draft-ietf-issll-is802-sbm-07.txt   draft-ietf-issll-is802-sbm-08.txt 
Internet Engineering Task Force Raj Yavatkar, Intel Internet Engineering Task Force Raj Yavatkar, Intel
INTERNET-DRAFT Don Hoffman, Teledesic INTERNET-DRAFT Don Hoffman, Teledesic
Yoram Bernet, Microsoft Yoram Bernet, Microsoft
Fred Baker, Cisco Fred Baker, Cisco
Michael Speer, Sun Microsystems draft-ietf-issll-is802-sbm-08.txt Michael Speer, Sun Microsystems
November 1998
SBM (Subnet Bandwidth Manager): SBM (Subnet Bandwidth Manager):
A Protocol for RSVP-based Admission Control over IEEE 802-style networks A Protocol for RSVP-based Admission Control over IEEE 802-style networks
Status of this Memo Status of this Memo
This document is an Internet-Draft. Internet-Drafts are working This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
This document is an Internet Draft. Internet Drafts are working
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and its working groups. Note that other groups may also distribute and its working groups. Note that other groups may also distribute
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SBM (Subnet Bandwidth Manager) November, 1998 The list of Internet-Draft Shadow Directories can be accessed at
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SBM (Subnet Bandwidth Manager) March, 1999
Abstract Abstract
This document describes a signaling method and protocol for RSVP-based This document describes a signaling method and protocol for RSVP-based
admission control over IEEE 802-style LANs. The protocol is designed admission control over IEEE 802-style LANs. The protocol is designed
to work both with the current generation of IEEE 802 LANs as well as with the to work both with the current generation of IEEE 802 LANs as well as with the
recent work completed by the IEEE 802.1 committee. recent work completed by the IEEE 802.1 committee.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
1. Introduction 1. Introduction
New extensions to the Internet architecture and service models have New extensions to the Internet architecture and service models have
been defined for an integrated services Inernet [RFC-1633, RFC-2205, been defined for an integrated services Inernet [RFC-1633, RFC-2205,
RFC-2210] so that applications can request specific qualities or lev- RFC-2210] so that applications can request specific qualities or lev-
els of service from an internetwork in addition to the current IP els of service from an internetwork in addition to the current IP
best-effort service. These extensions include RSVP, a resource reser- best-effort service. These extensions include RSVP, a resource reser-
vation setup protocol, and definition of new service classes to be vation setup protocol, and definition of new service classes to be
supported by Integrated Services routers. RSVP and service class supported by Integrated Services routers. RSVP and service class
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assume that the LAN technologies will continue to be a mix of assume that the LAN technologies will continue to be a mix of
legacy shared/ switched LAN segments and newer switched segments legacy shared/ switched LAN segments and newer switched segments
based on IEEE 802.1p specification. Therefore, we specify a sig- based on IEEE 802.1p specification. Therefore, we specify a sig-
naling protocol for managing bandwidth over both legacy and newer naling protocol for managing bandwidth over both legacy and newer
LAN topologies and that takes advantage of the additional func- LAN topologies and that takes advantage of the additional func-
tionality (such as an explicit support for different traffic tionality (such as an explicit support for different traffic
classes or integrated service classes) as it becomes available in classes or integrated service classes) as it becomes available in
the new generation of switches, hubs, or bridges. As a result, the new generation of switches, hubs, or bridges. As a result,
the SBM protocol would allow for a range of LAN bandwidth the SBM protocol would allow for a range of LAN bandwidth
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
management solutions that vary from one that exercises purely management solutions that vary from one that exercises purely
administrative control (over the amount of bandwidth consumed by administrative control (over the amount of bandwidth consumed by
RSVP-enabled traffic flows) to one that requires cooperation (and RSVP-enabled traffic flows) to one that requires cooperation (and
enforcement) from all the end-systems or switches in a IEEE 802 enforcement) from all the end-systems or switches in a IEEE 802
LAN. LAN.
II. This document specifies only a signaling method and protocol for II. This document specifies only a signaling method and protocol for
LAN-based admission control over RSVP flows. We do not define LAN-based admission control over RSVP flows. We do not define
here any traffic control mechanisms for the link layer; the pro- here any traffic control mechanisms for the link layer; the pro-
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best-effort traffic on the same shared media and that raises the best-effort traffic on the same shared media and that raises the
question of the utility of such a mechanism outside a topology question of the utility of such a mechanism outside a topology
consisting only of 802.1p-compliant switches. However, we assume consisting only of 802.1p-compliant switches. However, we assume
that the SBM-based admission control mechanism will still serve a that the SBM-based admission control mechanism will still serve a
useful purpose in a legacy, shared LAN topology for two reasons. useful purpose in a legacy, shared LAN topology for two reasons.
First, assuming that all the nodes that generate Integrated Ser- First, assuming that all the nodes that generate Integrated Ser-
vices traffic flows utilize the SBM-based admission control pro- vices traffic flows utilize the SBM-based admission control pro-
cedure to request reservation of resources before sending any cedure to request reservation of resources before sending any
traffic, the mechanism will restrict the total amount of traffic traffic, the mechanism will restrict the total amount of traffic
generated by Integrated Services flows within the bounds desired generated by Integrated Services flows within the bounds desired
by a LAN administrator. Second, the best-effort traffic generated by a LAN administrator (see discussion of the NonResvSendLimit
by the TCP/IP-based traffic sources is generally rate-adaptive parameter in Appendix C). Second, the best-effort traffic gen-
(using a TCP-style "slow start" congestion avoidance mechanism or erated by the TCP/IP-based traffic sources is generally rate-
a feedback-based rate adaptation mechanism used by audio/video adaptive (using a TCP-style "slow start" congestion avoidance
streams based on RTP/RTCP protocols) and adapts to stay within mechanism or a feedback-based rate adaptation mechanism used by
the available network bandwidth. Thus, the combination of admis- audio/video streams based on RTP/RTCP protocols) and adapts to
sion control and rate adaptation should avoid persistent traffic stay within the available network bandwidth. Thus, the combina-
congestion. This does not, however, guarantee that non- tion of admission control and rate adaptation should avoid per-
Integrated-Services traffic will not interfere with the sistent traffic congestion. This does not, however, guarantee
Integrated Services traffic in the absence of traffic control that non-Integrated-Services traffic will not interfere with the
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
Integrated Services traffic in the absence of traffic control
support in the underlying LAN infrastructure. support in the underlying LAN infrastructure.
3. Organization of the rest of this document 3. Organization of the rest of this document
The rest of this document provides a detailed description of the SBM- The rest of this document provides a detailed description of the SBM-
based admission control procedure(s) for IEEE 802 LAN technologies. based admission control procedure(s) for IEEE 802 LAN technologies.
The document is organized as follows: The document is organized as follows:
* Section 4 first defines the various terms used in the document * Section 4 first defines the various terms used in the document
and then provides an overview of the admission control procedure and then provides an overview of the admission control procedure
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resources on a LAN segment. resources on a LAN segment.
* Appendix A describes the details of the DSBM election algorithm * Appendix A describes the details of the DSBM election algorithm
used for electing a designated SBM on a LAN segment when more used for electing a designated SBM on a LAN segment when more
than one SBM is present. It also describes how DSBM clients dis- than one SBM is present. It also describes how DSBM clients dis-
cover the presence of a DSBM on a managed segment. cover the presence of a DSBM on a managed segment.
* Appendix B specifies the formats of SBM-specific messages used * Appendix B specifies the formats of SBM-specific messages used
and the formats of new RSVP objects needed for the SBM operation. and the formats of new RSVP objects needed for the SBM operation.
* Appendix C describes usage of the DSBM to distribute configura-
tion information to senders on a managed segment.
4. Overview 4. Overview
4.1. Definitions 4.1. Definitions
SBM (Subnet Bandwidth Manager) March, 1999
- Link Layer or Layer 2 or L2: We refer to data-link layer techno- - Link Layer or Layer 2 or L2: We refer to data-link layer techno-
logies such as IEEE 802.3/Ethernet as L2 or layer 2. logies such as IEEE 802.3/Ethernet as L2 or layer 2.
- Link Layer Domain or Layer 2 domain or L2 domain: a set of nodes - Link Layer Domain or Layer 2 domain or L2 domain: a set of nodes
SBM (Subnet Bandwidth Manager) November, 1998
and links interconnected without passing through a L3 forwarding and links interconnected without passing through a L3 forwarding
function. One or more IP subnets can be overlaid on a L2 domain. function. One or more IP subnets can be overlaid on a L2 domain.
- Layer 2 or L2 devices: We refer to devices that only implement - Layer 2 or L2 devices: We refer to devices that only implement
Layer 2 functionality as Layer 2 or L2 devices. These include Layer 2 functionality as Layer 2 or L2 devices. These include
802.1D bridges or switches. 802.1D bridges or switches.
- Internetwork Layer or Layer 3 or L3: Layer 3 of the ISO 7 layer - Internetwork Layer or Layer 3 or L3: Layer 3 of the ISO 7 layer
model. This document is primarily concerned with networks that model. This document is primarily concerned with networks that
use the Internet Protocol (IP) at this layer. use the Internet Protocol (IP) at this layer.
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those interconnected parts of a shared LAN that are not separated those interconnected parts of a shared LAN that are not separated
by DSBMs. by DSBMs.
- Traffic Class: An aggregation of data flows which are given simi- - Traffic Class: An aggregation of data flows which are given simi-
lar service within a switched network. lar service within a switched network.
- User_priority: User_priority is a value associated with the - User_priority: User_priority is a value associated with the
transmission and reception of all frames in the IEEE 802 service transmission and reception of all frames in the IEEE 802 service
model: it is supplied by the sender that is using the MAC ser- model: it is supplied by the sender that is using the MAC ser-
vice. It is provided along with the data to a receiver using the vice. It is provided along with the data to a receiver using the
MAC service. It may or may not be actually carried over the net- MAC service. It may or may not be actually carried over the
work: Token-Ring/802.5 carries this value (encoded in its FC
SBM (Subnet Bandwidth Manager) March, 1999
network: Token-Ring/802.5 carries this value (encoded in its FC
octet), basic Ethernet/802.3 does not, 802.12 may or may not octet), basic Ethernet/802.3 does not, 802.12 may or may not
depending on the frame format in use. 802.1p defines a consistent depending on the frame format in use. 802.1p defines a consistent
way to carry this value over the bridged network on Ethernet, way to carry this value over the bridged network on Ethernet,
Token Ring, Demand-Priority, FDDI or other MAC-layer media using Token Ring, Demand-Priority, FDDI or other MAC-layer media using
SBM (Subnet Bandwidth Manager) November, 1998
an extended frame format. The usage of user_priority is fully an extended frame format. The usage of user_priority is fully
described in section 2.5 of 802.1D [IEEE8021D] and 802.1p described in section 2.5 of 802.1D [IEEE8021D] and 802.1p
[IEEE8021P] "Support of the Internal Layer Service by Specific [IEEE8021P] "Support of the Internal Layer Service by Specific
MAC Procedures". MAC Procedures".
- Subnet: used in this memo to indicate a group of L3 devices shar- - Subnet: used in this memo to indicate a group of L3 devices shar-
ing a common L3 network address prefix along with the set of seg- ing a common L3 network address prefix along with the set of seg-
ments making up the L2 domain in which they are located. ments making up the L2 domain in which they are located.
- Bridge/Switch: a layer 2 forwarding device as defined by IEEE - Bridge/Switch: a layer 2 forwarding device as defined by IEEE
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not separated by any layer 3 devices. Several managed segments, not separated by any layer 3 devices. Several managed segments,
interconnected by layer 2 devices, constitute an extended seg- interconnected by layer 2 devices, constitute an extended seg-
ment. ment.
- Managed L2 domain: An L2 domain consisting of managed segments is - Managed L2 domain: An L2 domain consisting of managed segments is
referred to as a managed L2 domain to distinguish it from a L2 referred to as a managed L2 domain to distinguish it from a L2
domain with no DSBMs present for exercising admission control domain with no DSBMs present for exercising admission control
over resources at segments in the L2 domain. over resources at segments in the L2 domain.
- DSBM clients: These are entities that transmit traffic onto a - DSBM clients: These are entities that transmit traffic onto a
SBM (Subnet Bandwidth Manager) March, 1999
managed segment and use the services of a DSBM for the managed managed segment and use the services of a DSBM for the managed
segment for admission control over a LAN segment. Only the layer segment for admission control over a LAN segment. Only the layer
3 or higher layer entities on L3 devices such as hosts and 3 or higher layer entities on L3 devices such as hosts and
routers are expected to send traffic that requires resource routers are expected to send traffic that requires resource
reservations, and, therefore, DSBM clients are L3 entities. reservations, and, therefore, DSBM clients are L3 entities.
SBM (Subnet Bandwidth Manager) November, 1998
- SBM transparent devices: A "SBM transparent" device is unaware of - SBM transparent devices: A "SBM transparent" device is unaware of
SBMs or DSBMs (though it may or may not be RSVP aware) and, SBMs or DSBMs (though it may or may not be RSVP aware) and,
therefore, does not participate in the SBM-based admission con- therefore, does not participate in the SBM-based admission con-
trol procedure over a managed segment. Such a device uses stan- trol procedure over a managed segment. Such a device uses stan-
dard forwarding rules appropriate for the device and is tran- dard forwarding rules appropriate for the device and is tran-
sparent with respect to SBM. An example of such a L2 device is a sparent with respect to SBM. An example of such a L2 device is a
legacy switch that does not participate in resource reservation. legacy switch that does not participate in resource reservation.
- Layer 3 and layer 2 addresses: We refer to layer 3 addresses of - Layer 3 and layer 2 addresses: We refer to layer 3 addresses of
L3/L2 devices as "L3 addresses" and layer2 addresses as "L2 L3/L2 devices as "L3 addresses" and layer2 addresses as "L2
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shared L2 segment whereas two SBM-capable switches may share a half- shared L2 segment whereas two SBM-capable switches may share a half-
duplex switched segment. In that case, a single DSBM is elected for duplex switched segment. In that case, a single DSBM is elected for
the segment. The procedure for dynamically electing the DSBM is the segment. The procedure for dynamically electing the DSBM is
described in Appendix A. The only other approved method for specifying described in Appendix A. The only other approved method for specifying
a DSBM for a managed segment is static configuration at SBM-capable a DSBM for a managed segment is static configuration at SBM-capable
devices. devices.
The presence of a DSBM makes the segment a "managed segment". Some- The presence of a DSBM makes the segment a "managed segment". Some-
times, two or more L2 segments may be interconnected by SBM tran- times, two or more L2 segments may be interconnected by SBM tran-
sparent devices. In that case, a single DSBM will manage the resources sparent devices. In that case, a single DSBM will manage the resources
for those segments treating the collection of such segments as a sin- for those segments treating the collection of such segments as a
gle managed segment for the purpose of admission control.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
single managed segment for the purpose of admission control.
SBM (Subnet Bandwidth Manager) March, 1999
4.2.1. Basic Algorithm 4.2.1. Basic Algorithm
Figure 1 - An Example of a Managed Segment. Figure 1 - An Example of a Managed Segment.
+-------+ +-----+ +------+ +-----+ +--------+ +-------+ +-----+ +------+ +-----+ +--------+
|Router | | Host| | DSBM | | Host| | Router | |Router | | Host| | DSBM | | Host| | Router |
| R2 | | C | +------+ | B | | R3 | | R2 | | C | +------+ | B | | R3 |
+-------+ +-----+ / +-----+ +--------+ +-------+ +-----+ / +-----+ +--------+
| | / | | | | / | |
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knowledge of link topology allow discovery of link capacity, the knowledge of link topology allow discovery of link capacity, the
configuration may be necessary to limit the fraction of link configuration may be necessary to limit the fraction of link
capacity that can be reserved on a link. Configuration is likely capacity that can be reserved on a link. Configuration is likely
to be static with the current L2/L3 devices. Future work may to be static with the current L2/L3 devices. Future work may
allow for dynamic discovery of this information. This document allow for dynamic discovery of this information. This document
does not specify the configuration mechanism. does not specify the configuration mechanism.
2. DSBM Client Initialization: For each interface attached, a DSBM 2. DSBM Client Initialization: For each interface attached, a DSBM
client determines whether a DSBM exists on the interface. The client determines whether a DSBM exists on the interface. The
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
procedure for discovering and verifying the existence of the DSBM procedure for discovering and verifying the existence of the DSBM
for an attached segment is described in Appendix A. If the client for an attached segment is described in Appendix A. If the client
itself is capable of serving as the DSBM on the segment, it may itself is capable of serving as the DSBM on the segment, it may
choose to participate in the election to become the DSBM. At the choose to participate in the election to become the DSBM. At the
start, a DSBM client first verifies that a DSBM exists in its L2 start, a DSBM client first verifies that a DSBM exists in its L2
domain so that it can communicate with the DSBM for admission domain so that it can communicate with the DSBM for admission
control purposes. control purposes.
In the case of a full-duplex segment, an election may not be In the case of a full-duplex segment, an election may not be
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tion 5). In the process, the DSBM builds the PATH state, tion 5). In the process, the DSBM builds the PATH state,
remembers the router R1 (its L2 and l3 addresses) as the previ- remembers the router R1 (its L2 and l3 addresses) as the previ-
ous hop for the session, puts its own L2 and L3 addresses in ous hop for the session, puts its own L2 and L3 addresses in
the PHOP objects (see explanation later), and effectively the PHOP objects (see explanation later), and effectively
inserts itself as an intermediate node between the sender (or inserts itself as an intermediate node between the sender (or
R1 in Figure 1) and the receiver (host A) on the managed seg- R1 in Figure 1) and the receiver (host A) on the managed seg-
ment. ment.
b) When an application on host A wishes to make a reservation for b) When an application on host A wishes to make a reservation for
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
the RSVP session, host A follows the standard RSVP message pro- the RSVP session, host A follows the standard RSVP message pro-
cessing rules and sends a RSVP RESV message to the previous hop cessing rules and sends a RSVP RESV message to the previous hop
L2/L3 address (the DSBMs address) obtained from the PHOP L2/L3 address (the DSBMs address) obtained from the PHOP
object(s) in the previously received PATH message. object(s) in the previously received PATH message.
c) The DSBM processes the RSVP RESV message based on the bandwidth c) The DSBM processes the RSVP RESV message based on the bandwidth
available and returns an RESVERR message to the requester (host available and returns an RESVERR message to the requester (host
A) if the request cannot be granted. If sufficient resources A) if the request cannot be granted. If sufficient resources
are available and the reservation request is granted, the DSBM are available and the reservation request is granted, the DSBM
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separated by more than one managed segment. In that case, the separated by more than one managed segment. In that case, the
original PATH message would propagate through many DSBMs (one original PATH message would propagate through many DSBMs (one
for each managed segment on the path from R1 to A) setting up for each managed segment on the path from R1 to A) setting up
PATH state at each DSBM. Therefore, the RESV message would pro- PATH state at each DSBM. Therefore, the RESV message would pro-
pagate hop-by-hop in reverse through the intermediate DSBMs and pagate hop-by-hop in reverse through the intermediate DSBMs and
eventually reach the original forwarder (router R1) on the L2 eventually reach the original forwarder (router R1) on the L2
domain if admission control at all DSBMs succeeds. domain if admission control at all DSBMs succeeds.
4.2.2. Enhancements to the conventional RSVP operation 4.2.2. Enhancements to the conventional RSVP operation
The addition of a DSBM for admission control over managed segments (D)SBMs and DSBM clients implement minor additions to the standard
results in some additions to the RSVP message processing rules at a RSVP protocol. These are summarized in this section. A detailed
DSBM client. In the following, we first motivate and summarize the description of the message processing and forwarding rules follows in
additions and a detailed description of the message processing and section 5.
forwarding rules at (D)SBMs and DSBM clients is provided in Section 5:
- Normal RSVP forwarding rules apply at a DSBM client when it is 4.2.2.1 Sending PATH Messages to the DSBM on a Managed Segment
not forwarding an outgoing PATH message over a managed segment.
However, outgoing PATH messages on a managed segment are sent to
the DSBM for the corresponding managed segment (Section 5.2
describes how the PATH messages are sent to the DSBM on a managed
segment).
- In conventional RSVP processing over point-to-point links, RSVP Normal RSVP forwarding rules apply at a DSBM client when it is not
nodes (hosts/routers) use RSVP_HOP object (NHOP and PHOP info) to forwarding an outgoing PATH message over a managed segment. However,
outgoing PATH messages on a managed segment are sent to the DSBM for
the corresponding managed segment (Section 5.2 describes how the PATH
messages are sent to the DSBM on a managed segment).
SBM (Subnet Bandwidth Manager) November, 1998 4.2.2.2 The LAN_NHOP Objects
keep track of the next hop (downstream node in the path of data In conventional RSVP processing over point-to-point links, RSVP nodes
packets in a traffic flow) and the previous hop (upstream nodes (hosts/routers) use RSVP_HOP object (NHOP and PHOP info) to keep track
with respect to the data flow) nodes on the path between a sender of the next hop (downstream node in the path of data packets in a
and a receiver. Routers along the path of a PATH message forward
the message towards the destination address based on the L3 rout-
ing (packet forwarding) tables.
For example, consider the L2 domain in Figure 1. Assume that both SBM (Subnet Bandwidth Manager) March, 1999
the sender (some host X) and the receiver (some host Y) in a RSVP
session reside outside the L2 domain shown in the Figure, but traffic flow) and the previous hop (upstream nodes with respect to the
PATH messages from the sender to its receiver pass through the data flow) nodes on the path between a sender and a receiver. Routers
routers in the L2 domain using it as a transit subnet. Assume along the path of a PATH message forward the message towards the des-
that the PATH message from the sender X arrives at the router R1. tination address based on the L3 routing (packet forwarding) tables.
R1 uses its local routing information to decide which next hop
router (either router R2 or router R3) to use to forward the PATH For example, consider the L2 domain in Figure 1. Assume that both the
message towards host Y. However, when the path traverses a sender (some host X) and the receiver (some host Y) in a RSVP session
managed L2 domain, we require the PATH and RESV messages to go reside outside the L2 domain shown in the Figure, but PATH messages
through a DSBM for each managed segment. Such a L2 domain may from the sender to its receiver pass through the routers in the L2
span many managed segments (and DSBMs) and, typically, SBM proto- domain using it as a transit subnet. Assume that the PATH message from
col entities on L2 devices (such as a switch) will serve as the the sender X arrives at the router R1. R1 uses its local routing
DSBMs for the managed segments in a switched topology. When R1 information to decide which next hop router (either router R2 or
forwards the PATH message to the DSBM (an L2 device), the DSBM router R3) to use to forward the PATH message towards host Y. However,
may not have the L3 routing information necessary to select the when the path traverses a managed L2 domain, we require the PATH and
egress router (between R2 and R3) before forwarding the PATH mes- RESV messages to go through a DSBM for each managed segment. Such a L2
sage. To ensure correct operation and routing of RSVP messages, domain may span many managed segments (and DSBMs) and, typically, SBM
we must provide additional forwarding information to DSBMs. protocol entities on L2 devices (such as a switch) will serve as the
DSBMs for the managed segments in a switched topology. When R1 for-
wards the PATH message to the DSBM (an L2 device), the DSBM may not
have the L3 routing information necessary to select the egress router
(between R2 and R3) before forwarding the PATH message. To ensure
correct operation and routing of RSVP messages, we must provide addi-
tional forwarding information to DSBMs.
For this purpose, we introduce new RSVP objects called LAN_NHOP For this purpose, we introduce new RSVP objects called LAN_NHOP
address objects that keep track of the next L3 hop as the PATH address objects that keep track of the next L3 hop as the PATH message
message traverses an L2 domain between two L3 entities (RSVP PHOP traverses an L2 domain between two L3 entities (RSVP PHOP and NHOP
and NHOP nodes). nodes).
- When a DSBM client (a host or a router acting as the originator 4.2.2.3 Including Both Layer-2 and Layer-3 Addresses in the LAN_NHOP
of a PATH message) sends out a PATH message to the DSBM, it must
include LAN_NHOP information in the message. In the case of a When a DSBM client (a host or a router acting as the originator of a
unicast destination, the LAN_NHOP address specifies the destina- PATH message) sends out a PATH message to the DSBM, it must include
tion address (if the destination is local to its L2 domain) or LAN_NHOP information in the message. In the case of a unicast destina-
the address of the next hop router towards the destination. In tion, the LAN_NHOP address specifies the destination address (if the
our example of an RSVP session involving the sender X and destination is local to its L2 domain) or the address of the next hop
receiver Y with L2 domain in Figure 1 acting as the transit sub- router towards the destination. In our example of an RSVP session
net, R1 is the ingress node that receives the PATH message. R1 involving the sender X and receiver Y with L2 domain in Figure 1 act-
first determines that R2 is the next hop router (or the egress ing as the transit subnet, R1 is the ingress node that receives the
node in the L2 domain for the session address) and then inserts a PATH message. R1 first determines that R2 is the next hop router (or
LAN_NHOP object that specifies R2's IP address. When a DSBM the egress node in the L2 domain for the session address) and then
inserts a LAN_NHOP object that specifies R2's IP address. When a DSBM
receives a PATH message, it can now look at the address in the receives a PATH message, it can now look at the address in the
LAN_NHOP object and forward the PATH message towards the egress LAN_NHOP object and forward the PATH message towards the egress node
node after processing the PATH message. However, we expect the after processing the PATH message. However, we expect the L2 devices
(such as switches) to act as DSBMs on the path within the L2 domain
and it may not be reasonable to expect these devices to have an ARP
capability to determine the MAC address (we call it L2ADDR for Layer 2
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
L2 devices (such as switches) to act as DSBMs on the path within address) corresponding to the IP address in the LAN_NHOP object.
the L2 domain and it may not be reasonable to expect these dev-
ices to have an ARP capability to determine the MAC address (we
call it L2ADDR for Layer 2 address) corresponding to the IP
address in the LAN_NHOP object.
Therefore, we require that the LAN_NHOP information (generated by Therefore, we require that the LAN_NHOP information (generated by the
the L3 device) include both the IP address (LAN_NHOP_L3 address) L3 device) include both the IP address (LAN_NHOP_L3 address) and the
and the corresponding MAC address (LAN_NHOP_L2 address ) for the corresponding MAC address (LAN_NHOP_L2 address ) for the next L3 hop
next L3 hop over the L2 domain. The LAN_NHOP_L3 address is used over the L2 domain. The LAN_NHOP_L3 address is used by SBM protocol
by SBM protocol entities on L3 devices to forward the PATH mes- entities on L3 devices to forward the PATH message towards its desti-
sage towards its destination whereas the L2 address is used by nation whereas the L2 address is used by the SBM protocol entities on
the SBM protocol entities on L2 devices to determine how to for- L2 devices to determine how to forward the PATH message towards the L3
ward the PATH message towards the L3 NHOP (egress point from the NHOP (egress point from the L2 domain). The exact format of the
L2 domain). The exact format of the LAN_NHOP information and LAN_NHOP information and relevant objects is described later in Appen-
relevant objects is described later in Appendix B. dix B.
4.2.2.4 Similarities to Standard RSVP Message Processing
- When a DSBM receives a RSVP PATH message, it processes the PATH - When a DSBM receives a RSVP PATH message, it processes the PATH
message according to the PATH processing rules described in the message according to the PATH processing rules described in the
RSVP specification. In particular, the DSBM retrieves the IP RSVP specification. In particular, the DSBM retrieves the IP
address of the previous hop from the RSVP_HOP object in the PATH address of the previous hop from the RSVP_HOP object in the PATH
message and stores the PHOP address in its PATH state. It then message and stores the PHOP address in its PATH state. It then
forwards the PATH message with the PHOP (RSVP_HOP) object modi- forwards the PATH message with the PHOP (RSVP_HOP) object modi-
fied to reflect its own IP address (RSVP_HOP_L3 address). Thus, fied to reflect its own IP address (RSVP_HOP_L3 address). Thus,
the DSBM inserts itself as an intermediate hop in the chain of the DSBM inserts itself as an intermediate hop in the chain of
nodes in the path between two L3 nodes across the L2 domain. nodes in the path between two L3 nodes across the L2 domain.
skipping to change at page 14, line 4 skipping to change at page 14, line 49
PATH_TEAR, RESV, RESV_CONFM, RESV_TEAR, and RESV_ERR) now flow PATH_TEAR, RESV, RESV_CONFM, RESV_TEAR, and RESV_ERR) now flow
through the DSBM. In particular, a PATH_TEAR message is routed through the DSBM. In particular, a PATH_TEAR message is routed
exactly through the intermediate DSBM(s) as its corresponding exactly through the intermediate DSBM(s) as its corresponding
PATH message and the local PATH state is first cleaned up at each PATH message and the local PATH state is first cleaned up at each
intermediate hop before the PATH_TEAR message gets forwarded. intermediate hop before the PATH_TEAR message gets forwarded.
- So far, we have described how the PATH message propagates through - So far, we have described how the PATH message propagates through
the L2 domain establishing PATH state at each DSBM along the the L2 domain establishing PATH state at each DSBM along the
managed segments in the path. The layer 2 address (LAN_NHOP_L2 managed segments in the path. The layer 2 address (LAN_NHOP_L2
address) in the LAN_NHOP object should be used by the L2 devices address) in the LAN_NHOP object should be used by the L2 devices
SBM (Subnet Bandwidth Manager) November, 1998
along the path to decide how to forward the PATH message toward along the path to decide how to forward the PATH message toward
the next L3 hop. Such devices will apply the standard IEEE the next L3 hop. Such devices will apply the standard IEEE
SBM (Subnet Bandwidth Manager) March, 1999
802.1D forwarding rules (e.g., send it on a single port based on 802.1D forwarding rules (e.g., send it on a single port based on
its filtering database, or flood it on all ports active in the its filtering database, or flood it on all ports active in the
spanning tree if the L2 address does not appear in the filtering spanning tree if the L2 address does not appear in the filtering
database) to the LAN_NHOP_L2 address as are applied normally to database) to the LAN_NHOP_L2 address as are applied normally to
data packets destined to the address. data packets destined to the address.
4.2.2.5 Including Both Layer-2 and Layer-3 Addresses in the
RSVP_HOP Objects
In the conventional RSVP message processing, the PATH state esta- In the conventional RSVP message processing, the PATH state esta-
blished along the nodes on a path is used to route the RESV mes- blished along the nodes on a path is used to route the RESV message
sage from a receiver to a sender in an RSVP session. As each from a receiver to a sender in an RSVP session. As each intermediate
intermediate node builds the path state, it remembers the previ- node builds the path state, it remembers the previous hop (stores the
ous hop (stores the PHOP IP address available in the RSVP_HOP PHOP IP address available in the RSVP_HOP object of an incoming mes-
object of an incoming message) that sent it the PATH message and, sage) that sent it the PATH message and, when the RESV message
when the RESV message arrives, the intermediate node simply uses arrives, the intermediate node simply uses the stored PHOP address to
the stored PHOP address to forward the RESV after processing it forward the RESV after processing it successfully.
successfully.
In our case, we expect the SBM entities residing at L2 devices to In our case, we expect the SBM entities residing at L2 devices to act
act as DSBMs (and, therefore, intermediate RSVP hops in an L2 as DSBMs (and, therefore, intermediate RSVP hops in an L2 domain)
domain) along the path between a sender (PHOP) and receiver along the path between a sender (PHOP) and receiver (NHOP). Thus, when
(NHOP). Thus, when a RESV message arrives at a DSBM, it must use a RESV message arrives at a DSBM, it must use the stored PHOP IP
the stored PHOP IP address to forward the RESV message to its address to forward the RESV message to its previous hop. However, it
previous hop. However, it may not be reasonable to expect the L2 may not be reasonable to expect the L2 devices to have an ARP cache or
devices to have an ARP cache or the ARP capability to map the the ARP capability to map the PHOP IP address to its corresponding L2
PHOP IP address to its corresponding L2 address before forwarding address before forwarding the RESV message.
the RESV message.
To obviate the need for such address mapping at L2 devices, we To obviate the need for such address mapping at L2 devices, we use a
use a RSVP_HOP_L2 object in the PATH message. The RSVP_HOP_L2 RSVP_HOP_L2 object in the PATH message. The RSVP_HOP_L2 object
object includes the Layer 2 address (L2ADDR) of the previous hop includes the Layer 2 address (L2ADDR) of the previous hop and comple-
and complements the L3 address information included in the ments the L3 address information included in the RSVP_HOP object
RSVP_HOP object (RSVP_HOP_L3 address). (RSVP_HOP_L3 address).
When a L3 device constructs and forwards a PATH message over a When a L3 device constructs and forwards a PATH message over a managed
managed segment, it includes its IP address (IP address of the segment, it includes its IP address (IP address of the interface over
interface over which PATH is sent) in the RSVP_HOP object and add which PATH is sent) in the RSVP_HOP object and adds a RSVP_HOP_L2
a RSVP_HOP_L2 object that includes the corresponding L2 address object that includes the corresponding L2 address for the interface.
for the interface. When a device in the L2 domain receives such a When a device in the L2 domain receives such a PATH message, it
PATH message, it remembers the addresses in the RSVP_HOP and remembers the addresses in the RSVP_HOP and RSVP_HOP_L2 objects in its
RSVP_HOP_L2 objects in its PATH state and then overwrites the PATH state and then overwrites the RSVP_HOP and RSVP_HOP_L2 objects
RSVP_HOP and RSVP_HOP_L2 objects with its own addresses before with its own addresses before forwarding the PATH message over a
forwarding the PATH message over a managed segment. managed segment.
The exact format of RSVP_HOP_L2 object is specified in APPENDIX The exact format of RSVP_HOP_L2 object is specified in Appendix B.
B.
SBM (Subnet Bandwidth Manager) November, 1998 4.2.2.6 Loop Detection
- When an RSVP session address is a multicast address and a SBM, When an RSVP session address is a multicast address and a SBM, DSBM,
DSBM, and DSBM clients share the same L2 segment (a shared seg-
ment), it is possible for a SBM or a DSBM client to receive one
or more copies of a PATH message that it forwarded earlier when a
DSBM on the same wire forwards it (See Section 5.8 for an example
of such a case). To facilitate detection of such loops, we use a
new RSVP object called the LAN_LOOPBACK object. DSBM clients or
SBMs (but not the DSBMs reflecting a PATH message onto the inter-
face over which it arrived earlier) must overwrite (or add if the
PATH message does NOT already include a LAN_LOOPBACK object) the
LAN_LOOPBACK object in the PATH message with their own unicast IP
address.
Now, a SBM or a DSBM client can easily detect and discard the SBM (Subnet Bandwidth Manager) March, 1999
duplicates by checking the contents of the LAN_LOOPBACK object (a
duplicate PATH message will list a device's own interface address
in the LAN_LOOPBACK object). Appendix B specifies the exact for-
mat of the LAN_LOOPBACK object.
- The model proposed by the Integrated Services working group and DSBM clients share the same L2 segment (a shared segment), it is
requires isolation of traffic flows from each other during their possible for a SBM or a DSBM client to receive one or more copies of a
transit across a network. The motivation for traffic flow separa- PATH message that it forwarded earlier when a DSBM on the same wire
tion is to provide Integrated Services flows protection from mis- forwards it (See Section 5.8 for an example of such a case). To facil-
behaving flows and other best-effort traffic that share the same itate detection of such loops, we use a new RSVP object called the
path. The basic IEEE 802.3/Ethernet networks do not provide any LAN_LOOPBACK object. DSBM clients or SBMs (but not the DSBMs reflect-
notion of traffic classes to discriminate among different flows ing a PATH message onto the interface over which it arrived earlier)
that request different services. However, IEEE 802.1p defines a must overwrite (or add if the PATH message does NOT already include a
way for switches to differentiate among several "user_priority" LAN_LOOPBACK object) the LAN_LOOPBACK object in the PATH message with
values encoded in packets representing different traffic classes their own unicast IP address.
(see [IEEE802Q, IEEE8021p] for further details). The
user_priority values can be encoded either in native LAN packets Now, a SBM or a DSBM client can easily detect and discard the dupli-
(e.g., in IEEE 802.5's FC octet) or by using an encapsulation cates by checking the contents of the LAN_LOOPBACK object (a duplicate
above the MAC layer (e.g., in the case of Ethernet, the PATH message will list a device's own interface address in the
user_priority value assigned to each packet will be carried in LAN_LOOPBACK object). Appendix B specifies the exact format of the
the frame header using the new, extended frame format defined by LAN_LOOPBACK object.
IEEE 802.1Q [IEEE8021Q]. IEEE, however, makes no recommendations
about how a sender or network should use the user_priority 4.2.2.7 802.1p, User Priority and TCLASS
values. An accompanying document makes recommendations on the
usage of the user_priority values (see [Seaman98] for details). The model proposed by the Integrated Services working group requires
isolation of traffic flows from each other during their transit across
a network. The motivation for traffic flow separation is to provide
Integrated Services flows protection from misbehaving flows and other
best-effort traffic that share the same path. The basic IEEE
802.3/Ethernet networks do not provide any notion of traffic classes
to discriminate among different flows that request different services.
However, IEEE 802.1p defines a way for switches to differentiate among
several "user_priority" values encoded in packets representing dif-
ferent traffic classes (see [IEEE802Q, IEEE8021p] for further
details). The user_priority values can be encoded either in native LAN
packets (e.g., in IEEE 802.5's FC octet) or by using an encapsulation
above the MAC layer (e.g., in the case of Ethernet, the user_priority
value assigned to each packet will be carried in the frame header
using the new, extended frame format defined by IEEE 802.1Q
[IEEE8021Q]. IEEE, however, makes no recommendations about how a
sender or network should use the user_priority values. An accompanying
document makes recommendations on the usage of the user_priority
values (see [Seaman98] for details).
Under the Integrated Services model, L3 (or higher) entities that Under the Integrated Services model, L3 (or higher) entities that
transmit traffic flows onto a L2 segment should perform per-flow transmit traffic flows onto a L2 segment should perform per-flow pol-
policing to ensure that the flows do not exceed their traffic icing to ensure that the flows do not exceed their traffic specifica-
specification as specified during admission control. In addition, tion as specified during admission control. In addition, L3 devices
L3 devices may label the frames in such flows with a may label the frames in such flows with a user_priority value to iden-
user_priority value to identify their service class. tify their service class.
SBM (Subnet Bandwidth Manager) November, 1998 For the purpose of this discussion, we will refer to the user_priority
value carried in the extended frame header as the "traffic class" of a
For the purpose of this discussion, we will refer to the SBM (Subnet Bandwidth Manager) March, 1999
user_priority value carried in the extended frame header as a
"traffic class" of a packet. Under the ISSLL model, the L3 enti-
ties, that send traffic and that use the SBM protocol, may not
select the traffic class of outgoing packets. Instead, once a
sender sends a PATH message, downstream DSBMs will insert a new
traffic class object (TCLASS object) in the PATH message that
travels to the next L3 device (L3 NHOP for the PATH message). To
some extent, the TCLASS object contents are treated like the
ADSPEC object in the RSVP PATH messages. The L3 device that
receives the PATH message must remove and store the TCLASS object
as part of its PATH state for the session. Later, when the same
L3 device needs to forward a RSVP RESV message towards the origi-
nal sender, it must include the TCLASS object in the RESV mes-
sage. When the RESV message arrives at the original sender, it
must pass the user_priority value in the TCLASS object to its
local packet classifier (traffic control) so that subsequent,
outgoing data packets for this RSVP flow will have the
user_priority value included in the extended MAC header.
The format of the TCLASS object is specified in Appendix B. Note packet. Under the ISSLL model, the L3 entities, that send traffic and
that TCLASS and other SBM-specific objects are carried in a RSVP that use the SBM protocol, may select the appropriate traffic class of
message in addition to all the other, normal RSVP objects per RFC outgoing packets [Seaman98]. This selection may be overridden by DSBM
2205. devices, in the following manner. once a sender sends a PATH message,
downstream DSBMs will insert a new traffic class object (TCLASS
object) in the PATH message that travels to the next L3 device (L3
NHOP for the PATH message). To some extent, the TCLASS object contents
are treated like the ADSPEC object in the RSVP PATH messages. The L3
device that receives the PATH message must remove and store the TCLASS
object as part of its PATH state for the session. Later, when the same
L3 device needs to forward a RSVP RESV message towards the original
sender, it must include the TCLASS object in the RESV message. When
the RESV message arrives at the original sender, the sender must use
the user_priority value from the TCLASS object to override its selec-
tion for the traffic class marked in outgoing packets.
In summary, use of TCLASS objects requires following additions to The format of the TCLASS object is specified in Appendix B. Note that
the conventional RSVP message processing at DSBMs, SBMs, and DSBM TCLASS and other SBM-specific objects are carried in a RSVP message in
clients: addition to all the other, normal RSVP objects per RFC 2205.
4.2.2.8 Processing the TCLASS Object
In summary, use of TCLASS objects requires following additions to the
conventional RSVP message processing at DSBMs, SBMs, and DSBM clients:
* When a DSBM receives a PATH message over a managed segment and * When a DSBM receives a PATH message over a managed segment and
the PATH message does not include a TCLASS object, the DSBM the PATH message does not include a TCLASS object, the DSBM MAY
adds a TCLASS object to the PATH message before forwarding it. add a TCLASS object to the PATH message before forwarding it.
The DSBM comes up with the appropriate user_priority value for The DSBM determines the appropriate user_priority value for the
the TCLASS object according to some internal mapping of the TCLASS object. A mechanism for selecting the appropriate
service classes. One possible set of internal mappings is pro- user_priority value is described in an accompanying document
posed as an example in an accompanying document [Seaman98]. [Seaman98].
* When SBM or DSBM receives a PATH message with a TCLASS object * When SBM or DSBM receives a PATH message with a TCLASS object
over a managed segment in a L2 domain and needs to forward it over a managed segment in a L2 domain and needs to forward it
over a managed segment in the same L2 domain, it will typically over a managed segment in the same L2 domain, it will store it
forward the message without changing the contents of the TCLASS in its path state and typically forward the message without
object. However, if the DSBM/SBM cannot support the service changing the contents of the TCLASS object. However, if the
class represented by the user_priority value specified by the DSBM/SBM cannot support the service class represented by the
TCLASS object in the PATH message, it may change the priority user_priority value specified by the TCLASS object in the PATH
value in the TCLASS to a semantically "lower" service value to message, it may change the priority value in the TCLASS to a
reflect its capability. semantically "lower" service value to reflect its capability
and store the changed TCLASS value in its path state.
SBM (Subnet Bandwidth Manager) November, 1998
[NOTE: An accompanying document defines the int-serv mappings [NOTE: An accompanying document defines the int-serv mappings
SBM (Subnet Bandwidth Manager) March, 1999
over IEEE 802 networks [Seaman98] provides a precise definition over IEEE 802 networks [Seaman98] provides a precise definition
of user_priority values and describes how the user_priority of user_priority values and describes how the user_priority
values are compared to determine "lower" of the two values or values are compared to determine "lower" of the two values or
the "lowest" among all the user_priority values.] the "lowest" among all the user_priority values.]
* When a DSBM receives a RESV message with a TCLASS object, it * When a DSBM receives a RESV message with a TCLASS object, it
may use the traffic class information (in addition to the usual may use the traffic class information (in addition to the usual
flowspec information in the RSVP message) for its own admission flowspec information in the RSVP message) for its own admission
control for the managed segment. control for the managed segment.
Note that this document does not specify the actual algorithm Note that this document does not specify the actual algorithm
or policy used for admission control. At one extreme, a DSBM or policy used for admission control. At one extreme, a DSBM
may use per-flow reservation request as specified by the may use per-flow reservation request as specified by the
flowspec for a fine grain admission control. At the other flowspec for a fine grain admission control. At the other
extreme, a DSBM may only consider the traffic class information extreme, a DSBM may only consider the traffic class information
for a very coarse-grain admission control based on some static for a very coarse-grain admission control based on some static
allocation of link capacity for each traffic class. Any combi- allocation of link capacity for each traffic class. Any combi-
nation of the options represented by these two extremes may nation of the options represented by these two extremes may
also be used. also be used.
* When a DSBM (at an L2 or L3) device receives a RESV message
without a TCLASS object and it needs to forward the RESV mes-
sage over a managed segment within the same L2 domain, it
should first check its path state and check whether it has
stored a TCLASS value. If so, it should include the TCLASS
object in the outgoing RESV message after performing its own
admission control. If no TCLASS value is stored, it must for-
ward the RESV message without inserting a TCLASS object.
* When a DSBM client (residing at an L3 device such as a host or * When a DSBM client (residing at an L3 device such as a host or
an edge router) receives the TCLASS object in a PATH message an edge router) receives the TCLASS object in a PATH message
that it accepts over an interface, it should store the TCLASS that it accepts over an interface, it should store the TCLASS
object as part of its PATH state for the interface. Later, when object as part of its PATH state for the interface. Later, when
the client forwards a RESV message for the same session on the the client forwards a RESV message for the same session on the
interface, the client must include the TCLASS object (unchanged interface, the client must include the TCLASS object (unchanged
from what was received in the previous PATH message) in the from what was received in the previous PATH message) in the
RESV message it forwards over the interface. RESV message it forwards over the interface.
* When a DSBM client receives a TCLASS object in an incoming RESV * When a DSBM client receives a TCLASS object in an incoming RESV
message over a managed segment and local admission control message over a managed segment and local admission control
succeeds for the session for the outgoing interface over the succeeds for the session for the outgoing interface over the
managed segment, the client must pass the user_priority value managed segment, the client must pass the user_priority value
in the TCLASS object to its local packet classifier. This will in the TCLASS object to its local packet classifier. This will
ensure that the data packets in the admitted RSVP flow that are ensure that the data packets in the admitted RSVP flow that are
subsequently forwarded over the outgoing interface will contain subsequently forwarded over the outgoing interface will contain
SBM (Subnet Bandwidth Manager) March, 1999
the appropriate value encoded in their frame header. the appropriate value encoded in their frame header.
* When an L3 device receives a PATH or RESV message over a * When an L3 device receives a PATH or RESV message over a
managed segment in one L2 domain and it needs to forward the managed segment in one L2 domain and it needs to forward the
PATH/RESV message over an interface outside that domain, the L3 PATH/RESV message over an interface outside that domain, the L3
device must remove the TCLASS object (along with LAN_NHOP, device must remove the TCLASS object (along with LAN_NHOP,
RSVP_HOP_L2, and LAN_LOOPBACK objects in the case of the PATH RSVP_HOP_L2, and LAN_LOOPBACK objects in the case of the PATH
SBM (Subnet Bandwidth Manager) November, 1998
message) before forwarding the PATH/RESV message. If the outgo- message) before forwarding the PATH/RESV message. If the outgo-
ing interface is on a separate L2 domain, these objects may be ing interface is on a separate L2 domain, these objects may be
regenerated according to the processing rules applicable to regenerated according to the processing rules applicable to
that interface. that interface.
5. Detailed Message Processing Rules 5. Detailed Message Processing Rules
5.1. Additional Notes on Terminology 5.1. Additional Notes on Terminology
* An L2 device may have several interfaces with attached segments * An L2 device may have several interfaces with attached segments
skipping to change at page 18, line 37 skipping to change at page 20, line 4
roles simultaneously. DSBM clients always reside at L3 devices. roles simultaneously. DSBM clients always reside at L3 devices.
* A SBM protocol entity residing at a layer 2 device can be a SBM, * A SBM protocol entity residing at a layer 2 device can be a SBM,
a DSBM or none of the above (SBM transparent). A layer 2 device a DSBM or none of the above (SBM transparent). A layer 2 device
will never host a DSBM client. will never host a DSBM client.
5.2. Use Of Reserved IP Multicast Addresses 5.2. Use Of Reserved IP Multicast Addresses
As stated earlier, we require that the DSBM clients forward the RSVP As stated earlier, we require that the DSBM clients forward the RSVP
PATH messages to their DSBMs in a L2 domain before they reach the next PATH messages to their DSBMs in a L2 domain before they reach the next
SBM (Subnet Bandwidth Manager) March, 1999
L3 hop in the path. RSVP PATH messages are addressed, according to L3 hop in the path. RSVP PATH messages are addressed, according to
RFC-2205, to their destination address (which can be either an IP uni- RFC-2205, to their destination address (which can be either an IP uni-
cast or multicast address). When a L2 device hosts a DSBM, a simple- cast or multicast address). When a L2 device hosts a DSBM, a simple-
to-implement mechanism must be provided for the device to capture an to-implement mechanism must be provided for the device to capture an
incoming PATH message and hand it over to the local DSBM agent without incoming PATH message and hand it over to the local DSBM agent without
requiring the L2 device to snoop for L3 RSVP messages. requiring the L2 device to snoop for L3 RSVP messages.
In addition, DSBM clients need to know how to address SBM messages to In addition, DSBM clients need to know how to address SBM messages to
SBM (Subnet Bandwidth Manager) November, 1998
the DSBM. For the ease of operation and to allow dynamic DSBM-client the DSBM. For the ease of operation and to allow dynamic DSBM-client
binding, it should be possible to easily detect and address the exist- binding, it should be possible to easily detect and address the exist-
ing DSBM on a managed segment. ing DSBM on a managed segment.
To facilitate dynamic DSBM-client binding as well as to enable easy To facilitate dynamic DSBM-client binding as well as to enable easy
detection and capture of PATH messages at L2 devices, we require that detection and capture of PATH messages at L2 devices, we require that
a DSBM be addressed using a logical address rather than a physical a DSBM be addressed using a logical address rather than a physical
address. We make use of reserved IP multicast address(es) for the pur- address. We make use of reserved IP multicast address(es) for the pur-
pose of communication with a DSBM. In particular, we require that pose of communication with a DSBM. In particular, we require that
when a DSBM client or a SBM forwards a PATH message over a managed when a DSBM client or a SBM forwards a PATH message over a managed
skipping to change at page 19, line 43 skipping to change at page 21, line 5
We define use of two reserved IP multicast addresses. We call these We define use of two reserved IP multicast addresses. We call these
the "AllSBM Address" and the "DSBMLogicalAddress". These are chosen the "AllSBM Address" and the "DSBMLogicalAddress". These are chosen
from the range of local multicast addresses, such that: from the range of local multicast addresses, such that:
* They are not passed through layer 3 devices. * They are not passed through layer 3 devices.
* They are passed transparently through layer 2 devices which are * They are passed transparently through layer 2 devices which are
SBM transparent. SBM transparent.
SBM (Subnet Bandwidth Manager) March, 1999
* They are configured in the permanent database of layer 2 devices * They are configured in the permanent database of layer 2 devices
which host SBMs or DSBMs, such that they are directed to the SBM which host SBMs or DSBMs, such that they are directed to the SBM
management entity in these devices. This obviates the need for management entity in these devices. This obviates the need for
these devices to explicitly snoop for SBM related control pack- these devices to explicitly snoop for SBM related control pack-
ets. ets.
* The two reserved addresses are 224.0.0.16 (DSBMLogicalAddress) * The two reserved addresses are 224.0.0.16 (DSBMLogicalAddress)
SBM (Subnet Bandwidth Manager) November, 1998
and 224.0.0.17 (AllSBMAddress). and 224.0.0.17 (AllSBMAddress).
These addresses are used as described in the following table: These addresses are used as described in the following table:
Type DSBMLogicaladdress AllSBMAddress Type DSBMLogicaladdress AllSBMAddress
DSBM * Sends PATH messages * Monitors this address to detect DSBM * Sends PATH messages * Monitors this address to detect
Client to this address the presence of a DSBM Client to this address the presence of a DSBM
* Monitors this address to * Monitors this address to
receive PATH messages receive PATH messages
skipping to change at page 20, line 45 skipping to change at page 22, line 5
additional details. additional details.
5.3. Layer 3 to Layer 2 Address Mapping 5.3. Layer 3 to Layer 2 Address Mapping
As stated earlier, DSBMs or DSBM clients residing at a L3 device must As stated earlier, DSBMs or DSBM clients residing at a L3 device must
include a LAN_NHOP_L2 address in the LAN_NHOP information so that L2 include a LAN_NHOP_L2 address in the LAN_NHOP information so that L2
devices along the path of a PATH message do not need to separately devices along the path of a PATH message do not need to separately
determine the mapping between the LAN_NHOP_L3 address in the LAN_NHOP determine the mapping between the LAN_NHOP_L3 address in the LAN_NHOP
object and its corresponding L2 address (for example, using ARP). object and its corresponding L2 address (for example, using ARP).
SBM (Subnet Bandwidth Manager) March, 1999
For the purpose of such mapping at L3 devices, we assume a mapping For the purpose of such mapping at L3 devices, we assume a mapping
function called "map_address" that performs the necessary mapping: function called "map_address" that performs the necessary mapping:
L2ADDR object = map_addr(L3Addr) L2ADDR object = map_addr(L3Addr)
We do not specify how the function is implemented; the implementation We do not specify how the function is implemented; the implementation
may simply involve access to the local ARP cache entry or may require may simply involve access to the local ARP cache entry or may require
performing an ARP function. The function returns a L2ADDR object that performing an ARP function. The function returns a L2ADDR object that
SBM (Subnet Bandwidth Manager) November, 1998
need not be interpreted by an L3 device and can be treated as an need not be interpreted by an L3 device and can be treated as an
opaque object. The format of the L2ADDR object is specified in Appen- opaque object. The format of the L2ADDR object is specified in Appen-
dix B. dix B.
5.4. Raw vs. UDP Encapsulation 5.4. Raw vs. UDP Encapsulation
We assume that the DSBMs, DSBM clients, and SBMs use only raw IP for We assume that the DSBMs, DSBM clients, and SBMs use only raw IP for
encapsulating RSVP messages that are forwarded onto a L2 domain. encapsulating RSVP messages that are forwarded onto a L2 domain.
Thus, when a SBM protocol entity on a L3 device forwards a RSVP mes- Thus, when a SBM protocol entity on a L3 device forwards a RSVP mes-
sage onto a L2 segment, it will only use RAW IP encapsulation. sage onto a L2 segment, it will only use RAW IP encapsulation.
5.5. The Forwarding Rules 5.5. The Forwarding Rules
The message processing and forwarding rules will be described in the The message processing and forwarding rules will be described in the
context of the sample network illustrated in Figure 2. context of the sample network illustrated in Figure 2.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
Figure 2 - A sample network or L2 domain consisting of switched and Figure 2 - A sample network or L2 domain consisting of switched and
shared L2 segments shared L2 segments
.......... ..........
. .
+------+ . +------+ seg A +------+ seg C +------+ seg D +------+ +------+ . +------+ seg A +------+ seg C +------+ seg D +------+
| H1 |_______| R1 |_________| S1 |_________| S2 |_________| H2 | | H1 |_______| R1 |_________| S1 |_________| S2 |_________| H2 |
| | . | | | | | | | | | | . | | | | | | | |
+------+ . +------+ +------+ +------+ +------+ +------+ . +------+ +------+ +------+ +------+
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and a shared L2 segment. The sample network contains the following and a shared L2 segment. The sample network contains the following
devices: devices:
Device Type SBM Type Device Type SBM Type
H1, H5 Host (layer 3) SBM Transparent H1, H5 Host (layer 3) SBM Transparent
H2-H4 Host (layer 3) DSBM Client H2-H4 Host (layer 3) DSBM Client
R1 Router (layer 3) SBM R1 Router (layer 3) SBM
R2 Router (layer 3) DSBM for segment F R2 Router (layer 3) DSBM for segment F
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
S1 Switch (layer 2) DSBM for segments A, B S1 Switch (layer 2) DSBM for segments A, B
S2 Switch (layer 2) DSBM for segments C, D, E S2 Switch (layer 2) DSBM for segments C, D, E
S3 Switch (layer 2) SBM S3 Switch (layer 2) SBM
The following paragraphs describe the rules, which each of these dev- The following paragraphs describe the rules, which each of these dev-
ices should use to forward PATH messages (rules apply to PATH_TEAR ices should use to forward PATH messages (rules apply to PATH_TEAR
messages as well). They are described in the context of the general messages as well). They are described in the context of the general
network illustrated above. While the examples do not address every network illustrated above. While the examples do not address every
scenario, they do address most of the interesting scenarios. Excep- scenario, they do address most of the interesting scenarios. Excep-
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* If the device is a layer 3 device, determine whether the inter- * If the device is a layer 3 device, determine whether the inter-
face is on a managed segment managed by a DSBM, based on the face is on a managed segment managed by a DSBM, based on the
presence or absence of I_AM_DSBM messages. If the interface is presence or absence of I_AM_DSBM messages. If the interface is
not on a managed segment, strip out RSVP_HOP_L2, LAN_NHOP, not on a managed segment, strip out RSVP_HOP_L2, LAN_NHOP,
LAN_LOOPBACK, and TCLASS objects (if present), and forward to LAN_LOOPBACK, and TCLASS objects (if present), and forward to
the unicast or multicast destination. the unicast or multicast destination.
(Note that the RSVP Class Numbers for these new objects are (Note that the RSVP Class Numbers for these new objects are
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
chosen so that if an RSVP message includes these objects, the chosen so that if an RSVP message includes these objects, the
nodes that are RSVP-aware, but do not participate in the SBM nodes that are RSVP-aware, but do not participate in the SBM
protocol, will ignore and silently discard such objects.) protocol, will ignore and silently discard such objects.)
* If the device is a layer 2 device or it is a layer 3 device * If the device is a layer 2 device or it is a layer 3 device
*and* the interface is on a managed segment, proceed to rule *and* the interface is on a managed segment, proceed to rule
#3. #3.
3. Forward the PATH message onto the managed segment: 3. Forward the PATH message onto the managed segment:
skipping to change at page 25, line 5 skipping to change at page 26, line 5
ices must also have IP addresses) into the standard RSVP HOP ices must also have IP addresses) into the standard RSVP HOP
object and the L2 address of the forwarding interface into object and the L2 address of the forwarding interface into
the RSVP_HOP_L2 object. the RSVP_HOP_L2 object.
- If the PATH message received does not contain the TCLASS - If the PATH message received does not contain the TCLASS
object, insert a TCLASS object. The user_priority value object, insert a TCLASS object. The user_priority value
inserted in the TCLASS object is based on service mappings inserted in the TCLASS object is based on service mappings
internal to the device that are configured according to the internal to the device that are configured according to the
guidelines listed in [Seaman98]. If the message already guidelines listed in [Seaman98]. If the message already
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
contains the TCLASS object, the user_priority value may be contains the TCLASS object, the user_priority value may be
changed based again on the service mappings internal to the changed based again on the service mappings internal to the
device. device.
* If the device is a layer 3 device and hosts a SBM for the seg- * If the device is a layer 3 device and hosts a SBM for the seg-
ment to which the forwarding interface is attached, it *is ment to which the forwarding interface is attached, it *is
required* to retrieve and store the PHOP info. required* to retrieve and store the PHOP info.
If the device is a layer 2 device and hosts a SBM for the seg- If the device is a layer 2 device and hosts a SBM for the seg-
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* If the SBM protocol entity is the DSBM for the segment to which * If the SBM protocol entity is the DSBM for the segment to which
the forwarding interface is attached, it must send the PATH the forwarding interface is attached, it must send the PATH
message to the AllSBMAddress. message to the AllSBMAddress.
* If the SBM protocol entity is a SBM or a DSBM Client on the * If the SBM protocol entity is a SBM or a DSBM Client on the
segment to which the forwarding interface is attached, it must segment to which the forwarding interface is attached, it must
send the PATH message to the DSBMLogicalAddress. send the PATH message to the DSBMLogicalAddress.
5.6.1. Additional notes on forwarding a PATH message onto a 5.6.1. Additional notes on forwarding a PATH message onto a
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
managed segment managed segment
Rule #1 states that normal IEEE 802.1D forwarding rules should be Rule #1 states that normal IEEE 802.1D forwarding rules should be
used to determine the interfaces on which the PATH message should used to determine the interfaces on which the PATH message should
be forwarded. In the case of data packets, standard forwarding be forwarded. In the case of data packets, standard forwarding
rules at a L2 device dictate that the packet should not be for- rules at a L2 device dictate that the packet should not be for-
warded on the interface from which it was received. However, in warded on the interface from which it was received. However, in
the case of a DSBM that receives a PATH message over a managed the case of a DSBM that receives a PATH message over a managed
segment, the following exception applies: segment, the following exception applies:
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LAN_LOOPBACK object addresses this issue. All SBM protocol enti- LAN_LOOPBACK object addresses this issue. All SBM protocol enti-
ties (except DSBMs reflecting a PATH message) overwrite the ties (except DSBMs reflecting a PATH message) overwrite the
LAN_LOOPBACK object in the PATH message with the IP address of LAN_LOOPBACK object in the PATH message with the IP address of
the outgoing interface. DSBMs which are reflecting a PATH mes- the outgoing interface. DSBMs which are reflecting a PATH mes-
sage, leave the LAN_LOOPBACK object unchanged. Thus, SBM proto- sage, leave the LAN_LOOPBACK object unchanged. Thus, SBM proto-
col entities will always be able to recognize a reflected multi- col entities will always be able to recognize a reflected multi-
cast message by the presence of their own address in the cast message by the presence of their own address in the
LAN_LOOPBACK object. These messages should be silently dis- LAN_LOOPBACK object. These messages should be silently dis-
carded. carded.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
5.7. Applying the Rules -- Unicast Session 5.7. Applying the Rules -- Unicast Session
Let's see how the rules are applied in the general network illus- Let's see how the rules are applied in the general network illus-
trated previously (see Figure 2). trated previously (see Figure 2).
Assume that H1 is sending a PATH for a unicast session for which Assume that H1 is sending a PATH for a unicast session for which
H5 is the receiver. The following PATH message is composed by H1: H5 is the receiver. The following PATH message is composed by H1:
RSVP Contents RSVP Contents
skipping to change at page 28, line 5 skipping to change at page 29, line 5
PHOP IP address of R1 (2.0.0.1) PHOP IP address of R1 (2.0.0.1)
(seed the return path for RESV messages) (seed the return path for RESV messages)
RSVP_HOP_L2 L2 address of R1 RSVP_HOP_L2 L2 address of R1
LAN_NHOP LAN_NHOP_L3 (2.0.0.2) and LAN_NHOP LAN_NHOP_L3 (2.0.0.2) and
LAN_NHOP_L2 address of R2 (L2ADDR) LAN_NHOP_L2 address of R2 (L2ADDR)
(this is the next layer 3 hop) (this is the next layer 3 hop)
LAN_LOOPBACK IP address of R1 (2.0.0.1) LAN_LOOPBACK IP address of R1 (2.0.0.1)
IP Header IP Header
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
Source address IP address of H1 Source address IP address of H1
Destn address DSBMLogical IP address (224.0.0.16) Destn address DSBMLogical IP address (224.0.0.16)
MAC Header MAC Header
Destn address DSBMLogical MAC address Destn address DSBMLogical MAC address
* R1 does a routing lookup on the RSVP session address, to * R1 does a routing lookup on the RSVP session address, to
determine the IP address of the next layer 3 hop, R2. determine the IP address of the next layer 3 hop, R2.
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RSVP_HOP_L2 L2 address of S1 RSVP_HOP_L2 L2 address of S1
LAN_NHOP LAN_NHOP_L3 (IP) and LAN_NHOP_L2 LAN_NHOP LAN_NHOP_L3 (IP) and LAN_NHOP_L2
address of R2 address of R2
(layer 2 devices do not modify the LAN_NHOP) (layer 2 devices do not modify the LAN_NHOP)
LAN_LOOPBACK IP addr of S1 LAN_LOOPBACK IP addr of S1
IP Header IP Header
Source address IP address of H1 Source address IP address of H1
Destn address AllSBMIPaddr (224.0.0.17, since S1 is the Destn address AllSBMIPaddr (224.0.0.17, since S1 is the
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
DSBM for seg B). DSBM for seg B).
MAC Header MAC Header
Destn address All SBM MAC address (since S1 is the DSBM for Destn address All SBM MAC address (since S1 is the DSBM for
seg B). seg B).
* S1 looks at the LAN_NHOP address information to determine the * S1 looks at the LAN_NHOP address information to determine the
L2 address towards which it should forward the PATH message. L2 address towards which it should forward the PATH message.
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LAN_LOOPBACK IP address of S3 LAN_LOOPBACK IP address of S3
IP Header IP Header
Source address IP address of H1 Source address IP address of H1
Destn address DSBMLogical IP addr (since S3 is Destn address DSBMLogical IP addr (since S3 is
not the DSBM for seg F) not the DSBM for seg F)
MAC Header MAC Header
Destn address DSBMLogical MAC address Destn address DSBMLogical MAC address
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
* S3 looks at the LAN_NHOP address information to determine the * S3 looks at the LAN_NHOP address information to determine the
L2 address towards which it should forward the PATH message. L2 address towards which it should forward the PATH message.
* From the bridge forwarding tables, it determines that the L2 * From the bridge forwarding tables, it determines that the L2
address is reachable via segment F. address is reachable via segment F.
* It has discovered that R2 is the DSBM for segment F. It * It has discovered that R2 is the DSBM for segment F. It
therefore sends the PATH message to the DSBMLogicalAddress. therefore sends the PATH message to the DSBMLogicalAddress.
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MAC Header MAC Header
Destn address L2 addr corresponding to H5, the next Destn address L2 addr corresponding to H5, the next
layer 3 hop layer 3 hop
* R2 does a routing lookup on the RSVP session address, to * R2 does a routing lookup on the RSVP session address, to
determine the IP address of the next layer 3 hop, H5. determine the IP address of the next layer 3 hop, H5.
* It determines that H5 is accessible via a segment for which * It determines that H5 is accessible via a segment for which
there is no DSBM (not a managed segment). there is no DSBM (not a managed segment).
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
* Therefore, it removes the LAN_NHOP and RSVP_HOP_L2 objects * Therefore, it removes the LAN_NHOP and RSVP_HOP_L2 objects
and places the RSVP session address in the destination and places the RSVP session address in the destination
address of the IP header. It places the L2 address of the address of the IP header. It places the L2 address of the
next layer 3 hop, into the destination address of the MAC next layer 3 hop, into the destination address of the MAC
header and forwards the PATH message to H5. header and forwards the PATH message to H5.
5.8. Applying the Rules - Multicast Session 5.8. Applying the Rules - Multicast Session
The rules described above also apply to multicast (m/c) sessions. The rules described above also apply to multicast (m/c) sessions.
skipping to change at page 32, line 5 skipping to change at page 33, line 5
PHOP IP addr of R2 (seed the return path for PHOP IP addr of R2 (seed the return path for
RESV messages) RESV messages)
RSVP_HOP_L2 L2 addr of R2 RSVP_HOP_L2 L2 addr of R2
LAN_NHOP m/c session address and corresponding L2 address LAN_NHOP m/c session address and corresponding L2 address
LAN_LOOPBACK IP addr of S3 (DSBMs reflecting a PATH LAN_LOOPBACK IP addr of S3 (DSBMs reflecting a PATH
message don't modify this object) message don't modify this object)
IP Header IP Header
Source address IP address of H1 Source address IP address of H1
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
Destn address AllSBMIP address (since R2 is the DSBM for seg F) Destn address AllSBMIP address (since R2 is the DSBM for seg F)
MAC Header MAC Header
Destn address AllSBMMAC address (since R2 is the Destn address AllSBMMAC address (since R2 is the
DSBM for seg F) DSBM for seg F)
Since H3 is monitoring the All SBM Address, it will receive the Since H3 is monitoring the All SBM Address, it will receive the
PATH message reflected by R2. Note that R2 violated the standard PATH message reflected by R2. Note that R2 violated the standard
forwarding rules here by sending an incoming message back onto the forwarding rules here by sending an incoming message back onto the
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* R2 determines that there is an m/c receiver accessible via a * R2 determines that there is an m/c receiver accessible via a
segment for which there is no DSBM. Therefore, it removes the segment for which there is no DSBM. Therefore, it removes the
LAN_NHOP and RSVP_HOP_L2 objects and places the RSVP session LAN_NHOP and RSVP_HOP_L2 objects and places the RSVP session
address in the destination address of the IP header. It address in the destination address of the IP header. It
places the corresponding L2 address into the destination places the corresponding L2 address into the destination
address of the MAC header and multicasts the message towards address of the MAC header and multicasts the message towards
H5. H5.
5.9. Merging Traffic Class objects 5.9. Merging Traffic Class objects
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
When a DSBM client receives TCLASS objects from different senders When a DSBM client receives TCLASS objects from different senders
(different PATH messages) in the same RSVP session and needs to (different PATH messages) in the same RSVP session and needs to
combine them for sending back a single RESV message (as in a combine them for sending back a single RESV message (as in a
wild-card style reservation), the DSBM client must choose an wild-card style reservation), the DSBM client must choose an
appropriate value that corresponds to the desired-delay traffic appropriate value that corresponds to the desired-delay traffic
class. An accompanying document discusses the guidelines for class. An accompanying document discusses the guidelines for
traffic class selection based on desired service and the TSpec traffic class selection based on desired service and the TSpec
information [Seaman98]. information [Seaman98].
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(or SBM) with a successful admission control done for the TCLASS (or SBM) with a successful admission control done for the TCLASS
requested in the first RESV for the flow. If another RESV (not the requested in the first RESV for the flow. If another RESV (not the
refresh of the previously admitted RESV) for the same flow arrives refresh of the previously admitted RESV) for the same flow arrives
at the DSBM, the DSBM must first check the TCLASS value in the new at the DSBM, the DSBM must first check the TCLASS value in the new
RESV against the TCLASS value in the already installed RESV. If RESV against the TCLASS value in the already installed RESV. If
the two values are same, the RESV requests are merged and the new, the two values are same, the RESV requests are merged and the new,
merged RESV installed and forwarded using the normal rules of mes- merged RESV installed and forwarded using the normal rules of mes-
sage processing. However, if the two values are not identical, the sage processing. However, if the two values are not identical, the
DSBM must generate and send a RESV_ERR message towards the sender DSBM must generate and send a RESV_ERR message towards the sender
(NHOP) of the newer, RESV message. The RESV_ERR must specify the (NHOP) of the newer, RESV message. The RESV_ERR must specify the
error code corrsponding to the RSVP "traffic control error" error code corresponding to the RSVP "traffic control error"
(RESV_ERR code 21) that indicates failure to merge two incompati- (RESV_ERR code 21) that indicates failure to merge two incompati-
ble service requests (sub-code 01 for the RSVP traffic control ble service requests (sub-code 01 for the RSVP traffic control
error) [RFC-2205]. error) [RFC-2205]. The RESV_ERR message may include additional
objects to assist downstream nodes in recovering from this condi-
tion. The definition and usage of such objects is beyond the
scope of this draft.
5.10. Operation of SBM Transparent Devices 5.10. Operation of SBM Transparent Devices
We previously defined SBM Transparent devices. Since no SBM tran-
sparent devices were illustrated in the example provided, we will
describe the operation of these in the following paragraph.
SBM transparent devices are unaware of the entire SBM/DSBM proto- SBM transparent devices are unaware of the entire SBM/DSBM proto-
col. They do not intercept messages addressed to either of the SBM col. They do not intercept messages addressed to either of the SBM
related local group addresses (the DSBMLogicalAddrss and the related local group addresses (the DSBMLogicalAddrss and the
ALLSBMAddress), but instead, pass them through. As a result, they ALLSBMAddress), but instead, pass them through. As a result, they
do not divide the DSBM election scope, they do not explicitly par- do not divide the DSBM election scope, they do not explicitly par-
ticipate in routing of PATH or RESV messages, and they do not par- ticipate in routing of PATH or RESV messages, and they do not par-
ticipate in admission control. They are entirely transparent with ticipate in admission control. They are entirely transparent with
respect to SBM operation. respect to SBM operation.
According to the definitions provided, physical segments intercon- According to the definitions provided, physical segments intercon-
nected by SBM transparent devices are considered a single managed nected by SBM transparent devices are considered a single managed
segment. Therefore, DSBMs must perform admission control on such segment. Therefore, DSBMs must perform admission control on such
managed segments, with limited knowledge of the segment's managed segments, with limited knowledge of the segment's topol-
ogy. In this case, the network administrator should configure the
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
topology. In this case, the network administrator should configure DSBM for each managed segment, with some reasonable approximation
the DSBM for each managed segment, with some reasonable approxima- of the segment's capacity. A conservative policy would configure
tion of the segment's capacity. A conservative policy would con- the DSBM for the lowest capacity route through the managed seg-
figure the DSBM for the lowest capacity route through the managed ment. A liberal policy would configure the DSBM for the highest
segment. A liberal policy would configure the DSBM for the highest
capacity route through the managed segment. A network administra- capacity route through the managed segment. A network administra-
tor will likely choose some value between the two, based on the tor will likely choose some value between the two, based on the
level of guarantee required and some knowledge of likely traffic level of guarantee required and some knowledge of likely traffic
patterns. patterns.
This document does not specify the configuration mechanism or the This document does not specify the configuration mechanism or the
choice of a policy. choice of a policy.
5.11. Operation of SBMs Which are NOT DSBMs 5.11. Operation of SBMs Which are NOT DSBMs
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passive in the background for fault tolerance. They listen to the passive in the background for fault tolerance. They listen to the
periodic announcements from the current DSBM for the managed seg- periodic announcements from the current DSBM for the managed seg-
ment (Appendix A describes this in more detail) and step in to ment (Appendix A describes this in more detail) and step in to
elect a new DSBM when the current DSBM fails or ceases to be elect a new DSBM when the current DSBM fails or ceases to be
operational for some reason. Second, such SBMs also provide the operational for some reason. Second, such SBMs also provide the
important service of dividing the election scope and reducing the important service of dividing the election scope and reducing the
size and complexity of managed segments. For example, consider the size and complexity of managed segments. For example, consider the
sample topology in Figure 3 again. the device S3 contains an SBM sample topology in Figure 3 again. the device S3 contains an SBM
that is not a DSBM for any f the segments, B, E, or F, attached to that is not a DSBM for any f the segments, B, E, or F, attached to
it. However, if the SBM protocol entity on S3 was not present, it. However, if the SBM protocol entity on S3 was not present,
ssegments B and F would not be separate segments from the point of segments B and F would not be separate segments from the point of
view of the SBM protocol. Instead, they would constitute a single view of the SBM protocol. Instead, they would constitute a single
managed segment, managed by a single DSBM. Because the SBM entity managed segment, managed by a single DSBM. Because the SBM entity
on S3 divides the election scope, seg B and seg F are each on S3 divides the election scope, seg B and seg F are each
managed by separate DSBMs. Each of these segments have a trivial managed by separate DSBMs. Each of these segments have a trivial
topology and a well defined capacity. As a result, the DSBMs for topology and a well defined capacity. As a result, the DSBMs for
these segments do not need to perform admission control based on these segments do not need to perform admission control based on
approximations (as would be the case if S3 were SBM transparent). approximations (as would be the case if S3 were SBM transparent).
Note that, SBM protocol entities which are not DSBMs, are not Note that, SBM protocol entities which are not DSBMs, are not
required to overwrite the PHOP in incident PATH messages with required to overwrite the PHOP in incident PATH messages with
their own address. This is because it is not necessary for RESV their own address. This is because it is not necessary for RESV
messages to be routed through these devices. RESV messages are messages to be routed through these devices. RESV messages are
only required to be routed through the correct sequence of DSBMs. only required to be routed through the correct sequence of DSBMs.
SBMs may not process RESV messages that do pass through them, SBMs may not process RESV messages that do pass through them,
other than to forward them towards their destination address, other than to forward them towards their destination address,
using standard forwarding rules. using standard forwarding rules.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
SBM protocol entities which are not DSBMs are required to SBM protocol entities which are not DSBMs are required to
overwrite the address in the LAN_LOOPBACK object with their own overwrite the address in the LAN_LOOPBACK object with their own
address, in order to avoid looping multicast messages. However, no address, in order to avoid looping multicast messages. However, no
state need be stored. state need be stored.
6. Inter-Operability Considerations 6. Inter-Operability Considerations
There are a few interesting inter-operability issues related to There are a few interesting inter-operability issues related to
the deployment of a DSBM-based admission control method in an the deployment of a DSBM-based admission control method in an
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6.2. An L2 domain with SBM-transparent L2 Devices. 6.2. An L2 domain with SBM-transparent L2 Devices.
This scenario has been addressed earlier in the document. The This scenario has been addressed earlier in the document. The
SBM-based method is designed to operate in such an environment. SBM-based method is designed to operate in such an environment.
When SBM-transparent L2 devices interconnect SBM-aware devices, When SBM-transparent L2 devices interconnect SBM-aware devices,
the resulting managed segment is a combination of one or more phy- the resulting managed segment is a combination of one or more phy-
sical segments and the DSBM for the managed segment may not be as sical segments and the DSBM for the managed segment may not be as
efficient in allocating resources as it would if all L2 devices efficient in allocating resources as it would if all L2 devices
were SBM-aware. were SBM-aware.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
6.3. An L2 domain on which some RSVP-based senders are not DSBM 6.3. An L2 domain on which some RSVP-based senders are not DSBM
clients. clients.
All senders that are sourcing RSVP-based traffic flows onto a All senders that are sourcing RSVP-based traffic flows onto a
managed segment MUST be SBM-aware and participate in the SBM pro- managed segment MUST be SBM-aware and participate in the SBM pro-
tocol. Use of the standard, non-SBM version of RSVP may result in tocol. Use of the standard, non-SBM version of RSVP may result in
over-allocation of resources, as such use bypasses the resource over-allocation of resources, as such use bypasses the resource
management function of the DSBM. All other senders (i.e., senders management function of the DSBM. All other senders (i.e., senders
that are not sending streams subject to RSVP admission control) that are not sending streams subject to RSVP admission control)
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This document stipulates that DSBMs, DSBM clients, and SBMs use This document stipulates that DSBMs, DSBM clients, and SBMs use
only raw IP for encapsulating RSVP messages that are forwarded only raw IP for encapsulating RSVP messages that are forwarded
onto a L2 domain. RFC-2205 (the RSVP Proposed Standard) includes onto a L2 domain. RFC-2205 (the RSVP Proposed Standard) includes
support for both raw IP and UDP encapsulation. Thus, a RSVP node support for both raw IP and UDP encapsulation. Thus, a RSVP node
using only the UDP encapsulation will not be able to interoperate using only the UDP encapsulation will not be able to interoperate
with the DSBM unless DSBM accepts and supports UDP encapsulated with the DSBM unless DSBM accepts and supports UDP encapsulated
RSVP messages. RSVP messages.
7. Guidelines for Implementors 7. Guidelines for Implementors
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
In the following, we provide guidelines for implementors on dif- In the following, we provide guidelines for implementors on dif-
ferent aspects of the implementation of the SBM-based admission ferent aspects of the implementation of the SBM-based admission
control procedure including suggestions for DSBM initialization, control procedure including suggestions for DSBM initialization,
etc. etc.
7.1. DSBM Initialization 7.1. DSBM Initialization
As stated earlier, DSBM initialization includes configuration of As stated earlier, DSBM initialization includes configuration of
maximum bandwidth that can be reserved on a managed segment under maximum bandwidth that can be reserved on a managed segment under
skipping to change at page 38, line 5 skipping to change at page 39, line 5
This configuration compromises the efficiency with which the DSBM This configuration compromises the efficiency with which the DSBM
can allocate resources. This is because the single DSBM is can allocate resources. This is because the single DSBM is
required to make admission control decisions for all reservation required to make admission control decisions for all reservation
requests within the L2 topology, with no knowledge of the actual requests within the L2 topology, with no knowledge of the actual
physical segments affected by the reservation. physical segments affected by the reservation.
We can realize improvements in the efficiency of resource alloca- We can realize improvements in the efficiency of resource alloca-
tion by subdividing the complex segment into a number of managed tion by subdividing the complex segment into a number of managed
segments, each managed by their own DSBM. In this case, each DSBM segments, each managed by their own DSBM. In this case, each DSBM
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
manages a managed segment having a relatively simple topology. manages a managed segment having a relatively simple topology.
Since managed segments are simpler, the DSBM can be configured Since managed segments are simpler, the DSBM can be configured
with a more accurate estimate of the resources available for all with a more accurate estimate of the resources available for all
reservations in the managed segment. In the ultimate configura- reservations in the managed segment. In the ultimate configura-
tion, each physical segment is a managed segment and is managed by tion, each physical segment is a managed segment and is managed by
its own DSBM. We make no assumption about the number of managed its own DSBM. We make no assumption about the number of managed
segments but state, simply, that in complex L2 topologies, the segments but state, simply, that in complex L2 topologies, the
efficiency of resource allocation improves as the granularity of efficiency of resource allocation improves as the granularity of
managed segments increases. managed segments increases.
skipping to change at page 39, line 5 skipping to change at page 40, line 5
described here. A SBM implementation should satisfy these require- described here. A SBM implementation should satisfy these require-
ments and provide the suggested mechanisms just as though it were ments and provide the suggested mechanisms just as though it were
a conventional RSVP implementation and also protect the addi- a conventional RSVP implementation and also protect the addi-
tional, SBM-specific objects in a message. tional, SBM-specific objects in a message.
In addition, it is also necessary to authenticate DSBM candidates In addition, it is also necessary to authenticate DSBM candidates
during the election process, and a mechanism based on a shared during the election process, and a mechanism based on a shared
secret among the DSBM candidates may be used. The mechanism secret among the DSBM candidates may be used. The mechanism
defined in [Baker97] should be used. defined in [Baker97] should be used.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
9. References 9. References
[RFC-2205] R. Braden, L. Zhang, S. Berson, S. Herzog, S. Jamin, [RFC-2205] R. Braden, L. Zhang, S. Berson, S. Herzog, S. Jamin,
"Resource ReSerVation Protocol (RSVP) -- Version 1 Functional "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional
Specification ", RFC-2205, September 1997. Specification ", RFC-2205, September 1997.
[Baker97] F. Baker., "RSVP Cryptographic Authentication", draft- [Baker97] F. Baker., "RSVP Cryptographic Authentication", draft-
ietf-rsvp-md5-05.txt, August 1997. ietf-rsvp-md5-05.txt, August 1997.
skipping to change at page 40, line 5 skipping to change at page 41, line 5
works: Virtual Bridged Local Area Networks", Draft Standard works: Virtual Bridged Local Area Networks", Draft Standard
P802.1Q/D9, February 20, 1998. P802.1Q/D9, February 20, 1998.
[IEEEP8021p] "Information technology - Telecommunications and [IEEEP8021p] "Information technology - Telecommunications and
information exchange between systems - Local and metropolitan area information exchange between systems - Local and metropolitan area
networks - Common specifications - Part 3: Media Access Control networks - Common specifications - Part 3: Media Access Control
(MAC) Bridges: Revision (Incorporating IEEE P802.1p: Traffic (MAC) Bridges: Revision (Incorporating IEEE P802.1p: Traffic
Class Expediting and Dynamic Multicast Filtering)", ISO/IEC Final Class Expediting and Dynamic Multicast Filtering)", ISO/IEC Final
CD 15802-3 IEEE P802.1D/D15, November 24, 1997. CD 15802-3 IEEE P802.1D/D15, November 24, 1997.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
[IEEE8021D] "MAC Bridges", ISO/IEC 10038, ANSI/IEEE Std 802.1D- [IEEE8021D] "MAC Bridges", ISO/IEC 10038, ANSI/IEEE Std 802.1D-
1993. 1993.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
APPENDIX A Appendix A
DSBM Election Algorithm DSBM Election Algorithm
A.1. Introduction A.1. Introduction
To simplify the rest of this discussion, we will assume that there To simplify the rest of this discussion, we will assume that there
is a single DSBM for the entire L2 domain (i.e., assume a shared is a single DSBM for the entire L2 domain (i.e., assume a shared
L2 segment for the entire L2 domain). Later, we will discuss how a L2 segment for the entire L2 domain). Later, we will discuss how a
DSBM is elected for a half-duplex or full-duplex switched segment. DSBM is elected for a half-duplex or full-duplex switched segment.
To allow for quick recovery from the failure of a DSBM, we assume To allow for quick recovery from the failure of a DSBM, we assume
skipping to change at page 42, line 5 skipping to change at page 43, line 5
failure of a DSBM, it waits for a subsequent I_AM_DSBM advertise- failure of a DSBM, it waits for a subsequent I_AM_DSBM advertise-
ment before resuming any communication with the DSBM. During the ment before resuming any communication with the DSBM. During the
period when a DSBM is not present, a DSBM client may forward out- period when a DSBM is not present, a DSBM client may forward out-
going PATH messages using the standard RSVP forwarding rules. going PATH messages using the standard RSVP forwarding rules.
The exact message formats and addresses used for communication The exact message formats and addresses used for communication
with (and among) SBM(s) are described in Appendix B. with (and among) SBM(s) are described in Appendix B.
A.2. Overview of the DSBM Election Procedure A.2. Overview of the DSBM Election Procedure
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
When a SBM first starts up, it listens for incoming DSBM adver- When a SBM first starts up, it listens for incoming DSBM adver-
tisements for some period to check whether a DSBM already exists tisements for some period to check whether a DSBM already exists
in its L2 domain. If one already exists (and no new election is in in its L2 domain. If one already exists (and no new election is in
progress), the new SBM stays quiet in the background until an progress), the new SBM stays quiet in the background until an
election of DSBM is necessary. All messages related to the DSBM election of DSBM is necessary. All messages related to the DSBM
election and DSBM advertisements are always sent to the AllSBMAd- election and DSBM advertisements are always sent to the AllSBMAd-
dress. dress.
If no DSBM exists, the SBM initiates the election of a DSBM by If no DSBM exists, the SBM initiates the election of a DSBM by
skipping to change at page 43, line 5 skipping to change at page 44, line 5
(called ElectionIntervalTimer that is typically set to a value at (called ElectionIntervalTimer that is typically set to a value at
least equal to the DeadIntervalTimer value) to wait for the elec- least equal to the DeadIntervalTimer value) to wait for the elec-
tion to finish and to discover who is the best candidate. In this tion to finish and to discover who is the best candidate. In this
state, X keeps track of the best (or better) candidate seen so far state, X keeps track of the best (or better) candidate seen so far
(including itself). Whenever it receives another DSBM_WILLING mes- (including itself). Whenever it receives another DSBM_WILLING mes-
sage, it updates its notion of the best (or better) candidate sage, it updates its notion of the best (or better) candidate
based on the priority (and tie-breaking) criterion. During the based on the priority (and tie-breaking) criterion. During the
ElectionInterval, X sends out a DSBM_WILLING message every ElectionInterval, X sends out a DSBM_WILLING message every
RefreshInterval to (re)assert its candidacy. RefreshInterval to (re)assert its candidacy.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
At the end of the ElectionInterval, X checks whether it is the At the end of the ElectionInterval, X checks whether it is the
best candidate so far. If so, it declares itself to be the DSBM best candidate so far. If so, it declares itself to be the DSBM
(by sending out the I_AM_DSBM advertisement) and enters the (by sending out the I_AM_DSBM advertisement) and enters the
I_AM_DSBM state; otherwise, it decides to wait for the best candi- I_AM_DSBM state; otherwise, it decides to wait for the best candi-
date to declare itself the winner. To wait, X re-initializes its date to declare itself the winner. To wait, X re-initializes its
ElectDSBM state and continues to wait for another round of elec- ElectDSBM state and continues to wait for another round of elec-
tion (each round lasts for an ElectionTimerInterval duration). tion (each round lasts for an ElectionTimerInterval duration).
A SBM is in Idle state when no election is in progress and the A SBM is in Idle state when no election is in progress and the
skipping to change at page 44, line 5 skipping to change at page 45, line 5
At the end of the ElectionInterval, the elected DSBM sends out an At the end of the ElectionInterval, the elected DSBM sends out an
I_AM_DSBM advertisement and the DSBM is then operational. I_AM_DSBM advertisement and the DSBM is then operational.
A.4. DSBM Advertisements A.4. DSBM Advertisements
The I_AM_DSBM advertisement contains the following information: The I_AM_DSBM advertisement contains the following information:
1. DSBM address information -- contains the IP and L2 addresses 1. DSBM address information -- contains the IP and L2 addresses
of the DSBM and its SBM priority (a configuration parameter of the DSBM and its SBM priority (a configuration parameter
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
-- priority specified by a network administrator). The prior- -- priority specified by a network administrator). The prior-
ity value is used to choose among candidate SBMs during the ity value is used to choose among candidate SBMs during the
election algorithm. Higher integer values indicate higher election algorithm. Higher integer values indicate higher
priority and the value is in the range 0..255. The value zero priority and the value is in the range 0..255. The value zero
indicates that the SBM is not eligible to be the DSBM. The indicates that the SBM is not eligible to be the DSBM. The
IP address is required and used for breaking ties. The L2 IP address is required and used for breaking ties. The L2
address is for the interface of the managed segment. address is for the interface of the managed segment.
2. refresh interval -- contains the value of the refresh inter- 2. refresh interval -- contains the value of the refresh inter-
val in seconds. Value zero indicates the parameter has been val in seconds. Value zero indicates the parameter has been
omitted in the message. Receivers may substitute their own omitted in the message. Receivers may substitute their own
default value in this case. default value in this case.
3. SBMDeadInterval -- contains the value of the SBMDeadInterval 3. SBMDeadInterval -- contains the value of the SBMDeadInterval
in seconds. If the value is omitted (or value zero is speci- in seconds. If the value is omitted (or value zero is speci-
fied), a default value (from initial configuration) should be fied), a default value (from initial configuration) should be
used. used.
4. Miscellaneous configuration information to be advertised to
senders on the managed segment. See Appendix C for further
details.
A.5. DSBM_WILLING Messages A.5. DSBM_WILLING Messages
When a SBM wishes to declare its candidacy to be the DSBM during When a SBM wishes to declare its candidacy to be the DSBM during
an election phase, it sends out a DSBM_WILLING message. The an election phase, it sends out a DSBM_WILLING message. The
DSBM_WILLING message contains the following information: DSBM_WILLING message contains the following information:
1. DSBM address information -- Contains the SBM's own addresses 1. DSBM address information -- Contains the SBM's own addresses
(IP and L2 address), if it wishes to be the DSBM. The IP (IP and L2 address), if it wishes to be the DSBM. The IP
address is required and used for breaking ties. The L2 address is required and used for breaking ties. The L2
address is the address of the interface for the managed seg- address is the address of the interface for the managed seg-
ment in question. Also, the DSBM address information ment in question. Also, the DSBM address information
includes the corresponding priority of the SBM whose address includes the corresponding priority of the SBM whose address
is given above. is given above.
A.6. SBM State Variables SBM (Subnet Bandwidth Manager) March, 1999
SBM (Subnet Bandwidth Manager) November, 1998 A.6. SBM State Variables
For each network interface, a SBM maintains the following state For each network interface, a SBM maintains the following state
variables related to the election of the DSBM for the L2 domain on variables related to the election of the DSBM for the L2 domain on
that interface: that interface:
a) LocalDSBMAddrInfo -- current DSBM's IP address (initially, a) LocalDSBMAddrInfo -- current DSBM's IP address (initially,
0.0.0.0) and priority. All IP addresses are assumed to be in 0.0.0.0) and priority. All IP addresses are assumed to be in
network byte order. In addition, current DSBM's L2 address is network byte order. In addition, current DSBM's L2 address is
also stored as part of this state information. also stored as part of this state information.
skipping to change at page 45, line 43 skipping to change at page 47, line 5
when it has declared its candidacy. when it has declared its candidacy.
Figure 3 shows the state transition diagram for the election pro- Figure 3 shows the state transition diagram for the election pro-
tocol and the various states are described below. A complete tocol and the various states are described below. A complete
description of the state machine is provided in Section A.10. description of the state machine is provided in Section A.10.
A.7. DSBM Election States A.7. DSBM Election States
DOWN -- SBM is not operational. DOWN -- SBM is not operational.
DetectDSBM -- typically, the initial state of a SBM when it SBM (Subnet Bandwidth Manager) March, 1999
SBM (Subnet Bandwidth Manager) November, 1998
DetectDSBM -- typically, the initial state of a SBM when it
starts up. In this state, it checks to see whether a DSBM starts up. In this state, it checks to see whether a DSBM
already exists in its domain. already exists in its domain.
Idle -- SBM is in this state when no election is in progress Idle -- SBM is in this state when no election is in progress
and it is not the DSBM. In this state, SBM passively monitors and it is not the DSBM. In this state, SBM passively monitors
the state of the DSBM. the state of the DSBM.
ElectDSBM -- SBM is in this state when a DSBM election is in ElectDSBM -- SBM is in this state when a DSBM election is in
progress. progress.
skipping to change at page 46, line 42 skipping to change at page 48, line 5
be the DSBM. be the DSBM.
I_AM_DSBM message received -- SBM received a DSBM advertise- I_AM_DSBM message received -- SBM received a DSBM advertise-
ment from the DSBM in its L2 domain. ment from the DSBM in its L2 domain.
SBMDeadInterval Timeout -- The SBMDeadInterval timer has SBMDeadInterval Timeout -- The SBMDeadInterval timer has
fired. This means that the SBM did not receive even one DSBM fired. This means that the SBM did not receive even one DSBM
advertisement during this period and indicates possible advertisement during this period and indicates possible
failure of the DSBM. failure of the DSBM.
RefreshInterval Timeout -- The RefreshInterval timer has SBM (Subnet Bandwidth Manager) March, 1999
SBM (Subnet Bandwidth Manager) November, 1998
RefreshInterval Timeout -- The RefreshInterval timer has
fired. In the I_AM_DSBM state, this means it is the time for fired. In the I_AM_DSBM state, this means it is the time for
sending out the next DSBM advertisement. In the ElectDSBM sending out the next DSBM advertisement. In the ElectDSBM
state, the event means that it is the time to send out state, the event means that it is the time to send out
another DSBM_WILLING message. another DSBM_WILLING message.
ElectionInterval Timeout -- The ElectionInterval timer has ElectionInterval Timeout -- The ElectionInterval timer has
fired. This means that the SBM has waited long enough after fired. This means that the SBM has waited long enough after
declaring its candidacy to determine whether or not it suc- declaring its candidacy to determine whether or not it suc-
ceeded. ceeded.
CONTINUED ON NEXT PAGE CONTINUED ON NEXT PAGE
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
A.9. State Transition Diagram (Figure 3) A.9. State Transition Diagram (Figure 3)
+-----------+ +-----------+
+--<--------------<-|DetectDSBM |---->------+ +--<--------------<-|DetectDSBM |---->------+
| +-----------+ | | +-----------+ |
| | | |
| | | |
| | | |
| +-------------+ +---------+ | | +-------------+ +---------+ |
skipping to change at page 49, line 5 skipping to change at page 50, line 5
-- determines whether the entity represented by the first parameter -- determines whether the entity represented by the first parameter
is better than the second entity using the priority information is better than the second entity using the priority information
and the IP address information in the two parameters. and the IP address information in the two parameters.
If any address is zero, that entity If any address is zero, that entity
automatically loses; then first priorities are compared; higher automatically loses; then first priorities are compared; higher
priority candidate wins. If there is a tie based on priority candidate wins. If there is a tie based on
the priority value, the tie is broken using the IP the priority value, the tie is broken using the IP
addresses of tied candidates (one with the higher IP address in the addresses of tied candidates (one with the higher IP address in the
lexicographic order wins). Returns TRUE if first entity is a better lexicographic order wins). Returns TRUE if first entity is a better
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
choice. FALSE otherwise. choice. FALSE otherwise.
SendDSBMWilling Message() SendDSBMWilling Message()
Begin Begin
Send out DSBM_WILLING message listing myself as a candidate for Send out DSBM_WILLING message listing myself as a candidate for
DSBM (copy OwnAddr and priority into appropriate fields) DSBM (copy OwnAddr and priority into appropriate fields)
start RefreshIntervalTimer start RefreshIntervalTimer
goto ElectDSBM state goto ElectDSBM state
End End
skipping to change at page 50, line 5 skipping to change at page 51, line 5
Action: Initialize the local state variables (LocalDSBMADDR and Action: Initialize the local state variables (LocalDSBMADDR and
LocalDSBMAddrInfo set to 0). Start the ListenIntervalTimer. LocalDSBMAddrInfo set to 0). Start the ListenIntervalTimer.
State: DetectDSBM State: DetectDSBM
New State: Idle New State: Idle
Event: I_AM_DSBM message received Event: I_AM_DSBM message received
Action: set LocalDSBMAddrInfo = IncomingDSBMAddrInfo Action: set LocalDSBMAddrInfo = IncomingDSBMAddrInfo
start DeadDSBMInterval timer start DeadDSBMInterval timer
goto Idle State goto Idle State
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
State: DetectDSBM State: DetectDSBM
Event: ListenIntervalTimer fired Event: ListenIntervalTimer fired
New State: ElectDSBM New State: ElectDSBM
Action: Start ElectionIntervalTimer Action: Start ElectionIntervalTimer
SendDSBMWillingMessage(); SendDSBMWillingMessage();
State: DetectDSBM State: DetectDSBM
Event: DSBM_WILLING message received Event: DSBM_WILLING message received
New State: ElectDSBM New State: ElectDSBM
skipping to change at page 51, line 5 skipping to change at page 52, line 5
Event: DSBM_WILLING Message is received Event: DSBM_WILLING Message is received
New State: Depends on action (ElectDSBM or Idle) New State: Depends on action (ElectDSBM or Idle)
Action: /* check whether it is from the DSBM itself (shutdown) */ Action: /* check whether it is from the DSBM itself (shutdown) */
if (IncomingDSBMAddr == LocalDSBMAddr) { if (IncomingDSBMAddr == LocalDSBMAddr) {
cancel active timers cancel active timers
Set LocalDSBMAddrInfo = OwnAddrInfo Set LocalDSBMAddrInfo = OwnAddrInfo
Start ElectionIntervalTimer Start ElectionIntervalTimer
SendDSBMWillingMessage() /* goto ElectDSBM state */ SendDSBMWillingMessage() /* goto ElectDSBM state */
} }
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
/* else, ignore it */ /* else, ignore it */
continue in current state continue in current state
State: ElectDSBM State: ElectDSBM
Event: ElectionIntervalTimer Fired Event: ElectionIntervalTimer Fired
New State: depends on action (I_AM_DSBM or Current State) New State: depends on action (I_AM_DSBM or Current State)
Action: If (LocalDSBMAddrInfo == OwnAddrInfo) { Action: If (LocalDSBMAddrInfo == OwnAddrInfo) {
/* I won */ /* I won */
send I_AM_DSBM message send I_AM_DSBM message
skipping to change at page 52, line 5 skipping to change at page 53, line 5
State: ElectDSBM State: ElectDSBM
Event: RefreshIntervalTimer fired Event: RefreshIntervalTimer fired
New State: ElectDSBM New State: ElectDSBM
Action: /* continue to send DSBMWilling messages until Action: /* continue to send DSBMWilling messages until
election interval ends */ election interval ends */
SendDSBMWillingMessage() SendDSBMWillingMessage()
State: I_AM_DSBM State: I_AM_DSBM
Event: DSBM_WILLING message received Event: DSBM_WILLING message received
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
New State: I_AM_DSBM New State: depends on action (I_AM_DSBM or SteadyState)
Action: send I_AM_DSBM message /* reassert myself */ Action: /* check whether other guy is better */
If (ComparePrio(OwnAddrInfo, IncomingAddrInfo)) {
/* I am better */
send I_AM_DSBM message
restart RefreshIntervalTimer restart RefreshIntervalTimer
continue in current state
} else {
Set LocalDSBMAddrInfo = IncomingAddrInfo
cancel active timers
start DSBMDeadInterval timer
goto SteadyState
}
State: I_AM_DSBM State: I_AM_DSBM
Event: RefreshIntervalTimer fired Event: RefreshIntervalTimer fired
New State: I_AM_DSBM New State: I_AM_DSBM
Action: send I_AM_DSBM message Action: send I_AM_DSBM message
restart RefreshIntervalTimer restart RefreshIntervalTimer
State: I_AM_DSBM State: I_AM_DSBM
Event: I_AM_DSBM message received Event: I_AM_DSBM message received
New State: depends on action (I_AM_DSBM or Idle) New State: depends on action (I_AM_DSBM or Idle)
skipping to change at page 52, line 43 skipping to change at page 54, line 4
State: I_AM_DSBM State: I_AM_DSBM
Event: Want to shut myself down Event: Want to shut myself down
New State: DOWN New State: DOWN
Action: send DSBM_WILLING message with My address filled in, but Action: send DSBM_WILLING message with My address filled in, but
priority set to zero priority set to zero
goto Down State goto Down State
A.10.2 Suggested Values of Interval Timers A.10.2 Suggested Values of Interval Timers
To avoid DSBM outages for long period, to ensure quick recovery To avoid DSBM outages for long period, to ensure quick recovery
SBM (Subnet Bandwidth Manager) March, 1999
from DSBM failures, and to avoid timeout of PATH and RESV state at from DSBM failures, and to avoid timeout of PATH and RESV state at
the edge devices, we suggest the following values for various the edge devices, we suggest the following values for various
timers. timers.
Assuming that the RSVP implementations use a 30 second timeout for Assuming that the RSVP implementations use a 30 second timeout for
PATH and RESV refreshes, we suggest that the RefreshIntervalTimer PATH and RESV refreshes, we suggest that the RefreshIntervalTimer
should be set to about 5 seconds with DSBMDeadIntervalTimer set to should be set to about 5 seconds with DSBMDeadIntervalTimer set to
15 seconds (K=3, K*RefreshInterval). The DetectDSBMTimer should be 15 seconds (K=3, K*RefreshInterval). The DetectDSBMTimer should be
set to a random value between (DeadIntervalTimer, 2*DeadInterval- set to a random value between (DeadIntervalTimer, 2*DeadInterval-
Timer). The ElectionIntervalTimer should be set at least to the Timer). The ElectionIntervalTimer should be set at least to the
SBM (Subnet Bandwidth Manager) November, 1998
value of DeadIntervalTimer to ensure that each SBM has a chance to value of DeadIntervalTimer to ensure that each SBM has a chance to
have its DSBM_WILLING message (sent every RefreshInterval in have its DSBM_WILLING message (sent every RefreshInterval in
ElectDSBM state) delivered to others. ElectDSBM state) delivered to others.
A.10.3. Guidelines for Choice of Values for SBM_PRIORITY A.10.3. Guidelines for Choice of Values for SBM_PRIORITY
Network administrators should configure SBM protocol entity at Network administrators should configure SBM protocol entity at
each SBM-capable device with the device's "SBM priority" for each each SBM-capable device with the device's "SBM priority" for each
of the interfaces attached to a managed segment. SBM_PRIORITY is of the interfaces attached to a managed segment. SBM_PRIORITY is
an 8-bit, unsigned integer value (in the range 0-255) with higher an 8-bit, unsigned integer value (in the range 0-255) with higher
skipping to change at page 53, line 40 skipping to change at page 55, line 4
A.11. DSBM Election over switched links A.11. DSBM Election over switched links
The election algorithm works as described before in this case The election algorithm works as described before in this case
except each SBM-capable L2 device restricts the scope of the elec- except each SBM-capable L2 device restricts the scope of the elec-
tion to its local segment. As described in Section B.1 below, all tion to its local segment. As described in Section B.1 below, all
messages related to the DSBM election are sent to a special multi- messages related to the DSBM election are sent to a special multi-
cast address (AllSBMAddress). AllSBMAddress (its corresponding MAC cast address (AllSBMAddress). AllSBMAddress (its corresponding MAC
multicast address) is configured in the permanent database of multicast address) is configured in the permanent database of
SBM-capable, layer 2 devices so that all frames with AllSBMAddress SBM-capable, layer 2 devices so that all frames with AllSBMAddress
as the destination address are not forwarded and instead directed as the destination address are not forwarded and instead directed
SBM (Subnet Bandwidth Manager) March, 1999
to the SBM management entity in those devices. Thus, a DSBM can be to the SBM management entity in those devices. Thus, a DSBM can be
elected separately on each point-to-point segment in a switched elected separately on each point-to-point segment in a switched
topology. For example, in Figure 2, DSBM for "segment A" will be topology. For example, in Figure 2, DSBM for "segment A" will be
elected using the election algorithm between R1 and S1 and none of elected using the election algorithm between R1 and S1 and none of
the election-related messages on this segment will be forwarded by the election-related messages on this segment will be forwarded by
S1 beyond "segment A". Similarly, a separate election will take S1 beyond "segment A". Similarly, a separate election will take
place on each segment in this topology. place on each segment in this topology.
When a switched segment is a half-duplex segment, two senders (one When a switched segment is a half-duplex segment, two senders (one
sender at each end of the link) share the link. In this case, one sender at each end of the link) share the link. In this case, one
SBM (Subnet Bandwidth Manager) November, 1998
of the two senders will win the DSBM election and will be respon- of the two senders will win the DSBM election and will be respon-
sible for managing the segment. sible for managing the segment.
If a switched segment is full-duplex, exactly one sender sends on If a switched segment is full-duplex, exactly one sender sends on
the link in each direction. In this case, either one or two DSBMs the link in each direction. In this case, either one or two DSBMs
can exist on such a managed segment. If a sender at each end can exist on such a managed segment. If a sender at each end
wishes to serve as a DSBM for that end, it can declare itself to wishes to serve as a DSBM for that end, it can declare itself to
be the DSBM by sending out an I_AM_DSBM advertisement and start be the DSBM by sending out an I_AM_DSBM advertisement and start
managing the resources for the outgoing traffic over the segment. managing the resources for the outgoing traffic over the segment.
If one of the two senders does not wish itself to be the DSBM, If one of the two senders does not wish itself to be the DSBM,
then the other DSBM will not receive any DSBM advertisement from then the other DSBM will not receive any DSBM advertisement from
its peer and assume itself to be the DSBM for traffic traversing its peer and assume itself to be the DSBM for traffic traversing
in both directions over the managed segment. in both directions over the managed segment.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
APPENDIX B Appendix B
Message Encapsulation and Formats Message Encapsulation and Formats
To minimize changes to the existing RSVP implementations and to To minimize changes to the existing RSVP implementations and to
ensure quick deployment of a SBM in conjunction with RSVP, all ensure quick deployment of a SBM in conjunction with RSVP, all
communication to and from a DSBM will be performed using messages communication to and from a DSBM will be performed using messages
constructed using the current rules for RSVP message formats and constructed using the current rules for RSVP message formats and
raw IP encapsulation. For more details on the RSVP message for- raw IP encapsulation. For more details on the RSVP message for-
mats, refer to the RSVP specification (RFC 2205). No changes to mats, refer to the RSVP specification (RFC 2205). No changes to
the RSVP message formats are proposed, but new message types and the RSVP message formats are proposed, but new message types and
new L2-specific objects are added to the RSVP message formats to new L2-specific objects are added to the RSVP message formats to
skipping to change at page 56, line 5 skipping to change at page 57, line 5
B.3. RSVP-related Message Formats B.3. RSVP-related Message Formats
All RSVP messages directed to and from a DSBM may contain various All RSVP messages directed to and from a DSBM may contain various
RSVP objects defined in the RSVP specification and messages con- RSVP objects defined in the RSVP specification and messages con-
tinue to follow the formatting rules specified in the RSVP specif- tinue to follow the formatting rules specified in the RSVP specif-
ication. In addition, an RSVP implementation must also recognize ication. In addition, an RSVP implementation must also recognize
new object classes that are described below. new object classes that are described below.
B.3.1. Object Formats B.3.1. Object Formats
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
All objects are defined using the format specified in the RSVP All objects are defined using the format specified in the RSVP
specification. Each object has a 32-bit header that contains specification. Each object has a 32-bit header that contains
length (of the object in bytes including the object header), the length (of the object in bytes including the object header), the
object class number, and a C-Type. All unused fields should be set object class number, and a C-Type. All unused fields should be set
to zero and ignored on receipt. to zero and ignored on receipt.
B.3.2. LAN_NHOP, RSVP_HOP_L2, and LAN_LOOPBACK Objects B.3.2. SBM Specific Objects
LAN_NHOP, LAN_LOOPBACK, and RSVP_HOP_L2 objects are identified as Note that the Class-Num values for the SBM specific objects
separate object classes and the value of Class_Num for the objects (LAN_NHOP, LAN_LOOPBACK, and RSVP_HOP_L2) are chosen from the
is chosen so that non-SBM aware RSVP nodes will ignore the objects codespace 10XXXXXX. This coding assures that non-SBM aware RSVP
without forwarding them or generating an error message. nodes will ignore the objects without forwarding them or generat-
ing an error message.
Within the SBM specific codespace, note the following interpreta-
tion of the third most significant bit of the Class-Num:
a) Objects of the form 100XXXXX are to be silently dis-
carded by SBM nodes that do not recognize them.
b) Objects of the form 101XXXXX are to be silently for-
warded by SBM nodes that do not recognize them.
B.3.3. IEEE 802 Canonical Address Format B.3.3. IEEE 802 Canonical Address Format
The 48-bit MAC Addresses used by IEEE 802 were originally defined The 48-bit MAC Addresses used by IEEE 802 were originally defined
in terms of wire order transmission of bits in the source and des- in terms of wire order transmission of bits in the source and des-
tination MAC address fields. The same wire order applied to both tination MAC address fields. The same wire order applied to both
Ethernet and Token Ring. Since the bit transmission order of Eth- Ethernet and Token Ring. Since the bit transmission order of Ether-
ernet and Token Ring data differ - Ethernet octets are transmitted net and Token Ring data differ - Ethernet octets are transmitted
least significant bit first, Token Ring most significant first - least significant bit first, Token Ring most significant first -
the numeric values naturally associated with the same address on the numeric values naturally associated with the same address on
different 802 media differ. To facilitate the communication of different 802 media differ. To facilitate the communication of
address values in higher layer protocols which might span both address values in higher layer protocols which might span both
token ring and Ethernet attached systems connected by bridges, it token ring and Ethernet attached systems connected by bridges, it
was necessary to define one reference format - the so called was necessary to define one reference format - the so called canon-
canonical format for these addresses. Formally the canonical for- ical format for these addresses. Formally the canonical format
mat defines the value of the address, separate from the encoding defines the value of the address, separate from the encoding rules
rules used for transmission. It comprises a sequence of octets used for transmission. It comprises a sequence of octets derived
derived from the original wire order transmission bit order as from the original wire order transmission bit order as follows. The
follows. The least significant bit of the first octet is the first least significant bit of the first octet is the first bit transmit-
bit transmitted, the next least significant bit the second bit, ted, the next least significant bit the second bit, and so on to
and so on to the most significant bit of the first octet being the
8th bit transmitted; the least significant bit of the second octet SBM (Subnet Bandwidth Manager) March, 1999
is the 9th bit transmitted, and so on to the most significant bit
of the sixth octet of the canonical format being the last bit of the most significant bit of the first octet being the 8th bit
the address transmitted. transmitted; the least significant bit of the second octet is the
9th bit transmitted, and so on to the most significant bit of the
sixth octet of the canonical format being the last bit of the
address transmitted.
This canonical format corresponds to the natural value of the This canonical format corresponds to the natural value of the
address octets for Ethernet. The actual transmission order or for- address octets for Ethernet. The actual transmission order or for-
mal encoding rules for addresses on media which do not transmit mal encoding rules for addresses on media which do not transmit bit
bit serially are derived from the canonical format octet values. serially are derived from the canonical format octet values.
This document requires that all L2 addresses used in conjunction This document requires that all L2 addresses used in conjunction
with the SBM protocol be encoded in the canonical format as a with the SBM protocol be encoded in the canonical format as a
sequence of 6 octets. In the following, we define the object sequence of 6 octets. In the following, we define the object for-
mats for objects that contain L2 addresses that are based on the
SBM (Subnet Bandwidth Manager) November, 1998 canonical representation.
formats for objects that contain L2 addresses that are based on
the canonical representation.
B.3.4. RSVP_HOP_L2 object B.3.4. RSVP_HOP_L2 object
RSVP_HOP_L2 object uses object class = 161; it contains the L2 RSVP_HOP_L2 object uses object class = 161; it contains the L2
address of the previous hop L3 device in the IEEE Canonical address of the previous hop L3 device in the IEEE Canonical address
address format discussed above. format discussed above.
RSVP_HOP_L2 object: class = 161, C-Type represents the addressing format RSVP_HOP_L2 object: class = 161, C-Type represents the addressing format
used. In our case, C-Type=1 represents the IEEE Canonical Address used. In our case, C-Type=1 represents the IEEE Canonical Address
format. format.
0 1 2 3 0 1 2 3
+---------------+---------------+---------------+----------------+ +---------------+---------------+---------------+----------------+
| Length | 161 |C-Type(addrtype)| | Length | 161 |C-Type(addrtype)|
+---------------+---------------+---------------+----------------+ +---------------+---------------+---------------+----------------+
| Variable length Opaque data | | Variable length Opaque data |
skipping to change at page 57, line 37 skipping to change at page 58, line 51
C-Type = 1 (IEEE Canonical Address format) C-Type = 1 (IEEE Canonical Address format)
When C-Type=1, the object format is: When C-Type=1, the object format is:
0 1 2 3 0 1 2 3
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| 12 | 161 | 1 | | 12 | 161 | 1 |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Octets 0-3 of the MAC address | | Octets 0-3 of the MAC address |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Octets 4-5 of the MAC addr. | ///// | //// | | Octets 4-5 of the MAC addr. | /// | /// |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
//// -- unused (set to zero) SBM (Subnet Bandwidth Manager) March, 1999
/// -- unused (set to zero)
B.3.5. LAN_NHOP object B.3.5. LAN_NHOP object
LAN_NHOP object represents two objects, namely, LAN_NHOP_L3 LAN_NHOP object represents two objects, namely, LAN_NHOP_L3 address
address object and LAN_NHOP_L2 address object. object and LAN_NHOP_L2 address object.
<LAN_NHOP object> ::= <LAN_NHOP_L2 object> <LAN_NHOP_L3 object> <LAN_NHOP object> ::= <LAN_NHOP_L2 object> <LAN_NHOP_L3 object>
LAN_NHOP_L2 address object uses object class = 162 and uses the LAN_NHOP_L2 address object uses object class = 162 and uses the
same format (but different class number) as the RSVP_HOP_L2 same format (but different class number) as the RSVP_HOP_L2 object.
object. It provides the L2 or MAC address of the next hop L3 It provides the L2 or MAC address of the next hop L3 device.
SBM (Subnet Bandwidth Manager) November, 1998
device.
0 1 2 3 0 1 2 3
+---------------+---------------+---------------+----------------+ +---------------+---------------+---------------+----------------+
| Length | 162 |C-Type(addrtype)| | Length | 162 |C-Type(addrtype)|
+---------------+---------------+---------------+----------------+ +---------------+---------------+---------------+----------------+
| Variable length Opaque data | | Variable length Opaque data |
+---------------+---------------+---------------+----------------+ +---------------+---------------+---------------+----------------+
C-Type = 1 (IEEE 802 Canonical Address Format as defined below) C-Type = 1 (IEEE 802 Canonical Address Format as defined below)
See the RSVP_HOP_L2 address object for more details. See the RSVP_HOP_L2 address object for more details.
skipping to change at page 58, line 36 skipping to change at page 59, line 46
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Length = 8 | 163 | 1 | | Length = 8 | 163 | 1 |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| IPv4 NHOP address | | IPv4 NHOP address |
+---------------------------------------------------------------+ +---------------------------------------------------------------+
IPv6 LAN_NHOP_L3 object: class =163, C-Type = 2 IPv6 LAN_NHOP_L3 object: class =163, C-Type = 2
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Length = 20 | 163 | 2 | | Length = 20 | 163 | 2 |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
// IPv6 NHOP address (16 bytes) | | IPv6 NHOP address (16 bytes) |
+---------------------------------------------------------------+ +---------------------------------------------------------------+
B.3.6. LAN_LOOPBACK Object B.3.6. LAN_LOOPBACK Object
The LAN_LOOPBACK object gives the IP address of the outgoing SBM (Subnet Bandwidth Manager) March, 1999
interface for a PATH message and uses object class=164; both IPv4
and IPv6 formats are specified. The LAN_LOOPBACK object gives the IP address of the outgoing inter-
face for a PATH message and uses object class=164; both IPv4 and
IPv6 formats are specified.
IPv4 LAN_LOOPBACK object: class = 164, C-Type = 1 IPv4 LAN_LOOPBACK object: class = 164, C-Type = 1
0 1 2 3 0 1 2 3
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Length | 164 | 1 | | Length | 164 | 1 |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| IPV4 address of an interface | | IPV4 address of an interface |
SBM (Subnet Bandwidth Manager) November, 1998
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
IPv6 LAN_LOOPBACK object: class = 164, C-Type = 2 IPv6 LAN_LOOPBACK object: class = 164, C-Type = 2
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| Length | 164 | 2 | | Length | 164 | 2 |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| | | |
+ + + +
| | | |
skipping to change at page 59, line 32 skipping to change at page 60, line 43
B.3.7. TCLASS Object B.3.7. TCLASS Object
TCLASS object (traffic class based on IEEE 802.1p) uses object TCLASS object (traffic class based on IEEE 802.1p) uses object
class = 165. class = 165.
0 1 2 3 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | 165 | 1 | | Length | 165 | 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /// | /// | //// | //// | PV | | /// | /// | /// | /// | PV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Only 3 bits in data contain the user_priority value (PV). Only 3 bits in data contain the user_priority value (PV).
B.4. RSVP PATH and PATH_TEAR Message Formats B.4. RSVP PATH and PATH_TEAR Message Formats
As specified in the RSVP specification, a PATH and PATH_TEAR mes- As specified in the RSVP specification, a PATH and PATH_TEAR mes-
sages contain the RSVP Common Header and the relevant RSVP sages contain the RSVP Common Header and the relevant RSVP objects.
objects. For the RSVP Common Header, refer to the RSVP specifica-
tion (RFC 2205). Enhancements to an RSVP_PATH message include SBM (Subnet Bandwidth Manager) March, 1999
additional objects as specified below.
For the RSVP Common Header, refer to the RSVP specification (RFC
2205). Enhancements to an RSVP_PATH message include additional
objects as specified below.
<PATH Message> ::= <RSVP Common Header> [<INTEGRITY>] <PATH Message> ::= <RSVP Common Header> [<INTEGRITY>]
<RSVP_HOP_L2> <LAN_NHOP> <RSVP_HOP_L2> <LAN_NHOP>
<LAN_LOOPBACK> [<TCLASS>] <SESSION><RSVP_HOP> <LAN_LOOPBACK> [<TCLASS>] <SESSION><RSVP_HOP>
<TIME_VALUES> [<POLICY DATA>] <sender descriptor> <TIME_VALUES> [<POLICY DATA>] <sender descriptor>
<PATH_TEAR Message> ::= <RSVP Common Header> [<INTEGRITY>] <PATH_TEAR Message> ::= <RSVP Common Header> [<INTEGRITY>]
SBM (Subnet Bandwidth Manager) November, 1998
<LAN_LOOPBACK> <LAN_NHOP> <SESSION> <RSVP_HOP> <LAN_LOOPBACK> <LAN_NHOP> <SESSION> <RSVP_HOP>
[<sender descriptor>] [<sender descriptor>]
If the INTEGRITY object is present, it must immediately follow the If the INTEGRITY object is present, it must immediately follow the
RSVP common header. L2-specific objects must always precede the RSVP common header. L2-specific objects must always precede the
SESSION object. SESSION object.
B.5. RSVP RESV Message Format B.5. RSVP RESV Message Format
As specified in the RSVP specification, an RSVP_RESV message con- As specified in the RSVP specification, an RSVP_RESV message con-
tains the RSVP Common Header and relevant RSVP objects. In addi- tains the RSVP Common Header and relevant RSVP objects. In addi-
tion, it may contain an optional TCLASS object as described ear- tion, it may contain an optional TCLASS object as described ear-
lier. lier.
B.6. Additional RSVP message types to handle SBM interactions B.6. Additional RSVP message types to handle SBM interactions
New RSVP message types are introduced to allow interactions New RSVP message types are introduced to allow interactions between
between a DSBM and an RSVP node (host/router) for the purpose of a DSBM and an RSVP node (host/router) for the purpose of discover-
discovering and binding to a DSBM. New RSVP message types needed ing and binding to a DSBM. New RSVP message types needed are as
are as follows: follows:
RSVP Msg Type (8 bits) Value RSVP Msg Type (8 bits) Value
DSBM_WILLING 66 DSBM_WILLING 66
I_AM_DSBM 67 I_AM_DSBM 67
All SBM-specific messages are formatted as RSVP messages with an All SBM-specific messages are formatted as RSVP messages with an
RSVP common header followed by SBM-specific objects. RSVP common header followed by SBM-specific objects.
<SBMP_MESSAGE> ::= <SBMP common header> <SBM-specific objects> <SBMP_MESSAGE> ::= <SBMP common header> <SBM-specific objects>
where <SBMP common header> ::= <RSVP common Header> [<INTEGRITY>] where <SBMP common header> ::= <RSVP common Header> [<INTEGRITY>]
For each SBM message type, there is a set of rules for the permis- For each SBM message type, there is a set of rules for the permis-
sible choice of object types. These rules are specified using sible choice of object types. These rules are specified using
Backus-Naur Form (BNF) augmented with square brackets surrounding
optional sub-sequences. The BNF implies an order for the objects
in a message. However, in many (but not all) cases, object order
makes no logical difference. An implementation should create mes-
sages with the objects in the order shown here, but accept the
objects in any permissible order. Any exceptions to this rule will
be pointed out in the specific message formats.
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
Backus-Naur Form (BNF) augmented with square brackets surrounding
optional sub-sequences. The BNF implies an order for the objects in
a message. However, in many (but not all) cases, object order makes
no logical difference. An implementation should create messages
with the objects in the order shown here, but accept the objects in
any permissible order. Any exceptions to this rule will be pointed
out in the specific message formats.
DSBM_WILLING Message DSBM_WILLING Message
<DSBM_WILLING message> ::= <SBM Common Header> <DSBM IP ADDRESS> <DSBM_WILLING message> ::= <SBM Common Header> <DSBM IP ADDRESS>
<DSBM L2 address> <SBM PRIORITY> <DSBM L2 address> <SBM PRIORITY>
I_AM_DSBM Message I_AM_DSBM Message
<I_AM_DSBM> ::= <SBM Common Header> <DSBM IP ADDRESS> <DSBM L2 address> <I_AM_DSBM> ::= <SBM Common Header> <DSBM IP ADDRESS> <DSBM L2 address>
<SBM PRIORITY> <DSBM Timer Intervals> <SBM PRIORITY> <DSBM Timer Intervals>
<SBM_INFO> [<NON_RESV_SEND_LIMIT>]
For compatibility reasons, receivers of the I_AM_DSBM message must
be prepared to receive additional objects of the Unknown Class type
[RFC-2205].
All I_AM_DSBM messages are multicast to the well known AllSBMAd- All I_AM_DSBM messages are multicast to the well known AllSBMAd-
dress. The default priority of a SBM is 1 and higher priority dress. The default priority of a SBM is 1 and higher priority
values represent higher precedence. The priority value zero indi- values represent higher precedence. The priority value zero indi-
cates that the SBM is not eligible to be the DSBM. cates that the SBM is not eligible to be the DSBM.
Relevant Objects Relevant Objects
DSBM IP ADDRESS objects use object class = 42; IPv4 DSBM IP DSBM IP ADDRESS objects use object class = 42; IPv4 DSBM IP ADDRESS
ADDRESS object uses <Class=42, C-Type=1> and IPv6 DSBM IP ADDRESS object uses <Class=42, C-Type=1> and IPv6 DSBM IP ADDRESS object
object uses <Class=42, C-Type=2>. uses <Class=42, C-Type=2>.
IPv4 DSBM IP ADDRESS object: class = 42, C-Type =1 IPv4 DSBM IP ADDRESS object: class = 42, C-Type =1
0 1 2 3 0 1 2 3
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| IPv4 DSBM IP Address | | IPv4 DSBM IP Address |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
IPv6 DSBM IP ADDRESS object: Class = 42, C-Type = 2 IPv6 DSBM IP ADDRESS object: Class = 42, C-Type = 2
SBM (Subnet Bandwidth Manager) March, 1999
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| | | |
+ + + +
| | | |
+ IPv6 DSBM IP Address + + IPv6 DSBM IP Address +
| | | |
+ + + +
| | | |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
<DSBM L2 address> Object is the same as <RSVP_HOP_L2> object with C-Type <DSBM L2 address> Object is the same as <RSVP_HOP_L2> object with C-Type
=1 for IEEE Canonical Address format. =1 for IEEE Canonical Address format.
SBM (Subnet Bandwidth Manager) November, 1998
<DSBM L2 address> ::= <RSVP_HOP_L2> <DSBM L2 address> ::= <RSVP_HOP_L2>
a SBM may omit this object by including a NULL L2 address object. For a SBM may omit this object by including a NULL L2 address object. For
C-Type=1 (IEEE Canonical address format), such a version of the L2 C-Type=1 (IEEE Canonical address format), such a version of the L2
address object contains value zero in the six octet s corresponding to the address object contains value zero in the six octet s corresponding to the
MAC address (see section B.3.4 for the exact format). MAC address (see section B.3.4 for the exact format).
SBM_PRIORITY Object: class = 43, C-Type =1 SBM_PRIORITY Object: class = 43, C-Type =1
0 1 2 3 0 1 2 3
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
| //// | //// | //// | SBM priority | | /// | /// | /// | SBM priority |
+---------------+---------------+---------------+---------------+ +---------------+---------------+---------------+---------------+
TIMER INTERVAL VALUES. TIMER INTERVAL VALUES.
The two timer intervals, namely, DSBM Dead Interval and DSBM The two timer intervals, namely, DSBM Dead Interval and DSBM
Refresh Interval, are specified as integer values each in the Refresh Interval, are specified as integer values each in the
range of 0..255 seconds. Both values are included in a single range of 0..255 seconds. Both values are included in a single
"DSBM Timer Intervals" object described below. "DSBM Timer Intervals" object described below.
DSBM Timer Intervals Object: class = 44, C-Type =1 DSBM Timer Intervals Object: class = 44, C-Type =1
+---------------+---------------+---------------+----------------+ +---------------+---------------+---------------+----------------+
| //// | //// | DeadInterval |Refresh Interval| | /// | /// | DeadInterval |Refresh Interval|
+---------------+---------------+---------------+----------------+ +---------------+---------------+---------------+----------------+
SBM_INFO Object. NON_RESV_SEND_LIMIT Object: class = 45, C-Type = 1
The SBM_INFO object is designed to provide additional information
about the managed segment. This object uses <Class=45, C-Type=1>
and includes information such as media type (shared or switched,
half duplex vs full duplex, etc.) and whether (and how much)
traffic a sender can send before receiving a RESV message from a
receiver.
SBM_INFO Object: class = 45, C-Type = 1
0 1 2 3 0 1 2 3
+---------------+---------------+---------------+----------------+ +---------------+---------------+---------------+----------------+
| //// | //// | //// | Media Type | | NonResvSendLimit(limit on traffic allowed to send without RESV)|
+---------------+---------------+---------------+----------------+
| OptFlowSpec (limit on traffic allowed to send without RESV) |
| | | |
+---------------+---------------+---------------+----------------+ +---------------+---------------+---------------+----------------+
Media Type values: 0 (Shared segment); a default SBM (Subnet Bandwidth Manager) March, 1999
1 (switched, half duplex)
SBM (Subnet Bandwidth Manager) November, 1998 <NonResvSendLimit> ::= <Intserv Sender_TSPEC object> (class=12, C-Type =2)
2 (switched, full duplex) The NON_RESV_SEND_LIMIT object specifies a per-flow limit on the
profile of traffic which a sending host is allowed to send onto a
managed segment without a valid RSVP reservation (see Appendix C
for further details on the usage of this object). The object con-
tains the NonResvSendLimit parameter. This parameter is equivalent
to the Intserv SENDER_TSPEC (see RFC 2210 for contents and encoding
rules). The SENDER_TSPEC includes five parameters which describe a
traffic profile (r, b, p, m and M). Sending hosts compare the
SENDER_TSPEC describing a sender traffic flow to the SENDER_TSPEC
advertised by the DSBM. If the SENDER_TSPEC of the traffic flow in
question is less than or equal to the SENDER_TSPEC advertised by
the DSBM, it is allowable to send traffic on the corresponding flow
without a valid RSVP reservation in place. Otherwise it is not.
OptFlowSpec: The network administrator may configure the DSBM to disallow any
This parameter specifies whether or not a sender can send traffic sent traffic in the absence of an RSVP reservation by configuring a
when its RESV request fails. The parameter is an Intserv SENDER_TSPEC NonResvSendLimit in which r = 0, b = 0, p = 0, m = infinity and M =
object (see RFC 2210 for contents and encoding rules). 0. Similarly the network administrator may allow any traffic to be
If the token bucket rate (r) specified in sent in the absence of an RSVP reservation by configuring a Non-
this parameter is zero, it indicates that the sender(s) must not send ResvSendLimit in which r = infinity, b = infinity, p = infinity, m
traffic if their RESV request fails; otherwise, the parameter specifies = 0 and M = infinity. Of course, any of these parameters may be set
per-session limit on the amount of traffic that can be sent when RESV to values between zero and infinity to advertise finite per-flow
attempt for the session fails. limits.
<OptFlowSpec> ::= <Intserv Sender_TSPEC object> (class=12, C-Type =2) The NON_RESV_SEND_LIMIT object is optional. Senders on a managed
segment should interpret the absence of the NON_RESV_SEND_LIMIT
object as equivalent to an infinitely large SENDER_TSPEC (it is
permissible to send any traffic profile in the absence of an RSVP
reservation).
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
Appendix C
The DSBM as a Source of Centralized Configuration Information
There are certain configuration parameters which it may be useful
to distribute to layer-3 senders on a managed segment. The DSBM may
serve as a centralized management point from which such parameters
can easily be distributed. In particular, it is possible for the
network administrator configuring a DSBM to cause certain confi-
guration parameters to be distributed as objects appended to the
I_AM_DSBM messages. The following configuration object is defined
at this time. Others may be defined in the future. See Appendix B
for further details regarding the NON_RESV_SEND_LIMIT object.
C.1. NON_RESV_SEND_LIMIT
As we QoS enable layer 2 segments, we expect an evolution from sub-
nets comprised of traditional shared segments (with no means of
traffic separation and no DSBM), to subnets comprised of dedicated
segments switched by sophisticated switches (with both DSBM and
802.1p traffic separation capability).
A set of intermediate configurations consists of a group of QoS
enabled hosts sending onto a traditional shared segment. A layer-3
device (or a layer-2 device) acts as a DSBM for the shared segment,
but cannot enforce traffic separation. In such a configuration, the
DSBM can be configured to limit the number of reservations approved
for senders on the segment, but cannot prevent them from sending.
As a result, senders may congest the segment even though a network
administrator has configured an appropriate limit for admission
control in the DSBM.
One solution to this problem which would give the network adminis-
trator control over the segment, is to require applications (or
operating systems on behalf of applications) not to send until they
have obtained a reservation. This is problematic as most applica-
tions are used to sending as soon as they wish to and expect to get
whatever service quality the network is able to grant at that time.
Furthermore, it may often be acceptable to allow certain applica-
tions to send before a reservation is received. For example, on a
segment comprised of a single 10 Mbps ethernet and 10 hosts, it may
be acceptable to allow a 16 Kbps telephony stream to be transmitted
but not a 3 Mbps video stream.
A more pragmatic solution then, is to allow the network administra-
tor to set a per-flow limit on the amount of non-adaptive traffic
which a sender is allowed to generate on a managed segment in the
absence of a valid reservation. This limit is advertised by the
DSBM and received by sending hosts. An API on the sending host can
SBM (Subnet Bandwidth Manager) March, 1999
then approve or deny an application's QoS request based on the
resources requested.
The NON_RESV_SEND_LIMIT object can be used to advertise a Flowspec
which describes the shape of traffic that a sender is allowed to
generate on a managed segment when its RSVP reservation requests
have either not yet completed or have been rejected.
SBM (Subnet Bandwidth Manager) March, 1999
ACKNOWLEDGEMENTS ACKNOWLEDGEMENTS
Authors are grateful to Eric Crawley (Argon), Russ Fenger (Intel), Authors are grateful to Eric Crawley (Argon), Russ Fenger (Intel),
David Melman (Siemens), Ramesh Pabbati (Microsoft), Mick Seaman David Melman (Siemens), Ramesh Pabbati (Microsoft), Mick Seaman
(3COM), Andrew Smith (Extreme Networks) for their constructive (3COM), Andrew Smith (Extreme Networks) for their constructive com-
comments on the SBM design and the earlier versions of this docu- ments on the SBM design and the earlier versions of this document.
ment.
6. Authors` Addresses 6. Authors` Addresses
Raj Yavatkar Raj Yavatkar
Intel Corporation Intel Corporation
2111 N.E. 25th Avenue, 2111 N.E. 25th Avenue,
Hillsboro, OR 97124 Hillsboro, OR 97124
USA USA
phone: +1 503-264-9077 phone: +1 503-264-9077
email: yavatkar@ibeam.intel.com email: yavatkar@ibeam.intel.com
skipping to change at page 65, line 5 skipping to change at page 68, line 5
phone: +1 408 526 4257 phone: +1 408 526 4257
email: fred@cisco.com email: fred@cisco.com
Michael Speer Michael Speer
Sun Microsystems, Inc Sun Microsystems, Inc
901 San Antonio Road UMPK15-215 901 San Antonio Road UMPK15-215
Palo Alto, CA 94303 Palo Alto, CA 94303
phone: +1 650-786-6368 phone: +1 650-786-6368
email: speer@Eng.Sun.COM email: speer@Eng.Sun.COM
SBM (Subnet Bandwidth Manager) November, 1998 SBM (Subnet Bandwidth Manager) March, 1999
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