lotzestr. 16-18</street> <city>Goettingen</city>
<code>37083</code>
<country>Germany</country>
</postal>
<!-- phone, unknown -->
<email>fu@cs.uni-goettingen.de</email>
</address>
</author>
<author initials='S.' surname="Jeong" fullname='Seong-Ho Jeong'>
<organization abbrev="HUFS">
Hankuk University of FS
</organization>
<address>
<postal>
<street>89 Wangsan Mohyun</street> <city>Yongin-si, Gyeonggi-do</city>
<code>449-791</code>
<country>Korea</country>
</postal>
<phone>+82 31 330 4642</phone>
<email>shjeong@hufs.ac.kr</email>
</address>
</author>
<author initials='J.' surname="Manner" fullname='Jukka Manner'>
<organization abbrev="Univ. of Helsinki">
Department of Computer Science University of Helsinki
</organization>
<address>
<postal>
<street>P.O. Box 26 (Teollisuuskatu 23)</street> <city>HELSINKI</city>
<code>FIN-00014</code>
<country>Finland</country>
</postal>
<phone>+358-9-191-44210</phone>
<email>jmanner@cs.helsinki.fi</email>
</address>
</author>
<author initials='H.' surname="Tschofenig" fullname='Hannes Tschofenig'>
<organization abbrev="Nokia Siemens Networks">
Nokia Siemens Networks
</organization>
<address>
<postal>
<street>Otto-Hahn-Ring 6</street>
<street>Munich</street>
<code>81739</code>
<country>Germany</country>
</postal>
<!-- phone, unknown -->
<email>Hannes.Tschofenig@nsn.com</email>
</address>
</author>
<date month="July" year="2008"/>
<area>Transport</area>
<workgroup>Next Steps in Signaling (nsis)</workgroup>
<abstract>
<t> Mobility of an IP-based node affects routing paths, and as a result, can have a significant effect on the protocol operation and state management. This draft discusses the effects mobility can cause to the NSIS protocol suite, and how the protocols operate in different scenarios, with mobility management protocols. </t>
</abstract>
</front>
<middle>
<!-- Start of L1 section --> <section title="Introduction">
<t> Mobility of IP-based nodes incurs route changes,
usually at the edge of the network.
Since IP addresses are usually part of flow
identifiers, the change of IP addresses implies the
change of flow identifiers (i.e., the GIST message routing information or MRI <xref target ="nsis.gist" />). Local mobility usually
does not cause the change of the global IP addresses,
but affects the routing paths within the local access
network</t>
<t> The NSIS protocol suite consists of two layers: NSIS Transport Layer Protocol (NTLP) and the NSIS Signaling Layer Protocol
(NSLP). The General Internet Signaling Transport (GIST) <xref target
="nsis.gist" /> implements the NTLP, which is a signaling
application independent protocol and transports service-related
information between neighboring GIST nodes. Each specific service
has its own NSLP protocol; currently there two standardized NSLP
protocols, the QoS NSLP <xref target ="nsis.qosnslp" />, and the
NAT/Firewall NSLP <xref target ="nsis.natfwnslp" /></t>
<t>The goals of this draft are to present the effects of mobility on the
NTLP/NSLPs and to provide guides on how such NSIS protocols work in
basic mobility scenarios, including support for Mobile IPv4 and
Mobile IPv6 scenarios. We also show how these protocols fulfil
the requirements regarding mobility set forth in <xref target="rfc3726.req4sig" />. In general,
the NSIS protocols work well in mobile environments. The efficiency of
NSIS signaling is primarily an issue of software engineering, e.g.,
which way an implementer chooses when implementing the protocol functions, and how the coupling of the
mobility management protocols and the NSIS stack is implemented.
</t>
<t>
The Session ID (SID) used in NSIS signaling enables the separation of the signaling state and the IP addresses of the communicating hosts. This makes it possible to directly update a signaling state in the network due to mobility without being forced to first remove the old state and then re-establish a new one. This is the fundamental reason why NSIS signaling works well in mobile environments.
</t>
<t>
A further important issue is that NSLPs must be aware of mobility, i.e., routing and IP address changes. GIST has no semantics of an end-to-end signaling session, only NSLPs have. Moreover, the Session ID is effectively an NSLP layer concept.
</t>
<t>
This draft focuses on basic mobility scenarios. Key management
related to handovers, multihoming and interactions between NSIS and other
mobility management protocols than Mobile IP are out of scope of this
document. Also, practical implementations typically need various APIs across components within a node. API issues, e.g., APIs from GIST to the various mobility and routing schemes, are also out of scope of this work. The generic GIST API towards NSLP is flexible enough to fulfill most mobility-related needs of the NSLP layer.</t>
</section> <!-- End of L1 section -->
<!-- End of Introduction -->
<!-- Start of L1 section --> <section title="Requirements Notation and Terminology" anchor="Terminology">
<!-- Editing memo: need to be re-written -->
<!--
<t> 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 <xref target="refs.RFC2119">RFC2119</xref>.</t>
-->
<t>The terminology in this draft is based on <xref target ="nsis.gist" /> and <xref target ="rfc3753.mobterm" />. In addition, the following terms are used. Note that in this draft, a generic route change caused by regular IP routing is referred to as a 'route change', and the route change caused by mobility is referred to as 'mobility'.</t>
<t>(1) Downstream </t>
<t>The direction from a data sender towards the data receiver.</t>
<t>(2) Upstream</t>
<t>The direction from a data receiver towards the data sender.</t>
<t>(3) Crossover Node (CRN)</t>
<t>A Crossover Node is a node that for a given function is a merging point of two or more paths belong to flows of the same session along which states are installed. </t>
<t>In the mobility scenarios, there are two different types of merging points in the network according to the direction of signaling flows followed by data flows as shown in <xref target="fig.Top.NSIS.sig.caused.mob" /> of <xref target="Localized.signaling.scenario" />, where we assume that the MN is the data sender.
<list>
<t>Upstream CRN (UCRN): the node closest to the data sender from which the state information in the direction from data receiver to data sender begins to diverge after a handover.</t>
<t>Downstream CRN (DCRN): the node closest to the data sender from which the state information in the direction from the data sender to the data receiver begins to converge after a handover.</t>
</list><!--End of List-->
</t>
<t>In general, the DCRN and the UCRN may be different due to the asymmetric characteristics of routing although the data receiver is the same.</t>
<t>(4) State Update</t>
<t>State Update is the procedure for the re-establishment of NSIS state on the new path, the teardown of NSIS state on the old path, and the update of NSIS state on the common path due to the mobility. The State Update procedure is used to address mobility for the affected flows.
<list>
<t>Upstream State Update: State Update for the upstream signaling flow.</t>
<t>Downstream State Update: State Update for the downstream signaling flow.</t>
</list>
</t>
<!--
<t>If a route change happens without any change of the flow identifier, State update on the common path is not required because the flow identifiers do not change. Especially, in mobility scenarios, if the NSIS signaling interacts with local mobility management (LMM) protocols (e.g., HMIPv6), the State Update can be localized within the access network. In this case, setup delay of NSIS signaling can be minimized.</t>
-->
</section> <!-- End of L1 section -->
<!-- End of Terminology -->
<!-- Start of L1 section --> <section title="Challenges with Mobility" anchor="Problem.Statement">
<t>IP mobility in its simplest form only includes route changes. This section identifies problems caused by mobility, which affect the operations of NSIS protocol suite. </t>
<t>1. Change of route and possibly change of the MN's IP address </t>
<t>Topology changes or network reconfiguration might lead to
path changes for data packets sent to or from the MN and can cause an IP
address change of the MN. When an IP address changes due to mobility,
information within the
path-coupled MRI is affected (the source or destination address).
Consequently, this concerns GIST as well as NSLPs, e.g., the packet
classifier in QoS NSLP or some rules carried in NAT/FW NSLP. So already
installed firewall rules, NAT bindings, and QoS reservations may become
invalid, because the installed states refer to a non-existent flow. If
the affected nodes are also on the new path, this information must be
updated accordingly.
</t>
<!--
<t>NSIS solution: The NSIS suite decouples state and flow identification. A state is stored and referred to by the Session ID (SID). Flows associated with a given NSLP state are defined by the Message Routing Information (MRI). GIST notifies when a routing path associated with a SID changes, and provides a notification to the NSLP. It is then up to the NSLP to update the state information in the network. Thus, the effect is an update to the states, not a full new request. This decoupling effectively solves also a typical problem with certain signaling protocols, where protocol state is identified with flow endpoints, and when a flow endpoint changes, the whole session state becomes invalid. </t>
-->
<t>2. Double state problem </t>
<t>After a handover, packets may end up getting delivered through a new path. Since the
state on the old path still remains as it was after re-establishing
the state along the new path, we have two separates states for the
same signaling session. Although the state on the old path will be
deleted automatically based on the soft state timeout, the state
timer value may be quite long (e.g., 90s as a default value). With
the QoS NSLP, this problem might result in the waste of resources and
lead to failure of admitting new reservations (due to lack of
resources). With the NAT/FW NSLP, it is still possible to re-use
this installed state although an MN roams to a new location;
this means that another host can send data through a firewall without
any prior NAT/FW NSLP signaling because the previous state
does not yet expire. </t>
<!--
<t>NSIS solution: Removing old state in the network is a functionality of each NSLP independently. The QoS NSLP solves this through the use of the Reservation Sequence Number (RSN). The RSN makes it possible to identify new updated information related to a resource reservation. A QNE that is CRN for a given reservation is able to tear down an old reservation, and install a new reservation on the new path. More details can be found in the QoS NSLP specification. [WHAT DOES THE NAT/FW DO?] </t>
-->
<t> 3. End-to-end signaling and frequency of route changes </t>
<t>The change of route and IP addresses in mobile environments is
typically much faster and more frequent than traditional route
changes caused by node or link failure. This may result in a need to
speed up the update procedure of NSLP states. If the MRI
changes, the signaling session will be invalid.
</t>
<!--
<t>NSIS solution: If the MRI does not change due to handovers, the NSIS protocols are able to localize the update to only the new path. One of the NSIS nodes on the path is a merging point of the old and new routing paths, and is able to confine the signaling to only the affect path. Thus, no end-to-end signaling is needed. If the MRI changes, end-to-end signaling will happen since all the nodes on the path must be provided with an updated flow identification (MRI); the SID does not change. The ping-pong type of movement is a problem caused by the mobility management. Thus, fixing this is out of scope of the NSIS protocols. </t>
-->
<t>4. Identification of the crossover node </t>
<t>When a handover at the edge of a network has happened, in the typical case, only some parts of the end-to-end path used by the data packets changes. In this situation, the cross-over node (CRN) plays a central role in managing the establishment of the new signaling application state, and removing any useless state, while localizing the signaling to only the affect part of the network. </t>
<!--
<t>NSIS solution: GIST provides NSLPs with an identifier of the next signaling peer, the SII Handle. When this handle changes, the NSLP knows a routing change has happened. Yet, the NSLP can also figure out if it is also the crossover node for the session. More details can be found in the NSLP specifications. </t>
-->
<t>5. Upstream State Update vs. Downstream State Update </t>
<t>Due to the asymmetric nature of Internet routing, the upstream and downstream paths are likely not to be exactly the same. Therefore, the state update needs to be handled independently for the upstream and the downstream. </t>
<t>6. Authorization Issues </t>
<t>The procedure of State Update may be initiated by the MN, the CN, or even nodes within the network (e.g., crossover node, MAP in HMIP). This State Update on behalf of the MN raises authorization issues about the entity that is allowed to make these state modifications. </t>
<!--
<t>NSIS solution: Since NSIS operates on a hop-by-hop basis, any peer can perform state updates. This is possible because a chain-of-trust is expected between NSIS nodes. If this weren't the case, e.g., true resource reservations would not be possible; one misbehaving or compromised node would effectively break everything. Thus, currently the NSIS protocols do not limit the roles of each NSIS signaling peer on a path, and any node can make updates. Yet, some updates are reflected back to the signaling end points, and they can decide whether the signaling actually succeeded, or not. </t>
-->
<t>7. Dead peer and invalid NR problem </t>
<t>When the MN is on the path of a signaling exchange, after handover the old AR can not forward NSLP messages any further to the MN. In this case, the old AR's mobility or routing protocol, or even the NSLP may trigger an error message to indicate that the last node fails or is truncated. This error message is forwarded and may mistakenly cause the removal of the state on the existing common path, if the state is not updated before the error message is propagated through the signaling peers. This is called the 'invalid NR problem'.</t>
<!--
<t>NSIS solution: In general, a QNE should be conservative when it receives an indication for a state removal caused by a change in routing. The QoS NSLP uses retransmissions and the RSN value to cope with the problem - see the QoS NSLP specification for more details. </t>
-->
<t>8. IP-in-IP Encapsulation </t>
<t>Mobility protocols may use IP-in-IP encapsulation on the segment of the end-to-end path for routing traffic from the CN to the MN, and vice versa. Encapsulation harms any attempt to identify and filter data traffic belonging to, for example, a QoS reservation. Moreover, encapsulation of data traffic may lead to changes in the routing paths since the source and the destination IP addresses of the inner header differ from those of the outer header. Mobile IP uses tunneling mechanisms to forward data packets among end hosts. Traversing over the tunnel, NSIS signaling messages are transparent on the tunneling path due to the change of flow's addresses. In case of interworking with Mobile IP-tunneling, CRNs can be discovered on the tunneling path. It enables NSIS protocols to perform State Update procedure over the IP-tunnel. In this case, GIST needs to cope with the change of Message Routing Information (MRI) for the CRN discovery on the tunnel. Also, NSLP signaling needs to determine when to remove the tunneling segment on the signaling path and/or how to tear down the old state via interworking with the IP-tunneling operation. </t>
<!--
<t>NSIS solution: If the signaling packets are encapsulated it is necessary to perform a separate signaling exchange for the tunneled region. Furthermore, a binding is needed to tie the end-to-end and tunneled session together. The QoS NSLP implements this session binding. </t>
-->
</section> <!-- End of L1 section -->
<!-- End of Challenges with Mobility -->
<!-- Start of L1 section --> <section title="Basic Operations for Mobility Support" anchor="Basic.OP">
<t>This section presents the basic operations of the NSIS protocol suite after mobility related route changes. Detailed discussion of the operation of Mobile IP with respect to NSIS protocols are discussed in the subsequent section.
</t>
<!--
There may be two possible ways of operations:
<list>
<t>- Option 1: GIST probes the route change by its periodical internal refreshes, then use NetworkNotification() API primitive to notify NSLPs to update their corresponding state. Here the operation may be incomplete before an end-to-end signaling is accomplished. </t>
<t>- Option 2: Upon a handover event (e.g., acquisition of a new IP address in the MN, or update of the binding cache in the HA or the CN, as it will be discussed in <xref target="Int.with.mip4.mip6" />), each NSLP updates its signaling state in the reflected path. For generality this option is preferred as it eventually accomplishes the signaling procedure, no matter whether optimization is encountered.</t>
</list>
</t>
<t>In both options, as the primary task of signaling will be performed in the NSLP layer, and the NSLP operation is of particular importance. In order to illustrate this the following subsection presents an example of QoS NSLP signaling for data traffic from the MN to the CN in the Mobile IPv6 route optimization mode, following the second option approach.</t>
<t>Furthermore, optimization of the signaling procedure may be used, to reduce the unnecessary signaling overhead and to minimize the processing. To optimize the signaling, two issues are identified, namely how to discover an appropriate CRN and how to perform the localized signaling (or so-called State Update) according to the direction of data flows.</t>
-->
<!-- Start of L2 section -->
<section title="General functionality">
<t>
The NSIS protocol suite decouples state and flow identification. A state is stored and referred by the Session ID (SID). Flows associated with a given NSLP state are defined by the Message Routing Information (MRI). GIST notices when a routing path associated with a SID changes, and provides a notification to the NSLP. It is then up to the NSLP to update the state information in the network. Thus, the effect is an update to the states, not a full new request. This decoupling effectively solves also a typical problem with certain signaling protocols, where protocol state is identified with flow endpoints, and when a flow endpoint changes, the whole session state becomes invalid.
</t>
<t>
A further benefit of the decoupling is that if the MRI, i.e., the IP addresses associated with the data flow, remain the same after movement, the NSIS signaling will repair only the affected path of the end-to-end session. Thus, updating the session information in the network will be localized, and no end-to-end signaling will be needed. If the MRI changes, end-to-end signaling can not be avoided since new information for proper data flow identification must be provided all the way between the data sender and receiver.
</t>
<t>
GIST provides NSLPs with an identifier of the next signaling peer, the SII Handle. When this SII Handle changes, the NSLP knows a routing change has happened. Yet, the NSLP can also figure out whether it is also the crossover node for the session. Thus, CRN discovery is always done at the NSLP layer because only NSLPs have a notion of end-to-end signaling. </t>
<t>
When a path changes, the session information on the old path needs to be removed. After a routing change, the NSLP running on the end-host or the CRN, depending on the direction of the session, can use the SII Handle (provided by GIST) to remove states on the old path; new session information is simultaneously set up on the new path. Both current NSLPs use sequence numbers to identify the order of messages, and this information can be used by the protocols to recover from a routing change.
</t>
<t>
Since NSIS operates on a hop-by-hop basis, any peer can perform state updates. This is possible because a chain-of-trust is expected between NSIS nodes. If this weren't the case, e.g., true resource reservations would not be possible; one misbehaving or compromised node would effectively break everything. Thus, currently the NSIS protocols do not limit the roles of each NSIS signaling peer on a path, and any node can make updates. Yet, some updates are reflected back to the signaling end points, and they can decide whether the signaling actually succeeded, or not.
</t>
<t>
If the signaling packets are encapsulated in a tunnel, it is necessary to perform a separate signaling exchange for the tunneled region. Furthermore, a binding is needed to tie the end-to-end and tunneled session together.
</t>
</section> <!-- End of L2 section -->
<!-- End of General functionality -->
<!-- Start of L2 section --> <section title="QoS NSLP" anchor="Basic.OP.example">
<!--
<t>NSIS solution: Removing old state in the network is a functionality of each NSLP independently. The QoS NSLP solves this through the use of the Reservation Sequence Number (RSN). The RSN makes it possible to identify new updated information related to a resource reservation. A QNE that is CRN for a given reservation is able to tear down an old reservation, and install a new reservation on the new path. More details can be found in the QoS NSLP specification. [WHAT DOES THE NAT/FW DO?] </t>
<t>When the MN is on the path of a signaling exchange, after handover the old AR can not forward NSLP messages any further to the MN. In this case, the old AR's mobility or routing protocol, or even the NSLP may trigger an error message to indicate that the last node fails or is truncated. This error message is forwarded and may mistakenly cause the removal of the state on the existing common path, if the state is not updated before the error message is propagated through the signaling peers. This is called the 'invalid NR problem'.</t>
-->
<t>The following figure illustrates an example of QoS NSLP signaling in a Mobile IPv6 route optimization case, for a data flow from the MN to the CN, where sender-initiated reservation is used. Once a handover event is detected in the MN, the MN must get to know
the new care-of-address and update the path coupled MRI accordingly.
Then the MN issues a QoS NSLP RESERVE message towards the CN, that
carries the unique session ID and other identification information
for the session, as well as the reservation requirements. Upon receipt of the RESERVE message, the QoS NSLP nodes (which will be discovered by the underlying NTLP) establish the corresponding QoS NSLP state, and forward the message towards the CN. When there is already an existing NSLP state with the same session ID, the state will be updated. If all the QoS NSLP nodes along the path support the required QoS, the CN in turn responds with a RESPONSE message, to confirm the reservation. </t>
<t>In a bi-directional tunneling case, the only difference is that the RESERVE message should be sent to the HA instead of the CN, and the node which responds with a RESPONSE should be the HA instead of the CN too. More details are discussed in <xref target="Int.with.mip4.mip6" /></t>
<t>Therefore, for the basic operation there is no fundamental difference among different operation modes of Mobile IP, and the main issue of mobility support in NSIS is to trigger NSLP signaling appropriately when a handover event is detected, and the destination of the NSLP signaling shall follow the Mobile IP data path as being path-coupled signaling. </t>
<t>In this process, the obsoleted state in the old path is not explicitly released. To speed up the process, it may be possible to localize the signaling to speed this process. When the RESERVE message reaches a node, depicted as CRN in this document, where a state is determined for the first time to reflect the same session, the node may issue a NOTIFY message towards the MN's old CoA. The QNE adjacent to MN's old position stops the NOTIFY message, and sends RESERVE message (with Teardown bit set) towards the CN, to release the obsoleted state. This RESERVE with tear message is stopped by the CRN. The RSN used in the messages is used to distinguish the order of the signaling. More details are described in <xref target="Localized.signaling.scenario" /> </t>
<figure title="Basic operation example" anchor="fig.Basic.OP.example">
<preamble></preamble>
<artwork>
<![CDATA[
MN QNE1 MN QNE2 QNE3 QNE4 CN
(CoA1) | (CoA2) | (CRN) | |
| | | | | | |
| | | | | | |
| | |RESERVE | | | |
| | |------->| | | |
| | | (1) |RESERVE | | |
| | | |--------->| | |
| | | | (2) |RESERVE | |
| | | | |------->| |
| | | | | (3) |RESERVE |
| | | | | |------->|
| | | | NOTIFY| | (4) |
| | | |<---------| | |
| | | NOTIFY| (9) | | |
| |<------------| | | |
| | | (10) | | | |
| |RESERVE(T) | | | |
| |------------>| | | |
| | | (11) |RESERVE(T)| | |
| | | |--------->| | |
| | | | (12) | |RESPONSE|
| | | | | |<-------|
| | | | |RESPONSE| (5) |
| | | | RESPONSE|<-------| |
| | |RESPONSE|<---------| (6) | |
| | |<------ | (7) | | |
| | | (8) | | | |
| | | | | | |
| | | | | | |
]]>
</artwork>
</figure>
</section> <!-- End of L2 section -->
<!--End of QoS NSLP-->
<!-- Start of L2 section --> <section title="Localized signaling in mobile scenarios" anchor="Localized.signaling.scenario">
<t>As shown in <xref target="fig.Top.NSIS.sig.caused.mob" />, mobility generally causes signaling path to either converge or diverge depending on the direction of each signaling flow.</t>
<figure title="The topology for NSIS signaling caused by mobility" anchor="fig.Top.NSIS.sig.caused.mob">
<preamble></preamble>
<artwork>
<![CDATA[
Old path
+--+ +-----+
original |MN|<------ |OAR | ---------^
address | | |NSLP1| ^
+--+ +-----+ ^ common path
| C +-----+ +-----+ +--+
| | |<--|NSLP1|----|CN|
| |NSLP2| |NSLP2| | |
v New path +-----+ +-----+ +--+
+--+ +-----+ V B A
New CoA |MN|<------ |NAR |----------V >>>>>>>>>>>>
| | |NSLP1| ^
+--+ +-----+ ^
D ^
>>>>>>>(Binding process)>>>>>>>>>>>>^
<=====(upstream signaling followed by data flows) =====
(a) The topology for upstream NSIS signaling flow due to
mobility
Old path
+--+ +-----+
original |MN|------> |OAR | ----------V
| | |NSLP1|
address +--+ +-----+ V common path
| K +-----+ +-----+ +--+
| | |---|NSLP1|--->|CN|
| |NSLP2| |NSLP2| | |
v New path +-----+ +-----+ +--+
+--+ +-----+ ^ M N
New CoA |MN|------> |NAR |-----------^ >>>>>>>>>>>>
| | |NSLP1| ^
+--+ +-----+ ^
L ^
>>>>>>>(Binding process)>>>>>>>>>>>>^
====(downstream signaling followed by data flows) ======>
(b) The topology for downstream NSIS signaling flow due to
mobility
]]>
</artwork>
</figure>
<t>These topological changes due to mobility cause the NSIS state established in the old path to be useless. such state may be removed as soon as possible. In addition, NSIS state needs to be established along the new path and be updated along the common path. The re-establishment of NSIS signaling may be localized when route changes (including mobility) occur to minimize the impact on the service and to avoid unnecessary signaling overhead. This localized signaling procedure is referred to as State Update (refer to the terminology section). In mobile environments, for example, the NSLP/ NTLP needs to limit the scope of signaling information only to the affected portion of the signaling path because the signaling path in the wireless access network usually changes only partially.</t>
<!--
<t>One of the most appropriate nodes to perform the State Update is the CRN where the old and new signaling paths meet. The CRN should be the logical merging point, not physical one. In the end, CRN discovery can be a crucial element to alleviate the double reservation and end-to-end signaling problems identified in <xref target="Problem.Statement" />.</t>
-->
<!-- Start of L3 section -->
<section title="CRN Discovery" anchor="CRN.discovery">
<t>The CRN is discovered at the NSLP layer.
In case of QoS NSLP, when a
RESERVE message with an existing SESSION_ID is received and its
Source Identification Information (SII) and MRI are changed, the QNE
knows its upstream or downstream peer has changed by the handover, for
sender-oriented and receiver-oriented reservations, respectively.
And realizes it is implicitly the CRN.
</t>
<!-- <t>The NTLP layer can easily detect route changes by tracking the SII-Handle of sessions. Thus, in theory, it would be possible to also discover the CRN at the NTLP layer since the NTLP is responsible for detecting the path change of data (or signaling) flow. However, in practice a routing change primarily affects an NSLP and its internal state and next peers, and this change is out of scope of NTLP which is mainly concerned with hop-by-hop transport of signaling messages. Thus, all the logic for CRN discovery and how it affects the application layer is ultimately the task of NSLP.</t>
<t>There can also be two different approaches for the CRN discovery messaging depending on whether or not the discovery is coupled with a signaling message: coupled approach and uncoupled approach. In the coupled approach, the signaling to install the NSIS state along the new path or update the state along the common path is performed simultaneously with the CRN discovery. In the uncoupled approach, the signaling for the State Update is performed after the CRN discovery is completed. These two approaches may differ in terms of security. Generally, the coupled approach in the NSIS protocol suit is preferred to the uncoupled approach to reduce the delay for state update. </t> -->
</section><!-- End of L3 section-->
<!--End of CRN Discovery-->
<!-- Start of L3 section -->
<section title="Localized State Update" anchor="State.setup.and.update">
<!--
<t>Before initiating the State Update, the MN or the CN needs to acquire necessary authentication and authorization for the corresponding state operation. The MN or the CN may also check the availability of resources on the new path. In case of QoS NSLP, the QUERY message can be used to find the availability of resources in the networks (e.g., access networks or core networks). If the resources along the new path are not sufficient, it may be needed to keep the state established previously using multihomed interfaces while blocking incoming new requests.</t>
-->
<t>In the downstream State Update, the MN initiates the RESERVE with a new RSN for state setup toward a CN and also the implicit DCRN discovery is performed by the procedure of signaling as described in <xref target="CRN.discovery" />. The MRI from the DCRN to the CN (i.e., common path) is updated by the RESERVE message. DCRN may also send NOTIFY with "Route change (0x02)" to previous upstream peer. The NOTIFY is forwarded hop-by-hop and reaches the edge QNE (i.e., QNE1 in <xref target="fig.Basic.OP.example"/>). After the QNE is aware that the MN as QNI has disappeard (how this is can be noticed is out of scope of NSIS, yet, e.g., GIST will eventually no this through undelivered messages), the QNE sends a tearing RESERVE towards downstream. When the tearing RESERVE reaches the DCRN, it stops forwarding and drops it. Note that, however, it is not necessary for GIST state to be explicitly removed because of the inexpensiveness of the state maintenance at the GIST layer <xref target="nsis.gist" />. Note that, the sender-initiated approach leads to faster setup than the receiver-initiated approach as in RSVP <xref target="rfc2205.rsvp" />.</t>
<t>In the scenario of an upstream State Update, there are two possible methods for state update. One is the CN (or a HA/ a GFA/ a MAP) sends the refreshing RESERVE message toward the MN to perform State Update by receiving trigger (e.g., MIP binding update). UCRN is discovered implicitly by the CN-initiated signaling along the common path as described in <xref target="CRN.discovery" />. When the refreshing RESERVE reaches to the adjacent QNE of UCRN, the QNE sends back a RESPONSE saying "full QSPEC required". Then the UCRN sends the RESERVE with full QSPEC towards the MN to set up a new reservation. The UCRN may also send tearing RESERVE to previous downstream peer. The tearing RESERVE is forwarded hop-by-hop and reaches to the edge QNE. After the QNE is aware that the MN as QNI has disappeard, the QNE drops the tearing peer. Another method is, if GIST hop is already established on the new path (e.g. by QUERY from the CN, or the HA/GFA/ MAP) when MN gets a hint from GIST that routing has changed, the MN sends a NOTIFY towards upstream saying "Route Change" 0x02. When the NOTIFY hits UCRN, the UCRN is aware that the NOTIFY is for a known session comes from a new SII-Handle. Then the UCRN sends a RESERVE with a new RSN and an RII towards the MN. By receiving the RESERVE, the MN replies RESPONSE. The UCRN may also send tearing RESERVE to previous downstream peer. The tearing RESERVE is forwarded hop-by-hop and reaches to the edge QNE. After the QNE is aware that the MN as QNI is disappeared, the QNE drops the tearing peer.</t>
<t>The State Update on the common path to reflect the changed MRI brings issues on the end-to-end signaling addressed in <xref target="Problem.Statement" />. Although the State Update over the common path does not give rise to re-processing of AAA and admission control, it may lead to the increased signaling overhead and latency.</t>
<t>One of the goals of the State Update is to avoid the double reservation on the common path as described in <xref target="Problem.Statement" />. The double reservation problem on the common path can be solved by establishing a signaling association using a unique SID and by updating packet classifier/MRI. In this case, even though the flows on the common path have different MRIs, it refers to the same NSLP state. </t>
</section><!-- End of L3 section-->
<!--End of State setup and update-->
</section> <!-- End of L2 section -->
<!--End of Localized signaling in mobile scenarios-->
<!-- <!-- Start of L2 section -->
<!-- <section title="NAT/FW NSLP" anchor="natfw-section">
<t>
THIS SECTION IS FOR MARTIN, HANNES ET AL.
</t>
</section> --> <!-- End of L2 section -->
<!-- End Of NATFW NSLP -->
</section> <!-- End of L1 section -->
<!-- End of "Basic Operations for Mobility Support" section -->
<!-- Start of L1 section --> <section title="Interaction with Mobile IPv4/v6" anchor="Int.with.mip4.mip6">
<t>In Mobile IP scenario, there are two types of data routings, one is triangular routing with tunneling section, and the other is optimized routing which is direct routing between an MN and a CN. This section analyzes NSIS operation with these data routes.</t>
<t>Mobility management solutions like Mobile IP try to hide mobility effects from applications by providing stable addresses and
avoiding address changes. On the other hand, the PC-MRI contains
flow addresses and will change if the CoA changes. Some NSLPs, such
as QoS NSLP, must be mobility-aware, because they
care about the resources on the actual current path.
NSLPs may have to interact with MIP and/or the tunnel
software in order to obtain current link properties,
esp. additional overhead for the QoS-NSLP that must be
taken into account in QSPEC (e.g., the m parameter in the
TMOD).</t>
<t>We note that NSLPs must be supported by mobility management
implementations in order to request information about the current
flow address (CoAs), source addresses, tunneling, or, overhead.
Furthermore, NSLPs can be notified about mobility events that
may require actions in the NSLP, e.g., sending a new RESERVE
or QUERY. Furthermore, an implementation must select proper
interface addresses in the NLI in order to ensure that a corresponding
Messaging Association is established along the same path as the flow in
the MRI.</t>
<!-- Start of L2 section -->
<section title="Interaction with Mobile IPv4" anchor="Int.with.MIP4">
<t>In Mobile IPv4 <xref target ="rfc3344.mip4" />, the data flows are forwarded based on triangular routing, and an MN retains a new CoA from the FA (or an external method such as DHCP) in the visited access network. When the MN acts as a data sender, the data and signaling flows sent from the MN are directly transferred to the CN not necessarily through the HA or indirectly through the HA using the reverse tunneling. On the other hand, when the MN act as a data receiver, the data and signaling flows sent from the CN are routed through the IP tunneling between the HA and the FA (or the HA and the MN in case of the Co-located CoA). With this approach, routing is dependent on the HA, and therefore the NSIS protocols interact with the IP tunneling procedure of Mobile IP for signaling.</t>
<t>The <xref target ="fig.mip4" /> (a) to (e) show the NSIS signaling flows depending on the direction of the data flows and the routing methods.</t>
<figure title="NSIS signaling flows under different Mobile IPv4 scenarios" anchor="fig.mip4">
<preamble></preamble>
<artwork>
<![CDATA[
MN FA (or FL) CN
| | |
| IPv4-based Standard IP routing |
|------------ |--------------------------------->|
| | |
(a) MIPv4: MN-->CN, no reverse tunnel
MN FA HA CN
| IPv4 (normal) | | |
|--------------->| IPv4(tunnel) | |
| |--------------->| IPv4 (normal)|
| | |------------->|
(b) MIPv4: MN-->CN, the reverse tunnel with FA CoA
MN (FL) HA CN
| | | |
| IPv4(tunnel) | |
|------------------------------->|IPv4 (normal) |
| | |-------------->|
(c) MIPv4: MN-->CN, the reverse tunnel with Co-located CoA
CN HA FA MN
|IPv4 (normal) | | |
|-------------->| | |
| | MIPv4 (tunnel) | |
| |---------------->| IPv4 (normal)|
| | |------------->|
(d) MIPv4: CN-->MN, Foreign agent Care-of-address
CN HA (FL) MN
|IPv4(normal ) | | |
|-------------->| | |
| | MIPv4 (tunnel) | |
| |------------------------------->|
| | | |
(e) MIPv4: CN-->MN with Co-located Care-of-address
]]>
</artwork>
</figure>
<t>When an MN (as a signaling sender) arrives at a new FA and the corresponding binding process is completed (<xref target ="fig.mip4" /> (a), (b) and (c)), the MN performs the CRN discovery (DCRN) and the State Update toward the CN (as described in <xref target="Basic.OP"/>) to establish the NSIS state along the new path between the MN and the CN. In case reverse tunnel is not used (<xref target ="fig.mip4" /> (a)), a new NSIS state is established on direct path from the MN to the CN. If the reverse tunnel and FA CoA are used (<xref target ="fig.mip4" /> (b)), a new NSIS state is established along a tunneling path from the FA to the HA separately from end-to-end path. CRN discovery and State Update in tunneling path is also separately performed if necessary. If the reverse tunnel and co-located CoA are used (<xref target ="fig.mip4" /> (c)) the NSIS signaling for the DCRN discovery and the State Update is the same as the case of using FA CoA above except for the use of the reverse tunneling path from the MN to the HA. That is, in this case, one of tunnel end points is the MN, not the FA.</t>
<t>When an MN (as a signaling receiver) arrives at a new FA and the corresponding binding process is completed (<xref target ="fig.mip4" /> (d) and (e)), the MN sends NOFITY message to the signaling sender, i.e., the CN. In case FA CoA is used (<xref target ="fig.mip4" /> (d)), the CN initiates a NSIS signaling to update an existing state between the CN and the HA, and afterwards the NSIS signaling messages are forwarded to the FA and reaches to the MN. A new NSIS state is established along the tunneling path from the HA to the FA separately from end-to-end path. During this operation, a UCRN is discovered on the tunneling path, and a new MRI for the State Update on the tunnel may need to be created. CRN discovery and State Update in tunneling path is also separately performed if necessary. In case collocated CoA is used (<xref target ="fig.mip4" /> (d)) the NSIS signaling for the UCRN discovery and the State Update is also the same as the case of using FA CoA above except for the end point of tunneling path from the HA to the MN.</t>
<t>Note that Mobile IPv4 optionally supports route optimization. In the case route optimization is supported, the signaling operation will be the same as Mobile IPv6 route optimization.</t>
</section> <!-- End of L2 section -->
<!-- End of Interaction with Mobile IPv4 -->
<!-- Start of L2 section -->
<section title="Interaction with Mobile IPv6" anchor="Int.with.MIP6">
<t>Unlike Mobile IPv4, with Mobile IPv6 <xref target ="rfc3775.mip6" />, the FA is not required on the data path. If an MN moves to visited network, a CoA at the network is allocated like co-located CoA in Mobile IPv4. In addition, the route optimization process between the MN and CN can be used to avoid the triangular routing in the Mobile IPv4 scenarios.</t>
<t>If the route optimization is not used, data flow routing and NSIS signaling procedures (including the CRN discovery and the State Update) will be similar to the case of using the Mobile IPv4 with co-located CoA. However, if Route Optimization is used, signaling messages are sent directly from the MN to the CN, or from the CN to the MN. Therefore, route change procedures described in <xref target="Basic.OP"/> are applicable to this case.</t>
</section>
<!-- End of L2 section -->
<!-- End of Interaction with Mobile IPv6 -->
<!-- Start of L2 section -->
<section title="Interaction with Mobile IP tunneling" anchor="Int.with.MIPtunnel">
<t>In this section, we assume that MN acts as an NI and CN acts as an NR in interworking between Mobile IP and NSIS signaling.</t>
<t>Scenarios for interaction with Mobile IP tunneling vary depending on:
<list>
<t>- Whether a tunneling entry point (Tentry) is an MN or other node. In case Mobile IPv4 co-located CoA or Mobile IPv6, Tentry is an MN. In case Mobile IPv4 FA CoA case, Tentry is a FA. In both case, a HA is tunneling exit point (Texit).</t>
<t>- Whether the mode of QoS-NSLP signaling is sender-initiated or receiver initiated.</t>
<t>- Whether the signaling mode over tunnel is sequential mode or parallel mode. In sequential mode, end-to-end signaling pauses when it is waiting for results of tunnel signaling, and resumes upon receipt of the tunnel signaling outcome. In parallel mode, end-to-end signaling continues outside the tunnel while tunnel signaling is still in process and its outcome is unknown <xref target ="nsis.tunneling" />.</t>
</list>
</t>
<t>The following subsection describes sender-initiated and receiver-initiated reservation with Mobile IP tunneling and CRN discovery and State Update with Mobile IP tunneling.</t>
<!-- Start of L3 section -->
<section title="Sender-Initiated Reservation with Mobile IP tunnel" anchor="Int.with.MIPtunnel.SI">
<t>The following scenario assumes that a FA is a Tentry. However the procedure is the same for the case an MN is a Tentry if it is considered that the MN and the FA are the same node.
<list>
<t>- When an MN moves into a new network attachment point, QoS- NSLP in the MN initiates RESERVE (end-to-end) message to start the State Update procedure. The GIST below the QoS-NSLP adds GIST header and then sends the encapsulated RESERVE message to peer GIST node with corresponding QoS-NSLP for DCRN discovery. In this case, the peer GIST node is a FA if the FA is an NSIS-aware node. The FA is one of the endpoints of Mobile IP tunneling: Tentry. In case of interaction with tunnel signaling originated from the FA, there can be two scenarios depending on whether NSIS signaling interacts with the Mobile IP tunneling. The first scenario is that the NSIS signaling is discerned on the tunneling path between the FA and corresponding HA, and then the tunneling path becomes an NSIS-aware cloud. The second one is otherwise, and here the tunneling path is transparent as a logical link to NSIS signaling <xref target ="nsis.tunneling" />.</t>
<t>- In the NSIS-aware tunneling scenarios, as shown in <xref target ="fig.miptunnel.SI.SE" /> and <xref target ="fig.miptunnel.SI.PA" />, upon receiving the RESERVE message from the MN, the QoS-NSLP of FA explicitly creates a new RESERVE-t (tunnel) message, which keeps the existing (end-to-end) Session ID and includes a new (tunneling) MRI different from the (end-to-end) MRI, to distinguish the NSIS signaling messages over the Mobile IPv4 tunneling path. The RESERVE-t message is forwarded toward HA, another end point of Mobile IPv4 tunneling. Also, after receiving the RESERVE-t message from the FA, the HA should decide whether it needs to initiate a RESPONSE-t (tunnel) message toward FA for responding to the RESERVE-t message, or make the RESPONSE-t message wait until a RSESPONSE message, which is created to react the RESERVE message, arrives from the CN.</t>
<t>- In this procedure of NSIS-tunnel signaling, again, two categories of tunnel signaling mode are taken into consideration, i.e., either sequential or parallel mode.</t>
<t>- Provided that the tunnel signaling mode is sequential as shown in <xref target ="fig.miptunnel.SI.SE" />, the RESERVE signaling toward the HA resumes after confirming completeness of NSIS tunnel signaling through the RESERVE-t and the RESPONSE-t messages. Arriving at HA, the RESERVE message is forwarded to CN to update or refresh the existing NSIS states (QoS-NSLP and GIST) on the common path. The CN initiates a RESPONSE message, responding to the RESERVE message, toward the HA as its destination. The HA forwards the RESPONSE message to the FA after encapsulating the message. Finally, the RESPONSE message is sent to MN after being decapsulated at the FA. Note that both end-to-end signaling messages, the RESPONSE and the RESERVE messages, are not discernible on the tunneling path, like a logical link, and those messages just play a role of NSIS signaling for establishing end-to-end state.</t>
<t>- Provided that the tunnel signaling mode is parallel as shown in <xref target ="fig.miptunnel.SI.PA" />, upon receiving the RESERVE message from the MN, the FA forwards it to the HA immediately. Also, arriving at the HA from the CN, the RESPONSE message is again forwarded from the HA to the FA regardless of the delivery of RESPONSE-t message. Since in this parallel mode the end-to-end signaling messages do not reconcile with both NSIS-tunnel signaling messages, the RESERVE-t and RESPONSE-t messages, the tunneling path operates like a logical link and thus NON-QoS-HOP flag is set within the RESERVE message although NSIS-tunnel signaling messages are available on the tunnel path.</t>
</list>
</t>
<figure title="Sender-Initiated QoS-NSLP over Tunnel - Sequential Mode" anchor="fig.miptunnel.SI.SE">
<preamble></preamble>
<artwork>
<![CDATA[
MN (Sender) FA (Tentry) Tnode HA (Texit) CN (Receiver)
| | | | |
| RESERVE | | | |
+--------->| | | |
| |RESERVE-t | | |
| +=========>| | |
| | |RESERVE-t | |
| | +=========>| |
| | |RESPONSE-t| |
| | |<=========+ |
| |RESPONSE-t| | |
| |<=========+ | |
| | RESERVE | |
| +-------------------->| |
| | | | RESERVE |
| | | +--------->|
| | | | RESPONSE |
| | | |<---------+
| | RESPONSE | |
| |<--------------------+ |
| RESPONSE | | | |
|<---------+ | | |
| | | | |
]]>
</artwork>
</figure>
<figure title="Sender-Initiated QoS NSLP over Tunnel - Parallel Mode" anchor="fig.miptunnel.SI.PA">
<preamble></preamble>
<artwork>
<![CDATA[
MN (Sender) FA (Tentry) Tnode HA (Texit) CN (Receiver)
| | | | |
| RESERVE | | | |
+--------->| | | |
| |RESERVE-t | | |
| +=========>| | |
| | |RESERVE-t | |
| | +=========>| |
| | RESERVE | |
| +-------------------->| |
| | | | RESERVE |
| | | +--------->|
| | | | RESPONSE |
| | | |<---------+
| | |RESPONSE-t| |
| | |<=========+ |
| |RESPONSE-t| | |
| |<=========+ | |
| | RESPONSE | |
| |<--------------------+ |
| RESPONSE | | | |
|<---------+ | | |
| | | | |
]]>
</artwork>
</figure>
</section> <!-- End of L3 section -->
<!-- End of Sender-Initiated Reservation with Mobile IP tunnel-->
<!-- Start of L3 section -->
<section title="Receiver-Initiated Reservation with Mobile IP tunnel" anchor="Int.with.MIPtunnel.RI">
<t><xref target ="fig.miptunnel.RI.SE" /> and <xref target ="fig.miptunnel.RI.PA" /> show examples of receiver-initiated operation with Mobile IP tunnel for Sequential and Parallel modes, respectively. Basic Operation is the same as sender-initiated case.</t>
<figure title="Receiver-Initiated QoS NSLP over Tunnel - Sequential Mode" anchor="fig.miptunnel.RI.SE">
<preamble></preamble>
<artwork>
<![CDATA[
MN (Sender) FA (Tentry) Tnode HA (Texit) CN (Receiver)
| | | | |
|QUERY | | | |
+--------->| QUERY | |
| +-------------------->| QUERY |
| | | +--------->|
| | | | RESERVE |
| | RESERVE |<---------+
| |<--------------------+ |
| | QUERY-t | | |
| +=========>| QUERY-t | |
| | +=========>| |
| | |RESERVE-t | |
| |RESERVE-t |<=========+ |
| |<=========+ | |
| |RESPONSE-t| | |
| RESERVE +=========>|RESPONSE-t| |
|<---------| +=========>| |
| RESPONSE | | | |
+--------->| RESPONSE | |
| +-------------------->| RESPONSE |
| | | +--------->|
| | | | |
]]>
</artwork>
</figure>
<figure title="Receiver-Initiated QoS NSLP over Tunnel - Parallel Mode" anchor="fig.miptunnel.RI.PA">
<preamble></preamble>
<artwork>
<![CDATA[
MN (Sender) FA (Tentry) Tnode HA (Texit) CN (Receiver)
| | | | |
|QUERY | | | |
+--------->| QUERY | |
| +-------------------->| QUERY |
| | | +--------->|
| | | | RESERVE |
| | RESERVE |<---------+
| RESERVE |<--------------------+ |
|<---------+ | | |
| | QUERY-t | | |
| +=========>| QUERY-t | |
| | +=========>| |
| | |RESERVE-t | |
| |RESERVE-t |<=========+ |
| |<=========+ | |
| |RESPONSE-t| | |
| +=========>|RESPONSE-t| |
| | +=========>| |
| RESPONSE | | | |
+--------->| RESPONSE | |
| +-------------------->| RESPONSE |
| | | +--------->|
| | | | |
]]>
</artwork>
</figure>
</section><!-- End of L3 section -->
<!-- End of Receiver-Initiated Reservation with Mobile IP tunnel-->
<!-- Start of L3 section -->
<section title="CRN discovery and State Update with Mobile IP tunneling">
<t>Interaction with Mobile IP tunneling scenario can define two types of CRNs, i.e., a CRN on end-to-end path and a CRN on tunneling path. CRN discovery and State Update for these two paths are operated independently.</t>
<t>CRN discovery for end-to-end path is initiated by the MN by sending RESERVE (sender-initiated case) or QUERY (receiver-initiated case) message. As MN uses HoA as source address even after handover, a CRN is found by normal route change process (i.e., the same SID and FID, but different SII handle). If a HA is QoS-NSLP aware, the HA is found as the CRN. The CRN initiate tearing process on the old path as described in <xref target ="nsis.qosnslp" /></t>
<t>CRN discovery for tunneling path is initiated by Tentry by sending RESERVE-t (sender-initiated case) or QUERY-t (receiver-initiated case) message. The route change procedures described in <xref target="Basic.OP"/> are applicable to this case.</t>
</section> <!-- End of L3 section -->
<!-- End of CRN discovery and State Update with Mobile IP tunneling-->
</section><!-- End of L2 section -->
<!-- End of Interaction with Mobile IP tunnneling-->
</section> <!-- End of L1 Section -->
<!-- End of Interaction with Mobile IPv4/v6-->
<!-- Start of L1 section --> <section title="Further Studies" anchor="Further.Studies">
<t> All sections above dealt with basic issues on NSIS mobility support. This section introduces potential issues and possible approaches
for complicated scenarios in the mobile environment, i.e., peer failure
scenarios, multihomed scenarios, and interworking with other mobility
protocols, which may need to be resolved in the future. Topics in
this section are out-of-scope of this document, and detailed operations
are not described.</t>
<!-- Start of L2 section -->
<section title="NSIS Operation in the multihomed mobile environment">
<t>In multihomed mobile environments, multiple interfaces and addresses
(i.e., CoAs and HoAs) are available. This case, two major issues can
be considered. One is how to select or acquire the most appropriate
interface(s) and/or address(es) from end-to-end QoS point of view.
The other is, when multiple paths are simultaneously used for load-
balancing purpose, how to differentiate and manage two types of CRNs,
i.e., CRN between two on-going Paths (LB-CRN: Load Balancing CRN) and
CRN between the old and new paths caused by MN's handover (HO-CRN:
Handover CRN). This section introduces possible approaches for these
issues.</t>
<!-- Start of L3 section -->
<section title="Selecting the best interface(s)/CoA(s)">
<t>In MIPv6 route optimization case, if multiple CoAs registration is provided <xref target ="monami.mulcoareg" />, the contents of QUERYs sent by candidate CoAs can be used to select the best interface(s)/CoA(s).</t>
<t>Assume that an MN is a data sender and has multiple interfaces. Now
the MN moves to a new location and acquires CoA(s) for multiple
interfaces. After the MN performs the BU/BA procedure, it sends
QUERY messages toward the CN through the interface(s) associated with
the CoA(s). On receiving the QUERY messages, the CN or Gateway,
determines the best (primary) CoA(s) by checking 'QoS available'
field in the QUERY messages. Then a RESERVE message is sent toward
the MN to reserve resources along the path the primary CoA takes. If
the reservation is not successful, the CN transmits another RESERVE
message using the CoA with the next highest priority. The CRN may
initiate a teardown (RESERVE with the TEAR flag set) message toward
old access router (OAR) to release the reserved resources on the old
path.</t>
<t>In case of sender-initiated reservation, a similar approach is
possible. That is, the QUERY and RESERVE messages are initiated by
an MN, and the MN selects the Primary CoA based on the information
delivered by the QUERY message.</t>
<figure title="Receiver-initiated reservation in the multihomed environment">
<preamble></preamble>
<artwork>
<![CDATA[
|--Handover-->|
MN OAR AR1 AR2 AR3 CRN CRN CRN CN
(OAR/AR1)(OAR/AR2)(OAR/AR3)
| | | | | | | | |
|---QUERY(1)->|-------------------->|---------------------->|
| | | | | | | | |
|---QUERY(2)-------->|--------------------->|-------------->|
| | | | | | | | |
|---QUERY(3)--------------->|---------------------->|------>|
| | | | | | | | |
| | | | | | | | Primary CoA
| | | | | | | | Selection(4)
| | | | | | | | |
| | | | | | |<--RESERVE(5)--|
| | | |<------RESERVE(6)-----| (MRI |
| | | | (Actual reservation) | Update) |
|<----RESERVE(7)-----| | | | | |
| | | | | | | | |
| |<-----------teardown(8)-------------| | |
| | | | | | | | |
| | | | Multimedia Traffic | | |
|<=================->|<===================->|<=============>|
| | | | | | | | |
]]>
</artwork>
</figure>
</section><!-- End of L3 section -->
<!-- End of Selecting the best interface(s)/CoA(s)-->
<!-- Start of L3 section -->
<section title="Differentiation of two types of CRNs">
<t>When multiple interfaces of the MN are simultaneously used for load-balancing purpose, a possible approach for distinguishing LB-CRN and HO-CRN will introduce an identifier to determine the relationship between interfaces and paths.</t>
<t>An MN uses interface 1 and interface 2 for the same session, where the paths (say path 1 and path 2) have the same SID but different FIDs as shown in (a) of <xref target="fig.pathtype" />. Now one of the interfaces of MN performs a handover and obtains a new CoA, the MN will try to establish a new path (say Path 3) with the new FID, as shown in (b) of <xref target="fig.pathtype" />. In this case the CRN between path 2 and path 3 cannot determine if it is LB-CRN or HO-CRN since for both cases, SID is the same but FIDs are different. Hence the CRN will not know if State Update is required. One possible solution to solve this issue will introduce path classification identifier which shows the relationship between interfaces and paths. For example, signaling messages and QNEs belong to paths from interface 1 and interface 2 carry the identifier '00' and '02', respectively. By having this identifier, the CRN between path 2 and path 3 will be able to determine whether it is LB-CRN or HO-CRN. For example, if path 3 carries '00', the CRN is LB-CRN, and if '01', the CRN is HO-CRN.</t>
<figure title="The topology for NSIS signaling in multihomed mobile environments" anchor="fig.pathtype">
<preamble></preamble>
<artwork>
<![CDATA[
+--+ Path 1 +---+ +--+
| |IF1 <-----------------|LB | common path | |
|MN| |CRN|-------------|CN|
| | Path 2 | | | |
| |IF2 <-----------------| | | |
| | +---+ +--+
| |
+--+
(a) NSIS Path classification in multihomed environments
+--+ Path 1 +---+ +--+
| |IF1 <-----------------|?? | common path | |
|MN| |CRN|-------------|CN|
| | Path 2 -| | | |
| |IF2 <--- +------+ | | | | |
| | \_|??-CRN|--v +---+ +--+
| | / +------+
+--+IF? <---
Path 3
(b) NSIS Path classification after handover
]]>
</artwork>
</figure>
</section><!-- End of L3 section -->
<!-- End of Differentiation of two types of CRNs-->
</section><!-- End of L2 section -->
<!-- End of NSIS Operation in the multihomed mobile environment-->
<!-- Start of L2 section -->
<section title="Interworking with other mobility protocols">
<t>Unlike the generic route changes, in mobility scenarios, the end-to-end signaling problem by the State Update gives rise to the
degradation of network performance, e.g., increased signaling
overhead, service blackout, and so on. To reduce signaling latency
in the Mobile IP-based scenarios, the NSIS protocol suite may need to
interwork with localized mobility management (LMM). If the GIST/NSLP
(QoS-NSLP or NAT/FW-NSLP) protocols interact with Hierarchical Mobile
IPv6 and the CRN is discovered between an MN and an MAP, the State
Update can be localized by address mapping. However, how the State
Update is performed with scoped signaling messages within the access
network under the MAP is for future study.</t>
<t>In the inter-domain handover, a possible way to mitigate the latency
penalty is to use the multi-homed MN. It is also possible to allow
the NSIS protocols to interact with mobility protocols such as
Seamoby protocols (e.g., CARD [RFC4066] and CXTP [RFC4067]) and FMIP.
Another scenario is to use peering agreement which allows aggregation
authorization to be performed for aggregate reservation on an inter-
domain link without authorizing each individual session. How these
approaches can be used in NSIS signaling is for further study.</t>
</section>
<!-- End of L2 section -->
<!-- End of Interworking with other mobility protocols-->
<!-- Start of L2 section --><section title="Intermediate node becomes a dead peer">
<t>The failure of a (potential) NSIS CRN may result in incomplete state
re-establishment on the new path and incomplete teardown on the old
path after handover. In this case, a new CRN should be re-discovered
immediately by the CRN discovery procedure.</t>
<t>The failure of an AR may make the interactions with Seamoby protocols
(such as CARD and CXTP) impossible. In this case, the neighboring
peer closest to the dead AR may need to interact with such protocols.
A more detailed analysis of interactions with Seamoby protocols is
left for future work.</t>
<t>In Mobile IP-based scenarios, the failures of NSIS functions at an FA
and an HA may result in incomplete interaction with IP-tunneling. In
this case, recovery for NSIS functions needs to be performed
immediately. In addtion, a more detailed analysis of interactions
with IP-tunneling is left for future work.</t>
</section><!-- End of L2 section -->
<!-- End of Intermediate node becomes dead peer-->
</section><!-- End of L1 section -->
<!-- End of Further Study -->
<!-- Start of Security Consideration Section -->
<!-- Start of L1 section --> <section title="Security Considerations" anchor="Security.Considerations">
<t>This document does not introduce new security concerns.
The security considerations pertaining to the standard NSIS protocol
specifications [gist, qos-nslp, natfw-nslp] remain relevant.
When deployed in service provider networks, it is mandatory to
ensure that only authorized entities are permitted to
initiate re-establishment and removal of NSIS states in mobile environments,
including the use of NSIS proxies.</t>
</section> <!-- End of L1 section -->
<!-- End of Security Considerations -->
<!-- Start of Open Issues -->
<!-- Start of L1 section -->
<section title="Open Issues">
<t>1. MIP Interaction Part (<xref target="Int.with.mip4.mip6" />)
<list>
<t>- This section should illustrate how Tunnel I-D is applicable to MIP cases.</t>
<t>Discussion: How does this section should be cleaned up?</t>
</list>
</t>
</section> <!-- End of L1 section -->
<!-- Start of Change History -->
<!-- Start of L1 section -->
<section title="Change History">
<!-- Start of L2 section -->
<section title="Changes from -00 version">
<t>The major change made to the initial (-00) version of the draft is to re-arrange the issues addressed in the draft in order to clearly identify general issues caused by mobility itself and NSIS protocols-
specific issues. The generic route changes-related text in Section 4 was moved into Appendix to make this draft more mobility-specific.</t>
<t>Specifically, the following changes have been made:
<list style="numbers">
<t>Removed the terminologies, 'uplink' and 'downlink' in Section 2.</t>
<t>Removed the terminology, 'local repair' in Sections 2 and 4.</t>
<t>Re-arranged all problems in Section 3 by merging the 'mobility-related issues with NSIS protocols' section and the 'problem statement and general considerations' section.</t>
<t>Removed the general considerations section in Section 3.</t>
<t>Modified the problem statement section and moved it into the general problem section in Section 3.1.</t>
<t>Added more problems including 'Identification of the crossover node', 'Key exchanges', and 'AA-related Issues' to Section 3.1</t>
<t>Added the 'Multihoming-related issues' to Section 3.2.4</t>
<t>Removed the issues on 'how to immediately delete the state on the old path' in Section 3.2.</t>
<t>Moved the generic route changes-related text in Section 4.1 into Appendix.</t>
<t>Removed the figure describing "NSIS signaling topology for downstream signaling flow after the route changes in the middle of the network" in Figure 2.</t>
<t>Added 'NSLP_IDs' to each node in Figure 1.</t>
<t>Removed the 'use cases of identifiers' section, and instead, added the 'support for ping-pong type handover' section to Section5.</t>
<t>Added this change history.</t>
</list>
</t>
</section>
<!-- End of L2 section -->
<!-- Start of L2 section -->
<section title="Changes from -01 version">
<t>Version -02 includes mainly a number of clarifications on the issues raised in this draft and more details in some specific areas.
Specifically, the following changes have been made:
<list style="numbers">
<t>Defined the terminologies, 'route change' and 'mobility' in Section 2.</t>
<t>Clarified the terminology, 'Crossover node (CRN)' in Section 2.</t>
<t>Removed the terminology, 'mobility CRN' in Section 2.</t>
<t>The issue, 'Priority of signaling messages' in Section 3.2.2 was closed, and thus removed it.</t>
<t>Clarified the issue, 'CRN discovery and State Update on the IP-tunneling path in Section 3.2.4.</t>
<t>Added the pros and cons of two mechanisms on CRN discovery dependent on NSIS layers to Section 4.2.1.</t>
<t>Clarified the identifier, NSLP_Br_ID for CRN discovery in Section 4.2.2.</t>
<t>Added the scenario on interaction between NSIS and Mobile IP to Section 5.1.</t>
<t>Clarified interaction issues with IP-tunneling according to reservation initiation type (receiver-initiated or sender-initiated) in Mobile IPv4-based scenarios and added those to Section 5.1.1.1.</t>
<t>1Clarified interaction issues between NSIS protocols and IP-tunneling in Mobile IPv6 and added those to Section 5.1.1.2.</t>
<t>Clarified the multihoming-related issues in Section 5.2.</t>
<t>Added the issues on usage of 'hint' information to trigger NSIS signaling in mobility to Section 5.5.</t>
<t>Identified the dead peer-related issues in Mobile IP-based scenario in Section 5.5.</t>
</list>
</t>
</section>
<!-- End of L2 section -->
<!-- Start of L2 section -->
<section title="Changes from -02 version">
<t>In version -03, tunneling-related and multihoming-related scenarios were newly added in Sections 5.1.3 and 5.2, respectively. Also, the terminology, 'Path Update' is changed into 'State Update' in Section 3.2.4.</t>
</section>
<!-- End of L2 section -->
<!-- Start of L2 section -->
<section title="Changes from -03 version">
<t>Version -04 includes mainly a number of clarifications on the issues raised in this draft and more details in some specific areas.
Specifically, the following changes have been made:
<list style="numbers">
<t>The issue, 'Peering agreement issue' in Section 3.2.2 was closed, and thus removed it.</t>
<t>Clarified the issue, 'Interfaces between Mobile IP and NSIS protocols' in Section 3.2.1.</t>
<t>Clarified the issue, 'Authorization-related issues with teardown' in Section 3.2.2.</t>
<t>Clarified the issue, 'Dead peer discovery' in Section 3.2.2.</t>
<t>Clarified the issue, 'Invalid NR problem' in Section 3.2.2.</t>
<t>Clarified the issue, 'CRN discovery and State Update on the IP-tunneling path' in Section 3.2.4.</t>
<t>Clarified the issue, 'Multihoming-related issues' in Section 3.2.4.</t>
<t>Changed Figure 1 (a) into (b) in Section 4.1.</t>
<t>Changed Figure 1 (b) into (a) in Section 4.1.</t>
<t>Clarified the identifier, NSLP_Br_ID for CRN discovery in Section 4.2.2.</t>
<t>Clarified the identifier, Mobility identifier for CRN discovery in Section 4.2.2.</t>
<t>Added the text on 'CRN_DISCOVERY flag bit' in Section 4.2.3, and clarified the role of 'CD flag bit' in Section 4.3.1.</t>
<t>Clarified the issues on 'interaction with Mobile IP tunneling' and added those to Section 5.1.4.</t>
<t>Clarified the issues on 'load balancing in multihomed mobile environments' and added those to Section 5.2.5.</t>
<t>Changed Problems of the heading name in Section 3.2 into Challenges.</t>
</list>
</t>
</section>
<!-- End of L2 section -->
<!-- Start of L2 section -->
<section title="Changes from -04 version">
<t>Version -05 includes mainly a number of clarifications on the issues raised in this draft and more details in some specific areas.
Specifically, the following changes have been made:
<list style="numbers">
<t>'Explicit routes' in Section 3.1 (3) was removed. </t>
<t>Clarified the problem, 'Double reservation problem' in Section 3.1 (7). </t>
<t>Clarified the issue, 'CRN discovery-related issues' in Section 3.2.4 (1).</t>
<t>Clarified the issue, 'Issues on API between NTLP and NSLP' in Section 3.2.4 (3).</t>
<t>Clarified the issue, 'approaches for CRN discovery' in Section 4.2.1.</t>
<t>Changed NSLP_Br_ID (of identifiers for CRN discovery) into State_Br_ID in Section 4.2.2 for clarification.</t>
<t>Clarified the issue, 'double reservation problem on the common path' in Section 4.3.1.</t>
<t>Clarified the issue, 'Interfaces between Mobile IP and NSIS' in Section 5.1.1.</t>
<t>Removed the sencond paragraph on the issue, 'Explicit routes' in Section 4.1.</t>
<t>Clarified the issue, 'refresh timer value in mobility scenarios' in Section 5.3.</t>
<t>Removed the third paragraph on the issue, 'usage of Reservation Sequence Number (RSN) to support ping-pong type hanover' in Section 5.4.</t>
<t>Clarified the issues on 'peer failure' in Section 5.5. </t>
<t>Removed Figure 3 'Sender- vs. Receiver-initiated reservation' in Section 4.3.1. </t>
</list>
</t>
</section>
<!-- End of L2 section -->
<!-- Start of L2 section -->
<section title="Changes from -05 version">
<t>In Version -06, contents of this draft were re-selected and re-structured:
<list style="numbers">
<t>Section 4 and 5 of -05 were divided into two parts:
<list>
<t>'Main' part, which is focusing on examples and describing how mobility is handled by the NSIS protocols. Topics here will be route change handling and NSIS interwork with MIP v4/v6 (<xref target="Basic.OP" /> and <xref target="Int.with.mip4.mip6" /> in -06)</t>
<t>'Further Study' part, which introduces summary of potential issues and possible approaches for other topics. These topics are out-of-scope for discussing details (<xref target="Further.Studies" /> in -06)</t>
</list><!--End of Nested List-->
</t>
<t>Specific parameters and terms were removed from 'Main' part</t>
<t>Showing similar detailed operations were avoided in 'Interaction with MIP tunneling section (<xref target="Int.with.MIPtunnel" />)'</t>
<t>In Further Study section <xref target="Further.Studies" />:
<list>
<t>Detailed operations were removed</t>
<t>Ping-pong issue was removed</t>
</list><!--End of Nested List-->
</t>
<t>Problem Statement (<xref target="Problem.Statement" />) was cleaned up</t>
</list>
</t>
</section>
<!-- End of L2 section -->
<!-- Start of L2 section -->
<section title="Changes from -06 version">
<t>Changes in Version -07 are:
<list style="numbers">
<t>'Invalid NR problem' are moved from Further Study section </t>
<t>Figure 7 (Receiver-Initiated QoS NSLP over Tunnel -Parallel Mode) are changed</t>
<t>Terminologies 'NSLP CRN', 'NTLP CRN' 'NSIS CRN' 'Divergent-convergent UCRN' and 'Divergent-convergent DCRN' are removed from Terminology section.</t>
<t>'Open Issues' section is added</t>
</list>
</t>
</section>
<!-- End of L2 section -->
<!-- Start of L2 section -->
<section title="Changes from -07 version">
<t>Changes in Version -08 are:
<list style="numbers">
<t>Figure 1 was updated (NOTIFY message from CRN is added) </t>
<t>Section 4.2.1 (CRN discovery) was updated to be synchronized with QoS-NSLP draft</t>
<t>Title of Section 4.2.2 was changed from "State setup and update" to "Localized State Update"</t>
<t>Section 4.2.2 (Localized State Update) was updated to be synchronized with QoS-NSLP draft</t>
<t>Section 4.2.3 (State teardown) was deleted because the issues was already solved</t>
<t>Title of Section 4.2.3 was changed to "State teardown consideration"</t>
</list>
</t>
</section>
<!-- End of L2 section -->
<!-- Start of L2 section -->
<section title="Changes from -08 version">
<t>Changes in Version -09 are:
<list style="numbers">
<t>Security Consideration Section (Section 7) was cleaned up.</t>
<t>Security Consideration issue was removed from Open Issue section (Section 8).</t>
<t>NAT traversal issues were removed from Open Issue section (Section 8).</t>
</list>
</t>
</section>
<!-- End of L2 section -->
<!-- Start of L2 section -->
<section title="Changes from -09 version">
<t>Changes in Version -10 are:
<list style="numbers">
<t>Introduction was updated accordingly.</t>
<t>Definition of RFC2119 terms were removed from Section 2</t>
<t>Definition of Upstream/Downstream State Update were cleaned up</t>
<t>Title of Section 3 was changed from "Problem Statement" to "Challenges with Mobility"</t>
<t>NSIS solutions are removed from Section 3</t>
<t>Section 4 was cleaned up</t>
<t>More detailed description was added to Section 5</t>
</list>
</t>
</section>
<!-- End of L2 section -->
</section>
<!-- End of L1 section -->
<!-- End of Change History -->
<!-- Start of Contributors Section -->
<section title="Contributors">
<t>Sung-Hyuck Lee was the first editor of the draft. Since version 06 of the draft, Takako Sanda has taken the editorship.</t>
<t> Many individuals have contributed to this draft. Since it was not possible to list them all in the authors section, this section was created to have a sincere respect for other authors, Paulo Mendes, Robert Hancock, Roland Bless and Shivanajay Marwaha. Separating authors into two groups was done without treating any one of them better (or worse) than others.</t>
</section>
<!-- End of Contributors Section -->
<!-- Start of Acknowledgements Section -->
<section title="Acknowledgements">
<t>The authors would like to thank Byoung-Joon Lee, Charles Q. Shen, Cornelia Kappler, Henning Schulzrinne, and Jongho Bang for significant contributions in four earlier drafts and the previous draft. The authors would also like to thank Robert Hancock, Andrew Mcdonald, John Loughney, Rudiger Geib, Cheng Hong, Elena Scialpi, Pratic Bose, Martin Stiemerling and Luis Cordeiro for their useful comments and suggestions.</t>
</section>
<!-- End of Acknowledgements Section -->
</middle>
<!-- End of Middel portion -->
<back>
<references title='Normative Reference'>
<reference anchor="nsis.gist">
<front>
<title>GIST: General Internet Signaling Transport</title>
<author initials="H." surname="Schulzrinne"
fullname="Schulzrinne H. and Hancock R.">
<organization />
</author>
<date month="July" year="2007" />
</front>
<seriesInfo name="Internet Draft" value="draft-ietf-nsis-ntlp-14" />
<seriesInfo name="Work in progress" value="" />
</reference>
<reference anchor="nsis.qosnslp">
<front>
<title>NSLP for Quality-of-Service Signaling</title>
<author initials="J." surname="Manner"
fullname="Manner J., et al.">
<organization />
</author>
<date month="July" year="2007" />
</front>
<seriesInfo name="Internet Draft" value="draft-ietf-nsis-qos-nslp-15" />
<seriesInfo name="Work in progress" value="" />
</reference>
<reference anchor="nsis.natfwnslp">
<front>
<title>NAT/Firewall NSIS Signaling Layer Protocol (NSLP)</title>
<author initials="M." surname="Stiemerling"
fullname="Stiemerling M., et al.">
<organization />
</author>
<date month="July" year="2007" />
</front>
<seriesInfo name="Internet Draft" value="draft-ietf-nsis-nslp-natfw-15" />
<seriesInfo name="Work in progress" value="" />
</reference>
<reference anchor="nsis.tunneling">
<front>
<title> NSIS Operation Over IP Tunnels</title>
<author initials="C." surname="Shen"
fullname="Shen C., et al.,">
<organization />
</author>
<date month="September" year="2007" />
</front>
<seriesInfo name="Internet Draft" value="draft-ietf-nsis-tunnel-03" />
<seriesInfo name="Work in Progress" value="" />
</reference>
<reference anchor="rfc2205.rsvp">
<front>
<title>Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification</title>
<author initials="B." surname="Braden"
fullname="Braden, B., Zhang, L., Berson, S., Herzog, S., and Jamin S.">
<organization />
</author>
<date month="September" year="1997" />
</front>
<seriesInfo name="RFC2205" value="" />
</reference>
<reference anchor="rfc3344.mip4">
<front>
<title>IP Mobility Support for IPv4</title>
<author initials="C." surname="Perkins"
fullname="Perkins C., Ed.">
<organization />
</author>
<date month="August" year="2002" />
</front>
<seriesInfo name="RFC3344" value="" />
</reference>
<reference anchor="rfc3775.mip6">
<front>
<title>Mobility Support in IPv6</title>
<author initials="D." surname="Johnson"
fullname="Johnson D., Perkins C. and Arkko J.">
<organization />
</author>
<date month="June" year="2004" />
</front>
<seriesInfo name="RFC3775" value="" />
</reference>
<reference anchor="rfc3726.req4sig">
<front>
<title>Requirements for Signaling Protocols</title>
<author initials="M." surname="Brunner, (Ed)"
fullname="Brunner, (Ed)">
<organization />
</author>
<date month="June" year="2004" />
</front>
<seriesInfo name="RFC3726" value="" />
</reference>
</references>
<!-- End of Normative Reference -->
<!-- Start of Informative Reference -->
<references title='Informative References'>
<reference anchor="rfc3753.mobterm">
<front>
<title>Mobility Related Terminology</title>
<author initials="J." surname="Manner"
fullname="Manner, J. and Kojo, M.">
<organization />
</author>
<date month="June" year="2004" />
</front>
<seriesInfo name="RFC3753" value="" />
</reference>
<reference anchor="monami.mulcoareg">
<front>
<title>Multiple Care-of-Address Registration</title>
<author initials="R." surname="Wakikawa"
fullname="Wakikawa, R.">
<organization />
</author>
<date month="July" year="2007" />
</front>
<seriesInfo name="Internet Draft" value="draft-ietf-monami6-multiplecoa-03" />
<seriesInfo name="Work in progress" value="" />
</reference>
<!-- Referred by Security Consideration
<reference anchor="individual.nsissid">
<front>
<title>NSIS Authentication, Authorization and Accounting Issues</title>
<author initials="H." surname="Tschofenig"
fullname="Tschofenig, H.">
<organization />
</author>
<date month="June" year="2003" />
</front>
<seriesInfo name="Internet Draft" value="draft-tschofenig-nsis-sid-00" />
<seriesInfo name="Work in progress" value="" />
</reference>
-->
<!-- Referred by Security Consideration
<reference anchor="individual.nsisaaa">
<front>
<title>NSIS Authentication, Authorization and Accounting Issues</title>
<author initials="H." surname="Tschofenig"
fullname="Tschofenig, H.">
<organization />
</author>
<date month="March" year="2003" />
</front>
<seriesInfo name="Internet Draft" value="draft-tschofenig-nsis-aaa-issues-01" />
<seriesInfo name="Work in progress" value="" />
</reference>
-->
</references>
<!-- End of Informative Reference -->
<section title="" anchor="Appendix.A">
<t>The mobility occurs due to the change of the network attachment point, but the generic route changes is associated with load sharing, load balancing, or a link (or node) failure. These cause divergence (or convergence) between the old path along which state has already been installed and the new path along which data forwarding will actually happen.</t>
<t>The route changes brings on the change of signaling topology and it results in difference according to the types of route changes (e.g., the route changes or mobility). The route changes generally forms two common paths, an old path, and a new path, where the old path and the new path begin to diverge from one common path and afterward to converge to another common path for each direction of signaling flows (e.g., downstream or upstream flows) as shown in <xref target="fig.DCRN.UCRN" /></t>
<figure title="The topology for NSIS signaling in case of the route changes" anchor="fig.DCRN.UCRN">
<preamble></preamble>
<artwork>
<![CDATA[
Old path
+---+ +---+
^ --->|NE | ... |NE | ------V
common path ^ +---+ +---+ V common path
+--+ +----+ +----+ +--+
|S |-----> |DCRN| |DCRN| -------> |R |
| | | | | | | |
+--+ +----+ New path +----+ +--+
V +---+ +---+ ^
V --->|NE | ... |NAR| ------^
+---+ +---+
=======(downstream signaling followed by data flows) ======>
(a) The topology for downstream NSIS signaling flow after
route changes
Old path
+---+ +---+
v <---|NE | ... |NE | ----- ^
common path v +---+ +---+ ^ common path
+--+ +----+ +----+ +--+
|S |<----- |UCRN| |UCRN| <------- |R |
| | | | | | | |
+--+ +----+ New path +----+ +--+
^ +---+ +---+ v
^ <---|NE | ... |NAR| ----- v
+---+ +---+
<=====(upstream signaling followed by data flows) ======
(b) The topology for upstream NSIS signaling flow after
route changes
]]>
</artwork>
</figure>
</section>
<!--End of Appendix.A -->
<!--End of Appendix -->
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-22 23:03:12 |