1. Explicitly advertising the TE protocols enabled on links in ISIS
Chris Bowers
Shraddha Hegde
Paul Mattes
Mohan Nanduri
Spencer Giacalone
Imtiyaz Mohammad
Seoul, IETF97

2. SR centralized bandwidth accounting application
SR ingress router 20 20 40 10 Y Z X S D R M N O P
Program SR label stacks R S 30 20 20 20
10G 30 10 30 20
40G
20G
20G X
SR controller Y O
centralized
bandwidth accounting for SR LSPs
20G
20G
30G
20G
Advertisement from Y
LSPDU
Source = SYS-ID-Y Z M P
Extended IS Reach TLV (22) Neighbor = SYS-ID-Z
Metric = 10
Learn topology via BGP-LS
(including link bandwidth)
30G
IPv4 intf addr sub-TLV (6)
Local address =
10G
20G
30G
IPv4 Nbr addr sub-TLV (8)
Local address = D N
Maximum link BW sub-TLV (9)
30G

3. Scenarios involving SR and RSVP in the same network
SR only network
No problem
RSVP only network
SR and RSVP both in the network on the same links
SR on some links and RSVP on other links
Short-term workaround
Long-term solution

4. RSVP may also be running in the network
RSVP may also be running in the network. How does an RSVP ingress router figure out that a remote link has RSVP enabled on it?
This was never actually standardized for either ISIS or OSPF.
For ISIS, different implementations have used different criteria.
RSVP ingress router R S
LSPDU
Source = SYS-ID-Y
Extended IS Reach TLV (22) Neighbor = SYS-ID-Z
Metric = 10 X Y O
Link of interest
IPv4 intf addr sub-TLV (6)
Local address =
IPv4 Nbr addr sub-TLV (8)
Local address = Z
Maximum link BW sub-TLV (9)
30G M P
Max reservable BW sub-TLV (10)
25G D
Unreserved BW sub-TLV (11)
Priority 0 = 12G N

5. For a given implementation, does the presence of a particular ISIS TLV/sub-TLV for a link trigger inclusion in the traffic-engineering database of that link for use by CSPF to find paths to signal using RSVP?
TLV / sub-TLV X Y Z
Superset of TLV/sub-TLVs that trigger RSVP
22 (Extended IS Reachability TLV, includes wide metrics in TLV) No
22 / 3 (Admin Group)
Yes
22 / 4 (Link Local/Remote Id)
22 / 6 (IPv4 Interface Address)
22 / 8 (IPv4 Neighbor Address)
22 / 9 (Max Link Bandwidth)
22 / 10 (Max Reservable Link Bandwidth)
22 / 11 (Unreserved Bandwidth)
22 / 14 (Extended Admin Group)
22 / 18 (TE Default metric)
22/20 Link Protection Type
22/21 Interface Switching Capability
22/22 TE Bandwidth Constraints
22/33-39 TE Metric Extensions from RFC7810
138 (SRLG TLV)
Implementation

6. SR on some links and RSVP on other links
For some implementations, R will assume that RSVP is enabled on Y-to-Z link, due to presence of Max link BW sub-TLV.
Network operator may not want Y-to-Z link to be used for RSVP.
SR ingress router
RSVP ingress router 20 20 40 10 Y Z X S D R M N O P
Program SR label stacks R S 30 20 20 20 30 10 30 20
40G
20G
10G
20G X
SR controller Y O
centralized
bandwidth accounting for SR LSPs
20G
20G
30G
20G
Advertisement from Y
LSPDU
Source = SYS-ID-Y Z M P
Extended IS Reach TLV (22) Neighbor = SYS-ID-Z
Metric = 10
Learn topology via BGP-LS
(including link bandwidth)
30G
IPv4 intf addr sub-TLV (6)
Local address =
10G
20G
30G
IPv4 Nbr addr sub-TLV (8)
Local address = D N
Maximum link BW sub-TLV (9)
30G

7. Short term workaround using administrative groups
RSVP ingress router
Operator configures routers to advertise administrative group 4 for those links without RSVP enabled.
Operator configures constraints on R to exclude links with administrative group 4 from CSPF for RSVP LSPs.
Administrative group chosen to mean RSVP-not-enabled-on-link is local to network, not assigned by IETF. R S
40G
20G
10G
20G X Y O
Advertisement from Y
20G
20G
30G
20G
LSPDU
Source = SYS-ID-Y
Extended IS Reach TLV (22) Neighbor = SYS-ID-Z
Metric = 10
IPv4 intf addr sub-TLV (6)
Local address = Z M P
30G
IPv4 Nbr addr sub-TLV (8)
Local address =
Maximum link BW sub-TLV (9)
30G
10G
30G
20G D
administrative group 4
(defined by operator to mean RSVP-not-enabled-on-link)
administrative group sub-TLV(3)
0….0100 N

8. Long term solution using TE protocol sub-TLV
RSVP ingress router
Operator configures routers to advertise administrative group 4 for those links without RSVP enabled.
Operator configures constraints on R to exclude links with administrative group 4 from CSPF for RSVP LSPs.
Administrative group chosen to mean RSVP-not-enabled-on-link is local to network, not assigned by IETF. R S
40G
20G
10G
20G X Y O
20G
Advertisement from Y
Advertisement from Y
20G
30G
20G
LSPDU
Source = SYS-ID-Y
LSPDU
Source = SYS-ID-Y
Extended IS Reach TLV (22) Neighbor = SYS-ID-Z
Metric = 10
Extended IS Reach TLV (22) Neighbor = SYS-ID-M
Metric = 10 Z M P
30G
IPv4 intf addr sub-TLV (6)
Local address =
IPv4 intf addr sub-TLV (6)
Local address =
10G
30G
20G
IPv4 Nbr addr sub-TLV (8)
Local address =
IPv4 Nbr addr sub-TLV (8)
Local address = D N
Maximum link BW sub-TLV (9)
30G
Maximum link BW sub-TLV (9)
20G
TE protocol sub-TLV (TBD)
RSVP = NOT enabled
TE protocol sub-TLV (TBD)
RSVP = enabled
RSVP enabled
RSVP not enabled

9. 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
Bandwidth available for SR = 6G
SR LSP 2
SR LSP 1 1 2 3 4 5 6 7

10. Carving up bandwidth for RSVP-TE and SR-TE on the same link
link bandwidth = 10G
10G
SR LSP 1
Bandwidth available for SR-TE = 3G
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. 5
Maximum (RSVP) reservable link bandwidth = 6G
RSVP LSP 4
Unreserved Bandwidth
Priority 0 unreserved bandwidth = 1G
Priority 1 unreserved bandwidth = 2G …
RSVP LSP 3
RSVP LSP 2
RSVP LSP 1 0G 1 2 3 4 5 6 7