|
Network Working Group Request for Comments: 4678 Category: Informational |
A. Bivens IBM Research September 2006 |
This memo provides information for the Internet community. It does not specify an Internet standard of any kind. Distribution of this memo is unlimited.
Copyright © The Internet Society (2006).
This RFC is not a candidate for any level of Internet Standard. The IETF disclaims any knowledge of the fitness of this RFC for any purpose and in particular notes that the decision to publish is not based on IETF review for such things as security, congestion control, or inappropriate interaction with deployed protocols. The RFC Editor has chosen to publish this document at its discretion. Readers of this document should exercise caution in evaluating its value for implementation and deployment. See RFC 3932 for more information.
Entities responsible for distributing work across a group of systems
traditionally do not know a great deal about the ability of the
applications on those systems to complete the work in a satisfactory
fashion. Workload management systems traditionally know a great deal
about the health of applications, but have little control over the
rate in which these applications receive work. The
Server/Application State Protocol (SASP) provides a mechanism for
load balancers and workload management systems to communicate better
ways of distributing the existing workload to the group members.
1. Introduction
1.1. Overview
1.2. Identities
2. Requirements Notation
3. Conventions Used in This Document
4. General Message Structure
4.1. TLV Structure
4.2. Component Types
4.3. SASP Protocol Header
4.4. Version Negotiation
5. Singular Protocol Components
5.1. Member Data Component
5.2. Group Data Component
5.3. Weight Entry Data Component
5.4. Member State Instance Component
6. Group Protocol Components
6.1. Group of Member Data Component
6.2. Group of Weight Data Component
6.3. Group of Member State Data Components
7. Protocol Messages
7.1. Registration Request and Reply
7.1.1. Registration Request
7.1.2. Registration Reply
7.2. DeRegistration Request and Reply
7.2.1. DeRegistration Request
7.2.2. DeRegistration Reply
7.3. Get Weights Request and Reply
7.3.1. Get Weights Request
7.3.2. Get Weights Reply
7.4. Send Weights
7.5. Set Member State Request and Reply
7.5.1. Set Member State Request
7.5.2. Set Member State Reply
7.6. Set Load Balancer State Request and Reply
7.6.1. Set LB State Request
7.6.2. Set LB State Reply
8. Example of SASP Message Encoding
9. Protocol Flow
9.1. Normal Protocol Flow
9.2. Behavior in Error Cases
9.3. Example Flow 1: Load Balancer Registration,
Getting Weights, and Application-Side Quiescing
9.4. Example Flow 2: Set Load Balancer State, Application
Registration, and Load Balancer Group DeRegistration
9.5. Avoiding Single Points of Failure
10. Security Considerations
11. Normative References
Appendix A. Acknowledgements
The Server/Application State Protocol is designed to enable load balancers or schedulers (1) to receive traffic weight recommendations from Workload Managers, (2) to register with Workload Managers members of load balancing/scheduling groups, and (3) to enable Workload Managers to suggest new load balancing group members to load balancers and schedulers
The figure below shows where the SASP entities are in typical load balancing topology.
----------
| Group |
-------->|Member 1|<--|
| ---------- |
| |
--------- ---------- | ---------- |
|Request|<------>| Load |---| | Group | |
|Origins|<------>|Balancer|----------->|Member 2|<--|
--------- | |---| ---------- |
---------- | |
^ | ---------- |
| -------->| Group | |
SASP | |Member 3|<--|
------- ---------- |
| |
| -------------------- |
| | Group | SASP |
------>| Workload Manager |<----------
--------------------
Figure 1
SASP is a binary protocol that facilitates communication from load balancers/schedulers to Workload Managers. The connection between the Group Workload Manager (GWM) and the load balancer/scheduler is expected to be a long-running TCP connection. In SASP interactions, the GWM acts as a SASP server waiting to receive connections from the other SASP components. Server port 3860 has been registered with the IANA for SASP communications. It is expected that all SASP components are configured with the DNS name of the GWM to develop
this connection. Security in SASP is handled by transporting binary messages over Secure Socket Layer/Transport Layer Security (SSL/TLS). This document only describes the message format and protocol behavior above the connection and security layers. Connection and security aspects including SSL's authentication and encryption will be implementation specific.
SASP identifies a load balancer by a UTF-8 string called a "LB UID". A group of "equivalent" servers providing a service is identified by a UTF-8 string called a "Group Name", which is interpreted in the context of the LB UID. A server is identified by its IP address and (optional) port and protocol numbers. A GWM is only identified implicitly as the entity on the other end of the TCP connection from a load balancer or group member. All of these identifiers are local; there are no globally unique identifiers. The LB UID and GroupName fields are unstructured so that components could assign values to these fields that are meaningful to an administrator. For example, in many cases, a load balancer would use the name an administrator provided for the serverfarm group as the groupname in a SASP- specified group. Since the naming options in industry load balancers do not carry explicit naming restrictions, SASP naming options also carry no naming restrictions.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119].
Any string interpreted by the group workload manager is assumed to use UTF8. Components implementing SASP MUST support the printable ASCII subrepertoire of UTF8 (0x20-0x7E). Components MAY also choose to provide support for additional UTF8 character encodings. It is
recommended that customers using SASP-enabled products configure the string-generating components (load balancers and group members) to use the same character repertoire.
Many of the SASP structures involve the transfer of multi-byte integer values. In all cases where multi-byte integer values are used, they are considered to be in network-byte order (big-endian).
SASP is organized into several message components. For extendibility and ease of processing, each message component is described in a TLV (Type, Length, Value) format. An illustration of the SASP structure can be found in the example below. The first section is the header followed by the message component type. As mentioned, the header, message component, and all other components have a TLV format. Each component value contains a variable number of fields, some of which refer to upcoming components (explained component descriptions are in upcoming sections). After the first message component, any number of additional components may be included (as stipulated in the fields of the message type).
------------------------------------------------- | |T| Type (SASP Header Type) | | SASP |----------------------------------| | Header |L| Length of SASP header TLV | | |----------------------------------| | |V| Header fields | |-----------------------------------------------| | |T| Type (Message Type) | | Message |----------------------------------| | Type |L| Length of this Message Type TLV| | Component |----------------------------------| | |V| Component fields | |-----------------------------------------------| | |T| Type (Component Type) | | |----------------------------------| |Component-1 |L| Length of this TLV | | |----------------------------------| | |V| Component fields | |-----------------------------------------------| | ... | |-----------------------------------------------| | |T| Type (Component Type) | | |----------------------------------| |Component-n |L| Length of this TLV | | |----------------------------------| | |V| Component fields | -------------------------------------------------
Figure 2
An illustration of the TLV format is shown below. The Type is a two-byte field containing a binary value for the component type. The Length is a two-byte field containing the size of the TLV in bytes (including the Type and Length fields). The Value field is a variable-length field that actually contains the data of the component.
< xxxx xxxx xxxx xxxx, xxxx xxxx xxxx xxxx, xxxx...........xxxx >
|-----------------| |-----------------| |-----------------|
Type(2 bytes) Length(2 bytes) Value(variable)
Figure 3
The TLV structure requires a type value for each protocol component. All SASP types are listed in this section.
Reserved 0x0000-0x1000
Message Types
Registration Request 0x1010
Registration Reply 0x1015
DeRegistration Request 0x1020
DeRegistration Reply 0x1025
Get Weights Request 0x1030
Get Weights Reply 0x1035
Send Weights 0x1040
Set Load Balancer State Request 0x1050
Set Load Balancer State Reply 0x1055
Set Member State Request 0x1060
Set Member State Reply 0x1065
Utility Component Types
SASP Header 0x2010
Singular Component Types
Member Data 0x3010
Group Data 0x3011
Weight Entry Data 0x3012
Member State Instance 0x3013
Group Component Types
Group of Member Data 0x4010
Group of Weight Entry Data 0x4011
Group of Member State Data 0x4012
Reserved 0xF000-0xFFFF
An illustration of the SASP Header is found in the table below. It is expected that every message will start with the SASP Protocol Header component.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SASP header type (0x2010) | Size of this TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Version | Message Length
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message ID
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|
+-+-+-+-+-+-+-+-+
Figure 4
To negotiate the version of the protocol used by the entities involved in the connection, the GWM views the version included in the load balancer request as the load balancer's proposed version.
If the GWM supports the version proposed by the load balancer, it will respond to the connection with the appropriate response code and the load balancer's proposed version in the response header. This proposed version should be the version used for all messages in this connection.
If the GWM does not support the version proposed by the load balancer, the GWM will respond with a "message not understood" response code and the GWM's highest supported SASP version in the version field of the response header. This is an indication for the load balancer to come down to GWM's SASP version level.
The most basic of SASP components are singular components because they describe a single instance of a member, member resource, member weight, or group. Some of the SASP components reuse other SASP components. When this is the case, any component being reused by a base component will simply be given immediately following the base component. Some examples of this technique are seen and explained in the Weight Entry and Member State Instance components.
The member data component describes a particular member and is referred to by other components.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Member Data Type (0x3010) | Size of this TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol | Port | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
| |
+ +
| |
+ IP Address of Member +
| |
+ +-+-+-+-+-+-+-+-+
| | Label Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Label .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5
for example: TCP = 0x06, UDP = 0x11, etc.
*** A value of 0 can be given for the Protocol and Port to signify
a system level member. However, 0 shouldn't be perceived as a
wildcard for either Port or Protocol fields (i.e., a
deregistration request that includes a MemberData component with a
0 for the port doesn't mean deregister all applications listening
on any port of that IP and protocol).
IPv4 Address: 00 00 00 00 00 00 00 00 00 00 00 00 xx xx xx xx
IPv6 Address: xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx xx
The group data component simply describes a group with which to associate other singular components.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Data Type (0x3011) | Size of this TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LB UID Length | |
+-+-+-+-+-+-+-+-+ +
. .
. LB UID .
. .
+ +-+-+-+-+-+-+-+-+
| |Group Name Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Group Name .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6
Length = 0) to indicate all groups from the associated load
balancer.
The Weight Entry Component is used by the get and send weight messages to associate a weight with a particular member (or Member Data). It also uses an opaque member state field and a general member flags field to denote extra information about a member (described below). When the Weight Entry component is used, the Member Data TLV it refers to is listed first, immediately followed by the Weight Entry TLV.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Member Data Type (0x3010) | Size of this Member Data TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Member Data Fields .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Weight Entry Type (0x3012) | Size of this Weight Entry TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| State Field | Flags Field | Weight |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7
+ xxxx xxx1 The GWM has located this running system or
application.
+ xxxx xxx0 The GWM has not located this running system or
application.
group. When quiesced, the member will still show up in the weights, but the quiesce flag will be set, and its weight will be zero. When the administrator returns this member to active, the quiesce flag will be 0, and a weight will be provided. If the quiesce flag is on, this member should be avoided by the load balancer.
+ xxxx xx1x The member is quiesced.
+ xxxx xx0x The member is active (not quiesced).
+ xxxx x1xx This member has been registered by the load
balancer/scheduler.
+ xxxx x0xx This member has registered itself.
The goal of the confident flag is to convey to the load balancer that it should look to other methods of distribution recommendations if the GWM cannot give recommendations for any of the valid group members. If some members of the group have the confident flag on but the contact flag off or the quiesced flag on (meaning these members should always be avoided) while the remaining members of the group have their confident flag off, the load balancer should determine the appropriate distribution of work for those members with the confident flag off by other means.
+ xxxx 1xxx GWM has determined it has knowledge of the state
of this member.
+ xxxx 0xxx GWM has no knowledge of the state of this member.
The Member State Instance Component is used by the set member state message to indicate the sender's perceived state of the member mentioned. This component is used to set values that will ultimately end up in the WeightEntry component. When the Member State Instance component is used, the Member Data TLV it refers to is listed first, immediately followed by the Member State Instance TLV.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Member Data Type (0x3010) | Size of this Member Data TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. Member Data Fields .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Member State Instance(0x3013) | Size of Member State Inst TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| State Field | Flags Field |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8
and its weight will be zero. When the administrator returns this member to active, the quiesce flag will be 0, and a weight will be provided.
+ xxxx xxx1 The member or load balancer setting this state is
quiescing this member.
+ xxxx xxx0 The member or load balancer setting this state is
placing the member in a non-quiesced state.
Group protocol components each contain a collection of related singular components. In particular, they associate Member Data, Weight Entry, or Member State Instance components to a particular Group Data component. In these cases, the particular "Group of x" component will be immediately followed by the Group Data component. The Group Data component will be immediately followed by any number of singular components the group contains. In figures listed in this document, a component type with an asterisk denotes a component that is repeated a number of times.
The "group of member data" component describes a particular group of members and is used in the registration message components.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group of Member Data (0x4010) | Size of GroupOfMemberData TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Member Count | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
. .
. Group Data TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. *Array of Member Data Components .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9
The "Group of Weight Data" Component is used by the get and send weight messages to create a list of Weight Entry Components for a particular group.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Group Weight Entry Type(0x4011)| Size of GroupOfWeightEntry TLV|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Weight Entry Count | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
. .
. Group Data TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. *Array of Weight Entry Data Components .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10
The "group of member state data" component describes a particular set of members and their corresponding state fields used in the Set Member State messages.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Group Weight Entry Type(0x4011)| Size of GroupOfWeightEntry TLV|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Member State Instance Count | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
. .
. Group Data TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. *Array of Member State Data Components .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11
SASP messages are a collection of TLVs (Type, Length, and Value components). The header has no information as to what type of message it is part of; the purpose-specific information is in the message component. This format could facilitate placing more than one message component in a single message; however, this use of multiple message components is not supported in every GWM and could produce indeterminate behavior. Similar to the other protocol components, when a message component needs to involve other components, the additional components immediately follow the message component.
All SASP requests sent to the GWM will be acknowledged with a reply. The reply contains information requested as well as a single-byte response code describing the success of the request. SASP defines some general response codes in the range of 0x00 - 0x3F that may be used regardless of the response message type. However, some request types may cause specific error conditions not covered by the general response codes. The response code range of 0x40 - 0xFF is used for these message-specific response codes. Any given SASP response will only contain one response code (depending on the error type). This section explains the format and purpose of specific SASP messages.
This exchange happens between the load balancer/scheduler and the Group Workload Manager as well as between the Group Workload Manager and the member to register the members in a group specified by Group Name. Applications are identified with an IP address, Protocol, and
Port. Systems are identified only with an IP Address (Port = 0x0000 and Protocol = 0x00). All members in a group have equivalent functionality, so the Group Workload Manager can direct routers, load balancers, and schedulers to any member in the group. Even though registrations can come from either the load balancer/scheduler or the actual member, member-initiated registrations will only be considered if the Trust flag is set while the state of the load balancer/scheduler is set.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Registration Req. Type(0x1010)| Size of Registration Req. TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flag Field | Group of Member Data Count | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
. .
. *Array of Group of Member Data Components .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*There will be as many Group of Member Data Components as "Group of
Member Data Count" has specified.
Figure 12
+ xxxx xxx1 The entity sending this message is the load
balancer.
+ xxxx xxx0 The entity sending this message is an
Application.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Registration Reply Type(0x1015)| Size of Registration Reply TLV|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Code |
+-+-+-+-+-+-+-+-+
Figure 13
* 0x50 Invalid Group Name Size (size == 0)
* 0x51 Invalid LB UID Size (size == 0 or > max)
**The Invalid Group error return code refers to the LB or member attempting to form a group that the GWM considers invalid. For example, some GWM vendors may not support the registration of both System and Application members in the same group. To determine what can cause a GWM to return this error code, the vendor's documentation must be consulted.
This exchange happens between the load balancer/scheduler and the Group Workload Manager as well as between the Group Workload Manager and the Member to deregister members from a group specified by Group Name with the Group Workload Manager. Even though deregistrations can come from either the load balancer/scheduler or the actual member, member-initiated deregistrations will only be considered if the Trust flag is set with a Set LB State message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|DeRegistration Req.Type(0x1020)|Size of DeRegistration Req. TLV|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flag Field | Reason | Group of Member Data Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. *Array of Group of Member Data Components .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*There will be as many Group of Member Data Components as "Group of
Member Data Count" has specified.
Figure 14
+ xxxx xxx1 The entity sending this message is the load
balancer.
+ xxxx xxx0 The entity sending this message is an
Application.
+ 0x00 No reason given.
+ 0x01 Learned and Purposeful, i.e., a human has deconfigured
this member from the load balancer configuration.
+ 0x80-0xFF Open for vendor specific deregistration reason
codes.
** If Member Count equals zero in the Group of Member Data component, the Group Workload Manager will deregister the entire group. ** Recall that the Group Data Component contains both a Unique LB Identifier field and a Group Name field. If the Group Data component has no Group Name (GroupData's Group Name Length==0), the Group Workload Manager will deregister all groups associated with this load balancer.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| DeReg. Reply Type(0x1025) | Size of DeReg. Reply TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Code |
+-+-+-+-+-+-+-+-+
Figure 15
+ 0x00 Successful
+ 0x10 Message not understood
+ 0x11 GWM will not accept this message from the sender.
Reasons for this include the following:
a. The message was not sent by a LB and trust flag is off
b. LB attempted to address members of a different LB in the
message
c. Vendor specific criteria for this message type were not
met.
+ 0x41 Application or System not registered
+ 0x42 Unknown Group Name
+ 0x43 Unknown LB UID
+ 0x44 Duplicate Member in Request
+ 0x46 Duplicate Group in Request (for remove all
members/groups requests)
+ 0x51 Invalid LB UID Size (size == 0 or > max)
+ 0x61 Member is deregistering itself, but LB hasn't yet
contacted the GWM. This deregistration will not be
processed.
This exchange happens between the load balancer/scheduler and the
Group Workload Manager to get weights for the groups specified in the
list of GroupData objects. In the case of application load balancing
(balancing workloads between applications with the same
functionality), the load balancer would call the Group Workload
Manager every Interval (parameter returned by the Group Workload
Manager below) to get an array of weights and associated members
(e.g., Application1 20, SecondCopyOfApplication 30,
ThirdCopyOfApplication 5). The load balancer then uses these weights
to determine the fashion in which work will be sent to each of the
members. For example, in the case of weighted round robin, the load
balancer/scheduler would then send a request to Application1, the
next to SecondCopyOfApplication, and the next to
ThirdCopyOfApplication. After 15 requests, the load
balancer/scheduler would only send work to Application1 and
SecondCopyOfApplication. After an additional 30 requests, the load
balancer/scheduler would only send requests to
SecondCopyofApplication. After another 10 requests, the load
balancer/scheduler product would start over using the weights of 20,
30, and 5 again; or if the Interval number of seconds have passed, the load balancer/scheduler would get a new set of weights.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Get Weights Req. Type(0x1030) | Size of Get Weights Req. TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group Data Count | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
. .
. *Array of Group Data Components .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*There will be as many Group Data Components as "Group Data Count"
has specified.
Figure 16
** If there is no group name in the Group Data structure of the Get Weights Request, the load balancer is requesting weights for all groups registered for the load balancer.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Get Weights Reply Type(0x1035)| Size of Get Weights Reply TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Code | Interval | Group of Weight
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Entry Data Count| |
+-+-+-+-+-+-+-+-+ +
. .
. *Group of Weight Entry Data Components .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* There will be as many Group of Weight Entry Data Components as
"Group of Weight Entry Data Count" has specified.
Figure 17
+ 0x00 Successful
+ 0x10 Message not understood
+ 0x11 GWM will not accept this message from the sender.
Reasons for this include the following:
a. LB attempted to address members of a different LB in the
message
b. Vendor specific criteria for this message type were not
met.
+ 0x42 Unknown Group Name
+ 0x43 Unknown LB UID
+ 0x46 Duplicate Group in Request
+ 0x51 Invalid LB uid Size (size == 0 or > max)
This exchange happens between the Group Workload Manager and the load
balancer/scheduler to send the new weights for the group specified in
Group Name. This message is unique in that it is the only message
exchange initiated by the Group Workload Manager and the only message
that has no reply. In the case of application load balancing
(balancing workloads between applications with the same
functionality), the Group Workload Manager would message the load
balancer at a possibly dynamic interval (chosen by the Group Workload
Manager) to send an array of weights and associated members (e.g.,
Application1 20, SecondCopyOfApplication 30, ThirdCopyOfApplication
5). The load balancer then uses these weights to determine the
fashion in which work will be sent to each of the members. For
example, in the case of weighted round robin, the load
balancer/scheduler would then send a request to Application1, the
next to SecondCopyOfApplication, and the next to
ThirdCopyOfApplication. After 15 requests, the load
balancer/scheduler would only send work to Application1 and
SecondCopyOfApplication. After another 30 requests, the load
balancer/scheduler would only send requests to
SecondCopyofApplication. After an additional 10 requests, the load
balancer/scheduler product would start over using the weights of 20,
30, and 5 again, if it has not yet received a new set of weights.
The Group Workload Manager only sends this message if the Push flag
has been enabled using a Set Load Balancer State message.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Send Weights Type(0x1040) | Size of Send Weights TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Group of Weight Data Count | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
. .
. *Group of Weight Entry Data Components .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* There will be as many Group of Weight Entry Data Components as
"Group of Weight Data Count" has specified.
Figure 18
This is a special exchange that can take place between the load balancer and the Group Workload Manager or between the Member and the Group Workload Manager to pass information about the state of the member including placing the member in quiesced or non-quiesced states. In particular, the load balancer/scheduler can use this message to quiesce a set of members. Members can also use this message to quiesce themselves as well as to pass certain state information to the load balancer/scheduler that is opaque to the Group Workload Manager. This opaque state information is passed to the load balancer/scheduler with the weights during get and send weight messages.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|SetMemberState Req.Type(0x1060)|Size of SetMemberState Req. TLV|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flag Field | Group of MemberStateData Count| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
. .
. *Array of Group of Member State Data Components .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
*There will be as many Group of Member State Data Components as
"Group of Member State Data Count" has specified.
Figure 19
+ xxxx xxx1 The entity sending this message is the load
balancer.
+ xxxx xxx0 The entity sending this message is an
Application.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set Member State Reply(0x1025)|Size of SetMemberStateReply TLV|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Code |
+-+-+-+-+-+-+-+-+
Figure 20
+ 0x00 Successful
+ 0x10 Message not understood
+ 0x11 GWM will not accept this message from the sender.
Reasons for this include the following:
a. The message was not sent by a LB and trust flag is off
b. LB attempted to address members of a different LB in the
message
c. Vendor specific criteria for this message type were not
met.
+ 0x41 Application or System not registered
+ 0x42 Unknown Group Name
+ 0x43 Unknown LB UID
+ 0x44 Duplicate Member in Request
+ 0x46 Duplicate Group in Request
+ 0x50 Invalid Group Name Size (size == 0)
+ 0x51 Invalid LB UID Size (size == 0 or > than max)
+ 0x61 Member is setting state for itself, but LB hasn't yet
contacted the GWM. This request will not be processed.
This is an exchange that can take place between the load balancer and the Group Workload Manager to pass information about the state (and partial configuration) of the load balancer.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Set LB State Req. Type (0x1050)| Size of Set LB State Req. TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LB UID Length | |
+-+-+-+-+-+-+-+-+ +
. .
. LB UID .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LB Health | LB Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 21
0x00 - 0x7F Least Healthy - Most Healthy
0x80 - 0xFF Reserved
+ xxxx xxx1 The load balancer should receive weights through
the Send Weights message (GWM pushes weights to load
balancer). Even if this flag is set, the GWM must still
respond accordingly to any Get Weights messages from the
load balancer.
+ xxxx xxx0 The load balancer will send a Get Weights message
to get the new weights. This is the default behavior.
(load balancer pulls weights from GWM).
+ xxxx xx1x Trust any member-initiated registration,
deregistration, or set state message. Immediately reflect
the registration, deregistration, or new state in the
weights sent.
+ xxxx xx0x Do not trust any member-initiated registration,
deregistration, or set state message. Registration,
Deregistration, and State Setting of members can only occur
from the load balancer. Discard any member-initiated
registration, deregistration, or set state message. This
is the default behavior.
+ xxxx x1xx The GWM must not include members whose weights
and state (i.e., contact and quiesce flags) have not
changed since they were last sent.
+ xxxx x0xx The GWM must include the weights of all group
members when sending the weights to this load balancer
(including members whose weights and state have not
changed). This is the default behavior.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. .
. SASP Header TLV .
. .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Set LB State Reply (0x1025) | Size of Set LB State Reply TLV|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Return Code |
+-+-+-+-+-+-+-+-+
Figure 22
+ 0x00 Successful
+ 0x10 Message not understood
+ 0x11 GWM will not accept this message from the sender.
Reasons for this include the following:
a. LB attempted to address the state of a different LB
b. Vendor specific criteria for this message type were not
met.
+ 0x51 Invalid LB UID Size (size == 0 or > max)
This section provides an example of the actual SASP message encoding. For this example, we will look at a sample GetWeights Reply in which two webservers are registered to a serverfarm called FARM1. The IP addresses of the two webservers are 10.10.10.1 and 10.10.10.2. Currently the GWM has a weight of 40 for 10.10.10.1 and 20 for 10.10.10.2. The load balancer has a unique Identifier of "LB1" and the message example was sent by the GWM in response to a request (MessageID: 0x32000000) for FARM1's weights.
The TLVs necessary for this message are shown in the following list.
------------------------------------ | | Field | Size | Value | |-----------|---------|------------| |T| Type | 2 bytes | 0x2010 | |-----------|---------|------------| |L| Length | 2 bytes | 0x000D | |-----------|---------|------------| | | Version | 1 byte | 0x01 | | |---------|---------|------------| |V| Mesg Len| 4 bytes | 0x0000 006A| | |---------|---------|------------| | | Mesg ID | 4 bytes | 0x3200 0000| ------------------------------------
Figure 23
------------------------------------ | | Field | Size | Value | |-----------|---------|------------| |T| Type | 2 bytes | 0x1035 | |-----------|---------|------------| |L| Length | 2 bytes | 0x0009 | |-----------|---------|------------| | | RetCode | 1 byte | 0x00 | | |---------|---------|------------| |V| Interval| 2 bytes | 0x0040 | | |---------|---------|------------| | |GWD Count| 2 bytes | 0x0001 | ------------------------------------ *GWD Count = Group of Weight Data Count
Figure 24
------------------------------------ | | Field | Size | Value | |-----------|---------|------------| |T| Type | 2 bytes | 0x4011 | |-----------|---------|------------| |L| Length | 2 bytes | 0x0006 | |-----------|---------|------------| |V| WE Count| 2 bytes | 0x0002 | ------------------------------------ *WE Count = Weight Entry Count
Figure 25
------------------------------------ | | Field | Size | Value | |-----------|---------|------------| |T| Type | 2 bytes | 0x3011 | |-----------|---------|------------| |L| Length | 2 bytes | 0x000E | |-----------|---------|------------| | |LBUID len| 1 byte | 0x03 | | |---------|---------|------------| | | LBUID | 3 bytes | "LB1" or | | | | | 0x4C 42 31 | |V|---------|---------|------------| | |GroupName| 1 byte | 0x05 | | | Length | | | | |---------|---------|------------| | | Group | | "FARM1" or | | | Name | 5 bytes | 0x46 41 52 | | | | | 4D 31 | ------------------------------------
Figure 26
------------------------------------ | | Field | Size | Value | |-----------|---------|------------| |T| Type | 2 bytes | 0x3010 | |-----------|---------|------------| |L| Length | 2 bytes | 0x0018 | |-----------|---------|------------| | | Protocol| 1 byte | 0x06 | | |---------|---------|------------| | | Port | 2 bytes | 0x0050 | | |---------|---------|------------| |V| IP |16 bytes | 0x0000 0000| | | Address | | 0000 0000| | | | | 0000 0000| | | | | 0A0A 0A01| | |---------|---------|------------| | |Label Len| 1 byte | 0x00 | | |---------|---------|------------| | | Label | 0 bytes | | ------------------------------------
Figure 27
------------------------------------ | | Field | Size | Value | |-----------|---------|------------| |T| Type | 2 bytes | 0x3012 | |-----------|---------|------------| |L| Length | 2 bytes | 0x0008 | |-----------|---------|------------| | | State | 1 byte | 0x00 | | |---------|---------|------------| |V| Flags | 1 byte | 0x0D | | |---------|---------|------------| | | Weight | 2 bytes | 0x0028 | ------------------------------------
Figure 28
------------------------------------ | | Field | Size | Value | |-----------|---------|------------| |T| Type | 2 bytes | 0x3010 | |-----------|---------|------------| |L| Length | 2 bytes | 0x0018 | |-----------|---------|------------| | | Protocol| 1 byte | 0x06 | | |---------|---------|------------| | | Port | 2 bytes | 0x0050 | | |---------|---------|------------| |V| IP |16 bytes | 0x0000 0000| | | Address | | 0000 0000| | | | | 0000 0000| | | | | 0A0A 0A02| | |---------|---------|------------| | |Label Len| 1 byte | 0x00 | | |---------|---------|------------| | | Label | 0 bytes | | ------------------------------------
Figure 29
------------------------------------ | | Field | Size | Value | |-----------|---------|------------| |T| Type | 2 bytes | 0x3012 | |-----------|---------|------------| |L| Length | 2 bytes | 0x0008 | |-----------|---------|------------| | | State | 1 byte | 0x00 | | |---------|---------|------------| |V| Flags | 1 byte | 0x0D | | |---------|---------|------------| | | Weight | 2 bytes | 0x0014 | ------------------------------------
Figure 30
A hex stream representing this same message is below:
20 10 00 0D 01 00 00 00 6A 32 00 00 00 10 35 00 09 00 00 40
00 01 40 11 00 06 00 02 30 11 00 0E 03 4C 42 31 05 46 41 52
4D 31 30 10 00 18 06 00 50 00 00 00 00 00 00 00 00 00 00 00
00 0A 0A 0A 01 00 30 12 00 08 00 0D 00 28 30 10 00 18 06 00
50 00 00 00 00 00 00 00 00 00 00 00 00 0A 0A 0A 02 00 30 12
00 08 00 0D 00 14
(106 bytes)
This section describes the expected general flow of the SASP messages.
SASP first starts with a connection from an LB to the GWM. This is expected to be a long-running connection and will be used for many messages. After establishing the connection, the LB either registers a group of members or sets a Trust flag to allow the members to register themselves. The Trust flag is set using a Set LB State Request (both message flows are shown below).
Registration from load balancer
------------ Registration Request ------------------ | |----------------------->| | | Load | | Group Workload | | Balancer | Registration Reply | Manager | | |<-----------------------| | ------------ ------------------
Set LB State from load balancer
------------ Set LB State Request ------------------ | |----------------------->| | | Load | | Group Workload | | Balancer | Set LB State Reply | Manager | | |<-----------------------| | ------------ ------------------
Figure 31
The connection can start with other requests, but any other request would likely result in an error (unless this connection is a reconnection that has happened a short period of time after the original connection). For example, if the load balancer issues a deregistration request as its first message, it will receive an error because it has not registered any groups.
The load balancer always drops all state information after a loss of connection and can recover it using a GetWeights message. The establishment of a new connection causes the GWM to assume that the old one is broken. In this case, the GWM will keep all state for the load balancer for a limited time after a detected break. After the limited time has expired, all state for the broken connection will be discarded by the GWM.
Registration of group members may be done at any time. A load balancer can register anywhere from one group with one member to many groups of many members. The member may also register itself if the Trust flag has been set and it knows the appropriate load balancer information. Registrations will add to groups that already exist, but return errors if any of the registered members already exist.
In the case of system load balancing, the representation of a member is only the member's IP address with a 0 used as the value for the port and protocol. In the case of application load balancing, the representation of a member is the member's IP address and the Application's port and protocol.
Deregistration of group members may be done at any time. A load balancer can deregister anywhere from one group with one member to many groups of many members. The LB may also deregister entire groups or deregister all of its groups at once. The member may also deregister itself if the Trust flag has been set and it knows the appropriate load balancer information.
Once members are registered, the GWM will start the monitoring and weight computation processes to determine weights to be sent back to the load balancer. At any time the load balancer may issue a GetWeights message and ask for the weights for members in a particular group. The LB may also set a flag telling the GWM to send the weights without waiting for the GetWeights message. If this flag is set, the GWM will send the weights at an interval it feels is appropriate (the interval could change depending on the algorithm used and variance of the weights generated).
At any time the LB or a particular member may quiesce the member through the use of a SetMemberState message. In this case, the member's weight will always be zero, and the quiesce flag will be
turned on when sending its weight. Members may also use this message to send an opaque state value that will also be presented when sending weights.
At any time, the load balancer may choose to send the GWM a SetLBState request to configure its interaction. The message allows the load balancer to set the Push, Trust, and NoChange_NoSend flags. It also allows the load balancer to pass a health value to the GWM to be displayed.
While behaviors in many error conditions will be product specific, the following error cases should have the following expected behavior.
Case: The protocol is violated in an unrecoverable manner by either end of the connection.
Behavior: Either end of the connection may choose to disconnect to avoid future message synchronization problems. The state kept when disconnected is vendor specific.
Case: LB or application attempts to connect to the GWM before the GWM is fully up and running.
Behavior: The LB or application should wait at least 20 seconds to retry the connection.
Case: Members attempt to register or deregister themselves before the LB develops the connection with the GWM.
Behavior: In this case, the members would receive a reply with an error code signifying that there is no LB registered with that LB UID.
Case: Member registers or deregisters for an LB who has not set the Trust flag.
Behavior: GWM will send Member a reply containing an error code.
Case: LB asks for weights for a group that doesn't exist.
Behavior: GWM will send LB a reply containing an error code.
Case: LB or Member attempts to register a member that is already registered in that group.
Behavior: GWM will send sender a reply containing an error code.
Case: LB or Member attempts to deregister a member or group that doesn't exist.
Behavior: GWM will send sender a reply containing an error code.
Case: LB or Member tries to set state for a non-registered server.
Behavior: GWM will send sender a reply containing an error code.
Case: LB tries to Get Weights for an unregistered group.
Behavior: GWM will send LB a reply containing an error code.
Load Group Workload
Balancer Manager
| |
| 1) Registration Request |
|------------------------>|
|<------------------------|
| Registration Reply |
| |
| 2) Set LB State Request |
|------------------------>|
|<------------------------|
| Set LB State Reply |
| |
| 3) Get Weights Request |
|------------------------>|
|<------------------------|
| Get Weights Reply |
| | 4) Set Member State Req. --------
| |<-------------------------|Member|
| |------------------------->| A |
| | Set Member State Reply --------
| |
| | 5) Set Member State Req. --------
| |<-------------------------|Member|
| |------------------------->| C |
| | Set Member State Reply --------
| |
| 6) Get Weights Request |
|------------------------>|
|<------------------------|
| Get Weights Reply |
| |
| | 7) Set Member State Req. --------
| |<-------------------------|Member|
| |------------------------->| C |
| | Set Member State Reply --------
| |
| 8) Get Weights Request |
|------------------------>|
|<------------------------|
| Get Weights Reply |
| |
Figure 32
LB Health: 0x00 Flags: 0000 0010
Members Opaque State Flags Weight
-------- ------------ --------- ------
Member A 0x00 0000 1101 20
Member B 0x00 0000 1101 40
Member C 0x00 0000 1101 5
Members Opaque State Flags
-------- ------------ ---------
Member A 0x32 0000 0000
Members Opaque State Flags
-------- ------------ ---------
Member C 0x0A 0000 0001
Members Opaque State Flags Weight
-------- ------------ --------- ------
Member A 0x32 0000 1101 20
Member B 0x00 0000 1101 40
Member C 0x0A 0000 1111 5
Members Opaque State Flags
-------- ------------ ---------
Member C 0x0A 0000 0000
Members Opaque State Flags Weight
-------- ------------ --------- ------
Member A 0x32 0000 1101 20
Member B 0x00 0000 1101 40
Member C 0x0A 0000 1101 5
Load Group Workload
Balancer Manager
| |
| 1) Set LB State Request |
|------------------------>|
|<------------------------|
| Set LB State Reply |
| |
| | 2) Registration Request --------
| |<-------------------------|Member|
| |------------------------->| A |
| | Registration Reply --------
| |
| | 3) Registration Request --------
| |<-------------------------|Member|
| |------------------------->| B |
| | Registration Reply --------
| |
| 4) Send Weights Mesg |
|<------------------------|
| |
| | 5) Registration Request --------
| |<-------------------------|Member|
| |------------------------->| C |
| | Registration Reply --------
| |
| 6) Send Weights Mesg |
|<------------------------|
| |
|7) Deregistration Request|
|------------------------>|
|<------------------------|
| Deregistration Reply |
| |
Figure 39
Health: 0x7F Flags: 0000 0011
Members Opaque State Flags Weight
-------- ------------ --------- ------
Member A 0x00 0000 1001 20
Member B 0x00 0000 1001 40
Members Opaque State Flags Weight
-------- ------------ --------- ------
Member A 0x00 0000 1001 20
Member B 0x00 0000 1001 40
Member C 0x00 0000 1001 5
Member Data Count = 0
connect to multiple GWMs and register the same groups with corresponding members. The load balancer may choose to coordinate the recommendations of each GWM by any method it chooses (e.g., statistical combination such as averaging). The coordination of weights from multiple GWMs is product specific and not addressed in this protocol.
SASP is a binary stream expected to be transported over a TCP connection. To secure this protocol, it is expected that implementers of the protocol use a secure mode of transport such as SSL/TLS. Discussions around security concerns have been listed below:
Security Issue: In insecure environments, if the LB UID becomes known by another system, the other system could initiate a connection and send messages to the GWM causing the GWM to replace the previous (possibly valid) connection for the new (potentially bad) connection.
Solution: This may not be a concern if the load balancer and GWM are in protected parts of the network. If the administrator is concerned about this vulnerability, she should use SSL or TLS to provide authentication for the connection. When using SSL or TLS to secure the connection, the administrator SHOULD use both server and client authentication through client and server certificates. The GWM will trust any certificate that is signed by an authority it's been configured to trust.
Security Issue: In insecure environments, if the load balancer turns the Trust Flag on, any member or other system can send a Registration Message and be included in the serverfarm to receive work. A person with bad intentions and the correct information could exploit this feature and register his own application to receive work. His counterfeit application could capture valuable data from unsuspecting clients as their transactions are sent to his system.
Solution: This may not be a concern if the GWM and its members are in protected parts of the network. If the administrator is concerned about this vulnerability, she should use SSL or TLS to provide authentication for the member connections. When using SSL or TLS to authenticate the connection, the administrator would need to explicitly install valid certificates on each component
while at the same time establishing the trusted certificates of each component. This would make certain that only those trusted components would be permitted to connect to the GWM.
[RFC1700] Reynolds, J. and J. Postel, "Assigned Numbers", STD 2, RFC 1700, October 1994.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing Architecture", RFC 4291, February 2006.
The author gratefully acknowledges contributions by Mark Albert, David McCowan, John Fenton, Derek Huckaby, Dyan Collins, and Stefano Testa. Mark Albert, David McCowan, John Fenton, Derek Huckaby, Dyan Collins, and Stefano Testa were supported for this work by Cisco Systems Inc.
The author would also like to thank John Arwe, Dave Bostjancic, Brian Carpenter, Donna Dillenberger, Gus Kassimis, and Thomas Narten for their efforts in the creation and refining of this work.
Alan Bivens
IBM T.J. Watson Research Center
19 Skyline Drive
Hawthorne, NY 10532
US
EMail: jbivens@us.ibm.com
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