Base Resource Handling Procedures

If the peer or the local LSR does not support the Overload Protection Capability, it means that the associated adjacency [interface/peer] is brought down as part of the base resource handling mechanism.

The user can determine which interface or targeted peer was shut down, by applying the following commands:

- [show router ldp interface resource-failures]

- [show router ldp targ-peer resource-failures]


show router ldp interface resource-failures 
===============================================================================
LDP Interface Resource Failures
===============================================================================
srl                                     srr
sru4                                    sr4-1-5-1
===============================================================================

show router ldp targ-peer resource-failures 
===============================================================================
LDP Peers Resource Failures
===============================================================================
10.20.1.22                              192.168.1.3
===============================================================================

A trap is also generated for each interface or targeted peer:

16 2013/07/17 14:21:38.06 PST MINOR: LDP #2003 Base LDP Interface Admin State
"Interface instance state changed - vRtrID: 1, Interface sr4-1-5-1, administrati
ve state: inService, operational state: outOfService"

13 2013/07/17 14:15:24.64 PST MINOR: LDP #2003 Base LDP Interface Admin State
"Interface instance state changed - vRtrID: 1, Peer 10.20.1.22, administrative s
tate: inService, operational state: outOfService"

The user can then check that the base resource handling mechanism has been applied to a specific interface or peer by running the following show commands:

- [show router ldp interface detail]

- [show router ldp targ-peer detail]


    show router ldp interface detail 
===============================================================================
LDP Interfaces (Detail)
===============================================================================
-------------------------------------------------------------------------------
Interface "sr4-1-5-1"
-------------------------------------------------------------------------------
Admin State        : Up                  Oper State       : Down
Oper Down Reason   : noResources  <----- //link LDP resource exhaustion handled
Hold Time          : 45                  Hello Factor     : 3
Oper Hold Time     : 45                  
Hello Reduction    : Disabled            Hello Reduction *: 3
Keepalive Timeout  : 30                  Keepalive Factor : 3
Transport Addr     : System              Last Modified    : 07/17/13 14:21:38
Active Adjacencies : 0                   
Tunneling          : Disabled            
Lsp Name           : None
Local LSR Type     : System
Local LSR          : None
BFD Status         : Disabled            
Multicast Traffic  : Enabled             
-------------------------------------------------------------------------------

show router ldp discovery interface "sr4-1-5-1" detail 
===============================================================================
LDP Hello Adjacencies (Detail)
===============================================================================
-------------------------------------------------------------------------------
Interface "sr4-1-5-1"
-------------------------------------------------------------------------------
Local Address      : 192.168.2.110      Peer Address        : 192.168.0.2
Adjacency Type     : Link               State               : Down            
===============================================================================


show router ldp targ-peer detail 
===============================================================================
LDP Peers (Detail)
===============================================================================
-------------------------------------------------------------------------------
Peer 10.20.1.22
-------------------------------------------------------------------------------
Admin State        : Up              Oper State           : Down
Oper Down Reason   : noResources     <----- // T-LDP resource exhaustion handled
Hold Time          : 45              Hello Factor         : 3
Oper Hold Time     : 45              
Hello Reduction    : Disabled        Hello Reduction Fact*: 3
Keepalive Timeout  : 40              Keepalive Factor     : 4
Passive Mode       : Disabled        Last Modified        : 07/17/13 14:15:24
Active Adjacencies : 0               Auto Created         : No
Tunneling          : Enabled         
Lsp Name           : None
Local LSR          : None
BFD Status         : Disabled        
Multicast Traffic  : Disabled        
-------------------------------------------------------------------------------

show router ldp discovery peer 10.20.1.22 detail       
===============================================================================
LDP Hello Adjacencies (Detail)
===============================================================================
-------------------------------------------------------------------------------
Peer 10.20.1.22
-------------------------------------------------------------------------------
Local Address      : 192.168.1.110      Peer Address        : 10.20.1.22
Adjacency Type     : Targeted           State               : Down   <----- 
//T-LDP resource exhaustion handled
===============================================================================

Besides interfaces and targeted peer, locally originated FECs may also be put into overload. These are the following:

- unicast fec-originate pop

- multicast local static p2mp-fec type=1 [on leaf LSR]

- multicast local Dynamic p2mp-fec type=3 [on leaf LSR]

The user can check if only remote and, or local FECs have been set in overload by the resource base resource exhaustion mechanism using the following command:

- [tools dump router ldp instance]

The relevant part of the output is described below:

{...... snip......}
Num OLoad Interfaces:      4     <----- //#LDP interfaces resource in exhaustion
Num Targ Sessions:         72          Num Active Targ Sess:  62
Num OLoad Targ Sessions:   7     <----- //#T-LDP peers in resource exhaustion
Num Addr FECs Rcvd:        0           Num Addr FECs Sent:    0
Num Addr Fecs OLoad:       1     <----- //# of local/remote unicast FECs in Overload
Num Svc FECs Rcvd:         0           Num Svc FECs Sent:     0
Num Svc FECs OLoad:        0     <----- // # of local/
remote service Fecs in Overload
Num mcast FECs Rcvd:       0           Num Mcast FECs Sent:   0
Num mcast FECs OLoad:      0     <----- // # of local/
remote multicast Fecs in Overload
{...... snip......}

When at least one local FEC has been set in overload the following trap occurs:

23 2013/07/17 15:35:47.84 PST MINOR: LDP #2002 Base LDP Resources Exhausted 
"Instance
 state changed - vRtrID: 1, administrative state: inService, operationa l state:
 inService"

After the user has detected that at least, one link LDP or T-LDP adjacency has been brought down by the resource exhaustion mechanism, he/she must protect the router by applying one or more of the following to free resources up:

Identify the source for the [unicast/multicast/service] FEC flooding.
Configure the appropriate [import/export] policies and, or delete the excess [unicast/multicast/service] FECs not currently handled.

Next, the user has to manually attempt to clear the overload (no resource) state and allow the router to attempt to restore the link and targeted sessions to its peer.

Note:

Because of the dynamic nature of FEC distribution and resolution by LSR nodes, one cannot predict exactly which FECs and which interfaces or targeted peers are restored after performing the following commands if the LSR activates resource exhaustion again.

One of the following commands can be used:

- [clear router ldp resource-failures]

Clears the overload state and attempt to restore adjacency and session for LDP interfaces and peers.
Clear the overload state for the local FECs.

- [clear router ldp interface ifName]

- [clear router ldp peer peerAddress]

Clears the overload state and attempt to restore adjacency and session for LDP interfaces and peers.
These two commands do not clear the overload state for the local FECs.