draft-ietf-mpls-upstream-label-06.txt   draft-ietf-mpls-upstream-label-07.txt 
Network Working Group R. Aggarwal Network Working Group R. Aggarwal
Internet Draft Juniper Networks Internet Draft Juniper Networks
Category: Standards Track Category: Standards Track
Expiration Date: December 2008 Y. Rekhter Expiration Date: January 2009 Y. Rekhter
Juniper Networks Juniper Networks
E. Rosen E. Rosen
Cisco Systems, Inc. Cisco Systems, Inc.
June 05, 2008 July 10, 2008
MPLS Upstream Label Assignment and Context-Specific Label Space MPLS Upstream Label Assignment and Context-Specific Label Space
draft-ietf-mpls-upstream-label-06.txt draft-ietf-mpls-upstream-label-07.txt
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
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1 Specification of requirements ......................... 2 1 Specification of requirements ......................... 2
2 Introduction .......................................... 2 2 Introduction .......................................... 2
3 Context-Specific Label Space .......................... 3 3 Context-Specific Label Space .......................... 3
4 Upstream Label Assignment ............................. 4 4 Upstream Label Assignment ............................. 4
4.1 Upstream-Assigned and Downstream-Assigned Labels ...... 5 4.1 Upstream-Assigned and Downstream-Assigned Labels ...... 5
5 Assigning Upstream-Assigned Labels .................... 5 5 Assigning Upstream-Assigned Labels .................... 5
6 Distributing Upstream-Assigned Labels ................. 6 6 Distributing Upstream-Assigned Labels ................. 6
7 Upstream Neighbor Label Space ......................... 7 7 Upstream Neighbor Label Space ......................... 7
8 Context Label on LANs ................................. 9 8 Context Label on LANs ................................. 9
9 Usage of Upstream-Assigned Labels ..................... 10 9 Usage of Upstream-Assigned Labels ..................... 11
10 IANA Considerations ................................... 11 10 IANA Considerations ................................... 11
11 Security Considerations ............................... 11 11 Security Considerations ............................... 11
12 Acknowledgements ...................................... 11 12 Acknowledgements ...................................... 12
13 References ............................................ 12 13 References ............................................ 12
13.1 Normative References .................................. 12 13.1 Normative References .................................. 12
13.2 Informative References ................................ 12 13.2 Informative References ................................ 12
14 Author's Address ...................................... 12 14 Author's Address ...................................... 12
15 Intellectual Property Statement ....................... 13 15 Intellectual Property Statement ....................... 13
16 Copyright Notice ...................................... 13 16 Copyright Notice ...................................... 13
1. Specification of requirements 1. Specification of requirements
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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Section 8 describes how the context label is assigned. Rd maintains Section 8 describes how the context label is assigned. Rd maintains
a separate "Upstream Neighbor Label Space" for Ru. The "context" of a separate "Upstream Neighbor Label Space" for Ru. The "context" of
this packet, i.e. Ru's upstream neighbor label space, in which L was this packet, i.e. Ru's upstream neighbor label space, in which L was
reserved, is determined by Rd from the top context label and the reserved, is determined by Rd from the top context label and the
interface on which the packet is received. The ether type in the data interface on which the packet is received. The ether type in the data
link frame is set to indicate that the top label is upstream- link frame is set to indicate that the top label is upstream-
assigned. The second label in the stack is L. assigned. The second label in the stack is L.
8. Context Label on LANs 8. Context Label on LANs
The procedure described below applies to LSRs using IPv4 and does not
apply to LSRs only using IPv6. A solution for IPv6 LSRs is outside
the scope of this document.
For a labeled packet with an ether type of 'upstream label For a labeled packet with an ether type of 'upstream label
assignment' the top label is used as the context. The context label assignment' the top label is used as the context. The context label
value is assigned by the upstream LSR and advertised to the value is assigned by the upstream LSR and advertised to the
downstream LSRs. Mechanisms for advertising the context label will downstream LSRs. Mechanisms for advertising the context label will be
be provided by the label distribution protocol between the upstream provided by the label distribution protocol between the upstream and
and downstream LSRs. The description of such a mechanism is outside downstream LSRs. The description of such a mechanism is outside the
the scope of this document. scope of this document.
The context label assigned by a LSR on a LAN interface MUST be unique The context label assigned by an LSR for use on a particular LAN
across all the context labels assigned by other LSRs on the same LAN. interface MUST be unique across all the context labels assigned by
Each LAN interface is normally configured with a primary IPv4 address other LSRs for use on the same LAN. When a labeled packet is received
that is unique on that LAN. The host part of the IPv4 address, from the LAN, the context label MUST be looked up in the context of
identified by the network mask, is unique. If the IPv4 network mask the LAN interface on which the packet is received.
is greater then 12 bits, it is possible to map the remaining 20 bits
into an unique context label value. This enables the LSRs on the LAN This document provides two methods which an LSR can use to choose a
to assign an unique context label without the need for additional context label to advertise on a particular LAN.
configuration. To avoid assigning context label values that fall into
the reserved label space range [RFC3032], the value of the host part The first method requires that each LSR be provisioned with a 20-bit
of the IPv4 address is offset with 0x10, if this value is not greater context label for each LAN interface on which a context label is
required. It is then left to the provisioning system to make sure
that an assigned context label is unique across the corresponding
LAN.
The second method allows the context labels to be auto-generated, but
is only applicable if each LSR on the LAN has an IPv4 address as its
primary IP address for the corresponding LAN interface. (If the LAN
contains LSRs that have only IPv6 addresses for the LAN interface,
then the first method is used.)
Suppose that each LAN interface is configured with a primary IPv4
address that is unique on that LAN. The host part of the IPv4
address, identified by the network mask, is unique. If the IPv4
network mask is greater then 12 bits, it is possible to map the
remaining 20 bits into a unique context label value. This enables the
LSRs on the LAN to automatically generate a unique context label. To
ensure that auto-generated context label values do not fall into the
reserved label space range [RFC3032], the value of the host part of
the IPv4 address is offset with 0x10, if this value is not greater
then 0xFFFEF. Values of the host part of the IPv4 address greater then 0xFFFEF. Values of the host part of the IPv4 address greater
then 0xFFFEF are not allowed to be used as the context label. then 0xFFFEF are not allowed to be used as context labels.
Consider LSRs Rm (downstream) connected to Ru1 (upstream) on a LAN Consider LSRs Rm (downstream) connected to Ru1 (upstream) on a LAN
interface and to Ru2 (upstream) on a different LAN interface. Rm interface and to Ru2 (upstream) on a different LAN interface. Rm
could receive a context label value derived from the LAN interface could receive a context label value derived from the LAN interface
from Ru1 and from Ru2. It is possible that the context label values from Ru1 and from Ru2. It is possible that the context label values
used by Ru1 and Ru2 are the same. This would occur if the LAN used by Ru1 and Ru2 are the same. This would occur if the LAN
interfaces of both Ru1 and Ru2 are configured with a primary IPv4 interfaces of both Ru1 and Ru2 are configured with a primary IPv4
address where the lowest 20 bits are equal. To avoid these conflicts address where the lowest 20 bits are equal. However, this does not
the context label MUST be looked up in the context of the LAN create any ambiguity, as it has already been stated that the context
interface on which the packet is received. A receiving LSR that label MUST be looked up in the context of the LAN interface on which
receives a packet with a context label of Lc over LAN interface the packet is received.
identified by X, MUST use the label space specific to X to lookup Lc.
This determines the context to lookup the label below Lc in the label
stack.
9. Usage of Upstream-Assigned Labels 9. Usage of Upstream-Assigned Labels
A typical use case of upstream-assigned labels is for MPLS multicast A typical use case of upstream-assigned labels is for MPLS multicast
and is described here for illustration. This use case arises when an and is described here for illustration. This use case arises when an
upstream LSR Ru is adjacent to several downstream LSRs <Rd1...Rdn> in upstream LSR Ru is adjacent to several downstream LSRs <Rd1...Rdn> in
a LSP LSP1 AND Ru is connected to <Rd1...Rdn> via a multi-access a LSP LSP1 AND Ru is connected to <Rd1...Rdn> via a multi-access
media or tunnel AND Ru wants to transmit a single copy of a MPLS media or tunnel AND Ru wants to transmit a single copy of a MPLS
packet on the LSP to <Rd1...Rdn>. In the case of a tunnel Ru can packet on the LSP to <Rd1...Rdn>. In the case of a tunnel Ru can
distribute an upstream-assigned label L that is bound to the FEC for distribute an upstream-assigned label L that is bound to the FEC for
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