Internet DRAFT - draft-fang-mpls-label-forwarding-no-swap
draft-fang-mpls-label-forwarding-no-swap
INTERNET-DRAFT Luyuan Fang
Intended Status: Standards Track Microsoft
Expires: May 7, 2016 Fabio Chiussi
Barak Gafni
Mellanox
Nabil Bitar
Alcatel Lucent
Zhenbin Li
Huawei
Rob Raszuk
Bloomberg
Andrew Qu
MediaTek
November 4, 2015
MPLS Label Forwarding with No Swapping
draft-fang-mpls-label-forwarding-no-swap-02
Abstract
This document defines MPLS label forwarding operation with no label
swapping as a new MPLS label operation extension to the existing
basic forwarding operation of label push, pop, and swap.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
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Copyright and License Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Label Forwarding Operation as Defined in RFC3031 . . . . . . . 4
4. Label Forwarding with No Swap . . . . . . . . . . . . . . . . . 5
5. Proposed Text to Update RFC3031 . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1 Normative References . . . . . . . . . . . . . . . . . . . 7
8.2 Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
MPLS forwarding operation as defined in [RFC3031] has three basic
operations that must be performed on the labels at the network nodes:
push, swap, and pop. This document describes an additional operation
action: label forwarding with no swap. Currently, using the same
label as both incoming and outgoing label is typically achieved by
"swapping" the incoming label with an identical outgoing label. In
order to improve processing efficiency and memory usage reduction, a
simple label forwarding operation with no swap is desirable. This
operation should be specified in [RFC3031]
When MPLS Architecture [RFC3031] was defined, the three types of
label operation were sufficient, since labels were always only
locally meaningful. Label swap operation is performed at a Label
Switched Router (LSR) which is not an MPLS edge node, while label
push and pop can be performed at an MPLS edge node for label
imposition and deposition. Penultimate hop popping can also be
performed at the penultimate hop for improved efficiency when
appropriate. Since the labels are assigned independently in
distributed fashion in a non-traffic engineered basic MPLS networks,
it is not possible nor necessary to coordinate the label assignment.
Therefore, the label swapping function is sufficient and effective
for LSR.
With the increased interests and large scale development of Software-
Defined Networking (SDN), several new use cases have emerged where
domain-wide labels are used. For example, central controller assigned
MPLS labels become one of the options for MPLS based forwarding.
Using a single label is used to traverse multiple hops along the
Label Switched Path (LSP) become desirable. Relevant examples of the
use of domain-wide labels are described in
[I-D.fang-mpls-hsdn-for-hsdc], [I-D.ietf-spring-segment-routing], and
[I-D.li-mpls-global-label-usecases]
Domain-wide labels do not need to be swapped at the switches.
Therefore, in order to allow efficient handling of domain-wide
labels, there is a need to extend the label operation with one more
action type - forwarding with no swap.
The performance and memory efficiency can be increased by performing
simple forwarding function than swapping the labels with the
identical identifier. This does not otherwise change the fundamentals
of MPLS architecture and label encoding as defined by [RFC3031]
[RFC3032].
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2. Terminology
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 [RFC2119].
o Incoming Label Map (ILM): It maps each incoming label to a set of
NHLFEs. It is used when forwarding packets that arrive as labeled
packets.
o Label forwarding: A simple forwarding paradigm allowing
streamlined forwarding of data by using labels to identify classes
of data packets which are treated indistinguishably when
forwarding without label swapping.
o Label swap: The basic existing forwarding operation consisting of
looking up an incoming label to determine the outgoing label
encapsulation, port, and other data handling information.
o Label swapping: A forwarding paradigm allowing streamlined
forwarding of data by using labels to identify classes of data
packets which are treated indistinguishably when forwarding.
o Label Switched Path (LSP): The path through one or more LSRs at
one level of the hierarchy followed by a packets in a particular
forwarding equivalence class (FEC).
o Label Switching Router (LSR): An MPLS node which is capable of
forwarding native L3 packets.
o MPLS edge node: An MPLS node that connects an MPLS domain with a
node which is outside of the domain, either because it does not
run MPLS, and/or because it is in a different domain. Note that
if an LSR has a neighboring host which is not running MPLS, that
that LSR is an MPLS edge node.
o NHLFE: Next Hop Label Forwarding Entry
o Software-Defined Networking (SDN): an architecture that decouples
the network control and forwarding functions to enable the network
control to be directly programmable and the underlying
infrastructure to be abstracted for applications and network
services.
3. Label Forwarding Operation as Defined in RFC3031
Section 3.10 in [RFC3031] states the following:
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"The "Next Hop Label Forwarding Entry" (NHLFE) is used when
forwarding a labeled packet. It contains the following
information:
1. the packet's next hop
2. the operation to perform on the packet's label stack; this is one
of the following operations:
a) replace the label at the top of the label stack with a
specified new label
b) pop the label stack
c) replace the label at the top of the label stack with a
specified new label, and then push one or more specified new
labels onto the label stack.
..."
Section 3.13 in [RFC3031] states the following:
"Label swapping is the use of the following procedures to forward a
packet. In order to forward a labeled packet, a LSR examines the
label at the top of the label stack. It uses the ILM to map this
label to an NHLFE. Using the information in the NHLFE, it determines
where to forward the packet, and performs an operation on the
packet's label stack. It then encodes the new label stack into the
packet, and forwards the result."
It is clear that, in order to forward a labeled packet, [RFC3031]
mandates to perform one of three possible operations: swap, pop, or
swap/push.
Therefore, in order to forward a labeled packet with a label that
does not need to be swapped according to the standard, the label at
the top of the label stack must be swapped with an identical label.
Simply forwarding the labeled packet without swapping the label does
not conform with [RFC3031].
4. Label Forwarding with No Swap
Label forwarding is the use of the following procedures to forward a
packet.
Same as in [RFC3031], in order to forward a labeled packet, a LSR
examines the label at the top of the label stack. It uses the ILM to
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map this label to an NHLFE. Using the information in the NHLFE, it
determines where to forward the packet, and performs an operation on
the packet's label stack.
Unlike in label swapping, label forwarding does not remove the
incoming label and encodes the new label stack into the packet as in
label swapping, it forwards the packet with the same label stack as
the incoming stack, to the outgoing interface. Other processing may
be involved in selecting the outgoing interface, for example, load
balancing through IP deader hashing or use of Entropy label
[RFC6790].
5. Proposed Text to Update RFC3031
In order to allow efficient processing of domain-wide labels, which
do not need to be swapped, we propose to add a fourth possible
operation "Forward No Swap" to [RFC3031].
Accordingly, [RFC3031] should be modified as follows.
1. the packet's next hop
2. the operation to perform on the packet's label stack; this is one
of the following operations:
a) replace the label at the top of the label stack with a
specified new label
b) pop the label stack
c) replace the label at the top of the label stack with a
specified new label, and then push one or more specified new
labels onto the label stack
d) keep the label at the top of the label stack unchanged.
..."
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6. Security Considerations
The MPLS label forwarding operation specified herein does not
raise any security issues that are not already present in either
the MPLS architecture [RFC3031] or in MPLS label encoding
[RFC3032].
In addition, general MPLS and GMPLS considerations and MPLS
security defense techniques are documented in [RFC5920].
7. IANA Considerations
None.
8. References
8.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, January 2001.
[RFC6790] Kompella, K., et.al, "The Use of Entropy Labels in MPLS
Forwarding", November 2012.
8.2 Informative References
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[I-D.fang-mpls-hsdn-for-hsdc] L. Fang, et al., "MPLS-Based
Hierarchical SDN for Hyper-Scale DC/Cloud", draft-fang-
mpls-hsdn-for-hsdc-04 (work in progress), July 2015.
[I-D.ietf-spring-segment-routing] Filsfils, C. et al., "Segment
Routing Architecture", draft-ietf-spring-segment-routing-
06 (work in progress), October 2015.
[I-D.li-mpls-global-label-usecases] Z. Li, et al., "Usecases of MPLS
Global Label, draft-li-mpls-global-label-usecases-03 (work
in progress), October 2015.
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Authors' Addresses
Luyuan Fang
Microsoft
5600 148th Ave NE
Redmond, WA 98052
Email: lufang@microsoft.com
Fabio Chiussi
Seattle, WA 98116
Email: fabiochiussi@gmail.com
Barak Gafni
Mellanox
6 Habarzel St.
Tel Aviv, Israel
Email: gbarak@mellanox.com
Nabil Bitar
Alcatel Lucent
Zhenbin Li
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Robert Raszuk
Email: robert@raszuk.net
Andrew Qu
MediaTek
2860 Junction Ave.
San Jose, CA 95134
Email: andrew.qu@mediatek.com
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