| RFC : | rfc5980 |
| Title: | |
| Date: | March 2011 |
| Status: | INFORMATIONAL |
Internet Engineering Task Force (IETF) T. Sanda, Ed.
Request for Comments: 5980 Panasonic
Category: Informational X. Fu
ISSN: 2070-1721 University of Goettingen
S. Jeong
HUFS
J. Manner
Aalto University
H. Tschofenig
Nokia Siemens Networks
March 2011
NSIS Protocol Operation in Mobile Environments
Abstract
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 document discusses the effects mobility can cause
to the Next Steps in Signaling (NSIS) protocol suite, and shows how
the NSIS protocols operate in different scenarios with mobility
management protocols.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5980.
Sanda, et al. Informational [Page 1]
RFC 5980 NSIS Signaling in Mobility March 2011
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Sanda, et al. Informational [Page 2]
RFC 5980 NSIS Signaling in Mobility March 2011
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Notation and Terminology . . . . . . . . . . . . 4
3. Challenges with Mobility . . . . . . . . . . . . . . . . . . . 5
4. Basic Operations for Mobility Support . . . . . . . . . . . . 8
4.1. General Functionality . . . . . . . . . . . . . . . . . . 8
4.2. QoS NSLP . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3. NATFW NSLP . . . . . . . . . . . . . . . . . . . . . . . . 12
4.4. Localized Signaling in Mobile Scenarios . . . . . . . . . 13
4.4.1. CRN Discovery . . . . . . . . . . . . . . . . . . . . 15
4.4.2. Localized State Update . . . . . . . . . . . . . . . . 15
5. Interaction with Mobile IPv4/v6 . . . . . . . . . . . . . . . 16
5.1. Interaction with Mobile IPv4 . . . . . . . . . . . . . . . 17
5.2. Interaction with Mobile IPv6 . . . . . . . . . . . . . . . 19
5.3. Interaction with Mobile IP Tunneling . . . . . . . . . . . 20
5.3.1. Sender-Initiated Reservation with Mobile IP Tunnel . . 20
5.3.2. Receiver-Initiated Reservation with Mobile IP
Tunnel . . . . . . . . . . . . . . . . . . . . . . . . 23
5.3.3. CRN Discovery and State Update with Mobile IP
Tunneling . . . . . . . . . . . . . . . . . . . . . . 24
6. Further Studies . . . . . . . . . . . . . . . . . . . . . . . 25
6.1. NSIS Operation in the Multihomed Mobile Environment . . . 25
6.1.1. Selecting the Best Interface(s) or CoA(s) . . . . . . 26
6.1.2. Differentiation of Two Types of CRNs . . . . . . . . . 27
6.2. Interworking with Other Mobility Protocols . . . . . . . . 28
6.3. Intermediate Node Becomes a Dead Peer . . . . . . . . . . 29
7. Security Considerations . . . . . . . . . . . . . . . . . . . 29
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 29
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 30
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 30
10.1. Normative References . . . . . . . . . . . . . . . . . . . 30
10.2. Informative References . . . . . . . . . . . . . . . . . . 30
1. Introduction
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 General Internet Signaling Transport (GIST)
message routing information or Message Routing Information (MRI)
[RFC5971]). Local mobility usually does not cause the change of the
global IP addresses, but affects the routing paths within the local
access network.
The NSIS protocol suite consists of two layers: the NSIS Transport
Layer Protocol (NTLP) and the NSIS Signaling Layer Protocol (NSLP).
The General Internet Signaling Transport (GIST) [RFC5971] implements
Sanda, et al. Informational [Page 3]
RFC 5980 NSIS Signaling in Mobility March 2011
the NTLP, which is a protocol that is independent of the signaling
application and that transports service-related information between
neighboring GIST nodes. Each specific service has its own NSLP
protocol; currently there are two specified NSLP protocols, the QoS
NSLP [RFC5974] and the Network Address Translator / Firewall (NAT/FW)
NSLP [RFC5973].
The goals of this document 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 fulfill the
requirements regarding mobility set forth in [RFC3726]. In general,
the NSIS protocols work well in mobile environments. 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. Additional information
and mobility-specific enhanced operations, e.g., operations with
crossover node (CRN), are also introduced.
This document 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.
2. Requirements Notation and Terminology
The terminology in this document is based on [RFC5971] and [RFC3753].
In addition, the following terms are used. Note that in this
document, 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'.
(1) Downstream
The direction from a data sender towards the data receiver.
(2) Upstream
The direction from a data receiver towards the data sender.
Sanda, et al. Informational [Page 4]
RFC 5980 NSIS Signaling in Mobility March 2011
(3) Crossover Node (CRN)
A Crossover Node is a node that for a given function is a merging
point of two or more paths belonging to flows of the same session
along which states are installed.
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, where we assume that the Mobile Node (MN) is
the data sender.
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.
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.
In general, the DCRN and the UCRN may be different due to the
asymmetric characteristics of routing, although the data receiver is
the same.
(4) State Update
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.
Upstream State Update: State Update for the upstream signaling
flow.
Downstream State Update: State Update for the downstream signaling
flow.
3. Challenges with Mobility
This section identifies problems that are caused by mobility and
affect the operations of NSIS protocol suite.
1. Change of route and possible change of the MN's IP address
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. Traditional route changes usually do not
cause address changes of the flow endpoints. When an IP address
Sanda, et al. Informational [Page 5]
RFC 5980 NSIS Signaling in Mobility March 2011
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, firewall rules, NAT
bindings, and QoS reservations that are already installed 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.
2. Double state problem
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 separate
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., 90 s 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 did not
yet expire.
3. End-to-end signaling and frequency of route changes
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.
4. Identification of the crossover node
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
change. In this situation, the crossover 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 affected part of the network.
5. Upstream State Update vs. Downstream State Update
Due to the asymmetric nature of Internet routing, the upstream and
downstream paths are likely not to be exactly the same. Therefore,
state update needs to be handled independently for upstream and
downstream paths.
Sanda, et al. Informational [Page 6]
RFC 5980 NSIS Signaling in Mobility March 2011
6. Upstream signaling
If the MN is the receiver and moves to a new point of attachment, it
is difficult to signal upstream towards the Correspondent Node (CN).
New signaling states have to be established along the new path, but
for a path-coupled Message Routing Method (MRM), this has to be
initiated in downstream direction. So, NTLP signaling state in the
upstream direction cannot be initiated by the MN, i.e., GIST cannot
easily send a Query in the upstream direction (there is an upstream
Q-mode, but this is only applicable in a limited scope). The use of
additional protocols such as application-level signaling (e.g,
Session Initiation Protocol (SIP)) or mobility management signaling
(e.g., Mobile IP) may help to trigger NSLP and NTLP signaling from
the CN side in the downstream direction though.
7. Authorization issues
The procedure of State Update may be initiated by the MN, the CN, or
even nodes within the network (e.g., crossover node, Mobility Anchor
Point (MAP) in Hierarchical Mobile IP (HMIP)). This State Update on
behalf of the MN raises authorization issues about the entity that is
allowed to make these state modifications.
8. Dead peer and invalid NSIS Receiver (NR) problem
When the MN is on the path of a signaling exchange, after handover
the old Access Router (AR) cannot forward NSLP messages towards 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
NSIS Receiver (NR) problem'.
9. IP-in-IP encapsulation
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 through 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
Sanda, et al. Informational [Page 7]
RFC 5980 NSIS Signaling in Mobility March 2011
can be discovered on the tunneling path. It enables NSIS protocols
to perform the 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. Furthermore, tunneling
adds additional IP header as overhead that must be taken into account
by QoS NSLP, for example, when resources must be reserved
accordingly. So an NSLP must usually be aware whether tunneling or
route optimization is actually used for a flow [RFC5979].
4. Basic Operations for Mobility Support
This section presents the basic operations of the NSIS protocol suite
after mobility-related route changes. Details of the operation of
Mobile IP with respect to NSIS protocols are discussed in the
subsequent section.
4.1. General Functionality
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 also effectively solves a typical problem with certain
signaling protocols, where protocol state is identified by flow
endpoints, and when flow endpoint addresses change, the whole session
state becomes invalid.
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 usually cannot be
avoided since new information for proper data flow identification
must be provided all the way between the data sender and receiver,
e.g., in order to update filters, QoS profiles, or other flow-related
session data.
GIST provides NSLPs with an identifier of the next signaling peer,
the Source Identification Information (SII) handle. When this SII-
Handle changes, the NSLP knows a routing change has happened. Yet,
Sanda, et al. Informational [Page 8]
RFC 5980 NSIS Signaling in Mobility March 2011
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.
When a path changes, the session information on the old path needs to
be removed. Normally, the information is released when the session
timer is expired after a routing change. But the NSLP running on the
end-host or the CRN, depending on the direction of the session, may
use the SII-Handle (provided by GIST) to explicitly 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.
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 are not 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 endpoints, and they can decide whether or not
the signaling actually succeeded.
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.
In some cases, the NSLP must be aware whether tunneling is used,
since additional tunneling overhead must be taken into account, e.g.,
for resource reservations, etc.
4.2. QoS NSLP
Figure 1 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 needs to acquire the new Care-of Address
(CoA) and update the path coupled MRI accordingly. Then, the MN
issues towards the CN a QoS NSLP RESERVE message that carries the
unique session ID and other identification information for the
session, as well as the reservation requirements (steps (1)-(4) in
Figure 1). 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
Sanda, et al. Informational [Page 9]
RFC 5980 NSIS Signaling in Mobility March 2011
path support the required QoS, the CN in turn responds with a
RESPONSE message to confirm the reservation (steps (5)-(6) in
Figure 1).
In a bidirectional tunneling case, the only difference is that the
RESERVE message should be sent to the home agent (HA) instead of the
CN, and the node that responds with a RESPONSE should be the HA
instead of the CN, too. More details are given in Section 5.
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. Also, the destination of the NSLP
signaling shall follow the Mobile IP data path using path-coupled
signaling.
In this process, the obsoleted state in the old path is not
explicitly released because the state can be released by timer
expiration. To speed up the process, it may be possible to localize
the signaling. When the RESERVE message reaches a node, depicted as
CRN in this document (step (2) in Figure 1), 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 (step (9) in
Figure 1). The QoS NSIS Entity (QNE) adjacent to the MN's old
position stops the NOTIFY message (step (10) in Figure 1) and sends a
RESERVE message (with Teardown bit set) towards the CN to release the
obsoleted state (step (11) in Figure 1). This RESERVE with tear
message is stopped by the CRN (step (12) in Figure 1). The
Reservation Sequence Number (RSN) is used in the messages to
distinguish the order of the signaling. More details are given in
Section 4.4
Sanda, et al. Informational [Page 10]
RFC 5980 NSIS Signaling in Mobility March 2011
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) | | | |
| | | | | | |
Figure 1: Example Basic Handover Signaling in the QoS NSLP
Further cases to consider are:
* receiver-initiated reservation if MN is sender
* sender-initiated reservation if MN is receiver
* receiver-initiated reservation if MN is receiver
In the first case, the MN can easily initiate a new QUERY along the
new path after movement, thereby installing signaling state and
eventually eliciting a new RESERVE from the CN in upstream direction.
Similarly, the second and third cases require the CN to initiate a
RESERVE or QUERY message respectively. The difficulty in both cases
is, however, to let the CN know that the MN has moved. Because the
MN is the receiver, it cannot simply use an NSLP message to do so,
because upstream signaling is not possible in this case (cf. Section
3, Upstream Signaling).
Sanda, et al. Informational [Page 11]
RFC 5980 NSIS Signaling in Mobility March 2011
4.3. NATFW NSLP
Figure 2 illustrates an example of NATFW NSLP signaling in a Mobile
IPv6 route optimization case, for a data flow from the MN to the CN.
The difference to the QoS NSLP is that for the NATFW NSLP only the
NSIS initiator (NI) can update the signaling session, in any case.
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 NATFW NSLP CREATE message towards the CN, that
carries the unique session ID and other identification information
for the session (steps (1)-(4) in Figure 2). Upon receipt of the
CREATE message, the NATFW NSLP nodes (which will be discovered by the
underlying NTLP) establish the corresponding NATFW 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 NATFW NSLP nodes along the path accept the
required NAT/firewall configuration, the CN in turn responds with a
RESPONSE message, to confirm the configuration (steps (5)-(8) in
Figure 2).
In a bidirectional tunneling case, the only difference is that the
CREATE message should be sent to the HA instead of the CN, and the
node that responds with a RESPONSE should be the HA instead of the CN
too.
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.
In this process, the obsoleted state in the old path is not
explicitly released because the state can be released by timer
expiration. To speed up the process, when the CREATE message reaches
a node, depicted as CRN in this document (step (2) in Figure 2),
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
(steps (9)-(10) in Figure 2). When the NI notices this, it sends a
CREATE message towards the CN to release the obsoleted state (steps
(11)-(12)) in Figure 2).
Sanda, et al. Informational [Page 12]
RFC 5980 NSIS Signaling in Mobility March 2011
MN NI MN NF1 NF2 NF3 CN
(CoA1) | (CoA2) | (CRN) | |
| | | | | | |
| | | | | | |
| | |CREATE | | | |
| | |------->| | | |
| | | (1) |CREATE | | |
| | | |--------->| | |
| | | | (2) |CREATE | |
| | | | |------->| |
| | | | | (3) |CREATE |
| | | | | |------->|
| | | | NOTIFY| | (4) |
| | | |<---------| | |
| | | NOTIFY| (9) | | |
| |<------------| | | |
| | | (10) | | | |
| |CREATE(CoA2) | | | |
| |------------>| | | |
| | | (11) |CREATE(CoA2) | |
| | | |--------->| | |
| | | | (12) | |RESPONSE|
| | | | | |<-------|
| | | | |RESPONSE| (5) |
| | | | RESPONSE|<-------| |
| | |RESPONSE|<---------| (6) | |
| | |<------ | (7) | | |
| | | (8) | | | |
| | | | | | |
| | | | | | |
Figure 2: Example of NATFW NSLP Operation
4.4. Localized Signaling in Mobile Scenarios
This section describes detailed CRN operations. As described in
previous sections, CRN operations are informational.
As shown in Figure 3, mobility generally causes the signaling path to
either converge or diverge depending on the direction of each
signaling flow.
Sanda, et al. Informational [Page 13]
RFC 5980 NSIS Signaling in Mobility March 2011
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 ^
<=====(upstream signaling followed by data flows) =====
(a) The topology for upstream NSIS signaling flow due to
mobility (in the case that the MN is a data sender)
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 ^
====(downstream signaling followed by data flows) ======>
(b) The topology for downstream NSIS signaling flow due to
mobility (in the case that the MN is a data sender)
Note: OAR - old access router
NAR - new access router
Figure 3: The Topology for NSIS Signaling Caused by Mobility
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-
Sanda, et al. Informational [Page 14]
RFC 5980 NSIS Signaling in Mobility March 2011
establishment of NSIS signaling may be localized when route changes
(including mobility) occur; this is 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 to only the
affected portion of the signaling path because the signaling path in
the wireless access network usually changes only partially.
4.4.1. CRN Discovery
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 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. Also, the QNE realizes it is
implicitly the CRN.
4.4.2. Localized State Update
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
Section 4.4.1. The MRI from the DCRN to the CN (i.e., common path)
is updated by the RESERVE message. The DCRN may also send a NOTIFY
with "Route Change" (0x02) to the previous upstream peer. The NOTIFY
is forwarded hop-by-hop and reaches the edge QNE (i.e., QNE1 in
Figure 1). After the QNE is aware that the MN as QNI has disappeared
(how this can be noticed is out of scope for NSIS, yet, e.g., GIST
will eventually know 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 [RFC5971]. Note that the sender-initiated approach leads to
faster setup than the receiver-initiated approach as in RSVP
[RFC2205].
In the scenario of an upstream State Update, there are two possible
methods for state update. One is the CN (or the HA, Gateway Foreign
Agent (GFA), or MAP) sends the refreshing RESERVE message toward the
MN to perform State Update upon receiving the trigger (e.g., Mobile
IP (MIP) binding update). The UCRN is discovered implicitly by the
CN-initiated signaling along the common path as described in
Section 4.4.1. When the refreshing RESERVE reaches to the adjacent
QNE of UCRN, the QNE sends back a RESPONSE saying "Reduced refreshes
not supported; full QSPEC required" (0x03). Then, the UCRN sends the
RESERVE with full QSPEC towards the MN to set up a new reservation.
Sanda, et al. Informational [Page 15]
RFC 5980 NSIS Signaling in Mobility March 2011
The UCRN may also send a tearing RESERVE to the previous downstream
peer. The tearing RESERVE is forwarded hop-by-hop and reaches the
edge QNE. After the QNE is aware that the MN as QNI has disappeared,
the QNE drops the tearing peer. Another method is: if a GIST hop is
already established on the new path (e.g., by QUERY from the CN, or
the HA, GFA, or MAP) when MN gets a hint from GIST that routing has
changed, the MN sends a NOTIFY upstream saying "Route Change" (0x02).
When the NOTIFY hits the UCRN, the UCRN is aware that the NOTIFY is
for a known session and comes from a new SII-Handle. Then, the UCRN
sends towards the MN a RESERVE with a new RSN and an RII. By
receiving the RESERVE, the MN replies with a 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 has disappeared, the QNE drops
the tearing peer.
The State Update on the common path to reflect the changed MRI brings
issues on the end-to-end signaling addressed in Section 3. Although
the State Update over the common path does not give rise to re-
processing of AAA and admission control, it may lead to increased
signaling overhead and latency.
One of the goals of the State Update is to avoid the double
reservation on the common path as described in Section 3. The double
reservation problem on the common path can be solved by establishing
a signaling association using a unique SID and by updating the packet
classifier / MRI. In this case, even though the flows on the common
path have different MRIs, they refer to the same NSLP state.
5. Interaction with Mobile IPv4/v6
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 MRI [RFC5971] contains flow
addresses and will change if the CoA changes. This makes an impact
on some NSLPs such as QoS NSLP and NAT/FW NSLP.
QoS NSLP must be mobility-aware because it needs to care about the
resources on the actual current path, and sending a new RESERVE or
QUERY for the new path. Applications on top of Mobile IP communicate
along logical flows that use home addresses, whereas QoS NSLP has to
be aware of the actual flow path, e.g., whether the flow is currently
tunneled or route-optimized, etc. QoS NSLP may have to obtain
current link properties; especially there may be additional overhead
due to mobility header extensions that must be taken into account in
QSPEC (e.g., the m parameter in the traffic model (TMOD); see
[RFC5975]). Therefore, NSLPs must interact with mobility management
implementations in order to request information about the current
Sanda, et al. Informational [Page 16]
RFC 5980 NSIS Signaling in Mobility March 2011
flow address (CoAs), source addresses, tunneling, or overhead.
Furthermore, an implementation must select proper interface addresses
in the natural language interface (NLI) in order to ensure that a
corresponding Messaging Association is established along the same
path as the flow in the MRI. Moreover, the home agent needs to
perform additional actions (e.g., reservations) for the tunnel. If
the home agent lacks support of a mobility-aware QoS NSLP, a missing
tunnel reservation is usually the result. Practical problems may
occur in situations where a home agent needs to send a GIST query
(with S-flag=1) towards the MN's home address and the query is not
tunneled due to route optimization between HA and MN: the query will
be wrongly intercepted by QNEs within the tunnel.
NAT/FW box needs to be configured before MIP signaling, hence NAT/FW
signaling will have to be performed to allow Return Routability Test
(RRT) and Binding Update (BU) / Binding Acknowledgement (BA) messages
to traverse the NAT/FWs in the path. After RRT and BU/BA messages
are completed, more NAT/FW signaling needs to be performed for
passing the data. Optimized version can include a combined NAT/FW
message to cover both RRT and BU/BA messages pattern. However, this
may require NAT/FW NSLP to do a slight update to support carrying
multiple NAT/FW rules in one signaling round trip.
This section analyzes NSIS operation with the tunneled route case
especially for QoS NSLP.
5.1. Interaction with Mobile IPv4
In Mobile IPv4 [RFC5944], the data flows are forwarded based on
triangular routing, and an MN retains a new CoA from the Foreign
Agent (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 acts 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 the 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.
Figure 4 (a) to (e) show how the NSIS signaling flows depend on the
direction of the data flows and the routing methods.
Sanda, et al. Informational [Page 17]
RFC 5980 NSIS Signaling in Mobility March 2011
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 CoA
CN HA (FL) MN
|IPv4(normal ) | | |
|-------------->| | |
| | MIPv4 (tunnel) | |
| |------------------------------->|
| | | |
(e) MIPv4: CN-->MN with co-located CoA
Figure 4: NSIS Signaling Flows under Different Mobile IPv4 Scenarios
When an MN (as a signaling sender) arrives at a new FA and the
corresponding binding process is completed (Figure 4 (a), (b), and
(c)), the MN performs the CRN discovery (DCRN) and the State Update
toward the CN (as described in Section 4) to establish the NSIS state
Sanda, et al. Informational [Page 18]
RFC 5980 NSIS Signaling in Mobility March 2011
along the new path between the MN and the CN. In case the reverse
tunnel is not used (Figure 4 (a)), a new NSIS state is established on
the direct path from the MN to the CN. If the reverse tunnel and FA
CoA are used (Figure 4 (b)), a new NSIS state is established along a
tunneling path from the FA to the HA separately from the 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 (Figure 4 (c)), the NSIS signaling for the DCRN
discovery and for the State Update is the same as the case of using
the 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 the tunnel
endpoints is the MN, not the FA.
When an MN (as a signaling receiver) arrives at a new FA and the
corresponding binding process is completed (Figure 4 (d) and (e)),
the MN sends a NOTIFY message to the signaling sender, i.e., the CN.
In case the FA CoA is used (Figure 4 (d)), the CN initiates an 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
reach 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 the tunneling path is also separately
performed if necessary. In case co-located CoA is used (Figure 4
(d)), the NSIS signaling for the UCRN discovery and for the State
Update is also the same as the case of using the FA CoA, above except
for the endpoint of the tunneling path from the HA to the MN.
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.
5.2. Interaction with Mobile IPv6
Unlike Mobile IPv4, with Mobile IPv6 [RFC3775], the FA is not
required on the data path. If an MN moves to a 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.
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 Mobile IPv4 with the 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 Section 4
are applicable to this case.
Sanda, et al. Informational [Page 19]
RFC 5980 NSIS Signaling in Mobility March 2011
5.3. Interaction with Mobile IP Tunneling
In this section, we assume that the MN acts as an NI and the CN acts
as an NR in interworking between Mobile IP and NSIS signaling.
Scenarios for interaction with Mobile IP tunneling vary depending on:
- Whether a tunneling entry point (Tentry) is an MN or other node.
For a Mobile IPv4 co-located CoA or Mobile IPv6 CoA, Tentry is an
MN. For a Mobile IPv4 FA CoA, Tentry is an FA. In both cases, an
HA is the tunneling exit point (Texit).
- Whether the mode of QoS NSLP signaling is sender-initiated or
receiver-initiated.
- Whether the operation mode over the tunnel is with preconfigured
QoS sessions or with dynamically created QoS sessions as described
in [RFC5979].
The following subsections describe sender-initiated and receiver-
initiated reservations with Mobile IP tunneling, as well as CRN
discovery and State Updates with Mobile IP tunneling.
5.3.1. Sender-Initiated Reservation with Mobile IP Tunnel
The following scenario assumes that an FA is a Tentry. However, the
procedure is the same when an MN is a Tentry if the MN and the FA are
considered the same node.
- When an MN moves into a new network attachment point, QoS NSLP in
the MN initiates the RESERVE (end-to-end) message to start the
State Update procedure. The GIST below the QoS NSLP adds the GIST
header and then sends the encapsulated RESERVE message to peer
GIST node with the corresponding QoS NSLP. In this case, the peer
GIST node is an FA if the FA is an NSIS-aware node. The FA is one
of the endpoints of Mobile IP tunneling: Tentry. For proper NSIS
tunneling operation, a Mobile IP endpoint is required to be NSIS
tunneling aware. In case of interaction with tunnel signaling
originated from the FA, there can be two scenarios depending on
whether or not the tunnel already has preconfigured QoS sessions.
In the former case, the FA map end-to-end QoS signaling requests
directly to existing tunnel sessions. In the latter case, the FA
dynamically initiates and maintains tunnel QoS sessions that are
then associated with the corresponding end-to-end QoS sessions.
[RFC5979].
Sanda, et al. Informational [Page 20]
RFC 5980 NSIS Signaling in Mobility March 2011
- Figure 5 shows the typical NSIS operation over tunnels with
preconfigured QoS sessions. Both the FA and the HA are configured
with information about the Flow ID of the tunnel QoS session.
Upon receiving a RESERVE message from the MN, the FA checks tunnel
QoS configuration, and determines whether and how this end-to-end
session can be mapped to a preconfigured tunnel session. The FA
then tunnels the RESERVE message to the HA. The CN replies with a
RESPONSE message which arrives at the HA, the FA, and the MN.
- Figure 6 shows the typical NSIS operation over tunnels with
dynamically created QoS sessions. When the FA receives an end-to-
end RESERVE message from the MN, the FA chooses the tunnel Flow
ID, creates the tunnel session, and associates the end-to-end
session with the tunnel session. The FA then sends a tunnel
RESERVE' message (matching the request of the end-to-end session)
towards the HA to reserve tunnel resources. The tunnel RESERVE'
message is processed hop-by-hop inside the tunnel for the flow
identified by the chosen tunnel Flow ID, while the end-to-end
RESERVE message passes through the tunnel intermediate nodes
(Tmid). When these two messages arrive at the HA, the HA creates
the reservation state for the tunnel session, and sends a tunnel
RESPONSE' message to the FA. At the same time, the HA updates the
end-to-end RESERVE message based on the result of the tunnel
session reservation and forwards the end-to-end RESERVE message
along the path towards the CN. When the CN receives the end-to-
end RESERVE message, it sends an end-to-end RESPONSE message back
to the MN.
More detailed operations are specified in [RFC5979].
Sanda, et al. Informational [Page 21]
RFC 5980 NSIS Signaling in Mobility March 2011
MN (Sender) FA (Tentry) Tmid HA (Texit) CN (Receiver)
| | | | |
| RESERVE | | | |
+------------->| | | |
| | RESERVE | |
| +--------------------------->| |
| | | | RESERVE |
| | | +------------->|
| | | | RESPONSE |
| | | |<-------------+
| | RESPONSE | |
| |<---------------------------+ |
| RESPONSE | | | |
|<-------------+ | | |
| | | | |
Figure 5: Sender-Initiated QoS NSLP over Tunnel with Preconfigured
QoS Sessions
MN (Sender) FA (Tentry) Tmid HA (Texit) CN (Receiver)
| | | | |
| RESERVE | | | |
+------------->| | | |
| | RESERVE' | | |
| +=============>| | |
| | | RESERVE' | |
| | +=============>| |
| | RESERVE | |
| +---------------------------->| |
| | | RESPONSE' | |
| | |<=============+ |
| | RESPONSE' | | |
| |<=============+ | |
| | | | RESERVE |
| | | +------------->|
| | | | RESPONSE |
| | | |<-------------+
| | RESPONSE | |
| |<----------------------------+ |
| RESPONSE | | | |
|<-------------+ | | |
| | | | |
Figure 6: Sender-Initiated QoS NSLP over Tunnel with Dynamically
Created QoS Sessions
Sanda, et al. Informational [Page 22]
RFC 5980 NSIS Signaling in Mobility March 2011
5.3.2. Receiver-Initiated Reservation with Mobile IP Tunnel
Figures 7 and 8 show examples of receiver-initiated operation over
Mobile IP tunnel with preconfigured and dynamically created QoS
sessions, respectively. The Basic Operation is the same as the
sender-initiated case.
MN (Sender) FA (Tentry) Tmid HA (Texit) CN (Receiver)
| | | | |
| QUERY | | | |
+------------->| | | |
| | QUERY | |
| +--------------------------->| |
| | | | QUERY |
| | | +------------->|
| | | | RESERVE |
| | | |<-------------+
| | RESERVE | |
| |<---------------------------+ |
| RESERVE | | | |
|<-------------+ | | |
| RESPONSE | | | |
+------------->| | | |
| | RESPONSE | |
| +--------------------------->| |
| | | | RESPONSE |
| | | +------------->|
| | | | |
Figure 7: Receiver-Initiated QoS NSLP over Tunnel with Preconfigured
QoS Sessions
Sanda, et al. Informational [Page 23]
RFC 5980 NSIS Signaling in Mobility March 2011
MN (Sender) FA (Tentry) Tmid HA (Texit) CN (Receiver)
| QUERY | | | |
+------------->| | | |
| | QUERY' | | |
| +=============>| | |
| | | QUERY' | |
| | +=============>| |
| | | RESPONSE' | |
| | |<=============+ |
| | RESPONSE' | | |
| |<=============+ | |
| | QUERY | |
| +---------------------------->| |
| | | | QUERY |
| | | +------------->|
| | | | RESERVE |
| | | |<-------------+
| | | RESERVE' | |
| | |<=============+ |
| | RESERVE' | | |
| |<=============+ | |
| | RESERVE | |
| |<----------------------------+ |
| | RESPONSE' | | |
| +=============>| | |
| | | RESPONSE' | |
| | +=============>| |
| RESERVE | | | |
|<-------------+ | | |
| RESPONSE | | | |
+------------->| | | |
| | RESPONSE | |
| +---------------------------->| |
| | | | RESPONSE |
| | | +------------->|
| | | | |
Figure 8: Receiver-Initiated QoS NSLP over Tunnel with Dynamically
Created QoS Session
5.3.3. CRN Discovery and State Update with Mobile IP Tunneling
If a tunnel is in the mode of using dynamically created QoS sessions,
the Mobile IP tunneling scenario can include two types of CRNs, i.e.,
a CRN on an end-to-end path and a CRN on a tunneling path. If a
Sanda, et al. Informational [Page 24]
RFC 5980 NSIS Signaling in Mobility March 2011
tunnel is in the mode of using preconfigured QoS sessions, it can
only have CRNs on end-to-end paths. CRN discovery and State Update
for these two paths are operated independently.
CRN discovery for an end-to-end path is initiated by the MN by
sending a RESERVE (sender-initiated case) or QUERY (receiver-
initiated case) message. As the MN uses HoA as the source address
even after handover, a CRN is found by normal route change process
(i.e., the same SID and Flow ID, but a different SII-Handle). If an
HA is QoS NSLP aware, the HA is found as the CRN. The CRN initiates
the tearing-down process on the old path as described in [RFC5974].
CRN discovery for the tunneling path is initiated by Tentry by
sending a RESERVE' (sender-initiated case) or QUERY' (receiver-
initiated case) message. The route change procedures described in
Section 4 are applicable to this case.
The end-to-end state inside the tunnel should not be torn down until
all states inside the tunnel have been torn from the implementation
perspective. However, detailed discussions are out of scope for this
document.
6. Further Studies
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 for this document. Detailed operations
in this section are just for future reference.
6.1. NSIS Operation in the Multihomed Mobile Environment
In multihomed mobile environments, multiple interfaces and addresses
(i.e., CoAs and HoAs) are available, so two major issues can be
considered. One is how to select or acquire the most appropriate
interface(s) and/or address(es) from the end-to-end QoS point of
view. The other is, when multiple paths are simultaneously used for
load-balancing purposes, how to differentiate and manage two types of
CRNs, i.e., the CRN between two ongoing paths (LB-CRN: Load Balancing
CRN) and the CRN between the old and new paths caused by the MN's
handover (HO-CRN: Handover CRN). This section introduces possible
approaches for these issues.
Sanda, et al. Informational [Page 25]
RFC 5980 NSIS Signaling in Mobility March 2011
6.1.1. Selecting the Best Interface(s) or CoA(s)
In the MIPv6 route optimization case, if registrations of multiple
CoAs are provided [RFC5648], the contents of QUERYs sent by candidate
CoAs can be used to select the best interface(s) or CoA(s).
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 the 'QoS Available'
object in the QUERY messages. Then, a RESERVE message is sent toward
the MN to reserve resources along the path that 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.
For a 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.
Sanda, et al. Informational [Page 26]
RFC 5980 NSIS Signaling in Mobility March 2011
|--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 | | |
|<=================->|<===================->|<=============>|
| | | | | | | | |
Figure 9: Receiver-Initiated Reservation in the Multihomed
Environment
6.1.2. Differentiation of Two Types of CRNs
When multiple interfaces of the MN are simultaneously used for load-
balancing purposes, a possible approach for distinguishing the LB-CRN
and HO-CRN will introduce an identifier to determine the relationship
between interfaces and paths.
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
Flow IDs as shown in (a) of Figure 10. Then, one of the interfaces
of the MN performs a handover and obtains a new CoA, and the MN will
try to establish a new path (say Path 3) with the new Flow ID, as
shown in (b) of Figure 10. 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, the SID is the same but the Flow IDs are different. Hence,
the CRN will not know if State Update is required. One possible
solution to solve this issue is to introduce a path classification
identifier, which shows the relationship between interfaces and
paths. For example, signaling messages and QNEs that belong to paths
from interface 1 and interface 2 carry the identifiers '00' and '02',
respectively. By having this identifier, the CRN between path 2 and
Sanda, et al. Informational [Page 27]
RFC 5980 NSIS Signaling in Mobility March 2011
path 3 will be able to determine whether it is an LB-CRN or HO-CRN.
For example, if path 3 carries '00', the CRN is an LB-CRN, and if
'01', the CRN is an HO-CRN.
+--+ 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
Figure 10: The Topology for NSIS Signaling in Multihomed Mobile
Environments
6.2. Interworking with Other Mobility Protocols
In mobility scenarios, the end-to-end signaling problem by the State
Update (unlike the problem of generic route changes) 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.
Sanda, et al. Informational [Page 28]
RFC 5980 NSIS Signaling in Mobility March 2011
In the interdomain handover, a possible way to mitigate the latency
penalty is to use the multihomed MN. It is also possible to allow
the NSIS protocols to interact with mobility protocols such as
Seamoby protocols (e.g., Candidate Access Router Discovery (CARD)
[RFC4066] and the Context Transfer Protocol (CXTP) [RFC4067]) and
Fast Mobile IP (FMIP). Another scenario is to use a peering
agreement that allows aggregation authorization to be performed for
aggregate reservation on an interdomain link without authorizing each
individual session. How these approaches can be used in NSIS
signaling is for further study.
6.3. Intermediate Node Becomes a Dead Peer
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 rediscovered
immediately by the CRN discovery procedure.
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.
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 addition, a more detailed analysis of interactions
with IP tunneling is left for future work.
7. Security Considerations
This document does not introduce new security concerns. The security
considerations pertaining to the NSIS protocol specifications,
especially [RFC5971], [RFC5973], and [RFC5974], 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 and CRNs.
8. Contributors
Sung-Hyuck Lee was the editor of early drafts of this document.
Since draft version 06, Takako Sanda has taken the editorship.
Many individuals have contributed to this document. Since it was not
possible to list them all in the authors section, this section was
created to have a sincere respect for those who contributed: Paulo
Sanda, et al. Informational [Page 29]
RFC 5980 NSIS Signaling in Mobility March 2011
Mendes, Robert Hancock, Roland Bless, Shivanajay Marwaha, and Martin
Stiemerling. Separating authors into two groups was done without
treating any one of them better (or worse) than others.
9. Acknowledgements
The authors would like to thank Byoung-Joon Lee, Charles Q. Shen,
Cornelia Kappler, Henning Schulzrinne, and Jongho Bang for
significant contributions in early drafts of this document. 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.
10. References
10.1. Normative References
[RFC3775] Johnson, D., "Mobility Support in IPv6", RFC3775 ,
June 2004.
[RFC5971] Schulzrinne, H. and R. Hancock, "GIST: General Internet
Signalling Transport", RFC 5971, October 2010.
[RFC5973] Stiemerling, M., Tschofenig, H., Aoun, C., and E. Davies,
"NAT/Firewall NSIS Signaling Layer Protocol (NSLP)",
RFC 5973, October 2010.
[RFC5974] Manner, J., Karagiannis, G., and A. McDonald, "NSIS
Signaling Layer Protocol (NSLP) for Quality-of-Service
Signaling", RFC 5974, October 2010.
[RFC5944] Perkins, C., Ed., "IP Mobility Support for IPv4, Revised",
RFC 5944, November 2010.
10.2. Informative References
[RFC2205] Braden, B., "Resource ReSerVation Protocol (RSVP) --
Version 1 Functional Specification", RFC2205 ,
September 1997.
[RFC3726] Brunner, (Ed), M., "Requirements for Signaling Protocols",
RFC3726 , June 2004.
[RFC3753] Manner, J., "Mobility Related Terminology", RFC3753 ,
June 2004.
Sanda, et al. Informational [Page 30]
RFC 5980 NSIS Signaling in Mobility March 2011
[RFC4066] Liebsch, M., "Candidate Access Router Discovery (CARD)",
RFC4066 , July 2005.
[RFC4067] Loughney, J., "Context Transfer Protocol (CXTP)",
RFC4067 , July 2005.
[RFC5648] Wakikawa, R., "Multiple Care-of-Address Registration",
RFC5648 , October 2009.
[RFC5975] Ash, G., Bader, A., Kappler, C., and D. Oran, "QSPEC
Template for the Quality-of-Service NSIS Signaling Layer
Protocol (NSLP)", RFC 5975, October 2010.
[RFC5979] Shen, C., Schulzrinne, H., Lee, S., and J. Bang, "NSIS
Operation over IP Tunnels", RFC 5979, March 2011.
Authors' Addresses
Takako Sanda (editor)
Panasonic Corporation
600 Saedo-cho, Tsuzuki-ku, Yokohama
Kanagawa 224-8539
Japan
Phone: +81 45 938 3056
EMail: sanda.takako@jp.panasonic.com
Xiaoming Fu
University of Goettingen
Computer Networks Group
Goldschmidtstr. 7
Goettingen 37077
Germany
Phone: +49 551 39 172023
EMail: fu@cs.uni-goettingen.de
Seong-Ho Jeong
Hankuk University of FS
Dept. of Information and Communications Engineering
89 Wangsan, Mohyun, Cheoin-gu
Yongin-si, Gyeonggi-do 449-791
Korea
Phone: +82 31 330 4642
EMail: shjeong@hufs.ac.kr
Sanda, et al. Informational [Page 31]
RFC 5980 NSIS Signaling in Mobility March 2011
Jukka Manner
Aalto University
Department of Communications and Networking (Comnet)
P.O. Box 13000
FIN-00076 Aalto
Finland
Phone: +358 9 470 22481
EMail: jukka.manner@tkk.fi
URI: http://www.netlab.tkk.fi/~jmanner/
Hannes Tschofenig
Nokia Siemens Networks
Linnoitustie 6
Espoo
02600
Finland
Phone: +358 50 4871445
EMail: Hannes.Tschofenig@nsn.com
Sanda, et al. Informational [Page 32]