An efficient approach to distance-based loop-free routing is introduced called THOR (Transitive Hop-Ordered Routing) that, in contrast to all prior distributed routing algorithms and routing protocols, works correctly in the presence of negative link weights. THOR is shown to provide loop-free routing and to converge to shortest paths within a finite time. THOR is compared with OSPF using the ns-3 simulator for the case of minimum-hop routing, and the simulation results show that the approach used in THOR leads to faster convergence and less signalling overhead.

A new approach is introduced to provide multicast delivery services in wireless networks and IoT deployments without the need to deploy any multicast routing protocol. The approach consists of allowing Internet Group Management Protocol (IGMP) messages to traverse multiple hops to allow routers to express their interest in receiving traffic from multicast groups. The proposed variant of IGMP with multi-hop interests that we call IGMM (for Internet Group Message Multicast) replaces the role of a multicast routing protocol and builds multicast forwarding tables used in the data plane for multicast traffic in much the same way that some information-centric networking (ICN) proposals do.

A new family of algorithms for loop-free routing over multiple paths based on path identifiers is introduced. It is shown that different types of path identifiers can be used to attain loop-free routing if total ordering is established among such identifiers. A path identifier can range from the path itself to a succinct representation of it that need not be unique. POLAR (Path-Ordered Loop-free Algorithm for Routing) is presented as an example in which each router labels its shortest distance to each destination with a path identifier consisting of the number of hops and the identifier of the second-to-last hop along its least preferred loop-free path to that destination. POLAR is shown to converge to shortest paths without ever creating loops, and to be able to converge faster than routing protocols like OSPF depending on the type of topology changes taking place in a network.

The Acyclic Source-Tree Routing Algorithm (ASTRAL) is introduced to provide loop-free multipath routing in computer networks. With ASTRAL, routers share link-state information only about those links used in their paths to destinations rather than complete topology data, and without requiring periodic messaging. ASTRAL attains loop freedom by making routers coordinate with their immediate neighbors so that they change their next hops to destinations only after routers verify that the data in their topology databases are consistent with the topology data stored at their neighbors. ASTRAL is proven to guarantee loop-free routes at every instant and to converge to shortest paths within a finite time. ASTRAL is shown to be at least as efficient as the ideal link-state algorithm, more efficient than existing link-state routing protocols like OSPF and IS-IS, and more efficient than DUAL, which is the basis of EIGRP.

The congestion-control mechanisms currently implemented in different variants of the Transmission Control Protocol (TCP) do not account for the possibility that an inherent topology change is the cause of changes in the perceived end-to-end round-trip time (RTT) in a TCP session, rather than network congestion. This results in low throughput and inefficient use of the available bandwidth. We introduce TCP-RTA (TCP Real-time Topology Adaptiveness), a TCP variant that dynamically detects a topology change and in real-time adapts to an appropriate congestion-control strategy in order to maximize the effective use of the total available bandwidth. Simulation results indicate a throughput increase of more than 35% in scenarios involving dynamic topology changes in the midst of a TCP session.

The basic design of the Named Data Networking (NDN) architecture is shown to incur problems, in that Interests (content requests) may go unanswered even if content is available in the network, and Pending Interest Tables (PIT) are shown to provide limited performance benefits in the presence of in- network caching. A new approach to content-centric networking is introduced that eliminates the need to maintain PITs while providing the benefits sought by NDN. Content-Centric Networking with Data Answer Routing Table (CCN-DART) replaces PITs with Data Answer Routing Tables (DARTs) to forward Interests that do not state their sources. The size of a DART is proportional to the number of routes used by Interests traversing a router, rather than the number of Interests traversing a router. It is shown that undetected Interest loops cannot occur in CCN-DART, and that Interests and responses to them are forwarded correctly independently of the state of the network. The results of simulation experiments comparing CCN-DART with NDN using the ndnSIM simulation tool show that CCN-DART attains similar or better latencies than NDN when no looping problems occur in NDN, while using a similar number of Interests and storing an order of magnitude fewer forwarding entries.

A sufficient condition for loop-free routing is introduced based on path labels. A path label consists of the identifier of the first node and hop-count length of a path to a destination. This condition is applied to the policy mechanisms used in BGP, which results in BGP-ELF (BGP Enhanced for Loop Freedom). BGP-ELF uses updates, queries, and replies based on path labels to attain multi-path loop-free and stable routing across autonomous systems without the need for path vectors.

CSMA with collaborative indexing (CSMA/CI) is introduced, in which nodes collaborate with one another using carrier sensing and short signaling packets to establish collision-free schedules without the need for time slotting or the definition of transmission frames as in TDMA. The throughput of CSMA/CI is compared with the throughput of TDMA with a fixed transmission schedule, ALOHA, CSMA, and CSMA/CA analytically and with simulation experiments.

OPERA is a framework recently introduced that formalizes routing etiquettes based on path information. New rules derived from OPERA to provide total ordering among paths are added to the policy mechanisms used in IBGP and EBGP, which results in OPERA-based BGP (OBGP). OBGP is a complete loop-free inter-domain multi-path routing solution based on IBGP and EBGP. OBGP is proven to be stable and loop-free at every instant. Well-known examples of systems in which IBGP and EBGP do not converge are used to illustrate the benefits of OBGP.

A new approach to loop-free shortest-path routing is introduced that uses distance vouchers that attest to the acyclic nature of paths. Routers search and find new shortest paths to destinations without ever creating routing loops by trusting updates originated by routers that vouch being closer to destinations. The new approach is shown to converge faster than prior loop-free shortest-path routing methods.

ALOHA with priority acknowledgments (ACK) is transformed into a collision-free channel access method by increasing the amount of working memory capacity with which communicating nodes remember each node that has requested to join the channel successfully. This results in ALOHA-NUI, for neighborhood understood index. The throughput of ALOHA-NUI is compared with the throughput of TDMA with a fixed transmission schedule, ALOHA with priority ACK's, and CSMA with priority ACK's analytically and by simulation. ALOHA-NUI is shown to attain the high throughput of collision-free transmission scheduling methods that usually require clock synchronization while maintaining most of the simplicity of ALOHA with priority ACK's.

We introduce THORP (Totally Hop-Ordered Routing Procedure), a simple distributed algorithm for minimum-hop routing that works in much the same way as traditional distance-vector routing algorithms do. THORP eliminates routing-table loops by having routers choose as their next hops to destinations those neighbor routers that are totally ordered based on their current distances, without requiring their next-hop routers to correspond necessarily to minimum-hop paths. THORP is shown to be loop-free, to converge to minimum-hop distances within a finite time, and to be faster than the Diffusing Update Algorithm (DUAL), which is the only loop-free shortest-path algorithm that has been used successfully in practice and is part of Cisco’s EIGRP.

The Dominant-Distance Routing Information Protocol (DRIP) is introduced for quality-of-service (QoS) routing based on multiple criteria and is proven to be loop-free at every instant and capable of converging to optimal routes if they exist. DRIP is based on the exchange of updates and queries stating reference routing-metric values for destinations. Simulation experiments based on ns3 are used to compare DRIP against the Non-Restarting Vectoring Protocol recently proposed by Sobrinho and Ferreira, as well as OSPF and RIPv2. The results demonstrate that DRIP provides loop-free routing based on multiple performance and policy criteria as efficiently as routing protocols for shortest-path routing.

A new adaptive transmission protocol is introduced to improve the performance of slotted ALOHA. Nodes use known periodic schedules as base policies with which they collaboratively learn how to transmit periodically in different time slots so that packet collisions are minimized. The Adaptive Policy Tree (APT) algorithm is introduced for this purpose, which results in APT-ALOHA. APT-ALOHA does not require the presence of a central repeater and uses explicit acknowledgements to confirm the reception of packets. It is shown that nodes using APT-ALOHA quickly converge to transmission schedules that are virtually collision-free, and that the throughput of APT-ALOHA resembles that of TDMA, where slots are pre-allocated to nodes. In particular, APT-ALOHA attains a successful utilization of time slots- over 70% on saturation mode.

A new transport protocol is introduced to increase the responsiveness of the network to congestion. The new transport protocol, QUCO, reacts to congestion by selectively dropping off parts of a payload packet (combined with mitigation mechanisms to handle the loss of part of the payload). This packet trimming scheme greatly reduces the variations in the number of the packets going through the network. This allows to set tighter targets on the number of packets in flight and on the depth of the switch buffers. QUCO has less delay and much less delay variations than TCP. The resulting reduction in jitter is extremely useful, especially for media distribution.

Named-Data Transport (NDT) is introduced to provide efficient content delivery by name over the existing IP Internet. NDT consists of the integration of three end-to-end architectural components: The first connection-free reliable transport protocol, the Named-Data Transport Protocol (NDTP); minor extensions to the Domain Name System (DNS) to include records containing manifests describing content; and transparent caches that track pending requests for content. NDT uses receiver-driven requests (Interests) to request content and NDT proxies that provide transparent caching of content while enforcing privacy. The performance of NDT, the Transmission Control Protocol (TCP), and Named-Data Networking (NDN) is compared using off-the-shelf implementations in the ns-3 simulator. The results demonstrate that NDT outperforms TCP and is as efficient as NDN, but without making any changes to the existing Internet routing infrastructure.

The Internet Transport Protocol (ITP) is introduced to support reliable end-to-end transport services in the IP Internet without the need for end-to-end connections, changes to the Internet routing infrastructure, or modifications to name-resolution services. Results from simulation experiments show that ITP outperforms the Transmission Control Protocol (TCP) and the Named Data Networking (NDN) architecture, which requires replacing the Internet Protocol (IP). In addition, ITP allows transparent content caching while enforcing privacy.

ALOHA with Queue Sharing (ALOHA-QS) maintains most of the simplicity of ALOHA with priority acknowledgments (ACK) and attains the high throughput of transmission scheduling methods that require clock synchronization. Channel access with ALOHA-QS consists of a sequence of queue cycles, with each cycle having one or multiple collision-free transmissions by nodes that have joined the transmission queue and a single request turn to join the queue. The signaling of ALOHA-QS entails adding to packet headers the size of the shared queue, the position of the sending node in the queue, a bit indicating the end of transmissions by the transmitting node, and a bit stating whether or not a new node joined the queue successfully. The throughput of ALOHA-QS is compared with the throughput of TDMA with a fixed transmission schedule, ALOHA with priority ACK’s, and CSMA with priority ACK’s analytically and by simulation.

Queue-Sharing Multiple Access (QSMA) is introduced and analyzed. The new channel-access method consists of establishing and maintaining a distributed transmission queue among nodes sharing a common channel and results in a sequence of queue cycles, with each cycle having one or multiple queue turns with collision-free transmissions from nodes that have joined the transmission queue, followed by a joining period for the current cycle. Nodes can take advantage of carrier sensing to improve the efficiency with which nodes join and use the shared transmission queue. The throughput of ALOHA with priority ACK's, CSMA with priority ACK's, CSMA/CD with priority ACK's, TDMA with a fixed schedule, and QSMA with and without carrier sensing is compared analytically and by simulation in ns-3. The results show that QSMA is more efficient than TDMA with the simplicity of CSMA or ALOHA.