draft-ietf-mpls-bgp-mpls-restart-03.txt   draft-ietf-mpls-bgp-mpls-restart-04.txt 
Network Working Group Yakov Rekhter (Juniper Networks) Network Working Group Yakov Rekhter (Juniper Networks)
Internet Draft Rahul Aggarwal (Juniper Networks) Internet Draft Rahul Aggarwal (Juniper Networks)
Expiration Date: August 2004 Expiration Date: July 2005
Graceful Restart Mechanism for BGP with MPLS Graceful Restart Mechanism for BGP with MPLS
draft-ietf-mpls-bgp-mpls-restart-03.txt draft-ietf-mpls-bgp-mpls-restart-04.txt
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
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Abstract Abstract
A mechanism for BGP that would help minimize the negative effects on A mechanism for BGP that would help minimize the negative effects on
routing caused by BGP restart is described in "Graceful Restart routing caused by BGP restart is described in "Graceful Restart
Mechanism for BGP" (see [1]). This document extends this mechanism to Mechanism for BGP" (see [1]). This document extends this mechanism to
also minimize the negative effects on MPLS forwarding caused by the also minimize the negative effects on MPLS forwarding caused by the
Label Switching Router's (LSR's) control plane restart, and Label Switching Router's (LSR's) control plane restart, and
specifically by the restart of its BGP component when BGP is used to specifically by the restart of its BGP component when BGP is used to
carry MPLS labels and the LSR is capable of preserving the MPLS carry MPLS labels and the LSR is capable of preserving the MPLS
forwarding state across the restart. forwarding state across the restart.
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Label Switching Router's (LSR's) control plane restart, and Label Switching Router's (LSR's) control plane restart, and
specifically by the restart of its BGP component when BGP is used to specifically by the restart of its BGP component when BGP is used to
carry MPLS labels and the LSR is capable of preserving the MPLS carry MPLS labels and the LSR is capable of preserving the MPLS
forwarding state across the restart. forwarding state across the restart.
The mechanism described in this document is agnostic with respect to The mechanism described in this document is agnostic with respect to
the types of the addresses carried in the BGP Network Layer the types of the addresses carried in the BGP Network Layer
Reachability Information (NLRI) field. As such it works in Reachability Information (NLRI) field. As such it works in
conjunction with any of the address famililies that could be carried conjunction with any of the address famililies that could be carried
in BGP (e.g., IPv4, IPv6, etc...) in BGP (e.g., IPv4, IPv6, etc...)
The mechanism described in this document is applicable to all LSRs, The mechanism described in this document is applicable to all LSRs,
both those with the ability to preserve their forwarding state during both those with the ability to preserve their forwarding state during
BGP restart and those without (although the latter need to implement BGP restart and those without (although the latter need to implement
only a subset of the mechanism described in this document). only a subset of the mechanism described in this document).
Supporting (a subset of) the mechanism described here by the LSRs Supporting a subset of the mechanism described here by the LSRs that
that can not preserve their MPLS forwarding state across the restart can not preserve their MPLS forwarding state across the restart would
would not reduce the negative impact on MPLS traffic caused by their not reduce the negative impact on MPLS traffic caused by their
control plane restart, but it would minimize the impact if their control plane restart, but it would minimize the impact if their
neighbor(s) are capable of preserving the forwarding state across the neighbor(s) are capable of preserving the forwarding state across the
restart of their control plane and implement the mechanism described restart of their control plane and implement the mechanism described
here. here.
The mechanism makes minimalistic assumptions on what has to be
preserved across restart - the mechanism assumes that only the actual
MPLS forwarding state has to be preserved; the mechanism does not
require any of the BGP-related state to be preserved across the
restart.
Specification of Requirements Specification of Requirements
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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Summary for Sub-IP Area
(This section to be removed before publication.)
0.1 Summary
This document describes a mechanism that helps to minimize the
negative effects on MPLS forwarding caused by LSR's control plane
restart, and specifically by the restart of its BGP component in the
case where BGP is used to carry MPLS labels and LSR is capable of
preserving its MPLS forwarding state across the restart.
0.2 Related documents
See the Reference Section
0.3 Where does it fit in the Picture of the Sub-IP Work
This work fits squarely in MPLS box.
0.4 Why is it Targeted at this WG
The specifications on carrying MPLS Labels in BGP is a product of the
MPLS WG. This document specifies procedures to minimize the negative
effects on MPLS forwarding caused by the restart of the control plane
BGP module in the case where BGP is used to carry MPLS labels. Since
the procedures described in this document are directly related to
MPLS forwarding and carrying MPLS labels in BGP, it would be logical
to target this document at the MPLS WG.
0.5 Justification
The WG should consider this document, as it allows to minimize the
negative effects on MPLS forwarding caused by the restart of the
control plane BGP module in the case where BGP is used to carry MPLS
labels.
1. Motivation 1. Motivation
For the sake of brevity in the context of this document by "MPLS For the sake of brevity in the context of this document by "MPLS
forwarding state" we mean either <incoming label -> (outgoing label, forwarding state" we mean either <incoming label -> (outgoing label,
next hop)>, or <address prefix -> (outgoing label, next hop)> next hop)>, or <Forwarding Equivalence Class (FEC) -> (outgoing
mapping. In the context of this document the forwarding state that is label, next hop)>, or <incoming label -> label pop, next hop>, or
referred to in [1] means MPLS forwarding state. <incoming label, label pop> mapping. In the context of this document
the forwarding state that is referred to in [1] means MPLS forwarding
state, as defined above. In the context of this document the term
"next hop" refers to the next hop as advertised in BGP.
In the case where a Label Switching Router (LSR) could preserve its In the case where a Label Switching Router (LSR) could preserve its
MPLS forwarding state across restart of its control plane, and MPLS forwarding state across restart of its control plane, and
specifically its BGP component, and BGP is used to carry MPLS labels specifically its BGP component, and BGP is used to carry MPLS labels
(as specified in [2]), it may be desirable not to perturb the LSPs (e.g., as specified in [RFC3107]), it may be desirable not to perturb
going through that LSR (and specifically, the LSPs established by the LSPs going through that LSR (and specifically, the LSPs
BGP). In this document, we describe a mechanism that allows to established by BGP). In this document, we describe a mechanism that
accomplish this goal. The mechanism described in this document works allows to accomplish this goal. The mechanism described in this
in conjunction with the mechanism specified in [1]. The mechanism document works in conjunction with the mechanism specified in [1].
described in this document places no restrictions on the types of The mechanism described in this document places no restrictions on
addresses (address families) that it can support. the types of addresses (address families) that it can support.
The mechanism described in this document is applicable to all LSRs, The mechanism described in this document is applicable to all LSRs,
both those with the ability to preserve forwarding state during BGP both those with the ability to preserve forwarding state during BGP
restart and those without (although the latter need to implement only restart and those without (although the latter need to implement only
a subset of the mechanism described in this document). Supporting (a a subset of the mechanism described in this document). Supporting a
subset of) the mechanism described here by the LSRs that can not subset of the mechanism described here by the LSRs that can not
preserve their MPLS forwarding state across the restart would not preserve their MPLS forwarding state across the restart would not
reduce the negative impact on MPLS traffic caused by their control reduce the negative impact on MPLS traffic caused by their control
plane restart, but it would minimize the impact if their neighbor(s) plane restart, but it would minimize the impact if their neighbor(s)
are capable of preserving the forwarding state across the restart of are capable of preserving the forwarding state across the restart of
their control plane and implement the mechanism described here. their control plane and implement the mechanism described here. The
subset includes all the procedures described in this document, except
2. Assumptions the procedures in Sections 4.1, 4.2, 4.3, 5, and 6.
First of all we assume that an LSR implements the Graceful Restart 2. General requirements
Mechanism for BGP, as specified in [1]. Second, we assume that the
LSR is capable of preserving its MPLS forwarding state across the
restart of its control plane (including the restart of BGP).
The mechanism makes minimalistic assumptions on what has to be First of all an LSR MUST implement the Graceful Restart Mechanism for
preserved across restart - the mechanism assumes that only the actual BGP, as specified in [1]. Second, the LSR SHOULD be capable of
MPLS forwarding state has to be preserved; the mechanism does not preserving its MPLS forwarding state across the restart of its
require any of the BGP-related state to be preserved across the control plane (including the restart of BGP). Third, for the
restart. <Forwarding Equivalence Class (FEC) -> label> bindings distributed
via BGP the LSR SHOULD be able either (a) to reconstruct the same
bindings as the LSR had prior to the restart (see Section 4), or (b)
to create new <FEC -> label> bindings after restart, while temporary
maintaining MPLS forwarding state corresponds to both the bindings
prior to the restart, as well as to the newly created bindings (see
Section 5). Fourth, as long as the LSR retains the MPLS forwarding
state that the LSR preserved across the restart, the labels from that
state can not be used to create new local label bindings (but could
be used to reconstruct the existing bindings, as per procedures in
Section 4). Finally, for each next hop, if the next hop is reachable
via a Label Switched Path (LSP), then the restarting LSR MUST be able
to preserve the MPLS forwarding state associated with that LSP across
the restart.
In the scenario where label binding on an LSR is created/maintained In the scenario where label binding on an LSR is created/maintained
not just by the BGP component of the control plane, but by other not just by the BGP component of the control plane, but by other
protocol components as well (e.g., LDP, RSVP-TE), and the LSR protocol components as well (e.g., LDP, RSVP-TE), and the LSR
supports restart of the individual components of the control plane supports restart of the individual components of the control plane
that create/maintain label binding (e.g., restart of BGP, but no that create/maintain label binding (e.g., restart of BGP, but no
restart of LDP) the LSR needs to preserve across the restart the restart of LDP) the LSR MUST be able to preserve across the restart
information about which protocol has assigned which labels. the information about which protocol has assigned which labels.
After the LSR restarts, it MUST follow the procedures as specified in
[1]. In addition, if the LSR is able to preserve its MPLS forwarding
state across the restart, the LSR SHOULD advertise this to its
neighbors by appropriately setting the Flag for Address Family field
in the Graceful Restart Capability for all applicable AFI/SAFI pairs.
3. Capability Advertisement 3. Capability Advertisement
An LSR that supports the mechanism described in this document An LSR that supports the mechanism described in this document
advertises this to its peer by using the Graceful Restart Capability, advertises this to its peer by using the Graceful Restart Capability,
as specified in [1]. The Subsequent Address Family Identifier (SAFI) as specified in [1]. The Subsequent Address Family Identifier (SAFI)
in the advertised capability MUST indicate that the Network Layer in the advertised capability MUST indicate that the Network Layer
Reachability Information (NLRI) field carries not just addressing Reachability Information (NLRI) field carries not just addressing
information but labels as well (see [2]). Information, but labels as well (see [RFC3107] as an example of where
NLRI carries labels).
4. Procedures for the restarting LSR 4. Procedures for the restarting LSR
After the LSR restarts, it follows the procedures as specified in Procedures in this section applies when a restarting LSR is able to
[1]. In addition, if the LSR is able to preserve its MPLS forwarding reconstruct the same <FEC -> label> bindings as the LSR had prior to
state across the restart, the LSR advertises this to its neighbors by the restart.
appropriately setting the Flag field in the Graceful Restart
Capability for all applicable AFI/SAFI pairs.
Once the restarting LSR completes its route selection (as specified The procedures described in this section are conceptual and do not
in Section "Procedures for the Restarting Speaker" of [1]), then in have to be implemented precisely as described here, as long as the
addition to the procedures specified in [1], the restarting LSR implementations support the described functionality and their
performs one of the following: externally visible behavior is the same.
Once the LSR completes its route selection (as specified in Section
"Procedures for the Restarting Speaker" of [1]), then in addition to
the procedures specified in [1], the LSR performs one of the
following:
4.1. Case 1 4.1. Case 1
The following applies when (a) the best route selected by the The following applies when (a) the best route selected by the LSR was
restarting LSR was received with a label, (b) that label is not an received with a label, (b) that label is not an Implicit NULL, and
Implicit NULL, and (c) the LSR advertises this route with itself as (c) the LSR advertises this route with itself as the next hop.
the next hop.
In this case the restarting LSR searches its MPLS forwarding state In this case the LSR searches its MPLS forwarding state (the one
(the one preserved across the restart) for an entry with <outgoing preserved across the restart) for an entry with <outgoing label, next
label, Next-Hop> equal to the one in the received route. If such an hop> equal to the one in the received route. If such an entry is
entry is found, the LSR no longer marks the entry as stale. In found, the LSR no longer marks the entry as stale. In addition if the
addition if the entry is of type <incoming label, (outgoing label, entry is of type <incoming label, (outgoing label, next hop)> rather
next hop)> rather than <prefix, (outgoing label, next hop)>, the LSR than <Forwarding Equivalence Class (FEC), (outgoing label, next
uses the incoming label from the entry when advertising the route to hop)>, the LSR uses the incoming label from the entry when
its neighbors. If the found entry has no incoming label, or if no advertising the route to its neighbors. If the found entry has no
such entry is found, the LSR just picks up some unused label when incoming label, or if no such entry is found, the LSR allocates a new
advertising the route to its neighbors (assuming that there are label when advertising the route to its neighbors (assuming that
neighbors to which the LSR has to advertise the route with a label). there are neighbors to which the LSR has to advertise the route with
a label).
4.2. Case 2 4.2. Case 2
The following applies when (a) the best route selected by the The following applies when (a) the best route selected by the LSR was
restarting LSR was received either without a label, or with an received either without a label, or with an Implicit NULL label, or
Implicit NULL label, or the route is originated by the restarting the route is originated by the LSR, (b) the LSR advertises this route
LSR, (b) the LSR advertises this route with itself as the next hop, with itself as the next hop, and (c) the LSR has to generate a (non
and (c) the LSR has to generate a (non Implicit NULL) label for the Implicit NULL) label for the route.
route.
In this case the LSR searches its MPLS forwarding state for an entry In this case the LSR searches its MPLS forwarding state for an entry
that indicates that the LSR has to perform label pop, and the next that indicates that the LSR has to perform label pop, and the next
hop equal to the next hop of the route in consideration. If such an hop equal to the next hop of the route in consideration. If such an
entry is found, then the LSR uses the incoming label from the entry entry is found, then the LSR uses the incoming label from the entry
when advertising the route to its neighbors. If no such entry is when advertising the route to its neighbors. If no such entry is
found, the LSR just picks up some unused label when advertising the found, the LSR allocates a new label when advertising the route to
route to its neighbors. its neighbors.
The description in the above paragraph assumes that the restarting The description in the above paragraph assumes that the LSR generates
LSR generates the same label for all the routes with the same next the same label for all the routes with the same next hop. If this is
hop. If this is not the case, and the restarting LSR generates a not the case, and the LSR generates a unique label per each such
unique label per each such route, then the LSR needs to preserve route, then the LSR needs to preserve across the restart not just
across the restart not just <incoming label, (outgoing label, next <incoming label, (outgoing label, next hop)> mapping, but also the
hop)> mapping, but also the prefix associated with this mapping. In Forwarding Equivalence Class (FEC) associated with this mapping. In
such case the LSR would search its MPLS forwarding state for an entry such case the LSR would search its MPLS forwarding state for an entry
that (a) indicates Label pop (means no outgoing label), (b) the next that (a) indicates Label pop (means no outgoing label), (b) the next
hop equal to the next hop of the route and (c) has the same prefix as hop equal to the next hop of the route and (c) has the same FEC as
the route. If such an entry is found, then the LSR uses the incoming the route. If such an entry is found, then the LSR uses the incoming
label from the entry when advertising the route to its neighbors. If label from the entry when advertising the route to its neighbors. If
no such entry is found, the LSR just picks up some unused label when no such entry is found, the LSR allocates a new label when
advertising the route to its neighbors. advertising the route to its neighbors.
4.3. Case 3 4.3. Case 3
The following applies when the restarting LSR does not set BGP Next The following applies when the LSR does not set BGP next hop to self.
Hop to self.
In this case the restarting LSR, when advertising its best route for In this case the LSR, when advertising its best route for a
a particular NLRI just uses the label that was received with that particular NLRI just uses the label that was received with that
route. And if the route was received with no label, the LSR route. And if the route was received with no label, the LSR
advertises the route with no label as well. advertises the route with no label as well. Either way, the LSR does
not allocate label for that route.
5. Alternative procedures for the restarting LSR 5. Alternative procedures for the restarting LSR
In this section we describe an alternative to the procedures In this section we describe an alternative to the procedures
described in Section "Procedures for the restarting LSR". described in Section "Procedures for the restarting LSR".
The procedures described in this section assume that the restarting Procedures in this section apply when a restarting LSR does not
LSR has (at least) as many unallocated as allocated labels. The reconstruct the same <FEC -> label> bindings as the LSR had prior to
latter forms the MPLS forwarding state that the LSR managed to the restart, but instead creates new <FEC -> label> bindings after
preserve across the restart. The former is used for allocating labels restart, while temporary maintaining MPLS forwarding state
after the restart. corresponding to both the bindings prior to the restart, as well as
to the newly created bindings.
After the LSR restarts, it follows the procedures as specified in The procedures described in this section requires that for the use by
[1]. In addition, if the LSR is able to preserve its MPLS forwarding BGP graceful restart the LSR SHOULD have (at least) as many
state across the restart, the LSR advertises this to its neighbors by unallocated labels as labels allocated for the <FEC -> label>
appropriately setting the Flag field in the Graceful Restart bindings distributed by BGP. The latter forms the MPLS forwarding
Capability. state that the LSR managed to preserve across the restart. The former
is used for allocating labels after the restart.
To create local label bindings the LSR uses unallocated labels (this To create (new) local label bindings after the restart the LSR uses
is pretty much the normal procedure). That means that as long as the unallocated labels (this is pretty much the normal procedure).
LSR retains the MPLS forwarding state that the LSR preserved across
the restart, the labels from that state are not used for creating
local label bindings.
The restarting LSR SHOULD retain the MPLS forwarding state that the The LSR SHOULD retain the MPLS forwarding state that the LSR
LSR preserved across the restart at least until the LSR sends End-of- preserved across the restart at least until the LSR sends End-of-RIB
RIB marker to all of its neighbors (by that time the LSR already marker to all of its neighbors (by that time the LSR already
completed its route selection process, and also advertised its Adj- completed its route selection process, and also advertised its Adj-
RIB-Out to its neighbors). The restarting LSR MAY retain the RIB-Out to its neighbors). The LSR MAY retain the forwarding state
forwarding state even a bit longer, as to allow the neighbors to even a bit longer (the amount of extra time MAY be controlled by
receive and process the routes that have been advertised by the configuration on the LSR), as to allow the neighbors to receive and
restarting LSR. After that, the restarting LSR MAY delete the MPLS process the routes that have been advertised by the LSR. After that,
forwarding state that it preserved across the restart. the LSR MAY delete the MPLS forwarding state that it preserved across
the restart.
Note that while an LSR is in the process of restarting, the LSR may Note that while an LSR is in the process of restarting, the LSR may
have not one, but two local label bindings for a given BGP route - have not one, but two local label bindings for a given BGP route -
one that was retained from prior to restart, and another that was one that was retained from prior to restart, and another that was
created after the restart. Once the LSR completes its restart, the created after the restart. Once the LSR completes its restart, the
former will be deleted. Both of these bindings though would have the former will be deleted. Both of these bindings though would have the
same outgoing label (and the same next hop). same outgoing label (and the same next hop).
6. Procedures for a neighbor of a restarting LSR 6. Procedures for a neighbor of a restarting LSR
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then this may result in using a different label value, as when the then this may result in using a different label value, as when the
route re-appears, the LSR would create a new <label, FEC> binding. route re-appears, the LSR would create a new <label, FEC> binding.
To minimize the potential mis-routing caused by the label change, To minimize the potential mis-routing caused by the label change,
when creating a new <label, FEC> binding the LSR SHOULD pick up the when creating a new <label, FEC> binding the LSR SHOULD pick up the
least recently used label. Once an LSR releases a label, the LSR least recently used label. Once an LSR releases a label, the LSR
SHALL NOT re-use this label for advertising a <label, FEC> binding to SHALL NOT re-use this label for advertising a <label, FEC> binding to
a neighbor that supports graceful restart for at least the Restart a neighbor that supports graceful restart for at least the Restart
Time, as advertised by the neighbor to the LSR. Time, as advertised by the neighbor to the LSR.
7. Security Consideration 7. Comparison between alternative procedures for the restarting LSR
Procedures described in Section 4 involve more computational overhead
on the restarting router relative to the procedures described in
Section 5.
Procedures described in Section 5 requires twice as many labels as
the procedures described in Section 4.
Procedures described in Section 4 cause fewer changes to the MPLS
forwarding state in the neighbors of the restarting router than the
procedures described in Section 5.
In principle it is possible for an LSR to use procedures described in
Section 4 for some AFI/SAFI(s) and procedures described in Section 5
for other AFI/SAFI(s).
8. Security Consideration
The security considerations pertaining to the original BGP protocol The security considerations pertaining to the original BGP protocol
remain relevant. remain relevant.
In addition, the mechanism described here renders LSRs that implement In addition, the mechanism described here renders LSRs that implement
it to additional denial-of-service attacks as follows: it to additional denial-of-service attacks as follows:
An intruder may impersonate a BGP peer in order to force a failure An intruder may impersonate a BGP peer in order to force a failure
and reconnection of the TCP connection, but where the intruder and reconnection of the TCP connection, but where the intruder
sets the Forwarding State (F) bit (as defined in [1]) to 0 on sets the Forwarding State (F) bit (as defined in [1]) to 0 on
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considered to have failed and the same security issue applies as considered to have failed and the same security issue applies as
described above. described above.
However, the downstream LSR may declare the session as failed before However, the downstream LSR may declare the session as failed before
the expiration of its Restart Time. This increases the period during the expiration of its Restart Time. This increases the period during
which the downstream LSR might reallocate the label while the which the downstream LSR might reallocate the label while the
upstream LSR continues to transmit data using the old usage of the upstream LSR continues to transmit data using the old usage of the
label. To reduce this issue, this document requires that labels are label. To reduce this issue, this document requires that labels are
not re-used until for at least the Restart Time. not re-used until for at least the Restart Time.
8. Intellectual Property Considerations 9. Intellectual Property Considerations
This section is taken from Section 10.4 of [RFC2026]. This section is taken from Section 10.4 of [RFC2026].
The IETF takes no position regarding the validity or scope of any The IETF takes no position regarding the validity or scope of any
intellectual property or other rights that might be claimed to intellectual property or other rights that might be claimed to
pertain to the implementation or use of the technology described in pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights this document or the extent to which any license under such rights
might or might not be available; neither does it represent that it might or might not be available; neither does it represent that it
has made any effort to identify any such rights. Information on the has made any effort to identify any such rights. Information on the
IETF's procedures with respect to rights in standards-track and IETF's procedures with respect to rights in standards-track and
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copyrights, patents or patent applications, or other proprietary copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice rights which may cover technology that may be required to practice
this standard. Please address the information to the IETF Executive this standard. Please address the information to the IETF Executive
Director. Director.
The IETF has been notified of intellectual property rights claimed in The IETF has been notified of intellectual property rights claimed in
regard to some or all of the specification contained in this regard to some or all of the specification contained in this
document. For more information consult the online list of claimed document. For more information consult the online list of claimed
rights. rights.
9. Copyright Notice Juniper Networks, Inc. is seeking patent protection on some or all of
the technology described in this Internet-Draft. If technology in
this document is adopted as a standard, Juniper Networks agrees to
license, on reasonable and non-discriminatory terms, any patent
rights it obtains covering such technology to the extent necessary to
comply with the standard.
Redback Networks, Inc. is seeking patent protection on some of the
technology described in this Internet-Draft. If technology in this
document is adopted as a standard, Redback Networks agrees to
license, on reasonable and non-discriminatory terms, any patent
rights it obtains covering such technology to the extent necessary to
comply with the standard.
10. Copyright Notice
Copyright (C) The Internet Society (date). All Rights Reserved. Copyright (C) The Internet Society (date). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implmentation may be prepared, copied, published and or assist in its implmentation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind, distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
skipping to change at page 10, line 19 skipping to change at page 11, line 33
The limited permissions granted above are perpetual and will not be The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns. revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
10. Acknowledgments 11. Acknowledgments
We would like to thank Chaitanya Kodeboyina and Loa Andersson for We would like to thank Chaitanya Kodeboyina and Loa Andersson for
their review and comments. The approach described in Section their review and comments. The approach described in Section
"Alternative procedures for the restarting LSR" is based on the idea "Alternative procedures for the restarting LSR" is based on the idea
suggested by Manoj Leelanivas. suggested by Manoj Leelanivas.
11. Normative References 12. Normative References
[1] "Graceful Restart Mechanism for BGP", draft-ietf-idr- [1] "Graceful Restart Mechanism for BGP", draft-ietf-idr-
restart-01.txt restart-01.txt
[2] Rekhter, Y., Rosen, E., "Carrying Label Information in BGP-4",
RFC3107
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119 Requirement Levels", BCP 14, RFC 2119
[RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5 [RFC2385] Heffernan, A., "Protection of BGP Sessions via the TCP MD5
Signature Option", RFC2385 Signature Option", RFC2385
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision [RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", RFC2026 3", RFC2026
12. Author Information 13. Non-normative References
[RFC3107] Rekhter, Y., Rosen, E., "Carrying Label Information in
BGP-4", RFC3107
14. Author Information
Yakov Rekhter Yakov Rekhter
Juniper Networks Juniper Networks
1194 N.Mathilda Ave 1194 N.Mathilda Ave
Sunnyvale, CA 94089 Sunnyvale, CA 94089
e-mail: yakov@juniper.net e-mail: yakov@juniper.net
Rahul Aggarwal Rahul Aggarwal
Juniper Networks Juniper Networks
1194 N.Mathilda Ave 1194 N.Mathilda Ave
 End of changes. 

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