System information

Troubleshooting Banyan VINES 13-293
RTP
• Transport control—Consists of several subfields. If the packet is a broadcast packet, two
subfields are provided: class (bits 1 through 3) and hop-count (bits 4 through 7). If the packet is
not a broadcast packet, four subfields are provided: error, metric, redirect, and hop count. The
class subfield specifies the type of node that should receive the broadcast. For this purpose, nodes
are broken into various categories having to do with the type of node and the type of link the node
is on. By specifying the type of nodes to receive broadcasts, the class subfield reduces the
disruption caused by broadcasts. The hop count subfield represents the number of hops (router
traversals) the packet has been through. The error subfield specifies whether the ICP protocol
should send an exception notification packet to the packet’s source if a packet turns out to be
unroutable. The metric subfield is set to 1 by a transport entity when it needs to learn the routing
cost of moving packets between a service node and a neighbor. The redirect subfield specifies
whether the router should generate a redirect (when appropriate).
• Protocol type—Indicates the network- or transport-layer protocol for which the metric or
exception notification packet is destined.
• Destination network number, destination subnetwork number, source network number, and
source subnetwork number—Provide VIP address information.
RTP
RTP distributes network topology information. Routing update packets are broadcast periodically by
both client and service nodes. These packets inform neighbors of a node’s existence and indicate
whether the node is a client or a service node. Service nodes also include, in each routing update
packet, a list of all known networks and the cost factors associated with reaching those networks.
Two routing tables are maintained: a table of all known networks and a table of neighbors. For
service nodes, the table of all known networks contains an entry for each known network except the
service node’s own network. Each entry contains a network number, a routing metric, and a pointer
to the entry for the next hop to the network in the table of neighbors. The table of neighbors contains
an entry for each neighbor service node and client node. Entries include a network number, a
subnetwork number, the media-access protocol (for example, Ethernet) used to reach that node, a
local-area network (LAN) address (if the medium connecting the neighbor is a LAN), and a neighbor
metric.
RTP specifies four packet types:
• Routing update—Issued periodically to notify neighbors of an entity’s existence.
• Routing request—Exchanged by entities when they need to learn the network’s topology quickly.
• Routing response—Contains topological information and is used by service nodes to respond to
routing request packets.
• Routing redirect—Provides better path information to nodes using inefficient paths.
Each RTP packet has a 4-byte header consisting of the following 1-byte fields:
• Operation type—Indicates the packet type.
• Node type—Indicates whether the packet came from a service node or a nonservice node.
• Controller type—Indicates whether the controller in the node transmitting the RTP packet has a
multibuffer controller.
• Machine type—Indicates whether the processor in the RTP sender is fast or slow.
Both the controller type and the machine type fields are used for pacing.