1>This is defined in mbps
2>The bandwidth is only checked during the initial phase during the establishment of the LSP, later on there are no checks done
3>Present in the FLOW_SPEC object of the RSVP path message.
4> Upon receipt of the FLOW_SPEC object the intermediate routers check if the requested b/w is available on the egress links this operation is called Connection Admission Control( CAC).
5> If the requested b/w is not present then a path error message is generated which travels to the head-end node. If CSPF is enabled the HE node checks at the head-end if the appropriate amount of b/w is availble.
R1---------R2----------R3------R4
6>A path message is sent from R1 to R4 with a specific amount of b/w the path message reaches r2, r2 checks the egress interface to see if the amount of b/w is present if it is present the path message is sent to R3, in this case no b/w is reserved at this stage as R2 is not sure if the b/w reservation will also succeed on the remaining nodes this is just a sanity check.
7>After the path message reaches the R4, a RESV message is sent from R4 which goes to R3, once the RESV message is received the bandwidth is reserved, and the unreserved b/w is propogated to all the other nodes.
8> Show router rsvp interface
The above comand shows the total b/w and the reserved b/w the admin status and the active sessions. Reserved b/w refers to the summation of the b/w of the all the lsp's on that particular interface.
9>The unreserved b/w is updated on with the TE updates.
10> Over-subscription or undersubsription is possible for a particular link.
11> config> router>rsvp#
interface abc
subscription 40
This sets the b/w of a particular link to 400 mbps
12> If a particular amount of b/w is not available a failure code is generated in the Path message which is known as admission control error if CSPf is not enabled the LSP continues to establish this session although without much success.
13> An alternative path is used if CSPF is enabled on the link which is not the IGP based path.
14> By default whenever there is a change in the bandwidth the IGP updates are triggered, which are flooded throughout the entire network in a scaled network with a large amount of LSP this can lead to a huge amount of updates which can be overhead for the network and causes processing power.
15> To reduce the amount of updates bandwidth update trigger feature can be used, in this case updates are only triggered when the reserved bandwidth only crosses certain thresholds.
Thresholds can be defined as up (rising) or down (falling) direction
16> In the up direction LSA TE updates are only sent when the threshold rises from the threshold which is defined, at the min at least 1 threshold should be defined and at the max 16 thresholds can be defined. These are defined as the % of the link b/w
In the down direction TE updates are sent only when the b/w falls below the bandwidth which is defined.
17> config router rsvp
te-threshold-update this can also be configured on each particular interface
Config router rsvp te-up-threshold
config router rsvp te-down-threshold
This can be overriden by individual config per interface.
18> config router rsvp te-threshold-update on-cac-failure this lets the router imediately send a TE update if the bandwidth reservation fails this is to notify the hed-end node immediately that there is no b/w available.
19>config>router>te-threshold# update
Periodic updates can be sent within a range of 1-300 seconds even if there is no change in the link bandwidth.
20> When the following configs are made
config router rsvp
te-threshold-update
The default te-threshold values are valid this can be verified by using the command show router rsvp status.
Or show router rsvp interface xx detail.
21> In some cases the primary and secondary paths for an LSP might cross the same link in some part of the network there are 2 reservation styles for that:-
Shared Explicit:- this is the default and according to this the bandwidth can be shared on the common links. The total reservation is equivalent to the masimum reservation done by either of the LSP path.
Fixed Filter:- The total reservation is the sum of all individual LSP path b/w reservations
22> R1-----R2------R3------R5
| |
|-----R4
If we have the following network the primary and standby paths merge on R2 hence if the b/w is reserved for both in the SE style the highest b/w will be considered
Suppose 500mbps and 300 mbps SE style b/w reserved is 500 mbps, the paths are seperated by the LSP ID's
In the case of FF the max reservation is 800 mbps
23> To configure FF >>>>>>>>>> config.router.rsvp-resv-style ff
24> Make Before Break:- If there is a change in some parameters of an LSP ie for suppose the b/w of the LSP changes or a failover occurs or any other parameters change a new lsp is required to be signalled, in this case the alternative LSP is signalled first and only after the alternative LSP is signalled and established traffic is switched over to the alternative LSP with no traffic loss, if the establishment of the alternative LSP is not successful traffic stays on the old LSP this process is known as MBB. A path error message is sent after establishing the new LSP from the HE node
25> The tunnel-id for the old and the new LSP remains the same, however the LSP id of the new LSP is incremented for a brief period of time both the LSP's can co-exist.
26> MBB is generally used in cases of Fast reroute, optimization of the LSP path, soft pre-emption.
MBB is enabled by default however it can be disabled by using the following command config >router>mpls>lsp#
no adaptive is enabled by default.
27> If there are multiple Equal cost paths to a particular destination for the HE router to reach the TE router, the router chooses the CSPF randomly chooses one of them, the least-fill-configuration option instructs CSPF to choose a link with least amount of b/w reservation.
28> the above faetaure will only work with CSPF enabled.
29> This feature is generally used to eradicate unbalanced reservation of b/w among the links.
30> ECMP need not be enabled for this. Least fill leads to more balanced bandwidth distribution.
31> LSP soft preemption provides relative priorities for the LSP's it allows more important lsp paths preempt the less important LSP paths.
32> LSP paths are alloted different priority levels, a better priority level lsp can topple an lsp with a lower priority level if they contend for the bandwidth.
33> The unreserved b/w values are signalled with IGP TE updates using the unreserved_bw_subtlv.
34> LSP paths have two priority values setup priority and hold priority.
35> The values for both the priorities range from 0 to 7. 0 is the best priority and 7 is the worst priority.
36> LSP A can preempt LSP B and eventually succeed if the setup priority of LSP A is better then the hold priority of LSPB.
37> Setup and hold priorities are signalled through the session attribute object of the RSVP path message.
38> The default setup priority for an LSP is 7 (worst) , with this it cannot pre-empt another LSP and the default hold priority for an LSP is 0 (best) ie once established the LSP cannot be pre-empted by another LSP.
39> Setup priority cannot be lower then its hold priority which can cause undesired loops. Best practice is to set them equal.
40> config router mpls lsp
bandwidth xxxx
priority 2 2
The first value defines the setup priority and the second value defines the hold priority.
41> R1------ R2-----------R3
An LSP is setup between R1 to R3 the priorities (setup & hold) for the LSP is 2. Hence the unreserved bandwidth which will be displayed are the following:-
P0:- 1000000 kbps
P1:- 100000 kbps
P2:- 600000 kbps
P3:- 600000 kbps
P4:- 600000 kbps
P5:- 600000 kbps
P6:- 600000 kbps
P7:- 600000 kbps
42> If another LSP with priority levels between priority levels between 2 to 7 wants to reserve the bandwidth it will only get 600 mbps however an LSP with priority levels of 0 or 1 can still reserve 1000 mbps or 1 gig.
43> Like for eg if a few more LSP are created and Priority Levels P5 to P7 changes to 300000 kbps another LSP needs to be established which requests for 600 mbps, then the priority of that LSP should be between 1 to 4.
44>
2>The bandwidth is only checked during the initial phase during the establishment of the LSP, later on there are no checks done
3>Present in the FLOW_SPEC object of the RSVP path message.
4> Upon receipt of the FLOW_SPEC object the intermediate routers check if the requested b/w is available on the egress links this operation is called Connection Admission Control( CAC).
5> If the requested b/w is not present then a path error message is generated which travels to the head-end node. If CSPF is enabled the HE node checks at the head-end if the appropriate amount of b/w is availble.
R1---------R2----------R3------R4
6>A path message is sent from R1 to R4 with a specific amount of b/w the path message reaches r2, r2 checks the egress interface to see if the amount of b/w is present if it is present the path message is sent to R3, in this case no b/w is reserved at this stage as R2 is not sure if the b/w reservation will also succeed on the remaining nodes this is just a sanity check.
7>After the path message reaches the R4, a RESV message is sent from R4 which goes to R3, once the RESV message is received the bandwidth is reserved, and the unreserved b/w is propogated to all the other nodes.
8> Show router rsvp interface
The above comand shows the total b/w and the reserved b/w the admin status and the active sessions. Reserved b/w refers to the summation of the b/w of the all the lsp's on that particular interface.
9>The unreserved b/w is updated on with the TE updates.
10> Over-subscription or undersubsription is possible for a particular link.
11> config> router>rsvp#
interface abc
subscription 40
This sets the b/w of a particular link to 400 mbps
12> If a particular amount of b/w is not available a failure code is generated in the Path message which is known as admission control error if CSPf is not enabled the LSP continues to establish this session although without much success.
13> An alternative path is used if CSPF is enabled on the link which is not the IGP based path.
14> By default whenever there is a change in the bandwidth the IGP updates are triggered, which are flooded throughout the entire network in a scaled network with a large amount of LSP this can lead to a huge amount of updates which can be overhead for the network and causes processing power.
15> To reduce the amount of updates bandwidth update trigger feature can be used, in this case updates are only triggered when the reserved bandwidth only crosses certain thresholds.
Thresholds can be defined as up (rising) or down (falling) direction
16> In the up direction LSA TE updates are only sent when the threshold rises from the threshold which is defined, at the min at least 1 threshold should be defined and at the max 16 thresholds can be defined. These are defined as the % of the link b/w
In the down direction TE updates are sent only when the b/w falls below the bandwidth which is defined.
17> config router rsvp
te-threshold-update this can also be configured on each particular interface
Config router rsvp te-up-threshold
config router rsvp te-down-threshold
This can be overriden by individual config per interface.
18> config router rsvp te-threshold-update on-cac-failure this lets the router imediately send a TE update if the bandwidth reservation fails this is to notify the hed-end node immediately that there is no b/w available.
19>config>router>te-threshold# update
Periodic updates can be sent within a range of 1-300 seconds even if there is no change in the link bandwidth.
20> When the following configs are made
config router rsvp
te-threshold-update
The default te-threshold values are valid this can be verified by using the command show router rsvp status.
Or show router rsvp interface xx detail.
21> In some cases the primary and secondary paths for an LSP might cross the same link in some part of the network there are 2 reservation styles for that:-
Shared Explicit:- this is the default and according to this the bandwidth can be shared on the common links. The total reservation is equivalent to the masimum reservation done by either of the LSP path.
Fixed Filter:- The total reservation is the sum of all individual LSP path b/w reservations
22> R1-----R2------R3------R5
| |
|-----R4
If we have the following network the primary and standby paths merge on R2 hence if the b/w is reserved for both in the SE style the highest b/w will be considered
Suppose 500mbps and 300 mbps SE style b/w reserved is 500 mbps, the paths are seperated by the LSP ID's
In the case of FF the max reservation is 800 mbps
23> To configure FF >>>>>>>>>> config.router.rsvp-resv-style ff
24> Make Before Break:- If there is a change in some parameters of an LSP ie for suppose the b/w of the LSP changes or a failover occurs or any other parameters change a new lsp is required to be signalled, in this case the alternative LSP is signalled first and only after the alternative LSP is signalled and established traffic is switched over to the alternative LSP with no traffic loss, if the establishment of the alternative LSP is not successful traffic stays on the old LSP this process is known as MBB. A path error message is sent after establishing the new LSP from the HE node
25> The tunnel-id for the old and the new LSP remains the same, however the LSP id of the new LSP is incremented for a brief period of time both the LSP's can co-exist.
26> MBB is generally used in cases of Fast reroute, optimization of the LSP path, soft pre-emption.
MBB is enabled by default however it can be disabled by using the following command config >router>mpls>lsp#
no adaptive is enabled by default.
27> If there are multiple Equal cost paths to a particular destination for the HE router to reach the TE router, the router chooses the CSPF randomly chooses one of them, the least-fill-configuration option instructs CSPF to choose a link with least amount of b/w reservation.
28> the above faetaure will only work with CSPF enabled.
29> This feature is generally used to eradicate unbalanced reservation of b/w among the links.
30> ECMP need not be enabled for this. Least fill leads to more balanced bandwidth distribution.
31> LSP soft preemption provides relative priorities for the LSP's it allows more important lsp paths preempt the less important LSP paths.
32> LSP paths are alloted different priority levels, a better priority level lsp can topple an lsp with a lower priority level if they contend for the bandwidth.
33> The unreserved b/w values are signalled with IGP TE updates using the unreserved_bw_subtlv.
34> LSP paths have two priority values setup priority and hold priority.
35> The values for both the priorities range from 0 to 7. 0 is the best priority and 7 is the worst priority.
36> LSP A can preempt LSP B and eventually succeed if the setup priority of LSP A is better then the hold priority of LSPB.
37> Setup and hold priorities are signalled through the session attribute object of the RSVP path message.
38> The default setup priority for an LSP is 7 (worst) , with this it cannot pre-empt another LSP and the default hold priority for an LSP is 0 (best) ie once established the LSP cannot be pre-empted by another LSP.
39> Setup priority cannot be lower then its hold priority which can cause undesired loops. Best practice is to set them equal.
40> config router mpls lsp
bandwidth xxxx
priority 2 2
The first value defines the setup priority and the second value defines the hold priority.
41> R1------ R2-----------R3
An LSP is setup between R1 to R3 the priorities (setup & hold) for the LSP is 2. Hence the unreserved bandwidth which will be displayed are the following:-
P0:- 1000000 kbps
P1:- 100000 kbps
P2:- 600000 kbps
P3:- 600000 kbps
P4:- 600000 kbps
P5:- 600000 kbps
P6:- 600000 kbps
P7:- 600000 kbps
42> If another LSP with priority levels between priority levels between 2 to 7 wants to reserve the bandwidth it will only get 600 mbps however an LSP with priority levels of 0 or 1 can still reserve 1000 mbps or 1 gig.
43> Like for eg if a few more LSP are created and Priority Levels P5 to P7 changes to 300000 kbps another LSP needs to be established which requests for 600 mbps, then the priority of that LSP should be between 1 to 4.
44>
No comments:
Post a Comment