Internet DRAFT - draft-chenpeng-mpls-ldp-ext
draft-chenpeng-mpls-ldp-ext
Networking Working Group Ran. Chen
Internet-Draft Shaofu. Peng
Intended status: Standards Track ZTE Corporation
Expires: November 10, 2017 May 09, 2017
LDP Extensions for FEC elements sharing label
draft-chenpeng-mpls-ldp-ext-01
Abstract
Label Distribution Protocol (LDP) is defined in [RFC5036] for
distribution of labels inside one MPLS domain. It defined how to
associate a Forwarding Equivalence Class (FEC) with each label it
distributes. A FEC is a list of one or more FEC elements, but it
does not describe operations how to achieve one or more FEC element
share the same label.
Currently Label resources are getting more and more nervous, and it
is necessary to save the label resources. This document defines
extensions to the LDP protocol to achieve one or more FEC element
share the same label.
Status of This Memo
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This Internet-Draft will expire on November 10, 2017.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 2
3. LDP Extension . . . . . . . . . . . . . . . . . . . . . . . . 2
3.1. Host-parasitism FEC Relationship TLV . . . . . . . . . . 3
3.2. Label Borrowing Message . . . . . . . . . . . . . . . . . 4
4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Egress Operation . . . . . . . . . . . . . . . . . . . . 4
4.2. Ingress/Transit Operation . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. Normative references . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
Label Distribution Protocol (LDP) is defined in [RFC5036] for
distribution of labels inside one MPLS domain. It defined how to
associate a Forwarding Equivalence Class (FEC) with each label it
distributes. A FEC is a list of one or more FEC elements, but it
does not describe operations how to achieve one or more FEC element
share the same label.
Currently Label resources are getting more and more nervous, and it
is necessary to save the label resources. This document defines
extensions to the LDP protocol to achieve one or more FEC element
share the same label.
2. Conventions used in this document
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 RFC2119.
3. LDP Extension
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3.1. Host-parasitism FEC Relationship TLV
The following section describes the protocol extensions required to
support one or more FEC element share the same label.
Labels are bound to Forwarding Equivalence Classes (FECs). A Host-
parasitism FEC Relationship is a list of one or more FEC elements.
The FEC Relationship TLV encodes FEC items.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|1| H-P Relationship(TBD) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix(2) | Host Address Family | PreLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Host Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix(2) | Parasitic Address Family | PreLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parasitic Prefix 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| ... ... |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix(2) | Parasitic Address Family | PreLen |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Parasitic Prefix n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1
The FEC Relationship TLV contains a Host-FEC element, and 0 or many
Parasitic-FEC elements. Both Host-FEC element and the Parasitic-FEC
element are use the same format as defined in [RFC5036].
The type of the FEC Elements is 0x02(prefix).The Host-FEC indicates
Label Lender, and the Parasitic-FEC indicates Label borrowing.
Sequence Number Specifies a 4 octet unsigned sequence number that
identifies the sequence number of the Host-parasitism FEC
Relationship. The greater the Sequence Number, the more new the
Host-parasitism FEC Relationship. if the difference between the
larger one and the smaller one is more than half of the value of a 4
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octet unsigned integer, it indicates that there is a turnover, and
the smaller value of the Sequence Number , the more new the Host-
parasitism FEC Relationship.
3.2. Label Borrowing Message
The document defines a new LDP message: Label Borrowing Message. An
LSR sends a Label Borrowing message to an LDP peer to advertise label
borrowing relationship to the peer. The Label Borrowing message Must
include a Host-parasitism FEC Relationship TLV.
The encoding for the Label Borrowing message is:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Label Borrowing (TBD) | Message Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Action | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Host-parasitism FEC Relationship TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2
U-bit: The value is set to 1, it indicates the unknown TLV MUST be
silently ignored and the rest of the message processed as if the
unknown TLV did not exist.
Message ID: 32-bit value used to identify this message.
Action: Set to 1, it indicates Label borrowing. Set to 0, it
indicates Label does not borrow.
4. Operations
4.1. Egress Operation
The Egress may involve one or more of the following actions:
o A Egress node advertises Label Mapping messages for the Host-FEC
label to one or more LDP peers, The LDP label distribution
procedures is the same as described in [RFC5036].
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o According to local policy that is configed on Egress node, all or
part of the Parasitic-FECs can share the same label with the Host-
FEC. The Egress node MUST advertises a Label Borrowing Message
included the Host-parasitism FEC Relationship TLV with action set
to 1. If the local policy is coarsness-grained that enforced all
Parasitic-FECs to share the Host-FEC's label, the Host-parasitism
FEC Relationship TLV can only contain the single Host-FEC element,
and Parasitic-FECs elements are empty. Otherwise, the Host-
parasitism FEC Relationship TLV need contain not only the Host-FEC
element, but also specific Parasitic-FECs elements who need to
share Host-FEC's label due to a local fine-grained policy.
o When the Host-FEC label is available, and if due to a local
coarsness or fine-grained policy that all Parasitic-FECs which
borrowed label from the Host-FEC didnt borrow again, the Egress
node MUST advertises a Label Borrowing Message included the Host-
parasitism FEC Relationship TLV with action set to 0, only contain
that single Host-FEC element, and Parasitic-FECs elements are
empty. Otherwise, if due to a local fine-grained policy, some
Parasitic-FECs didnot want to borrow the Host-FEC's label, but
there are always any other Parasitic-FECs left to share label, an
updated Label Borrowing Message included the Host-parasitism FEC
Relationship TLV with action set to 1 need to be advertised,
contain the Host-FEC element and the specific Parasitic-FECs
elements.
4.2. Ingress/Transit Operation
An LSR which received a Label Borrowing Message from an LDP peer may
involve one or more of the following actions:
o Maintain the up-to-date Host-parasitism FEC Relationship. It will
compare the sequence number in the received Label Borrow Message
and the existed locally maintained Host-parasitism FEC
Relationship data. If the Label Borrow Message is newer than the
locally maintained data, it will overwrite the later, otherwise it
will be ignored. If the Host-parasitism FEC Relationship only
contained a single Host-FEC, the Parasitic-FECs could be
determined by checking IGP/BGP prefixes whose original advertised
router-id are same as the Host-FEC, and also by local FEC-
policy(i.e. which IGP/BGP prefix could be installed as an LDP FEC
due to local FEC-policy).
o Based on the borrowed label get from the up-to-date Host-
parasitism FEC Relationship data, Install ILM entries at the
transit node and FTN entries at the ingress node for Parasitic-
FECs. The outgoing label of the Parasitic-FEC's FTN entry will be
same as the one of the Host-FEC's FTN entry. Both the incoming
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label and outgoing label of the parasitic-FEC's ILM entry will be
same as the ones of the Host-FEC's ILM entry.
o Transmission of the up-to-date Label Borrowing message to one or
more other LDP peers;
Note that the traditional process of received Label Mapping/Withdraw
Message for an FEC MUST NOT be affected by the process of the Label
Borrow Message if the FEC is also a Parasitic-FEC according to the
up-to-date Host-parasitism FEC Relationship data. That is, the
priority of the traditional process is higher.
5. Security Considerations
TBD.
6. Acknowledgements
TBD.
7. IANA Considerations
TBD.
8. Normative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<http://www.rfc-editor.org/info/rfc3031>.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
October 2007, <http://www.rfc-editor.org/info/rfc5036>.
[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
March 2016, <http://www.rfc-editor.org/info/rfc7794>.
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Authors' Addresses
Ran Chen
ZTE Corporation
No.50 Software Avenue,Yuhuatai District
Nanjing, Jiangsu Province 210012
China
Phone: +86 025 88014636
Email: chen.ran@zte.com.cn
Shaofu Peng
ZTE Corporation
No.68 Zijinghua Road,Yuhuatai District
Nanjing, Jiangsu Province 210012
China
Email: peng.shaofu@zte.com.cn
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