115 lines
3.7 KiB
Plaintext
115 lines
3.7 KiB
Plaintext
.NC "The Design of the ARGO Network Layer"
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.sh 1 "End System to Intermediate System Routing Protocol"
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.pp
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The following sections describe the design of the End System to Intermediate
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System (ES-IS) Routing Exchange Protocol.
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.sh 2 "Overview"
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.nf
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- protocol involves sending/receiving hello pdus.
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- timers determine
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- when to send information
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- when to discard information
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- want to keep as much of the work outside of kernel
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- only put functions and tables in kernel when necessary
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.sh 2 "Supported Features (brief overview of each)"
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- report configuration (both ES and IS)
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- record configuration (both ES and IS)
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- flush configuration (both ES and IS)
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- query configuration (ES only)
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- configuration response (ES only)
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- request redirect (IS only)
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- record redirect (ES only)
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- flush old redirect (ES only)
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- multicast vs. broadcast (using broadcast only)
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.sh 2 "Kernel Resident Features"
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.sh 3 "Support for PDU Transmission"
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- need mechanism to send/receive PDUs
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- utilize ES-IS socket (like raw socket)
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- socket(AF_ISO, SOCK_DGRAM, ISOPROTO_ESIS)
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.sh 4 "Sending PDUs"
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- sendmsg() used for transmitting PDUS
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- data will be pre-formed ES-IS PDU
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- no checks will be made on the pdu format
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- addr_snpa is the destination (to)
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- before sending, socket must be associated with a particular interface
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this is done via setsockopt():
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ESISOPT_SETIF - option
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buffer is name of interface, ie. "un0"
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.sh 4 "Receiving PDUs"
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- recvmsg() used for receiving PDUs
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- data will be:
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#define ESIS_PDU
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#define ESIS_CONFIG_RESP
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#define ESIS_REDIR_REQ
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struct esis_indication {
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short ei_type; /* type of indication */
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union {
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struct ? config_resp
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struct ? redir_req
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char pdu[0]
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} ei_u;
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}
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- no checks will be made on the pdu format
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- addr_snpa is the source (from)
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.sh 4 "Addressing"
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- ES-IS PDUs are sent to SNPA.
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- addresses used are SN addresses, not NSAP addresses
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- format of msg_name (part of msghdr) struct sockaddr_iso
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afi = 0 /* means special snpa address */
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isoa_u is struct addr_snpa
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struct addr_snpa {
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char sn_addr[7]; /* snpa addr */
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}
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isoa_len is number of bytes of sn_addr that are valid
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- sn_addr may be a unicast or multicast address
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- multicast addresses will be faked via broadcast addresses
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.sh 3 "NSAP to SNPA translation"
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- translation from NSAP to SNAP required for every CLNP PDU sent
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- function provided by iso_nsap_to_snpa
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iso_nsap_to_snpa(ifp, m, nsap, snpa)
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struct ifnet *ifp; /* outgoing interface */
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struct mbuf *m; /* pkt */
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struct sockaddr_iso *nsap; /* destination address */
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char *snpa; /* RESULT: snpa address */
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{
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if (nsap.afi == AFI_SNPAADDR) {
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copy snpa addr from nsap into snpa
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return SUCCESS
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} else {
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scan RIB for (RIB.nsap == nsap)
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if (found) {
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copy RIB.snpa into snpa
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return SUCCESS
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}
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scan RIB for (RIB.type == IS) && (RIB.ifp = ifp)
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if (found) {
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copy RIB.snpa into snpa
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return SUCCESS
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}
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if (ifp allows multicast) {
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/* invoke query configuration function */
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copy ifp.ifaddr.ifa_all_es into snpa
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return SUCCESS
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}
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return FAILURE
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}
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}
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- NSAP to SNPA table resides in kernel so CLNP has quick access
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- entries added/timed-out of table via user level ES-IS daemon
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.sh 3 "Query Configuration Functon"
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- invoked when iso_nsap_to_snpa
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- requires snpa, but
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- does not find a match for dest nsap, and
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- does not find a match for Any IS.
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- clnp packet is sent to address "all ES" as specified in ifnet structure
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(for now, this is just the broadcast address)
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.sh 3 "Configuration Response Function"
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- invoked by clnp_input(), after determining that the packet received is
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destined for one of its NSAPs
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- checks if sn_dst == "all ES" (for now, this is all hex ffs)
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- if true, a copy of packet is made, and passed up to esis_input()
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