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The Subnetwork Bandwidth Manager (SBM) feature answers this requirement for RSVP in relation to IEEE 802-based networks. SBM specifies a signalling method and protocol for LAN-based admission control for RSVP flows. SBM allows RSVP-enabled routers and Layer 2 and Layer 3 devices to support reservation of LAN resources for RSVP-enabled data flows. The SBM signalling method is similar to that of RSVP itself. SBM protocol entities have the following features:
A managed segment includes those interconnected parts of a shared LAN that are not separated by DSBMs. The presence of a DSBM makes the segment a managed one. One or more SBMs may exist on a managed segment, but there can be only one DSBM on each managed segment.
You can configure an interface on routers connected to the segment to participate in the DSBM election process. The contender configured with the highest priority becomes the DSBM for the managed segment.
If you do not configure a router as a DSBM candidate and RSVP is enabled, then the system interacts with the DSBM if a DSBM is present on the segment. In fact, if a DSBM, identifying itself as such, exists on the segment, the segment is considered a managed segment and all RSVP message forwarding will be based on the SBM message forwarding rules. This behavior exists to allow cases in which you might not want an RSVP-enabled interface on a router connected to a managed segment interface to become a DSBM, but you want it to interact with the DSBM if one is present managing the segment.
Figure 1 shows a managed segment in an Layer 2 domain that interconnects a set of hosts and routers.
When a DSBM client sends or forwards an RSVP PATH message over an interface attached to a managed segment, it sends the PATH message to the segment's DSBM instead of to the RSVP session destination address, as is done in conventional RSVP processing. As part of its message processing procedure, the DSBM builds and maintains a PATH state for the session and notes the previous Layer 2/Layer 3 hop from which it received the PATH message. After processing the PATH message, the DSBM forwards it toward its destination address.
The DSBM receives the RSVP reservation request (RSVP RESV) message and processes it in a manner similar to how RSVP itself handles reservation request processing, basing the outcome on available bandwidth. The procedure is as follows:
The SBM feature enables admission control over IEEE 802-styled networks.
SBM is not supported currently on Token Ring LANs.
The SBM feature is used in conjunction with RSVP, which is documented in the Quality of Service Solutions Configuration Guide and the Quality of Service Solutions Command Reference.
For related information on this feature, refer to the following documents:
This feature runs on all platforms that also support RSVP beginning with Release 12.0(5)T.
Designated Subnetwork Bandwidth Manager---See DSBM.
DSBM---A protocol entity that resides in a Layer 2 or Layer 3 device and manages resources on a Layer 2 segment. Only one, if any, DSBM exists for each Layer 2 segment.
DSBM clients---Entities that transmit traffic onto a managed segment and use the services of a DSBM for the managed segment for admission control over a LAN segment. DSBM clients are always Layer 3 entities because only Layer 3 (or higher) entities are expected to send traffic requiring resource reservations.
extended segment---Those parts of a network that are members of the same IP subnet and are not separated by any Layer 3 devices. Several managed segments interconnected by Layer 2 devices constitute an extended segment.
Layer 2---Also referred to as the link layer of the ISO seven-layer model, comprises data link layer technologies such as IEEE 802.3 Ethernet.
Layer 2 devices---Devices that implement only Layer 2 functionality. These devices include 802.1D bridges and switches.
Layer 3---Network layer of the ISO seven-layer model. SBM primarily pertains to networks that use the IP at this layer.
Layer 3 devices---Also known as Layer 3 devices or end stations, these devices include hosts and routers that use Layer 3 and higher layer protocols or application programs that make resource reservations.
managed Layer 2 domain---A Layer 2 domain consisting of managed segments. A managed Layer 2 domain includes a DSBM that exercises admission control over resources at segments in the Layer 2 domain.
managed segment---A segment with a DSBM present that is responsible for exercising admission control over requests for resource reservations. A managed segment includes those interconnected parts of a shared LAN that are not separated by DSBMs.
SBM---A protocol entity that resides in a Layer 2 or Layer 3 device and can manage resources on a segment. When more than one SBM exists on a segment, one of the SBMs is elected to be the DSBM.
SBM transparent device---A device that is unaware of SBMs or DSBMs and therefore does not participate in the SBM-based admission control procedure over a managed segment. An SBM transparent device may or may not be RSVP aware.
segment---A Layer 2 physical segment that is shared by one or more senders, such as a shared Ethernet or Token Ring wire resolving contention for media access using CSMA or token passing.
subnet---In regard to SBM, a group of Layer 3 devices sharing a common Layer 3 network address prefix along with the set of segments making up the Layer 2 domain in which they are located.
Subnetwork Bandwidth Manager---See SBM.
traffic class---An aggregation of data flows that are given similar service within a switched network.
To configure SBM, perform the following task:
| Command | Purpose |
|---|---|
Router(config-if)# ip rsvp dsbm-candidate [priority] |
| Command | Purpose |
|---|---|
Router# show ip rsvp sbm |
The command output identifies the interface by name and IP address, and it shows whether the interface has been configured as a DSBM contender. If the interface is a contender, the DSBM Priority field displays its priority. The DSBM election process is dynamic, addressing any new contenders configured as participants. Consequently, at any given time, an incumbent DSBM might be replaced by one configured with a higher priority.
router1# show ip rsvp sbm Interface DSBM Addr DSBM Priority DSBM Candidate My Priority Et1 1.1.1.1 70 yes 70 Et2 145.2.2.150 100 yes 100
interface Ethernet2 ip address 145.2.2.150 255.255.255.0 no ip directed-broadcast ip pim sparse-dense-mode no ip mroute-cache media-type 10BaseT ip rsvp bandwidth 7500 7500 ip rsvp dsbm-candidate 100 end
This section documents the following new commands. All other commands used with this feature are documented in the Cisco IOS Release 12.0 command references.
To enable Resource Reservation Protocol (RSVP) and Subnetwork Bandwidth Manager (SBM) for IP on an interface, use the ip rsvp bandwidth interface configuration command. To disable RSVP and SBM on an interface, use the no form of this command.
ip rsvp bandwidth [interface-kbps [single-flow-kbps]]
interface-kbps | (Optional) Amount of bandwidth (in kbps) on the interface to be reserved. The range is 1 to 10000000. |
single-flow-kbps | (Optional) Amount of bandwidth (in kbps) allocated to a single flow. The range is 1 to 10000000. |
RSVP is disabled. If this command is entered without the optional arguments, RSVP is enabled on 75 percent of the link bandwidth.
Interface configuration
| Release | Modification |
|---|---|
11.2 | This command was introduced. |
12.0(5)T | This command was revised to support SBM. |
This command is not supported on Versatile Interface Processor-based routers. RSVP is disabled by default to allow backward compatibility with systems that do not implement RSVP. Weighted Random Early Detection (WRED) or fair queueing must be enabled first.
The following example shows a T1 (1536 kbps) link configured to permit RSVP reservation of up to 1158 kbps, but no more than 100 kbps for any given flow on serial interface 0. Fair queueing is configured with 15 reservable queues to support those reserved flows, should they be required.
router(config)# interface serial 0
router(config-if)# fair-queue 64 256 15
router(config-if)# ip rsvp bandwidth 1158 100
| Command | Description |
fair-queue | Displays information about SBM configured for a specific RSVP-enabled interface or for all RSVP-enabled interfaces on the router. |
ip rsvp dsbm-candidate | Configures an interface as a DSBM candidate. |
ip rsvp neighbors | Enables neighbors to request a reservation. |
ip rsvp reservations | Enables a router to simulate RSVP RESV message reception from the sender. |
ip rsvp sender | Enables a router to simulate RSVP PATH message reception from the sender. |
ip rsvp udp-multicast | Instructs the router to generate UDP-encapsulated RSVP multicasts whenever it generates an IP multicast. |
random-detect | Enables random early detection on an interface. |
show ip rsvp installed | Displays RSVP-related installed filters and corresponding bandwidth information. |
show ip rsvp interface | Displays RSVP-related interface information. |
show ip rsvp reservation | Displays RSVP-related receiver information currently in the database. |
show ip rsvp sbm | Displays information about SBM configured for a specific RSVP-enabled interface or all RSVP-enabled interfaces on the router. |
show ip rsvp sender | Displays RSVP-related sender information currently in the database. |
To configure an interface as a Designated Subnetwork Bandwidth Manager (DSBM) candidate, use the ip rsvp dsbm-candidate interface configuration command. To disable DSBM on an interface, which exempts the interface as a DSBM candidate, use the no form of this command.
ip rsvp dsbm-candidate [priority]
priority | (Optional) A value in the range of 64 to 128. Among contenders for the DSBM, the interface with the highest priority number wins the DSBM election process. |
An interface is not configured as a DSBM contender by default. If you use this command to enable the interface as a DSBM candidate and you do not specify a priority, the default priority of 64 is assumed.
Interface configuration
| Release | Modification |
|---|---|
12.0(5)T | This command was introduced. |
SBM protocol entities, any one of which can manage resources on a segment, can reside in Layer 2 or Layer 3 devices. Many SBM-capable devices may be attached to a shared Layer 2 segment. When more than one SBM exists on a given segment, one of the SBMs is elected to be the DSBM. The elected DSBM is responsible for exercising admission control over requests for resource reservations on a segment, which, in the process, becomes a managed segment. A managed segment includes those interconnected parts of a shared LAN that are not separated by DSBMs. In all circumstances, only one, if any, DSBM exists for each Layer 2 segment.
You can configure an interface to have a DSBM priority in the range of 64 to 128. You can exempt an interface from participation in the DSBM election on a segment but still allow the system to interact with the DSBM if a DSBM is present on the segment. In other words, you can allow an RSVP-enabled interface on a router connected to a managed segment to be managed by the DSBM even if you do not configure that interface to participate as a candidate in the DSBM election process. To exempt an interface from DSBM candidacy, do not issue the ip rsvp dsbm-candidate command on that interface.
The following example configures interface Ethernet2 as a DSBM candidate with a priority of 100:
interface Ethernet2 ip rsvp dsbm-candidate 100
| Command | Description |
show ip rsvp sbm | Displays information about an SBM configured for a specific RSVP-enabled interface or for all RSVP-enabled interfaces on the router. |
interface-name | (Optional) Name of the interface for which you want to display SBM configuration information. |
EXEC
| Release | Modification |
|---|---|
12.0(5)T | This command was introduced. |
To obtain SBM configuration information about a specific interface configured to use RSVP, specify the interface name with the show ip rsvp sbm command. To obtain information about all interfaces enabled for RSVP on the router, use the show ip rsvp sbm command without specifying an interface name.
The following example displays information for the two RSVP-enabled Ethernet interfaces Et1 and Et2 on router1:
router# show ip rsvp sbm Interface DSBM Addr DSBM Priority DSBM Candidate My Priority Et1 1.1.1.1 70 yes 70 Et2 145.2.2.150 100 yes 100
The following example displays information about the RSVP-enabled Ethernet interface e2 on router1:
router# show ip rsvp sbm e2 Interface DSBM Addr DSBM Priority DSBM candidate My Priority e2 145.2.2.150 100 yes 100
Table 1 identifies the fields and their values displayed as output of the show ip rsvp sbm command.
| Field | Description |
|---|---|
Interface | Name of the DSBM-candidate interface on the router. |
DSBM Addr | IP address of the DSBM. |
DSBM Priority | Priority of the DSBM. |
DSBM Candidate | Yes if the ip rsvp dsbm-candidate command was issued for this SBM to configure it as a DSBM candidate. No if it was not so configured. |
My Priority | Priority configured for this interface. |
| Command | Description |
ip rsvp dsbm-candidate | Configures an interface as a DSBM candidate. |
This section documents new Cisco IOS Release 12.0(5)T debug commands related to SBM. All other commands used with this feature are documented in the Cisco IOS Release 12.0 Quality of Service Solutions Command Reference publication.
This command has no arguments or keywords.
This command is disabled by default.
The debug ip rsvp command provides information about messages received, minimal detail about the content of these messages, and information about state transitions. To obtain detailed information about RSVP and SBM, use the debug ip rsvp detail command.
| Release | Modification |
|---|---|
12.0(5)T | This command was introduced. |
The following example enables output of debug information about SBM message processing, the DSBM election process, and RSVP message processing information on router2:
router# debug ip rsvp RSVP debugging is on router2# *Dec 31 16:42:14.635: RSVP: send I_AM_DSBM message from 145.2.2.150 *Dec 31 16:42:14.635: RSVP: IP to 224.0.0.17 length=88 checksum=C788 Ethernet2) *Dec 31 16:42:19.635: RSVP: send I_AM_DSBM message from 145.2.2.150 *Dec 31 16:42:19.635: RSVP: IP to 224.0.0.17 length=88 checksum=C788 (Ethernet2) *Dec 31 16:42:20.823: RSVP: PATH message for 145.5.5.202(Ethernet2) from 145.2.2.1 *Dec 31 16:42:22.163: RSVP: send path multicast about 145.5.5.202 on Ethernet2 *Dec 31 16:42:22.163: RSVP: DSBM mgd segment - sending to ALLSBMADDRESS *Dec 31 16:42:22.163: RSVP: IP to 224.0.0.17 length=212 checksum=DCAB (Ethernet2) *Dec 31 16:42:23.955: RSVP: Sending RESV message for 145.5.5.202 *Dec 31 16:42:23.955: RSVP: send reservation to 145.2.2.1 about 145.5.5.202 *Dec 31 16:42:23.955: RSVP: IP to 145.2.2.1 length=108 checksum=1420 (Ethernet2) *Dec 31 16:42:24.443: RSVP: RESV message for 145.5.5.202 (Ethernet2) from 145.2.2.2 *Dec 31 16:42:24.635: RSVP: send I_AM_DSBM message from 145.2.2.150 *Dec 31 16:42:24.635: RSVP: IP to 224.0.0.17 length=88 checksum=43AF (Ethernet2)
| Command | Description |
debug ip rsvp detail | Displays detailed information about RSVP and SBM. |
debug ip rsvp detail sbm | Displays detailed information about the contents of SMB messages only, and SBM and DSBM state transitions. |
ip rsvp dsbm-candidate | Configures an interface as a DSBM candidate. |
show ip rsvp sbm | Displays information about SBM configured for a specific RSVP-enabled interface or all RSVP-enabled interfaces on the router. |
This command has no arguments or keywords.
This command is disabled by default.
| Release | Modification |
|---|---|
12.0(5)T | This command was introduced. |
The following example shows the detailed debug information about RSVP and SBM that is available when you enable debug mode through the debug ip rsvp detail command: router# debug ip rsvp detail RSVP debugging is on router2#u *Dec 31 16:44:29.651: RSVP: send I_AM_DSBM message from 145.2.2.150 *Dec 31 16:44:29.651: RSVP: IP to 224.0.0.17 length=88 checksum=43AF
(Ethernet2) *Dec 31 16:44:29.651: RSVP: version:1 flags:0000 type:I_AM_DSBM cksum:43AF
ttl:254 reserved:0 length:88 *Dec 31 16:44:29.651: DSBM_IP_ADDR type 1 length 8 : 91020296 *Dec 31 16:44:29.651: HOP_L2 type 1 length 12: 00E01ECE *Dec 31 16:44:29.651: : 0F760000 *Dec 31 16:44:29.651: SBM_PRIORITY type 1 length 8 : 00000064 *Dec 31 16:44:29.651: DSBM_TIMERS type 1 length 8 : 00000F05 *Dec 31 16:44:29.651: SBM_INFO type 1 length 44: 00000000 *Dec 31 16:44:29.651: : 00240C02 00000007 *Dec 31 16:44:29.651: : 01000006 7F000005 *Dec 31 16:44:29.651: : 00000000 00000000 *Dec 31 16:44:29.655: : 00000000 00000000 *Dec 31 16:44:29.655: : 00000000
| Command | Description |
debug ip rsvp | Displays information about SBM message processing, the DSBM election process, and RSVP message processing. |
debug ip rsvp detail sbm | Displays detailed information about the contents of SMB messages only, and SBM and DSBM state transitions. |
ip rsvp dsbm-candidate | Configures an interface as a DSBM candidate. |
show ip rsvp sbm | Displays information about SBM configured for a specific RSVP-enabled interface or all RSVP-enabled interfaces on the router. |
This command has no arguments or keywords.
This command is disabled by default.
The debug ip rsvp detail sbm command provides information about messages received, minimal detail about the content of these messages, and information about state transitions.
| Release | Modification |
|---|---|
12.0(5)T | This command was introduced. |
The following example shows the detailed debug information about SBM and the SBM and DSBM state transitions that is available when you enable debug mode through the debug ip rsvp detail sbm command: router# debug ip rsvp detail sbm RSVP debugging is on router2# *Dec 31 16:45:34.659: RSVP: send I_AM_DSBM message from 145.2.2.150 *Dec 31 16:45:34.659: RSVP: IP to 224.0.0.17 length=88 checksum=9385 (Ethernet2) *Dec 31 16:45:34.659: RSVP: version:1 flags:0000 type:I_AM_DSBM cksum:9385
ttl:254 reserved:0 length:88 *Dec 31 16:45:34.659: DSBM_IP_ADDR type 1 length 8 : 91020296 *Dec 31 16:45:34.659: HOP_L2 type 1 length 12: 00E01ECE *Dec 31 16:45:34.659: : 0F760000 *Dec 31 16:45:34.659: SBM_PRIORITY type 1 length 8 : 0029B064 *Dec 31 16:45:34.659: DSBM_TIMERS type 1 length 8 : 00000F05 *Dec 31 16:45:34.659: SBM_INFO type 1 length 44: 00000000 *Dec 31 16:45:34.659: : 00240C02 00000007 *Dec 31 16:45:34.659: : 01000006 7F000005 *Dec 31 16:45:34.659: : 00000000 00000000 *Dec 31 16:45:34.663: : 00000000 00000000 *Dec 31 16:45:34.663: : 00000000 *Dec 31 16:45:34.663:
| Command | Description |
debug ip rsvp | Displays information about SBM message processing, the DSBM election process, and RSVP message processing. |
debug ip rsvp detail | Displays detailed information about RSVP and SBM |
ip rsvp dsbm-candidate | Configures an interface as a DSBM candidate. |
show ip rsvp sbm | Displays information about SBM configured for a specific RSVP-enabled interface or all RSVP-enabled interfaces on the router. |
Posted: Tue Oct 19 15:27:49 PDT 1999
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