                         3Com (R) Corporation
                     EtherDisk (R) Diskette for the
        3C90X Fast EtherLink XL/EtherLink XL Bus Master NIC Family
                     Fast IP Questions and Answers



Q:  What is Fast IP?

A:  Fast IP is an innovative software-based solution that provides an easy
    and low cost mechanism to improve performance on today's switched
    networks. Fast IP allows end systems (desktops and servers) to
    discover switched, Layer 2 communication paths. By creating switched
    short-cuts, Fast IP allows end stations to bypass the router and
    transfer data across wire-speed switched paths. Fast IP is part of
    3Com's DynamicAccess software, an advanced network driver that brings
    intelligence to the end systems to provide improved network performance
    and control.

Q:  What are the motivation & benefits of Fast IP?

A:  Today's networks are evolving to an Intranet based model where network
    managers are not able to predict traffic flows any more and where IP is
    becoming the predominant network protocol. Most of the network platforms
    in place today relay on general purpose, CPU-based routers to provide
    inter-subnet communication. With the exponential increase of network
    users, faster connections, more demanding applications and
    omnidirectional traffic flow, those routers are becoming bottlenecks
    that slow down the network and reduce users productivity.

    Fast IP delivers a mechanism to improve network performance by bypassing
    those router bottlenecks. By allowing desktops and servers to
    automatically find available switched paths to communicate at
    wire-speeds, Fast IP delivers dramatic improvement over router's
    performance. Still, Fast IP maintains the control of routing. Initial
    Fast IP connection requests traverse the router on initiation, where
    net managers can configure traffic policies. Easy to implement, Fast IP
    is a software based technology that is available for 3Com NICs today.

Q:  What is the performance gain when using Fast IP?

A:  The fact that Fast IP bypasses the router in any communication provides
    increased performance in switched networks even if there are just a
    small number of network nodes using Fast IP. The performance gain
    obtained when deploying Fast IP is directly related to traffic load on
    the backbone router. The more traffic is pumped to it, the bigger the
    latency and response time and the higher the performance gain. Internal
    tests show performance increases in the order of 600% when routers are
    loaded at 70 to 75%.

Q:  How does Fast IP work?

A:  Fast IP leverages the processing power of the end station. Based on data
    to be forwarded to a separate subnet: 

    The end system will issue an NHRP request. The NHRP request is a
    standard IP format packet with source and destination MAC and IP
    addresses. Contained in the data portion of the packet is the source end
    system's MAC address.
 
    The NHRP packet is forwarded to a router in accordance with normal
    intersubnet forwarding policies. The router retains its function as a
    control point and filters or forwards the packet according to configured
    policies. 

    The destination station, also running Fast IP, recognizes the NHRP
    request and issues an NHRP response directly to the originating source
    end system using the source MAC address received in the data portion of
    the NHRP request. 

    When the NHRP reply is received by the originating source end system, it
    will then redirect data packets directly to the destination end system
    using its MAC address, rather than going through the router, resulting
    in wire-speed switching. 

    The NHRP request-response process happens in parallel to data traffic
    flow going through the router. Besides providing traffic control, this
    process assures that data communication will not be interrupted while
    the Fast IP short-cut is being established. If there is no switched path
    available between end stations, traffic will continue flowing through
    the router.

Q:  What level of security is provided by Fast IP?

A:  Fast IP relies on the router's configuration for security. Since the
    first NHRP packet flows through the router, any restriction or filter
    that has been configured on it will be applied. Communications that
    were not allowed to happen before will not take place with Fast IP
    since they follow the same routed path at initiation. Fast IP short-cuts
    are initiated per IP session. Therefore, even in the case that two
    different applications operate on the same server, there will be a Fast
    IP request per application. If the source station is restricted to
    either one, the router will not forward the request to that server and
    the Fast IP short-cut will not succeed for that application, whereas the
    other application's connection can be set up for a short-cut.

Q:  How to position Fast IP and how does it contrast to Layer 3 Switching?  

A:  3Com is a long time leader in NICs and Layer 3 switching. Layer 3
    Switches are designed to replace or displace the bottlenecked router
    moving it to the edge of the network for LAN/WAN use where forwarding
    performance is less of an issue.  Layer 3 switches are multiprotocol and
    allow higher level of  security, plus they also offer advanced features
    like bandwidth allocation and, in conjunction with DynamicAccess
    software, end-to-end LAN Traffic Prioritization (CoS). Fast IP is
    designed to improve network performance in today's environments where
    the router is a bottleneck, extending existing network investment.
    The target customer for Fast IP are those networks that have a switched
    infrastructure but rely on a traditional backbone router to provide
    inter-subnet traffic communication. These customers want to improve
    network performance but have budget limitations or are not ready to
    displace the router. With Layer 3 switching and Fast IP, 3Com offers a
    wide range of solutions to meet customers' needs.

Q:  Is Fast IP a proprietary 3Com solution for 3Com NICs?

A:  Fast IP is a solution based on the IETF NHRP (Next Hop Resolution
    Protocol) draft. This ensures that Fast IP can work over existing
    network devices (switches and routers), both 3Com and non-3Com. Fast IP
    will also support the IEEE 802.1p/Q specification, providing a standard
    solution to improve traffic forwarding over 802.1p enabled switches.

Q:  When will Fast IP be available for other vendors NICs?

A:  The first release of Fast IP is part of DynamicAccess software release
    1.2 and it is focused on our current 3Com customers. Therefore, it works
    on 3Com Ethernet XL and Fast Ethernet XL NICs only. With DynamicAccess
    Software release 1.5 (1QCY98) Fast IP will be available for other 3Com
    Ethernet cards as well as for customers with non-3Com Ethernet NICs. 

Q:  When will Fast IP be available for UNIX systems (e.g., Sun, HP, IBM,
    Silicon Graphics, etc.)?

A:  We are currently in discussions with a number of UNIX systems vendors.
    Announcement of their support for Fast IP will be made soon.  

Q:  Does Fast IP work over ATM?

A:  Yes. Although we do not support short-cuts between ELANs today,  Fast IP
    will create short-cuts where multiple subnets are within the same ELAN.
    The reason why Fast IP does not short-cut between ELANs is that in
    sending the NHRP reply, it will be contained to the senders ELAN.  3Com
    is working on a software upgrade which will assist Fast IP in
    short-cutting between ELANs. This software will be available in 1Q98 as
    a free upgrade for the CB7000 family.

Q:  When will Fast IP be available on ATM and FDDI NICs?

A:  DynamicAccess software will be available for ATM and FDDI NICs at a
    later release in 1998.

Q:  What other protocols are supported by Fast IP?

A:  The use of IP as the main protocol has increased over the last years and
    it is expected to be the dominant protocol in customer networks. Because
    of the performance issues that this brings, Fast IP is targeted to solve
    traffic problems for IP networks.

Q:  What are the end system requirements for Fast IP?

A:  Fast IP will be supported on desktops and servers running NDIS 3 network
    drivers. Therefore Win95, Win NT 3.51 and Win NT 4.0 systems will be able
    to support it. There are no special requirements for other network devices
    such as routers or switches in order to support Fast IP. There will be
    support for NDIS 3.0, 4.0 and 5.0, NetWare and UNIX drivers in 1998.

Q:  What are the network configuration requirements for Fast IP?

A:  Fast IP is designed to bypass the router, particularly where the router
    is a bottleneck, as well as to leverage the switched infrastructure. For
    Fast IP to create short-cuts around routers, there must be a switched
    path between source and destination.

Q:  Do I need any hardware upgrades to support Fast IP?

A:  No. Being software-based, Fast IP can be implemented in any network
    regardless of the switching and routing infrastructure that is in place. 

Q:  What types of applications will benefit from Fast IP?

A:  Fast IP will show dramatically improved performance for long lasting
    communication flows or for applications that make frequent use of a
    intersubnet resource. Before issuing a short-cut request, Fast IP waits
    for a short number of packets are sent through the routed path
    eliminating unnecessary connection requests for short-lived flows such
    as web-browsing.  In addition  Fast IP periodically ages out unused
    short-cuts.  Therefore the type of applications which will benefit from
    Fast IP most are long lasting traffic flows, e.g., files transfers,
    server backup, document imaging, etc.  Also applications which send out
    frequent periodic updates such as stock updates, manufacturing equipment
    status updates, hospital equipment monitoring updates, etc. will use
    Fast IP as long as the short-cut address is contained in the address
    cache.

Q:  How many short-cuts are maintained in cache memory?

A:  The number of short-cuts per station is 256.

Q:  How do we compare ICMP Redirect Message function to Fast IP?

A:  ICMP (Internet Control Message Protocol, RFC 792) and is an integral
    part of IP. ICMP is necessary for reporting errors occurred when
    processing IP datagrams. ICMP messages are several and provide
    information to solve datagram delivery problems. Among those messages,
    the Redirect Message has been mistakenly compared to Fast IP as an
    existing IP mechanism to provide short-cuts in router-based networks.

    The ICMP Redirect Message is used when more than one router is attached
    to a LAN. End stations typically have only one default router. The
    default router (also called a default gateway) is used when sending
    packets to destinations that are not on the end station's local LAN. The
    end station sends all non-local traffic to its default router, which
    then forwards it to its destination. If this router can tell (by
    information learned from its routing protocols) that another router on
    this LAN is closer to the destination, it uses the ICMP Redirect message
    to tell the end-station that when talking to this destination it should
    use a different egress router. 

    Fast IP provides a mechanism to discover switched paths across corporate
    networks to provide improved performance (by minimizing router hops).
    ICMP Redirects only optimize the exit path for traffic from an
    end-station to a non-local destination, but all the non-local traffic
    must still cross at least one router, even if there is a layer 2
    switched path available.

Q:  Will I see an increase in CPU utilization with Fast IP.

A:  In a Fast IP enabled network you will see an increase in CPU utilization
    at the client when you enable Fast IP. This is due to the increased
    throughput on the wire achieved with Fast IP. If your system has limited
    CPU resources you may want to leave Fast IP disabled.


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