INTERNET DRAFT EXPIRES JUNE 1999 INTERNET DRAFT
Network Working Group D. Ruffen
T. Len
Category: Informational J. Yanacek
Cabletron Systems Incorporated
December 1998
Cabletron's SecureFast VLAN Operational Model
Version 1.8
<draft-rfced-info-cabletron-vlan-00.txt>
Status of This Memo
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Distribution of this document is unlimited.
Abstract
Cabletron's SecureFast VLAN (SFVLAN) product implements a
distributed connection-oriented switching protocol that provides
fast forwarding of data packets at the MAC layer. The product
uses the concept of virtual LANs (VLANs) to determine the validity
of call connection requests and to scope the broadcast of certain
flooded messages.
Table of Contents
Status of this Memo......................................... 1
Copyright Notice............................................ 1
Abstract.................................................... 1
1. Introduction............................................. 3
1.1 Data Conventions..................................... 3
1.2 Definitions of Commonly Used Terms................... 4
2. SFVLAN Overview.......................................... 6
2.1 Features............................................. 6
2.2 VLAN Principles...................................... 7
2.2.1 Default, Base and Inherited VLANs.............. 8
2.2.2 VLAN Configuration Modes....................... 8
2.2.2.1 Endstations............................ 8
2.2.2.2 Ports.................................. 9
2.2.2.3 Order of Precedence.................... 9
2.2.3 Ports with Multiple VLAN Membership............ 10
2.3 Tag/Length/Value Method of Addressing................ 10
2.4 Architectural Overview............................... 11
3. Base Services............................................ 13
D. Ruffen, et. al. Informational [Page 1]
4. Call Processing.......................................... 14
4.1 Directory Service Center............................. 14
4.1.1 Local Add Server............................... 15
4.1.2 Inverse Resolve Server......................... 15
4.1.3 Local Delete Server............................ 17
4.2 Topology Service Center.............................. 17
4.2.1 Neighbor Discovery Server...................... 18
4.2.2 Spanning Tree Server........................... 18
4.2.2.1 Creating and Maintaining
the Spanning Tree........... 18
4.2.2.2 Remote Blocking........................ 19
4.2.3 Link State Server.............................. 20
4.3 Resolve Service Center............................... 20
4.3.1 Table Server................................... 21
4.3.2 Local Server................................... 21
4.3.3 Subnet Server.................................. 21
4.3.4 Interswitch Resolve Server..................... 21
4.3.5 Unresolvable Server............................ 22
4.3.6 Block Server................................... 22
4.4 Policy Service Center................................ 23
4.4.1 Unicast Rules Server........................... 23
4.5 Connect Service Center............................... 24
4.5.1 Local Server................................... 24
4.5.2 Link State Server.............................. 24
4.5.3 Directory Server............................... 25
4.6 Filter Service Center................................ 25
4.7 Path Service Center.................................. 25
4.7.1 Link State Server.............................. 25
4.7.2 Spanning Tree Server........................... 25
4.8 Flood Service Center................................. 26
4.8.1 Tag-Based Flood Server......................... 26
5. Monitoring Call Connections.............................. 26
5.1 Definitions.......................................... 26
5.2 Tapping a Connection................................. 27
5.2.1 Types of Tap Connections....................... 27
5.2.2 Locating the Probe and Establishing
the Tap Connection.......... 28
5.2.3 Status Field................................... 29
5.3 Untapping a Connection............................... 30
6. Interswitch Message Protocol (ISMP)...................... 31
6.1 General Packet Structure............................. 31
6.1.1 Frame Header................................... 31
6.1.2 ISMP Packet Header............................. 32
6.1.2.1 Version 2.............................. 32
6.1.2.2 Version 3.............................. 33
6.1.3 ISMP Message Body.............................. 33
6.2 Interswitch BPDU Message............................. 34
6.3 Interswitch Remote Blocking Message.................. 35
6.4 Interswitch Resolve Message.......................... 36
6.4.1 Prior to Version 1.8........................... 36
6.4.2 Version 1.8.................................... 39
D. Ruffen, et. al. Informational [Page 2]
6.5 Interswitch New User Message......................... 43
6.6 Interswitch Tag-Based Flood Message.................. 46
6.6.1 Prior to Version 1.8........................... 46
6.6.2 Version 1.8.................................... 49
6.7 Interswitch Tap/Untap Message........................ 52
7. Security Considerations.................................. 55
8. References............................................... 55
9. Authors' Addresses....................................... 55
10. Full Copyright Statement................................ 55
1. Introduction
This memo is being distributed to members of the Internet community
in order to solicit reactions to the proposals contained herein.
While the specification discussed here may not be directly
relevant to the research problems of the Internet, it may be of
interest to researchers and implementers.
1.1 Data Conventions
The methods used in this memo to describe and picture data adhere
to the standards of Internet Protocol documentation [RFC1700]. In
particular:
The convention in the documentation of Internet Protocols
is to express numbers in decimal and to picture data in
"big-endian" order. That is, fields are described left to
right, with the most significant octet on the left and the
least significant octet on the right.
The order of transmission of the header and data described
in this document is resolved to the octet level. Whenever
a diagram shows a group of octets, the order of
transmission of those octets is the normal order in which
they are read in English.
Whenever an octet represents a numeric quantity the left
most bit in the diagram is the high order or most
significant bit. That is, the bit labeled 0 is the most
significant bit.
Similarly, whenever a multi-octet field represents a
numeric quantity the left most bit of the whole field is
the most significant bit. When a multi-octet quantity is
transmitted the most significant octet is transmitted
first.
D. Ruffen, et. al. Informational [Page 3]
1.2 Definitions of Commonly Used Terms
This section contains a collection of definitions for terms that
have a specific meaning for the SFVLAN product and that are used
throughout the text.
Switch ID
A 10-octet value that uniquely identifies an SFVLAN switch
within the switch fabric. The value consists of the 6-octet
base MAC address of the switch, followed by 4 octets of zeroes.
Network link
The physical connection between two switches. A network link
is associated with a network interface (or port) of a switch.
Network port
An interface on a switch that attaches to another switch.
Access port
An interface on a switch that attaches to a user endstation.
Port ID
A 10-octet value that uniquely identifies an interface of a
switch. The value consists of the 6-octet base MAC address of
the switch, followed by the 4-octet local port number of the
interface.
Neighboring switches
Two switches attached to a common (network) link.
Call connection
A mapping of user traffic through a switch that correlates the
source and destination address pair specified within the packet
to an inport and outport pair on the switch.
Call connection path
A set of 0 to 7 network links over which user traffic travels
between the source and destination endstations. Call
connection paths are selected from a list of alternate equal
cost paths calculated by the VLS protocol [IDvlsp], and are
chosen to load balance traffic across the fabric.
D. Ruffen, et. al. Informational [Page 4]
Ingress switch
The owner switch of the source endstation of a call connection.
That is, the source endstation is attached to one of the local
access ports of the switch.
Egress switch
The owner switch of the destination endstation of a call
connection. That is, the destination endstation is attached to
one of the local access ports of the switch.
Intermediate switches
Any switch along the call connection path on which user traffic
enters and leaves over network links. Note that the following
types of connections have no intermediate switches:
- Call connections between source and destination endstations
that are attached to the same switch -- that is, the ingress
switch is the same as the egress switch. Note also that the
path for this type of connection consists of 0 network links.
- Call connections where the ingress and egress switches are
physical neighbors connected by a single network link. The
path for this type of connection consists of a single network
link.
InterSwitch Message protocol (ISMP)
The protocol used for interswitch communication between SFVLAN
switches.
Undirected messages
Messages that are (potentially) sent to all SFVLAN switches in
the switch fabric -- that is, they are not directed to any
particular switch. ISMP messages with a message type of 5, 7
or 8 are undirected messages.
Switch flood path
The path used to send undirected messages throughout the switch
fabric. The switch flood path is formed using a spanning tree
algorithm that provides a single path through the switch fabric
that guarantees loop-free delivery to every other SFVLAN switch
in the fabric.
D. Ruffen, et. al. Informational [Page 5]
Upstream Neighbor
That switch attached to the inport of the switch flood path --
that is, the switch from which undirected messages are
received. Note that each switch receiving an undirected
message has, at most, one upstream neighbor, and the originator
of any undirected ISMP message has no upstream neighbors.
Downstream Neighbors
Those switches attached to all outports of the switch flood
path except the port on which the undirected message was
received. Note that for each undirected message some number of
switches have no downstream neighbors.
Virtual LAN (VLAN) identifier
A VLAN is a logical grouping of ports and endstations such that
all ports and endstations in the VLAN appear to be on the same
physical (or extended) LAN segment even though they may be
geographically separated.
A VLAN identifier consists of a variable-length string of
octets. The first octet in the string contains the number of
octets in the remainder of the string -- the actual VLAN
identifier value. A VLAN identifier can be from 1 to 16 octets
long.
VLAN policy
Each VLAN has an assigned policy value used to determine
whether a particular call connection can be established.
SFVLAN recognizes two policy values: Open and Secure.
2. SFVLAN Overview
Cabletron's SecureFast VLAN (SFVLAN) product implements a
distributed connection-oriented switching protocol that provides
fast forwarding of data packets at the MAC layer.
2.1 Features
Within a connection-oriented switching network, user traffic is
routed through the switch fabric based on the source and
destination address (SA/DA) pair found in the arriving packet.
For each SA/DA pair encountered by a switch, a "connection" is
programmed into the switch hardware. This connection maps the
SA/DA pair and the port on which the packet was received to a
specific outport over which the packet is to be forwarded. Thus,
D. Ruffen, et. al. Informational [Page 6]
once a connection has been established, all packets with a
particular SA/DA pair arriving on a particular inport are
automatically forwarded by the switch hardware out the specified
outport.
A distributed switching environment requires that each switch be
capable of processing all aspects of the call processing and
switching functionality. Thus, each switch must synchronize its
various databases with all other switches in the fabric or be
capable of querying other switches for information it does not
have locally.
SFVLAN accomplishes the above objectives by providing the
following features:
- A virtual directory of the entire switch fabric.
- Call processing for IP, IPX and MAC protocols.
- Automatic call connection, based on VLAN policy.
- Automatic call rerouting around failed switches and links.
In addition, SFVLAN optimizes traffic flow across the switch
fabric by providing the following features:
- Broadcast interception and address resolution at the ingress
port.
- Broadcast scoping, restricting the flooding of broadcast
packets to only those ports that belong to the same VLAN as the
packet source.
- A single loop-free path (spanning tree) used for the flooding
of undirected interswitch control messages. Only switches
running the SFVLAN switching protocol are included in this
spanning tree calculation -- that is, traditional bridges or
routers configured for bridging are not included.
- Interception of both service and route advertisements with
readvertisement sourced from the MAC address of the original
advertiser.
2.2 VLAN Principles
Each SFVLAN switch port, along with its attached endstations,
belongs to one or more virtual LANs (VLANs). A VLAN is a logical
grouping of ports and endstations such that all ports and
endstations in the VLAN appear to be on the same physical (or
D. Ruffen, et. al. Informational [Page 7]
extended) LAN segment even though they may be geographically
separated.
VLAN assignments are used to determine the validity of call
connection requests and to scope the broadcast of certain flooded
messages.
2.2.1 Default, Base and Inherited VLANs
Each port is explicitly assigned to a default VLAN. At start-up,
the default VLAN to which all ports are assigned is the base VLAN
-- a permanent, non-deletable VLAN to which all ports belong at
all times.
The network administrator can change the default VLAN of a port
from the base VLAN to any other unique VLAN by using a management
application known here as the VLAN Manager. A port's default VLAN
is persistent -- that is, it is preserved across a switch reset.
When an endstation attaches to a port for the first time, it
inherits the default VLAN of the port. Using the VLAN Manager,
the network administrator can reassign an endstation to another
VLAN.
Note
When all ports and all endstations belong to the base
VLAN, the switch fabric behaves like an 802.1D bridging
system.
2.2.2 VLAN Configuration Modes
For both ports and endstations, there are a variety of VLAN
configuration types, or modes.
2.2.2.1 Endstations
For endstations, there are two VLAN configuration modes:
inherited and static.
- Inherited
An inherited endstation becomes a member of its port's default
VLAN.
D. Ruffen, et. al. Informational [Page 8]
- Static
A static port becomes a member of the VLAN to which it has been
assigned by the VLAN Manager.
The default configuration mode for an endstation is inherited.
2.2.2.2 Ports
For ports, there are two VLAN configuration modes: normal and
locked.
- Normal
All inherited endstations on a normal port become members of
the port's default VLAN. All static endstations are members of
the VLAN to which they were mapped by the VLAN Manager.
If the VLAN Manager reassigns the default VLAN of a normal
port, the VLAN(s) for the attached endstations may or may not
change, depending on the VLAN configuration mode of each
endstation. All inherited endstations will become members of
the new default VLAN. All others will retain membership in
their previously mapped VLANs.
- Locked
All endstations attached to a locked port can be members only
of the port's default VLAN.
If the VLAN Manager reconfigures a normal port to be a locked
port, all endstations attached to the port become members of
the port's default VLAN, regardless of any previous VLAN
membership.
The default configuration mode for ports is normal.
2.2.2.3 Order of Precedence
On a normal port, static VLAN membership prevails over inherited
membership.
On a locked port, default VLAN membership prevails over any static
VLAN membership.
If a statically assigned endstation moves from a locked port back
to a normal port, the endstation's static VLAN membership must be
preserved.
D. Ruffen, et. al. Informational [Page 9]
2.2.3 Ports with Multiple VLAN Membership
A port can belong to multiple VLANs, based on the VLAN membership
of its attached endstations.
For example, consider a port with three endstations, a default
VLAN of "blue" and the following endstation VLAN assignments:
- One of the endstations is statically assigned to VLAN "red."
- Another endstation is statically assigned to VLAN "green."
- The third endstation inherits the default VLAN of "blue."
In this instance, the port is explicitly a member of VLAN "blue."
But note that it is also implicitly a member of VLAN "red" and
VLAN "green." Any tag-based flooding (Section 4.8) directed to
any one of the three VLANs ("red," "green," or "blue") will be
forwarded out the port.
2.3 Tag/Length/Value Method of Addressing
Within most computer networks, the concept of "address" is
somewhat elusive because different protocols can (and do) use
different addressing schemes and formats. For example, Ethernet
(physical layer) addresses are six octets long, while IP (network
layer) addresses are only four octets long.
To distinguish between the various protocol-specific forms of
addressing, many software modules within the SFVLAN product
specify addresses in a format known as Tag/Length/Value (TLV).
This format uses a variable-length construct as shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value length | |
+-+-+-+-+-+-+-+-+ +
| Address value |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Tag
This 4-octet field specifies the type of address contained in
the structure. The following address types are currently
supported:
D. Ruffen, et. al. Informational [Page 10]
Tag name Value Address type
aoMacDx 1 DX ethernet dst/src/type
aoIpxSap 2 Sap
aoIpxRIP 3 RIP
aoInstYP 4 YP (YP name and version)
aoInstUDP 5 UDP (Port #)
aoIpxIpx 6 Ipx
aoInetIP 7 IP (Net address)
aoInetRPC 8 RPC (Program #)
aoInetRIP 9 INET RIP
aoMacDXMcast 10 Multicast unknown type
aoAtDDP 11 AppleTalk DDP
aoEmpty 12 (no address type specified)
aoVlan 13 VLAN identifier
aoHostName 14 Host name
aoNetBiosName 15 NetBIOS name
aoNBT 16 NetBIOS on TCP name
aoInetIPMask 17 IP Subnet Mask
aoIpxSap8022 18 Sap 8022 type service
aoIpxSapSnap 19 Sap Snap type service
aoIpxSapEnet 20 Sap Enet type service
aoDHCPXID 21 DHCP Transaction ID
aoIpMcastRx 22 IP class D receiver
aoIpMcastTx 23 IP class D sender
aoIpxRip8022 24 Ipx Rip 8022 type service
aoIpxRipSnap 25 Ipx Rip type service
aoIpxRipEnet 26 Ipx Rip Enet service
aoATM 27 ATM
aoATMELAN 28 ATM LAN Emulation Name
Value length
This 1-octet field contains the length of the value of the
address. The value here depends on the address type and actual
value.
Address value
This variable-length field contains the value of the address.
The length of this field is stored in the Value length field.
2.4 Architectural Overview
The SFVLAN software executes in the switch CPU and consists of the
following elements as shown in Figure 1:
- The SFVLAN base services that handles traffic intercepted by
the switch hardware. The base services are described in
Section 3.
D. Ruffen, et. al. Informational [Page 11]
+------------------------------------------------------+
| +-----+ |
| +------------+ | I | |
| | CALL TAP <--(8)--> N | |
| +------------+ | T | |
| | E | |
| +-----------+ +------------+ | R | |
| | PATH | | TOPOLOGY | | S | |
| | | | | | W | |
| | Lnk state <------> Lnk state <--(3)--> I | | Flood path
| | | | | | T <----(5,7,8)-->
| | Span tree <------> Span tree <--(4)--> C | |
| +--^--------+ | | | H | |
| | | Discovery <--(2)--> | |
| | +------------+ | M | |
| | | E | |
| +------^--+ +--------+ | S | |
| | CONNECT >---------+--> FILTER | | S | |
| +--^------+ | +--------+ | A | | specific
| | | | G | | netwrk lnks
| | +--------^-+ +-------+ | E <----(2,3,4)-->
| +-------< POLICY | | FLOOD >--(7)--> | |
| +------^---+ +-^-----+ | P | |
| | | | R | |
| +-----------+ +-^-----------V-+ | O | |
| | DIRECTORY <----> RESOLVE <------(5)--> T | |
| +-----^-----+ +---^-----------+ | O | |
| | | | C | |
| | +---------^-----------+ | O | |
| +----< Base Services | | L | |
| +-----^---------------+ +-----+ |
+------------------|-----------------------------------+
Switch CPU |
| Host control port
+-----O----------------+
| ^ no cnx |
Layer 2 | | |
---------->O-----+--------------->O----------->
SA/DA pr | known cnx |
+----------------------+
Switch hardware
Figure 1: SFVLAN Architectural Overview
D. Ruffen, et. al. Informational [Page 12]
- Eight call processing service centers that provide the
essential services required to process call connections. The
call processing service centers are described in Section 4.
- A Call Tap module that supports the monitoring of call
connections. The Call Tap module is described in Section 5.
- The InterSwitch Message Protocol (ISMP) that provides a
consistent method of encapsulating and transmitting control
messages exchanged between SFVLAN switches. (Note that ISMP is
not a discrete software module. Instead, its functionality is
distributed among those service centers and software modules
that need to communicate with other switches in the fabric.)
The Interswitch Message Protocol and the formats of the
individual interswitch messages are described in Section 6.
3. Base Services
The SFVLAN base services act as the interface between the switch
hardware and the SFVLAN service centers running on the switch CPU.
This relationship is shown in Figure 2. This figure is a
replication of the bottom portion of Figure 1.
| Directory Resolve |
| ^ ^ |
| | | |
| | +---------^-----------+ |
| +----< Base Services | |
| +-----^---------------+ |
+-------------------|--------------------------+
Switch CPU |
| Host control port
+-----O----------------+
| ^ no cnx |
Layer 2 | | |
---------->O-----+--------------->O----------->
SA/DA pr | known cnx |
+----------------------+
Switch hardware
Figure 2: Base Services
During normal operation of the switch, data packets arriving at
any one of the local switch ports are examined in the switch
hardware. If the packet's source and destination address (SA/DA)
pair match a known connection, the hardware simply forwards the
packet out the outport specified by the connection.
D. Ruffen, et. al. Informational [Page 13]
If the SA/DA pair do not match any known connection, the hardware
diverts the packet to the host control port where it is picked up
by the SFVLAN base services. The base services generate a
structure known as a state box that tracks the progress of the
call connection request as the request moves through the call
processing service centers.
After creating the call's state box, the base services check to
determine if the call is a duplicate of a call already being
processed. If not, a request is issued to the Directory Service
Center (Section 4.1) to add the call's source address to the local
Node and Alias Tables. The base services then hand the call off to
the Resolve Service Center (Section 4.3) for further processing.
4. Call Processing
Call connection processing is handled by a set of eight service
centers, each with one or more servers. The servers within a
service center are called in a particular sequence. Each server
records the results of its processing in the call connection
request state box and passes the state box to the next server in
the sequence.
In the sections that follow, servers are listed in the order in
which they are called.
4.1 Directory Service Center
The Directory Service Center is responsible for cataloging the MAC
addresses and alias information for both local and remote
endstations. The information is stored in two tables -- the Node
Table and the Alias Table.
- The Node Table contains the MAC addresses of endstations
attached to the local switch. It also contains a cache of
remote endstations detected by the Resolve Service Center
(Section 4.3). Every entry in the Node Table has one or more
corresponding entries in the Alias Table.
- The Alias Table contains protocol alias information for each
endstation. An endstation alias can be a network address (such
as an IP or IPX address), a VLAN identifier, or any other
protocol identifier. Since every endstation is a member of at
least one VLAN (the default VLAN for the port), there is always
at least one entry in the Alias Table for each entry in the
Node Table.
D. Ruffen, et. al. Informational [Page 14]
Note
The Node and Alias Tables must remain synchronized.
That is, when an endstation's final alias is removed
from the Alias Table, the endstation entry is removed
from the Node Table.
Note that the total collection of all Node Tables and Alias Tables
across all switches is known as the "virtual" directory of the
switch fabric. The virtual directory contains address mappings of
all known endstations in the fabric.
4.1.1 Local Add Server
The Directory Local Add server adds entries to the local Node or
Alias Tables. It is called by the base services (Section 3) to
add a local endstation and by the Interswitch Resolve (Section
4.3.4) server to add an endstation discovered on a remote switch.
4.1.2 Inverse Resolve Server
The Directory Inverse Resolve server is invoked when a new
endstation has been discovered on the local switch (that is, when
the Local Add server was successful in adding the endstation).
The server provides two functions:
- It populates the Node and Alias Tables with local entries
during switch initialization.
- It processes a new endstation discovered after the fabric
topology has converged to a stable state.
In both instances, the processing is identical.
When a new endstation is detected on one of the switch's local
ports, the Inverse Resolve server sends an Interswitch New User
request message (Section 6.5) over the switch flood path to all
other switches in the fabric. The purpose of the Interswitch New
User request is two-fold:
- It informs the other switches of the new endstation address.
Any entries for that endstation in the local databases of other
switches should be dealt with appropriately.
- It requests information about any static VLAN(s) to which the
endstation has been assigned.
When a switch receives an Interswitch New User request message
from one of its upstream neighbors, it first forwards the message
D. Ruffen, et. al. Informational [Page 15]
to all its downstream neighbors. No actual processing or VLAN
resolution is attempted until the message reaches the end of the
switch flood path and begins its trip back along the return path.
This ensures that all switches in the fabric receive notification
of the new user and have synchronized their databases.
If a switch receives an Interswitch New User request message but
has no downstream neighbors, it does the following:
- If the endstation was previously connected to one of the
switch's local ports, the switch formulates an Interswitch New
User Response message by loading the VLAN identifier(s) of the
static VLAN(s) to which the endstation was assigned, along with
its own MAC address. (VLAN identifiers are stored in
Tag/Length/Value (TLV) format. See Section 2.3.) The switch
then sets the message status field to NewUserAck, and returns
the message to its upstream (requesting) neighbor.
Otherwise, the switch sets the status field to NewUserUnknown
and returns the message to its upstream neighbor.
- The switch then deletes the endstation from its local database,
as well as any entries associated with the endstation in its
connection table.
When a switch forwards an Interswitch New User request message to
its downstream neighbors, it keeps track of the number of requests
it has sent out and does not respond back to its upstream neighbor
until all requests have been responded to.
- As each response is received, the switch checks the status
field of the message. If the status is NewUserAck, the switch
retains the information in that response. When all requests
have been responded to, the switch returns the NewUserAck
response to its upstream neighbor.
- If all the Interswitch New User Request messages have been
responded to with a status of NewUserUnknown, the switch checks
to see if the endstation was previously connected to one of its
local ports. If so, the switch formulates an Interswitch New
User Response message by loading the VLAN identifier(s) of the
static VLAN(s) to which the endstation was assigned, along with
its own MAC address. The switch then sets the message status
field to NewUserAck, and returns the message to its upstream
(requesting) neighbor.
Otherwise, the switch sets the status field to NewUserUnknown
and returns the message to its upstream neighbor.
D. Ruffen, et. al. Informational [Page 16]
- The switch then deletes the endstation from its local database,
as well as any entries associated with the endstation in its
connection table.
When the originating switch has received responses to all the
Interswitch New User Request messages it has sent, it does the
following:
- If it has received a response message with a status of
NewUserAck, it loads the new VLAN information into its local
database.
- If all responses have been received with a status of
NewUserUnknown, the originating switch assumes that the
endstation was not previously connected anywhere in the network
and assigns it to a VLAN according to the VLAN membership rules
and order of precedence.
If any Interswitch New User Request message has not been responded
to within a certain predetermined time (currently 5 seconds), the
originating switch recalculates the switch flood path and resends
the Interswitch New User Request message.
4.1.3 Local Delete Server
The Directory Local Delete server removes entries (both local and
remote) from the local Node and Alias Tables. It is invoked when
an endstation, previously known to be attached to one switch, has
been moved and discovered on another switch.
Note also that remote entries are cached and are purged from the
tables on a first-in/first-out basis as space is needed in the
cache.
4.2 Topology Service Center
The Topology Service Center is responsible for maintaining three
databases relating to the topology of the switch fabric:
- The topology table of SFVLAN switches that are physical
neighbors to the local switch.
- The spanning tree that defines the loop-free switch flood path
used for transmitting undirected interswitch messages.
- The directed graph that is used to calculate the best path(s)
for call connections.
D. Ruffen, et. al. Informational [Page 17]
4.2.1 Neighbor Discovery Server
The Topology Neighbor Discovery server uses Interswitch Keepalive
messages to detect the switch's neighbors and establish the
topology of the switching fabric. Interswitch Keepalive messages
are exchanged in accordance with Cabletron's VlanHello protocol,
described in detail in [IDhello].
4.2.2 Spanning Tree Server
The Topology Spanning Tree server is invoked by the Topology
Neighbor Discovery server when a neighboring SFVLAN switch is
either discovered or lost -- that is, when the operational status
of a network link changes.
The Spanning Tree server exchanges interswitch messages with
neighboring SFVLAN switches to calculate the switch flood path
over which undirected interswitch messages are sent. There are
two parts to this process:
- Creating and maintaining the spanning tree
- Remote blocking
4.2.2.1 Creating and Maintaining the Spanning Tree
In a network with redundant network links, a packet traveling
between switches can potentially be caught in an infinite loop --
an intolerable situation in a networking environment. However, it
is possible to reduce a network topology to a single configuration
(known as a spanning tree) such that there is, at most, one path
between any two switches.
Within the SFVLAN product, the spanning tree is created and
maintained using the Spanning Tree Algorithm defined by the IEEE
802.1d standard.
Note
A detailed discussion of this algorithm is beyond the
scope of this document. See [IEEE] for more information.
To implement the Spanning Tree Algorithm, SFVLAN switches exchange
Interswitch BPDU messages (Section 6.2) containing encapsulated
IEEE-compliant 802.2 Bridge Protocol Data Units (BPDUs). There
are two types of BPDUs:
- Configuration (CFG) BPDUs are exchanged during the switch
discovery process, following the receipt of an Interswitch
D. Ruffen, et. al. Informational [Page 18]
Keepalive message. They are used to create the initial the
spanning tree.
- Topology Change Notification (TCN) BPDUs are exchanged when
changes in the network topology are detected. They are used to
redefine the spanning tree to reflect the current topology.
See [IEEE] for detailed descriptions of these BPDUs.
4.2.2.2 Remote Blocking
After the spanning tree has been computed, each network port on an
SFVLAN switch will be in one of two states:
- Forwarding. A port in the Forwarding state will be used to
transmit all ISMP messages.
- Blocking. A port in the Blocking state will not be used to
forward undirected ISMP messages. Blocking the rebroadcast of
these messages on selected ports prevents message duplication
arising from multiple paths that exist in the network topology.
Note that all other types of ISMP message will be transmitted.
Note
The IEEE 802.1d standard specifies other port states
used during the initial creation of the spanning tree.
These states are not relevant to the discussion here.
Note that although a port in the Blocking state will not forward
undirected ISMP messages, it may still receive them. Any such
message received will ultimately be discarded, but at the cost of
CPU time necessary to process the packet.
To prevent the transmission of undirected messages to a port, the
port's owner switch can set remote blocking on the link by sending
an Interswitch Remote Blocking message (Section 6.3) out over the
port. This notifies the switch on the other end of the link that
undirected messages should not be sent over the link, regardless
of the state of the sending port.
Each SFVLAN switch sends an Interswitch Remote Blocking message
out over all its blocked network ports every 5 seconds. A flag
within the message indicates whether remote blocking should be
turned on or off over the link.
D. Ruffen, et. al. Informational [Page 19]
4.2.3 Link State Server
The Topology Link State server is invoked by any process that
detects a change in the state of the network links of the local
switch. These changes include (but are not limited to) changes in
operational or administrative status of the link, path "cost" or
bandwidth.
The Link State server runs Cabletron's Virtual LAN Link State
(VLS) protocol which exchanges interswitch messages with
neighboring SFVLAN switches to calculate the set of best paths
between the local switch and all other switches in the fabric.
(The VLS protocol is described in detail in [IDvlsp].)
The Link State server also notifies the Connect Service Center
(Section 4.5) of any remote links that have failed, thereby
necessitating potential tear-down of current connections.
4.3 Resolve Service Center
The Resolve Service Center is responsible for resolving the
destination address of broadcast data packets (such as an IP ARP
packet) to a unicast MAC address to be used in mapping the call
connection. To do this, the Resolve Service Center attempts to
resolve such broadcast packets directly at the access port of the
ingress switch.
Address resolution is accomplished as follows:
1) First, an attempt is made to resolve the address from the
switch's local databases by calling the following servers:
- The Table server attempts to resolve the address from the
Resolve Table (Section 4.3.1).
- Next, the Local server attempts to resolve the address from
the Node and Alias Tables (Section 4.3.2).
- If the address is not found in these tables but is an IP
address, the Resolve Subnet server (Section 4.3.3) is also
called.
2) If the address cannot be resolved locally, the Interswitch
Resolve server (Section 4.3.4) is called to access the "virtual
directory" by sending an Interswitch Resolve request message
out over the switch flood path.
3) If the address cannot be resolved either locally or via an
Interswitch Resolve message -- that is, the destination
endstation is unknown to any switch, perhaps because it has
D. Ruffen, et. al. Informational [Page 20]
never transmitted a packet to its switch -- the following steps
are taken:
- The Unresolvable server (Section 4.3.5) is called to record
the unresolved packet.
- The Block server (Section 4.3.6) is called to determine
whether the address should be added to the Block Table.
- The Flood Service Center (Section 4.8) is called to broadcast
the packet to other SFVLAN switches using a tag-based
flooding mechanism.
4.3.1 Table Server
The Resolve Table server maintains the Resolve Table which
contains a collection of addresses that might not be resolvable in
the normal fashion. This table typically contains such things as
the addresses of "quiet" devices that do not send data packets or
special mappings of IP addresses behind a router. Entries can be
added to or deleted from the Resolve Table via an external
management application.
4.3.2 Local Server
The Resolve Local server checks the Node and Alias Tables
maintained by the Directory Service Center (Section 4.1) to
determine if it can resolve the address.
4.3.3 Subnet Server
If the address to be resolved is an IP address but cannot be
resolved via the standard processing described above, the Resolve
Subnet server applies the subnet mask to the IP address and then
does a lookup in the Resolve Table.
4.3.4 Interswitch Resolve Server
If the address cannot be resolved locally, the Interswitch Resolve
server accesses the "virtual directory" by sending an Interswitch
Resolve request message (Section 6.4) out over the switch flood
path. The Interswitch Resolve request message contains the
destination address as it was received within the packet, along
with a list of requested addressing information.
When a switch receives an Interswitch Resolve request message from
one of its upstream neighbors, it checks to see if the destination
D. Ruffen, et. al. Informational [Page 21]
endstation is connected to one of its local access ports. If so,
it formulates an Interswitch Resolve response message by filling
in the requested address information, along with its own MAC
address. It then sets the message status field to ResolveAck, and
returns the message to its upstream (requesting) neighbor.
If the receiving switch cannot resolve the address, it forwards
the Interswitch Resolve request message to its downstream
neighbors. If the switch has no downstream neighbors, it sets the
message status field to Unknown, and returns the message to its
upstream (requesting) neighbor.
When a switch forwards an Interswitch Resolve request message to
its downstream neighbors, it keeps track of the number of requests
it has sent out and received back. It will only respond back to
its upstream (requesting) neighbor when one of the following
conditions occurs:
- It receives any response with a status of ResolveAck
- All downstream neighbors have responded with a status of Unknown
Any Interswitch Resolve request message that is not responded to
within a certain predetermined time (currently 5 seconds) is
assumed to have a response status of Unknown.
When the Interswitch Resolve server receives a successful
Interswitch Resolve response message, it records the resolved
address information in the remote cache of its local directory for
use in resolving later packets for the same endstation. Note that
this process results in each switch building its own unique copy
of the virtual directory containing only the endstation addresses
in which it is interested.
4.3.5 Unresolvable Server
The Unresolvable server is called when a packet destination
address cannot be resolved. The server records the packet in a
table that can then be examined to determine which endstations are
generating unresolvable traffic.
Also, if a particular destination is repeatedly seen to be
unresolvable, the server calls the Block server (Section 4.3.6) to
determine whether the address should be blocked.
4.3.6 Block Server
The Resolve Block server is called when a particular destination
has been repeatedly seen to be unresolvable. This typically
D. Ruffen, et. al. Informational [Page 22]
happens when, unknown to the packet source, the destination
endstation is either not currently available or no longer exists.
If the Block server determines that the unresolved address has
exceeded a configurable request threshold, the address is added to
the server's Block Table. Interswitch Resolve request messages
for addresses listed in the Block Table are sent less frequently,
thereby reducing the amount of Interswitch Resolve traffic
throughout the fabric.
If an address listed in the Block Table is later successfully
resolved by and Interswitch Resolve request message, the address
is removed from the table.
4.4 Policy Service Center
Once the destination address of the call packet has been resolved,
the Policy Service Center is called to determine the validity of
the requested call connection based on the VLAN policy of the
source and destination VLANs.
4.4.1 Unicast Rules Server
The Policy Unicast Rules server recognizes two VLAN policy values:
Open or Secure. The default policy for all VLANs is Open.
The policy value is used as follows when determining the validity
of a requested call connection:
- If the VLAN policy of either the source or destination cannot
be determined, the Filter Service Center is called to establish
a filter (i.e., blocked) for the SA/DA pair.
- If the source and destination endstations belong to the same
VLAN, then the connection is permitted regardless of the VLAN
policy.
- If the source and destination endstations belong to different
VLANs, but both VLANs are running with an Open policy, then the
connection is permitted, providing cut-through switching
between different VLAN(s).
- If the source and destination endstations belong to different
VLANs and one or both of the VLANs are running with a Secure
policy, then the Flood Service Center (Section 4.8) is called
to broadcast the packet to other SFVLAN switches having ports
or endstations that belong to the same VLAN as the packet
source.
D. Ruffen, et. al. Informational [Page 23]
Note that if any of the VLANs to which the source or destination
belong has a Secure policy, then the policy used in the above
algorithm is Secure.
4.5 Connect Service Center
Once the Policy Service Center (Section 4.4) has determined that a
requested call connection is valid, the Connect Service Center is
called to set up the connection. Note that connectivity between
two endstations within the fabric is established on a switch-by-
switch basis as the call progresses through the fabric toward its
destination. No synchronization is needed between switches to
establish an end-to-end connection.
The Connect Service Center maintains a Connection Table containing
information for all connections currently active on the switch's
local ports.
Connections are removed from the Connection Table when one of the
endstations is moved to a new switch (Section 4.1.2) or when the
Topology Link State server (Section 4.2.3) notifies the Connect
Service Center that a network link has failed. Otherwise,
connections are not automatically aged out or removed from the
Connection Table until a certain percentage threshold (HiMark) of
table capacity is reached and resources are needed. At that
point, some number of connections (typically 100) are aged out and
removed at one time.
4.5.1 Local Server
If the destination endstation resides on the local switch, the
Connect Local server establishes a connection between the source
and destination ports. Note that if the source and destination
both reside on the same physical port, a filter connection is
established by calling the Filter Service Center (Section 4.6).
4.5.2 Link State Server
The Connect Link State server is called if the destination
endstation of the proposed connection does not reside on the local
switch.
The server executes a call to the Path Link State server (Section
4.7.1) which returns up to three "best" paths of equal cost from
the local switch to the destination switch. If more than one path
is returned, the server chooses a path that provides the best load
balancing of user traffic across the fabric.
D. Ruffen, et. al. Informational [Page 24]
4.5.3 Directory Server
The Connect Directory server is called if the Connect Link State
server is unable to provide a path for some reason.
The server examines the local directory to determine on which
switch the destination endstation resides. If the port of access
to the destination switch is known, then a connection is
established using that port as the outport of the connection.
4.6 Filter Service Center
The Filter Service Center is responsible for establishing filtered
connections. This service center is called by the Connect Local
server (Section 4.5.1) if the source and destination endstations
reside on the same physical port, and by the Policy Service Center
(Section 4.4) if the VLAN of either the source or destination is
indeterminate.
A filter connection is programmed in the switch hardware with no
specified outport. That is, the connection is programmed to
discard any traffic for that SA/DA pair.
4.7 Path Service Center
The Path Service Center is responsible for determining the path
from a source to a destination.
4.7.1 Link State Server
The Path Link State server is called by the Connect Link State
server (Section 4.5.2) to return up to three best paths of equal
cost between a source and destination pair of endstations. These
best paths are calculated by the Topology Link State server
(Section 4.2.3).
The Path Link State server is also called by the Connect Service
Center to return a complete source-to-destination path consisting
of a list of individual switch port names. A switch port name
consists of the switch base MAC address and a port instance
relative to the switch.
4.7.2 Spanning Tree Server
The Path Spanning Tree server is called by any server needing to
forward an undirected message out over the switch flood path. The
server returns a port mask indicating which local ports are
D. Ruffen, et. al. Informational [Page 25]
currently enabled as outports of the switch flood path. The
switch flood path is calculated by the Topology Spanning Tree
server (Section 4.2.2).
4.8 Flood Service Center
If the Resolve Service Center (Section 4.3) is unable to resolve
the destination address of a packet, it invokes the Flood Service
Center to broadcast the unresolved packet.
4.8.1 Tag-Based Flood Server
The Tag-Based Flood server encapsulates the unresolved packet into
an Interswitch Tag-Based Flood message (Section 6.6), along with a
list of Virtual LAN identifiers specifying those VLANs to which
the source endstation belongs. The message is then sent out over
the switch flood path to all other switches in the fabric.
When a switch receives an Interswitch Tag-Based Flood message, it
examines the encapsulated header to determine the VLAN(s) to which
the packet should be sent. If any of the switch's local access
ports belong to one or more of the specified VLANs, the switch
strips off the tag-based header and forwards the original packet
out the appropriate access port(s).
The switch also forwards the entire encapsulated packet along the
switch flood path to its downstream neighboring switches, if any.
5. Monitoring Call Connections
The SecureFast VLAN product permits monitoring of user traffic
moving between two endstations by establishing a call tap on the
connection between the two stations. Traffic can be monitored in
one or both directions along the connection path.
5.1 Definitions
In addition to the terms defined in Section 1.2, the following
terms are used in this description of the call tap process.
Originating Switch
The originating switch is the switch that requests the call
tap. Any switch along a call connection path may request a tap
on that call connection.
D. Ruffen, et. al. Informational [Page 26]
Probe
The tap probe is the device to receive a copy of the call
connection data. The probe is attached to a port on the probe
switch.
Probe Switch
The probe switch (also known as the terminating switch) is the
switch to which the probe is attached. The probe switch can be
anywhere in the topology.
5.2 Tapping a Connection
A request to tap a call connection between two endstations can
originate on any switch along the call connection path -- the
ingress switch, the egress switch, or any of the intermediate
switches. The call connection must have already been established
before a call tap request can be issued. The probe device can be
attached to any switch in the topology.
5.2.1 Types of Tap Connections
A call tap is enabled by setting up an auxiliary tap connection
associated with the call being monitored. Since the tap must
originate on a switch somewhere along the call connection path,
the tap connection path will pass through one or more of the
switches along the call path. However, since the probe switch can
be anywhere in the switch fabric, the tap path and the call path
may diverge at some point.
Therefore, on each switch along the tap path, the tap connection
is established in one of three ways:
- The existing call connection is used with no modification.
When both the call path and tap path pass through the switch,
and the inport and outports of both connections are identical,
the switch uses the existing call connection to route the tap.
- The existing call connection is modified.
When both the call path and tap path pass through the switch,
but the call path outport is different from the tap path
outport, the switch enables an extra outport in either one or
both directions of the call connection, depending on the
direction of the tap. This happens under two conditions.
D. Ruffen, et. al. Informational [Page 27]
- If the switch is also the probe switch, an extra outport is
enabled to the probe.
- If the switch is the point at which the call path and the tap
path diverge, an extra outport is enabled to the downstream
neighbor on that leg of the switch flood path on which the
probe switch is located.
- A new connection is established.
If the call path does not pass through the switch (because the
tap path has diverged from the call path), a completely new
connection is established for the tap.
5.2.2 Locating the Probe and Establishing the Tap Connection
To establish a call tap, the originating switch formats an
Interswitch Tap request message (Section 6.7) and sends it out
over the switch flood path to all other switches in the topology.
Note
If the originating switch is also the probe switch, no
Interswitch Tap request message is necessary.
As the Interswitch Tap request message travels out along the
switch flood path, each switch receiving the message checks to see
if it is the probe switch and does the following:
- If the switch is the probe switch, it establishes the tap
connection by either setting up a new connection or modifying
the call connection, as appropriate (see Section 5.2.1). It
then reformats the Tap request message to be a Tap response
message with a status indicating that the probe has been found,
and sends the message back to its upstream neighbor.
- If the switch is not the probe switch, it forwards the Tap
request message to all its downstream neighbors (if any).
- If the switch is not the probe switch and has no downstream
neighbors, it reformats the Tap request message to be a Tap
response message with a status indicating that the probe is not
located on that leg of the switch flood path. It then sends
the response message back to its upstream neighbor.
When a switch forwards an Interswitch Tap request message to its
downstream neighbors, it keeps track of the number of requests it
has sent out.
D. Ruffen, et. al. Informational [Page 28]
- If a response is received with a status indicating that the
probe switch is located somewhere downstream, the switch
establishes the appropriate type of tap connection (see Section
5.2.1). It then formats a Tap response message with a status
indicating that the probe has been found and passes the message
to its upstream neighbor.
- If no responses are received with a status indicating that the
probe switch is located downstream, the switch formats a Tap
response message with a status indicating that the probe has
not been found and passes the message to its upstream neighbor.
5.2.3 Status Field
The status field of the Interswitch Tap request/response message
contains information about the state of the tap. Some of these
status values are transient and are merely used to track the
progress of the tap request. Other status values are stored in
the tap table of each switch along the tap path for use when the
tap is torn down. The possible status values are as follows:
- StatusUnassigned. This is the initial status of the
Interswitch Tap request message.
- OutportDecisionUnknown. The tap request is still moving
downstream along the switch flood path. The probe switch had
not yet been found.
- ProbeNotFound. The probe switch is not located on this leg of
the switch flood path.
- DisableOutport. The probe switch is located on this leg of the
switch flood path, and the switch has had to either modify the
call connection or establish a new connection to implement the
tap (see Section 5.2.1). When the tap is torn down, the switch
will have to disable any additional outports that have been
enabled for the tap.
- KeepOutport. The probe switch is located on this leg of the
switch flood path, and the switch was able to route the tap
over the existing call path (see Section 5.2.1). Any ports
used for the tap will remain enabled when the tap is torn down.
D. Ruffen, et. al. Informational [Page 29]
5.3 Untapping a Connection
A request to untap a call connection must be issued on the tap
originating switch -- that is, the same switch that issued the tap
request.
To untap a call connection, the originating switch sends an
Interswitch Untap request message (Section 6.7) out over the
switch flood path to all other switches in the topology. The
message is sent over the switch flood path, rather than the tap
connection path, to ensure that all switches that know of the tap
are properly notified, even if the switch topology has changed
since the tap was established.
When a switch receives an Interswitch Untap request message, it
checks to see if it is handling a tap for the specified call
connection. If so, the switch disables the tap connection, as
follows:
- If a new connection was added for the tap, the connection is
deleted from the connection table.
- If additional outports were enabled on the call connection,
they are disabled.
The switch then forwards the Interswitch Untap request message to
its downstream neighbor (if any). If the switch has no downstream
neighbors, it formats an untap response and sends the message back
to its upstream neighbor.
When a switch forwards an Interswitch Untap request message to its
downstream neighbors, it keeps track of the number of requests it
has sent out and does not respond back to its upstream neighbor
until all untap requests have been responded to. Once all
responses have been received, the switch handles any final cleanup
for the tap and then sends a single Interswitch Untap response
message to its upstream neighbor.
D. Ruffen, et. al. Informational [Page 30]
6. Interswitch Message Protocol (ISMP)
The InterSwitch Message protocol (ISMP) provides a consistent
method of encapsulating and transmitting messages exchanged
between switches to create and maintain the databases and provide
other control services and functionality required by the SFVLAN
product.
6.1 General Packet Structure
ISMP packets are of variable length and have the following general
structure:
- Frame header
- ISMP packet header
- ISMP message body
Each of these packet segments is discussed separately in the
following subsections.
6.1.1 Frame Header
ISMP packets are encapsulated within an IEEE 802-compliant frame
using a standard header as shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Destination address +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
04 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Source address +
08 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 | Type | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
16 | |
+ +
: :
Destination address
This 6-octet field contains the Media Access Control (MAC)
address of the multicast channel over which all switches in the
fabric receive ISMP packets. Except where otherwise noted,
this field contains the multicast address of the control
channel over which all switches in the fabric receive ISMP
packets -- a value of 01-00-1D-00-00-00.
D. Ruffen, et. al. Informational [Page 31]
Source address
Except where otherwise noted, this 6-octet field contains the
physical (MAC) address of the switch originating the ISMP
packet.
Type
This 2-octet field identifies the type of data carried within
the frame. Except where otherwise noted, the type field of
ISMP packets contains the value 0x81FD.
6.1.2 ISMP Packet Header
There are two versions of the ISMP packet header in use by the
SecureFast VLAN product.
6.1.2.1 Version 2
The version 2 ISMP packet header consists of 6 octets, as shown
below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 |///////////////////////////////////////////////////////////////|
://////// Frame header /////////////////////////////////////////:
+//////// (14 octets) /////////+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
12 |///////////////////////////////| Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
16 | ISMP message type | Sequence number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | |
+ +
: :
Frame header
This 14-octet field contains the frame header (Section 6.1.1).
Version
This 2-octet field contains the version number of the
InterSwitch Message Protocol to which this ISMP packet adheres.
This document describes ISMP Version 2.0.
D. Ruffen, et. al. Informational [Page 32]
ISMP message type
This 2-octet field contains a value indicating which type of
ISMP message is contained within the message body. The
following table lists each ISMP message, along with its message
type and the section within this document that describes the
message in detail:
Message Name Type Description
Interswitch Link State message 3 See note below
Interswitch BPDU message 4 Section 6.2
Interswitch Remote Blocking message 4 Section 6.3
Interswitch Resolve message 5 Section 6.4
Interswitch New User message 5 Section 6.5
Interswitch Tag-Based Flood message 7 Section 6.6
Interswitch Tap/Untap message 8 Section 6.7
Note
The Link State messages used by the VLS Protocol are
not described in this document. For a detailed
description of these messages, see [IDvlsp].
Sequence number
This 2-octet field contains an internally generated sequence
number used by the various protocol handlers for internal
synchronization of messages.
6.1.2.2 Version 3
The version 3 ISMP packet header is used only by the Interswitch
Keepalive message. That message is not described in this
document. For a detailed description of the version 3 ISMP packet
header, see [IDhello].
6.1.3 ISMP Message Body
The ISMP message body is a variable-length field containing the
actual data of the ISMP message. The length and content of this
field are determined by the value found in the message type field.
See the following sections for the exact format of each message
type.
D. Ruffen, et. al. Informational [Page 33]
6.2 Interswitch BPDU Message
The Interswitch BPDU message consists of a variable number of
octets, as shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Frame header / +
: ISMP packet header (type 4) :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | Version | Opcode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Message flags | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
28 | |
: BPDU packet :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Frame header/ISMP packet header
This 20-octet field contains the frame header and the ISMP
packet header.
Version
This 2-octet field contains the version number of the message
type. This document describes ISMP message type 4, version 1.
Opcode
This 2-octet field contains the operation type of the message.
For an Interswitch BPDU message, the value should be 1.
Message flags
This 2-octet field is currently unused. It is reserved for
future use.
BPDU packet
This variable-length field contains an IEEE-compliant 802.2
Bridge Protocol Data Unit. See [IEEE] for a detailed
description of the contents of this field.
D. Ruffen, et. al. Informational [Page 34]
6.3 Interswitch Remote Blocking Message
The Interswitch Remote Blocking message consists of 30 octets, as
shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Frame header / +
: ISMP packet header (type 4) :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | Version | Opcode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Message flags | Blocking flag ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 | ... Blocking flag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Frame header/ISMP packet header
This 20-octet field contains the frame header and the ISMP
packet header.
Version
This 2-octet field contains the version number of the message
type. This document describes ISMP message type 4, version 1.
Opcode
This 2-octet field contains the operation type of the message.
Valid values are as follows:
2 Enable/disable remote blocking
3 Acknowledge previously received Remote Blocking message
Message flags
This 2-octet field is currently unused. It is reserved for
future use.
Blocking flag
This 4-octet field contains a flag indicating the state of
remote blocking on the link over which the message was
received. A value of 1 indicates remote blocking is on and no
undirected ISMP messages should be sent over the link. A value
of 0 indicates remote blocking is off. This flag is irrelevant
if the operation type (Opcode) of the message has a value of 3.
D. Ruffen, et. al. Informational [Page 35]
6.4 Interswitch Resolve Message
There are two versions of the Interswitch Resolve message used by
the SecureFast VLAN product.
6.4.1 Prior to Version 1.8
The Interswitch Resolve message used by SFVLAN prior to version
1.8 consists of a variable number of octets, as shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Frame header / +
: ISMP packet header (type 5) :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | Version | Opcode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Status | Call Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 | |
+ Source MAC of packet +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Originating switch MAC +
36 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 | |
+ Owner switch MAC +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
44 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
48 | |
: Known destination address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n | Count | |
+-+-+-+-+-+-+-+-+ +
n+4 | Resolve list |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n = 46 + length of known address TLV
In the following description of the message fields, the term
"originating" switch refers to the switch that issued the original
Interswitch Resolve request. The term "owner" switch refers to
that switch to which the destination endstation is attached. And
D. Ruffen, et. al. Informational [Page 36]
the term "responding" switch refers to either the "owner" switch
or to a switch at the end of the switch flood path that does not
own the endstation but issues an Interswitch Resolve response
because it has no downstream neighbors.
With the exception of the resolve list (which has a different size
and format in a Resolve response message), all fields of an
Interswitch Resolve message are allocated by the originating
switch, and unless otherwise noted below, are written by the
originating switch.
Frame header/ISMP packet header
This 20-octet field contains the frame header and the ISMP
packet header.
Version
This 2-octet field contains the version number of the message
type. This document describes ISMP message type 5, version 1.
Opcode
This 2-octet field contains the operation code of the message.
Valid values are as follows:
1 The message is a Resolve request.
2 The message is a Resolve response.
3 (unused in Resolve messages)
4 (unused in Resolve messages)
The originating switch writes a value of 1 to this field, while
the responding switch writes a value of 2.
Status
This 2-octet field contains the status of a Resolve response
message. Valid values are as follows:
0 The Resolve request succeeded (ResolveAck).
1 (unused)
2 The Resolve request failed (Unknown).
This field is written by the responding switch.
Call tag
This 2-octet field contains the call tag of the endstation
packet for which this Resolve request is issued. The call tag
is a 16-bit value (generated by the originating switch) that
uniquely identifies the packet.
D. Ruffen, et. al. Informational [Page 37]
Source MAC of packet
This 6-octet field contains the physical (MAC) address of the
endstation that originated the packet identified by the call
tag.
Originating switch MAC
This 6-octet field contains the physical (MAC) address of the
switch that issued the original Resolve request.
Owner switch MAC
This 6-octet field contains the physical (MAC) address of the
switch to which the destination endstation is attached -- that
is, the switch that was able to resolve the requested
addressing information. This field is written by the owner
switch.
If the status of the response is Unknown, this field is
irrelevant.
Known destination address
This variable-length field contains the known attribute of the
destination endstation address. This address is stored in
Tag/Length/Value format. (See Section 2.3.)
Count
This 1-octet field contains the number of address attributes
requested or returned. This is the number of items in the
resolve list.
Resolve list
This variable-length field contains a list of the address
attributes either requested by the originating switch or
returned by the owner switch. Note that in a Resolve request
message, this list contains only the tags of the requested
address attributes (see Section 2.3). On the other hand, a
Resolve response message with a status of ResolveAck contains
the full TLV of each resolved address attribute. The number of
entries in the list is specified in the count field.
In an Interswitch Resolve response message, this field is
irrelevant if the status of the response is Unknown.
D. Ruffen, et. al. Informational [Page 38]
6.4.2 Version 1.8
The Interswitch Resolve message used by SFVLAN version 1.8
consists of a variable number of octets, as shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Frame header / +
: ISMP packet header (type 5) :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | Version | Opcode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Status | Call Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 | |
+ Source MAC of packet +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Originating switch MAC +
36 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 | |
+ Owner switch MAC +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
44 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
48 | |
: Known destination address :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n | Count | |
+-+-+-+-+-+-+-+-+ +
n+4 | Resolve list |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n1 | |
+ Actual dest switch MAC +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Downlink chassis MAC +
n1+8 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n1+12 | |
+ Actual chassis MAC +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
n1+20 | |
+ Domain name +
: :
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
D. Ruffen, et. al. Informational [Page 39]
n = 46 + length of known address TLV
n1 = n + length of Resolve list
In the following description of the message fields, the term
"originating" switch refers to the switch that issued the original
Interswitch Resolve request. The term "owner" switch refers to
that switch to which the destination endstation is attached. And
the term "responding" switch refers to either the "owner" switch
or to a switch at the end of the switch flood path that does not
own the endstation but issues an Interswitch Resolve response
because it has no downstream neighbors.
With the exception of the resolve list (which has a different size
and format in a Resolve response message) and the four fields
following the resolve list, all fields of an Interswitch Resolve
message are allocated by the originating switch, and unless
otherwise noted below, are written by the originating switch.
Frame header/ISMP packet header
This 20-octet field contains the frame header and the ISMP
packet header.
Version
This 2-octet field contains the version number of the message
type. This section describes version 3 of the Interswitch
Resolve message.
Opcode
This 2-octet field contains the operation code of the message.
Valid values are as follows:
1 The message is a Resolve request.
2 The message is a Resolve response.
3 (unused in Resolve messages)
4 (unused in Resolve messages)
The originating switch writes a value of 1 to this field, while
the responding switch writes a value of 2.
Status
This 2-octet field contains the status of a Resolve response
message. Valid values are as follows:
0 The Resolve request succeeded (ResolveAck).
1 (unused)
2 The Resolve request failed (Unknown).
This field is written by the responding switch.
D. Ruffen, et. al. Informational [Page 40]
Call tag
This 2-octet field contains the call tag of the endstation
packet for which this Resolve request is issued. The call tag
is a 16-bit value (generated by the originating switch) that
uniquely identifies the packet.
Source MAC of packet
This 6-octet field contains the physical (MAC) address of the
endstation that originated the packet identified by the call
tag.
Originating switch MAC
This 6-octet field contains the physical (MAC) address of the
switch that issued the original Resolve request.
Owner switch MAC
This 6-octet field contains the physical (MAC) address of the
switch to which the destination endstation is attached -- that
is, the switch that was able to resolve the requested
addressing information. This field is written by the owner
switch.
If the status of the response is Unknown, this field is
irrelevant.
Known destination address
This variable-length field contains the known attribute of the
destination endstation address. This address is stored in
Tag/Length/Value format.
Count
This 1-octet field contains the number of address attributes
requested or returned. This is the number of items in the
resolve list.
Resolve list
This variable-length field contains a list of the address
attributes either requested by the originating switch or
returned by the owner switch. Note that in a Resolve request
message, this list contains only the tags of the requested
address attributes. On the other hand, a Resolve response
message with a status of ResolveAck contains the full TLV of
each resolved address attribute. The number of entries in the
list is specified in the count field.
D. Ruffen, et. al. Informational [Page 41]
In an Interswitch Resolve response message, this field is
irrelevant if the status of the response is Unknown.
Actual destination switch MAC
This 6-octet field contains the physical (MAC) address of the
actual switch within the chassis to which the endstation is
attached. If the status of the response is Unknown, this field
is irrelevant.
Downlink chassis MAC
This 6-octet field contains the physical (MAC) address of the
downlink chassis. If the status of the response is Unknown,
this field is irrelevant.
Actual chassis MAC
This 6-octet field contains the physical (MAC) address of the
uplink chassis. If the status of the response is Unknown, this
field is irrelevant.
Domain name
This 16-octet field contains the ASCII name of the domain. If
the status of the response is Unknown, this field is
irrelevant.
D. Ruffen, et. al. Informational [Page 42]
6.5 Interswitch New User Message
The Interswitch New User message consists of a variable number of
octets, as shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Frame header / +
: ISMP packet header (type 5) :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | Version | Opcode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Status | Call Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 | |
+ Source MAC of packet +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Originating switch MAC +
36 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 | |
+ Previous owner switch MAC +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
44 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
48 | :
: MAC address of new user +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
70 | Count | |
+-+-+-+-+-+-+-+-+ +
74 | Resolve list |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In the following description of the message fields, the term
"originating" switch refers to the switch that issued the original
Interswitch New User request. The term "previous owner" switch
refers to that switch to which the endstation was previously
attached. And the term "responding" switch refers to either the
"previous owner" switch or to a switch at the end of the switch
flood path that did not own the endstation but issues an
Interswitch New User response because it has no downstream
neighbors.
With the exception of the resolve list, all fields of an
Interswitch New User message are allocated by the originating
D. Ruffen, et. al. Informational [Page 43]
switch, and unless otherwise noted below, are written by the
originating switch.
Frame header/ISMP packet header
This 20-octet field contains the frame header and the ISMP
packet header.
Version
This 2-octet field contains the version number of the message
type. This document describes ISMP message type 5, version 1.
Opcode
This 2-octet field contains the operation code of the message.
Valid values are as follows:
1 (unused in a New User message)
2 (unused in a New User message)
3 The message is a New User request.
4 The message is a New User response.
The originating switch writes a value of 3 to this field, while
the responding switch writes a value of 4.
Status
This 2-octet field contains the status of a New User response
message. Valid values are as follows:
0 VLAN resolution successful (NewUserAck)
1 (unused)
2 VLAN resolution unsuccessful (NewUserUnknown)
This field is written by the responding switch.
Call tag
This 2-octet field contains the call tag of the endstation
packet for which this New User request is issued. The call tag
is a 16-bit value (generated by the originating switch) that
uniquely identifies the packet that caused the switch to
identify the endstation as a new user.
Source MAC of packet
This 6-octet field contains the physical (MAC) address of the
endstation that originated the packet identified by the call
tag.
D. Ruffen, et. al. Informational [Page 44]
Originating switch MAC
This 6-octet field contains the physical (MAC) address of the
switch that issued the original New User request.
Previous owner switch MAC
This 6-octet field contains the physical (MAC) address of the
switch to which the endstation was previously attached -- that
is, the switch that was able to resolve the VLAN information.
This field is written by the previous owner switch.
If the status of the response is Unknown, this field is
irrelevant.
MAC address of new user
This 24-octet field contains the physical (MAC) address of the
new user endstation, stored in Tag/Length/Value format.
Count
This 1-octet field contains the number of VLAN identifiers
returned. This is the number of items in the resolve list.
This field is written by the previous owner switch.
If the status of the response is Unknown, this field and the
resolve list are irrelevant.
Resolve list
This variable-length field contains a list of the VLAN
identifiers of all static VLANs to which the endstation
belongs, stored in Tag/Length/Value format (see Section 2.3).
The number of entries in the list is specified in the count
field. This list is written by the previous owner switch.
If the status of the response is Unknown, this field is
irrelevant.
D. Ruffen, et. al. Informational [Page 45]
6.6 Interswitch Tag-Based Flood Message
There are two versions of the Interswitch Tag-Based Flood message
used by the SecureFast VLAN product.
6.6.1 Prior to Version 1.8
The Interswitch Tag-Based Flood message used by SFVLAN prior to
version 1.8 consists of a variable number of octets, as shown
below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Frame header / +
: ISMP packet header (type 7) :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | Version | Opcode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Status | Call Tag |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 | |
+ Source MAC of packet +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Originating switch MAC +
36 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 | Count | |
+-+-+-+-+-+-+-+-+ +
44 | VLAN list |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n | |
+ +
: Original packet :
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n = 41 + length of VLAN list
Frame header/ISMP packet header
This 20-octet field contains the frame header and the ISMP
packet header.
D. Ruffen, et. al. Informational [Page 46]
Version
This 2-octet field contains the version number of the message
type. This document describes ISMP message type 7, version 1.
Opcode
This 2-octet field contains the operation code of the message.
The value here should be 1, indicating the message is a flood
request.
Status
This 2-octet field is currently unused. It is reserved for
future use.
Call tag
This 2-octet field contains the call tag of the endstation
packet encapsulated within this tag-based flood message. The
call tag is a 16-bit value (generated by the originating
switch) that uniquely identifies the packet.
Source MAC of packet
This 6-octet field contains the physical (MAC) address of the
endstation that originated the packet identified by the call
tag.
Originating switch MAC
This 6-octet field contains the physical (MAC) address of the
switch that issued the original tag-based flooded message.
Count
This 1-octet field contains the number of VLAN identifiers
included in the VLAN list.
VLAN list
This variable-length field contains a list of the VLAN
identifiers of all VLANs to which the source endstation
belongs. Each entry in this list has the following format:
D. Ruffen, et. al. Informational [Page 47]
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value length | |
+-+-+-+-+-+-+-+-+ +
| VLAN identifier value |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The 1-octet value length field contains the length of the VLAN
identifier. VLAN identifiers can be from 1 to 16 characters
long.
Original packet
This variable-length field contains the original packet as sent
by the source endstation.
D. Ruffen, et. al. Informational [Page 48]
6.6.2 Version 1.8
The Interswitch Tag-Based Flood message used by SFVLAN version 1.8
consists of a variable number of octets, as shown below:
Note
SFVLAN version 1.8 also recognizes the Interswitch
Tag-Based Flood message as described in Section 6.6.1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Frame header / +
: ISMP packet header (type 7) :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | VLAN identifier | Version |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Opcode | Status |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 | Call tag | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Source MAC of packet +
32 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
36 | |
+ Originating switch MAC +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 | | Count | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
44 | |
: VLAN list :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n | |
+ +
: Original packet :
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
n = 41 + length of VLAN list
Frame header/ISMP packet header
This 20-octet field contains the frame header and the ISMP
packet header.
- The frame header source address contains a value of 02-00-1D-
00-xx-yy, where xx-yy is a value set by the VLAN Manager
D. Ruffen, et. al. Informational [Page 49]
application to tag the frame header with the VLAN identifier.
This value ranges from 2 to 4095. For example, a value of
100 would be set as 00-64.
- The frame header type field contains a value of 0x81FF. Note
that this differs from all other ISMP messages.
VLAN identifier
This 2-octet field contains the VLAN identifier of the packet
source.
Version
This 2-octet field contains the version number of the message
type. This section describes version 2 of the Interswitch Tag-
Based Flood message.
Opcode
This 2-octet field contains the operation code of the message.
Valid values here are as follows:
1 The message is a flood request. The original packet is
complete within this message.
2 The message is a fragmented flood request. The first
portion of the original packet is contained in this
message.
3 The message is a fragmented flood request. The second
portion of the original packet is contained in this
message.
Status
This 2-octet field is currently unused. It is reserved for
future use.
Call tag
This 2-octet field contains the call tag of the endstation
packet encapsulated within this tag-based flood message. The
call tag is a 16-bit value (generated by the originating
switch) that uniquely identifies the packet.
Source MAC of packet
This 6-octet field contains the physical (MAC) address of the
endstation that originated the packet identified by the call
tag.
D. Ruffen, et. al. Informational [Page 50]
Originating switch MAC
This 6-octet field contains the physical (MAC) address of the
switch that issued the original tag-based flooded message.
Count
This 1-octet field contains the number of VLAN identifiers
included in the VLAN list.
VLAN list
This variable-length field contains a list of the VLAN
identifiers of all VLANs to which the source endstation
belongs. Each entry in this list has the following format:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value length | |
+-+-+-+-+-+-+-+-+ +
| VLAN identifier value |
: :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The 1-octet value length field contains the length of the VLAN
identifier. VLAN identifiers can be from 1 to 16 characters
long.
Original packet
This variable-length field contains the original packet as sent
by the source endstation.
D. Ruffen, et. al. Informational [Page 51]
6.7 Interswitch Tap/Untap Message
The Interswitch Tap/Untap message consists of a variable number of
octets, as shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
00 | |
+ Frame header / +
: ISMP packet header (type 8) :
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
20 | Version | Opcode |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 | Status | Error code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 | Header type | Header length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 | Direction | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Probe switch MAC +
36 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 | Probe port |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
44 | |
+ +
48 | (Reserved) |
+ +
52 | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
56 | |
+ +
| Header |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Frame header/ISMP packet header
This 20-octet field contains the frame header and the ISMP
packet header.
Version
This 2-octet field contains the version number of the message
type. This document describes ISMP message type 8, version 1.
D. Ruffen, et. al. Informational [Page 52]
Opcode
This 2-octet field contains the operation type of the message.
Valid values are as follows:
1 The message is a Tap request.
2 The message is a Tap response.
3 The message is an Untap request.
4 The message is an Untap response.
Status
This 2-octet field contains the current status of the tap
request. Valid values are as follows:
1 Switch must disable outport on untap. (DisableOutport)
2 Switch must keep outports on untap. (KeepOutport)
3 Probe not found this leg of spanning tree. (ProbeNotFound)
4 Still searching for probe switch. (OutportDecisionUnknown)
5 Unassigned. (StatusUnassigned)
6 (reserved)
7 (reserved)
8 (reserved)
9 (reserved)
See Section 5.2.3 for details on the use of this field.
Error code
This 2-octet field contains the response message error code of
the requested operation. Valid values are as follows:
1 Operation successful. (NoError)
2 No response heard from downstream neighbor. (Timeout)
3 Port does not exist on probe switch. (BadPort)
4 Message invalid. (InvalidMessage)
5 Version number invalid. (IncompatibleVersions)
Header type
This 2-octet field contains the type of information contained
in the header field. Currently, valid values are as follows:
1 (reserved)
2 Header contains destination and source endstation MAC
addresses.
Header length
This 2-octet field contains the length of the header field.
Currently, this field always contains a value of 12.
D. Ruffen, et. al. Informational [Page 53]
Direction
This 2-octet field contains a value indicating the type of tap.
Valid values are as follows:
1 (reserved)
2 Tap is bi-directional and data should be captured flowing
in either direction over the connection.
3 Tap is uni-directional and data should be captured only
when it flows from the source to the destination.
Probe switch MAC
This 6-octet field contains the physical (MAC) address of the
switch to which the probe is attached.
Probe port
This 4-octet field contains the logical port number (on the
probe switch) to which the probe is attached.
Reserved
These 12 octets are reserved.
Header
This variable-length field contains the header that identifies
the connection being tapped. The length of the header is
stored in the length field.
Currently, this field is 12 octets long and contains the 6-
octet physical address of the connection's destination
endstation, followed by the 6-octet physical address of the
connection's source endstation, as shown below:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ Destination MAC address +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Source MAC address +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
D. Ruffen, et. al. Informational [Page 54]
7. Security Considerations
Requested call connections are established or denied based on the
VLAN policy of the source and destination addresses specified
within the packet. Section 4.4.1 discusses this process in
detail.
8. References
[RFC1700] Reynolds, S.J., Postel, J. Assigned Numbers.
October 1994.
[IEEE] "IEEE Standard 802.1d -- 1990"
[IDvlsp] Kane, L., et. al. Cabletron's VLS Protocol
Specification.
[IDhello] Hamilton, D., Ruffen, D. Cabletron's VlanHello
Protocol Specification.
9. Authors' Addresses
Cabletron Systems, Inc., is located at:
Post Office Box 5005
Rochester, NH 03866-5005
(603) 332-9400
Dave Ruffen Email: ruffen@ctron.com
Ted Len Email: len@ctron.com
Judy Yanacek Email: jyanacek@ctron.com
10. Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document and translations of it may be copied and furnished
to others, and derivative works that comment on or otherwise
explain it or assist in its implementation may be prepared,
copied, published and distributed, in whole or in part, without
restriction of any kind, provided that the above copyright notice
and this paragraph are included on all such copies and derivative
works. However, this document itself may not be modified in any
way, such as by removing the copyright notice or references to the
Internet Society or other Internet organizations, except as needed
for the purpose of developing Internet standards in which case the
procedures for copyrights defined in the Internet Standards
D. Ruffen, et. al. Informational [Page 55]
process must be followed, or as required to translate it into
languages other than English.
The limited permissions granted above are perpetual and will not
be revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on
an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE."
D. Ruffen, et. al. Informational [Page 56]
INTERNET DRAFT EXPIRES JUNE 1999 INTERNET DRAFT