draft-ietf-pim-mtid-08.txt   draft-ietf-pim-mtid-09.txt 
PIM WG Yiqun Cai PIM WG Yiqun Cai
Internet Draft Heidi Ou Internet Draft Heidi Ou
Intended Status: Proposed Standard Intended Status: Proposed Standard
Expires: December 10, 2011 Cisco Systems, Inc. Expires: February 17, 2012 Cisco Systems, Inc.
June 10, 2011 August 17, 2011
PIM Multi-Topology ID (MT-ID) Join Attribute PIM Multi-Topology ID (MT-ID) Join Attribute
draft-ietf-pim-mtid-08.txt draft-ietf-pim-mtid-09.txt
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and 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
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 1, line 35 skipping to change at page 1, line 35
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."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on December 10, 2011. This Internet-Draft will expire on February 17, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2011 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
skipping to change at page 2, line 15 skipping to change at page 2, line 15
described in the Simplified BSD License. described in the Simplified BSD License.
Abstract Abstract
This document introduces a new type of PIM Join Attribute that This document introduces a new type of PIM Join Attribute that
extends PIM signaling to identify a topology that should be used when extends PIM signaling to identify a topology that should be used when
constructing a particular multicast distribution tree. constructing a particular multicast distribution tree.
Table of Contents Table of Contents
1 Specification of Requirements ...................... 3 1 Terminologies ...................................... 3
2 Introduction ....................................... 3 2 Introduction ....................................... 3
3 Functional Overview ................................ 4 3 Functional Overview ................................ 4
3.1 PIM RPF Topology ................................... 4 3.1 PIM RPF Topology ................................... 5
3.2 PIM MT-ID .......................................... 5 3.2 PIM MT-ID .......................................... 6
3.3 Applicability ...................................... 6 3.3 Applicability ...................................... 7
4 Protocol Specification of PIM MT-ID ................ 6 4 Protocol Specification of PIM MT-ID ................ 7
4.1 PIM MT-ID Hello Option ............................. 6 4.1 PIM MT-ID Hello Option ............................. 7
4.2 PIM MT-ID Join Attribute ........................... 7 4.2 PIM MT-ID Join Attribute ........................... 8
4.2.1 Sending PIM MT-ID Join Attribute ................... 7 4.2.1 Sending PIM MT-ID Join Attribute ................... 8
4.2.2 Receiving PIM MT-ID Join Attribute ................. 7 4.2.2 Receiving PIM MT-ID Join Attribute ................. 8
4.2.3 Validating PIM MT-ID Join Attribute ................ 8 4.2.3 Validating PIM MT-ID Join Attribute ................ 9
4.2.4 Conflict Resolution ................................ 9 4.2.4 Conflict Resolution ................................ 10
4.2.4.1 Conflict Resolution Rules For Upstream Routers ..... 9 4.2.4.1 Conflict Resolution Rules For Upstream Routers ..... 10
4.2.4.2 Conflict Resolution Rules For Downstream Routers ... 10 4.2.4.2 Conflict Resolution Rules For Downstream Routers ... 11
5 Packet Format ...................................... 10 5 Packet Format ...................................... 11
5.1 PIM MT-ID Hello Option ............................. 10 5.1 PIM MT-ID Hello Option ............................. 11
5.2 PIM MT-ID Join Attribute TLV Format ................ 10 5.2 PIM MT-ID Join Attribute TLV Format ................ 12
6 IANA Considerations ................................ 11 6 IANA Considerations ................................ 12
6.1 PIM ................................................ 11 6.1 PIM MT-ID Hello Option ............................. 12
6.2 PIM ................................................ 11 6.2 PIM MT-ID Join Attribute Type ...................... 13
7 Security Considerations ............................ 12 7 Security Considerations ............................ 13
8 Acknowledgments .................................... 12 8 Acknowledgments .................................... 13
9 Authors' Addresses ................................. 12 9 Authors' Addresses ................................. 13
10 Normative References ............................... 13 10 Normative References ............................... 14
11 Informative References ............................. 13 11 Informative References ............................. 14
1. Specification of Requirements 1. Terminologies
The following acronyms are frequently used in the document.
- RPF: RPF stands for "Reverse Path Forwarding". A PIM router
performs RPF for two purposes. When building a forwarding tree,
a PIM router identifies an interface (the RPF interface) and an
upstream PIM neighbor (the RPF neighbor) to which to send PIM
Joins. Upon receiving a data packet, a PIM router verifies if
the packet arrives from the expected incoming interface (aka RPF
check) before deciding whether or not to replicate the packets.
- RPF Topology: An RPF topology is a collection of routes that a
PIM router uses for RPF. One or more RPF topologies may be
created on a PIM router.
- MT: MT stands for "Multi-Topology" in this document. Sometimes
it is also referred to as multi-topology routing. In the context
of PIM, MT refers to the capability of building and maintaining
multiple RPF topologies.
- PIM MT-ID: An MT-ID is a numerical identifier associated with an
RPF topology.
- PIM MT-ID Join Attribute: This is a new type of Join Attribute
that is introduced by this document in order to specify RPF
topology in the PIM Join messages.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
2. Introduction 2. Introduction
Some unicast protocols, such as OSPF and IS-IS, allow a single Some unicast protocols, such as OSPF and IS-IS, allow a single
network to be viewed as multiple topologies [RFC4915], [RFC5120]. network to be viewed as multiple topologies [RFC4915], [RFC5120].
Deploying multi-topology (MT) routing allows different paths through Deploying multi-topology (MT) routing allows different paths through
the network to be selected to support different traffic, or to offer the network to be selected to support different traffic, or to offer
protection paths in the event of failures. protection paths in the event of failures.
PIM [RFC4601] employs a technique known as Reverse Path Forwarding PIM [RFC4601] employs a technique known as Reverse Path Forwarding
skipping to change at page 4, line 5 skipping to change at page 4, line 33
This document does not introduce any change to the RPF check This document does not introduce any change to the RPF check
procedure used to verify the incoming interface when a packet is procedure used to verify the incoming interface when a packet is
forwarded as defined in [RFC4601]. For example, to use the forwarded as defined in [RFC4601]. For example, to use the
capability described by this document, an application can choose to capability described by this document, an application can choose to
use group addresses, and/or source addresses, to identify a unique use group addresses, and/or source addresses, to identify a unique
multicast stream. It might further need to perform the functions of multicast stream. It might further need to perform the functions of
splitting and merging. But the detailed processing is beyond the splitting and merging. But the detailed processing is beyond the
scope of the document. scope of the document.
In the rest of the document, the MT-ID Join Attribute may be simply In the rest of the document, the MT-ID Join Attribute will be
referred to as "MT-ID". referred to as "MT-ID".
3. Functional Overview 3. Functional Overview
PIM relies on routes learned from routing protocols for the purpose
of RPF. These routes form one or more topologies. This section
describes the function of multi-topology routing for PIM and its
applicability.
3.1. PIM RPF Topology 3.1. PIM RPF Topology
PIM RPF topology is a collection of routes used by PIM to perform RPF PIM RPF topology is a collection of routes used by PIM to perform RPF
operation when building shared or source trees. The routes in the operation when building shared or source trees. The routes in the
topology may be contributed by different protocols. In the rest of topology may be contributed by different protocols. In the rest of
the document, PIM RPF topology may be simply referred to as the document, PIM RPF topology may be simply referred to as
"topology" when there is no ambiguity. "topology" when there is no ambiguity.
In a multi-topology environment, multiple RPF topologies can be In a multi-topology environment, multiple RPF topologies can be
created in the same network. A particular source may be reachable in created in the same network. A particular source may be reachable in
only one of the topologies, or in several of them via different only one of the topologies, or in several of them via different
paths. paths.
To help explain the relationship between MT capable unicast routing To help explain the relationship between MT capable unicast routing
protocol and MT capable RPF topologies, please consider the following protocol and MT capable RPF topologies, consider the following
example. example described by Figure 1.
+++ A +++ B +++ +++ A +++ B +++
+ + + +
S -- R1 R2 -- receivers S -- R1 R2 -- receivers
* * * *
*** C *** D *** *** C *** D ***
Figure 1. A simple topology for multicast
- The traffic source is S. S is announced by R1 using MBGP to - The traffic source is S. S is announced by R1 using MBGP to
every router. This route is installed in every topology. every router. This route is installed in every topology.
- Two topologies are created in the unicast IGP, let us call them - Two topologies are created in the unicast IGP, let us call them
OSPF 1000 and OSPF 2000. OSPF 1000 includes A, B and interfaces OSPF 1000 and OSPF 2000. OSPF 1000 includes A, B and interfaces
in R1 and R2 that are configured to be part of OSPF 1000. OSPF in R1 and R2 that are configured to be part of OSPF 1000. OSPF
2000 includes C, D and interfaces on R1 and R2 that are 2000 includes C, D and interfaces on R1 and R2 that are
configured to be part of OSPF 2000. configured to be part of OSPF 2000.
- Two PIM RPF topologies are created, let us call them PIM 500 and - Two PIM RPF topologies are created, let us call them PIM 500 and
PIM 600. PIM 600.
PIM 500 comprises the following routes: S announced by MBGP and PIM 500 comprises the following routes: S announced by MBGP and
those learned via OSPF 1000. those learned via OSPF 1000.
PIM 600 comprises the following routes: S announced by MBGP and PIM 600 comprises the following routes: S announced by MBGP and
those learned via OSPF 2000 those learned via OSPF 2000
The above example shows that the naming spaces of MT-ID are not The above example illustrates that the naming spaces of MT-ID are not
required to be the same between PIM and IGPs. Furthermore, a unicast required to be the same between PIM and IGPs. Furthermore, a unicast
IGP topology and the PIM RPF topology to which the IGP topology IGP topology and the PIM RPF topology to which the IGP topology
contributes routes are not required to have the same set of routes. contributes routes are not required to have the same set of routes.
In the above example, the prefix covering S does not exist in either In the above example, the prefix covering S does not exist in either
OSPF 1000 or OSPF 2000. But since it exists in PIM 500 and PIM 600, OSPF 1000 or OSPF 2000. But since it exists in PIM 500 and PIM 600,
R2 is able to join to it via either path. R2 is able to join to it via either path.
There are two methods to select the RPF topology for a particular There are two methods to select the RPF topology for a particular
multicast distribution tree, via configuration or via PIM. multicast distribution tree, via configuration or via PIM.
skipping to change at page 6, line 9 skipping to change at page 7, line 7
the MT-ID used by the unicast routing protocols that contribute the MT-ID used by the unicast routing protocols that contribute
routes to the topology. In practice, when only one unicast routes to the topology. In practice, when only one unicast
routing protocol (such as OSPF or IS-IS) is used, the PIM MT-ID routing protocol (such as OSPF or IS-IS) is used, the PIM MT-ID
is RECOMMENDED to be assigned using the same value as the IGP is RECOMMENDED to be assigned using the same value as the IGP
topology identifier. Using the same example presented earlier, if topology identifier. Using the same example presented earlier, if
every route in PIM 500 is contributed by OSPF 1000, it is every route in PIM 500 is contributed by OSPF 1000, it is
RECOMMENDED to name this RPF topology as PIM 1000 instead of PIM RECOMMENDED to name this RPF topology as PIM 1000 instead of PIM
500. This is for the purpose of reducing management overhead and 500. This is for the purpose of reducing management overhead and
simplifying troubleshooting. simplifying troubleshooting.
- This value must be unique and consistent within the network - This value MUST be unique and consistent within the network for
domain for the same topology. For example, PIM 500 MUST refer to the same topology. For example, PIM 500 MUST refer to the same
the same topology on routers R1, C, D and R2. For actual topology on routers R1, C, D and R2. For actual deployment, one
deployment, one should have a means to detect inconsistency of should have a means to detect inconsistency of the PIM MT-ID
the PIM MT-ID configuration, but the detail of such mechanism is configuration, but the detail of such mechanism is beyond the
beyond the scope of this document. scope of this document.
- 0 is reserved as the default, and MUST NOT be included in the - 0 is reserved as the default, and MUST NOT be included in the
Join Attribute encoding. Join Attribute encoding.
- How to assign a PIM MT-ID to a topology is decided by the network - How to assign a PIM MT-ID to a topology is decided by the network
administrator and is outside the scope of this document administrator and is outside the scope of this document
3.3. Applicability 3.3. Applicability
The PIM MT-ID Join Attribute described in this document applies to The PIM MT-ID Join Attribute described in this document applies to
skipping to change at page 8, line 15 skipping to change at page 9, line 15
If the router supports [RFC5384] but not this document, it is able to If the router supports [RFC5384] but not this document, it is able to
skip PIM MT-ID Join Attribute and move on to the next Join Attribute skip PIM MT-ID Join Attribute and move on to the next Join Attribute
if one is present. The RPF decision will not be altered because the if one is present. The RPF decision will not be altered because the
router doesn't understand the meaning of PIM MT-ID Join Attribute. router doesn't understand the meaning of PIM MT-ID Join Attribute.
The router will use the procedures described by [RFC5384] to perform The router will use the procedures described by [RFC5384] to perform
conflict resolution. conflict resolution.
If a router doesn't support [RFC5384], it will ignore the Join/Assert If a router doesn't support [RFC5384], it will ignore the Join/Assert
message because it is not able to parse the encoded sources. message because it is not able to parse the encoded sources.
If a router does support both [RFC5384] and this document, but choose If a router does support both [RFC5384] and this document, but
not to send either PIM MT-ID or PIM Join Attribute Option in its chooses not to send either PIM MT-ID or PIM Join Attribute Option in
Hello packets (likely due to administrative reason), when it receives its Hello packets (likely due to administrative reason), when it
a PIM Join/Assert packets with PIM MT-ID Join Attribute, it SHOULD receives a PIM Join/Assert packets with PIM MT-ID Join Attribute, it
ignore the Join/Assert message. SHOULD ignore the Join/Assert message.
4.2.3. Validating PIM MT-ID Join Attribute 4.2.3. Validating PIM MT-ID Join Attribute
An upstream router MUST be known to support this document in order An upstream router MUST be known to support this document in order
for a downstream router to include the PIM MT-ID attribute in its for a downstream router to include the PIM MT-ID attribute in its
Join packets. But an upstream router doesn't need to know if a Join packets. But an upstream router doesn't need to know if a
downstream router supports this document or not when deciding whether downstream router supports this document or not when deciding whether
to accept the attribute. Hence, if the Join packet sender doesn't to accept the attribute. Hence, if the Join packet sender doesn't
include "PIM Join Attribute" or "PIM MT-ID" options in its Hello include "PIM Join Attribute" or "PIM MT-ID" options in its Hello
packets, the PIM MT-ID attribute in the Join may still be considered packets, the PIM MT-ID attribute in the Join may still be considered
valid. This is also in accordance with the "Robustness Principle" valid. This is also in accordance with the "Robustness Principle"
outlined in [RFC761]. outlined in [RFC761].
The following text specifies the detail of the validity check. The following text specifies the detail of the validity check.
- There is at most 1 PIM MT-ID attribute encoded. If there are - There is at most 1 PIM MT-ID attribute encoded. If there are
multiple PIM MT-ID Join Attributes included, only the last one is multiple PIM MT-ID Join Attributes included (possibly due to an
accepted for this particular source. Processing of the rest of error in the implementation), only the last one is accepted for
the Join message continues. this particular source. Processing of the rest of the Join
message continues.
- The length field must be 2. If the length field is not 2, the - The length field must be 2. If the length field is not 2, the
rest of the Join message, including the current (S,G) or (*,G) rest of the Join message, including the current (S,G) or (*,G)
entry, MUST be ignored. The group, source and the RP in the Join entry, MUST be ignored. The group, source and the RP in the Join
message that have already been processed SHOULD still be message that have already been processed SHOULD still be
considered valid. considered valid.
- The value MUST NOT be 0. If it is 0, the PIM MT-ID attribute is - The value MUST NOT be 0. If it is 0, the PIM MT-ID attribute is
ignored. Processing of the rest of the Join message, including ignored. Processing of the rest of the Join message, including
the current (S,G) or (*,G) entry, continues as if the particular the current (S,G) or (*,G) entry, continues as if the particular
skipping to change at page 9, line 42 skipping to change at page 10, line 42
4.2.4.1. Conflict Resolution Rules For Upstream Routers 4.2.4.1. Conflict Resolution Rules For Upstream Routers
- If an upstream router receives different PIM MT-ID attributes - If an upstream router receives different PIM MT-ID attributes
from PIM Join packets, it MUST follow the rules specified in from PIM Join packets, it MUST follow the rules specified in
[RFC5384] to select one. The PIM MT-ID chosen will be the one [RFC5384] to select one. The PIM MT-ID chosen will be the one
encoded for its upstream neighbor. encoded for its upstream neighbor.
In order to minimize the chances of potential transient In order to minimize the chances of potential transient
forwarding loops, an upstream router MAY choose to ignore the forwarding loops, an upstream router MAY choose to ignore the
incoming PIM Join packets all together if it sees a conflict in incoming PIM Join packets altogether if it sees a conflict in PIM
PIM MT-ID attributes. This action may also be taken by an MT-ID attributes. This action may also be taken by an upstream
upstream router which has locally configured topology selection router which has locally configured topology selection policy, as
policy, as an exception to the rules described above. an exception to the rules described above.
- If an upstream router receives a different PIM MT-ID attribute in - If an upstream router receives a different PIM MT-ID attribute in
an ASSERT packet, it MUST use the tie-breaker rules as specified an ASSERT packet, it MUST use the tie-breaker rules as specified
in [RFC4601] to determine an ASSERT winner. PIM MT-ID is not in [RFC4601] to determine an ASSERT winner. PIM MT-ID is not
considered in deciding a winner from Assert process. considered in deciding a winner from Assert process.
4.2.4.2. Conflict Resolution Rules For Downstream Routers 4.2.4.2. Conflict Resolution Rules For Downstream Routers
- If a downstream router sees different PIM MT-ID attributes from - If a downstream router sees different PIM MT-ID attributes from
PIM Join packets, it MUST follow the specification of [RFC4601] PIM Join packets, it MUST follow the specification of [RFC4601]
skipping to change at page 10, line 25 skipping to change at page 11, line 25
routers. routers.
- If a downstream router sees its preferred upstream router loses - If a downstream router sees its preferred upstream router loses
in the ASSERT process, and the ASSERT winner uses a different PIM in the ASSERT process, and the ASSERT winner uses a different PIM
MT-ID, the downstream router SHOULD still choose the ASSERT MT-ID, the downstream router SHOULD still choose the ASSERT
winner as the RPF neighbour but it MUST NOT encode PIM MT-ID when winner as the RPF neighbour but it MUST NOT encode PIM MT-ID when
sending Join packets to it. sending Join packets to it.
5. Packet Format 5. Packet Format
This section describes the format of new PIM messages introduced by
this document. The messages follow the same transmission order as the
messages defined in [RFC4601].
5.1. PIM MT-ID Hello Option 5.1. PIM MT-ID Hello Option
0 1 2 3 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OptionType = 30 | OptionLength = 0 | | OptionType = 30 | OptionLength = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- OptionType: 30. - OptionType: 30.
skipping to change at page 11, line 13 skipping to change at page 12, line 21
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
- F bit: 0 Non-transitive Attribute. - F bit: 0 Non-transitive Attribute.
- E bit: As specified by [RFC5384]. - E bit: As specified by [RFC5384].
- Attr Type: To be assigned by IANA. - Attr Type: To be assigned by IANA.
- Length: 2. - Length: 2.
- R: Reserved bits, 4 in total. - R: Reserved bits, 4 in total. Set to zero on transmission.
Ignored upon receipt.
- Value: PIM MT-ID, 1 to 4095. - Value: PIM MT-ID, 1 to 4095.
6. IANA Considerations 6. IANA Considerations
6.1. PIM 6.1. PIM MT-ID Hello Option
The IANA maintains a registry of "Protocol Independent Multicast IANA maintains a registry of "Protocol Independent Multicast (PIM)
(PIM) Parameters" with a sub-registry called "PIM-Hello Options" Parameters" with a sub-registry called "PIM-Hello Options"
The IANA assigned the PIM Hello Option type value 30 for the PIM MT- The IANA assigned the PIM Hello Option type value 30 for the PIM MT-
ID Hello Option according to the First Come First Served allocation ID Hello Option according to the First Come First Served allocation
policy. policy.
The IANA is requested to make that allocation permanent with The IANA is requested to make that allocation permanent with
reference to this document. reference to this document.
Note that the option defined in Section 5.1 of this document has Note that the option defined in Section 5.1 of this document has
length 0. The IANA is requested to update the length value recorded length 0. The IANA is requested to update the length value recorded
in the registry. in the registry.
6.2. PIM 6.2. PIM MT-ID Join Attribute Type
The IANA maintains a registry of "Protocol Independent Multicast The IANA maintains a registry of "Protocol Independent Multicast
(PIM) Parameters" with a sub-registry called "PIM Join Attribute (PIM) Parameters" with a sub-registry called "PIM Join Attribute
Types". Types".
The IANA is requested to assign the next available value for the PIM The IANA is requested to assign the next available value for the PIM
MT-ID Join Attribute defined in Section 5.2 of this document. MT-ID Join Attribute defined in Section 5.2 of this document.
7. Security Considerations 7. Security Considerations
 End of changes. 22 change blocks. 
58 lines changed or deleted 98 lines changed or added

This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/