Internet DRAFT - draft-hermann-casp-qos-mobility
draft-hermann-casp-qos-mobility
Internet-Draft S. Hermann
Expires: December 12, 2003 T. Chen
G. Schaefer
Technical University of Berlin
C. Fan
Siemens AG
June 13, 2003
QoS Resource Allocation in Mobile Networks with CASP
draft-hermann-casp-qos-mobility-00.txt
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This document discusses QoS resource allocation in mobile networks
with Cross-Application Signaling Protocol [1].CASP separates
signaling message delivery from the discovery of the next suitable
CASP node. When the discovery is done by scout messages, it may
introduce considerable latency in the (re-)registration procedure in
handover cases. Therefore, advanced discovery mechanisms are
recommended.
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To demonstrate the use of advanced discovery mechanisms, we enable
access routers to provide the information of the aggregate QoS value,
the next CASP node and optionally the price of provided services in
advertisements in addition to network topology information. By this
means, we can achieve seamless mobility and QoS provisioning in a
mobile access network because a mobile node can select the most
suited access point from several received advertisements for a (re-
)registration procedure. In this document, we describe the mechanism
and the message flows in both the case of general mobility management
using Mobile IPv6 (MIPv6) and the case of micro-mobility management
using Hierarchical MIPv6 (HMIPv6).
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Enhanced Advertisements . . . . . . . . . . . . . . . . . . . 6
2.1 Message Propagation . . . . . . . . . . . . . . . . . . . . . 6
2.2 Considerations of the Routers in the Access Network . . . . . 7
2.3 Message Format . . . . . . . . . . . . . . . . . . . . . . . . 9
3. QoS Signaling and Registration Process with MIPv6 . . . . . . 14
4. QoS Signaling and (Re-)registration Processes with HMIPv6 in
a Separate Signaling Manner . . . . . . . . . . . . . . . . . 17
5. QoS Signaling and Re-registration Processes with HMIPv6 in a
Combined Signaling Manner . . . . . . . . . . . . . . . . . . 21
6. Security Considerations . . . . . . . . . . . . . . . . . . . 23
References . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 24
Full Copyright Statement . . . . . . . . . . . . . . . . . . . 26
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1. Introduction
In high mobility scenarios, frequent handovers may result in a
significant degradation of QoS provisioning if the access network is
unable to provide enhanced solutions for prompt QoS re-
establishments. Most of the current approaches for signaling
protocols consider only the actions which have to be taken after a
handover occurs. Some newly proposed protocols use various ideas to
speed up the re-establishment of the reservation paths and handle the
specific mobility related events, e.g. changes of the IP address of
a mobile node. However, none of the protocols introduces mechanisms
for the preparation of a handover.
Several requirements have been identified for seamless handovers and
the fast re-establishment of QoS reservations:
o Bidirectional reservation. If the route is symmetric, it should
be feasible to set up reservation in both directions with a single
reservation message; if the route is asymmetric, a reservation
message from the originator should trigger an independent
signaling message from the responder.
o Path repair and re-establishment of reservations. The paths in a
mobility supporting access network usually change only partially
after a handover. Therefore, the protocol should support partial
repairs of the paths to avoid long distance end-to-end signaling
message exchanges between corresponding nodes.
o Reservation Range. The reservation range consists of a lower and
an upper bounds of QoS parameters e.g. bandwidth. The upper
bandwidth value represents the desired bandwidth while the lower
value is the acceptable bandwidth. If the network is not able to
satisfy the desired value, it can reserve as much as it can which
is greater than the acceptable value. Thus, the mobile node is
unnecessary to negotiate further with the network on the requested
QoS as happens when only one value in a QoS request.
o Modularity. The protocol should provide a modular architecture to
enable different functionalities flexibly.
o Endpoint identifier. The endpoint identifier must be independent
from identifiers which may change due to mobility, e.g. the IP
address.
o Security model. The Security model must provide an efficient and
secure solution.
All the above mentioned requirements are satisfied by the Cross-
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Application Signaling Protocol [1] (CASP). The CASP protocol is
split into two layers, a general purpose messaging layer (M-layer)
and several client layers for signaling applications like QoS, MIDCOM
etc. The messaging layer is used to establish session states with
session identifiers. These identifiers are independent from the IP
address of a node. Therefore they can be used to identify the
sessions from a mobile node easily, even after a change of the care-
of address due to a handover to another access router. CASP [2]
itself deals with it already. As soon as the mobile node detects a
route change due to mobility (e.g. based on a layer 2 trigger), it
triggers mobility related protocols. The mobility component may
trigger a CASP signaling message.
In CASP, signaling and discovery message delivery are separated. The
Scout protocol is used to discover the next suitable CASP node and
the required soft-state refresh interval if the next CASP node is
more than one network-layer hop away. It is only needed in case that
no other suitable means of discovering the next CASP node are
available. See [1] for reference. In environments with high
mobility, however, the discovery process with scout will increase a
considerable overall handover latency.
Additionally, the price information is an important criterion for the
handover decision especially in heterogeneous networks.
To enable seamless QoS provisioning, we introduce the following new
functionalities in our proposed signaling protocol:
o Mobility supporting functions. To avoid the extra message
exchanges for the discovery, each access routers broadcasts
enhanced advertisements regularly, which contains the information
about the next suited CASP nodes.
o QoS information before handover. The enhanced advertisements
contain information about the available resources in the network
and a mobile node can the select the suited access router. This
procedure demands an efficient and fast information distribution
mechanism in the access network.
o Price information before handover. If a mobile node receives
advertisements from different access networks, its decision for
the next access router may depend on the price of the offered
service. Therefore, the enhanced advertisements also contain an
optional field for the price information.
In the following chapters, we describe the components of the CASP
Mobility Client, which enables seamless QoS provisioning support for
mobile nodes. We also explain the mechanism and the message flows in
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both the general mobility management (e.g. Mobile IPv6 (MIPv6)) case
and the micro-mobility management (e.g. Hierarchical MIPv6 (HMIPv6))
case.
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2. Enhanced Advertisements
Presently, the advertisement only includes the topology information
of the access network. In MIPv6 case, mobile node can construct a
new Care-of-Address (CoA) based on the advertised prefix information.
Before performing a handover, mobile node may receive more than one
advertisement from different access routers before the old
advertisement expires.
We introduce information about the available aggregated QoS of a path
and about the price. A mobile node can access the most suited
network which offers proper QoS and a reasonable price.
2.1 Message Propagation
The foreign mobility agent (e.g. MAP in HMIPv6) of a network is
responsible for its own discovery. Therefore it advertises its
presence downstream in the access network.
Every foreign mobility agent or intermediate router(IR) MUST be able
to receive and propagate advertisement messages from its upstream
nodes in the access network.
Figure 1 shows how advertisement messages propagate in a hierarchical
architecture. The router in level 2 sends its advertisement to the
routers in level 1, including e.g. its prefix information, the
bandwidth value it can provide and the price information. The
routers in level 1 receives the advertisement and extracts the useful
information from it. Then it composes its own advertisement which
contains 1) the prefix information of the upper router and itself; 2)
QoS parameters e.g. available bandwidth of the path; and 3) the
applicable price information if any. Then it sends out its
advertisement. In general, the advertisements from routers in level
1 are sent more frequently than those from routers in level 2.
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+------+
level 2 |router|
| |
/+------+\
Advertisement / \ Advertisement
/ \
v v
+------+ +------+
level 1 |router| |router|
| | | |
+------+ +------+
\ /
Advertisement \ / Advertisement
\ /
v v
+------+
|mobile|
| node |
+------+
Figure 1: Advertisements propagate
2.2 Considerations of the Routers in the Access Network
This section describes the required operations of the routers in an
access network regarding the propagation of QoS and price
information. Usually the information about available resources in a
network varies more often than the price information.
To reduce the signaling traffic in the network it is advantageous not
to advertise the resources each time after a minimal change occurred.
Therefore, the routers in the network can maintain threshold values.
Apart from that all the values are soft states which are continuously
sent by each router.
The threshold values determine, under which condition a new
advertisement MUST be sent out immediately. Each router (including
intermediate router) maintains an upper and a lower threshold value.
When the remaining total bandwidth at a router reaches the lower
threshold value, the router will not insert the normal bandwidth
value which it is providing to a session in its regular
advertisements any longer. It sends immediately a new advertisement
with a less bandwidth value in it, announcing that it will provide
the new bandwidth for further sessions. It will use the new
bandwidth value in its regular advertisement until the remaining
total bandwidth reaches the upper threshold value. This strategy
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aims to serve more sessions with a degraded quality instead of
providing the whole bandwidth to only some mobile nodes and rejecting
the requests of others.
When the remaining total bandwidth reaches the upper threshold value
due to the bandwidth release from terminated sessions, the router
advertises immediately the normal bandwidth since it has enough
resources again to provide the normal bandwidth to each session.
When the remaining total bandwidth fall in the range of the upper and
lower threshold, no irregular advertisement is necessary to be sent
out. Otherwise, there would be too many unnecessary advertisements
being sent out when the remaining total bandwidth is oscillating
around one threshold value due to the continuing process of resource
releasing and reserving.
In general, an advertisement must be sent if one of the following
events occurs:
o The router receives a new advertisement from another router. The
router must add its own information and forward the advertisement
downstream.
o The available resources or the price for using the resources
changes if there is no threshold values; or the change recommends
the sending of an advertisement as described above.
o The validity of the advertised information expires. All
advertised information are soft state and must be regularly
refreshed. If a router does not receive a refresh from another
router for a certain period of time, the information expires.
o The router receives a solicitation message. In some cases it will
be useful for a mobile node to request information from routers
via solicitation messages.
o Registration or deregistration of a mobile node at a foreign agent
(FA). If the FA receives a registration update from a mobile node
which leaves an access network, the FA can release the reserved
resources and it CAN (depending on the application of thresholds)
send an advertisement to the routers in the network.
The described process considers the available bandwidth only in the
access network. It is not able to provide the QoS information
outside the access network.
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2.3 Message Format
An enhanced ICMPv6 Router Advertisement message is shown in Figure 2.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|vers=6 |Prio=15| Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length |Next Header=58 | Hop Limit =255|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| Source Address = router or home agent's address |
+ +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| Destination Address = mobile node's address* or All-Nodes |
+ multicast address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=134 | Code=0 | Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Cur Hop Limit |M|O| Reserved | Router Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reachable Time |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Retrans Timer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=3 | Length=4 | Prefix Length |L|A| Reserved 1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Valid Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preferred Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| (Network-)Prefix |
+ +
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| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length=3 | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Valid Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| CASP node address |
+ +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length=1 |Flg| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Bandwidth | Price Reference Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* The mobile node's address is used as the destination address only
when the advertisement corresponds to the mobile node's solicitation
message.
Figure 2. Message format of an enhanced advertisement
The details of IPv6 header and ICMPv6 router advertisement refer in
[6]and [7].
We describe only the fields of the enhanced features, which are the
IPv6 address of the next CASP node, available bandwidth information,
a price reference label.
Next CASP node Option:
Type TBD
Length 8-bit unsigned integer. The length of the option
(including the type and length fields) in units of
8 octets. The value is 3.
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Reserved This field is unused.
Valid lifetime
This value indicates the validity duration of the
announced CASP node.
CASP node address
The IPv6 address of "the next CASP node". This
address is used as the destination address for the
CASP messages which are sent by the mobile node to
reserve bandwidth in the access network.
Bandwidth and Price Information Option:
Type TBD
Length 8-bit unsigned integer. The length of the option
(including the type and length fields) in units of
8 octets. The value is 1.
Flg A 2-bit flag to indicate the presence of the available
bandwidth and the price reference label. 11 means
the advertisement contains available bandwidth
and price reference label information; 10 means only
available bandwidth and no price reference label; 01
means only price reference label and no available
bandwidth information.
Available Bandwidth
16-bit unsigned integer represents the available
bandwidth for each mobile node at the router.
Price Reference Label
16-bit unsigned integer represents the price
information in the administrative domain.
The Next CASP node option is only demanded, if the access router
itself can not handle the CASP messages from the mobile nodes. In
this case, it advertises the address of another CASP node in the
access network, which is suited to process the reservation requests
from the mobile nodes. Another application area is the usage of
brokers in the access networks.
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The Bandwidth and Price Information Option SHOULD be included in
every advertisement. According to the available bandwidth
information, mobile nodes can make decisions on 1) whether to perform
a handover; and/or 2) which access router it should handoff to.
Moreover, the additional 32-bit length of the Bandwidth Fields is
trivial even for wireless channels.
This value MAY be replaced by another value when a router at the
lower level can provide only less bandwidth. Hence a mobile node can
determine the aggregate bandwidth provided by the path when it
receives an enhanced advertisement. A mobile node SHOULD be able to
obtain the available bandwidth information by means of e.g. sending
a solicitation message.
To reduce the required number of bits in the price information field,
a label is used in this field rather than the detailed price
information. Each label specifies a charging model (e.g. 0,25 Euro
per min for the first 3 mins and 0,10 Euro per min for every
additional min). A mobile node can determine the price with the
label based on the knowledge of the label defined in a price
reference table. If a mobile node does not have the knowledge of the
label or the price reference table, it can request the information
from the access network by means of e.g. sending a solicitation
message. The access network SHOULD answer each individual
solicitation request with the meaning of the label by either unicast
or anycast depending on a local policy unless it considers that it is
under an attack with an excessive amount of such requests.
Furthermore, mobile nodes SHOULD be able to authenticate and check
the integrity of the price information presented in an advertisement.
More details are discussed in the section of security considerations.
Other issues of price information distribution are discussed in [3].
It MAY be necessary that the domain administrator refreshes the price
reference table periodically. The refresh interval MUST be much
larger than that of advertisement.
When the service provider changes the charging model by replacing the
old price reference label with a new one from the same price
reference table, or it assigns a new charging model to a label, it
MUST publicize the new charging model in the access network while
taking the following considerations:
o The access network SHOULD NOT spend a lot of bandwidth on
distributing the detailed information;
o A mobile node in the access network SHOULD be able to obtain the
charging model information if he does not receive the information
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distributions.
Therefore, when the access network needs to publicize the new
charging model, it repeats the meaning of a price reference label in
advertisements for e.g. five times. It includes the information in
one advertisement e.g. every three advertisements. During the
charging model publication period, the access network MAY or MAY NOT
answer solicitation requesting the information. After the period, it
SHOULD answer the solicitation with the information unless it
considers that it is under an attack with an excessive amount of such
requests.
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3. QoS Signaling and Registration Process with MIPv6
After the binding update is sent to the home agent (HA) every packet
to the mobile node (MN) is routed via its home network. This
Triangular routing between the HA, MN and correspondent node (CN) is
removed after sending the first packet from the MN to the CN.
Support for route optimization is a fundamental part of MIPv6 and
available as an extension for MIPv4.
Usually a reservation is initiated by the mobile node. If the
correspondent node wants to reserve a path to the mobile node and if
route optimization is not yet established, an appropriate error
message should be generated by the mobile node or the HA. If the MN
sends this message it can attach a binding update and the CN may then
try to establish a reservation through the optimized route to the CoA
of the MN.
Figure 3 shows the message flow during a QoS resource reservation
with CASP in a MIPv6 network.
MN oAR nAR CR HA CN
| | | | | |
|( Router Sol. )| | | |
|(--------------------->)| | | |
| | | | | |
|Router Adv. | | | | |
|<-----------------------| | | |
| | | | | |
|Binding Upd.| | | | |
|----------------------------------------------->| |
| | | | | |
| |Binding Ack| | | |
|<-----------------------------------------------| |
| | | | | |
|( | | | | Data )|
|( | | | Data |<----------)|
|(<=======(Tunnel)===============================| )|
| | | | | |
|Binding Upd.| | | | |
|------------------------------------------------------------>|
| | | | | |
| | | | Binding Ack |
|<------------------------------------------------------------|
| | | | | |
|CASP-QoS QUERY/RESERVE/COMMIT* | | |
|------------------------------------------------------------>|
| | | | | |
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| | CASP-QoS SUCCESS* | | |
|<------------------------------------------------------------|
| | | | | |
|Data, HAO** | | | | |
|------------------------------------------------------------>|
| | | | | |
* The CASP-QoS message types are defined in [3]. The RELEASE message
is sent only when the dead-branch-removal flag is set.
** Home Address Option (HAO)
Figure 3: Message flows with advertisements in MIPv6 scenarios
In inter-domain handover or power-up cases, a mobile node can obtain
related information in the access network by either listening to
Router Advertisements or performing Router Solicitation. Handover
detection based on advertisements significantly contributes to
handover latency. Alternatively, before registering with the access
router the MN can send a solicitation message to all access routers
near it.
When MN receives an enhanced advertisement, it can start BU process
without the help of scout messages. If an access network does not
have this feature of enhanced advertisement, a mobile node MAY send
out a scout message to locate its next suitable CASP-aware node as
described in [1]. The approach of sending scout messages may
introduce significant latency in a handover procedure.
After sending the binding update to the home agent and receiving the
Acknowledgement, the CoA of the MN is registered.
If the MN wants to establish a reservation to a correspondent node,
possible after receiving a data packet from it, it adds a Binding
Update and a home address option to its next packet which is sent to
the CN. This is followed by a CASP-QoS QUERY/ RESERVE/ COMMIT
message.
The CN replies with a SUCCESS message and a routing header to the MN
if the reservation is successful. Otherwise it generates an error
message, and the MN may retry its request with a partial reservation.
Figure 4 shows a CASP QoS RESERVE message example.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
1 | Option type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2 |F|D|A| Reserved| Flow label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3 | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4 | MN Address |
5 | |
6 | |
7 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8 | Address of the next CASP node |
9 | |
10 | |
11 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 | MN-HoA* |
13 | |
14 | |
15 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 | AR Address |
17 | |
18 | |
19 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 |Object Type | Object Length | desired Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
21 |Object Type | Object Length | acceptable Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* Home Address of MN (MN-HoA). It represents an global unique
identification of the MN. This is relevant to charging.
Figure 4: CASP QoS RESERVE message example [8]
It is noted that the CASP-QoS information can be piggybacked to the
binding-update packet even though the BU and the CASP signaling
processes occur in series as shown in Figure 3.
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4. QoS Signaling and (Re-)registration Processes with HMIPv6 in a
Separate Signaling Manner
The following are some observations and requirements on intra-domain
handover (micro-mobility):
o After a handover from one access router to another, a bigger part
of the reserved path stays unchanged. The crossover router (CR),
where the old and the new path meet, is usually near the mobile
node.
o The duration of a handover and of the re-establishment of
reservations should be short.
o There is always a mobility entity in the visited domain to help
the mobility management, e.g. foreign agent (FA) in MIPv4,
mobility anchor point (MAP) in HMIPv6.
o Handovers happen quite often.
Due to these the QoS signaling is different from that after a route
change or a normal change of the point of attachment to a network.
According to the topology shown in Figure 5, Figure 6 shows the
message exchanges in HMIPv6 scenarios. The upper part of the message
flows shows how to establish a reservation; the lower part shows the
re-establishment of the existing reservation after an intra-domain
handover.
+-----+ +------+
|home |---------------| MAP* |
|agent| ____| |__________
+-----+ / +------+ \
| / | \
| / | \
+-------------+ +-----+ +-----+
|correspondent| | oAR | | nAR |
| host | +-----+ +-----+
+-------------+ ^
\
v
+------+
|mobile|----->
| node |
+------+
* Mobility Anchor Point (MAP)
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Figure 5. HMIPv6 micro-mobility network topology.
The MAP is a router located in the foreign domain. It is used by the
MN as a local HA. It intercepts all packets addressed to registered
Mobile Nodes and tunnels them to the corresponding LCoA. In an
HMIPv6 intra-domain handover process, only the reservation on the new
path between MN and MAP needs to be re-established.
The message flows shown in Figure 6 occur in an HMIPv6 intra-domain
handover with a separate signaling manner.
MN oAR nAR MAP(CR) HA CN
| | | | | |
| | Advertisement from MAP | | |
| |<------------------------------| | |
| | | | | |
| Adv. from oAR | | | | |
|<---------------| | | | |
| | | | | |
| BU from MN to MAP as registration | | |
|----------------------------------------------->| | |
| | | | | |
| | BA from MAP to MN | | |
|<-----------------------------------------------| | |
| | | | | |
| BU from MN to HA as registration | | |
|----------------------------------------------------------->| |
| BU from MN to CN as registration | | |
|----------------------------------------------------------------------->|
| | | BA from HA to MN | |
|<-----------------------------------------------------------| |
| | | | BA from CN to MN |
|<-----------------------------------------------------------------------|
| | | | | |
|CASP-QoS QUERY/RESERVE/COMMIT | | | |
|----------------------------------------------------------------------->|
| | | | | |
| | | CASP-QoS SUCCESS | |
|<-----------------------------------------------------------------------|
|Existing Reservation | | | |
|rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr>|
| | | | | |
| | Adv. from MAP regularly | | |
| |<--------------|<--------------| | |
| | | | | |
| Adv. from nAR | | | |
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|<-------------------------------| | | |
| | | | | |
| BU from MN to MAP as re-registration | | |
|----------------------------------------------->| | |
| | | | | |
| | BA from MAP to MN | | |
|<-----------------------------------------------| | |
| | | | | |
|CASP-QoS QUERY/RESERVE/COMMIT | | | |
|----------------------------------------------->| | |
| | | | | |
| | CASP-QoS SUCCESS | | |
|<-----------------------------------------------| | |
| | CASP-QoS RELEASE | | |
| |<------------------------------| | |
|Reservation route change | | | |
|RRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRRrrrrrrrrrrrrrrrrrrrrrr>|
| | | | | |
| | intercept & tunnel packets | route packets |
|<-------------------------------|<--------------|<----------------------|
| | | | | |
| Data | | | | |
|----------------------------------------------------------------------->|
| | | | | |
Figure 6: QoS signaling and (re-)registration processes with HMIPv6
The details of the re-establishment of the existing reservation are
discussed as follows.
In Figure 6, it is assumed that the MAP is the cross-over router.
After receiving an advertisement from nAR/ L2 Trigger, the mobile
node sends a binding update request to the MAP of the network. After
MN receives the binding acknowledgement, the connection to the
foreign domain is reestablished. Afterwards the MN tries to rebuild
the reservation to the CN. It sends a QoS CASP reservation message
containing the IP address of the CN as the destination address. The
CASP message propagates until it reaches the CR.
MAP is assumed to be the first node which can identify the session
according to the existing session ID. Due to the changes the access
router and the link, the IP addresses in the flow-id are different.
When the upstream of the CASP-QoS signaling process is successful,
MAP replies a "CASP-QoS SUCCESS" message. If a dead-branch-removal
flag is used, the old reservation can be deleted. If the message
contains no flag, the old reservation should time out. The rest of
the path to the CN remains the same and the CR can initiate the re-
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establishment of the upstream reservation. In case of "CASP-QoS
FAILURE", MN either keeps the new connection without any QoS support
or revokes the binding updates and stays in the old path. The
integrated signaling procedure shown in the next section can avoid
this dilemma.
If there is only an upstream reservation, the reservation message can
be discarded by MAP. Else, if there is also a downstream
reservation, the CN needs to be informed about the handover. This
can be done by sending an error message for the existing downstream
reservation to the CN.
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5. QoS Signaling and Re-registration Processes with HMIPv6 in a Combined
Signaling Manner
In an access network the interaction between mobility management and
QoS resource reservation should be very close. Combining both
mechanisms is a valuable approach. This chapter describes a method
by which QoS information is collected in the access routers and
advertised to the mobile nodes, which may have the choice between
different access points and may choose the most suited one based on
the QoS information in advertisements [8].
In addition to the QoS and mobility considerations, the security
issues, such as authentication, authorization and DoS attack
protection should be taken into account.
The success of the re-registration procedure in an intra-domain
handover depends on two aspects: 1. the new path can provide e.g.
at least the acceptable bandwidth; 2. the re-authentication and re-
authorization (re-AA) checks pass.
Figure 7 shows the combined signaling message flows for the intra-
domain handover case in HMIPv6 scenarios [8]
It is assumed that MN has a bidirectional QoS-enabled connection with
CN before it starts an intra-domain handover. MN receives more than
one enhanced advertisements from different ARs, it can select the
most suitable AR as the handover target. When the handover is
triggered, MN sends an re-registration request message to the target
AR(nAR). When nAR receives the request, it starts the BU process.
CASP is embedded in the BU packet. Each node along the path from nAR
to MAP checks whether it can satisfy at least e.g. the acceptable
bandwidth for either uni-direction or bi-direction. If yes, it
reserves the requested resource. When MAP (which is assumed to be
the CR) realizes that each node on the path can meet the request, it
communicates with AAAL for a re-authentication and re-authorization
(re-AA) check. If the re-AA passes, MAP sends back a BU ACK packet
including CASP. While MAP sends the BU ACK packet, it initiates the
reservation release process to tear down the path between oAR and
MAP.
In brief, the integration of BU process and CASP-QoS signaling is
beneficial for intra-domain handovers in terms of the low-latency
feature.
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MN oAR nAR MAP(CR) AAAL CN
|Existing Reservation | | | |
|rrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr>|
| | | | | |
|Router Adv. | | | | |
|<-----------------------| | | |
| | | | | |
|Re-registration req. | | | |
|----------------------->| | | |
| | |BU+CASP* | | |
| | |---------->| | |
| | | |re-AA | |
| | | |<-------->| |
| | |BU ACK + CASP** | |
| | |<----------| | |
| |BU ACK | | | |
|<-----------------------| | | |
| | CASP-QoS RELEASE | | |
| |<----------------------| | |
| | | | | Data |
|( | Data | |<---------------------)|
|(<=======(Tunnel)===================| | )|
| | | | | |
|Data, HAO***| | | | |
|----------------------------------------------------------->|
| | | | | |
* the CASP message (QUERY/RESERVE/COMMIT) can be send in parallel
to the BU message or may be combined and checked by each CASP node
along the path.
** the CASP (SUCCESS) can trigger the downstream QoS
signaling.
*** Home Address Option (HAO)
Figure 7: Message flows with the advertisements in HMIPv6
scenarios
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6. Security Considerations
Security threats for NSIS are identified in [5]. NSIS AAA issues are
included in [3].
There are additional security issues related to enhanced
advertisements.
Mobile nodes SHOULD be able to authenticate the source of an
advertisement, and to check the integrity of QoS and price
information in an advertisement. If a malicious node modifies the
price distribution information or it advertises wrong information
masquerading a legal AR, it can cause trouble or confusion to mobile
users or to the service provider when mobile nodes do not perform the
security checks.
Details of a solution will be worked out in subsequent versions of
this draft.
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References
[1] Schulzrinne, H., "CASP - Cross-Application Signaling Protocol",
Internet Draft draft-schulzrinne-nsis-casp-01.txt, March 2003.
[2] Schulzrinne, H., "A Quality-of-Service Resource Allocation
Client for CASP", Internet Draft draft-schulzrinne-nsis-casp-
qos-01.txt, March 2003.
[3] Tschofenig, H., "NSIS Authentication, Authorization and
Accounting Issues", Internet Draft draft-tschnofenig-nsis-aaa-
issues-01.txt, March 2003.
[4] Krawczyk, H., Bellare, M. and R. Canetti, "HMAC: Keyed-Hashing
for Message Authentication", Request for Comments RFC 2104,
February 1997.
[5] Tschofenig, H., "Security Threats for NSIS", Internet Draft
draft-ietf-nsis-threats-01.txt, January 2003.
[6] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", Request for Comments RFC 2460, December 1998.
[7] Narten, T., Nordmark, E. and W. Simpson, "Neighbor Discovery for
IP Version 6 (IPv6)", Request for Comments RFC 2461, December
1998.
[8] Chen, T., Hermann, S. and G. Schaefer, "Secure QoS-enabled
Mobility Support for IP-based Networks", March 2003,
<http://www-tkn.ee.tu-berlin.de/research/SeQoMo/>.
Authors' Addresses
Sven D. Hermann
Technical University of Berlin
Sekr. FT 5-2, Einsteinufer 25
Berlin 10587
Germany
Phone: ++49 30 314 28224
EMail: hermann@ee.tu-berlin.de
URI: http://www-tkn.ee.tu-berlin.de/~hermann
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Tianwei Chen
Technical University of Berlin
Sekr. FT 5-2, Einsteinufer 25
Berlin 10587
Germany
Phone: ++49 30 314 23825
EMail: chen@ee.tu-berlin.de
URI: http://www-tkn.ee.tu-berlin.de/~chen
Guenter Schaefer
Technical University of Berlin
Sekr. FT 5-2, Einsteinufer 25
Berlin 10587
Germany
Phone: ++49 30 314 23836
EMail: schaefer@ee.tu-berlin.de
URI: http://www-tkn.ee.tu-berlin.de/~schaefer
Changpeng Fan
Siemens AG
Siemens AG
Berlin D-13627
Germany
Phone: ++49 30 386 36361
EMail: changpeng.fan@siemens.com
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Hermann, et. al. Expires December 12, 2003 [Page 26]
