Develcon Electronics DI-1135 Manual de usuario

Orbitor 3000

Ethernet Bridge/Router

Reference Manual

Issue 2

All Software Versions

Part # 168-18806

Contents

SECTION 1 —INTRODUCTION ..................................................................................1-1

THE ORBITOR ETHERNET REMOTE BRIDGE/ROUTER..................................................................................................... 1-1

IP ROUTING AND THE ORBITOR ETHERNET REMOTE BRIDGE/ROUTER.......................................................................... 1-1

ARP—Address Resolution Protocol.......................................................................................................................... 1-2

Proxy ARP ............................................................................................................................................................... 1-2

The Complete IP Connection.................................................................................................................................... 1-2

IP Header Details...................................................................................................................................................... 1-3

Protocol................................................................................................................................................................ 1-4

Time to live.......................................................................................................................................................... 1-4

Header Checksum................................................................................................................................................. 1-4

Fragmentation....................................................................................................................................................... 1-4

Options................................................................................................................................................................. 1-4

Source Routing................................................................................................................................................. 1-4

Route Recording............................................................................................................................................... 1-4

Time Stamps .................................................................................................................................................... 1-4

ICMP Messages........................................................................................................................................................ 1-5

Unreachable.......................................................................................................................................................... 1-5

Redirect................................................................................................................................................................ 1-5

Quench................................................................................................................................................................. 1-5

Ping...................................................................................................................................................................... 1-5

Time and Mask server........................................................................................................................................... 1-5

RIP—Routing Information Protocol.......................................................................................................................... 1-6

Route Tables......................................................................................................................................................... 1-6

Update Mechanism............................................................................................................................................... 1-6

IPX ROUTING AND THE ORBITOR ETHERNET REMOTE BRIDGE/ROUTER....................................................................... 1-7

IPX Addressing ........................................................................................................................................................ 1-7

Network Layer Addressing vs. MAC Addressing.................................................................................................. 1-7

IPX Address Format............................................................................................................................................. 1-7

Network Addresses........................................................................................................................................... 1-7

Node Addresses................................................................................................................................................ 1-8

Socket Addresses.............................................................................................................................................. 1-8

Other IPX Header Information.............................................................................................................................. 1-8

Establishing an IPX Connection................................................................................................................................ 1-9

Service Advertisement Protocol................................................................................................................................ 1-9

SAP Broadcasts.................................................................................................................................................... 1-9

SAP Requests..................................................................................................................................................... 1-10

Server Types........................................................................................................................................................... 1-10

Routing Information Protocol ................................................................................................................................. 1-10

RIP/X Operation................................................................................................................................................. 1-10

RIP/X Broadcasts ............................................................................................................................................... 1-10

RIP/X Requests.................................................................................................................................................. 1-11

RIP/X Metrics .................................................................................................................................................... 1-11

BRIDGING AND THE ORBITOR ETHERNET REMOTE BRIDGE/ROUTER........................................................................... 1-11

The Initial Bridging Process.................................................................................................................................... 1-12

Station Address Learning.................................................................................................................................... 1-12

Learning Local Addresses............................................................................................................................... 1-12

Forwarding..................................................................................................................................................... 1-12

Local Destination Addresses........................................................................................................................... 1-12

Forwarding Unknown Destination Addresses ................................................................................................. 1-13

Unknown Location Update............................................................................................................................. 1-13

Aging Timer........................................................................................................................................................... 1-13

Address Purging................................................................................................................................................. 1-13

Aging Exception................................................................................................................................................. 1-13

Contents (continued)

Filled Address Table............................................................................................................................................... 1-14

ORBITOR ETHERNET BRIDGE/ROUTER FEATURE DEFINITIONS .................................................................................... 1-15

Telnet ..................................................................................................................................................................... 1-15

Link Compression................................................................................................................................................... 1-15

WAN Topologies.................................................................................................................................................... 1-17

Point-to-Point..................................................................................................................................................... 1-17

Multipoint .......................................................................................................................................................... 1-17

Bandwidth On Demand........................................................................................................................................... 1-17

Disaster Recovery............................................................................................................................................... 1-18

Time of Day Connect Application ...................................................................................................................... 1-18

Point-to-Point................................................................................................................................................. 1-18

Multipoint...................................................................................................................................................... 1-19

Disaster Recovery Backup Link.............................................................................................................................. 1-19

ISDN Single Active Link & Dual Active Link........................................................................................................ 1-19

Operating Software Upgrades ................................................................................................................................. 1-19

SECTION 2 —ISDN CONNECTION MANAGEMENT.................................................2-1

Orbitor ISDN Connection Management .................................................................................................................... 2-1

Wide Area Network Topologies Supported........................................................................................................... 2-1

Call Establishment Methods ................................................................................................................................. 2-1

Auto-Call (Time-of-Day Connections).............................................................................................................. 2-2

Address Connect .............................................................................................................................................. 2-3

Manual Call...................................................................................................................................................... 2-3

Combination..................................................................................................................................................... 2-4

Connection Process............................................................................................................................................... 2-4

Protocol Awareness.......................................................................................................................................... 2-5

Suspension Process........................................................................................................................................... 2-5

Interesting Traffic............................................................................................................................................. 2-5

Idle Timer ........................................................................................................................................................ 2-6

Orbitor Session Participation (Spoofing)........................................................................................................... 2-6

Termination Process......................................................................................................................................... 2-7

IP Specifics .......................................................................................................................................................... 2-7

IP Address Connect.......................................................................................................................................... 2-7

Suspension of TCP/IP Sessions ........................................................................................................................ 2-7

RIP—Routing Information Protocol ................................................................................................................. 2-7

IPX Specifics........................................................................................................................................................ 2-8

RIP/IPX and SAP/IPX...................................................................................................................................... 2-8

Suspension of IPX Sessions.............................................................................................................................. 2-8

Server IPX Watchdog Frames....................................................................................................................... 2-8

Client IPX Watchdog Frames....................................................................................................................... 2-8

IPX Serialization Frames.................................................................................................................................. 2-8

SECTION 3 —LINK INTERFACES REFERENCE......................................................3-1

PINOUT INFORMATION .................................................................................................................................................. 3-1

LINK CLOCKING INFORMATION..................................................................................................................................... 3-1

CSU/DSU LINK MODULE INFORMATION ...................................................................................................................... 3-1

Console Pinouts........................................................................................................................................................ 3-2

V.24 & RS232C Link Pinouts................................................................................................................................... 3-3

V.11 & X.21 Link Pinouts........................................................................................................................................ 3-4

RS442 & RS530 Link Pinouts .................................................................................................................................. 3-5

V.35 Link Pinouts..................................................................................................................................................... 3-6

RS232 Null-Modem Cable Configuration................................................................................................................. 3-7

V.35 Null-Modem Cable Configuration.................................................................................................................... 3-8

RS530 Null-Modem Cable Configuration................................................................................................................. 3-9

Contents (continued)

RS530 To RS449 Conversion Cable ....................................................................................................................... 3-10

WAN LINK CONTROL-SIGNAL OPERATION................................................................................................................. 3-11

APPENDIX A —EVENT LOGS...................................................................................A-1

APPENDIX B —PROGRAMMABLE FILTERING......................................................B-1

MAC ADDRESS FILTERING ...........................................................................................................................................B-1

Security ....................................................................................................................................................................B-1

Security—“Filter if Destination”...........................................................................................................................B-2

Security—“Filter if Source”..................................................................................................................................B-3

Security—“Forward if Destination”......................................................................................................................B-4

Security—“Forward if Source”.............................................................................................................................B-5

PATTERN FILTER OPERATORS .......................................................................................................................................B-7

BRIDGE PATTERN FILTERING ........................................................................................................................................B-7

Protocol Discrimination............................................................................................................................................B-7

Protocol Type Field..............................................................................................................................................B-8

Internet Protocol (IP)............................................................................................................................................B-8

Filter all IP Packets ..........................................................................................................................................B-8

IP, and no more................................................................................................................................................B-8

Transport Control Protocol / Internet Protocol (TCP/IP) .......................................................................................B-9

Filter only TCP/IP............................................................................................................................................B-9

Filter all IP without TCP traffic........................................................................................................................B-9

Filter all except TCP/IP....................................................................................................................................B-9

Local Area Transport (LAT).................................................................................................................................B-9

Filter all LAT...................................................................................................................................................B-9

Filter all but LAT.............................................................................................................................................B-9

DEC...................................................................................................................................................................B-10

Filter all DEC.................................................................................................................................................B-10

Bandwidth Conservation.........................................................................................................................................B-10

Ethernet Broadcasting.........................................................................................................................................B-10

Ethernet Multicasting..........................................................................................................................................B-10

General Restrictions................................................................................................................................................B-11

Internet Addresses ..............................................................................................................................................B-11

Ethernet Station Addresses .................................................................................................................................B-11

Mask Combinations............................................................................................................................................B-12

IP ROUTER PATTERN FILTERING.................................................................................................................................B-13

Protocol Discrimination..........................................................................................................................................B-13

IPX ROUTER PATTERN FILTERING ..............................................................................................................................B-13

APPENDIX C —FRAME FORMATS..........................................................................C-1

OCTET LOCATIONS ON A BRIDGED TCP/IP FRAME .......................................................................................................C-1

OCTET LOCATIONS ON A BRIDGED NOVELL NETWARE FRAME .....................................................................................C-1

ETHERNET TYPE CODES .........................................................................................................................................C-2

OCTET LOCATIONS ON AN IP ROUTED TCP/IP FRAME..................................................................................................C-2

OCTET LOCATIONS ON AN IPX ROUTED NOVELL NETWARE FRAME .............................................................................C-3

OCTET LOCATIONS ON A BRIDGED XNS FRAME ...........................................................................................................C-3

Orbitor 3000 Reference Manual—1-1

Section 1 — Introduction

The Orbitor Ethernet Remote Bridge/Router

The Orbitor Ethernet remote bridge/router provides IP and IPX routing combined with a protocol transparent bridge.

This bridge/router combination is often the best solution to linking remotely located LANs where most of the traffic is IP

or IPX with smaller amounts of traffic from other protocols such as NetBIOS or DEC LAT.

The Orbitor Ethernet bridge/router supports the widely implemented Routing Information Protocol, otherwise known as

RIP. RIP support allows the Orbitor Ethernet to interoperate with other vendors’ routers.

The Orbitor Ethernet remote bridge/router will operate as delivered, providing increased LAN performance directly out of

the box without the need for complex pre-configuration. However, in those situations where specific customization is

required, an easy-to-use “hotkey”menuing Bridge/Router Manager console provides access to LAN and Link statistical

information, and control of the network configuration.

With increased LAN and Link management capability, you will be able to detect LAN and Link problems, determine

utilization patterns, and plan for future expansion that will optimize your existing data-communication resources.

The Orbitor Ethernet bridge/router can be thought of as a group of discrete functions combined in a single box. The first

functional module is the LAN interface, which receives all LAN traffic and then decides where individual frames should

be sent: to the IP router, to the IPX router, to the bridge, to the management system, or discarded altogether. After the

LAN interface there are several functional units including the IP router, the IPX router, the bridge, and the management

system. Any traffic that these modules need sent across a link is then sent to the link modules, which control data

coming and going on the WAN ports. The following figure illustrates the relationships between the various component

modules in a Orbitor Ethernet bridge/router.

Figure 1—1Orbitor Ethernet Bridge/Router Block Diagram

The Orbitor Ethernet menu system provides a method to control whether IP & IPX traffic is routed through the router

modules, or bridged through the bridge module along with all other bridged data.

IP Routing and the Orbitor Ethernet Remote Bridge/Router

The Orbitor Ethernet bridge/router may be used to route only between subnets within the same network, or between

different networks.

Network broadcasts sent within a subnet-routed environment will not be forwarded to the other subnets in the network.

The procedure for establishing an IP connection through an IP router is explained on the next few pages.

Introduction

1-2 —Orbitor 3000 Reference Manual

ARP—Address Resolution Protocol

A protocol called ARP (Address Resolution Protocol) is used to determine the MAC address of a particular IP address.

Remember that the MAC address is predefined for each device on the LAN, and the IP address for each device is

assigned according to the network structure.

If the originating station does not know the MAC address of the destination station, a MAC broadcast will be transmitted

onto the LAN asking “Who has IP address 170.22.10.4?”This MAC broadcast is called an ARP request. Because the

ARP request is a MAC broadcast, every device on the LAN will see the frame. The device that has the IP address

170.22.10.4 will respond with a frame to the originating station. The ARP reply frame will include the MAC address of

the destination device.

Now when the two devices wish to send data across the LAN to each other, they will both use the MAC and IP address of

the other device.

Each device on the LAN maintains a table for MAC addresses and IP addresses, called the ARP cache. The ARP cache

contains a list of IP addresses and their corresponding MAC addresses.

Proxy ARP

Each time an originating station does not know the MAC address of a destination station, the originating station sends out

an ARP request. Now if the destination station is on a different network, the router connected to the originating network

will see the frame and look at the IP address being requested.

The router will look in its routing table and see if it has an entry for that IP network address. If the router has an entry,

the router will generate an ARP reply to send back to the originating station. The ARP reply will specify the MAC

address of the router as the MAC address to send frames to for the IP address of the destination station.

The Complete IP Connection

The following are the steps that a frame of data will take when being transmitted from an originating station on an IP

network to a destination station on a different IP network. In this example, the two networks are separated by a third

network with two router hops between the originating network and the destination network.

•Originating station will send an ARP request if it does not have the MAC address of the destination station.

•Local router will see ARP request and send an ARP reply to the originating station with the MAC address of the

local router port.

•Originating station will send the data frame addressed to the IP address of the destination station, and the MAC

address of the local router port.

Introduction

Orbitor 3000 Reference Manual—1-3

•Local router will receive the data frame and strip off the MAC portion. The resulting IP frame will be examined

to determine the destination IP address.

•Local router will look in its routing table to find the IP address of the router to send the IP frame to next. The

local router will see that the destination router is the next router.

•Local router will look in its ARP cache to find the MAC address of the destination router as determined by the IP

address in the routing table.

•Local router will rebuild the complete frame with a new MAC header indicating the MAC address of the

destination router. Remember that the local router does not alter the destination IP address, so the destination IP

address will still be the IP address of the destination station.

•Destination router will receive the data frame and strip off the MAC portion. The resulting IP frame will be

examined to determine the destination IP address.

•Destination router will look in its routing table to find the IP address of the router to send the IP frame to next.

The destination router will see that the destination IP address is on a locally connected network.

•Destination router will look in its ARP cache to see if it has a MAC address for the destination IP address. If it

does not have an entry, the destination router will generate an ARP request. The destination station will send an

ARP reply.

•Destination router will rebuild the complete frame with a new MAC header indicating the MAC address of the

destination station. The destination IP address once again will be unchanged and remain as the destination

station IP address.

•Destination station will receive the data frame and process it.

If the destination station wishes to send a frame back to the originating station, the process will happen in the reverse

direction.

If the path from the originating station to the destination station causes the frame to pass through more than two routers,

the above process will simply be extended to include the interaction between the intermediate routers.

IP Header Details

Every IP header has common fields of information. The layout of the information is always the same. Refer to the

following diagram for a representation of the IP header.

Figure 1—2IP Header

Introduction

1-4 —Orbitor 3000 Reference Manual

Protocol

The protocol section is used to indicate the protocol being used by the transport layer. This could be TCP, UDP,

or something else.

Time to live

The time to live section is used to prevent a frame from traversing the network forever. This field contains a

number (maximum 255) that is set when the frame is originally generated. Each time the frame is passed through

the bridge/router, the bridge/router will decrement the time to live by two. When the time to live reaches zero,

the frame is discarded.

Header Checksum

The header checksum is used to verify the data in the IP header. The IP header is recalculated each time a frame

is passed through a router. The recalculation is necessary because the time to live field is changed.

Fragmentation

Fragmentation occurs when an IP frame must be split up into smaller IP frames. When the originating device

generates the IP frame, the device is not aware of all the paths the frame must traverse to get to the destination

device. If the IP frame is to pass through a network that has small packet capabilities, the IP frame must be split

up and reassembled at the destination device. Each of the fragments is assigned a fragment offset value, which

determines where the fragment fits into the original IP frame.

The Orbitor Ethernet bridge/router will accept fragmented frames directed to itself and reassemble them, but it

will not fragment frames.

Options

There are various options that may be set for any IP frame.

Source Routing

Source routing is used to predetermine the path that the IP frame must travel through the network. There are two

types of source routing: strict source routing and loose source routing.

Strict source routing will contain a list of IP addresses of routers that must be used when the IP frame is sent

through the network. Strict source routing is used mainly to provide some type of data security. Once the IP

frame has reached the destination station, the destination station will take the list of IP addresses from the options

field, reverse them, and use them for a strict route back to the originating station.

Loose source routing will also contain a list of IP address of routers to be used on the path to the destination

station. However, the IP frame may pass through other intermediate routers to get to the next IP address in the

loose source routing list.

Route Recording

Route recording simply keeps a list of all the IP addresses of the routers that the IP frame has passed through on

its way to the destination station.

Time Stamps

The time stamp option is used to record the time at which the IP frame passed through each router on its way to

the destination station.

Introduction

Orbitor 3000 Reference Manual—1-5

ICMP Messages

Internet Control Message Protocol (ICMP) messages are used to perform station and router protocol participation. ICMP

messages are passed between routers, or between routers and stations. There are several different messages, as discussed

below.

Unreachable

The “unreachable”message is sent back to the originating station when the path to the destination network has

disappeared. A destination network may be unreachable because of a broken link, a downed router, a downed

station, or other reasons.

Redirect

The “redirect”message is sent to the originating station when there is a better router to use to reach the

destination network. Because the routers share routing tables, each router has the ability to determine whether it

is the best router to use for network traffic. Once a station receives a redirect, all future IP frames destined for the

particular destination network will be sent to the new router.

Quench

The “quench”message is sent to the originating station when the path to the destination network has become

congested. The originating station will slow down the rate of transmission of frames for an internally (to the

station) predetermined period of time upon receiving a quench message.

Ping

The “ping”message is actually a query status message that may be sent to devices on the LAN to query their

operation status. The ping message is basically a message asking “Are you alive?”The LAN device will reply

with a message if it is active.

Time and Mask server

Two other ICMP messages are used to query the time and/or subnet mask from a particular LAN device. A

message is sent to a LAN device asking for the time or mask, and the device replies appropriately.

Introduction

1-6 —Orbitor 3000 Reference Manual

RIP—Routing Information Protocol

The most important function of the IP protocol is routing. IP routers constantly exchange information keeping their

routing tables up to date. A method of communication is required to ensure compatibility between all IP routers in the

network. RIP is the portion of the IP protocol that is used for router communication.

Route Tables

Each router will maintain a table of network addresses and the appropriate action to take with an IP frame it

receives. A routing table entry will usually consist of the following items:

•Network or sub-network address

•IP address of the next hop router

•Network interface to use to get to the next hop router

•Subnet mask for this network interface

•Number of hops to reach the destination network

•Number of seconds since this route was updated

When a router receives an IP frame, the router will examine it to determine the destination network address. The

router will then look in the routing table, determine the next router to send the IP frame to, and send the frame to

that router.

The selection of the best route path is based solely on the number of hops to the destination network.

Update Mechanism

In order to ensure that the routing tables of all routers in the network are kept up to date, each router will

broadcast its routing table onto each of its locally connected networks. The broadcast of the routing tables occurs

every 30 seconds.

The process of updating a routing table with current information, and deciding which router to use to reach a

destination network, creates a ripple effect of changes through the network. When a router goes down and an

adjacent router determines that the path has disappeared, the remaining adjacent routers on that network must

determine the next path to use to reach the destination network. Each router will now broadcast its new routing

table with the updated information. The updated information will propagate through the network until all routing

tables have been brought up to date. This process is called convergence.

The broadcast of the routing tables is also used as a method of determining whether a router is still alive or has

been removed from the network. If a router has not heard from an adjacent router in 180 seconds, the local router

will mark the adjacent router as unreachable and start to adjust the routing table, if necessary.

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