draft-ietf-mpls-entropy-label-03.txt   draft-ietf-mpls-entropy-label-04.txt 
Network Working Group K. Kompella Network Working Group K. Kompella
Internet-Draft J. Drake Internet-Draft J. Drake
Updates: 3031, 5036 (if approved) Juniper Networks Updates: 3031, 5036 (if approved) Juniper Networks
Intended status: Standards Track S. Amante Intended status: Standards Track S. Amante
Expires: November 10, 2012 Level 3 Communications, LLC Expires: January 11, 2013 Level 3 Communications, LLC
W. Henderickx W. Henderickx
Alcatel-Lucent Alcatel-Lucent
L. Yong L. Yong
Huawei USA Huawei USA
May 9, 2012 July 10, 2012
The Use of Entropy Labels in MPLS Forwarding The Use of Entropy Labels in MPLS Forwarding
draft-ietf-mpls-entropy-label-03 draft-ietf-mpls-entropy-label-04
Abstract Abstract
Load balancing is a powerful tool for engineering traffic across a Load balancing is a powerful tool for engineering traffic across a
network. This memo suggests ways of improving load balancing across network. This memo suggests ways of improving load balancing across
MPLS networks using the concept of "entropy labels". It defines the MPLS networks using the concept of "entropy labels". It defines the
concept, describes why entropy labels are useful, enumerates concept, describes why entropy labels are useful, enumerates
properties of entropy labels that allow maximal benefit, and shows properties of entropy labels that allow maximal benefit, and shows
how they can be signaled and used for various applications. how they can be signaled and used for various applications.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 10, 2012. This Internet-Draft will expire on January 11, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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The term ingress (or egress) LSR is used interchangeably with ingress The term ingress (or egress) LSR is used interchangeably with ingress
(or egress) LER. The term application throughout the text refers to (or egress) LER. The term application throughout the text refers to
an MPLS application (such as a VPN or VPLS). an MPLS application (such as a VPN or VPLS).
A label stack (say of three labels) is denoted by <L1, L2, L3>, where A label stack (say of three labels) is denoted by <L1, L2, L3>, where
L1 is the "outermost" label and L3 the innermost (closest to the L1 is the "outermost" label and L3 the innermost (closest to the
payload). Packet flows are depicted left to right, and signaling is payload). Packet flows are depicted left to right, and signaling is
shown right to left (unless otherwise indicated). shown right to left (unless otherwise indicated).
The term 'label' is used both for the entire 32-bit label and the 20- The term 'label' is used both for the entire 32-bit label stack entry
bit label field within a label. It should be clear from the context and the 20-bit label field within a label stack entry. It should be
which is meant. clear from the context which is meant.
1.2. Motivation 1.2. Motivation
MPLS is very successful generic forwarding substrate that transports MPLS is very successful generic forwarding substrate that transports
several dozen types of protocols, most notably: IP, PWE3, VPLS and IP several dozen types of protocols, most notably: IP, PWE3, VPLS and IP
VPNs. Within each type of protocol, there typically exist several VPNs. Within each type of protocol, there typically exist several
variants, each with a different set of load balancing keys, e.g., for variants, each with a different set of load balancing keys, e.g., for
IP: IPv4, IPv6, IPv6 in IPv4, etc.; for PWE3: Ethernet, ATM, Frame- IP: IPv4, IPv6, IPv6 in IPv4, etc.; for PWE3: Ethernet, ATM, Frame-
Relay, etc. There are also several different types of Ethernet over Relay, etc. There are also several different types of Ethernet over
PW encapsulation, ATM over PW encapsulation, etc. as well. Finally, PW encapsulation, ATM over PW encapsulation, etc. as well. Finally,
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load balancing information. However, they MUST NOT have values in load balancing information. However, they MUST NOT have values in
the reserved label space (0-15) [IANA MPLS Label Values]. To ensure the reserved label space (0-15) [IANA MPLS Label Values]. To ensure
that they are not used inadvertently for forwarding, entropy labels that they are not used inadvertently for forwarding, entropy labels
SHOULD have a TTL of 0. The CoS field of an entropy label can be set SHOULD have a TTL of 0. The CoS field of an entropy label can be set
to any value deemed appropriate. to any value deemed appropriate.
Since entropy labels are generated by an ingress LSR, an egress LSR Since entropy labels are generated by an ingress LSR, an egress LSR
MUST be able to distinguish unambiguously between entropy labels and MUST be able to distinguish unambiguously between entropy labels and
application labels. This is accomplished by REQUIRING that the label application labels. This is accomplished by REQUIRING that the label
immediately preceding an entropy label (EL) in the MPLS label stack immediately preceding an entropy label (EL) in the MPLS label stack
be an 'entropy label indicator' (ELI). The ELI is a reserved label be an 'entropy label indicator' (ELI), where preceding means closer
with value (TBD by IANA). An ELI MUST have 'Bottom of Stack' (BoS) to the top of the label stack (farther from bottom of stack
bit = 0 ([RFC3032]). The TTL SHOULD be set to whatever value the indication). The ELI is a reserved label with value (TBD by IANA).
label above it in the stack has. The CoS field can be set to any An ELI MUST have 'Bottom of Stack' (BoS) bit = 0 ([RFC3032]). The
value deemed appropriate; typically, this will be the value in the TTL SHOULD be set to whatever value the label above it in the stack
label above the ELI in the label stack. has. The CoS field can be set to any value deemed appropriate;
typically, this will be the value in the label above the ELI in the
label stack.
Entropy labels are useful for pseudowires ([RFC4447]). [RFC6391] Entropy labels are useful for pseudowires ([RFC4447]). [RFC6391]
explains how entropy labels can be used for RFC 4447-style explains how entropy labels can be used for RFC 4447-style
pseudowires, and thus is complementary to this memo, which focuses on pseudowires, and thus is complementary to this memo, which focuses on
how entropy labels can be used for tunnels, and thus for all other how entropy labels can be used for tunnels, and thus for all other
MPLS applications. MPLS applications.
4. Data Plane Processing of Entropy Labels 4. Data Plane Processing of Entropy Labels
4.1. Egress LSR 4.1. Egress LSR
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