SCTP Programmer's Guide

Table 1-2 Comparison Between SCTP, TCP, and UDP (continued)

UDPTCPSCTPFeature

nonoyesMulti-stream support

yesnoyesUnordered data delivery

nonoyes

Security cookie against SYN flood attack

yesBuilt-in heartbeat (reachability check)

1 In UDP, a node can communicate with another node without going through a setup procedure, or

without changing any state information. However, each UDP packet contains the required state

information to form a connection, so that an ongoing state need not be maintained at each endpoint.

2 TCP does not preserve any message boundaries. It treats all the data passed from its upper layer as a

formatless stream of data bytes. However, because TCP transfers data in sequence of bytes, it can

automatically resize all the data into new TCP segments that are suitable for the Path MTU, before

transmitting them.

TCP implements a keep-alive mechanism, which is similar to the SCTP HEARTBEAT chunk. In TCP,

however, the keep-alive interval is, by default, set to two hours for state cleanup. In SCTP, the HEARTBEAT

chunk is used to facilitate fast failover.

This section addresses the following topics:

• “Multihoming” (page 28)

• “Multistreaming” (page 30)

• “Conservation of Data Boundaries” (page 31)

• “SCTP Graceful Shutdown Feature” (page 31)

• “SCTP Support for IPv4 and IPv6 Addresses” (page 32)

• “SCTP Data Exchange Features” (page 32)

• “Support for Dynamic Address Reconfiguration ” (page 33)

• “Reporting Packet Drops to an Endpoint” (page 33)

• “Support for ECN-Nonces in SCTP” (page 34)

• “SCTP Support for Partially Reliable Data Transmission” (page 35)

Multihoming

Multihoming is the ability of a single SCTP endpoint to contain multiple interfaces with

different IP addresses. In a single-homed connection, an endpoint contains only one

network interface and one IP address.

Figure 1-5 illustrates the single-homed connection in TCP.

28 Introduction