Network Working Group I. Hokelek
Internet-Draft M. Fecko
Expires: February 2, 2008 P. Gurung
S. Samtani
Applied Research
Telcordia Technologies, Inc.
July 2, 2007
Loop-Free IP Fast Reroute Using Local and Remote LFAPs
draft-hokelek-rlfap-00.txt
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Abstract
This draft describes a new loop-free IP fast reroute mechanism which
enhances the IP Fast-ReRoute (IPFRR) [1,15] by introducing the
concept of pre-computed remote Loop-Free Alternate Paths (rLFAPs) on
top of the IPFRR local LFAP. In rLFAP, a router which is adjacent to
the failed resource switches over to pre-computed LFAPs, if they
exist, immediately after failure detection. Multi-hop neighbors
(MNBs) are notified about this remote failure as quickly as possible
using fast failure notification mechanism. Upon receipt of failure
information, MNBs activate their pre-computed remote LFAPs that they
maintain for protecting against remote failures within their
multi-hop neighborhoods. In the worst case, where IPFRR results in
forming micro-loops, rLFAP completely prevents micro-loops for
single link failures and quickly converges to a loop-free path in
case of multiple link failures.
1. Introduction
Fast reroute in communication networks is defined as the dynamic and
timely redirection of a primary path to an alternate secondary path
in response to degradation/failure of the primary path. IP Fast-
ReRoute (IPFRR) drafts [1,15] provide a framework for the fast-
reroute mechanism which minimizes the adverse effects of link or
node failures by timely invoking the pre-computed repair paths.
IPFRR performs well when a router which is adjacent to the failed
resource (link or router) has Loop-Free Alternate Paths (LFAPs).
However, major issues arise either when there is no local LFAP or
the router assumes that the alternate path is loop-free but this
might not be true if there are inconsistencies in the routers' FIBs
(e.g., due to failure propagation and FIB update delays). In the
latter case, a micro-loop might be formed when the primary path is
replaced with the alternate path.
A relative performance of a fast-reroute mechanism should not be
worse than the performance with relying on the routing protocol's
(e.g., OSPF or IS-IS) standard repair mechanism. The performance
metrics include repair delay, additional overhead, ability to handle
micro-loops, backward compatibility, complexity (processing and
memory), and the repair path coverage and quality. An ideal but
non-realistic fast-reroute mechanism would have zero repair delay,
create no extra overhead, either be micro-loop free or handle all
micro-loops, be backward compatible, require minimum amount of
processing power and memory, and cover all failure scenarios.
Fast reroute can be severely impaired by micro-loops which represent
the worst case scenario for IPFRR. Ref. [2] summarizes the
techniques proposed for minimizing the adverse effects of micro-
loops. These techniques either can resolve the micro-loops only
partially [3], or can suffer high delays [4, "incremental cost
advertisement"], or are highly complex [5,6]. Therefore, a fast
reroute mechanism that is micro-loop free and has comparable
performance results to IPFRR in terms of the above metrics will
significantly help IETF to reach its goal of dynamic and timely
rerouting.
This document describes a new micro-loop free fast reroute mechanism
which enhances IPFRR [1,15] by introducing the concept of pre-
computed remote LFAPs (rLFAPs) on top of the IPFRR local LFAP. This
mechanism achieves complete and fast micro-loop prevention at the
minimal amount of extra complexity. In rLFAP, a router that is
adjacent to the failed resource immediately switches over pre-
computed LFAPs if LFAPs for protecting against this local failure
exist (the same as IPFRR) and instantly propagates failure
information to multi-hop neighbors (MNBs) (e.g., X-hop neighbors,
where X is an integer number representing how many hops away from
the failure). Upon receipt of failure information, MNBs activate
their pre-computed LFAPs that they maintain for protecting against
remote failures within their MNBs. Note that this draft uses the
existing well-defined LFAP criteria in [15] but extends its
applicability by calculating remote LFAPs to protect against remote
failures.
2. Overview of rLFAP
The number of LFAP choices to bypass a failed resource is either
equal or higher at routers which are multi-hop away from the failed
component compared to the router adjacent to the failure (the latter
is the subset of the first). This fact together with the concept of
remote LFAP, which protects against failures at multi-hop routers,
is the key motivation behind rLFAP.
One might think that rLFAP would not be fast enough since there is a
certain failure notification delay before activating remote LFAPs.
However, in rLFAP, each router pre-computes two sets of LFAPs: the
first set includes local LFAPs which are activated instantly (if
exist) when a local failure is detected and the second set includes
remote LFAPs which are activated when notifications of remote
failures arrive from multi-hop routers. Therefore, rLFAP follows the
approach proposed in the IPFRR draft [1] for its local best-effort
fast reroute and quickly continues to correct the previous best
effort decisions as failure notifications keep on arriving from
MNBs. Since rLFAP gradually corrects the previous decisions, micro
loops are detected and corrected before or shortly after they are
formed (rLFAP completely prevents micro-loops for single link
failures and quickly converges to a loop-free path in case of
multiple link failures).
The main features of rLFAP are as follows:
- Prevention of micro-loops without tunneling
- Handling multiple link/node failures
- Faster than IPFRR in the worst case scenarios; comparable
otherwise
- Ability to distinguish link and node failures
- Scalability due to limiting the scope of MNBs to X hops
- Minimal additional overhead for fast failure notification
2.1 Micro-loop Prevention Using Remote LFAPs
S----------------A------------------B
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E-----------------------------------D
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F-----------G-----------H-----------J
Figure 1: Micro-loop prevention with rLFAP (link E-D fails)
An example link failure scenario is shown in Figure 1, where link
metrics are unity (i.e., hop-count). The primary path from S to D is
S-E-D before link E-D fails. After E detects the failure, IPFRR
switches instantly over the shortest alternate path E-S-A-B-D.
In this case, a micro-loop is formed between S and E and will cause
network disruption until a new primary path S-A-B-D converges if
none of the techniques in Ref. [2] is employed. However, rLFAP
immediately starts using LFAP S-A-B-D when S is notified about the
failure of link E-D. Note that LFAP S-A-B-D is pre-computed at S to
protect against the failure of link E-D (this is a remote link
failure from router S point of view and the path S-A-B-D is a remote
LFAP from link E-D point of view).
2.2 Handling Multiple Simultaneous Failures
S-----------A-----------B-----------C
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| |
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E-----------------------F-----------D
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| |
| |
| |
G-----------------------H
Figure 2: A simple topology with unit link costs demonstrating
rLFAP's capability for handling multiple simultaneous failures
(links E-F and H-F fail at the same time)
Figure 2 shows a scenario where two link failures (links E-F and H-
F) occur. Using IPFRR, E switches over the shortest alternate
path E-G-H-F-D as soon as it detects the failure of link E-F.
However, after the switchover, H sends all packets coming from the
source E back to G since link H-F also failed. The micro-loop
between E and H should be resolved. After resolving the micro-loop
between E and H, another micro-loop between E and S should also be
resolved to enable successful reroute. If S is notified about these
two link failures, then the best LFAP S-A-B-C-D can be utilized
quickly (X=3 is needed in this scenario). The number of LFAPs needed
for the multiple link failures will not be scalable if they are
required to be pre-computed by each router for any combination of
failures within the entire network. However, rLFAP only needs to
protect failures within its MNBs (explained in Section 3.1);
therefore rLFAP significantly enhances the IPFRR scalability in
resolving micro-loops in case of multiple failures (e.g., compared
to the NOT-VIA mechanism [6]).
2.3 Distinguishing Link and Node Failures
A------------B-------------C
| | |
| | |
| | |
| | |
S------------E-------------D
\ /
\ /
\ /
\ /
\ /
\ /
F
Figure 3: rLFAP's ability to distinguish link and node failures
(either link S-E or router E fail)
Another important rLFAP feature is the ability to distinguish
between link and node failures. Figure 3 shows an example topology
with unit link costs for demonstrating the rLFAP's ability to
distinguish link and node failures. The primary path from S to D is
S-E-D before any failure. Initially, a router assumes that it is a
link failure whenever its communication to a neighboring node is
disrupted (e.g., S detects that it can't reach node E through link
S-E). In this case, the pre-computed LFAP S-F-E-D will be activated
immediately without waiting for distinguishing whether it is a link
or node failure. However, if it is a router failure (e.g., node E
fails), the failure notification concept of rLFAP makes it possible
for routers to receive the failure notification from other
interfaces of the failed router (e.g., node S receives failure
notifications of links B-E and F-E using 2-hop (i.e., X=2) failure
notification mechanism). Upon detection of router's failure, the
pre-computed LFAP S-A-B-C-D is activated. Hence, in rLFAP, routers
can distinguish between link and node failures. The significance of
this feature is supported by the recent work by Gjoka et. al. [7],
which shows that the failure coverage of the fast reroute mechanisms
is different for link and node failure cases.
3. Design Details
rLFAP achieves loop-free convergence by introducing two additional
mechanisms on top of IPFRR: multi-hop failure notification and remote
alternate paths (remote LFAPs or SAPs) for protecting against
failures at multi-hop routers. Apart from these mechanisms, rLFAP
implements all its functionalities using the IPFRR framework [1]. In
this section, we first describe multi-hop neighborhoods (MNBHs) which
limit the number of the required remote LFAPs/SAPs for
scalability. And then, two fast failure notification mechanisms and
LFAP calculations for local and remote failures within MNBH are
presented. It is crucial for all fast reroute mechanisms that the
underlying dynamic routing protocol should converge back to its
optimum routes without causing micro-loops once the topology change
is disseminated to all routers in the network. rLFAP provides a fast
re-convergence from LFAPs to the optimum new routes by utilizing
new routes shortly after they are calculated.
3.1 Multi-hop Neighborhood (MNBH)
N11----N12----N13----N14----N15----N16----N17
| | | | | | |
| | | | | | |
N21----N22----N23----N24----N25----N26----N27
| | | | | | |
| | | | | | |
N31----N32----N33----N34----N35----N36----N37
| | | | | | |
| | | | | | |
N41----N42----N43----N44----N45----N46----N47
| | | | | | |
| | | | | | |
N51----N52----N53----N54----N55----N56----N57
| | | | | | |
| | | | | | |
N61----N62----N63----N64----N65----N66----N67
| | | | | | |
| | | | | | |
N71----N72----N73----N74----N75----N76----N77
Figure 4: An example network
Figure 4 shows an example network consists of 49 nodes. A node on
the boundary has two neighbors if it is located on one of four
corner positions (e.g., N11); otherwise three neighbors (e.g., N12).
A non-boundary node has four neighbors (e.g., N22) irrespective of
its location. The issue is to decide the structure of two adjacent
MNBHs: overlapping or non-overlapping. Inconsistencies or micro-
loops may arise on boundaries of adjacent MNBHs if they are
non-overlapping since each MNBH has only a partial view of the
global topology (e.g., failures close to the boundary of adjacent
MNBHs). Also, an additional mechanism is needed to explicitly
maintain the boundaries if multi-hop NHs are non-overlapping.
Therefore, rLFAP uses overlapping MNBHs.
|
|
----N24----
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----N33----N34----N35----
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| | | | |
----N42----N43----N44----N45----N46----
| | | | |
| | | | |
----N53----N54----N55----
| | |
| | |
----N64----
|
|
Figure 5: 2-hop MNBH for N44
The MNBH for each node only defines a local scope within which to
propagate failure notifications. For example, 2-hop (i.e., X-hop
where X=2) MNBH of N11 consists of nodes together with their all
links which are at most 2-hop away from N11. These nodes include N12,
N13, N21, N22, and N31; and hence, there are 5 nodes and 11 links
within 2-hop MNBH of N11. However, N44's 2-hop MNBH includes 12 nodes
and 36 links as shown in Figure 5. N44 has to calculate separate
LFAPs/SAPs for each destination in the network to protect against
link/node failures within its MNBH. Since MNBHs are overlapping and
define only a local scope for each node, no additional mechanism is
needed to explicitly maintain the MNBHs in the network (e.g., a
simple flooding mechanism similar to OSPF LSAs but limited to X-hop
away routers is sufficient for maintaining MNBHs). Each node takes
its best fast reroute action independently in case of a failure
within its MNBH. Minimal inconsistencies (hence micro-loops) are
expected as a result of each node's independent decision since two
overlapping MNBHs' partial topologies have a lot common information.
3.2 Alternate Path Calculation
We describe the alternate path calculation methodology for the node
N44 in Figure 5. Other nodes in the network repeat the same steps
but using their own MNBHs. For simplicity, we assume that only link
failures occur.
N44 has four local links. For each local link LL_k (k=1,2,3,4), the
following calculations are done per each destination Nij
(i=1,2,3,5,6,7 and j=1,2,3,5,6,7):
- remove LL_k from the topology to anticipate the failure
- calculate the shortest path to Nij using the new topology. If
the new shortest path to Nij (after the failure) is the same as
the primary path to Nij (before the failure) then break (do not
perform the following three steps). Do not store any alternate
path to Nij for the failure of LL_k
- calculate three local shortest alternate paths (SAPs) via
immediate neighbors to Nij (there are three immediate neighbors
after the link failure and therefore three SAPs need to be
calculated). Here SAP is defined as the shortest distance path to
Nij calculated by the Djikstra algorithm after removing LL_k from
the topology
- store the shortest local LFAP among these three local SAPs (if
LFAP exists)
- if none of these local SAPs are loop-free then store the shortest
local SAP as an alternate path
A similar method will be used for calculating remote alternate
paths. N44 has 32 remote links within its MNBH. For each remote link
RL_k (k=5,6,...,32), the following calculations are done per each
destination Nij (i=1,2,3,5,6,7 and j=1,2,3,5,6,7):
- remove RL_k from the topology to anticipate the failure
- calculate the shortest path to Nij using the new topology. If the
shortest path to Nij is the same as the primary path to Nij
then break (do not perform the following three steps). Do not
store any alternate path to Nij for the failure of RL_k
- calculate four remote shortest alternate paths (SAPs) via
immediate neighbors to Nij (since RL_k is not a local interface
there are four immediate neighbors for this node)
- store the shortest remote LFAP among these four remote SAPs
- if none of these SAPs are LFAP then store the shortest remote
SAP
The above algorithms make sure that a local or remote alternate
path (either LFAP or SAP) will be stored only if the primary path
does not function anymore after the failure. Therefore, rLFAP
stores only the required alternate paths and is scalable. Note that
routers only store alternate next-hops (not the alternate path
itself).
3.3 Fast Failure Notification Mechanism
The objectives of a multi-hop failure notification mechanism are as
follows:
- Routers should be notified about failures as fast as possible to
minimize the reroute delay from the primary path to an LFAP
- Failure notification should create minimal overhead in terms of
bandwidth consumption. For example, generating too many LSA
packets in OSPF consumes the available bandwidth and may cause
disruption in other parts of the network beyond the failure
point
- A solution which does not require modifications to the
underlying routing protocol is preferable
- A failure notification should not cause the network instability
under some worst-case scenarios (e.g., sending too many OSPF LSA
messages for transient failures (link flapping) may cause the
network instability)
There are two options for the multi-hop failure notification in
rLFAP when a router detects a local failure:
1) Configuring routing protocol's parameters for the fast failure
propagation by relying on periodic link state updates (e.g.,
LSAs for OSPF and LSPs for IS-IS)
2) Implementing a new efficient fast failure notification mechanism
within the MNBH
3.3.1 Configuring Routing Protocol's Parameters
rLFAP is proposed initially for link state IGPs, where link state
update packets are LSAs in OSPF and LSPs in IS-IS. For simplicity, we
describe the concept for OSPF; all the procedures are applicable to
IS-IS as well. This option does not introduce a new signaling
mechanism but optimizes the existing link state update mechanisms for
rLFAP's performance efficiency.
The flooding procedure by which OSPF distributes LSAs is reliable. A
router packages its new LSA within a link state update packet (may
contain multiple distinct LSAs) and transmits it on each of its
interfaces which are in the same OSPF area impacted by the LSA. Each
recipient acknowledges the router from which the LSA was received,
repackages the LSA within a new link state update packet and sends
it out on each of its interfaces except for the interface on which
the LSA was received.
When the content of an LSA changes, a new LSA is originated
[8]. However, two instances of the same LSA may not be originated
within the time period MinLSInterval. This may require that the
generation of the next instance may be delayed by up to
inLSInterval. Although MinLSInterval is an architectural constant
(default is 5 secs), implementations could make this interval
configurable in order to speed up the failure propagation [12].
Ref. [9] studies how to achieve sub-second IGP convergence in large
IP networks by configuring the routing protocol parameters. Ref.
[10] shows that minLSInterval around 20-30 ms does not generate much
overhead while providing fast failure propagation to multi-hop
routers. Based on these studies, we suggest that minLSInterval which
is around 20-30 ms will provide rLFAP with fast failure notification
mechanism due to the MNBH, where the maximum number of hops between
two nodes in which one node includes another within its MNBH is
limited to X hops. Note also that this interval limits the successive
generations of the same LSA. The maximum delay (i.e., 20-30 ms) is
realized only if there are two successive topology changes in which
the second failure occurs just after an LSA for the first failure is
generated.
3.3.2 An Efficient Failure Flooding Mechanism within MNBH
For the stable wired backbone networks, configuring routing
protocols' parameters for fast failure notification will neither
create much additional signaling overhead nor network instability
since transient failures (i.e., link flapping) are rarely occured in
these networks. However, for wireless mobile ad-hoc or backbone
networks, the drawback of configuring the routing protocol's
parameters for fast failure propagation is that the routing protocol
overhead will be enormous in the case where frequent transient
failures (e.g., link flapping) occur. This overhead is due to too
many LSA updates which are generated for each transient topology
change and flooded to the entire network. The frequent transient
failures may also cause the network instability since the routing
protocol may repeat shortest path calculations and FIB updates too
frequently for each topology change without allowing a common
convergence.
The LSA flooding scope is more explicit in OSPF IPv6 and appears in
the LS type field [13]. There are three separate flooding scopes for
LSAs:
- Link-local scope: LSA is flooded only on the local link and no
further.
- Area scope: LSA is flooded only throughout a single OSPF area.
- AS scope: LSA is flooded throughout the routing domain.
However, rLFAP needs LSA's scope to be configurable to its MNBH and
none of these scopes satisfies this requirement. Moreover, an LSA is
needed by the routing protocol and should be at least flooded within
the same OSPF area.
Therefore, another option for the fast failure notification mechanism
in rLFAP is to implement a new flooding procedure within MNBH which
minimizes routing protocol instability and overhead. The new flooding
mechanism defines a new link update packet (LUP) which is similar to
LSA in OSPF but includes two new fields: Time-To-Live (TTL) and
Stop-Flooding (SF) bit. TTL indicates the maximum number of hops a
new LUP will be transmitted. The transmission is stopped if TTL field
is zero and SF is one (i.e., true). SF decides whether the flooding
of LUP will continue beyond the MNBH. A router continues flooding an
LUP within the MNBH irrespective of its SF value. However, if TTL is
zero, then a router continues the flooding procedure only if the
LUP's SF value is zero (i.e., false). An intermediate router changes
SF value to one if LFAPs, which protect against this particular
failure described in LUP, are found for all destinations in the
network. An intermediate router is not allowed to change SF value
from one to zero because the SF value 1 indicates that LFAPs are
found for all destinations (i.e., full coverage).
LUP has its own timers for controlling its new packet generation and
flooding mechanism. This is another reason for introducing a new
packet format since the timers for controlling LSA flooding can not
be set independently for each LSA. The rLFAP flooding procedure
will be the same as OSPF's flooding procedure but with the following
modifications:
- Parameters (e.g., timers) for the LUP flooding are set to
aggressive values for fast failure notifications while parameters
for LSAs are set to relatively conservative for minimizing the
routing protocol instability and overhead.
- Each router sets TTL field to the number of maximum hops defined
by the MNBH (i.e., parameter X in X-hop MNBH) and SF bit to 0
upon generation of a new LUP packet.
- Each recipient of a LUP packet decrements TTL and sets SF bit to
1 if all required LFAPs are found and then transmits it on each
of its interfaces except for the interface on which the LUP was
received only if TTL field is nonzero.
- Each recipient which observes zero TTL field continue the
flooding procedure if SF bit is still zero; otherwise stops the
flooding procedure.
There are two advantages in this method: i) minimal routing overhead
since flooding LUP update messages are limited to MNBH, ii) fast
failure notification since the parameters of the flooding procedure
(e.g., timers) can be set independently from the routing protocol's
flooding mechanism's parameters. This efficient flooding mechanism
is expected to substantially decrease the amount of additional
overhead and routing protocol instability, which are observed during
the transient failures, while fast failure notifications are still
provided.
3.4 Remote LFAPs and Scalability
In rLFAP, remote LFAPs are calculated only to protect against node
and link failures within the MNBH. Therefore, the number of
LFAPs for a single failure scenario will not be an important issue
in terms of scalability.
However, in case of protecting against multiple failures, the number
of pre-computed LFAPs to protect against some combinations of these
failures might not be scalable in rLFAP depending on the depth of
the MNBH (i.e., parameter X) and the average number of links for
each node. Our design utilizes the concept of KEYLINKS introduced
in Ref. [14] for the purpose of handling this scalability problem.
The main idea behind KEYLINKS is that LFAP for a certain
destination is needed only if the primary path fails. Therefore,
each node maintains what nodes/links in its MNBH are used for
reaching a certain destination and calculates an LFAP only for the
links on its primary path (i.e., LFAP, which is needed only if at
least one of the links on the primary path fails, should not use any
of multiple failures). Maintaining key links and nodes adds
additional complexity while the gain is obtained in terms of
scalability (i.e., fewer LFAPs need to be pre-computed and stored).
For example, N44's 2-hop MNBH includes 12 nodes and 36 links as
shown in Figure 5. For a certain destination, assume that 2 nodes
and 3 links from the 2-hop MNBH of N44 are on the primary path.
Therefore, LFAPs are needed only to protect against 5 members (5
LFAPs) instead of 48 members (48 LFAPs) of the 2-hop MNBH for a
single failure scenario. This reduction for a single destination is
significant since each node needs to pre-compute LFAPs for all
possible destinations in the network.
3.5 Routing Convergence from LFAPs to New Primary Paths
It is crucial for all fast reroute mechanisms that the underlying
dynamic routing protocol should converge to its new optimum routes
once the topology change is disseminated to all routers in the
network. The loops can still form in this phase if the FIB updates
are not done in the right order.
In rLFAP, all nodes within the MNBH have pre-computed alternate
paths protecting against the failures within the MNBH. This makes
sure that all nodes within the MNBH are aware of these failures
and therefore their current routes do not include the failed
resources. This feature provides a flexibility of timely switching
back to new primary paths when new paths are calculated by the
routing protocol. rLFAP switches back to new primary paths after
waiting for a constant delay representing the rLFAP convergence
time within the MNBH (this delay starts after new paths are found
by the routing protocol).
Another important feature of rLFAP is that the minimum number of
next hop changes is expected during switching from LFAPs to new
primary paths of the dynamic routing protocol. The reason is that
the next hop change will occur only if the next hop in the new
primary path is different than the next hop in the alternate path.
Due to the MNBH concept, it is conjectured that the next hops for
LFAPs and the new primary paths will be the same with a high
probability and the minimum number of FIB updates is expected
during switching from LFAPs to new primary paths.
4. Scope and Applicability
This work is proposed initially for link state IGPs (i.e., OSPF and
IS-IS). Further study is needed for extending its applicability to
non-link state IGPs or BGP.
5. Acknowledgements
The authors would like to thank John Scudder, the co-chair of the
IETF RTGWG, for his valuable comments and suggestions on the
preliminary version of this draft.
6. References
Internet-drafts are works in progress available from
[1] M. Shand and S. Bryant, "IP Fast Reroute Framework",
draft-ietf-rtgwg-ipfrr-framework-06.txt, Oct. 2006 (work in
progress).
[2] S. Bryant and M. Shand, "A Framework for Loop-free Convergence",
draft-bryant-shand-lf-conv-frmwk-03.txt, Oct. 2006 (work in
progress).
[3] Alex Zinin, "Analysis and Minimization of Microloops in Link-
state Routing Protocols", draft-ietf-rtgwg-microloop-analysis-
01.txt, Oct. 2005 (work in progress).
[4] Francois et. al., "Loop-free convergence using ordered FIB
updates", , Oct. 2006 (work
in progress).
[5] S. Bryant, M. Shand, "IP Fast Reroute using tunnels", , Apr 2005 (work in progress).
[6] S. Bryant, M. Shand, and S. Previdi, "IP Fast Reroute Using Not-
via Addresses", , Oct. 2006 (Work in progress).
[7] M. Gjoka, V. Ram, and X. Yang, "Evaluation of IP Fast Reroute
Proposals", to appear in IEEE/Create-Net/ICST COMSWARE 2007.
[8] J. Moy, "OSPF Version 2", RFC 2328, April 1998.
[9] P. Francois, C. Filsfils, J. Evans, and O. Bonaventure,
"Achieving sub-second IGP convergence in large IP network",
SIGCOMM Comput. Commun. Rev., 35(3):35-44, 2005.
[10] M. Pitkanen and M. Luoma, "OSPF Flooding Process Optimization",
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7. Authors' Addresses
Ibrahim Hokelek
Applied Research,
Telcordia Technologies, Inc.
RRC-1E313
One Telcordia Drive,
Piscataway, NJ 08854
United States. Email: ihokelek@research.telcordia.com
Mariusz A. Fecko
Applied Research,
Telcordia Technologies, Inc.
RRC-1E326
One Telcordia Drive,
Piscataway, NJ 08854
United States. Email: mfecko@research.telcordia.com
Provin Gurung
Applied Research,
Telcordia Technologies, Inc.
RRC-1D305
One Telcordia Drive,
Piscataway, NJ 08854
United States. Email: pgurung@research.telcordia.com
Sunil Samtani
Applied Research,
Telcordia Technologies, Inc.
RRC-1P387
One Telcordia Drive,
Piscataway, NJ 08854
United States. Email: ssamtani@research.telcordia.com
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