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Almost every company offers some kind of remote usage of accommodate employees working at home, business partners, or external tech support team. Remote access became very well liked partly due for the Remote Access Service RAS on Microsofts Windows NT. It allows remote clients to dial-in and connect and logon to network like they were relaxing in the office and locally connected. Nowadays the acronym RAS is employed to define various kinds of remote dial-in solutions.
PPP is todays preferred RAS protocol which is supported by just about every network system which is part in the TCP/IP suite. In addition to point-to-point dial-up connections over POTS and ISDN, PPP is usually used for router-to-router connections in WANs. PPP operates on the Data Link layer with the OSI model and includes two varieties of control protocols:
Link Control Protocol LCP - establishes, configures, maintains, and terminates the point-to-point connection.
Network Control Protocol NCP Provides an interface for a number of upper-layer Network protocols including IP, IPX, AppleTalk, and NetBEUI, and can be used to encapsulate the upper-layer protocols data and transfers it within the link put together by the LCP. Multiple protocols, like IP and IPX, are able to use the link simultaneously.
PPP supports several authentication protocols including MS-CHAP, EAP, the older Password Authentication Protocol PAP, plus the Challenge Handshake Authentication Protocol CHAP. After the remote client is authenticated, the PPP connection is reasonably insecure since the transmitted info is not encrypted. Several other protocols are around to encrypt the transmitted data and secure the authentication process. Examples of such protocols are PPTP and IPSec, that happen to be discussed at a later date in this chapter.
A very helpful extension to PPP is Multilink PPP, that allows multiple physical connections being combined within a logical connection. A typical illustration of this is bundling the 2 main B-channels in the ISDN BRI connection.
PPP could be the successor on the Serial Line Internet Protocol SLIP, an adult dial-up protocol, used primarily in UNIX environments and still backed up by some ISPs. Major differences with PPP are that SLIP lacks authentication, compression, and multilink capabilities.
As its name indicates, PPP over Ethernet PPPoE allows encapsulation of PPP packets in Ethernet frames. PPP is ideal for point-to-point connections instead of a shared broadcast medium like Ethernet. But when DSL, cable as well as other broadband connections became available, which that can provide use of multiple hosts over a shared Ethernet network, ISPs desired to maintain precisely the same functionality given by PPP to control, and charge for, individual client connections. PPPoE basically offers the functionality of PPP, for instance LCP, NCP, and its particular authentication methods, however for Ethernet. It allows multiple Ethernet hosts to find out a unique PPP session with all the provider via a bridging device like a cable modem.
The Remote Desktop Protocol RDP is utilized by handheld remote control software for example Microsoft s Remote Desktop to transfer mouse/keyboard input and screen output more than a TCP/IP connection. For example, the website owner can manage a server remotely, and never having to walk to your server room, and work using the server just as if she was soaking in front of it. Desktop support staff can solve client problems without going towards the user s office. This is obviously very convenient for both IT staff and users as it may save both time and effort. RDP can be used for Microsoft s Terminal Services, that allow clients to perform applications on the remote server. This allows some type of computer with a minimal configuration to own applications that could normally not operated with the computer as a result of hardware limitations. This concept is termed thin client and allows multiple users to work with different applications simultaneously, in their own individual private workspace about the terminal server. In addition to keyboard input, mouse input, and screen output, clients can make use of their local disks and printers from applications running around the remote server. RDP has been available since Windows, but RDP servers and industry is now made available for Linux along with other operating systems. RDP uses port 3389.
A Virtual Private Network VPN can be a private connection spanning a public network including the Internet. VPNs can help to save a company big money because they may use their Internet connection, as an alternative to expensive long-distance point-to-point connections for instance dial-up, ISDN, and leased lines, allowing remote networks and remote employees to connect to your corporate network. The first main sort of VPN can be a connection between two networks and is particularly known to be a site-to-site or LAN-to-LAN VPN. It is typically used by connecting branch offices of one particular organization or creating an extranet for business partners. When the VPN is established, a personal virtual point-to-point connection, known as the tunnel, is created above the Internet between two routers or firewalls. The clients and servers from the networks on both sides in the VPN connection are unaware on the VPN. The following network diagram shows a simple illustration of a site-to-site VPN. The green line depicts the virtual connection.
The second main sort of VPN, called remote access VPN, is very useful for remote and mobile users who require to access the business network. Whether they come in a hotel, for a business partner s office, or over a business trip to your other side in the planet, all that they need is an Internet connection along with a VPN client. The VPN client applications are installed within the client main system and establishes a tunnel to your corporate network following a connection using a local ISP is established. This style of VPN is called remote access VPN and is particularly depicted inside following network diagram. The remote access connection in the client to your Internet may be anything at a dial-up with a cable connection given that it supports PPP. The router inside following network diagram might be a firewall or even a VPN hardware appliance.
Tunneling identifies encapsulating a packet into another packet. There are at the least three sorts of protocols associated with a tunnel. The first will be the carrier protocol, for instance IP around the public Internet. The second may be the tunneling protocol, for instance PPTP, L2TP, and IPSec. The third could be the encapsulated protocol, like IP, IPX, NetBEUI and AppleTalk. The following three sections cover the tunneling protocols.
The Point to Point Tunneling Protocol PPTP is usually a tunneling protocol creat ed primarily by Microsoft. It can be an extension of PPP and encapsulates PPP packets to transfer them by using a tunnel spanning a public IP network. The encapsulated protocol might be IP at the same time, and also IPX, AppleTalk, as well as other protocols support ed by PPP. PPTP relies within the authentication protocols in PPP, including MS-CHAP, and relies using a protocol called Microsoft Point-to-Point Encryption MPPE to offer data encryption. PPTP itself isn't going to provide any actual security because it will not encrypt the encapsulated packets, it merely tunnels encapsulates them. PPTP operates on the Data-Link layer in the OSI-model and uses TCP port 1723.
The Layer 2 Tunneling Protocol L2TP is undoubtedly an IETF standard developed to replace PPTP. It could be the result of combining the technology of Microsoft s PPTP with Ciscos Layer 2 Forwarding L2F tunneling protocol. In addition to IP networks, L2TP supports tunneling through various other kinds of point-to-point networks including Frame Relay, X.25, and ATM. The encapsulated protocol could be IP, but IPX, AppleTalk, along with other protocols support ed by PPP while they are transmitted as IP packets. Just as with PPTP, L2TP won't actually encrypt data, nor will it authenticate individual messages. To overcome these shortcomings, L2TP is normally us ed in partnership with IPSec. This combination offers an additional layer of authentication and encryption for the reason that L2TP packets are encapsulated in IPSec packets for the Network layer. L2TP operates on the Data-Link layer in the OSI-model and uses UDP port 1701.
IPSec is often a popular and finish encryption framework for IP networks that can offer end-to-end security with the Network layer by using a selection of protocols and encryption techniques. IPSec is usually us ed in partnership with tunneling protocols for example L2TP to provide a higher level of the reassurance of VPNs. Besides VPNs, IPSec can also be used in LAN environments for client/server connections, router-to-router connections in WANs, and then for secure RAS connections. A primary benefit from IPSec is that it truly is transparent towards the user and is usually easily implemented since the majority modern os's and network devices support it natively.
IPSec can run by 50 percent different modes: Transport mode or Tunnel mode. In transport mode, the payload associated with an IP packet is protected. In tunnel mode, the payload plus the header are protected. If the original header is encrypted, a whole new header while using basic IP address facts are added on the encrypted packet, so routers and network devices can certainly still read the information they require in order to transport the packet. IPSec and its particular protocols use port 50, 51, and 500.
S-BGP uses repositories for distribution on this data. We initially described a model the place where a few replicated, loosely synchronized repositories were operated through the RIRs. Discussions with ISPs suggest a model where major ISPs and Internet exchanges operate repositories, and smaller ISPs and subscribers employ these repositories. In either model, each ISP periodically, one example is daily, uploads new/changed certificates, its current CRL, and AAs. Each ISP also downloads all with this data for everyone other ISPs which can be running S-BGP. The repositories periodically transfer new data together to maintain loose synchronization. ISPs process the repository information to make more compact files that includes the AA data plus the public keys and prefix and AS data through the certificates, but none with the certificate management information or CRLs. These resulting extracted files are transferred to your routers executing S-BGP underneath the control in the ISP.
Because certificates, AAs, and CRLs are signed and carry validity interval information, they might require minimal additional security whilst in transit to or from the repository or while stored on the repository. Nonetheless, S-BGP employs the Secure Sockets Layer SSL protocol, with both client and server certificates, to protect having access to the repositories, to be a countermeasure to denial-of-service attacks. The simple, hierarchic structure in the PKI allows repositories to automatically effect access control checks around the uploaded data, as an example, to stop one ISP from accidentally or maliciously overwriting the certificates, CRLs, and AAs from another ISP.
S-BGP distributes RAs with BGP UPDATEs within a newly defined, optional, transitive path attribute. Because routes may change quickly, it is essential that RAs accompany the UPDATEs that happen to be validated along with them. If some other means of distribution is needed for this data, there can be a likelihood which the UPDATEs and also the data is going to be out of synch, building a conundrum for any router; that is certainly, what if the router do once the UPDATE plus the security data differ? RAs utilize a compact encoding scheme to aid ensure that are put within the BGP packet size limits, even if route or address aggregation occurs. S-BGP accommodates aggregation by explicitly including signed attribute data that otherwise could be lost when aggregation occurs. An S-BGP router receiving an UPDATE coming from a peer caches the RAs using the route from the Adj-RIB to the peer, and from the Local Routing Information Base Loc- RIB when the route is selected.
As noted inside the following discussion, the bandwidth necessary to support in-band distribution of route attestations is negligible when compared with subscriber traffic.
Although the RA mechanism was designed to shield AS path data, this may also accommodate other new path attributes; as an example, communities 11 and confederations 12. Specifically, there is really a provision to point what data, in addition on the AS path, is covered with the digital signature that is area of the RA.
Figure 1 illustrates the way the major aspects of S-BGP interact, employing a simplified example. The figure shows two ISPs, each which has a Network Operations Center NOC, a repository, and three routers. A third ISP is represented by 1 S-BGP-enabled router. Each ISP interacts by having an RIR to try a certificate representing the prefixes and AS numbers assigned to your ISP. Each NOC interacts that has a repository to upload data certificates, CRLs, and AAs from that ISP, and also to download exactly the same data acquired of all other ISPs. The repositories connect to one another to change uploaded ISP data, to produce that data open to all other ISPs. Within an ISP, the NOC pushes a copy from the extracted certificate and AA data, produced in the downloads acquired at a repository, to every single router. Routers exchange UPDATE messages, containing RAs, that enable validation of the received UPDATE.
S-BGP uses IPSec 6, 7, 8, specifically the Encapsulating Security Payload ESP protocol, to deliver authentication, data integrity, and antireplay for all those BGP traffic between neighboring routers. The Internet Key Exchange IKE protocol 9, 10 is needed for key management services simply ESP. The S-BGP PKI includes certificates for IKE, outside of those useful for RA processing.
The usage of IPSec is preferable to your current option with the Message Digest Algorithm 5 MD5 TCP checksum option 15, in lots of respects. IPSec uses keyed hash functions in the way which is cryptographically more secure which the MD5 checksum option, and IKE provides automated key management, an element sorely lacking inside option. Protecting BGP traffic for the IP layer, vs. the TCP layer, counters more vulnerabilities, for the reason that TCP implementation is protected at the same time, one example is, including SYN flooding and spoofed RSTs resets, are rejected.
Despite the extensive security provided by S-BGP, architectural vulnerabilities exist that happen to be not eliminated by its use. For example, an S-BGP router may reassert a route that had been withdrawn earlier, even when the route hasn't been readvertised. The router may also suppress UPDATEs, including ones that withdraw routes. These vulnerabilities exist because BGP UPDATEs will not carry sequence numbers or time stamps that can be accustomed to determine their timeliness. However, RAs do carry an expiration time and date, so there is really a limit regarding how long an attestation is usually misused using this method. S-BGP restricts malicious behavior towards the set of actions in which a router or AS is authorized, depending on externally verifiable, authoritative constraints.
In developing the S-BGP architecture, we paid close attention for the performance and operational impact on the proposed countermeasures, and reported our analysis in earlier papers. In preparing this post, we updated our data, utilizing a range of sources; as an example, the Route Views project. Although much data about BGP and associated infrastructure is obtainable, other details are difficult to acquire inside a fashion that is certainly representative of a standard BGP router. This is because each AS inside the Internet embodies a rather different take a look at connectivity, as a results of local policy filters applied by other ASes.
It is important that this transmission, storage, and processing requirements imposed by S-BGP not so great with regards to overwhelm routers. Each these requirements should be analyzed separately.
The transmission of RAs in UPDATEs does significantly increase the size of such messages, by about 800 percent. However, as the volume on this traffic is minuscule in accordance with subscriber traffic, the increase is negligent. The group of files containing certificates, AAs, and CRLs could well be about 75-85 MB. Daily transmission of those files between ISPs and repositories may not represent an important increase in traffic volume for that Internet.
Although the transmission overhead is just not a concern, storage in the RAs in each Adj-RIB along with the Loc-RIB is often a problem. The additional space necessary to hold these RAs is estimated at about 30-35 MB per peer, if S-BGP were fully deployed today. This is often a modest volume of memory for just a typical router that has a few peers, but a tremendous amount of storage for routers at Internet exchanges, certainly where an router could possibly have tens or maybe hundreds of peers.
Thus the management CPU in a very router may require a gigabyte or higher of RAM under these conditions. When a large ISP peers with lots of other ISPs in an exchange, the peering will not be symmetric; which is, the massive ISP accepts not many routes from each on the smaller ISPs, filtering the rest. Thus the number of additional memory important for RAs in Adj-RIBs for each these small ISP peers could be considerably less than for symmetric peer relationships. This requisite memory seems modest by current workstation standards, but the majority deployed routers can't be configured using this much memory.
The computational burden of router processing of RAs in UPDATEs can be a function on the path length in each UPDATE and also the rate when UPDATEs arrive. The arrival rate is usually a function in the number of S-BGP peers the router sees, along with the rate of which each peer sends UPDATEs. Our analysis suggests that this long-term 24-hour UPDATE rate for just a router with 30 peers is around 0.5 UPDATEs per second. On average, each UPDATE would contain about 3.7 RAs. We originally estimated peak minute rate as about ten times the average rate. At this rate, a router could probably perform the requisite signature verification in software about 18 signature verifications per second. Recent evidence suggests one factor of 100-200 may well be a better estimate, in light of exposure to major worm attacks, as well as that rate it could well be hard for software to maintain pace.
Heuristics are around to reduce this burden. Analysis signifies that about half of all UPDATEs are sent as a consequence of route flaps; that may be, transient communication failures that, when remedied, result within a return to your former route. Thus if the router maintained a depth-two cache per Adj-RIB-In, it may avoid signature validation about 50 percent on the time. However, this might double the storage requirements of these RIBs, and that may exacerbate the storage problem cited previously.
Our previous analysis also assumed that receipt of each and every UPDATE would bring about transmission connected with an UPDATE with one new signature. This was an oversimplification; a router generates and transmits an UPDATE only should the newly received route is better than the latest best route to the prefix, or should the best route to the prefix is withdrawn because of the UPDATE. When a router has numerous peers, most in the UPDATEs it receives might not exactly yield a greater route, thereby will not trigger transmission of a different UPDATE.
On additional hand, each time a router does select a different route, an UPDATE could be constructed and sent to each and every neighbor, requiring one signature per neighbor. This is because an RA specifies the AS number with the neighbor which it is directed. It is possible to construct an RA that identifies another hop to be a set of AS numbers, corresponding to every one of the neighbors that an UPDATE is authorized to become sent. The downside of the strategy is it makes the RAs larger, contributing towards the storage problem noted previously.
The observation made previously suggests a heuristic for UPDATE processing to mitigate signature validation costs. A router can defer validation on the RAs in different UPDATE who's receives, in the event the UPDATE may not represent a different best route. This optimization might be especially of great help for routers that get the greatest variety of UPDATEs; that is certainly, routers with lots of neighbors. One might worry that it strategy allows an opponent to force processing, by sending what will be considered excellent routes, but an S-BGP router could detect such fraudulent UPDATEs and may choose to drop its connection to some peer that behaved that way, as a way to counter a very attack.
Initialization/reboot of any BGP router also results within a surge in UPDATE processing, along with the deferred processing heuristic is relevant here too, while reboots are relatively infrequent. Saving RIBs in nonvolatile storage addresses this matter. Most deployed routers will not have sufficient nonvolatile storage to take this strategy, but a majority of do have hard drives that could easily accommodate the RIBs.
It is reasonable to believe that next-generation routers could possibly be configured with plenty of RAM for that RIBs, but this analysis implies that full deployment isn't feasible with all the currently deployed router base. To add RAM, and even to add nonvolatile storage, router vendors will need to upgrade the processor boards where net management processing comes about. That implies that addition of any crypto accelerator chip could be prudent as portion of the board redesign process, for instance, to face surge conditions noted previously.
Adoption of S-BGP requires cooperation among several groups. ISPs and subscribers running BGP must cooperate to come up with and distribute AAs. Major ISPs must implement the S-BGP security mechanisms so that you can offer significant benefit towards the Internet community. The IANA and RIRs must enhance operational procedures to back up generation of prefix and AS number allocation certificates. Router vendors ought to offer additional storage in next-generation products, or offer ancillary devices to use with existing router products, and revise BGP software to guide S-BGP.
There offers some good news; S-BGP could be deployed incrementally. Only neighboring ASes receive full make use of such deployment. Although we opted for transitive path attribute syntax to cart RAs, therefore it might be simple for non-neighbor ASes to change RAs, it appears likely that intervening ASes wouldn't normally have sufficient storage with the RAs of their RIBs.
Also, the controls required by routers to take benefit of noncontiguous deployment of S-BGP can be complex, hence our suggestion that only contiguous deployment of S-BGP be attempted.
External routes received from S-BGP peers need to become redistributed in the AS, both to interior routers and other border routers, to be able to maintain a consistent and stable view on the exterior routes over the AS. Thus an AS must change to using S-BGP for everyone its border routers at a time, to protect yourself from route loops inside the AS.
As of early 2003, an implementation of S-BGP continues to be developed and demonstrated on small amounts of workstations representing small quantities of ASes. We also developed software for a straightforward repository, as well as NOC tools that support secure upload and download of certificates, CRLs, and AAs from repositories, as well as certificate management for NOC personnel and routers. This suite of software, plus CA software from another Defense Advanced Research Projects Agency DARPA program, provide all from the elements necessary to represent a complete S-BGP system. All of this software program is available in open source form.
S-BGP represents a thorough approach to addressing a variety of security concerns related to BGP. It detects and rejects unauthorized UPDATE messages, irrespective from the means by that they can arise; by way of example, misconfiguration, active wiretapping, compromise of routers or management systems, etc. S-BGP is just not perfect; it features a few residual vulnerabilities, however these pale in comparison on the security features S-BGP provides, and removal of such vulnerabilities would require more fundamental changes to BGP semantics.
The S-BGP design is based over a top-down security analysis, starting using the semantics of BGP and factoring inside the wide range of attacks who have or may be launched contrary to the existing infrastructure.
Many individuals contributed for the design and growth and development of S-BGP, including Christine Jones, Charlie Lynn, Joanne Mikkelson, and Karen Seo.
2 S. Kent, C. Lynn, and K. Seo, Secure Border Gateway Protocol SBGP, IEEE Journal on Selected Areas in Communications, Vol. 18, No. 4, April 2000.
3 C. Villamizar, R. Chandra, and R. Govindan, BGP Route Flap Damping, RFC 2439, November 1998.
4 Smith, and Garcia-Luna-Aceves, Securing the Border Gateway Routing Protocol, Proceedings of Global Internet 96, November 1996.
5 S. Murphy, panel presentation on Security Architecture for that Internet Infrastructure, Symposium on Network and Distributed System Security, April 1995.
6 S. Kent and R. Atkinson, Security Architecture with the Internet Protocol, RFC 2401, November 1998.
7 R. Glenn and S. Kent, The NULL Encryption Algorithm and Its Use with IPsec, RFC 2410, November 1998.
8 S. Kent and R. Atkinson, IP Encapsulating Security Payload ESP, RFC 2406, November 1998.
9 D. Maughan, M. Schertler, M. Schneider, and J. Turner, Internet Security Association and Key Management Protocol ISAKMP, RFC 2408, November 1998.
10 D. Harkins and D. Carrel, The Internet Key Exchange IKE, RFC 2409, November 1998.
11 R. Chandra, P. Traina, and T. Li, BGP Communities Attribute, RFC 1997, August 1996.
12 P. Traina, Autonomous System Confederations for BGP, RFC 1965, June 1996.
13 T. Bates, R. Chandra, D. Katz, and Y. Rekhter, Multiprotocol Extensions for BGP-4, RFC 2283, February 1998.
14 K. Seo, C. Lynn, and S. Kent, Public-Key Infrastructure with the Secure Border Gateway Protocol S-BGP, DARPA Information Survivability Conference and Exposition, June 2001.
15 A. Heffernan, Protection of BGP Sessions using the TCP MD5 Signature Option, RFC 2385, August 1998.
STEPHEN KENT received the, , and degrees in computer science from MIT, and also a in mathematics from Loyola University of New Orleans. He has worked at BBN more than 25 years, where he serves today as Chief Scientist-Information Security. He served within the IAB for spanning a decade, and chaired the Privacy Security Research Group in the IRTF and also the PEM WG within the IETF, where he currently co-chairs the PKIX WG. He has served on several committees for your National Research Council, and chairs a committee on authentication and privacy with the NRC. His current work targets PKI issues, BGP security, and also high speed IP encryption. He is often a Fellow from the ACM, along with a member in the Internet Society and Sigma Xi. His e-mail address is: