6/1/991 Internetworking connectionless and connection-oriented networks Malathi Veeraraghavan Mark Karol Polytechnic UniversityBell Labs. Outline: »Why internetwork? »Prior work »Our proposal

6/1/992 Why internetwork? Router Switch Endpoint Connectionless (CL) NetworkCL Network Connection-Oriented (CO) Network

6/1/993 Switching modes Networking modes Problem Statement Applications at endpoints start sending data without warning in connectionless networks CO networks need a connection setup phase So how do the gateways cope with the traffic arriving from the CL networks without time to set up a connection? Connectionless Connection-oriented Packet-switching Circuit-switching IP ATM Telephony network, SONET/SDH, WDM

6/1/994 Use provisioned connections Use provisioned connections through CO network –Suitable for some cases Provisioned connections: set up a priori based on anticipated traffic Switched connections: set up on demand as traffic arrives CO Network CL Network

6/1/995 Switched connections Need switched connections for some cases – CL applications have an application-level handshake that can be used to trigger connection setups e.g., interconnecting an Internet telephony PC to a telephone e.g., H.245 signaling to Q.931 signaling through the PSTN phone CO Network Switch CL Network Router Endpoint Gateway

6/1/996 Prior work Interesting case - Case 3 –A choice exists of which network to use Existing solutions: –MPOA (Multi-Protocol Over ATM) –MPLS (Multi-Protocol Label Switching) CO Network CL Network

6/1/997 Solutions - MPOA MPOA: –Overlay model –Routing data not shared –Good solution if choice to use CO network made based on application needs (e.g., interactive sessions with long holding times) CO Network CL Network SETUP Interactive application (long-lived flow; if flow classifier is set to use CO network for this flow type) IP packet

6/1/998 Solutions - MPOA MPOA: –Not a good solution if either CL or CO network can be used for a given application (e.g., large bulk-data transfers) Large bulk-data transfers can be handled by either network - if flow classification does not detect this as a flow to be handled by the CO network CO Network CL Network IP packet Does not take advantage of shorter path through the CO network

6/1/999 Solutions - MPLS MPLS: –Peer model –Routing data is shared –Requires every CO switch to also be a CL router –Consider same example as last slide - large bulk-data transfer that could go either way CO /CL Network CL Network IP packet Packets will be forwarded in CL mode while connection is being set up Gateway will select CO network because path is shorter IP packet SETUP IP packet SETUP IP packet SETUP IP packet SETUP

6/1/9910 Proposed solution Peer model Routing data is shared –How is this done: routing-related actions But, not all nodes in the CO network need to have CL capability Problem created: –Data arrives from the CL endpoints into the gateway before connections are set up –User-plane actions

6/1/9911 Routing related actions Gateways running OSPF connected by a CO network (non- broadcast network) announce point-to-point links between gateways R1 S1 R2 R4 R7 R5 R3 R6R6 S4 S5 S3 S2 CL Network CO Network GW1 GW2 GW3 Note: switches have no CL capability

6/1/9912 Routing related actions Topological view of each router and gateway R1 R2 R4 R7 R5 R3 R6R6 CL Network GW1 GW2 GW Shortest path from R4 to R7 is via GW3 and GW2 User data packets from R4 to R7 arrive at GW3 even before connection is set up

6/1/9913 User-plane actions IP datagrams arrive at the gateway to be carried through the CO network when no connection exists through it. –IP datagram could be carrying a TCP segment –IP datagram could be carrying a UDP datagram CO network used only for flows classified as needing connections or those that can be handled on either network

6/1/9914 For flows for which the CO network is to be used TCP segment –If it is a SYN segment, hold it up, set up connection SYN-related time-outs are large (5 sec) –If it is a data segment, then send zero-window acknowledgment to halt data if persist timers get routed through some other path and data arrives before connection is set up, send another zero-window ack.

6/1/9915 For flows for which the CO network is to be used UDP datagram –For applications with user-level message exchange, hold up such messages and set up connection (e.g., H.245 open logical channel) –For applications without such exchanges use source routing to override default routes use small-bandwidth provisioned pipes

6/1/9916 Applications Bulk-data e.g. ftp, smtp, http Interactive e.g., telnet, rlogin, telephony Packet-switched CO networks CL (packet-switched) networks Small amounts of data transfer Large amounts of data transfer Circuit-switched or CL networks Streaming e.g., live or stored audio or video Circuit-switched (CO) networks Peer model needed for this case

6/1/9917 Protocol conversion vs. protocol encapsulation ATM or label overhead incurred on connection with protocol encapsulation (+ TCP ACKs overhead) This can be avoided with protocol conversion Much simpler transport-layer protocol can be used in CO network since the network nodes now maintain state and congestion control (instead of state information being maintained at endpoints) Can use protocol conversion in switched mode Drawback: TCP state information about many connections needs to be held at the gateways Feasibility as yet untested.

6/1/9918 Conclusions For applications whose data can be carried in either the CL network or CO network, internetworking should allow for the exchange of routing information (peer model) Requiring all CO nodes to have CL capability seems too constraining (an MPLS requirement) Hence, our proposed solution: –Share routing data –“Halt” or “turn back traffic” while setting up connections