Chapter Thirteen

The Other Protocols

Objectives

• You’ll get a brief overview of– IPX/SPX– NetBEUI– Appletalk

• How each protocol handles addressing• The pros and cons of each protocol

IPX/SPX• Internetwork Packet Exchange/Sequenced Packet

Exchange – Developed by Xerox in the early 80s– Adopted and tweaked by Novell to become their protocol

of choice in NetWare servers until Version 5.– IPX/SPX is designed to provide transport services for data

over the network• IPX is a connectionless protocol• SPX provide a reliable connection-oriented services.

Addressing in IPX/SPX• An IPX/SPX address consists of three separate

components:– A network number: 32 bits assigned by administrator and

bound to a specific network– A node number is derived from the 48-bit MAC address.– The network number and node address form the station

address.

Addressing in IPX/SPX• A socket number: 16 bits

– assigned to the process or application running on the device by NOS.

– This is NOT the same as the sockets discussed in the Transport layer.

– When a process needs network access, it will request a socket number. Once that number is assigned, any packet containing that socket number will be passed on to that process.

Reserved IPX/SPX Sockets

IPX Packet Structure• IPX/SPX packet consists of a 30-bye

header and 0-1470 bytes payload.• IPX/SPX packet will be encapsulated

into the frame created by the hardware protocol.

IPX Packet Structure

Configuring IPX/SPX

• IPX/SPX is a protocol designed to be independent of the hardware protocol used.– It supports Ethernet, Token Ring and FDDI.– IPX/SPX packet is inserted as the payload for whatever

frame type the network uses.

• IPX/SPX is sensitive about the frame type. Your IPX configuration must be configured to use the correct frame type.– Auto Detect usually works pretty well.

Frame Types• IPX/SPX recognizes four different types of Ethernet

Frame and two different types of Token Ring frame• 802.3 (Raw)

– The typical Ethernet frame

• 802.2– An older frame type used by non-Ethernet protocols

• Ethernet II• Ethernet SNAP• 802.5 Token Ring • Token Ring SNAP

Configuring IPX/SPX• The Network address is where

you fill in the 32-bit network number. The default is all 0s.

• If no network number is statically assigned, the host will send out a broadcast looking for a SAP server.

• The SAP server will assign an address.

Routing in IPS/SPX• If the network numbers of both transmitting and receiving

devices are the same, no routing is necessary.

• If a packet isn’t addressed to the local network, the transmitting station will broadcast a RIP packet.– Available routers with access to the target network number respond

with their node address and the number of hops to target.– Transmitting workstation picks the router with the fewest hops and

transmits the packet.

Routing in IPS/SPX

• When a router receive an IPX/SPX packet, it will perform the following actions:– The router will check the Transport Control field. If the

value becomes 16 when incremented, it discards the packet unless it is an NLSP packet. • NLSP can be configured to support up to 127 hops

– Next it checks the Packet Type field. If the packet type is NetBIOS and Transport control field was incremented to 8, the packet is discarded.

– Otherwise, the router compares the Destination Network number to its routing tables and transmit the packet through the appropriate interface.

Pros and Cons of IPS

• Pros– Light overhead on the individual workstations– Very easy to configure and hard to mess up

• Cons– Very HEAVY overhead on the network as a whole because

of too many broadcast packets.• Workstation broadcasts to find routers, router broadcasts to find

other routers, and server broadcast advertisement of service they offer.

– No any governing body to manage the network numbers. Network administrator picks up the network number as he/she desires

NetBEUI

• NetBIOS Enhanced User Interface– Originally developed by IBM– Developed by Microsoft for early versions of NT 3.51– A Layer 2 protocol– No longer supported by Microsoft

• XP does not install NetBEUI by default, but the protocol can be added from the installation CD.

Pros and Cons of NetBEUI

• Pros– Easy to configure• All you need is to put all workstations on the same

workgroup, but make sure they have different names.

– Extremely fast with low overhead on network and workstations

• Cons– Not routable

AppleTalk

• Developed by Apple Computer Corporation• Has a lot of similarities to TCP/IP– Layered functionality– A robust collection of related protocols

• Moves data in datagrams

Addressing in AppleTalk

• Each host is assigned a node ID and an entity name.– The Node ID is similar to the IP address.– The entity name is similar to a NetBIOS name.– The Name Binding Protocol (NBP) resolves node IDs and

entity names to MAC addresses.• Networks are numbered (like in IPX/SPX) with 16-bit

network numbers.– AppleTalk only supports network number from 0 to

65,534. 65,535 is reserved.

Some AppleTalk Protocols (1 of 3)

• Datagram Delivery Protocol (DDP) provides point-to-point delivery of user data.– DDP packet can contain either a short header or a long header

• Data intended for the local network requires only the short header which includes fields that define the source and destination sockets; the frame type and length.

• Data needs to be routed, a long header will be used which includes field that defines source and destination networks, hop count, and checksum

• If hop count exceeds 16, the datagram is discarded.

Some AppleTalk Protocols (2 of 3)

• Routing Table Maintenance Protocol (RTMP) allows routers to dynamically build routing tables by exchanging known network numbers and accessibility between routers.

• AppleTalk Echo Protocol (AEP) is Apple’s version of ICMP.

Some AppleTalk Protocols (2 of 2)

• Connection-oriented protocol:– AppleTalk Transaction Protocol (ATP) is used for small

amount of data– AppleTalk Data Streaming Protocol (ADSP) provides jitter-

free delivery of multimedia. ADSP is used to transmit the large amount of data

• Connectionless protocol: Datagram Delivery Protocol (DDP)

• AppleTalk Session Protocol (ASP) opens, maintains, and closes sessions.