A Framework for Qualitative Communications Using Big Packet Protocol 2 nd Workshop on Networking for Emerging Applications and Technologies (NEAT 2019) 19 th August 2019 Richard Li 1 , Kiran Makhijani 1 , Hamed Yousefi 1 , Cedric Westphal 1,2 , Lijun Dong 1 , Tim Wauters 3 , Filip De Turck 3 Futurewei Technologies 1 , University of California, Santa Cruz 2 IDLab, Ghent University ś imec 3
Agenda • Motivation & Concept • Traditional means of dealing with retransmission. • Qualitative Service • New Packetization • Qualitative Service Techniques • Qualitative Service Framework • Generic Packet Wash Operation • Adaptive Rate Control • In-Packet Network Coding • In-Network Qualitative Packet Processing • BPP Based Implementation Strategy Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 2
Agenda • Motivation & Concept • Traditional means of dealing with retransmission. • Qualitative Service • New Packetization • Qualitative Service Techniques • Qualitative Service Framework • Generic PacketWash Operation • Adaptive Rate Control • In-Packet Network Coding • In-Network Qualitative Packet Processing • BPP Based Implementation Strategy Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 3
Packet as Fundamental Unit • Information Integrity is verified at packet level • Traversed :- complete forwarding information (addressing) • Treated :- Forwarded as an atomic entity ( fragmentation: leads to new pkt ). • Verified :- Checksum computation over entire packet • Consequences • Dropped :- In entirety by network elements 0 1 0 0 1 0 1 0 1 0 0 1 0 1 0 1 0 0 1 0 1 0 1 0 0 1 0 1 0 1 0 0 1 0 1 On the wire payload = Pkt tx Pkt intransit = Pkt rx sender Network nodes receiver Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 4
Cost of Retransmissions Due to Packet Dropping • When reliable transport layer protocol is used, packet drops result in the retransmission of the packet. Sender Receiver t 0 t 0 P 1 sent • Cost of re-transmissions t 1 t 1 RTO for P 1 • Wastes network resources t 2 Timeout or Dup ACKs (lost segment) • Reduces the overall throughput, t 2 • Unpredictable longer delays. Retransmit P 1 t 3 t 3 Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 5
Basic Idea – Packet as Logical Unit Bits by themselves have no meaning Application Semantics 0 0 .. 0 1 1 1 0 0 1 0 1 1 0 Old School (what information, how to use it) 0 1 .. 0 1 0 1 • Organize packets according to semantics. On the wire payload § Utilize application data semantics for a more predictable headers delivery of data even in adverse network conditions. • Each local unit (called chunk) is self-describing Chunk On the wire § Its significance in the context of information carried in the context chunks payload. § Operate on chunks not no the bit-stream. New Idea • Purpose: § Ability to perform finer granularity of Operations on Packets Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 6
Why Logical Units? drop P 1 traditional packet Egress Queue Qualitative packet trim Logical units within packets enable Trim excess N bytes selective drops as against full and used available queue buffer packet drop Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019
Qualitative Communication Service A packetization scheme that breaks down the payload into multiple chunks, each with a certain semantics or significance. The network nodes make decisions * to process chunks based on the current situation and the significance carried in the packet. Pkt’ Pkt Pkt’ Pkt sender Network nodes receiver Note*: Network does not understand semantics, only operate on the meta data, without any knowledge of information carried in chunks. Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 8
Question May be Raised • Can we simply reduce the packet size to the chunk size, and transmit each chunk as an independent packet? • Increased overhead of the protocol headers and underlying packet latency for the same amount user data. • Reduced bulk protocol throughput, and a greater number of packets to be processed by the network. Headers Chunk1 Chunk2 Chunk3 Chunk4 Chunk5 Headers Chunk1 Headers Chunk2 Headers Chunk3 Headers Chunk4 Headers Chunk5 Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 9
Agenda • Motivation & Concept • Traditional means of dealing with retransmission. • Qualitative Service • New Packetization • Qualitative Service Techniques • Qualitative Service Framework • Generic Packet Wash Operation • Adaptive Rate Control • In-Packet Network Coding • In-Network Qualitative Packet Processing • BPP Based Implementation Strategy Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 10
Qualitative Service Framework Application Qualitative Payload (chunks, priorities) Network: Hop by Hop Conditional PacketWash Transport Layer Receiver (congestion notification Sender protocols) (Qualitative Context and Action) Network Layer Transport: End to end qualitative congestion feedback Application Level Support : Transport Level Support : Network Level Support : § Only an application can tell § Sender should be informed of § Network layer needs a well- what can be treated Qualitative operations. formed meta-data to qualitatively and how to § The partial dropping of a packet conditionally do operations treat it. should be understood by sender as a § In-network Processing § Application feeds meta-data warning that some level of congestion to network layer. is occurring. Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 11
Generalized Packet Wash Operation PacketWash : Action that changes the Q-Entropy : describes the payload. rule to alter the payload. • Is a function through which • A chunk-dependent network nodes treat a qualitative packet; significance parameter • Has thresholds beyond which a understood by this function; packet cannot be further degraded (as it would become useless); Entropy Payload • Triggered on Network conditions ( ⍷ ) (P) or congestion. PW Q’ p Q p Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 12
Adaptive Rate Control • Packet Wash performs selective trimming of a payload from less to higher significant chunks. • Trimming of packets is a signal of congestion • This can be viewed as a form of Early Congestion Notification (ECN) coupled with an immediate reaction The receiver selectively acknowledges the received chunks, and not the packets - The sender can take action to reduce the sending rate to match the observed - throughput, so as to avoid further chunk drops Optimal control loop is for further study - Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 13
Transport Layer for Qualitative Services • After a trimming operation, the network may increase the priority/TOS of the packet • Occurs from the lowest priority first • For fairness: l To ensure the same flow is not trimmed twice before another flow is trimmed once • For performance: l To speed up the delivery of a packet that has already encountered congestion Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 14
In-Packet Network Coding • Network- coding granularity is reduced from packets to chunks. First group of data chunks ( k =5) • The data to be transmitted is segmented into groups of k chunks. In-Packet Network Coding Window • Create payloads by inserting network coded chunks. • The receiver needs k chunks (or degrees of freedom) to decode the chunks. • Qualitative communication services can Packet 2 with coded chunks Packet 1 with coded chunks be facilitated by utilizing the in-network ( h =3) packet wash on coded packets. Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 15
Benefits of In-Packet Network Coding • The sender can add some ratio of redundancy in the packet payloads. Packet 1 Packet 2 • The remainder of the payload can be cached Sender by the receiver and are useful for future decoding. Forwarding • When network congestion happens, the Node 1 Re-code with cached intermediate router does not need to decide Cache coded chunks from Packet 1 chunks locally which chunk to drop, it can randomly select Forwarding as many chunks as needed until the outgoing Node 2 bu ff er permits to contain the packet. Receiver • There is no need for priority in this context and not need to track which specific chunk has been lost. Decode the original chunks without retransmission Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 16
Side-Effects of Qualitative Packetization • Since Qualitative service is a new packetization scheme, Payload integrity must be preserved ( network never interprets user payload ) • While we do not propose a format of Qualitative packet: • Chunk Offset - Now each Chunk is an independent entity other than forwarding header. Relative offset from the start may be used to delineate chunks. • Encryption – over payload is not helpful in this scheme, it must be at chunk level • Checksum – similarly, checksum independence is necessary. Qualitative Services, 2nd ACM Sigcomm NEAT Workshop 19 August, 2019 17
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