Transcript Advertising TE Protocols in OSPF

Explicitly advertising the TE
protocols enabled on links in OSPF
Chris Bowers
Shraddha Hegde
Seoul, IETF97
SRLG-aware IPFRR using LDP or node-SIDs (LFA and RLFA)
S
S
SRLG 1001
Shortest path before failure
X
Y
X
Y
SRLG-implied remote failure
W
W
SRLG-aware repair path
Z
D
•
•
•
•
Local failure seen by S
Z
D
Y-to-Z link shares an SRLG with link from S-to-X.
SRLG-aware IP-FRR repair path for needs to use RLFA tunnel to W to avoid Y-to-Z link.
S uses IGP advertisement from Y to determine SRLG of Y-to-Z link.
This application of SRLG for IP-FRR was standardized in RFC 5286 (IPFRR/LFA): Section 3 and RFC 7916 (LFA
Manageability): Section 6.2.4.1.
Using info in Link TLV in TE Opaque LSA for SRLG-aware IP-FRR
Advertisements originated by router Y.
Router LSA
Advertising Rtr = Router-ID-Y
# links = 3
Link Type = point-to-point
Link ID = Router-ID-Z
Link Data = 1.1.5.1
Metric = 10
Link Type = point-to-point
Link ID = Router-ID-W
Link Data = 1.1.9.1
Metric = 10
Link Type = point-to-point
Link ID = Router-ID-S
Link Data = 1.1.1.2
Metric = 10
TE Opaque LSA
Advertising Rtr = Router-ID-Y
Link TLV
S uses values in blue to
correlate each Link TLV with
each link in the Router LSA
S
1.1.1.1
Link type sub-TLV
Point-to-Point
1.1.1.2
Link ID sub-TLV
Link ID = Router-ID-Z
Y
X
1.1.5.1
Local Intf IP addr sub-TLV
Local address = 1.1.5.1
Remote Intf IP addr sub-TLV
Remote address = 1.1.5.2
SRLG sub-TLV
1001
1.1.9.1
1.1.9.2
W
1.1.5.2
RFC 5286:
“Information about remote
link SRLG membership may be
dynamically obtained using
[RFC4205] or [RFC4203].”
• S learns the SRLGs of links from Y using the SRLG sub-TLV in the Link TLV of the TE Opaque LSA
defined in RFC 4203 (OSPF) and RFC 4205 (ISIS).
• This is explicitly described in RFC 5286 (IPFRR/LFA): Section 3 and RFC 7916 (LFA
Manageability): Section 6.2.4.1.
• This has been implemented and deployed in networks for several years.
Z
D
SRLG 1001
SRLG-aware TI-LFA using Node and Adj-SIDs
SRLG 1001
S
S
Shortest path before failure
Local failure seen by S
X
Y
1
X
Y
2
D
2
1
Z
SRLG-implied remote failure
SRLG-aware repair path
Z
D
• Link 1 from Y-to-Z shares an SRLG with link from S-to-X.
• SRLG-aware FRR repair path for needs to use link 2 from Y-to-Z in order to avoid link 1.
• S needs to use IGP advertisements from Y to determine SRLGs on link 1 and 2 and adj-SIDs for link 1 and 2.
Using info in Link TLV and Extended Link TLV for SRLG-aware TI-LFA
Router LSA
Advertising Rtr = Router-ID-Y
# links = 3
Link Type = point-to-point
Link ID = Router-ID-Z
Link Data = 1.1.5.1
Metric = 10
Link Type = point-to-point
Link ID = Router-ID-W
Link Data = 1.1.6.1
Metric = 10
Link Type = point-to-point
Link ID = Router-ID-S
Link Data = 1.1.1.2
Metric = 10
TE Opaque LSA
TE Opaque LSA
Advertising Rtr = Router-ID-Y
Advertising Rtr = Router-ID-Y
Link TLV
Link TLV
Link type sub-TLV
Point-to-Point
Link type sub-TLV
Point-to-Point
Link ID sub-TLV
Link ID = Router-ID-Z
Link ID sub-TLV
Link ID = Router-ID-Z
Local Intf IP addr sub-TLV
Local address = 1.1.5.1
Local Intf IP addr sub-TLV
Local address = 1.1.6.1
Remote Intf IP addr sub-TLV
Remote address = 1.1.5.2
Remote Intf IP addr sub-TLV
Remote address = 1.1.6.2
SRLG sub-TLV
SRLG=1001
SRLG sub-TLV
SRLG=1005
Extended Link Opaque LSA
Extended Link Opaque LSA
Advertising Rtr = Router-ID-Y
Advertising Rtr = Router-ID-Y
Extended Link TLV
Link type = Point-to-Point
Link ID = Router-ID-Z
Link Data = 1.1.5.1
Extended Link TLV
Link type = Point-to-Point
Link ID = Router-ID-Z
Link Data = 1.1.6.1
Adjacency-SID sub-TLV
Label = 2001
Adjacency-SID sub-TLV
Label = 2002
Correlated Link Information
Advertising Rtr = Router-ID-Y
Link Type = point-to-point
Link ID = Router-ID-Z
Link Data/Local Addr = 1.1.5.1
Remote address = 1.1.5.2
SRLG=1001
Adj-SID Label = 2001
Advertising Rtr = Router-ID-Y
Link Type = point-to-point
Link ID = Router-ID-Z
Link Data/Local Addr = 1.1.6.1
Remote address = 1.1.6.2
SRLG=1005
Adj-SID Label = 2001
S
1.1.1.1
1.1.1.2
X
Y
1.1.5.1
1.1.6.1
1.1.5.2
1.1.6.2
Z
D
SRLG 1001
• Implementations already make these correlations today.
Scenarios involving SR and RSVP in the same network
• SR only network
• No problem
• RSVP only network
• No problem
• SR and RSVP both in the network on the same links
• No problem
• SR on some links and RSVP on other links
• Short-term workaround
• Long-term solution
Interaction with RSVP
SR-only domain
Y is advertising the Link TLV in the TE Opaque LSA
for the two links from Y-to-Z. Therefore, assume
that RSVP is enabled on those links. Include the
links in CSPF computations and potentially try to
signal RSVP LSPs across those links.
RSVP-only domain
S
R
RSVP ingress
router
X
L
Y
1
O
TE Opaque LSA
Extended Link Opaque LSA
Advertising Rtr = Router-ID-Y
Advertising Rtr = Router-ID-Y
Link TLV
Link type sub-TLV
Point-to-Point
2
Z
This may not be the behavior
desired by the operator.
Link ID sub-TLV
Link ID = Router-ID-Z
M
P
Local Intf IP addr sub-TLV
Local address = 1.1.5.1
Remote Intf IP addr sub-TLV
Remote address = 1.1.5.2
SRLG sub-TLV
SRLG=1001
SRLG 1001
D
N
Extended Link TLV
Link type = Point-to-Point
Link ID = Router-ID-Z
Link Data = 1.1.5.1
Adjacency-SID sub-TLV
Label = 2001
Solution proposed in draft-hegde-ospf-advertising-te-protocols-00
SR-only domain
Y is advertising the TE-protocol sub-TLV without
the RSVP flag set for the two links from Y-to-Z.
RSVP is not enabled on those links, so don’t
include them in the CSPF and don’t try to signal
RSVP LSPs across them.
RSVP-only domain
S
R
RSVP ingress
router
TE Opaque LSA
Extended Link Opaque LSA
Advertising Rtr = Router-ID-Y
Advertising Rtr = Router-ID-Y
Link TLV
X
L
Y
O
Link type sub-TLV
Point-to-Point
Link ID sub-TLV
Link ID = Router-ID-Z
Local Intf IP addr sub-TLV
Local address = 1.1.5.1
1
2
Z
D
Extended Link TLV
Link type = Point-to-Point
Link ID = Router-ID-Z
Link Data = 1.1.5.1
Adjacency-SID sub-TLV
Label = 2001
Remote Intf IP addr sub-TLV
Remote address = 1.1.5.2
M
P
N
SRLG sub-TLV
SRLG=1001
TE protocol sub-TLV
RSVP = NOT enabled
SR = enabled
• Use new TE-protocol sub-TLV to explicitly indicate if RSVP
is enabled on a link or not.
Solution proposed in draft-ppsenak-ospf-te-link-attr-reuse-03
SR-only domain
RSVP-only domain
S
R
X
Y
Extended Link Opaque LSA
Advertising Rtr = Router-ID-Y
Link TLV
RSVP ingress
router
L
TE Opaque LSA
Advertising Rtr = Router-ID-Y
O
Link type sub-TLV
Point-to-Point
Link ID sub-TLV
Link ID = Router-ID-Z
Local Intf IP addr sub-TLV
Local address = 1.1.5.1
Adjacency-SID sub-TLV
Label = 2001
Remote Intf IP addr sub-TLV
Remote address = 1.1.5.2
Local Intf IP addr sub-TLV
Local address = 1.1.5.1
SRLG sub-TLV
SRLG=1001
1
2
Z
D
Extended Link TLV
Link type = Point-to-Point
Link ID = Router-ID-Z
Link Data = 1.1.5.1
Remote Intf IP addr sub-TLV
Remote address = 1.1.5.2
SRLG sub-TLV
SRLG=1001
M
P
N
• Move all needed information from the Link TLV in the TE
Opaque LSA to the Extended Link TLV in the Extended
Link Opaque LSA.
• No longer advertise the Link TLV.
Problems with solution proposed in draft-ppsenak-ospf-te-link-attr-reuse-03
Operator needs RSVP and SR to
co-exist on the same link.
TE Opaque LSA
Extended Link Opaque LSA
Advertising Rtr = Router-ID-Y
Advertising Rtr = Router-ID-Y
Link TLV
Link type sub-TLV
Point-to-Point
Link ID sub-TLV
Link ID = Router-ID-Z
S
R
Local Intf IP addr sub-TLV
Local address = 1.1.5.1
Adjacency-SID sub-TLV
Label = 2001
Remote Intf IP addr sub-TLV
Remote address = 1.1.5.2
Local Intf IP addr sub-TLV
Local address = 1.1.5.1
SRLG sub-TLV
SRLG=1001
Remote Intf IP addr sub-TLV
Remote address = 1.1.5.2
Maximum BW sub-TLV
10G
X
L
Y
O
Extended Link TLV
Link type = Point-to-Point
Link ID = Router-ID-Z
Link Data = 1.1.5.1
SRLG sub-TLV
SRLG=1001
Max Reservable BW sub-TLV
Priority 0 = 5G
Unreserved BW sub-TLV
Priority 0 = 3G
1
2
Z
•
M
P
•
•
D
N
•
•
•
Y needs to advertise both the Link TLV in the TE Opaque LSA and the
Extended Link TLV in the Extended Link Opaque LSA.
In this example, Local/Remote Interface IP address sub-TLVs and SRLG
sub-TLV are duplicated.
How should S and R interpret this duplicated information in the event of a
conflict?
Current text does not clearly address this scenario.
Rules for dealing with duplicated information are usually complicated.
Better to not duplicate the information in the first place.
draft-hegde-ospf-advertising-te-protocols-00 does not have this problem.
Operator wants RSVP and SR co-exist on the
same link.
TE Opaque LSA
Extended Link Opaque LSA
Advertising Rtr = Router-ID-Y
Advertising Rtr = Router-ID-Y
Link TLV
Link type sub-TLV
Point-to-Point
Link ID sub-TLV
Link ID = Router-ID-Z
S
R
Local Intf IP addr sub-TLV
Local address = 1.1.5.1
Extended Link TLV
Link type = Point-to-Point
Link ID = Router-ID-Z
Link Data = 1.1.5.1
Adjacency-SID sub-TLV
Label = 2001
Remote Intf IP addr sub-TLV
Remote address = 1.1.5.2
SRLG sub-TLV
SRLG=1001
Maximum BW sub-TLV
10G
X
L
Y
1
Max Reservable BW sub-TLV
Priority 0 = 5G
Unreserved BW sub-TLV
Priority 0 = 3G
2
Z
D
O
TE protocol sub-TLV
RSVP = enabled
SR = enabled
M
P
N
• No information is duplicated, so there is no possibility of
conflicting information that needs to be resolved.
Comparison of two proposed solutions
draft-hegde-ospfadvertising-te-protocols
draft-ppsenak-ospf-telink-attr-reuse-03
SR-only network
No problem
No problem
RSVP-only network
No problem
No problem
SR on some links and RSVP
on other links
Addresses problem
Addresses problem
SR and RSVP both in the
network on the same links
No problem
Creates new problems
Existing deployments of
RLFA that use SRLG info
No problem
Creates new problems
A potential new bandwidth-related sub-TLV for SR-TE
• For example, it may be useful to define a new
bandwidth related sub-TLV: “Bandwidth Usable for
SR-TE”
• If we standardize a new “Bandwidth Usable for SRTE” sub-TLV, we should decide whether it goes in
the Link TLV or the Extended Link TLV.
• New attributes can make use of the Extended Link
TLV if that makes sense.
TE Opaque LSA
Extended Link Opaque LSA
Advertising Rtr = Router-ID-Y
Advertising Rtr = Router-ID-Y
Link TLV
Link type sub-TLV
Point-to-Point
Link ID sub-TLV
Link ID = Router-ID-Z
Local Intf IP addr sub-TLV
Local address = 1.1.5.1
Remote Intf IP addr sub-TLV
Remote address = 1.1.5.2
SRLG sub-TLV
SRLG=1001
Maximum BW sub-TLV
10G
Max Reservable BW sub-TLV
Priority 0 = 5G
Unreserved BW sub-TLV
Priority 0 = 3G
• However, we shouldn’t move attributes that have
been defined for the Link TLV to the Extended Link
TLV.
TE protocol sub-TLV
RSVP = enabled
SR = enabled
Extended Link TLV
Link type = Point-to-Point
Link ID = Router-ID-Z
Link Data = 1.1.5.1
Adjacency-SID sub-TLV
Label = 2001
BW Usable for SR-TE
3G
Potentially useful new sub-TLV: “bandwidth usable for SR-TE”
Max link bandwidth = 10G
10G
Explicitly leaves bandwidth non-SR-TE
(shortest path routed) traffic.
SR controller uses “bandwidth usable for SR-TE” to
compute available bandwidth for SR LSPs.
SR LSP 4
SR LSP 3
SR LSP 2
Bandwidth available for SR = 6G
SR LSP 1
0
1
2
3
4
5
6
7
Carving up bandwidth for RSVP-TE and SR-TE on the same link
link bandwidth = 10G
10G
Bandwidth available for SR-TE = 3G
SR LSP 1
SR controller uses “bandwidth usable for SR-TE” to
compute bandwidth usable for SR-TE LSPs.
SR LSP 2
Explicitly leaves bandwidth for other traffic.
Maximum (RSVP) reservable link bandwidth = 6G
5
RSVP LSP 4
Unreserved Bandwidth
RSVP LSP 3
0G
Priority 0 unreserved bandwidth = 1G
Priority 1 unreserved bandwidth = 2G
…
RSVP LSP 2
RSVP LSP 1
0
1
2
3
4
5
6
7