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Roadmap
This page centralizes the list of projects being worked on, ideas for future projects, list of implemented projects, and projects and ideas that have failed due to some unknown reason at the time they were conceived.
The intent of this roadmap is to guide our community to better allocate our efforts. In addition, this roadmap should give newcomers an opportunity to understand where Linux XIA is, how our efforts are organized, and what you can do to help.
If you are looking for something to work on, and find this roadmap too rough, check out our Ideas list.
Depend on: reaching enough code maturity
Developer: Michel Machado
Status: started
Linux XIA is not yet mature enough for production, but we do think that broader exposure will help us to move forward faster, and get more in tune with the interested community. This project will figure out how we can submit our code upstream, do all required work, and, hopefully, go mainline.
Depends on: TCP-like transport
Developer: Alexander Breen
Status: started
Bringing iperf, nginx, and Firefox to XIA allows one to test and demo a lot of things.
Depends on: UDP- and TCP-like transports
Developer: Yuguang Li
Status: started
VLC and Live555 are client and server video applications. Their port to XIA will enhance our demos, and allow one to explore principals that can improve video transmissions. The importance of this effort comes from the large fraction of the total Internet traffic that is nowadays dedicated to video.
The following projects describe ideas we want implemented, but nobody is working on. We'll come back to them at an opportune time. If you choose to work on one of them, please announce it on our mailing list.
Depends on: LPM principal
Status: Not started
Providing inter- and intra-domain routing is fundamental to allow users to build testbeds comprised of more than a few machines. Retrofitting BGP/OSPF to XIA would provide XIA users with a "simple" way to build large XIA networks. Bird or Quagga are good starting points to avoid developing from scratch.
Status: Not started
Simplify the work that applications have to do to create XIP addresses.
Depends on: none
Status: Not started
These principals offer a gradual migration plan from IPv4 to pure XIA networks.
Besides the implementation of I4ID and X4ID principals, this project should document demos to be posted on this wiki.
The U4ID principal has proven to be a useful principal to promote interoperability between XIA and TCP/IP. The U6ID principal should be the analog of U4ID for IPv6 networks. The code of U6ID should follow the code of U4ID closely to keep general behavior, and simplify implementation.
Besides the implementation of the U6ID, this project should document a demo to be posted on this wiki.
Depends on: none
Status: Not started
The idea is to have a name resolution for XIA. A new resource record type is needed for XIP addresses.
Depends on: none
Status: Not started
Finding a way to reuse the implementation of TCP or SCTP present in the Linux kernel such that one of them can be a principal in Linux XIA. This would simplify porting applications, offer a reliable transport for XIA applications, and benefit XIA from all the long-accumulated experience that Linux's implementation of these protocols has.
Depends on: Ether principal
Status: Not started
A very simple version of NWP is implemented inside of HID's kernel module. Once Ether principal is implemented, NWP could be implemented in userland. A userland implementation of NWP would simplify the code, and lower the effort to bring out the potential of the protocol. For example:
- Identifying and removing unavailable hosts efficiently;
- Low convergence time of the neighbor tables;
- Levering instrinsic security to avoid cache poisoning;
- Taking advantage of Ethernet multicast to reduce broadcast frames;
- Supporting zero configuration in local networks.
The last item would eliminate the need for DHCP, and can be seem is just an extension of what NDP does in IPv6.
Once NWP is in userland, the current NWP in the kernel should be removed, and all communication with the kernel to maintain the neighbor table must go through Netlink.
Currently, HIDs are bound to a machine and thus available on all network interfaces, however, this makes testing forwarding harder, and limits network administrators' control on the topology of their networks. The solution is to scope HIDs to one or more network interfaces in a similar way to IPv6, in which an IPv6 is bound to a machine, but scoped to network interfaces. The new incarnation of NWP should scope HIDs.
Depends on: Userland NWP
Status: Not started
Once NWP is in userland and flesh out, the current HID principal will lose meaning, and should be deprecated.
Instead of dropping HID principal entirely, one should implement a new HID principal that simply redirects to Ether principal in order to keep compatibility with Click XIA.
Depends on: TCP-like transport
Status: Not started
Linux kernel does not include a full RSA implementation because its maintainers believe that all current demands can be properly handled in userland. This page holds some links about this issue. The current implementation only supports signature verification. Without RSA, implementing intrinsic security is daunting.
Depends on: None
Status: Not started
Having Linux XIA on Raspberry Pi would open the door to have Linux XIA on embedded solutions. For example, home and car networks. An idea to showcase this port is to send videos and pictures captured with a Pi camera using the Digital fountain.
Depends on: None
Status: Not started
Implementing the CID principal, the content principal, for Linux XIA. An interesting first version of this principal would be to reshape the TUX web server, a simple web server for static content implemented as a kernel module, as the CID principal. More on the TUX web server is available here, and a short description of how it accesses the file system here.
This first version of CID would have some challenges to overcome, most notably that there won't be a reliable transport to use. Given that we don't need HTTP compatibility, the HTTP header could become binary like in HTTP/2, and have fields to work without a reliable transport underneath it.
Instead of defining its XIDs as a simple hash of the content they represent, the CID principal could define its XIDs as being the root of a Merkle tree over the content they represent. This alternative approach allows a cheaper verification to take place when not all parts of a large content is available. The reliable transmission mechanism could potentially take advantage of the Merkle tree to operate as well.
Depends on: None
Status: Not started
The tool xip, Linux XIA's tool to manage the XIA stack, has been growing with each principal added to the stack, but its code hasn't been carefully designed to avoid duplicate code. In order to prepare xip for the future principals, the following improvements would help:
- Refactoring
xipto keep the code clean as the number of principals. Does it make sense to push the code for each principal into a dynamic object? Shouldn't there be an internal library to homogenize the code of each principal? - Dropping the current Route Netlink code in favor of adopting the library libmnl. The current Route Netlink code is borrowed from
iptool, and it does more than whatxipneeds. Library libmnl is simple, clean, and has been successufully used in net-eval. - Shouldn't
xipbe smart enough to load the kernel module of requested principals?
Depends on: None
Status: Not started
In order to keep XIA's DST table synchronized with the routing table, Linux XIA implements a routing dependency algorithm. We wrote this algorithm at a very early stage of the development, and didn't know all the relevant use cases back then. Our understanding of the importance of this algorithm has also improved, and now it'd be a good time to rewrite this algorithm to reflect all the current knowledge.
The current implementation limits the number of redirects to one due to the complexity related to managing locks for two or more levels of redirections. In practice this force principals to have a hard time to implement default routes since it would add at least one more redirecting level. Researching how locks are managed over trees and DAGs should help us to reach a solution that would remove this restriction.
An interesting use case that emerged during the development of XDP was the following: XDP principal needs to pre-route XIP addresses per sockets. While doing it, XDP may have to hold a set of DST entries for each address. If any of these DST entries becomes invalid, the whole address must be rerouted. The current code only watches for the last DST entry.
Another use cases not properly handled is the case in which a principal needs to fork a routing redirect, that is, the principal needs to return more than one XID to XIP. The canonical example of this case is the zFilter principal. The current implementation postpone the fork up to the forwarding call. This need is also found by other principals, for example, when a principals wants to load balance over a set of XIDs.
Finally, a use case that only became aparent while profiling the implementation with net-eval was the heavy anchors. A few anchors may become the root anchors of virtually all DST entries. The issue that emerges in this scenario is the lock contention to add dependencies to these heavy anchors.
The following projects explore less understood aspects of XIA. Their outcomes can lead to discoveries and publications, or painful failures. If you dare work on one of them, the general recommendation is as follows:
- Start researching the literature. Google scholar is a really good starting point. Read as many related papers as you can find. Write a "related work" page that summarizes the papers you read.
- If you decide to keep going, announce your project on our mailing list.
- Present the most relevant papers you found in our group meetings. Remember to include the link to your related-work page when you request meeting slots to present the papers. You may get good feedback and more references from our group, and someone may even join your effort.
Make the journey your destination. Research is in general rewarding, but it can also be painful. Do not give up on your project because you may not have the qualifications at beginning, or the challenges may seem daunting, or after the first failures. While persistence is going to be key to overcome the difficulties, keep your eyes open to opportunities that you may find during the project. This last point is well captured by Nobel prize-winning biochemist Albert Szent-Györgyi: "A discovery is said to be an accident meeting a prepared mind."
Depends on: lots of courage
Status: Not started
Denial of Service (DoS) can grow out of control and well threaten the Internet as we know it. A complete solution for this problem is not known yet. This project intends to explore the design space to figure out if one can create a set of principals that can be widely deployed, implement some form of robust communication between clients and servers, and impose a high cost to those executing DoSes. The solution may not allow communication between clients, for example.
If successful, this project could well be the reason people would take to embrace XIA in production.
Depends on: TCP-like transport
Status: Not started
If a congestion control solution could be implemented just above XIP and below all principals, it would automatically make everything congestion control aware. There are plenty of challenges here, TCP/IP offers no example, and there is little literature about this. TCP/IP, for example, does not enforce congestion control, which is left to protocol as a measure of good citizenship. Moreover, any congestion control protocol should be friendly to TCP's congestion control in order to avoid disrupting most of the Internet traffic.
This project seeks to compare, implement, and evaluate various information-centric networking models in Linux XIA.
Information-centric networking is a general approach for an Internet architecture that elevates content to be a first-class entity. It enables efficient and secure content transport through caching, chunking, closest-copy routing, replication, etc. ICN also provides better scalability in the face of an Internet that is increasingly focused on large-scale data distribution.
Linux XIA does not currently support ICN, but this approach has been modeled in XIA as the CID (content identifier) principal. The CID principal has been implemented in the XIA prototype in the Click Modular Router (with caching and chunking modules included) [2].
There are several prominent ICN projects ongoing in the United States and abroad. Content-Centric Networking (CCN) [3] and Named Data Networking (NDN) [4] are two closely-related projects that take the ICN general concept and apply a more specific architecture principles.
Other approaches from European groups, such as COMET [5], would simplify content access by acting as a content-wrapper over the current Internet, mapping content mechanisms (naming, addressing, resolution) to network resources over existing infrastructure. CONVERGENCE [6] proposes to establish a content-centric model based on a common container for all kinds of digital content, called a Versatile Digital Item (VDI). GreenICN [7] addresses how ICN networks and devices can operate in highly-scalable and energy-efficient ways, such as in disaster-aftermath or video-delivery environments. PURSUIT [8], NetInf [9], and various other projects take slightly different approaches as well.
Finally, there are significant economic considerations to take into account when designing a content-centric Internet. Two PhD dissertations [10] [11] have modeled the economic considerations and proposed protocol design for ICNs.
- "XIA: Efficient Support for Evolvable Internetworking." Han et al. NSDI '12.
- https://github.com/XIA-Project/xia-core/wiki/XIA-Prototype-Overview
- http://www.ccnx.org/
- http://named-data.net/
- http://www.comet-project.org/
- http://www.ict-convergence.eu/
- http://www.greenicn.org/
- www.fp7-pursuit.eu/
- http://www.netinf.org/
- "Modeling and Optimizing Content-Oriented Networking." Chong Wang, PhD Dissertation, Boston University, December 2012.
- "Economic Incentives in Content-Centric Networking: Implications for Protocol Design and Pubic Policy." Patrick Ayapong, PhD Dissertation, Carnegie Mellon University, May 2013.
- Develop a better understanding of current ICN designs and consider economic models of content. Compare and contrast the approaches and pick three diverse models to implement in Linux XIA.
- Design mappings for how to port the chosen approaches to Linux XIA principals. Think of ways in which these principals may be used or compose with other principals.
- Implement these principals in Linux XIA.
- Evaluate the ported ICN principals in terms of the ease with which they were ported, their performance, how well they address various environments and applications, etc.
- Apply the implemented ICN approaches to environments aligned with the FIA Next Phase, such as video delivery.
- What are the strengths and weaknesses of the various ICN approaches? Can they be evaluated along common performance metrics?
- Is Linux XIA an effective platform for experimentation and evaluation, as previously claimed? How easy (or difficult) are the ports -- does Linux XIA lower the deployment barrier?
- How do ICN approaches mesh with the evolvability model of XIA?
- How can Linux XIA compose different models of content in DAGs? What kinds of applications could benefit from these compositions? Could new applications be created?
- Control plane mechanisms (globally? Or per-principal?).
- Cryptographically-secure identifiers.
- Experience with various future Internet architecture designs and ICN principles.
- A content principal (or series of principals) in Linux XIA that would be useful to a broader array of users.
- An example of Linux XIA as a platform for evaluation of similar approaches, which is currently claimed but perhaps not yet supported.
- Further evidence of evolvability and interoperability of XIA, and more measurements of how easy/difficult it is to port architectures to Linux XIA.
- Research and applications that are relevant to video delivery environments, in line with the desired outcomes of the FIA NP grant.
- A paper that evaluates the architectural and performance features of porting ICN models to XIA, perhaps well-suited for a SIGCOMM ICN workshop or the 3rd ACM-ICN.
- May 1, 2015: research and comparison phase. If there are no interesting research angles to this project, it could be redirected or scrapped.
- June 1, 2015: port design phase completed, possibly reconsidering which models to port.
- August 1, 2015: port of at least one of the models -- perhaps the most useful one first (NDN?). If interest dwindles past this point, this architecture could at least be used for CIDs.
- November 1, 2015: port of the second model. Re-evaluate whether to port a third model, or to evaluate two ported models.
- January 1, 2016: port of the third model, or evaluation of ported architectures.
- March 1, 2016: evaluation of the ported architectures complete.
- June 1, 2016: application of results to various environments, such as video-delivery, disaster-recovery, etc.
Status: Done
The application will take advantage of zFilter principal to multicast videos, and erasure codes to make the transmission reliable. Read about the Digital fountain.
Depends on: None
Status: Done
Here is the list of implemented items necessary for the foundation of XIP:
- XIP routing tables. It was implemented with a sophisticated lock mechanism that supports concurrent writes, lockless reads, and on-demand expansion.
- Support for RTNetlink API. RTNetlink API allows one to write routing daemons in userland, and applications to manage the XIP stack. Notice that RTNetlink API is the same API daemons like Quagga (http://www.quagga.net/) use to manage IP's routing tables.
- Applications to manage configuration (package xiaconf). Package xiaconf is a analogue of iproute2 for XIA, that is, xiaconf is a collection of utilities for controlling an XIA stack.
- Principals as independent kernel modules. Not only does it make developing new principals easier, it also bounds the complexity of the whole code since all principals are independent.
- Support for LXC (http://lxc.sourceforge.net/). LXC is relevant for two reasons, it simplifies sophisticate testing/debugging, and is a cutting-edge virtualization mechanism supported in Linux that makes it important to push XIA for cloud providers/users. Although LXC is not trivial to understand, it turned out that supporting LXC took little coding effort and helped to organize the code.
- Forwarding API for principals with support for fast path (Linux DST subsystem) and positive dependency. Positive dependency is important to avoid flushing routing cache whenever an modification in the routing table is made; otherwise the performance could be even worse than slow path, and would produce traffic hiccups in busy routers.
Depends on: Foundation
Status: Done
HID principal integrates with XIP's routing table, application xip, and packet forwarding. HID also implements a very simple version of Neighbor Watch Protocol (NWP) that fills in a role similar to ARP's one in IPv4.
Depends on: Foundation
Status: Done
AD principal integrates with XIP's routing table, application xip, and packet forwarding.
Depends on: XIPNIC
Status: Done
XDP implements a UDP-like protocol, but it's header less. XDP doesn't add checksum, and since XIP doesn't support fragmentation, neither does XDP.
Depends on: Foundation and principals AD, HID, and XDP
Status: Done
XIP DST entries must be invalidated when they rely on the non-existence of either a principal (i.e. the principal isn't loaded into the kernel), or an XID of a known principal; a principal becomes known when it's loaded in the kernel. Negative dependency is essential in XIP because routing cache will end up making wrong decisions without it.
Depends on: UDP-like transport
Status: Done
The idea here is to have connection state, reliable delivery, flow control, and optional ordered delivery. We ported Serval to XIA; Serval offers all these features and more.
Status: Done
These principals allow Linux XIA to interoperate with IPv4 networks, and Click XIA's variation of U4ID.
Status: Done
It is multicast principal that does not keep state per multicast group, but router's neighbors.
XIP addresses are not going to be associated to network devices like IP addresses are. XIP addresses do not have the same semantic of an IP address. Even XIDs are not assigned to interfaces, for example, an HID is associated to a machine, not an interface.
This new protocol must support dynamic extensions in order to allow unforseen principals to use it for unforseen messages.
It turned out that to support evolution, each principal must implement its own messages when need, and that a principal dedicated to diagnosis is the way to fill the remaining gaps of not having an ICMP-like protocol.
Depends on: Foundation
Status: Not started
Raw sockets was thought as a way of first testing ideas for principals in userland. However, Implementing principals in userland is not on the roadmap anymore because it turned out that each principal makes use of different kernel APIs to work, and restricting userland principals to a set of kernel APIs would limit userland principals' scope. Moreover, Linux prototype has successfully been able to componentize principals as kernel modules.
All grants that have generously supported the development of Linux XIA are listed on our Funding page.