Higher Layer Protocols

In general, higher layer protocols (that is, above the network layer) need only be implemented on the source computer system and destination computer system (that is, end nodes). Intermediate nodes (such as the 6611 Network Processor) do not need to interpret higher level protocols as they are transported

transparently within the network and data link layer protocols implemented by the 6611 Network Processor.

However there are several higher layer protocols which are necessary for the 6611 Network Processor to:

• Maintain routing tables used by network layer protocols

• Provide systems management functions

• Support the 6611 Network Processor Data Link Switching function These higher layer protocols are described in the following sections.

Chapter 1. Introduction to Networks, Protocols and Internetworking

7

1.2.5.1 Routing Table Maintenance Protocols

The routing tables used by network layer protocols are maintained by various higher layer protocols. Each of these protocols is specific to a particular protocol suite, and some protocol suites incorporate several alternatives.

Some protocol suites support the partitioning of large networks into smaller networks which can be managed autonomously. These smaller networks are known by various names (depending on the protocol suite) such as areas (used in DECnet), zones (used in AppleTalk), or autonomous systems (used in TCP/IP).

Some protocol suites use different routing table maintenance protocols:

• Within each of these smaller networks

• Between each of these smaller networks

For example the TCP/IP protocol suite uses different protocols within and between autonomous systems. These are called interior and exterior protocols respectively.

The routing table maintenance protocols for each protocol suite include:

• TCP/IP Interior Protocols

RIP (Routing Information Protocol) Hello

OSPF (Open Shortest Path First)

• TCP/IP Exterior Protocols

EGP (Exterior Gateway Protocol) BGP (Border Gateway Protocol)

• NetWare

- RIP (Routing Information Protocol)

• XNS

- RIP (Routing Information Protocol)

• AppleTalk

- RTMP (Routing Table Maintenance Protocol)

• OSI

- IS-IS (Intermediate System-Intermediate System)

Note: The TCP/IP, Netware and XNS protocol suites all use different forms of RIP. That is, TCP/IP RIP, Netware RIP and XNS RIP are three different protocols that happen to have the same name.

The DECnet protocol suite does have an equivalent routing table maintenance protocol; however, it does not have a particular name.

1.2.5.2 System Management Protocols

The 6611 Network Processor uses several higher layer protocols for system management purposes. These are a" drawn from the TCP/IP protocol suite and include:

• FTP (File Transfer Protocol) which is used for the distribution of configuration and software changes to 6611 Network Processors across a TCP/IP network.

8

• RSH (Remote Shell) and REXEC (Remote Execution) which are used to remotely execute commands on a 6611 Network Processor across a TCP/IP network.

• TELNET and RLOGIN (Remote Login) which are used to remotely access the 6611 Network Processor System Manager function across a TCP/IP network.

• ICMP (Internet Control Message Protocol) which is used for various TCP/IP network management purposes such as reporting IP routing errors. ICMP can be used by the PING (Packet InterNet Groper) program to determine if a 6611 Network Processor is reachable across a TCP/I P network.

• SNMP (Simple Network Management Protocol) which is used to manage a network of 6611 Network Processors and other TCP/I P devices across a TCP/IP network from a suitable network management system such as IBM AIX* NetView/6000* for the IBM RiSe System/6000*.

1.2.5.3 Data Link Switching Support

The Data Link Switching function provided by the 6611 Network Processor makes use of a transport layer protocol to provide connections between 6611 Network Processors. The protocol used is TCP (Transmission Control Protocol) which is drawn from the TCP/IP protocol suite. The implementation of the Data Link Switching function is described further in 2.2.3, "Data Link Switching" on page 40.

1.2.6 Addressing

Both data link layer and network layer protocols make use of addresses to transfer information to the correct destination.

Data link layer addresses are used to select which of the nodes connected to the same data link or data link network is the destination for an information transfer that makes use of that data link or data link network.

Network layer addresses are used to specify which node is the ultimate destination for an information transfer, no matter how many data links or data link networks are traversed to perform that transfer.

Data link layer and network layer addresses are described further in the following sections.

1.2.6.1 Data Link Layer Addresses

Each type of data link or data link network uses its own form of data link addresses to distinguish between the various nodes that are attached to a common data link or data link network.

Frame Relay Uses DLCI (Data Link Connection Identifier) addresses which are 10 bits long

Chapter 1. Introduction to Networks, Protocols and Internetworking

9

Some protocol suites provide protocols to determine the data link layer address that can be used to reach a particular network layer address. For example the TCP/IP protocol suite uses ARP (Address Resolution Protocol) to derive the data link layer address from a network layer address.

1.2.6.2 Network Layer Addresses

Each protocol suite uses its own form of network layer addresses which are used to distinguish between the various nodes throughout a network. The network layer addresse.s used by various protocol suites are:

TCP/IP

Uses a two-part address consisting of a 4-byte network number and a 6 byte host number

Uses a two-part address consisting of a 4-byte network number and a 6 byte host number

For example the TCP/IP protocol suite uses a different network layer address for each data link or data link network interface.

Some protocol suites use the data link layer address as part of the network layer address. For example the XNS protocol suite uses the data link layer address for the host number part of the network layer address.

Some protocol suites provide a pseudonym capability for network layer

addresses which allow an easily understood plain text name to be used in place of a network layer address. Such names can be translated into network layer addresses using protocols designed for that purpose.

For example the AppleTalk protocol suite uses NBP (Name Binding Protocol) to translate names into network layer addresses. Similarly the TCPIIP protocol suite uses Domain Name Servers to translate names into network layer addresses.

10