Internet DRAFT - draft-jaehwoon-cats-mobility
draft-jaehwoon-cats-mobility
CATS Working Group Jaehwoon Lee
Internet-Draft Dongguk University
Intended status: Informational October 10, 2023
Expires: April 9, 2024
Network-based mobility management in CATS network environment
draft-jaehwoon-cats-mobility-01
Abstract
Computing-Aware Traffic Steering (CATS) network architecture is to
choose the best edge computing server by considering both the network
environment and available computing/storage resources of the edge
computing server. This draft describes the mechanism in which service
continuity is provided even when the client moves and connects to a new
ingress CATS-Router by using the PMIPv6-based mobility management
method in the CATS-based edge computing networking environment.
Status of this Memo
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This Internet-Draft will expire on April 9, 2024.
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Table of Contents
1. Introduction.................................................2
2. Conventions and Terminology..................................3
2.1. Conventions used in this document........................3
2.2. Terminology..............................................4
3. Protocol Operation...........................................4
4. Message Formats..............................................7
4.1. CATS mobility notification and request messages..........7
4.2 CATS mobility indications message........................7
4.3 Mobile node anddes and CATS address options..............8
5. Security Considerations......................................9
6. IANA Considerations..........................................9
7. References....................................................9
Author's Address.................................................9
1. Introduction
Cloud computing provides powerful computing and nearly unlimited
storage resources to client devices connected over the Internet.
However, if the number of clients, such as Internet of Things (IoT)
devices is quite large, the amount of traffic exchanged between
clients and the cloud computing server is also igh and it can cause
congestion over the Internet. When congestion occurs on the path
between a client and the cloud computing server, the client
transmitting service request may experience long response time in
receiving the result of the service request, or the service request
itself may be lost.
In edge computing, even though edge computing server provides
smaller computing and storage resources compared to the cloud
computing server, multiple number of edge computing servers can be
located near client devices and the client sending service request
can benefit from shorter response time. In the edge computing
environment, one way for a client to find a suitable edge computing
server is to choose the nearest edge server based on the location of
the client inferred from the client's source IP address. Another way
is to choose one of the several edge servers by utilizing the round-
robin method. However, in such cases, if the available resource in
the chosen server is insufficient or congestion occurs on the path
between the client and the chosen server, the client may experience
longer response time or service request may be lost.
IETF CATS working group tries to standardize the mechanism to
choose the best edge computing server by considering both the
networking environment and available computing/storage resources of
the edge computing server[1]. Here, a service is represented by an
CATS Service ID (CS-ID). Assume that there is a client trying to
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receive a service provided by a specific service instance. In this
case, ingress CATS-Router acts as a gateway for the client. In
addition, egress CATS-Router is connected to the edge computing
server in which specific service instance is installed. Assume that
there are N edge servers providing a specific service. Moreover,
each edge server is assumed to be connected to a different egress
CATS-Router. The client transmits a service request message with
CS-ID as a destination IP address. Ingress CATS-Router chooses the
best egress CATS-Router by using the combination of the network
metric such as delay, and computing metric such as available
computing/storage resource of edge servers. The ingress CATS-Router
transmits the service request sent by the client to the chosen
egress CATS-Router. After which egress CATS-Router transmits the
service request to the service instance in the edge computing
server. The result of the service request is in turn transmitted
from the edge server to the client through the egress CATS-Router
and the ingress CATS-Router.
When a client transmits a service request and then moves to another
network before receiving the service result, the client can no
longer receive the result of the service request. When the client
moves and connects to a new ingress CATS-Router, host-based mobility
management method such as Mobile IPv6 (MIPv6) can be used to
maintain end-to-end connectivity[2]. In this case however, the
destination IP address of the service request message sent by the
client is the CS-ID. Which means that the new ingress CATS-Router
cannot know the address of the egress CATS-Router connected to the
edge server providing service to the client which uses the CS-ID as
the destination IP address. Therefore, host-based mobility
management cannot be used in the CATS networking environment. That
being said, network-based mobility management mechanism such as
Proxy MIPv6 (PMIPv6) can be used in the CATS networking environment
if the new ingress CATS-Router knows the address of the egress CATS-
Router connected to the edge server providing service to the
client[3]. In this case, service continuity is ensured for the
client. However, new ingress CATS-Router cannot know the IP address
of the egress CATS-Router only using the address information of the
IP packet sent by the client. The reason is that the destination
address of the IP packet indicates not a specific destination but a
specific service.
This draft describes the mechanism in which service continuity is
provided even when the client moves and connects to a new ingress
CATS-Router by using the PMIPv6-based mobility management method in
the CATS-based edge computing networking environment.
2. Conventions and Terminology
2.1. Conventions
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL","SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [4].
2.2 Terminology
TBD.
3. Protocol Operation
When a client moves from an ingress CATS-Router to another ingress
CATS-Router before receiving all the service results, either
proactive method of reactive method can be utilized to provide
service continuity.
Fig. 1 shows the message exchange procedure to provide service
continuity proactively when a client moves to another network in
CATS networking environment. If the client transmits service
request message with CS-ID as a destination IP address, an ingress
CATS-Router (that is, old ingress CATS-Router) chooses the best
egress CATS-Router by using the combination of the network metric
and computing metric. The old ingress CATS-Router transmits the
service request to the chosen egress CATS-Router. The egress CATS-
Router transmits the service request message to the corresponding
service instance in the edge computing server. When the old ingress
CATS-Router detects the movement of the client before completing
transmission of all service results, it transmits the CATS mobility
notification message including the addresses of the client and the
chosen egress CATS-Router to one or more candidate new ingress
CATS-Routers that client may connect to. The format of the CATS
mobility notification message is defined in Section 4.1. Here, how
the old ingress CATS-Router can know the movement of the client is
out of scope. One method is to use the signal strength of the
client. Moreover, how the old ingress CATS-Router can know which is
the new ingress CATS-Router that the client moves and connects to is
TBD. One method is for the old ingress CATS-Router to broadcast the
CATS mobility notification message to neighbor ingress CATS-Routers.
Another method is to find some candidate ingress CATS-Routers by
using the GPS information of the client. When the client moves and
connects to a new ingress CATS-Router, the new ingress CATS-Router
transmits the CATS mobility indication message having the IP address
of the client to the old ingress CATS-Router and establishes the
tunnnel with the old ingress CATS-Router. The format of the CATS
mobility indication message is defined in Section 4.2. The old
ingress CATS-Router having received the CATS mobility indication
message also establishes the tunnel with the new ingress CATS-
Router.
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Client old ingress Router new ingress Router egress Router Service
instance
| | | | |
|<--connect -->| | | |
|-service req->| | | |
| |------ service request --------->| |
| | | |-service req ->|
(movement) | | | |
| (client move detection) | | |
| |- notify msg ->| | |
|<----- connect ---------->| | |
| |<-- ind. msg --| | |
| |<=est. tunnel=>| | |
| | | |<- svc result--|
| |<---- service result -----| |
| |- svc result ->| | |
|<--- svc result ----| | |
| | |--- ind. msg --->| |
| | | |<- svc result--|
| | |<-- svc result --| |
|<--- svc result ----| | |
Figure 1: Message exchange procecure - proactive method
Moreover, the new ingress CATS-Router transmits the CATS mobility
indication message having the client's IP address and the IP address
of the old ingress CATS-Router to the egress CATS-Router. From now
on, the old ingress CATS-Router and the egress CATS-Router can
transmit all services results to the client through the new ingress
CATS-Router.
Fig. 2 shows the message exchange procedure to provide service
continuity reactively to the client. If the client moves and
connects to a new ingress CATS-Router, the new ingress CATS-Router
transmits the CATS mobility request message including the IP address
of the client to the old ingress CATS-Router. The format of the CATS
mobility request message is defined in Section 4.1. Here, how the
new ingress CATS-Router can know the address information of the old
ingress CATS-Router is TBD. One method is to use a location server.
When a client connects to an old ingres CATS-Router, the old CATS-
Router store the IP and link layer addresses of the client and the
IP address information of the egress CATS-Router that the service
request of the client is transmitted in the location server. The
information regarding the client can be removed just after all
service results are transmitted to the client. When a client moves
to a new ingress CATS-Router, then the new ingress CATS-Router can
know whether the client is a new client or the client requiring
service continuity by quering the information stored in the server.
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Client old ingress Router new ingress Router egress Router Service
instance
| | | | |
|<--connect -->| | | |
|-service req->| | | |
| |------ service request --------->| |
| | | |-service req ->|
(movement) | | | |
|<----- connect ---------->| | |
| |<-- req. msg --| | |
| |- notify msg ->|
| |<=est. tunnel=>| | |
| | | |<- svc result--|
| |<---- service result -----| |
| |- svc result ->| | |
|<--- svc result ----| | |
| | |--- ind. msg --->| |
| | | |<- svc result--|
| | |<-- svc result --| |
|<--- svc result ----| | |
Figure 2: Message exchange procecure - reactive method
Another method is to assign a network address to CAT domain but
different sub-network address is assigned to different ingress CATS-
Router. For example, assume that 10.0.0.0/8 network address is
assigned to a CATS domain. Here, 10.0.0.0/16 sub-network address is
assigned to the old ingress CATS-Router and 10.0.1.0/16 sub-network
address is assigned to the new ingress CATS-Router. Moreover,
10.0.0.1 IP address is assigned to the old ingress CATS-Router and
10.0.1.1 IP address is assigned to the new ingress CATS-Router. When
a client connects to the old ingress CATS-Router, the router
advertises 10.0.0.0 network address by using the Router
Advertisement message. If the client transmits DHCP request message
requesting a new IP address, the router assigns one of the IP
addresses belonging to 10.0.0.0/16 sub-network address. When the
client moves and connects to the new ingress CATS-Router, the router
advertises 10.0.0.0/8 network address by using the Router
advertisement message. If the client transmits DHCP request message,
then the router considers that the client is the newly connected
client. Otherwise, the router can deduce the IP address of the old
ingress CATS-Router by using the source IP address of the packet
transmitted by the client. The old ingress CATS-Router having
received CATS mobility request message transmits the CATS mobility
notification message including the IP address of the egress
CATS-Router to the new ingress CATS-Router and establishes the
tunnel with the new ingress CATS-Router. Moreover the old ingress
CATS-Router can inform the new ingress CATS-Router whether the
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client needs service continuity or not by using the notification
message. The new ingress CATS-Router transmits the CATS mobility
indication message to the old ingress CATS-Router and establishes
the tunnel with old ingress CATS-Router. Moveover, it transmits the
CATS mobility indication message to the egress CATS-Router. From now
on, the old ingress CATS-Router and the egress CATS-Router can
transmit all service results to the client through the new ingress
CATS-Router.
4. Message Formats
4.1 CATS mobility notification and request messages
In this draft, the proxy binding update message defined in the Proxy
Mobile IPv6 protocol is used to define the CATS mobility
notification and request messages [3]. The message format is as
follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A|H|L|K|M|R|P|C|N| Reserved | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
C: CATS flag. This bit must be set to 1 in the CATS environment.
N: The flag must be set to 0 for CATS mobility notification message
must be set to 1 for CATS mobility request message.
The mobility option of the CATS notification message contains client
node address option and CATS address option defined in Section 4.3.
In this case, the address contained in the CATS address option is
the egress CATS-Router address. Moreover, the mobility option of the
CATS request message contains the client node address option.
4.2 CATS mobility indication message
In this draft, the proxy binding acknowledgment message defined in
the Proxy Mobile IPv6 protocol is used to define the CATS mobility
indication message [3]. The message format is as follows:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Status |K|R|P|C|Resrved|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence # | Lifetime |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Mobility options .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
C: CATS flag. This bit must be set to 1 in the CATS environment.
When the message is transmitted from the new ingress CATS-Router to
the old ingress CATS-Router, the client node address option is
included in the mobility option. Moreover, when the message is
transmitted from the new ingress CATS-Router the the egress
CATS-Router, the client node address and CATS address options are
included in the mobility options. In this case, the address included
in the CATS address option is the old ingress CATS-Router.
4.3 Mobile node address and CATS address options
In this draft, the mobility option defined in the Mobile IPv6
protocol is used to define the client node address and CATS address
options [2]. The option format is as follow:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length = 16 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Client node address option:
- Type : TBD
- The mobile node address is included in the Address field.
CATS address option:
- Type : TBD
- The CATS address is included in the address field.
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5. Security Considerations
TBD
6. IANA Considerations
TBD
7. References
[1] C. Li, Z. Du, M, Boucadair, L. M. Contreras, J. Drake, G. Huang
and G. Mishra, "A Framework for Computing-Aware Traffic
Steering (CATS)", draft-ldbc-cats-framework-03 (work in
progress, Aug. 3, 2023.
[2] D. Johnson, C. Perkins and J. Arkko, "Mobility Support in
IPv6", IETF RFC 6275, July 2011.
[3] S. Gundavelli, K. Leung, V. Devarapalli, K. Chowdhury and
B. Patil, "Proxy Mobile IPv6", IETF RFC 5213, Aug. 2008.
[4] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Author's Address
Jaehwoon Lee
Dongguk University
30, Pildong-ro 1 gil, Jung-gu
Seoul 04620, KOREA
Email: jaehwoon@dongguk.edu
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