Better Networking with SCTP 233
5-0 writes to tell us that IBM DeveloperWorks has an interesting look at the key features of SCTP in the Linux 2.6 kernel and the ability to deliver multi-streaming. "SCTP is a reliable, general-purpose transport layer protocol for use on IP networks. While the protocol was originally designed for telephony signaling, SCTP provided an added bonus -- it solved some of the limitations of TCP while borrowing beneficial features of UDP. SCTP provides features for high availability, increased reliability, and improved security for socket initiation."
How long... (Score:2, Interesting)
Re:How long... (Score:5, Funny)
Easy that: as long as it took IPv6 to be adopted into the mainstream.
Re:How long... (Score:5, Informative)
Easy that: as long as it took IPv6 to be adopted into the mainstream.
Probably not that long. The problem with IPv6 is that too many entities are involved in a successful v6 deployment and too many changes have to happen at different levels.
OTOH, SCTP requires only a client and a server that want to use it.
Re:How long... (Score:5, Insightful)
And no overzealous firewalls on the way.
Re:How long... (Score:2)
And no overzealous firewalls on the way.
Compared to your chances of convincing an ISP to upgrade their routers and buy a prefix from ARIN, getting the firewall fixed is child's play even if the admin wears a huge tinfoil napolean hat and hides behind 'the commitee'
Re:How long... (Score:2)
I don't even dream about IPv6 support upstream -- the place where 192.88.99.1 gets routed to is... Switzerland (and I'm in Poland). Fortunately, at least prot 41 is not blocked.
While not terribly clueful about networking myself, I'm the guy who gets called by two of four local ISPs when they want any non-trivial changes to their firewalls -- so, I at least made them provide what IPv6 could be done, and I'm making sure the firewall
Re:How long... (Score:2)
That sounds like a pretty bad situation, but I'll still bet you could get SCTP/IP easier that IPv6 since v6 would require them to actually spend money and perhaps replace old routers. SCTP/IP requires only that they don't block it. It may even be that they DON'T block it since they probably haven't even thought about it. To a router, it's just an IP packet with an unusual protocol number.
I don't even dream about IPv6 support upstream -- the place where 192.88.99.1 gets routed to is... Switzerland (and I'
Overzealous security admins (Score:2)
What sucks is when some pompous asshat says "no, I can't provide you with a mechanism to accept incoming connections" or "no, you can't open an outgoing ssh connection".
Re:Overzealous security admins (Score:2, Insightful)
What sucks is when some pompous asshat says "no, I can't provide you with a mechanism to accept incoming connections" or "no, you can't open an outgoing ssh connection".
I feel your pain, however I've found that it makes sense use a simple formula when evaluating an end user request to allow XYZ traffic to traverse a firewall(s) on my organizations network, 1. Is there a business need for it or is it just a user saying "oh this would
No, but if you were an ISP... (Score:3, Insightful)
However if you were an ISP, tasked assumedly with providing connectivity to your customers, and did something similar, then yes, you would be, in my opinion. And there are a fair number of really crummy ISPs who, for one specious reason or another, block various ports and protocols.
And perhaps most unfortunately of all, it's quite common for these ISPs to have regional broadband monopolies, so that a c
Re:Overzealous security admins (Score:2)
Okay, I'll bite -- why? (I'll assume you aren't just being tautological and defining any non-buggy multithreaded program as "trivial"!)
Multithreaded code (Score:2)
No, it's not a tautological statement. And, actually, it's probably too strong (120 characters isn't much to say something in). It's a statement about engineering, not about computer science. Futhermore, I was thinking of systems without "hard" priority levels -- RTOSes have legitimate reasons for use of hard priority level threading. However, this is not the case for al
Re:Multithreaded code (Score:3, Interesting)
Multithreading should be treated rather like rabid dogs -- something to be avoided if at all possible.
A wonderful post. I usually say it a little more concisely: "can you draw me the complete state machine? no? then you don't know what your code's doing."
Re:How long... (Score:2)
The problem with IP6 is that it isn't backwards compatible with IPv4.
IPv6 will *never* happen.
http://cr.yp.to/djbdns/ipv6mess.html [cr.yp.to]
Re:How long... (Score:2)
Re:How long... (Score:2)
Comment removed (Score:5, Informative)
Re: (Score:3, Interesting)
Unfortunately (Score:2)
Multicast would rock for a P2P distribution system, even "explicit multicast" which has a rather low limit on the number of destinations, as opposed to IP multicast which has no limit on the number of destinations but presents a nightmare for backbon
Re:How long... (Score:5, Interesting)
How long do you think it will be before this is adopted into the mainstream?
Probably never main stream. Maybe for some telco types in niche applications... but it is too easy for 99% of the world to just open 2 sockets if you want 2 streams, or rpc's and threads... both of which are well supported and seasoned. Sctp is new, new bugs, not supported everywhere and as a result will go not go far.
One might argue it is supposed to be more secure, I argue it is not. If it was it would be tied to kerberos and ipsec and use AES at the transport layer.
Sctp has only one advantage, and this too could be done using TCP or UDP with not too much effort. That is you can open one socket and have mutiple streams inside, reducing the socket count on servers, a problem if you are routing more than 48000 calls or so. But yor could also do this with "TCP connecting pooling", a common way around this issue.
But like ATM, it is the telco business push. ATM anyone?
Sctp to me looks like a problem looking for a home for 99% of us. But at least an informative post so when I see the compile option I will turn it off.
Re:How long... (Score:2, Informative)
Nope. I worked on SCTP implementation in year 2000.... Nortel had it in 1999.
zm
Re:How long... (Score:5, Interesting)
Nope. I worked on SCTP implementation in year 2000.... Nortel had it in 1999.
New as in it is just making it into some kernels. And it most of us have never seen an application use it. And it may be years before we do. However, as stated it exists in a niche telco market.
Nortel (used to work there) and the industry still has the "central office" mentality. Nortel had one thing right, VoIP is the future. What the telco business as a whole has wrong is how this will be done.
In the future there will no need for a central office, all calls will NOT route through central servers and thus negate a heavy need for sctp altogether! sctp is like a T1-T2-Txxx to sockets, allowing n channels of calls through one IP connection. If VoIP (not strictly defined) goes point to point direct there is no need for a central office. End user devices only need 1 to 4 channels. (Audio/Video/Control/MP3 Movies).
What will happen is someone like Linksys (or a Chinese company) will get enough momentum to produce a $99 device you hook to your internet, some LDAP server out there will be your directory and call routing will go direct device to device over TCP/IP. The MOBILE protocol has a better chance of surpasing SCTP as being in common use. You might even run call conferencing right off your own device.
Central office technology has seen it's peek hayday. SS7, BSSMAP, ISDN, SONET and others are far too complex, expensive, patented and cumbersome - and will be religated to legacy wireline only. SCTP might be used in this niche area to concentrator like a RLCM to wireline services. Hardly end user equipment.
The Internet is slowly eatting the telco business alive. As the traditional telco business market is evaporating.
Wireline needs to quite the bickering, quite tripping on DCLEC cables and get decent inexpensive DSL services or they can say good-bye to their business. DSL is the only hope for the wireline side of the telco business and most are screwing it up big time.
Cisco, if they keep innovation going high are going to put Nortel out of business. Central offices are being replaced with Network Access Point (NAP) and Cisco is king. Nortel might be best to spend their efforts on making the biggest, fastest, cheapest internet router possible. A DMS10000, 10000 as it can take 10000 IP based fibers.
BTW, I loved working for Nortel, but left as I was a grossly underpaid Canadian and could see Stern was going to wreck the company.
Re:How long... (Score:2)
Not really. Its changing, most all of the backbone internet providers are telco people: Sprint, AT&T, MCI, Verizon. At my house, my telephone comes from my cable TV and internet provider. Many companies do this: Time-Warner cable, Comcast, and Cox.
I would say the telco business is alive and well.
Re:How long... (Score:2)
Re:How long... (Score:2)
Oh, so anything new goes nowhere. I can see your point, we are still trying to make those things as fire and the well mainstream...
Re:How long... (Score:2)
Goodbye TCP? (Score:3, Insightful)
Really?
Re:Goodbye TCP? (Score:4, Insightful)
Re:Goodbye TCP? (Score:2)
Re:Goodbye TCP? (Score:2)
not susceptible to SYN floods like TCP
Init and cookie floods instead, the basic problem still exists.
Re:Goodbye TCP? (Score:2, Informative)
Re:INIT floods (Score:5, Insightful)
Flooding using the flooder's true address will still work, but it is trivial to block. Sure, having 100000 zombies flood a single destination will put quite a burden and will force the floodee to maintain a huge list of banned addresses, but, a single hash table on the router will alleviate anything except for bandwidth wasted.
This is same as a full TCP connect() flood.
There is a TCP hack named "syn cookies", but this doesn't work very well as TCP wasn't designed to be resistant to SYN floods.
Re:INIT floods (Score:5, Informative)
Re:INIT floods (Score:2)
The server still has to compute and store the cookie (caveat: I have no idea how computation / storage intensive the cookie is; I'm mostly speaking theoretically here). So, what happens if I forge INIT blocks from 10 IP addresses? 100? 1000? If this raises the bar of forged INITs required to DOS, great, but it doesn't seem right to say it's immune from the analogous attack to the SYN flood (ie, in either case you can consume server resources while hiding your true IP address). It's just that now the questio
Re:INIT floods (Score:2)
That means that just like when the server is using SYN cookies with TCP, an attacker would have to fully open a connection/association to attempt a DOS attack. An invalid
Re:INIT floods (Score:2)
And I assume the cookie can be reconstructed based on the remote IP and the known key? I guess that makes sense, so any flood attack would have to compromise the key sequence. Could be an interesting attack to work on.
Re:INIT floods (Score:5, Insightful)
SCTP protects against this type of attack through a four-way handshake and the introduction of a cookie. In SCTP, a client initiates a connection with an INIT packet. The server responds with an INIT-ACK, which includes the cookie (a unique context identifying this proposed connection). The client then responds with a COOKIE-ECHO, which contains the cookie sent by the server. At this point, the server allocates the resource for the connection and acknowledges this by sending a COOKIE-ACK to the client.
Funny how things suddenly makes sense when you read the entire paragraph.
Re:INIT floods (Score:5, Informative)
In fact, that's pretty close to how it's done according to SCTP for beginners [uni-essen.de]
Re:Goodbye TCP? (Score:2)
Dude, FTP is an application-level protocol(runs on top of 2 TCP connections).
multihoming? (Score:2, Interesting)
Re:multihoming? (Score:2, Redundant)
Re:multihoming? (Score:5, Informative)
Heartbeats are optional. Some real-time applications probably want to use heartbeats every 10 seconds, while other can disable them completely.
The multihoming has nothing to do with routing table size. The multihoming feature is used for providing better connectivity.
Imagine your laptop with WiFi. If the application (say, FTP download) used SCTP instead of TCP then the download would not break when your laptop moves from one access point to another and switches ip-address. SCTP survives that.
Re:multihoming? (Score:2)
This only works when all potential ip-addresses of your laptop are known at the start of connection (example: one cabled IP address, and one (fixed) Wifi address).
Indeed, list of addresses is included in the init chunk, and not updated later.
In the case of "roaming" where you get a different, dynam
Re:multihoming? (Score:5, Informative)
This is an transport layer, not a network layer. It is only necessary in endpoints, such as clients and servers, and it might be a good thing if firewalls understood it. But the routers don't interpret it, so there won't be any change on backbones, except a slight increase in traffic with a few more keep-alive packets.
Re:multihoming? (Score:2)
Its an unfortunate re-use of the same term.
WOW! (Score:4, Funny)
Services file? (Score:2)
Please add the following to your /etc/services:
tallmatthew 25/sctp
SCTP vs TCP benchmarks (Score:5, Informative)
http://www.altoriopreto.com.br/mestrado/index_en.
Re:SCTP vs TCP benchmarks (Score:2, Interesting)
The exception being the HTTP tests, where I guess they used only one tcp connection to the server with no keepalive (something that no web browser would do in the real world, most opening 2 or 4 tcp connections with keepalive).
I can't see a real advantage of multi-stream SCTP over multiple TCP connections
Re:SCTP vs TCP benchmarks (Score:2, Interesting)
Good question
Perhaps this provides a bit of insight: From the article:
"Multi-streaming is an important feature of SCTP, especially when you consider some of the control and data issues in protocol design. In TCP, control and data typically share the same connection, which can be problematic because control packets can be delayed behind data packets. If control and data were spli
Re:SCTP vs TCP benchmarks (Score:2)
The why is far ore interresting. Is this a implementation that is still subtoptimal, or is this because features will cost latacey by default. (i see a 4 way handshake over a 3 way handshake will cost you a little bit more latnecy to start with)
I can't see a real advantage of multi-stream SCTP over multiple TCP connections
Managememnet int the STCP protocol instead of doing that manually? Specailly if quality of service is involved? YOu can program that all man
Re:SCTP vs TCP benchmarks (Score:5, Funny)
What would you like it to do, magically go faster than the bandwidth you have?
Re:SCTP vs TCP benchmarks (Score:2, Insightful)
I think the point is to use what you have more effeciently, if real "bandwidth" is measured as the transfer rate of actual payload from point A to point B, then using it more effeciently (less overhead) does actually increase "bandwidth", not magic but it does allow me to go "faster" than I can without utilizing those more effecient technique(s).
Re:SCTP vs TCP benchmarks (Score:2)
Low message delivery latency (Score:2, Informative)
The main advantage of using SCTP over multiple TCP connections is connection establishment time as well as server overhead. You can create an association with hundreds of streams in the roughly the same time as a single TCP connection, with little or no overhead for unused streams. Then when you want to initiate a new non-blocking transaction you can
Benchmarks measure LKSCTP not SCTP (Score:2, Interesting)
See http://sctp.fh-muenster.de/Performance/index.html [fh-muenster.de]
TAO/ACE Orb SCTP Benchmarks (Score:2)
http://www.atl.external.lmco.com/projects/QoS/docu ments/DOA2003_97_Thaker.pdf [lmco.com]
Seems the funding for the TAO SCIOP implmementation came from the US Navy:
http://www.omg.org/news/meetings/workshops/RT_2003 _Manual/Presentations/5-4_Thaker_etal.pdf [omg.org]
FreeBSD, Darwin (Score:5, Informative)
Re:Fyi Darwin is dead (Score:2)
Re:Fyi Darwin is dead (Score:2)
read the RFC (Score:4, Insightful)
I will grant SCTP does some neet stuff, the best is that it allows independent non-mutually-blocking streams over one connection. It also has state cookies, yum.
SCTP tries to be all things to all people in one protocol. It reads as though they just decided the whole layered protocol thing was overrated and shoved every new feature into this one layer.
Kernel space name resolution not required (Score:5, Informative)
State cookies are not stored on the server at all, but rather are echoed from the client back to the server as a effective means of SYN flood style DoS attack prevention.
SCTP (properly implemented) is radically superior to TCP for a large class of applications, basically anything that needs low latency reliable message exchange. The lack of message boundary information in TCP causes considerable pain for implementers of upper layer protocols - notably RDMA/RDDP and iSCSI. The running solution for efficient hardware implementation of RDMA and iSCSI over TCP involves *inserting* markers every 512 bytes or so in the middle of a data stream so that the receiver can re-synchronize it efficiently.
The primary SCTP RFC is RFC 2960 for those who are wondering.
Re:read the RFC (Score:2, Interesting)
I couldn't disagree more. SCTP moves a lot of things that should be done in the transport layer there, instead of making applications re-implement heartbeats and failover and message boundaries and so forth for the 1000th time.
How this compares WRT DCCP? (Score:4, Interesting)
The wikipedia assumes they share some properties, but it's SCTP a better DCCP, or what?
Re:How this compares WRT DCCP? (Score:4, Informative)
Other possible future TCPs (Score:5, Informative)
TCP Evaluation Discussion [hamilton.ie]
Interesting plots too [hamilton.ie]
The end result is that TCP is not particularly suited to high-speed networks.
Good news and bad news (Score:2)
Re:Good news and bad news (Score:2)
4-way handshake (Score:2, Interesting)
Now, if the COOKIE-ACKs required some signficiant processing (like encryption with a public key) then I could understand how this would re
Re:4-way handshake (Score:3, Insightful)
Does this matter with TCP/IP offload and iWarp? (Score:4, Informative)
I used to work on InfiniBand where the reliability/congestion detection protocol (Reliable Connected and Link Level flow control in IB terms) are in hardware. This scales to 20 Gbit connections between hosts quite well. Other examples of hardware protocols include myrinet (invented by myricom) and qsnet (from quadrics) and scalable coherent interface current pushed by Dolphin Interconnect. All of these folks struggle to compete with good old TCP/IP over ethernet. Except for the parts of the HPC world, TCP/IP over ethernet wins. In the storage landscape, Fibre Channel, SAS, and SATA seem to be holding out but iSCSI sure is trying.
The performance issue is real though and very few systems can saturate a 10 Gbit TCP/IP etnernet link without massive host CPU overhead. One solution floating around is that instead of trying to make new protocols to replace TCP, we should imitate the competition and put hard work in hardware. TCP/IP offload NICs (TOE) are becoming increasingly more popular. With RDMA technology layered on top of it you get iWARP. For storage you get iSER (ironically from an IB company!). This technology is being adopted by both the MS and Linux camps so it seems to have a good shot. In fact, many of the interfaces used by IB work about as well over iWARP cards. Things like Message Passing Interface, Direct Access Provider Library, Sockets Direct Protocol (SDP), and iSER do not know the difference between iWARP and IB or anyone else.
Software can just post a full size message and it gets sent out the wire without copying, segmentation, timers, resends, or other CPU hogs. This kind of stuff really helps with large messages. With SDP, apps can be made to take advantage of it without changes to the application. MS is also providing a standard way for just TOE NICs without RDMA abilities to work with the OS. Linux doesn't seem to have a standardized way for TCP/IP to be offloaded entirely but is supporting RDMA and SDP.
The things SCTP seems to offer is more explicit understanding of the difference between failure and congestion and multi-home support. This could make load balancing over multiple paths between hosts pretty interesting. The problem I see is that is that it is competing with the established TCP that now has many of its warts fixed with hardware offload. SCTP will still have the issue of a CPU handling segmentation/reassembly, massive amounts of interrupts, timer/retry overhead, etc. It also seems to have a higher overhead for connection establishment (although that is mitigated by being able to send data during the end phases). Is this a solution looking for a real problem? Pehaps not. Does this really have a chance of being taken up? I am not too confident.
-Ack
Especially on the WAN, yes (Score:3, Informative)
SCTP is a more efficient RDMA/iWARP transport than TCP, but the differential advantage of SCTP over TCP is much lower in a LAN environment due to the low RTTs, so RDDP/TCP dominates so far despite the bizarre marker insertion scheme (MPA). Same goes
Re:Especially on the WAN, yes (Score:2)
Ok, that makes more sense. IB and other hardware based reliability systems all have problems with long distances. There are folks working on IB WAN though including the U.S. Naval Research Laboratory [pennnet.com]. Check out Obsidian Research [obsidianresearch.com].
"The interrupt is
Re:Does this matter with TCP/IP offload and iWarp? (Score:2)
Only the win-modems/NICs (aka the cheap stuff) forced the CPU to handle all the network activity.
Or am I missing something?
Re:Does this matter with TCP/IP offload and iWarp? (Score:2)
Re:Does this matter with TCP/IP offload and iWarp? (Score:2)
Re:Does this matter with TCP/IP offload and iWarp? (Score:2)
Err, no. TSO (TCP Segmentation Offload -- DMA IO for the network) has been adopted by the Linux people, TOE (TCP Offload Engine -- half the TCP stack is now in hardware) has been completely rejected [lwn.net] by the Linux people, multiple times ... and has basically zero chance of ever happening.
The good thing, is that it doesn't help ... so no
Re:Does this matter with TCP/IP offload and iWarp? (Score:3, Insightful)
-Ack
Linux support for TOE (Score:3, Informative)
This is a bit of an end run around the Linux kernel bridging, routing, and filtering layers, which is the primary reason why support for it won't get merged in
Interesting. Not a bad idea (Score:5, Informative)
The first attempt in the IP world to add a protocol of this type was Reliable Data Protocol, in 1984. (See RFC 908 [faqs.org]). But that never went anywhere. Since then, nobody has really addressed this. There was ISO TP4, but that didn't go anywhere either, althoug it was fully supported in Windows NT.
SCTP has reasonable congestion behavior, like TCP, so it's an improvement over UDP-based protocols in that regard. Moving some UDP-based protocols to SCTP could be a step up. That's where it could be most useful. It might make sense to put remote procedure call type protocols that now use UDP onto SCTP. If a protocol has to do retransmission, it's better to do it at the transport layer than at the application layer.
The "multihoming" thing seems badly placed, because that's not properly a transport layer function. But I haven't really looked at that.
John Nagle
Re:Interesting. Not a bad idea (Score:2)
It would have been nice if SCTP would have been widely available when we were designing prot
Sounds similar to TIPC (Score:3, Informative)
It also has the concept of priority in it, so that messages may be prioritized.
Unlike SCTP, however, it does not run on top of IP but is its own protocol that runs directly over the wire, which means that it cannot be routed across an IP network. It is great as an internal embedded messaging protocol, but not as useful when a network is involved.
TIPC is also not connection oriented. There is no connection setup required to send messages much like UDP.
-Aaron
SCTP in need of a working shim (Score:3, Interesting)
So I asked - why not have an API for translating TCP calls into SCTP? He told me that this is called a "shim" and that one already exists. He also said the primary area of interest regarding the shim was getting the shim working on windows and deployed by default with windows. That would significantly reduce the gap.
TCP - SCTP shim requirements (Score:2, Interesting)
Second, trying SCTP first and then falling back to TCP later causes considerable delay. To fix that problem the shim would need to insert itself in the name resolution process (getnameinfo) so that it could intelligently decide which protocol to try first. Of course name servers would have to carry SRV extension records to indicate th
Re:TCP - SCTP shim requirements (Score:2)
congestion avoidance? (Score:2)
SCTP uses AIMD congestion control (Score:2, Informative)
Of course given the additional message boundary information available in SCTP, further improvements could be made.
Gives new meaning to "blowing chunks" (Score:2)
Chunks
Each SCTP packet consists, in addition to the common header, of chunks. Each chunk has a common format but the contents can vary. One chunk is display in the diagram to the right with the green background.
Chunk type
An 8-bit value predefined by the IETF to identify the contents of the chunk value field.
Chunk flags
Eight flag bits whose definition vary with the chunk type. The default value is zero.
Chunk length
Protocols that can benefit from SCTP (Score:5, Informative)
Some of the protocols that could benefit from SCTP include:
kitchen sink (Score:3, Insightful)
For example, manually opening multiple connections through different interfaces and then having the SCTP implementation figure out which one to send through is nonsense; if the system has multiple routes to the Internet, then that can be taken care of at the IP level.
Similarly, preservation of write boundaries is a useless gimmick that is rarely needed, and when it is needed, can be easily implemented in user code.
The four-way handshake during setup is possibly useful, but you can trivially get the same with TCP in a backwards compatible fashion if you configure your kernel to protect against SYN spoofing.
Altogether, I'm not quite sure what problem SCTP is supposed to solve. SCTP has made its way into some other standards, so it will probably be unavoidable, but it's not a well-designed protocol in my opinion.
Re:kitchen sink (Score:4, Interesting)
What's useless to one application is useful to another. Most of the features can be turned on and off, so the application developer can pick what's suitable for their use.
For example, manually opening multiple connections through different interfaces and then having the SCTP implementation figure out which one to send through is nonsense; if the system has multiple routes to the Internet, then that can be taken care of at the IP level.
This is one thing that I almost agree with you on - multihoming should probably be done at the IP level. But that requires that intermediate routers be modified to introduce the required functionality and we have already seen that many ISPs have no interest in adjusting their infrastructure to support new technologies (multicast, IPv6, etc). SCTP's multihoming support has the advantage that only the end points of the connection need to care, to the rest of the network it's just plain old IPv4.
Similarly, preservation of write boundaries is a useless gimmick that is rarely needed, and when it is needed, can be easily implemented in user code.
I'm not sure why you think this is a "useless gimmick". Very few applications want a byte stream - almost everything works on the datagram level. Think about HTTP - you send the server a bunch of headers (these are separate datagrams), the server returns a bunch of headers (again, separate datagrams) and the actual object data (one massive datagram). At the moment this is done over a byte stream and in order to maintain the boundaries between the datagrams you have to delimit them at the sending end and then parse them at the receiving end. With almost every application wanting to send multiple datagrams instead of a byte stream isn't it better to have this handled at the protocol level rather than reimplementing it for every application? Almost the only things which benefit from byte streams rather than datagram streams are interactive stuff like telnet and SSH (even SSH would benefit from SCTP when you're multiplexing multiple tunnels)
The four-way handshake during setup is possibly useful, but you can trivially get the same with TCP in a backwards compatible fashion if you configure your kernel to protect against SYN spoofing.
TCP SYN cookies are weak in comparison to the SCTP 4-way handshake.
Altogether, I'm not quite sure what problem SCTP is supposed to solve. SCTP has made its way into some other standards, so it will probably be unavoidable, but it's not a well-designed protocol in my opinion.
SCTP was originally designed for telephony applications (it is used to transport SIGTRAN traffic and can also be used to transport SIP). It is designed to combine the benefits of TCP (reliable ordered delivery with congestion control) with the benefits of UDP (preservation of message boundaries and unordered delivery). But while designing a new protocol it was worthwhile addressing other problems that have shown up with TCP and UDP. I would hazard a guess that the _only_ reason TCP is so widely used is because it's the only widely available transport that provides congestion control and reliable ordered delivery - most applications are _not_ suited to communicating through byte streams and many do not even require the data to arrive in order. If SCTP is widely available as an alternative protocol I can see it being used for new applications purely because the preservation of message boundaries removes the need for a chunk of parsing code.
Re:What's not said (Score:3, Informative)
Disclaimer: I'm using SCTP in my job for several years now.
Linux is a popular research platform (Score:3, Interesting)
Linux is a very popular platform for researchers to try out new kernel ideas in a real-world system, like networking protocol ideas. This is for a number of reasons (it's well-written, it's easy to hack on, it's open source and doesn't have any weird restrictions, it's free, it's already popular among CS folk, etc.
I'm not familiar with the particulars of SCTP, but just the fact that this is available under Linux (and perhaps that some (all?)) distros make it available by d
Re:Credit where due (Score:3, Informative)
In other words, it started out in the hands of AT&T, Bell Labs, Northern Telecom, Alcatel, et. al.
Utterly incorrect.
If you had only taken ten seconds to check wikipedia's sctp page [wikipedia.org] you would have found it was developed by the Internet Engineering Taskforce's SIGNTRAN [wikipedia.org] working group.
The IETF is an open, all-volunteer standards organization and couldn't be further in spirit from the monopolies you mention.
Give credit where it is due ind
Re:Credit where due (Score:2)
It's a matter of semantics. From the wiki you mention:
In other words the engineers on the telco's payroll's did the work under the auspices of a standards body instead of eacy vendor creating their own incompatible mess.
Truly the behavior of monopolists, daring to work together!
Re:Cool thing (Score:2, Insightful)
What for? Could you give a specific example of an application where such a protocol would be needed? (That is where using TCP or UDP would require a severe overhead in the application layer.)
If you have always wanted such a protocol, you certainly must have had a specific use in mind.
Re: (Score:2)
Re:Linux to Linux (Score:2)
Re:Linux to Linux (Score:5, Informative)
But yes all my friends use windows!
So will such features help Desktop Linux?
Short answer: It might "help Desktop Linux" in general, but it will fix zero interoperability issues and it will do nothing to the problems you listed.
Long answer: You need to learn a few things about network protocols, my friend. Even if SCTP, TCP or UDP had anything to do with your problems, SCTP is not implemented on Windows. Most if not all of the programs you're using use TCP or UDP, and the issues of compatibility you're experiencing have nothing to do with these protocols. The programs you mention have their own protocols that run over TCP and UDP. Seriously, go and learn how to program BSD sockets [softlab.ntua.gr] and you'll understand where TCP and UDP are in the network protocol heirarchy. Once you've done that, maybe you could help out projects like Kopete and Gaim to fix your problems.
YAGNI !!! (Score:2)