Fast Ethernet Super-Subnets Proposal

Generic Proposal

Problems tackled

Within-subnet throughput

Increased from 10 Mbit/s shared up to 10 Mbit/s or 100 Mbit/s switched. This is one or two orders of magnitude improvement.

Off-subnet throughput

Increased from 10 Mbit/s shared to (a share of) 100 Mbit/s switched. This is also an order of magnitude improvement.

Consolidation and Standardization of "Glue Boxes"

Each Cisco Ethernet interface could have associated with it a DELNI or repeater; several thinwire, 10BASE-T or FOIRL transceivers; and all the cables required to link these boxes together. For a Cisco with 18 Ethernet interfaces this can add up to a large number of parts.

A Catalyst switch can provide many of these functions for many subnets in one box. It provides a standard way to add another local 10 Mbit or 100 Mbit port, add a 10 Mbit fibre-optic port, add a local monitoring or test port, and collect subnet usage statistics.

A Catalyst can provide 48 to 96 user ports, and several Catalysts can "front-end" the one Cisco 7000 ... which allows for many more switched ports than are available with the Cisco alone.

VLAN support

Sets of ports chosen from any of the interface cards can be configured as a Virtual LAN (VLAN). This should improve port utilization over the current practice of using separate hubs for each LAN.

Changing a particular port from one LAN to another can be done programatically, rather than requiring physical patching.

Other Considerations

To get from one VLAN to another still requires the packets to go through a router. So, to get from a port in one VLAN on the Catalyst to a port on a different VLAN on the same Catalyst requires the packets to go up the link to the router and back again.

A cisco router port will be a member of each VLAN. End-systems will be configured in the normal way to send off-subnet IP packets to a default router at the .254 address.

Fast Ethernet is proposed rather than other high-speed networking technologies such as 100VG-AnyLAN, FDDI/CDDI or ATM because:

• Ethernet and Fast Ethernet use the same packet size and framing, only the clock rate is different. This means no packet encapsulation conversions or packet splitting in switches, and shouldn't require any changes to networking software.
• Some interface cards can auto-sense between Ethernet and Fast Ethernet allowing for the one card to be purchased to use on existing 10 Mbit/s networks and then moved to 100 Mbit/s networks.
• Fast Ethernet interfaces are available for our newer main host machines and for PCI and EISA file servers.
• Fast Ethernet cards are relatively cheap. For example, Digital's Fast EtherWORKS PCI 10/100 (DE500-XA) card with full-duplex capability costs only $249, and Intel has announced a US$159 10/100Mbps Ethernet PCI NIC (EtherExpress Pro/100).
• Fast Ethernet switches can provide high port densities at reasonable costs, e.g. a Catalyst 5000 can provide 50 switched Fast Ethernet ports for ~$1,000 per port.

• Single-vendor solution,
• Keep within the CiscoFusion architecture,
• Allow for advanced protocols such as ISL and IP Multicast,
• Allows for other interface cards such as FDDI/CDDI and ATM, and
• Good discount rate.

Scenario 1: Computer Room

1. 2-port Fast Ethernet Interface for Cisco 7000 (CX-FEIP)
2. Catalyst 5000 (WS-C5001) with
3. 1 x 24-port 10BASE-T card (WS-X5010)
4. 1 x 12-port 100BASE-TX card (WS-X5113)
5. about 5 PCI Fast Ethernet interface cards (DE500)
6. about 20 AUI to 10BASE-T adapters
7. UTP patch cords, patch panels etc.
8. some sort of switch management / monitoring software such as CiscoWorks and VLANView or SwitchVision for Windows.

Provides 10 and 100 Mbit/s switched ports for subnet 1, 11 and 82 hosts.

2 x 100 Mbit/s links are used between the router and switch. Cisco IOS 11.x provides the CiscoFusion Inter-Switch Link (ISL) protocol which allows traffic for multiple VLANs to share the same physical link. Since we aren't running 11.x yet, one subnet e.g. subnet 82 will have to share a switch to cisco link with another subnet. This can be supported in the router by using a secondary address on the shared router port.

Digital Alpha machines that have PCI busses can use a DE500 card to provide a 100 Mbit/s full duplex interface.

Other, older server machines, can have a 10 Mbit/s switched port each.

Very low bandwidth hosts, such as the protocol translators, could share one 10 Mbit/s port.

All hosts (or groups of hosts) will be cabled using UTP back to the wiring cabinets in each computer room. From there, trunk UTP cables will run back to a patch panel in the cisco room. The ports on the Catalyst will also be brought to this patch panel, and patched into the machine room trunks as required.

Scenario 1a: Subnet 8 workstations

1. basic Catalyst setup from Scenario 1
2. 1 x 12-port 10BASE-FL card (WS-X5011)
3. DE500 PCI Fast Ethernet interface cards for any new AlphaServers
4. trade back the Kalpana switch for $5,000 credit

The seven or so servers for subnet 8 machines would each be connected to a 10BASE-T port on the Catalyst. A new AlphaServer for subnet 8 could have a DE500 Fast Ethernet interface and be connected to a 100BASE-TX port.

10BASE-FL ports would be used to drive the Fibre-Optic links across to each Unix Workstation lab.

Subnet 8 could share an existing Cisco to Catalyst trunk. Alternatively, until we can use the ISL protocol, subnet 8 should use it's own Cisco to Catalyst link. This could even be a 10 Mbit/s 10BASE-T link.

Scenario 2: Multimedia Subnet

1. 2-port Fast Ethernet Interface for Cisco 7000.
2. Catalyst 5000 with
3. 1 x 24-port 10BASE-T card
4. 1 x 12-port 100BASE-TX card
5. DE500 or similar Fast Ethernet card for Multimedia server
6. 1 x 12-port workgroup switch such as a Kalpana PRO16 (PSPRO16-M041) with a 100 Mbit/s Fast Ethernet uplink port (PSP100T) or a Grand Junction Networks FastSwitch 2800
7. 2 x 100BASE-TX to 100BASE-FX converters (e.g. from LANCAST) if the link to the lab is to be over fibre

The Multimedia server has a 100 Mbit/s Fast Ethernet link into the Catalyst.

Install a 100 Mbit/s Fast Ethernet link between Catalyst (near the Cisco) and the workgroup switch (near the multimedia workstations). Since the Catalyst doesn't yet have a 100 Mbit/s Fast Ethernet over Fibre interface, a 100BASE-TX to 100BASE-FX converter interfaces is required at the Catalyst end.

10 Mbit/s switched Ethernet links run from the workgroup switch to individual workstations.

Support for more than 240 machines in the same IP subnet would be provided by using secondary addresses on the cisco port in the VLAN.

Scenario 2a: Super-size Subnet

1. basic Catalyst setup from Scenario 2
2. DE500 or similar Fast Ethernet card for local fileservers
3. 1 x 12-port 10BASE-FL card

10BASE-FL ports would be used to drive Fibre-Optic links to the existing 10BASE-2 or 10BASE-T repeaters on the different floors of the building.

Using a switch to combine the traffic from multiple 10 Mbit/s LANs into one 100 Mbit/s fileserver port should enable us to happily run more that 60 (or whatever) Windows machines on the one LAN.

We can also use IP secondary addresses on the cisco port in the VLAN to handle more that 240 IP hosts in a VLAN. This should enable us to put the whole community of users in the same VLAN and not have to divide it up into multiple subnets just because there are a certain number of users.