Internet DRAFT - draft-choi-ipv6-signaling
draft-choi-ipv6-signaling
Internet Draft Jun Kyun Choi
Document: draft-choi-ipv6-signaling-02.txt Gyu Myoung Lee
Expiration Date: December 2002 Ki Young Jung
ICU
Woo Seop Rhee
ETRI
June 2002
The Features of IPv6 Signaling
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC-2026.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
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The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
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Abstract
In this draft, we describe the features and requirements of IPv6
signaling protocol and explain the needs of QoS signaling in IPv6
network. We also explain mapping of IPv6 signaling with IPv4 in some
detail.
Conventions
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 RFC-2119.
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Table of Contents
1. Introduction.....................................................2
2. The Needs of QoS Signaling in IPv6 networks......................3
2.1. IP related Signaling Protocols..............................3
2.2. QoS related Signaling Protocols.............................3
2.3. The Features of QoS related Signaling in IPv6 Networks......4
2.4. The Requirements of QoS Signaling Protocol in IPv6 Networks.5
3. Mapping of IPv6 Signaling with IPv4..............................7
4. Other Issues.....................................................9
5. IANA Considerations..............................................9
6. Security Considerations..........................................9
Appendix. The delivering methods of signaling messages in IPv6
network............................................................10
References.........................................................14
Acknowledgements...................................................15
Author's Addresses.................................................15
1. Introduction
Many signaling mechanisms are defined and developed to support
Quality of Service (QoS) in IP networks. Those are chosen by users to
satisfy their needs, objectives, and implementation costs. Also most
of the signaling protocols are based on the underlying network
infrastructure, i.e. IP networks, but they don't depend on the minor
version of the network. For example, one signaling protocol designed
for the IPv4 network can be used in IPv6 network without modifying
the specification of the signaling mechanism. Rather than to do like
that, the signaling protocol adopt itself to the different version of
network implementation by defining option fields like IP version
information field and related information like IPv4 addresses (32
bits) or IPv6 addresses (128 bits).
Actually, IPv6 has many features to support QoS and other
capabilities for the emerged networks. We will describe about that in
section 2. Also, those features can be used to help existing IPv4
based signaling mechanisms or used to substitute some functions of
existing signaling protocols in order to make the signaling protocols
more fully using the power of IPv6 features.
In this draft, we describe the features and requirements of IPv6
signaling protocol to explain the needs of QoS signaling in IPv6
network. Deployment point of view, we also explain three stages of
evolution scenarios and mapping of IPv6 signaling with IPv4 in some
detail. Finally, the delivering methods of signaling messages in IPv6
network are presented in appendix.
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2. The Needs of QoS Signaling in IPv6 networks
2.1. IP related Signaling Protocols
There are already many signaling protocols in IP networks to provide
some control delivering mechanism with or without QoS support. We can
classify the signaling mechanisms regarding the actual nodes that are
affected by that signaling protocol.
A signaling protocol may concern with a pair of node that may be host
or router. Like ICMP, that kind of signaling protocol is just for the
information notification. On the other hand, like SIP described in
[RFC 2543], some signaling may be transferring the QoS related
information that can be used to a node to determine the control of
resource of the node.
There are other kinds of signaling protocols that effect on the nodes
on a path of source to destination path. With regarding the QoS,
currently RSVP [RFC 2205](or RSVP-TE [RFC 3209]) and LDP[RFC 3036]
(or CR-LDP [RFC 3212]) is defined to provide QoS in intermediate node
of the path in the IP networks. We just use the term "IP network"
because any kind of sub layer mechanism can be used to support the
transport of IP packets.
Other signaling protocols are defined between the neighbors those are
connected with link. We will not mention about this case because this
case is treated with special case of above two cases.
We will regard the signaling protocols that use IP or higher layer
and related with QoS mechanisms.
2.2. QoS related Signaling Protocols
Usually the QoS mechanisms are supported in the IP layer or the
Transport layer (for example, TCP or UDP). To simplify the discussion,
we will just regard the three signaling protocols, RSVP-TE, CR-LDP,
SIP. These signaling protocols are covering the classification in
section 2.1 and also these signaling mechanisms can be used for the
some or all of QoS supporting features described in 2.3. Also we note
that these are running on the IP and TCP (UDP) layer. We will explain
these signaling protocols as briefly as possible to make our
discussion further.
o RSVP-TE (including RSVP-TE extension for GMPLS [RSVP-TE 07])
RSVP-TE, originated by RSVP is used for the IntServ model described
in [RFC 2210]. Both RSVP and RSVP-TE are implemented on the IP layer.
RSVP is defined to support QoS in IP network with fine granularity,
but this leads the scalability problems. RSVP-TE has some additional
concepts, like label distribution, aggregated flow, and explicit
route. But RSVP-TE doesn't support multicasting environment.
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o CR-LDP (including CR-LDP extension for GMPLS [CR-LDP 06])
CR-LDP, from LDP, is used for the almost same purpose of RSVP-TE. But
this signaling protocol use the TCP (and UDP) layer instead of IP
layer in RSVP-TE. So this signaling protocol uses the features of TCP
protocol.
o SIP and H.323
To provide the multimedia services, like voice or moving pictures,
SIP and other protocols are defined to provide the server and client
side QoS mechanism. This protocol use ether TCP or UDP.
2.3. The Features of QoS related Signaling in IPv6 Networks
We will choose some existing signaling protocols to explain our idea.
To validate the further discussion, we must describe the features of
signaling mechanisms in IPv6 network with supporting QoS.
o QoS support
Information with QoS controlling is important context of signaling
packet. With aggregated flow concept, IPv6 signaling mechanisms can
provide finer QoS granularity than DiffServ model, and more scalable
than IntServ model.
o Resource Reservation
The key role of signaling protocol is to allocate and reserve the
network resource for the purpose of meeting end-to-end QoS
requirements along the entire path. The signaling protocol MUST be
able to deal with such resource allocation requests.
o Priority Flow Control
Each node has many flows with different priority of various data
rates and QoS requirements. These flows are classified and scheduled
with the capability of making intelligent decisions on how resource
allocation SHOULD be controlled.
o Explicit route
In IPv6 specification, there is a route extension header to use
explicit route. Explicit route is important for traffic engineering
in IPv6 networks, so we can use of this option header. In doing so,
signaling packet specify the route with route extension header and
data packet is just switched according to flow label in each router
on the path specified with signaling packet. There is already ROUTE
object in RSVP-TE specification [RFC 3209]. In the case of CR-LDP,
some TLVs are defined to be used for this purpose.
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o Scalability
The performance of the signaling protocol SHOULD not largely depend
on the scale of the network to which IPv6 is applied (e.g. the number
of nodes, the number of physical links etc). The signaling function
SHOULD keep constant performance as much as possible regardless of
network size. Aggregating flows can reduce resource allocation and
runtime management overhead.
o Flow Label Information Distribution
To make use of flow label field [Flow Label 02] of IPv6 basic header
and identify the flow label between the routers on specific path,
label-binding information SHOULD be delivered between the related
routers. The related routers are on the path of the flow. Label value
is only meaningful between a pair of routers. And the label value is
predetermined before forwarding data packet along the path.
o Label Stacking
In Label Switching, label stacking concept is addressed. To enable
the label stacking, the signaling protocol is defined to notify the
stacking information. But we don't consider the concept in this
version.
2.4. The Requirements of QoS Signaling Protocol in IPv6 Networks
Besides of features of signaling, we SHOUD consider the following
requirements of QoS signaling in IPv6 networks.
o Make use of IPv6 features
IPv6 have many features to make use of that to provide some new
functions. For example, one can want to use the IPv6 Routing Option
header to send signaling packet along the desired path rather than
the shortest path. This is reasonable because the IPv6 routers may be
implement routing option header processing component so we can use
that without any additional functional implementations. Also we can
think about the hop-by-hop header to notify routers that the packets
have some signaling and reservation information. These things are
already considered in other signaling mechanism. That means we can
use the IPv6 native features or don't use of them. There is another
viewpoint related with this. If the same information is transferred
with IPv6 header and payload, there may exist the consistency
problems. So some people want to make one of choices, not both of
them.
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o Backward compatibility
The existing signaling protocols such as RSVP, RSVP-TE, CR-LDP and so
on are implemented in IPv4 network. These signaling protocols MUST be
operated in IPv6 network. Therefore, they MUST support backward
compatibility for operating both IPv6 and IPv4.
o Easy to implement
There are two aspects related with this issue. First, we can consider
the compatibility of the new signaling with existing signaling. So
the implementation can be done with minimum modification of previous
architecture and components. Second we can omit some functions of
previous signaling so that we just make a light-weight signaling
mechanism. We are still studying about this carefully because it
makes some effects with other various factors such like the
capabilities of this new signaling and the signaling translation
between two heterogeneous AS's. We can think above two factors
simultaneously and SHOULD make some trade-off.
o Signaling interworking between IPv6 and IPv4
To be gradually deployed, we can consider the situation of mixed
nodes that some implement the IPv6 signaling and others implement
the IPv4 signaling. In this environment, we consider signaling
interworking issues. So we will explain mapping of IPv6 signaling
with IPv4 in section 3.
o Traffic parameters for QoS negotiation
There are many traffic parameters such as peak data rate, peak burst
size, committed data rate, committed burst size, excess burst size
and so on. The QoS signaling applies the traffic parameters per
aggregated flow. To make use of this, state of QoS information SHOLD
be maintained per aggregated flow. Also the adding and deleting of a
flow with respect to the aggregated flow SHOULD be carefully managed.
An aggregated flow is not just used for label-related switching, but
also used for classification information in routers on path. So the
traffic parameter information SHOULD be stored in the router with the
information related with an aggregated flow identifier(s).
o Mobility support
To provide the QoS in mobile environment, we SHOLD consider the
mobility of nodes and dynamic behavior of related flows. In signaling,
we are concerning two problems. First the flow management can be
considered with per aggregated flow or per flow. In some point,
snapshot of network can be described with many aggregated flows and
related QoS management. But as time goes, some flow of mobile node
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departs one aggregated flow and join the other aggregated flow.
Second the support of micro mobility issues. To make use of old flow
related resources as much as possible, we should define Nearest
Common Router (NCR) and provide the finding mechanism. This work is
under working. We just consider the need of modification or
adaptation of that mechanism in our work.
o Inter-operation with other QoS-supporting networks
In this version, we cannot consider this issue.
3. Mapping of IPv6 Signaling with IPv4
The current Internet will smoothly transit from IPv4 to IPv6.
Deployment point of view, we consider three stages of evolution
scenarios
- first stage (stage 1): IPv4 ocean and IPv6 island
- second stage (stage 2): IPv6 ocean and IPv4 island
- third stage (stage 3): IPv6 ocean and IPv6 island
In first stage shown in Figure 1, MPLS-based core network (e.g., IPv4
ocean) and IPv6 access network (e.g., IPv6 island)is deployed. In
this environment, core signaling such as RSVP-TE and CR-LDP is used
in IPv4 ocean and access signaling such as RSVP and RSVP-TE is used
in IPv6 island. To support end-to-end QoS signaling, these protocols
SHOUD perform the mapping of IPv6 signaling with IPv4. Flow label
information of IPv6 header is translated to FEC(Forwarding Equivalent
Class) information of MPLS. For this reason, signaling interworking
function is needed. Using this QoS signaling, flow information is
transmitted unchanged from source to destination and the required
resource is reserved and end to end path is established.
+-------------+ +---------------+ +-------------+
| IPv6 island |-------| IPv4 ocean |-------| IPv6 island |
| |-------| (MPLS) |-------| |
+-------------+ +---------------+ +-------------+
Flow Label -- mapping -- FEC -- mapping -- Flow Label
|<----------->| |<------------->| |<----------->|
RSVP/RSVP-TE RSVP-TE/CR-LDP RSVP/RSVP-TE
(Access signaling) (Core signaling) (Access signaling)
|<--------------------------------------------------------->|
end-to-end QoS signaling
Figure 1. Signaling mapping (stage 1)
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In second stage shown in Figure 2, IPv6 network will dominate over
IP4 network. This network is composed of IPv6-based core network
(e.g., IPv6 ocean) and IPv4-based access network (e.g., IPv4 island).
The existing IPv4 network is operated in MPLS. In this environment,
core signaling such as RSVP-TE and CR-LDP is used in IPv6 ocean and
access signaling such as RSVP and RSVP-TE is used in IPv4 island. FEC
information of IPv4 is translated to flow label information of IPv6.
+-------------+ +---------------+ +-------------+
| IPv4 island |-------| IPv6 ocean |-------| IPv4 island |
| (MPLS) |-------| |-------| (MPLS) |
+-------------+ +---------------+ +-------------+
FEC -- mapping -- Flow Label -- mapping -- FEC
|<----------->| |<------------->| |<----------->|
RSVP/RSVP-TE RSVP-TE/CR-LDP RSVP/RSVP-TE
(Access signaling) (Core signaling) (Access signaling)
|<--------------------------------------------------------->|
end-to-end QoS signaling
Figure 2. Signaling mapping (stage 2)
In third stage shown in Figure 3, IPv6 protocol is implemented both
core network (e.g., IPv6 ocean) and access network (e.g., IPv6
island). Signaling protocol like RSVP-TE MAY be used without
signaling translation.
+-------------+ +---------------+ +-------------+
| IPv6 island |-------| IPv6 ocean |-------| IPv6 island |
+-------------+ +---------------+ +-------------+
Flow Label -- mapping -- Flow Label -- mapping - Flow Label
|<----------->| |<------------->| |<----------->|
RSVP/RSVP-TE RSVP-TE/CR-LDP RSVP/RSVP-TE
(Access signaling) (Core signaling) (Access signaling)
|<--------------------------------------------------------->|
end-to-end QoS signaling
Figure 3. Signaling mapping (stage 3)
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4. Other Issues
The problems arise from the tunneling such like mobile IPv6
mechanisms are not fully exploited in this version of document. Also
the more detail procedure of signaling packet processing in CR-LDP
and RSVP-TE in case of the explicit route information is carried in
Routing Option header should be considered. We are studying about
these issues.
5. IANA Considerations
The value field described in appendix SHOULD be registered and
maintained by IANA. The New values SHOULD be to be assigned via IETF
Consensus as defined in [RFC 2434].
6. Security Considerations
This document does not have any security concerns. The security
requirements using this document are described in the referenced
documents.
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Appendix. The delivering methods of signaling messages in IPv6 network
In this appendix, we will describe the delivering methods of existing
signaling protocols in IPv6 networks via using IPv6 extension headers.
The use of these methods in existing signaling protocols is discussed
in the last of this section.
1. RSVP/RSVP-TE for IPv6 (including RSVP-TE extension for GMPLS)
o Using Router Alert Option
Router alert option [RFC 2711] within the IPv6 Hop-by-Hop option
header has the semantic "routers should examine the datagram more
closely". Using this option, IPv6 datagram containing signaling
messages are indicated and taken actions.
The router alert option has the following format:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0 0 0|0 0 1 0 1|0 0 0 0 0 0 1 0| Value (2 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
length = 2
The first three bits of the first byte are zero and the value 5 in
the remaining five bits is the Hop-by-Hop Option Type number.
[RFC 2460] specifies the meaning of the first three bits. By
zeroing all three, this specification requires that nodes not
recognizing this option type should skip over this option and
continues processing the header and that the option must not change
en route.
There MUST only be one option of this type, regardless of value,
per Hop-by-Hop header.
Value: A 2 octets code in network byte order with the following
values
0 Datagram contains a Multicast Listener Discovery
message [RFC 2710].
1 Datagram contains RSVP message.
2 Datagram contains an Active Networks message.
3-65535 Reserved to IANA for future use.
Alignment requirement: 2n+0
Values are registered and maintained by the IANA.
We suggest the new value (= 3) for RSVP-TE messages. The value 3 is
REQUIRED the approval of IETF and SHOULD be assigned by IANA. Other
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signaling messages MAY be added. In this case, the value for new
signaling message SHOULD be assigned by IANA.
The described method has some advantages and disadvantages. It is not
necessary to implement the new protocol for signaling. The existing
signaling message is used without change. However, all IPv6 datagram
containing a signaling message MUST contain this option within the
IPv6 Hop-by-Hop Option Header of such datagram. The additional option
header is redundant.
o Next Header for signaling
This method uses the new Next Header value for signaling message.
Message body includes signaling messages like RSVP/RSVP-TE. Every
signaling message is preceded by an IPv6 header or by more IPv6
extension headers. The signaling message is identified by a Next
Header value in the immediately preceding header.
The signaling messages have the following general format:
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header | Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+ +
| Message Body |
+ (signaling message) +
Version 4-bit Internet Protocol version number = 6.
Traffic Class 8-bit traffic class field.
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Flow Label 20-bit flow label.
Payload Length 16-bit unsigned integer. Length of the IPv6
payload, i.e., the rest of the packet
following this IPv6 header, in octets
Next Header 8-bit selector. Identifies the type of
signaling message immediately following the
IPv6 header. Uses the same values as the
IPv4 Protocol field [RFC 1700 et seq.].
Hop Limit 8-bit unsigned integer. Decremented by 1 by
each node that forwards the packet. The
packet is discarded if Hop Limit is
decremented to zero.
Source Address 128-bit address of the originator of the
packet.
Destination Address 128-bit address of the intended recipient of
the packet (possibly not the ultimate
recipient, if a Routing header is present).
For this method, we MUST assign the new Next Header value of IPv6
header. Currently, RSVP is already assigned the value 46 decimal in
[RFC 1700].
For example, if the Next Header value of IPv6 header is 46 decimal
the following ISMP message is RSVP message. The Next Header value of
other unassigned signaling messages SHOULD be assigned by IANA.
This second method may be used for the signaling protocols which are
running on the IP layer.
Compared with the method using router alert option, this method is
very simple because of no additional extension header. Therefore, the
complexity of processing is reduced but this new function MUST be
implemented within IPv6 header.
Note) The signaling protocols, like SIP, that are used for end-to-
end path may use the option TLVs to indicate the presence of the
signaling information. We already know that the real-time service
cannot be served without support of intermediate node. If some
end-to-end sessions are need to be guaranteed to their perceived
QoS, the intermediate nodes those are on the path may use the
information to do something related with QoS implicitly.
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2. CR-LDP for IPv6 (including CR-LDP extension for GMPLS)
In the case of RSVP-TE, if the header of a packet is indicating "This
packet carries the signaling information." then the intermediate
routers and the end host can make different treatment on just only
look at the IP header.
On the other hand, like CR-LDP, the protocol running on the TCP(UDP)
layer may also make use of the benefit that IP header already notify
the existence of signaling information in the payload of IP packet.
Originally in the CR-LDP protocol, the signaling information is
transferred along the path per hop. If a router sees the notification
of signaling information in the IP header, it can forward the
signaling packet and processing the signaling information
simultaneously. So the forwarding direction of packet can be done
faster than old mechanisms.
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References
[RFC 1700] J. Reynolds et al.. "Assign Numbers", October 1994
[RFC 2205] R. Braden, Ed. et al.. "Resource ReSerVation Protocol
(RSVP) -- Version 1 Functional Specification", September
1997
[RFC 2210] J. Wroclawski et al.. "The use of RSVP with IETF
Integrated Services", September 1997
[RFC 2434] T. Narten, et al.. "Guidelines for Writing an IANA
Considerations Section in RFCs", October 1998
[RFC 2460] S. Deering, et al.. "Internet Protocol, Version 6 (IPv6)
Specification", December 1998
[RFC 2463] A. Conta, et al.. "Internet Control Message Protocol
(ICMPv6) for the Internet Protocol Version 6 (IPv6)
Specification", December 1998
[RFC 2475] S. Blake, et al.. "An Architecture for Differentiated
Services", December 1998
[RFC 2543] M. Handley, et al.. "SIP: Session Initiation Protocol",
March, 1999
[RFC 2710] S. Deering, et al.. "Multicast Listener Discovery (MLD)
for IPv6", October 1999
[RFC 2711] C. Partridge, et al.. "IPv6 Router Alert Option", October
1999
[RFC 3031] E. Rosen, et al.. "Multiprotocol Label Switching
Architecture", January 2001
[RFC 3036] L. Andersson, et al.. "LDP Specification", January 2001
[RFC 3209] D. Awduche et al.. "RSVP-TE: Extensions to RSVP for LSP
Tunnels", December 2001
[RFC 3212] B. Jamoussi, et al.. "Constraint-Based LSP Setup using
LDP", January 2002
[CR-LDP 06] Peter Ashwood-Smith, et al.. "Generalized MPLS Signaling
- CR-LDP Extensions", Internet-Draft draft-ietf-mpls-
generalized-cr-ldp-06.txt, work in progress, April 2002
[RSVP-TE 07] Lou Berger, et al.. "Generalized MPLS Signaling - RSVP-
TE Extensions", Internet-Draft draft-ietf-mpls-
generalized-rsvp-te-07.txt, work in progress, April 2002
Choi et al Expires - December 2002 [Page 14]
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[Flow Label 02] J. Rajahalme, et al.. "IPv6 Flow Label Specification",
Internet-Draft draft-ietf-ipv6-flow-label-02.txt, work in
progress, June 2002
Acknowledgements
This work was supported in part by KOSEF(Korea Science and
Engineering Foundation) and MIC(Ministry of Information and
Communication) of Korean government.
Author's Addresses
Jun Kyun Choi
Information and Communications University (ICU)
58-4 Hwa Ahm Dong, Yuseong, Daejeon
Korea 305-732
Phone: +82-42-866-6122
Email: jkchoi@icu.ac.kr
Gyu Myoung Lee
Information and Communications University (ICU)
58-4 Hwa Ahm Dong, Yuseong, Daejeon
Korea 305-732
Phone: +82-42-866-6231
Email: gmlee@icu.ac.kr
Ki Young Jung
Information and Communications University (ICU)
58-4 Hwa Ahm Dong, Yuseong, Daejeon
Korea 305-732
Phone: +82-42-866-6182
Email: jjungki@icu.ac.kr
Woo Seop Rhee
Electronics and Telecommunications Research Institute (ETRI)
161 Kajeong, Youseong, Daejeon
Korea 305-350
Phone: +82-42-860-5324
Email: wsrhee@etri.re.kr
Document: draft-choi-ipv6-signaling-02.txt
Expiration Date: December 2002
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