Smart DeskStream
Token Ring Switch
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What is Desktop Switching ?
Conventional Shared Token Ring
Shared User Ring
n
Users share the Token Ring
network
n
Often up to 80 users share 16Mbps
CAU/LAM or
Chassis
Switched ring
Fully Switched Token Ring
n
n
n
Each user has their own dedicated Token
Ring !
No need to share 16Mbps with other
users
Desktop
Switch
Connections can be Full Duplex (32Mbps)
Smart DeskStream Technical Presentation 3
The CAU/LAM is the ring. Users share the bandwidth available on
that ring - typically 16Mbps these days.
A ring can support over 250 users in theory, but in practice this
number is better limited to around 80. Even at this reduced number,
power users may suffer from ‘bandwidth starvation’! The DeskStream
allows them to each have a full 16Mbps since each port is its own
ring. If the adapter driver will support it, the connection can be full
duplex DTR which allows a maximum throughput of 32Mbps.
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Smart DeskStream
Product Overview
n Designed as a shared hub replacement
n 1 U high
n 24 ports with auto ring speed and protocol
detect
n Plug ‘n’ Play installation
n Easily stacked to offer up to 192 ports
n High performance switching
n Simple, graphical management
Smart DeskStream Technical Presentation 4
The DeskStream is a workgroup switch, i.e. There is no internal ring -
data is switched between ports. It is designed to replace the shared
medium hubs e.g. CAUs and RAMs.
It is 1U high which saves space in the rack. The racking lugs are user
installable since it can be a free standing unit as well.
By default all ports are speed detecting and can also negotiate full
duplex or classic mode token ring. Both of these parameters can be
manually configured if necessary.
In general, the default setting allows us to connect it up and it just
works.
Up to eight DeskStreams can be stacked using the stacking bus; this
means that a single stack can support up to 192 workstations in a
completely switched environment. The stack can also support up to
16 uplink ports.
All ports can - providing that the drivers support it - run in full duplex
DTR mode.
Managing via the Trueview GUI is straightforward. Each stack shows
as a single icon; opening the icon reveals each DeskStream and
allows them to be managed individually.
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Easy Integration
into existing networks
Typical Network
Layout
Shared User Ring
CAU/LAM or Chassis
Network
Backbone
Smart DeskStream Technical Presentation 5
The slide shows part of a typical network, with CAUs providing a
shared medium interface for the workstations. The CAUs are
connected to Ringswitches as are the servers.
Ultimately some users will complain of slow responses especially as
both programs and data files get bigger.
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Easy Integration
into existing networks
2. Reduce size of shared ring
n Greater bandwidth for remaining shared
Shared User Ring
users
3. Introduce 32Mbps- Full
Duplex uplink
n Higher performance access to
backbone resources
1. Move users to switched,
DeskStream ports
n Simple, reconnection of ports
n Immediate bandwidth upgrade for 23 users
n Improved manageability and reliability
Network
Backbone
Smart DeskStream Technical Presentation 6
Switching to the workgroup can help alleviate this problem.
The DeskStream can be connected between the CAU and the
Ringswitch using the single Master (or node) port (24) on the
DeskStream to connect to the CAU and one of the Direct (or
concentrator) ports, or an uplink port to connect to the Ringswitch.
Once the DeskStream is connected and operational, the power users
can be moved across simply by moving the cable connection - no
other configuration activity is required. These users now get a
dedicated connection and will also release bandwidth for the
workstations remaining on the shared medium ring.
CAUs and RAMs can’t use full duplex DTR, but the DeskStream can!
So the uplink to the Ringswitch is a more efficient link than the
original CAU link.
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Easy Integration
Hub Replacement
Switched User Ring
1. Add DeskStreams as
needed
n Easily scalable solution
n High port density releases rack
space
2. Move all users to switched ports
n Performance, security and manageability
for each user connection
Network
Backbone
Smart DeskStream Technical Presentation 7
As time and money permits, the remaining workstations can be
phased over to a switched environment as more DeskStreams are
installed and stacked.
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Powerful, Flexible Connectivity
Resilience
Switched User Ring
1. Add additional links to
backbone
n
Resilience, load sharing and higher
access speeds
Network
Backbone
Smart DeskStream Technical Presentation 8
CAUs can be connected to two Ringswitches to give a resilient link,
so can the DeskStream, either as a standalone device or, as shown
in the slide, as part of a stack.
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Powerful, Flexible Connectivity
Resilience and Performance
Switched User Ring
1. Use HSTR uplinks to increase
backbone access
n
Resilience, load sharing and higher
access speeds
2 x 100Mbps
Network
Backbone
Smart DeskStream Technical Presentation 9
If bandwidth still needs to be extended, the DeskStream supports
HSTR uplink modules - both copper and fibre. These only work as a
point to point full duplex link and so potentially will allow a 200Mbps
connection.
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Smart DeskStream Family
Summary
Smart DeskStream Token Ring Switch
n 24 workstation ports with two module slots
Smart DeskStream Stacking Module
n One required for each DeskStream to be stacked
Smart DeskStream TR Fibre Module
n Dual ports, 4, 16Mbps and DTR, load sharing and
redundancy
Smart DeskStream HSTR Copper Module &
Smart DeskStream HSTR Fiber Module
n Dual ports, 100Mbps, load sharing and redundancy
Smart DeskStream Technical Presentation 10
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Smart DeskStream
Background Positioning
Smart DeskStream behaves like a hub
n When integrating DeskStream into an existing
network, use it as if it was a CAU/LAM.
Smart DeskStream is designed for simplicity
n DeskStream offers full auto-configuration for
simple installation
Smart DeskStream Technical Presentation 11
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Smart DeskStream
Background Positioning
n Smart DeskStream is NOT designed as a
backbone applications switch
n You can only support a shared device on one port
n It does NOT offer Active Broadcast Control, full
RMON or protocol filtering.
l These are backbone features, not required at the
workgroup level
n Smart Ringswitch Family is for backbone
solutions
n DeskStreams and Ringswitches can be integrated
to provide a TR switching solution
Smart DeskStream Technical Presentation 12
As we saw in the slides on integrating into an existing network, the
DeskStream has only one workstation port which is capable of being
connected to a shared medium hub.
Uplink ports can be connected to CAUs either as nodes or ,if using
fibre, as RI/RO ports. This connectivity option is not recommended.
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Smart DeskStream
Token Ring Switch
Connectivity
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Connectivity
Ports
n 24 RJ45 ports
n Each behaves EXACTLY like a shared hub port
n Each port has its own MAC address
n Ports 1 - 23 are direct, each can be connected to
l Adapters
l Bridges/ Routers
l Backbone TR switches
n Direct ports are also known as slave or
concentrator (on Ringswitches) ports
Smart DeskStream Technical Presentation 14
The DeskStream workstation ports are RJ45 connectors and are
ports which work like a shared medium hub port, i.e. in classic mode
they will require the phantom drive to be present.
Each port has its own MAC address, so whether working in classic
mode or full duplex DTR the connection there will be only two
addresses on the link.
Ports 1 - 23 are called direct ports and are similar to concentrator
ports on a Ringswitch. (They are also sometimes known as ‘slave’
ports). They will accept a connection to a TR adapter, a bridge or
router port or a Ringswitch port set up as a node.
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Connectivity
Ports - 2
n 24th RJ45 port
n 24th port is a master, and can be
l connected to a shared Hub port (any type/vendor)
l re-configured as a direct port
n Master port is also known as node (on
Ringswitches)
n Master port can therefore be configured as node or
concentrator, similar to a Ringswitch port
Smart DeskStream Technical Presentation 15
Port 24 is configurable, but by default it is a master (or node) port.
This can be connected to a CAU (or RAM) port or to a Ringswitch
port that is in concentrator mode.
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Connectivity
Ports - 3
n Ring Speed / Protocol Detect
n
Each port supports 4Mbps, 16Mbps and Full Duplex
(Dedicated TR)
l Default is auto speed sensing
l Ring speed may be manually configured on a per port basis
n
n
Impedance is matched to support UTP/STP cabling
l No requirement for a separate media filter / Balun
Negotiates Classic TR or full duplex DTR on insertion
Smart DeskStream Technical Presentation 16
The port can be given a name and the ring speed and protocol can
be left as Auto or can be configured manually. The port can also be
enabled or disabled. No other port parameters (except port mode on
port 24) can be configured.
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Connectivity
Ports - LEDs
n Left Port LED:
n Green - Port open
n Flashing green - Disabled
n Right Port LED:
n Red - Port closed
n Flashing red - Error
n Port 24 will flash red by default (because it is
master as default)
Smart DeskStream Technical Presentation 17
Left LED - flashing green; disabled by management software
Right LED - red. This happens when a connection is made against
the configured set up e.g. workstation connects with a non DTR
driver into a manually configured DTR port
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Connectivity
Status LEDs
n First LED on right of unit - Status
n Green - Normal operation
n Flashing green - Diagnostic self test
n Red - Error
l System Failure
n Flashing Red - Warning
l E.g. Fan Failure
Smart DeskStream Technical Presentation 18
System failure - e.g. CPU crash i.e. will require a replacement
DeskStream
Warning - failure which allows the DeskStream to continue working,
at least temporarily.
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Connectivity
Status LEDs - 2
n Second LED, Module Link 1
n Green - Port open
n Red - Port closed
n Flashing green - Disabled
n Flashing red - Error
n Third LED, Module Link 2 - As for Link 1
Smart DeskStream Technical Presentation 19
Flashing red - e.g. module installed as node, but with nothing
connected
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Connectivity
Stacking Module
n Stacking Module and Cable
n Installed into stacking slot on rear of each
DeskStream in a stack
l module has two mini SCSI connectors
n Supplied with short, mini-SCSI cable
n Top port connects to DeskStream above
n Bottom port connects to DeskStream
below
n Unused ports do not need to be terminated
n 8 DeskStreams can be stacked
n Stacking bus has 640Mbps data
throughput
Smart DeskStream Technical Presentation 20
The stacking bus is not configurable in any way
It uses a cell-based communications technology (similar to ATM)
The cells are 53 bytes long including an 8-byte header and 45 bytes
of payload
The bus has 640Mbps of bandwidth available and each DeskStream
can access up to 350Mbps.
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Connectivity
Stacking Module - 2
n Bottom DeskStream
n Automatically configures itself as Master
n Assumes responsibility for stack management
n TrueView sees the stack as a single icon
n Uses Master mgmt MAC address or LAA
l Mgmt MAC is same as base MAC address
n Single IP address per stack
n Single download image,
l Master takes care of upgrade to all DeskStreams in
the stack
l Active download
l Uses this microcode after reset
Smart DeskStream Technical Presentation 21
Trueview displays a single icon for each stack. Opening the icon
shows the individual units in the stack.
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Connectivity
Stacking Module - 3
n Stacking Module cannot be hot-
swapped
n DeskStream unit must be powered off
before installing stacking module
n Cable may be connected to another
DeskStream while it is powered on
n Stacking becomes active on reboot of all
DeskStream units in stack
Smart DeskStream Technical Presentation 22
It is important to remember that any installation or removal of
modules must be done with power off - this device has no hot
swappable units.
Cabling is, of course movable at any time and this includes the
stacking bus cables. Removing a stacking bus cable will be detected
by the Master unit and this will cause a reboot; adding a cable is not
detected by the Master so a manual stack reboot will be required.
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Connectivity
Stacking Module - 4
n DeskStream Resilience
n Lost power or stacking module failure
n Stack will reboot
n If failing unit is in the stack center, two
separate stacks will form
n ‘New’ stack appears under TrueView/32 (If
secondary uplink exists)
Stack 1
Stack 2
Smart DeskStream Technical Presentation 23
A DeskStream may fail in two ways: one in which the stacking bus is
taken down (usually a total power failure) and another where the
DeskStream fails but keeps the stack active.
In the first case the stack will divide around the failing DeskStream,
resulting in two stacks each of which will be detected by Trueview if
both stacks have an uplink. The Master will detect this failure and
reboot (the remains of) its stack (stack 2 in the slide).
A new master will take control of the ‘new’ stack and start with a
reboot.
If the network is using IP and a secondary uplink exists, it will be
necessary to give the upper part of the defective stack an IP address
if both parts are to continue working. A DHCP server will be helpful
here.
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Connectivity
Stacking Module - 5
n DeskStream Resilience
n If stacking module remains operative
n Stack will reboot
n If failing unit is in the stack center, stack
continues to operate
n DeskStream will be shown as failed under
TrueView/32
Single Stack
Smart DeskStream Technical Presentation 24
In the second case, the Master will detect the failure and attempt to
recover the failing unit by rebooting the stack. Assuming this doesn’t
solve the problem, Trueview will show the stack with a failed module,
but the stack will continue to operate. Of course users on the failed
module will be off the network.
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Uplink Connectivity
Uplink modules are installed in the back of the unit
Use the icon to display the uplink ports
The icon will display the uplink ports on all the
Deskstreams in the stack
Smart DeskStream Technical Presentation 25
Managing the Uplink Module
The uplink is a function of the stack so selecting the uplink icon will
display all the uplinks in the stack.
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Uplink Connectivity
The icon will display all the uplink ports which exist on
the stack
Select individual ports for management
Link 1 is port 25 and Link 2 is port 26
Smart DeskStream Technical Presentation 26
Managing the Uplink Module
The uplinks are, to a large extent, just two more ports similar to port
24 in that the port type can be configured. They are numbered 25 and
26. In a stack each port is known by the DeskStream number in the
stack followed by the port number e.g. 2.21 - this is the second
Deskstream (counting up from the master (1)) and port 21.
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Fiber Connectivity
TR Fiber Module - 1
n Dual Link Fiber Connectivity
n Each link supports 4Mbps, 16Mbps and Full
Duplex (DTR)
n Links operate independently
n Allows redundant links / load sharing in Fiber
environments
n Each link can be set to Master or Direct mode
(Node or Concentrator mode)
The two uplink ports, although physically mounted on the same
module, are in fact separate entities which will operate independently.
This means that they can each be used for different functions, if
necessary:
one could be an uplink to a Ringswitch, the other could have a server
attached for example; they could each be connected to different
Ringswitches to allow a dual path (not very resilient if the DS fails!);
or one could be used to connect to another remote DeskStream while
the other had a server attached … and so on. More examples on the
next slide.
This is possible because the port type can be configured.
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Fiber Connectivity
TR Fiber Module - 2
n Allows Fiber connection to
n TR Fiber adapters
n Backbone TR switch fiber ports
n Third party Fiber TR shared hub ports
n TR CAU Fiber Trunk Link
l configure for Ring In, Ring Out mode
n Other DeskStream Fiber modules
l In back to back mode
One DeskStream Link set as master, the other set as direct
Can be configured in the same way as a Ringswitch fibre port, for
attachment to a CAU fibre RI/RO port
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Fiber Connectivity
TR Fiber Module - 3
n Fiber port Specifications
n Uses standard IEEE 802.5j specifications
n Operates at wavelength 850 nm
n Supports Multi-mode Fiber cabling
l 62.5/125um or 50/125um acceptable
n Distances of 2Km
n ST connectors
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High Speed Token Ring
HSTR Copper and Fiber Modules - 1
n Dual Link HSTR Connectivity
n
n
n
n
n
n
n
Each link supports 100Mbps Full Duplex DTR
Compatible with IEEE 802.5t
Copper module uses RJ45 connectors
Fiber module uses SC connectors
Links operate independently
Offer redundant links / load sharing
Each link can be set to Master or Slave mode
As with the Ringswitch HSTR module this only supports 100Mbps full
duplex DTR and is fully compatible with IEEE 802.5t, the HSTR
specification.
There are two HSTR modules:
Copper which uses RJ45 connectors and
Fibre which uses SC connectors
As we saw with the standard TR module, each port is independent
and can be used in the same ways with other HSTR components.
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HSTR Connectivity
HSTR Copper and Fiber Modules - 2
n Allows HSTR connection to
n HSTR adapters (for servers & power users)
n Backbone HSTR switch ports
n Other DeskStream HSTR modules
l In back to back mode
l One DeskStream Link set as master, the other set as
slave
Smart DeskStream Technical Presentation 31
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HSTR Connectivity
HSTR Fiber Module
n HSTR Fiber port Specifications
n Uses standard IEEE 802.5t specifications
n Operates at wavelength 1300 nm (same as FDDI)
n Supports Multi-mode Fiber cabling
l 62.5/125um or 50/125um acceptable
n Distances of 2Km
n SC connectors
Smart DeskStream Technical Presentation 32
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Smart DeskStream
Token Ring Switch
Management
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Network Management
Smart DeskStream Manager
n Graphical, Windows-based management
n Uses Madge’s TrueView/32 platform
l 16-bit TrueView does not support DeskStream
n Easy to use
n Will integrate with other platforms
l DeskStream Mgr for HP OpenView for HP-UX and NT
l DeskStream Mgr for Tivoli NetView for IBM AIX
Command Line Interface (CLI)
n Text based
n via Telnet session or Direct serial connection
n Allows access to more complex operations
Smart DeskStream Technical Presentation 34
There are two major ways of managing the DeskStream:
1. Using Trueview/32
2. Using the command line interface.
There is no 16-bit Trueview device manager for DeskStream and so it
can only be managed with Trueview/32 - the 32-bit version.
This is just another device manager and is used in the same way that
other device managers are used in Trueview.
Trueview itself can be integrated into higher level network
management software, e.g. HP OpenView and Tivoli NetView. Using
one of these to access a Madge device will bring up the Trueview
device manager.
The command line interface can be used via a null modem
connection to the 9-pin serial interface on the back of the
DeskStream, or using IP and Telnet through the normal network
ports. The content is the same.
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Smart DeskStream
Management Features
Software Downloads
n Download in active mode
l Download becomes active on reboot
n Single download file for all flash and microcode
files
l TFTP over IPX or IP
l SNMP over IPX or IP
l Flash memory to run diagnostics, MAC and boot
sequence
Smart DeskStream Technical Presentation 35
All downloads are performed via a normal network connection when
the DeskStream is active. The new microcode is stored in flash
memory until the next stack reset, when it is stored permanently.
There is a single binary file for all required software for the
DeskStream.
The process can be managed from within Trueview when we specify
TFTP over IP or IPX, or the serial port or Telnet which uses raw
SNMP commands (IP only of course over Telnet).
Using the serial port or Telnet to manage the process is simple over
IP, we just need to specify the IP address of the machine hosting the
binary file, and the path to the file. It is a little more complex over IPX
since we will need to specify the Network id (8 hex digits), the node id
(MAC address - 12 hex digits) and the socket id (4 hex digits).
E.g.
00000002 (Network id )
0000F63D1836 (Node id)
5400 (Socket id)
Use the Trueview Tools, Services, Configuration to discover these
values.
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Smart DeskStream Manager
Advanced Functionality
Easy to configure options
n Up to 5 write and read passwords
n Dynamic table of port configurations
n Copy bit on transparent frame option
Simplified support
n Menu icon to view all microcode versions
n Configuration downloads and uploads
n Switch status report
Smart DeskStream Technical Presentation 36
We can set up to five write and read passwords to give several
people different levels of management access to the DeskStream.
The Dynamic table or port configurations allows us to change any
one of the configurable port parameters on one or more ports at one
time. The contents of this table can also be saved to file, clipboard or
to a printer for archiving. When saving this table wait until it has
finished its dynamic restore.
Bridges and switches sometimes have a problem with the setting of
the Address Recognised/ Frame Copied bits when using transparent
bridging. This can be manually configured on the DeskStream.
A Trueview icon will display the hard and software versions; this
information can be saved to a file, clipboard or to a printer. Dump and
Configuration data is also noted in this table which can be uploaded
and subsequently, if necessary, downloaded back to the
DeskStream.
Opening the I-field icon will show a status report for the DeskStream;
if there is a problem a Details button will give more information.
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Smart DeskStream Manager
Command Line Interface
Telnet and serial interface menu is easy:
DeskStream Terminal Configuration
1. General
2. Versions
3. IP
4. Port
5. Port Group
6. Spanning Tree
7. Bridge
8. Download
9. Debug
10. Quit
Enter selection number:
Smart DeskStream Technical Presentation 37
The CLI is divided into a number of sections, each of which is divided
further. Each will have some Show and Set commands, possibly
function Enable and Disable.
1. General
system values
system health
I-field values (name, contact, location)
set passwords
2. Versions
3. IP
version numbers and build time
IP values, set address, subnet, gateway
enable BOOTP, DHCP, RARP
4. Port
Show/configure various port parameters on a per port basis
Show/configure port group parameters
5. Port Group
6. Bridge
Show/set bridge no., hop limit, SR or SRT
7. Spanning Tree Show/set spanning tree protocol parameters
8. Download
Set IP/IPX address of binary file host
Start IP or IPX download
9. Debug
Set address for uploading file, dump or configuration data
Show last reset, last dump, last saved data
10. Quit
Guess!
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Smart DeskStream
Diagnostic Features
Diagnostic Downloads
n Self-tests run on every reboot
n Output is sent over serial port as it runs
n On failing,
l The test will halt
l The Status LEDs will flash to signify an error
l The failing test message will be re-sent to the serial port
every 15 seconds
l A terminal can then be connected to see the error
n Output can be provided to Madge Support for
problem diagnosis
n Allows simple and quick diagnosis of problems
Smart DeskStream Technical Presentation 38
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Smart DeskStream
Token Ring Switch
Source Route Switching
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Smart DeskStream
Objectives
At the end of this session you will be able to:
n Explain Source Route Switching, including
n
Concentrator Relay Function
n
Bridge Relay Function
n Demonstrate IBM & IEEE Spanning Tree support
n Use the built-in Diagnostics
Smart DeskStream Technical Presentation 40
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Source Route Switching
n What is Source Route Switching ?
n Industry term for using switching in the
workgroup
n Refers to IEEE 802.5 Annex K specification
n Supports Transparent and Source Route traffic
n How does it work ?
n Switch behaves like a transparent switch
l Matches the MAC address and route descriptors to
ports
n Source Route information is preserved
Smart DeskStream Technical Presentation 41
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Source Route Switching
‘Annex K’
n Components of Annex K ?
n Concentrator Relay Function (CRF)
l Handles switching process
l All ports access the network using the same ring
number (source routing)
l Includes all ports (by default) within a stack of
DeskStreams
n Bridge Relay Function (BRF)
l Allows bridging between CRF and ports on different
ring numbers
l Equivalent to an IEEE SRT switch
Smart DeskStream Technical Presentation 42
The CRF manages all the basic ports including a ‘virtual’ port which
gives a link to the BRF interface and any ports which have been
transferred to that interface.
Ports within the CRF all use the same ring number (although they are
not in a ring - this is a switched environment). This allows an SR
frame (in an SR network) to find the correct DeskStream stack; the
CRF will sort out, from its Address/Descriptor table, which port to
pass the frame to.
The BRF allows us to take some ports out of the CRF and assign a
different ring number to each. The BRF manages the switching
between these ports and - via the CRF - to the basic ports.
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Source Route Switching
Frame Forwarding using CRF
n DeskStream behaves as a transparent bridge
n It learns the MAC and RIF information in passing
frames, and builds up an address table
l Also known as Active Learning
n As frames arrive, the next hop or destination
MAC address is looked up in the table to
determine which port to forward the frame
l If the destination MAC address or route descriptor is
not listed against a port the DeskStream forwards the
frame to all ports
n Up to 2048 entries of MAC or route descriptor in
each DeskStream
Smart DeskStream Technical Presentation 43
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Source Route Switching
Introducing multiple uplinks - 1
n Resilient links
Dual uplinks to the same backbone switch
A
This is an illegal configuration - two ports on the
same switch cannot connect to the same ring
Note: SRT+ will not overcome this - SRT+
learns configuration from ring poll process,
which DeskStream only performs on each port
X
Spanning tree will close one of the ports
Ring Number 101
Backbone
Smart DeskStream Technical Presentation 44
Duplicate links to the same Ringswitch will usually result in a bridging
error - bridging a ring to itself makes no sense - and spanning tree
will close one of the ports
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Source Route Switching
Introducing multiple uplinks - 2
n Load sharing connectivity
Dual uplinks to different backbone switches
A
Both uplinks will be active, allowing load sharing
of source route traffic
AREs and specifically routed frames will pass
through
(Transparent traffic will still be blocked on one
port)
Active
Ring Number 101
Active
Backbone
B
Smart DeskStream Technical Presentation 45
Dual connection to two Ringswitches, each with its own bridge
number, and both ports having the same ring number assigned, is a
valid and normal resilient operation.
On a Source Routed network one of the Ringswitch ports will be
designated, the other standby. Standby ports will not pass Spanning
Tree Explorer frames (sometimes called Single Route Explorers), but
will pass All Routes Explorers and Specifically Routed frames.
In a Transparently bridged network one port will be forwarding, the
other blocking. Blocking ports allow no frames to pass.
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Source Route Switching
Bridging using BRF
n What is the Bridge Relay Function?
n Provides SRT bridging between SR ring
numbers on different ports
n Allows a different ring number to be set on
each port
n Ports cannot share a ring number
107
109
108
Smart DeskStream Technical Presentation 46
The BRF allows us to set up ports outside the CRF. These have
individual ring numbers which cannot be shared. The BRF allows
these ports to communicate with each other and, through the CRF,
with the ports using the shared ring number.
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Source Route Switching
Bridging using BRF
n What is the Bridge Relay Function?
DeskStream ports
CRF Port Interface (Local)
‘Virtual’ port
BRF Port Interface (SRB)
Port 17
Port 23
Port 20
(ring 107)
(ring 109)
(ring 108)
Smart DeskStream Technical Presentation 47
The CRF manages switched communication between its ports.
The BRF is only available on the Master DeskStream - the bottom
one in a stack - and manages switched communications for the BRF
ports.
By default all ports in a DeskStream stack are in the CRF, but we can
enable the BRF interface on any or all of the Master DeskStream
ports including the uplink modules.
Communication between the CRF interface - known as the Local
Interface - and the BRF interface - known as the Source Route
Bridging (SRB) Interface - is via the ‘virtual’ port.
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Source Route Switching
Setting up the BRF interfaces
n Use the Set icon
n Select ‘Advanced…’
Smart DeskStream Technical Presentation 48
Setting up the BRF is a global function using the indicated icon.
The port grouping dialogue box specifies the CRF parameters, but
the Advanced button takes us to the internal interfaces - local and
SRB.
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Source Route Switching
Setting up the BRF interfaces
Local IF
parameters
SRB IF
parameters
Smart DeskStream Technical Presentation 49
The main use of the two parts of this dialogue box is to vary the path
cost. These two interfaces are within the DeskStream and for optimal
network management we don’t want these to be standby or blocking
bridges. The local interface, by default will have a very low path cost
(2) and so should always be designated or forwarding. The SRB
interface is currently defaulted to auto path cost and so will get a
value based on the ring speed divided into 1000 (62 for 16Mbps, 10
for 100Mbps). It might be sensible to lower this manually.
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Source Route Switching
Setting up BRF on a port
n Select a port
n Select SR bridging
Smart DeskStream Technical Presentation 50
Once the interfaces are set up, enabling SRB on individual ports on
the Master DeskStream is simple. The SR Bridging entry in the
menu will only appear on ports on the Master DeskStream. Select
this entry.
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Source Route Switching
Setting up BRF on a port - 2
n Enable SRB
n Auto learn or
Specify ring
number
Smart DeskStream Technical Presentation 51
The resulting dialogue box is similar to that for the CRF except that
we can enable Source Route Bridging and there is no Advanced
button.
We can choose to enter a ring number or let the device find it for
itself; we can set the maximum hop count - this will vary depending
on whether we are using the IBM spanning tree specification (7) or
the IEEE (13).
We can also set an LAA if we want to.
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Source Route Switching
Combining CRF and BRF functions
n CRF is operational on all ports in stack by default
n
CRF will attempt to learn ring number
n
the CRF ring number can be manually configured
n BRF will only function on master DeskStream
n
only ports on master DeskStream are supported on BRF
n
Each port can be designated as a BRF port, including option
module ports
n
n
n
Each BRF port has its own ring number
BRF ports can auto-detect ring number
Internal “virtual” port links between the CRF and BRF
CRF
BRF
Smart DeskStream Technical Presentation 52
Summary
CRF will attempt to learn the ring number from the RIF in passing
frames as will the BRF.
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Source Route Switching
Introducing multiple uplinks - 3
n Load sharing, resilient connectivity
Dual uplinks to the same backbone switch
A
This is an illegal configuration - two ports on the
same switch cannot connect to the same ring
Use BRF to set one of the ports to a different ring
number
This is a legal configuration - both uplinks will be
active
If middle DeskStream fails, both DeskStreams
Active
retain backbone connectivity
101
Active
BRF
Ring Number 102
Smart DeskStream Technical Presentation 53
What do we need the BRF for?
One use is in resilient networks. The DeskStream replaces the
shared medium hubs which are often connected to two backbone
switches to ensure a connection.
As we have seen, connecting two CRF ports to one Ringswitch is an
illegal configuration and will fail. If we need to connect this way -
perhaps to ensure maximum connectivity for a DeskStream stack if
one fails catastrophically - then the BRF with a different ring number
makes this an allowable configuration.
We will need to manage the path costs to ensure that standby (SR)
or blocking (Transparent) ports are in the Ringswitch.
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Source Route Switching
Introducing multiple uplinks - 3
n Setting Spanning Tree mode
n Select icon
n Set IEEE or IBM
n Set SRT or SR only
Smart DeskStream Technical Presentation 54
Selecting the bridge icon brings up the Bridging Information dialogue
box.
In this we can set the Bridge Number (in a resilient network) and the
global hop count limit - this has a maximum of 7 for the IBM spanning
tree option and 13 for IEEE 802.1d.
We can choose the spanning tree option we want to use. Don’t forget
that this must be consistent over all relevant devices on the network.
We can also choose whether the switch will support SRT or SR only.
Selecting SR only will change the spanning tree mode to IBM SR.
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Spanning Tree
IEEE Spanning Tree Support
n DeskStream supports IEEE
n DeskStream participates in negotiation
DeskStream CRF and BRF send out and respond
to IEEE spanning tree frames
CRF to BRF link has a very low path cost to avoid
blocking within the DeskStream
X
Blocking will therefore occur at backbone port
Ring Number 101
IEEE SPT
CRF
BRF
Ring Number 102
Smart DeskStream Technical Presentation 55
In a more complex resilient network the CRF/BRF takes part in the
bridging conversations since it is a bridge. The responses to
Spanning Tree management frames is completely normal and so will
it will depend on path cost, ring number or MAC address as to which
ports are designated or standby (forwarding or blocking).
Note on internal blocking:
This is not a problem if the only BRF port is an uplink, but ALL BRF
ports will use this interface, so if it is blocking this may impact other
connections - dual attached servers for instance? If the BRF or Local
interface blocks it may result in the majority of traffic taking a longer,
less efficient route.
For that reason, it is important that all blocking/standby ports are
external to the DeskStream i.e. in a Ringswitch.
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Spanning Tree
IBM Spanning Tree Support
n DeskStream DOES NOT participate in IBM
Spanning Tree negotiation
2
Switch 1 sends IBM Spanning Tree BPDU
DeskStream forwards BPDU to all ports, including
other uplinks
X
Switch 2 receives BPDU, and appears as direct link
To prevent a loop, one backbone port will then
block
1
IBM BPDU
Smart DeskStream Technical Presentation 56
A DeskStream stack with only CRF ports doesn’t take part in any
bridging conversations - it acts in the same that a CAU would.
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Spanning Tree
IBM Spanning Tree Support - 2
n BRF can be configured to participate in
IBM Spanning Tree negotiation
2
BRF negotiates with other switches in the network
to configure the spanning tree
CRF to BRF link has a very low path cost to avoid
blocking within the DeskStream
X
Blocking will therefore occur at backbone port
Ring Number 101
IBM BPDU
1
CRF
BRF
Ring Number 102
Smart DeskStream Technical Presentation 57
As we saw in an earlier slide.
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